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Rastrelliger brachysoma (Bleeker, 1851), the short mackerel, is a dietary staple and of significant economic demand in Southeast Asia and Thailand. However, the demand for short mackerel has precipitated an overfishing crisis, leading to a depletion of fish stocks. Overfishing, coupled with parasitism, may result in a decline in the population of R. brachysoma. Digenetic trematode infection is prevalent in marine fish and has a considerable impact on the overall health of the fish. Here, to identify digenetic trematodes infecting R. brachysoma, we aim to determine the identity, prevalence, and intensity of digenean infections in R. brachysoma from the Gulf of Thailand. A total of 194 short mackerel were obtained from Chon Buri Province, where digeneans were isolated and identified. The molecular identity of the digeneans was confirmed using the nuclear 28S rRNA gene. Of the 194 short mackerel, 100% were found to be infected with digeneans, comprising of Lecithocladium, Prodistomum, Opechona, and Aphanurus. Lecithocladium was the most prevalent (98%) and had the highest intensity of infection (37 mean intensity), followed by Prodistomum (75% prevalence and 17 mean intensity). Our study thus presents the first evidence of digeneans infecting the economically important short mackerel from the Gulf of Thailand. The high infection rate of digenetic trematodes may have implications on the health of R. brachysoma, further driving their population decline. These data underscore the importance of safeguarding fisheries resources in the Gulf of Thailand, and downstream conservation efforts are crucial for evidence-based management decisions to safeguard the long-term sustainability of fish resources., (© 2024. The Author(s).)

Haliotrema Pteroisi: Paperna, 1972 (Monogenoidea: Dactylogyridae) was found parasitizing the gill lamellae of devil firefish, Pterois miles (Bennet) (Perciformes: Scorpaenidae), in the Red Sea off Safaga (26°44'N, 33°56'E), Egypt. The parasite species was described based on morphological features of available specimens and transferred to PlatycephalotremaKritsky and Nitta, 2019 (Dactylogyridae) as Platycephalotrema pteroisi (Paperna, 1972) n. comb. The occurrence of Pl. pteroisi off Safaga, Egypt, represented a range extension for the helminth of about 160 km to the southwest of the southern end of the Gulf of Aqaba. The transfer of the species to Platycephalotrema based on an evaluation of morphological features was supported by an analysis of molecular sequences of the 28S rDNA gene of Pl. pteroisi and 49 other dactylogyrid species. Maximum-likelihood, Bayesian inference, and maximum parsimony analyses of this dactylogyrid sequence data revealed H. pteroisi to nest with significant support within the clade of Platycephalotrema spp. During the literature review of dactylogyrid species infecting scorpionfishes, it was determined that Ancyrocephalus sp. of Dyer et al. from luna lion fish Pterois lunulata Temminck and Schlegel collected off Okinawa-jima, Japan represented an undescribed species of Platycephalotrema., (© American Society of Parasitologists 2024.)

Large yellow croaker (L. crocea) is a productive species in marine aquaculture with great economic value in China. However, the sustainable development of large yellow croaker is hampered by various diseases including cryptocaryonosis caused by Cryptocaryon irritans. The genetic regulation processes for cryptocaryonosis in large yellow croaker are still unclear. In this present study, we analyzed differential alternative splicing events between a C. irritans resistance strain (RS) and a commercial strain (CS). We identified 678 differential alternative splicing (DAS) events from 453 genes in RS and 719 DAS events from 500 genes in CS. A set of genes that are specifically alternatively spliced in RS was identified including mfap5, emp1, and trim33. Further pathway analysis revealed that the specifically alternative spliced genes in RS were involved in innate immune responses through the PRR pathway and the Toll and Imd pathway, suggesting their important roles in the genetic regulation processes for cryptocaryonosis in large yellow croaker. This study would be helpful for the studies of the pathogenesis of cryptocaryonosis and dissection of C. irritans resistance for L. crocea., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Sea lice infestations can pose significant challenges in the aquaculture sector, affecting fish health and overall production. In the search for effective and eco-friendly solutions, hydrogen peroxide bath treatment has been considered as one of the promising methods. This is the first study to evaluate the field efficacy of hydrogen peroxide bath technique against sea lice infestation on cage-cultured snubnose pompano (Trachinotus blochii). Sea lice was identified as Lepeophtheirus spinifer using morphological description. Naturally-infested snubnose pompano stocked in 2 ×3×2 m 3 net cages at 15 fish/cage at the Igang Marine Station of SEAFDEC/AQD, in Guimaras, Philippines were treated in triplicates with two hydrogen peroxide concentrations (1500 and 2000 ppm) in comparison to a control (seawater only) for 20 minutes at 32.8 ± 0.7 ppt and 28.9 ± 0.3 °C and were monitored at 3rd and 7th day post-treatment. The total mean intensity of sea lice, mean intensity per life stages (copepodid, chalimus I, chalimus II, pre-adult I, pre-adult II, adult male and adult female), and the 12-h viability of scraped male and adult female L. spinifer from the treatment groups were evaluated. The total mean intensity of sea lice in the treated groups at 3 day post-treatment was significantly lower than the control group (p<0.001). A possible re-infection of sea lice was observed 7 days post-treatment as explained by the slight increase in the mean intensity in the treated groups. However, no mortalities of pompano were recorded throughout the experiment. In addition, adult female lice were absent in the treated group while adult male lice were only detected in the 1500 ppm treatment group at a very low mean intensity. The viability test also showed that all sea lice were not able to recover after 12 h whereas a 100 % recovery rate was noted in the control group. Results suggest that the 1500 and 2000 ppm hydrogen peroxide concentrations are effective in reducing sea lice infestation on cage-cultured snubnose pompano. However, a long-term effect of hydrogen peroxide treatment on sea lice needs further investigation., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Host phylogeny and ecological convergence are two factors thought to influence the structure of parasite communities. The aims of this study were to determine the diversity of metazoan parasites of 10 sympatric fish species of the family Carangidae from the southeastern Gulf of California, and to analyze their similarity at infracommunity and component community levels, in order to determine if the host species, particularly those congeneric with similar ecological characteristics, exhibit similar assemblages of parasites. In total, 874 fish specimens were examined and 40 parasite species were identified. The component community was composed by 21 parasite species in Caranx caninus, 20 in C. caballus, 11 in C. vinctus, five in Chloroscombrus orqueta, four in Carangoides otrynter, seven in Hemicaranx leucurus, eight in Selene brevoortii, 14 in S. peruviana, and 11 in Trachinotus rhodopus. The metazoan parasite communities of C. vinctus, Ch. orqueta, H. leucurus, and S. brevoortii are reported here for the first time. The parasite communities of the remaining six carangid species have been reported from regions other than the Gulf of California. All fish species differed significantly regarding the diversity of their parasite infracommunities. This possibly is due to different patterns of habitat use among fish species, and because of the differential host specificity among parasite taxa. Nonetheless, when the analysis was restricted to common parasite species, some fish showed similar parasite infracommunities, particularly congeners of the genus Selene as well as C. caballus and C. vinctus. The component communities of species of Selene were highly similar (>65%), but the three species of Caranx were not. This result supports the hypothesis that congeneric fish species with similar ecological filters harbor similar parasite communities. However, the difference observed between C. caninus and C. caballus suggests that these species, despite being evolutionary and ecologically related, have different physiological or immunological characteristics (compatibility filters) that may result in different parasite communities., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Taeniacanthus aulacocephali Izawa, 2021 (Copepoda: Cyclopoida: Taeniacanthidae) was redescribed from the branchial cavity and gill filaments of Uranoscopus japonicus Houttuyn (Perciformes: Uranoscopidae) collected from the Pacific coast of the Kochi and Wakayama prefectures, Japan. This is the second record of the copepod, and the finding from U. japonicus represents the new host record. The species is characterized by several distinguishing features: 1) a decrease in the width of the habitus between the second and fourth pedigerous segments; 2) the ratio of prosome/body length; 3) the presence of eight setae on the exopodal terminal segment of leg 2; 4) an un-bifurcated maxilliped claw surrounded by 14-28 transverse ridges; and 5) the presence of an inner coxal seta on legs 2 and 3. The newly collected specimens were subjected to a modified non-destructive DNA extraction method and morphological description based on the same copepod individual, while preserving a morphologically describable specimen. Sequences of 18S rDNA, 28S rDNA and the mitochondrial cytochrome c oxidase subunit 1 mitochondrial gene (cox1) were obtained., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

During March 2023, 7 green sunfish (Lepomis cyanellus) and 2 bluegill (Lepomis macrochirus) were collected from the Black River (White River drainage) in Lawrence County, Arkansas. In addition, during March 2023 and again in May-June 2023, 13 L. cyanellus and 6 L. macrochirus were taken from Butcherknife and Big Fork creeks (Ouachita River drainage), Polk County, Arkansas, 9 L. cyanellus were collected from the Caddo River, Montgomery County, Arkansas, and 5 green sunfish were taken from Clear Creek at Savoy, Washington County, Arkansas. All fish had their gill, gallbladder, fins, integument, musculature, and other major organs examined for myxozoans. The gill of 1 of 34 (3%) L. cyanellus was infected with a new myxozoan, Myxobolus fergusoni n. sp. Qualitative and quantitative morphological data were obtained from fresh myxospores, and molecular data consisted of a 1,933-base-pair sequence of the partial small subunit (SSU) ribosomal RNA (rRNA) gene. Phylogenetic analysis grouped M. fergusoni n. sp. with other centrarchid-infecting myxobolids from North America and placed this cluster in a larger clade comprising myxozoans that infect North American and European esocids, a North American aphredoderid, European percids, and a gasterosteid from Japan. Myxobolus fergusoni n. sp. infects the gill arches of L. cyanellus, similar to Myxobolus cartilaginis (Hoffman, Putz, and Dunbar, 1965), which was described from head cartilage, gill arches, and large fin rays of L. cyanellus. Another is Myxobolus mesentericusKudo, 1920, which was described from the viscera of green sunfish. A large polysporic plasmodium filled with myxospores was present in a basifilamental location associated with multiple gill filaments at their junction with the gill arch. The intact plasmodium replaced connective tissue within the arch but elicited only mild proliferation of overlying epithelium and a minimal host inflammatory response. This is the third time a myxozoan has been described from L. cyanellus, as well as being the first time it has been described from an Arkansas specimen., (© American Society of Parasitologists 2024.)

Myxospores discovered floating free in the bile of marine fishes from the south-central coast of Vietnam were identified using morphological and molecular methods, leading to the description of 2 new species. Ceratomyxa chauvanminhi n. sp. was detected in 16% (8/50) of cultured barramundi Lates calcarifer (Bloch) specimens, and Ceratomyxa sekoi n. sp. was found in 20% (5/25) of wild largehead hairtail Trichiurus lepturus Linnaeus specimens. The spores of C. chauvanminhi n. sp. are very shallowly ovoid, slightly crescent shaped, and 11.5 ± 0.5 (10.7-12.4) μm thick, 5.8 ± 0.2 (5.4-6.1) μm long, and 5.5 ± 0.2 (5.2-5.7) μm wide. Their posterior angles are slightly concave at 158.7° ± 4.2° (151.3°-164.8°), and they possess 2 equal spherical polar capsules 2.5 ± 0.2 (2.1-2.9) μm in diameter. The spores of C. sekoi n. sp. are 5.6 ± 0.2 (5.0-6.1) μm long, 75.5 ± 4.8 (68.9-90.0) μm thick, and 5.5 ± 0.1 (5.4-5.6) μm wide, with 2 equal, slightly anterior spherical polar capsules 2.1 ± 0.2 (1.7-2.4) μm in diameter. Although C. sekoi n. sp. spores resemble those of species of MyxodavisiaZhao, Zhou, Kent, and Whipps, 2008, characterized by long tapering valves, genetic analyses distinctly place this new species within the Ceratomyxa Thélohan, 1892 lineage. This study contributes to the understanding myxosporean diversity in Vietnamese waters and highlights the difficulty associated with distinguishing between the genera Ceratomyxa and Myxodavisia., (© American Society of Parasitologists 2024.)

A total of 366 individuals of Lutjanus argentiventris (Peters, 1869) were collected over a 5-yr period (October 2018 to June 2022) from Acapulco Bay, Mexico. Parasite communities in Lutjanus argentiventris were quantified and analyzed to determine the main factors that generate changes in species richness and/or species composition over time. The digeneans and copepods were the best-represented parasite groups. The parasite communities were characterized by a high numerical dominance of ectoparasites, mainly isopod larvae. Species richness at the component community level (9-23 species) was similar to the reported richness in other Lutjanus spp. The parasite communities of Lutjanus argentiventris exhibited high variability in species composition, suggesting that each parasite species may respond differently to environmental changes. However, the species richness and diversity were fairly stable over time; therefore, a clear pattern of interannual variation was not observed. Variations in the community structure probably were due to factors such as host traits (e.g., feeding behavior and body size), and possible interannual differences in environmental factors amplified by the occurrence of the anomalous event of La Niña., (© American Society of Parasitologists 2024.)

Introduction: Due to the high-density farming of Larimichthys crocea over the years, diseases caused by pathogens such as bacteria, viruses, and parasites frequently occur in Ningbo, posing a huge threat and challenge to the sustainable and healthy development of the L. crocea's bay farming industry. In order to understand the diseases occurrence in L. crocea farming in Ningbo area, an epidemiological investigation of L. crocea diseases was carried out through regular sampling in 2023., Methods: From April to October 2023, routine sampling of L. crocea was conducted monthly in various farming areas in Ningbo. Each time, live or dying L. crocea with obvious clinical symptoms were sampled, with a total number of 55 L. crocea collected. The samples were preserved in ice bags and transported to the laboratory for pathogen detection(including bacterial isolation and identification,virus identification, and parasites detection)., Results: A total of fifty-five fish dying L. crocea with obvious clinical symptoms were collected in this study, of which 78.18% (43/55) were detected with symptoms caused by pathogenic infection, while 21.82% (12/55) did not have identified pathogens, which were presumed to be breeding abrasions, nutritional metabolic disorders, unconventional pathogens infection or other reasons. A total of twenty-five pathogenic bacteria strains were isolated, which mainly were Pseudomonas plecoglossicida and Vibrio harveyi , accounting for 52% (13/25) and 32% (8/25) of the pathogenic bacteria strains, respectively. Among them, both V. harveyi and Streptococcus . iniae co-infected one fish. Additionally, three other bacterial strains including Nocardia seriolae , Staphylococcus Saprophyticus , and Photobacterium damselae subsp.damselae were isolated. Microscopic examination mainly observed two parasites, Cryptocaryon irritans and Neobenedenia girellae . In virus detection, the red sea bream iridovirus (RSIV) was mainly detected in L. crocea . Statistical analysis showed that among the fish with detected pathogens, 55.81% (24/43) had bacterial infections, 37.21% (16/43) had parasitic infections, and 37.21% (16/43) had RSIV infections. Among them, five fish had mixed infections of bacteria and parasites, three had mixed infections of bacteria and viruses, three had mixed infections of parasites and viruses, and one L. crocea had mixed infections of viruses, bacteria, and parasites., Discussion: These findings indicate that these three major types of diseases are very common in the L. crocea farming area in Ningbo, implying the complexity of mixed infections of multiple diseases., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Xu, Ge, Feng, Wei, Tan, Liang and Tong.)

Purple-spotted bigeyes Priacanthus tayenus Richardson (Priacanthidae) and bartail flathead Platycephalus indicus (Linnaeus) (Platycephalidae) were collected from the Arabian Gulf and examined for species of Monogenoidea (Polyonchoinea) from February to December 2020. Diplectanum robustitubum Wu & Li, 2003 and an undescribed species of Platycephalotrema Kritsky & Nitta, 2019 were recovered from the gill lamellae of these hosts, respectively. Diplectanum robustitubum from Iraq was redescribed and transferred to Oliveriplectanum Domingues & Boeger, 2008 (Diplectanidae) as Oliveriplectanum robustitubum (Wu & Li, 2003) n. comb. Platycephalotrema parile n. sp. (Dactylogyridae) from Iraq and Kuwait was described and differentiated from the similar species, Haliotrema indicum Tripathi, 1959, Platycephalotrema ogawai Kritsky & Nitta, 2019, and Platycephalotrema platycephali (Yin & Sproston, 1948) Kritsky & Nitta, 2019, based primarily on the comparative morphologies of the vaginal sclerites. Haliotrema indicum was transferred to Platycephalotrema as Platycephalotrema indicum (Tripathi, 1959) n. comb. and Haliotrema swatowense Yao, Wang, Xia, & Chen, 1998 was considered a junior subjective synonym of P. indicum. The finding of O. robustitubum in the Arabian Gulf represents a new geographic record for the species., Background: The present paper represents the third installment concerning the monogenoids collected during surveys to explore their diversity on the marine and freshwater fishes of Iraq. Previous installments on the monogenoids emanating from the surveys included the dactylogyrid and gyrodactylid species parasitizing mugilid fishes., Purpose: The purpose of this paper is to further document the diversity of monogenoids infecting the fishes of Iraq., Methods: Marine fishes were necropsied for parasites, and standard procedures for collecting, mounting, drawing, and measuring of monogenoids were employed., Results: Oliveriplectanum robustitubum n. comb. (Diplectanidae) and Platycephalotrema parile n. sp. (Dactylogyridae) were collected. The occurrence of O. robustitubum in the Arabian Gulf represented a new locality record for the species., Conclusion: The recorded presence of O. robustitubum and P. parile n. sp. suggests that the diversity of monogenoids in Iraq is under estimated in the literature., (© 2024. The Author(s).)

The genus Ancyrocephalus sensu lato is a large assemblage of species of dactylogyrid monopisthocotyleans without clear taxonomic boundaries. Despite an urgent need for revision, only three representatives of this taxon have been molecularly characterised so far. We found specimens of Ancyrocephalus curtus , a previously non-genotyped species, in gills of Perccottus glenii caught in the River Syumnyur, Amur Basin, Russia. The aim of this study was to assess the phylogenetic position of this parasite using partial sequences of 28S rRNA gene. In the phylogenetic tree, A. curtus appeared as a sister taxon to the dactylogyrine genus Gobioecetes. The new molecular evidence supports the hypothesis about the non-monophyletic status of Ancyrocephalus sensu lato.

Prevalence values for 3 digenean species of the family Opecoelidae were calculated during a half-year period from 20 individuals per month of the fish species Clinocottus analis, collected from an intertidal environment of Baja California, Mexico. Trematode species recovered were Opecoelus adsphaericus, Opecoelus cameroni, and Opecoelus pacificus. Of these, only O. adsphaericus was present throughout the study, whereas O. pacificus and O. cameroni were recorded for 1 or 2 mo, respectively, exhibiting relatively low prevalence values. The decrease in prevalence of O. adsphaericus coincides with the appearance of O. pacificus and O. cameroni; these last 2 species were found only in the largest hosts, and their presence represents new records for Mexican marine fauna., (© American Society of Parasitologists 2024.)

Acanthocephalans are a group of obligate endoparasites that alternate between vertebrates and invertebrates to complete their life cycles. Occasionally, the same individual host acts as a definitive or paratenic host for different acanthocephalan species. In this study, acanthocephalans were sampled in marine fish in three localities of the Yucatán Peninsula; adults and cystacanths were recovered from the intestine and body cavity, respectively, of Haemulon plumierii from off the coast of Sisal, Yucatán. Ribosomal DNA sequences (small and large subunits) were used to test the phylogenetic position of the species of the genus Dollfusentis , whereas the mtDNA gene cox 1 was used for assessing species delimitation. The cox 1 analysis revealed an independent genetic lineage, which is recognized herein as a new species, Dollfusentis mayae n. sp. The new species is morphologically distinguished from the other six congeners by having a cylindrical proboscis armed with 22-25 longitudinal rows bearing 12 hooks each. The cystacanths were morphologically identified as Gorgorhynchus medius by having a cylindrical trunk covered with tiny irregular spines on the anterior region, and a cylindrical proboscis armed with 17-18 longitudinal rows of 21 hooks each; small and large subunit phylogenetic analyses yielded G. medius within the family Isthomosacanthidae, suggesting that Gorgorhynchus should be transferred to this family from Rhadinorhynchidae where it is currently allocated.

Purpose: The aim of this article is to describe a new and unusual species of Neoechinoprhynchus Stiles & Hassall, 1905 from the Arabian Gulf coast off Iraq., Methods: Routine methods for examination of fish hosts and recovery of acanthocephalean parasites were followed. Parasites were cleaned, relaxed overnight in refrigerated water then fixed in cold 70% ethanol. Standard procedure for staining, dehydration, clearing in xylene and mounting in Canada balsam was followed., Results: Neoechinorhynchus miniovalis n. sp. is described from five whole-mounted specimens collected from the mudskipper Boleophthalmus dussumieri Valenciennes (Oxudericidae) captured in Shatt Al-Basrah Canal, Iraq in 2008. It is distinguished from other species of Neoechinorhynchus Stiles and Hassall, 1905 by a combination of the following diagnostic characters: very small ellipsoid trunk with tapering posterior end and correspondingly small size organs; body wall with similar thickness dorso-ventrally; proboscis wider than long with long anterior hooks having prominent roots; hooks in second and third circles much smaller and rootless; receptacle 5-6 times as long as proboscis with a triangular cephalic ganglion at its base; no para-receptacle structure; lemnisci relatively long and equal, not reaching anterior testis; all male reproductive structures contiguous in posterior two-thirds of trunk; testes equatorial and much wider than long; anterior testis smaller than posterior testis; large syncytial cement gland with six giant nuclei; cement reservoir adjacent to anterior end of sperm vesicle adjacent to Saefftigen's pouch. No sexual dimorphism except that the trunk is more rounded in females than in males. The female reproductive system is about one-third as long as the trunk with the selective apparatus in two positions and uterine bell angulating ventrad. Female lemnisci are longer than in males. Comparisons with worldwide and North American-related species that have partially similar features are made., Conclusions: The finding of Neoechinorhynchus miniovalis n. sp. with unusual small body and wide ellipsoid shape acanthocephalan is considered the first acanthocephalan species belonging to Neoechinorhynchus reported from Palearctic region compared to similar seven species reported only from Neotropical (three species), Nearctic regions (two species), far east (one species) and oriental (one species)., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Purpose: The aim of this study was the comparative analysis of the parasite communities of new populations of invasive pumpkinseed (Lepomis gibbosus) in western Ukraine with pumpkinseed from Czechia, where populations have rapidly expanded over the last two decades., Methods: Sampling took place at three localities in the western part of Ukraine (i.e. Dobrotvir Reservoir (Vistula basin), Burshtyn Reservoir (Dniester basin), Mynai Pond (Danube basin)) and four in Czechia (i.e. Oxbow D2, Heršpický Pond (Danube basin), and Kolín oxbow and Římov Reservoir (Elbe basin)., Results: In total, 11 parasite taxa were recorded in Ukraine and 17 in Czechia. Four species were co-introduced from North America with their host, i.e. the myxosporean Myxobolus dechtiari, the monogeneans Onchocleidus dispar and Onchocleidus similis, and metacercariae of a trematode Posthodiplostomum centrarchi. High dominance indices were related to a high abundance of co-introduced parasites, i.e. O. similis in Mynai pond and P. centrarchi in Dobrotvir Reservoir. Overall abundance of acquired parasites was generally low., Conclusion: This study shows that parasite communities in recently established pumpkinseed populations in the western part of Ukraine and Czechia are less diverse than those established in Europe for decades. The generally low parasite load in these new populations may play an important role in their ability to successfully establish and create strong populations by providing a competitive advantage over local species., (© 2024. The Author(s).)

Purpose: The present paper describes two new genera and species of the parasitic copepod family Chondracanthidae Milne Edwards, 1840 based on specimens collected from two species of deep-sea fishes at a depth of 212 m off Suruga Bay, Japan. Avatar nishidai gen. et sp. nov. is described from the host fish Chaunax abei Le Danois, 1978 (Chaunacidae). Kokeshioides surugaensis gen. et sp. nov. is described from the host fish Setarches longimanus (Alcock, 1894) (Setarchidae)., Methods: Fresh specimens of chondracanthids were collected from the buccal cavity of two species of deep-sea fishes (fish hosts were frozen), Chaunax abei Le Danois, 1978 (Lophiiformes: Chaunacidae) and Setarches longimanus (Alcock, 1894) (Perciformes: Setarchidae), caught at a depth of 212 m in Suruga Bay, Japan (34° 37'48.87″ N, 138° 43'2.958″ E). Both the species are described and illustrated based on ovigerous females., Results: The genus Avatar gen. nov. can readily be distinguished from all other chondracanthid genera by the following combination of features: cephalothorax slightly wider than long with anterior pair of large and posterior pair of small lateral lobes, and two pairs of ventro-lateral processes; the very posteriormost part of the first pedigerous somite contributes to the neck; cylindrical trunk with two pairs of blunt proximal fusiform processes; antennule with small knob terminally; antenna bearing distal endopodal segment; labrum protruding ventrally; two pairs of biramous legs each with 2-segmented rami. Kokeshioides gen. nov. has the following combinations of features that distinguish it from other chondracanthid genera: body flattened, without lateral processes; cephalothorax much wider than long, with paired anterolateral and posterolateral lobes, folded ventrally; the very posteriormost part of the first pedigerous somite contributes to the neck; mandible elongate; legs unique, heavily sclerotized, represented by two pairs of acutely pointed processes., Conclusion: With the addition of two new genera presently reported, the family Chondracanthidae currently includes 52 valid genera. Among the described genera Avatar gen. nov. seems to be very primitive, while Kokeshioides gen. nov. is highly advanced. The deduced evolutionary history of chondracanthid genera is also discussed., (© 2024. The Author(s).)

The Almaco jack (Seriola rivoliana) is a marine fish maintained in mariculture systems and frequently infested by monogenean parasites like Neobenedenia sp. Severe infestations can lead to high mortalities and economic losses for farmers. This study evaluated the effects of temperature on the immune response on Almaco jack infested with Neobenedenia sp. We exposed infested fishes at temperatures of 20 °C, 24 °C, and 30 °C for 20 days and took samples of different tissues at the beginning of the experiment, and after 3 and 20 days. The tissues considered were the skin, thymus, cephalic kidney, and spleen to evaluate the relative gene expression of different genes: Hsp70, IgM, IL-1β, IL-10, and MyD88. Our results showed an increase in IL-1β gene expression in the skin after 20 days of infestation but no significant effect of temperature on gene expression, despite increases in infestation rates with temperature. Therefore, relative genetic expression was controlled by the number of parasites and the days post-infestation. These results show that the parasite infestation induced a local response in the skin, but that temperature has an indirect effect on the immune system of Almaco jack., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Small pelagic fishes represent one of the most important food resources off the Northwest coast of Africa. Despite their economic significance, little is known about the infections with flesh invading myxosporean parasites of genus Kudoa (Cnidaria, Myxozoa). Heavy infections in the flesh may be associated with post-mortem myoliquefaction, commonly known as 'soft flesh'. This condition may reduce the quality and marketability of the fish fillet, resulting in both economic losses to the fishing industry and loss of consumer confidence. In this study, we investigated Kudoa-induced 'soft flesh' occurrence in European anchovy Engraulis encrasicolus, European pilchard Sardina pilchardus, and Atlantic chub mackerel Scomber colias caught in 2019 off the Moroccan Atlantic coast. Five hundred specimens of each fish species were examined for 'soft flesh' by texture testing and visual inspection 48 h post-catch. 'Soft flesh' occurred in 0.2 % of the European anchovies, 1.4 % of the European pilchard, and in 4.4 % of the Atlantic chub mackerel. Microscopic examination of muscle samples revealed that 'soft flesh'-affected fish were infected with myxospores of K. thyrsites-like morphotype. Analysis of the kudoid SSU rDNA sequence obtained from European pilchard and the Atlantic chub mackerel identified these as K. thyrsites (100 % identity), whereas analysis of the sequence from European anchovy identified the presence of K. encrasicoli (100 % identity). Even if there are no known human health consequences associated with the ingestion of these Kudoa species, the unsightly appearance of some infected fillets is a food quality issue, that can eventually lead to reduced marketability and value., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Cryptocaryons irritans is a ciliate parasite responsible for cryptocaryoniasis, leading to considerable economic losses in aquaculture. It is typically managed using a copper-zinc alloy (CZA), effectively diminishing C. irritans infection rates while ensuring the safety of aquatic organisms. Nevertheless, the precise mechanism underlying cuproptosis induced C. irritans mortality following exposure to CZA remains enigmatic. Therefore, this study delves into assessing the efficacy of CZA, investigate cuproptosis as a potential mechanism of CZA action against C. irritans, and determine the alterations in antioxidant enzymes, peroxidation, and lipid metabolism. The mRNA expression of dihydrolipoamide S-acetyltransferase was upregulated after 40 and 70 min, while aconitase 1 was implicated in cuproptosis following 70 min of CZA exposure. Furthermore, the relative mRNA levels of glutathione reductase experienced a significant increase after 40 and 70 min of CZA exposure. In contrast, the relative mRNA levels of glutathione S-transferase and phospholipid-hydroperoxide glutathione peroxidase were significantly decreased after 70 min, suggesting a disruption in antioxidant defense and an imbalance in copper ions. Lipidomics results also unveiled an elevation in glycerophospholipids metabolism and the involvement of the lipoic acid pathway, predominantly contributing to cuproptosis. In summary, exposure to CZA induces cuproptosis in C. irritans, impacts glutathione-related enzymes, and alters glycerophospholipids, consequently triggering lipid oxidation., (Copyright © 2023 Elsevier Inc. All rights reserved.)

The purple-spotted bigeye, Priacanthus tayenus, is a marine benthic fish native to the Indian and Pacific Oceans, including the Arabian Gulf in Saudi Arabia. This study identified a myxozoan parasite infecting wild P. tayenus from the Saudi Arabian Gulf. These parasites produced spherical to ovoid-shaped, white plasmodia enclosed within pseudocysts in the fish musculature. The annual infection rate was 5.1%, with the highest prevalence in summer (7.6%), followed by spring (6%), and autumn (2.5%), while no infections were observed in winter. The number of plasmodia per fish ranged from 100 to 150 (135.1 ± 16.2). Their dimensions were 4-4.7 mm (4.3 ± 0.3 mm) in length and 4.5-7 mm (6 ± 1.1 mm) in width. Milky-colored exudates within the plasmodia contained mature spores measuring 8-9 μm (8.6 ± 0.4 μm) x 6-7.5 μm (6.9 ± 0.5 μm). The polar capsules of the spores exhibited dimensions of 2-5 μm (3.5 ± 0.5 μm) x 2.5-4.5 μm (3 ± 0.45 μm). Both morphological and genetic analyses confirmed these plasmodia as a novel Kudoa species. Histopathological examination revealed atrophy in the surrounding muscles without an inflammatory response. This study documents the first occurrence of a novel Kudoa sp. in P. tayenus at the Jubail landing site in Saudi Arabia, emphasizing the need for further surveillance and investigations to elucidate its pathogenesis and implications for wild fish stocks., Competing Interests: All authors declare that they have no conflict of interest., (Copyright: © 2024 Ibrahim et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Monogeneans are a diverse group of flatworms, being ectoparasites of marine and freshwater fish, with great morphological and ecological variety. Analyzes of monogenetics in fish with great habitat diversity such as snappers are scarce in the literature, which already emphasizes the need for an update in this regard. The presente study found, morphologically characterized and mapped the geographic distribution and in known hosts the species Microcotyloides incisa and Microcotyloides impudicus, describing the first occurrence of these monogeneans for South America and in new hosts. The survey of hosts in the literature shows that M. incisa seems to have a greater Affinity with congener species of Lutjanidae and fish from other families, which may indicate a preference or specificity for fish of this family because they are congeners of their host type. The introduction of these parasites into South American waters may have occurred due to the migratory behavior of snappers, which are well distributed along the Mexican coast, where the parasites are usually reported. Here, we also bring the first occurrence of M. incisa for Lutjanus analis and Lutjanus jocu and M. impudicus for Ocyurus chrysurus and Lutjanus synagris, helping in the mapping and distribution of these monogenetic species in the Americas.

The elucidation of life-cycles of digeneans, with their successive larval stages, is facilitated by the use of molecular markers. Samples of sporocysts containing cercariae and metacercariae belonging to Monorchis Monticelli, 1893 were collected from naturally infected bivalves, Cerastoderma glaucum (Bruguière, 1789), and adult forms of Monorchis spp. were collected from sparid fishes of the genus Diplodus. All specimens were collected in the Gulf of Gabès, southern Tunisia. The identities of the examined molluscs and fishes were determined via molecular barcoding of their COI gene. Sequences of COI and ITS1 genes were also obtained for both larval and adult stages of collected parasite specimens. Genetic sequence data generated for the collected larval specimens only differed minimally from the sequence data of adults identified as Monorchis parvus; we attribute the difference to intraspecific variation. The morpho-anatomical study showed that the different stages of M. parvus collected from the Tunisian coasts had the same morphology as those reported in European waters with a lag in maturity and lower measurements. The species is recorded and molecularly characterised for the first time off the Tunisian coasts., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: A new species of the genus Ceratocolax Vervoort, 1965 is described based on specimens collected from the Tomtate grunt Haemulon aurolineatum Cuvier, caught in the coast of Angra dos Reis, off the State of Rio de Janeiro, Brazil., Methods: One hundred specimens of H. aurolineatum were purchased from the local fish market and examined for parasitic copepods. Parasites were fixed and preserved in 80% ethanol. Morphological features of the copepods were examined and drawn using an Olympus BX51 equipped with a drawing tube., Results: Ceratocolax tavaresi n. sp. can be distinguished from all congeners by the following combination of characters in the adult female: (1) second endopodal segment of leg 3 with one seta, (2) lack of stout spinules along outer margins on rami of legs 2-4, (3) genital somite without flaplike structures, (4) terminal exopodal segment of leg 4 with seven elements; and in the adult male: (1) legs 1 to 4 with 3-segmented rami (except endopod of leg 4), (2) presence of a pair of blunt processes on dorsal surface of the third pedigerous somite, (3) second endopodal segment of leg 3 with one seta., Conclusion: The number of species of Ceratocolax reported in the Atlantic Ocean was increased to three, including the new species. This is the forty-second species of copepod found parasitizing haemulid fish in marine waters from the Americas; however, the diversity of parasitic copepods off this continent is still underestimated., (© 2023. The Author(s) under exclusive licence to Witold Stefański Institute of Parasitology, Polish Academy of Sciences.)

Recent examinations of some marine fishes from off the southern coast of Iraq revealed the presence of two new species of Dichelyne (Dichelyne) Jägerskiöld, 1902 (Nematoda: Cucullanidae), both intestinal parasites, namely: D. (D.) lethrini n. sp. from the smalltooth emperor Lethrinus microdon Valenciennes (Lethrinidae, Acanthuriformes) and D. (D.) iraqiensis n. sp. from the humphead snapper Lutjanus sanguineus (Cuvier) (Lutjanidae, Acanthuriformes). Specimens are described and illustrated based on light and scanning electron microscopical examinations. Dichelyne (D.) lethrini n. sp. is mainly characterised by the length of spicules (522 µm), presence of a dorsal caecum, location of deirids at the level of the posterior end of oesophagus and the post-oesophageal position of the excretory pore, number (10 pairs) and distribution of caudal papillae in the male, and the presence of two minute terminal spines on the female tail tip. Dichelyne (D.) iraqiensis n. sp. differs from the species of the subgenus Dichelyne mainly based on the absence of caudal spines, the presence of a dorsal caecum, the length of spicules (789-884 µm), the location of deirids and the excretory pore approximately at the same level, and the size of eggs (72-78 × 42-51 µm). These new species infecting marine fishes in Iraq represent new geographic records of cucullanids of the subgenus Dichelyne from fishes in marine waters off Iraq., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

Two species of Pseudodiscocotyla Yamaguti, 1965 (Monogenea: Discocotylidae) were collected from crimson jobfish Pristipomoides filamentosus (Valenciennes) (Perciformes: Lutjanidae) off Okinawa-jima island, southern Japan. Pseudodiscocotyla opakapaka is redescribed and represents the first Japanese record. A new species, Pseudodiscocotyla mikiae n. sp., differs from Ps. opakapaka in the absence of spines around the male genital pore, the shape of the vaginal pore, the presence of spines inside the vaginal pore, and the shape of the clamp. The locations of the male genital atrium and the vaginal pore in both species were similar, and the observed armament differences of the male copulatory organ are therefore presumed to establish reproductive isolation. The phylogenetic trees for the Mazocraeidea based on the partial 28S rDNA sequences were created using new sequences of Pseudodiscocotyla mikiae n. sp., and Discocotylidae formed a sister group with the species Diclidophoridae, Macrovalvitrematidae, and Plectanocotylidae. Pristipomoides filamentosus is widely distributed across the Indo-Pacific, and Pseudodiscocotyla mikiae n. sp. could share the distribution of the host., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

Larval stages of the widely distributed digenean species Proctoeces maculatus (Looss, 1901) were reported 40 years ago from South Africa in the common octopus, Octopus vulgaris Cuvier (Octopodidae). However, the absence of adult specimens and molecular data from this region has hindered a comprehensive understanding of its distribution. In this study, we collected three species of intertidal and near-shore marine fishes [ Clinus superciliosus (L.) (Clinidae), Diplodus capensis (Smith) (Sparidae) and Sparodon durbanensis (Castelnau) (Sparidae)] along the South African coast and discovered adult specimens of P . maculatus at five localities. By employing a combination of morphological and molecular techniques, including 28S rDNA, 18S rDNA and COI mtDNA analyses, the first report of adult P . maculatus from South Africa is presented. The findings encompass a comprehensive morphological description and molecular data, illuminating the true distribution of this species in the region.

The current conservation status of Percichthys trucha (Creole perch) is Least Concern, although the population trend is considered to be decreasing. We conducted an extensive survey of parasite fauna in this species over two decades in its distribution range in Argentina. Fish were collected using gill and trawl nets. Parasites were collected, identified, and counted to calculate prevalence and mean intensity. The present work reports the parasite species infecting P. trucha, using data from our own survey and from previously published records. This information enables us to evaluate infection and distribution patterns, assess the role of P. trucha as host, determine the specificity of the parasites, and evaluate the threat represented by introduced, invasive parasites. The data set consists of a total of 453 host-parasite-locality records, of which only 15 are exclusively bibliographic. We found 44 parasite taxa: 19 digeneans, 4 monogeneans, 5 cestodes, 8 nematodes, 4 acanthocephalans, 3 crustaceans, and 1 mollusk. The most represented families were Diplostomidae, Heterophyidae, and Dactylogyridae. This study increases the number of parasite species known from 25 to 44. It can be concluded that this parasite fauna is characterized by high diversity, particularly of digeneans, and most of the parasites reproduce within this host, a pattern which is related to the top position of this fish species in the trophic webs. Six parasite species (Allocreadium patagonicum, Homalometron papilliferum, Acanthostomoides apophalliformis, Duplaccessorius andinus, Pseudodelphys limnicola, and Hysterothylacium patagonense) exhibit high host specificity (only matures in Creole perches) and are widely distributed, which could now be considered as "biogeographical core helminth fauna." Some P. trucha populations are affected by the invasion of alien fishes like Cyprinus carpio and pathogenic parasites like Lernaea cyprinacea and Schizocotyle acheilognathi. Our findings emphasize the need for further research., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: Bluegill sunfish (Lepomis macrochirus) are a North American sport fish that exhibit two different male morphotypes. Alpha-males are large, colorful, territorial, and have significant parental investment, while β-males are small, drab, and have two reproductive phenotypes, neither of which involves parental investment. Due to the two different reproductive strategies, the level of interaction between congenerics varies, which may impact parasites that are spread via close contact, such as Monogenoidea that infect the gills. Monogeneans are ectoparasites on the gills and skin of fish hosts that may cause significant pathology in high numbers and be an indicator of host behavior and interaction between hosts., Methods: In this study, 328 L. macrochirus (106 α-males, 92 β-males, and 130 females) were necropsied from 8 lakes and ponds in northwestern Virginia to identify and enumerate monogenean parasites from the gills., Results: Alpha-males had a significantly greater parasite abundance and species richness compared to β-males. This may be due to the increased size and surface area of gills in α-males, increased interaction with females during mating, and stationary behavior when guarding nests, which enhanced the chances of α-males contracting the parasites. This also led to significant differences in the monogenean communities infecting the two morphotypes, which were also significantly influenced by the size of the hosts., Conclusions: It is important in future studies regarding parasitism that behavioral morphotypes within a sex, such as α-male and β-male L. macrochirus in this study, be treated separately as behavioral and morphometric differences between them can potentially lead to differences in parasitism., (© 2023. The Author(s) under exclusive licence to Witold Stefański Institute of Parasitology, Polish Academy of Sciences.)

Examination of the gill lamellae of the Panama grunt Rhencus panamensis (Steindachner) (Haemulidae), golden snapper Lutjanus inermis (Peters), and yellow snapper Lutjanus argentiventris (Peters) (Lutjanidae) (Perciformes) from the coast of the Guerrero State (eastern Tropical Pacific) of Mexico revealed 5 species of Monogenoidea: Euryhaliotrema disparum n. sp. on R. panamensis; Haliotrematoides uagroi n. sp. on L. inermis; and E. anecorhizion Kritsky & Mendoza-Franco, 2012, E. fastigatum (Zhukov, 1976) Kritsky & Boeger, 2002, and E. paracanthi (Zhukov, 1976) Kritsky & Boeger, 2002 on L. argentiventris. Specimens found on R. panamensis were assigned within Euryhaliotrema as a new species possessing the atypical morphology of the male copulatory organ (i.e., a coiled tube with clockwise rings). Haliotrematoides uagroi n. sp. differs from Haliotrematoides striatohamus (Zhukov, 1981) Mendoza-Franco, Reyes-Lizama & Gonzalez-Solis, 2009 from Haemulon spp. (Haemulidae) from the Caribbean Sea (Mexico) in having inner blades on the distal shafts of the ventral and dorsal anchors. The present paper represents the first finding of a species of Euryhaliotrema (E. disparum n. sp.) on a species of Rhencus and the second species on a haemulid host, and H. uagroi n. sp. as the first monogenoidean species described on L. inermis. Euryhaliotrema anecorhizion, E. fastigatum, and E. paracanthi on L. argentiventris in the Pacific coast of Mexico represent new geographical records., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

Specimens of two undescribed and one known gonad-infecting species of Philometra Costa, 1845 (Nematoda: Philometridae) were collected in some marine fishes from off the southern coast of Iraq. Based on light and scanning electron microscopy, the following new species are described: Philometra tayeni n. sp. (males and nongravid females) from ovaries of the purple-spotted bigeye Priacanthus tayenus Richardson (Priacanthidae, Acanthuriformes), and Philometra nibeae n. sp. (males and gravid female) from the ovary of the blotched croaker Nibea maculata (Bloch et Schneider) (Sciaenidae, Acanthuriformes). Philometra tayeni is mainly characterised by a pair of postanal papillae and a V-shaped caudal mound in males and by their body lengths (2.42-2.99 mm), whereas P. nibeae differs from its gonad-infecting congeners parasitising scienids mainly based on the body length of males (2.29-2.49 mm) and their spicules (96-117 µm), absence of a pair of postanal papillae and shape of caudal mound consisting of two parts. Philometra piscaria Moravec & Justine, 2014 (males and nongravid females), a parasite of the orange-spotted grouper Epinephelus coioides (Hamilton) (Epinephelidae, Perciformes), is recorded from the Arabian (= Persian) Gulf for the first time; previously unknown females of this species are described., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

Marine cultured fish often suffer from Cryptocaryon irritans infection, which causes enormous mortality. C. irritans is resistant to oxidative damage induced by zinc. To develop an effective drug to control the parasite, a putative thioredoxin glutathione reductase (CiTGR) from C. irritans was cloned and characterized. CiTGR was designed as a target to screen for inhibitors by molecular docking. The selected inhibitors were tested both in vitro and in vivo. The results showed that CiTGR is located in the nucleus of the parasite, possesses a common pyridine-oxidoreductases redox active center, and lacks a glutaredoxin active site. Recombinant CiTGR exhibited high TrxR activity but low glutathione reductase activity. Shogaol was found to significantly suppress TrxR activity and enhance toxicity of zinc on C. irritans (P < 0.05). The abundance of C. irritans on the fish body decreased significantly after oral administration of shogaol (P < 0.05). These results implied that CiTGR could be used to screen for drugs that weaken the resistance of C. irritans to oxidative stress, which is critical for controlling the parasite in fish. This paper deepens the understanding of the interaction between ciliated parasites and oxidative stress., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Temporal variation of the helminth infracommunity structure in the Gafftopsail pompano Trachinotus rhodopus was studied during bi-monthly revisions of samples collected offshore from Puerto Ángel, Oaxaca (Mexican Pacific) in 2018. In total, 110 specimens of T. rhodopus were subjected to a parasitic review. Helminths found were identified to the lowest possible taxonomic level (six species and three genera) by means of morphological and molecular data. Attributes of the helminth infracommunities are described through statistical analyses, showing stability in terms of their richness throughout the year. However, variations were found in helminth abundance related to the seasonality of samplings, which may be associated with the life cycles of the parasites, the host species' gregarious behavior, the availability of intermediate hosts, and/or the diet of T. rhodopus., Competing Interests: Declaration of Competing Interest None., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Based on previous molecular phylogenetic analyses, Bothriocestus n. gen. is erected to accommodate bothriocephalid tapeworms that have an elongate scolex, a well-developed apical disc, and a narrow neck region, parasitize freshwater fishes in the Holarctic, and were previously placed in the polyphyletic genus Bothriocephalus Rudolphi, 1808 (Cestoda: Bothriocephalidea). Bothriocestus claviceps (Goeze, 1782) n. comb., a parasite of eels (Anguilla spp.) in the Holarctic region, is designated as the type species. Another species of the new genus, Bothriocestus cuspidatus (Cooper, 1917) (syn. Bothriocephalus cuspidatusCooper, 1917) is redescribed from type and voucher specimens, and new material from the type host, the walleye, Sander vitreus (Mitchill, 1818) (Perciformes: Percidae), in Manitoba and Ontario (where the type locality is located) (Canada) and in New York state and Wisconsin. Bothriocestus cuspidatus of S. vitreus is characterized primarily by the possession of a narrow, long strobila (total length up to 18 cm) composed of distinctly craspedote, trapezoidal proglottids, with primary, secondary, and tertiary proglottids differing in size, and by an arrow-shaped (=cuspidatus) scolex that is distinctly broader than the first proglottids, widest near the base in lateral view and gradually becoming broader toward the anterior end in dorsoventral view. A "dwarf" form of B. cuspidatus (total length of 9-27 mm) from Johnny darter, Etheostoma nigrum Rafinesque, 1820, and tessellated darter, Etheostoma olmstedi Storer, 1842 (both Percidae: Etheostominae), is also characterized morphologically in the present paper., (© American Society of Parasitologists 2023.)

AbstractParasites can affect host behavior, cognition, locomotion, body condition, and many other physiological traits. Changes to host aerobic metabolism may be responsible for these parasite-induced performance alterations. Whole-organism metabolic rate is underpinned by cellular energy metabolism driven most prominently by mitochondria. However, few studies have explored how mitochondrial enzymatic activity relates to body condition and parasite infection, despite it being a putative site for metabolic disruptions related to health status. We studied correlations among natural parasite infection, host body condition, and activity of key mitochondrial enzymes in target organs from wild-caught pumpkinseed sunfish ( Lepomis gibbosus ) to better understand the cellular responses of fish hosts to endoparasite infection. Enzymatic activities in the gills, spleen, and brain of infected fish were not significantly related to parasite infection or host body condition. However, the activity of cytochrome c oxidase, an enzyme involved in oxidative phosphorylation, in fish hearts was higher in individuals with a lower body condition. Activities of citrate synthase, electron transport system (complexes I and III), and carnitine palmitoyltransferase were also significantly different among organ types. These results provide preliminary information regarding the likely mitochondrial pathways affecting host body condition, the maintenance energetic requirements of different organs, and the organs' specific dependency on particular mitochondrial pathways. These results help pave the way for future studies on the effects of parasite infection on mitochondrial metabolism.

We evaluated spatial and temporal variability in parasite communities from the commercially important tropical marine fish the black-spotted croaker (Protonibea diacanthus) (Teleostei: Sciaenidae) to examine its population structure off the coast of the Northern Territory, Australia. Differences in parasite assemblage between four locations, across three seasons of the year, were used to evaluate the degree of connectivity of the sciaenid across coastal study areas. Analysis of parasite prevalence and mean intensity in these fish suggested the four sampling sites are distinct host populations. Across time, parasite assemblages at the four sites were distinct during the mid-dry (April-August) and build-up (September-November) seasons. During the wet season (December-March) there was substantial overlap in the parasite assemblages at three of the four sites indicating that fish population mixing may be occurring. Parasite assemblages at one nearshore site remained distinct across spatial and temporal scales. Our findings support the utility of parasitic organisms for elucidating the population structure of host species and reiterate the need to account for both spatial and temporal variability when performing stock discrimination analyses., (© 2023. The Author(s).)

Purpose: Introduced or invasive fish are susceptible to new parasites but can simultaneously carry infectious parasites from their native range towards new hosts. Screening these parasites is key to address the health of fish populations and spread of diseases., Methods: In this study, we sequenced a Coccidia parasite, for the first time from the blenny Omobranchus sewalli, introduced in the northern coast of Brazil with an Indo-Pacific origin., Results: Only one individual was infected, its genetic sequence matched (over 99%) with two lineages of undetermined species, belonging to the genus Goussia, sequenced from three marine fish species (Mulloidichthys flavolineatus, Lutjanus kasmira, and Selar crumenophthalmus) in Hawaii., Conclusions: Phylogenetic analysis suggests considerable differentiation between the Goussia detected and other Goussia spp. sequenced from North Atlantic marine fish, thus we cannot exclude the possibly that this parasite was carried by O. sewalli from its native Indo-Pacific range., (© 2023. The Author(s) under exclusive licence to Witold Stefański Institute of Parasitology, Polish Academy of Sciences.)

Strange oceanographic events such as El Niño and La Niña may have indirect effects on the local transmission processes of intestinal parasites due to the reduction or increase in populations of potential intermediate or definitive hosts. A total of 713 individuals of Lutjanus inermis (Peters) were collected over an 8-year period (October 2015 to July 2022) from Acapulco Bay, Mexico. Parasite communities in L. inermis were quantified and analysed to determine if they experienced interannual variations in species composition and structure as a result of local biotic and abiotic factors influenced by oceanographic events, such as El Niño-Southern Oscillation (ENSO), or La Niña, the cool phase of the ENSO climate pattern. Twenty-six taxa of metazoan parasites were recovered and identified: two Monogenea, eight Digenea, two Acanthocephala, four Nematoda, one Cestoda, seven Copepoda, and two Isopoda. Species richness at the component community level (8 to 17 species) was similar to reported richness in other species of Lutjanus Bloch. Parasite communities of L. inermis exhibited high inter-annual variation in the abundance of component species of parasite. However, the species richness and diversity were fairly stable over time. Climatic episodes of El Niño and La Niña probably generated notable changes in the structure of local food webs, thus indirectly influencing the transmission rates of intestinal parasite species. Changes in species composition and community structure of parasites possibly were due to variations in feeding behaviour during the events and differences in the host body size.

Cryptocaryon irritans is one of the most harmful marine parasites in mariculture. Copper sulphate is often used to kill parasites and the influence of copper sulphate on the tomont stage of C. irritans was explored in this study. The results showed that excystment rate was not significantly affected when tomonts were exposed to 5 mg/L (76.7%) and 10 mg/L (78.9%) of copper sulphate for 3 h. However, excystment rate was significantly inhibited when exposed to 15 mg/L (33.3%) for 3 h and 5 mg/L (28.9%), 10 mg/L (33.3%) and 15 mg/L (33.3%) for 6 h. After treatment with high concentrations of copper sulphate, the interior of the tomonts was fuzzy under the microscope, and the division process could not be observed. Metabolomic results combined with preliminary transcriptome analysis results showed that the tomonts were induced to produce linoleate, riboflavin, inositol and other substances under the stress of Cu 2+ , which affected the antioxidant mechanism of the body. Using MDA content determination and antioxidant enzyme activity analysis, copper sulphate was found to cause oxidative damage to tomonts by affecting the generation of metabolites, leading to the death of tomonts., (© 2023 John Wiley & Sons Ltd.)

Two new species of copepods assigned to the genus Acusicola Cressey, 1970 (Cyclopoida: Ergasilidae) are proposed based on post-metamorphic adult females, parasitizing the gills of two actinopterygian fish off Brazil namely, the Tripletail Lobotes surinamensis (Bloch) (Lobotidae), collected in the coastal zone of the State of Pará, near Curuçá Municipallity, and the Swordspine snook Centropomus ensiferus Poey (Centropomidae) collected in Sepetiba Bay, State of Rio de Janeiro, Brazil. Acusicola iamarinoi n. sp. parasite of L. surinamensis, differs from its closet congeners based on the first segment of the antennule armed with 10 setae, the presence of a maxillule armed with four elements and a pair of blunt processes dorsally on the fourth pedigerous somite. Acusicola pasternakae n. sp., collected from C. ensiferus, can be distinguished from its closest congeners based on the membranous sheath of the first endopodal segment of antenna with horizontal marks, the first segment of the antennule armed with 11 setae and a spine on the last exopodal segment of leg 2. This is the first report of representatives of Acusicola parasitizing fish of the families Lobotidae and Centropomidae as well as new geographical records of the genus in the coast of State of Pará and in Sepetiba Bay, Brazil., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

The Chinese sleeper Perccottus glenii Dybowski, 1877 is an invasive fish species rapidly expanding in Siberia and Europe. Its native range encompasses the Far East region of Russia, northeastern China and northern North Korea. We studied species composition, prevalence, mean abundance and variance of mean abundance of macroparasites of the Chinese sleeper in the native and the introduced range. The species composition of the parasite component communities differed considerably in the native and the introduced range. The frequency distributions of prevalence, mean abundance and variance of mean abundance of the parasites did not demonstrate any significant differentiation between the two parts of the host range. However, an analysis of the abundance-occupancy and the abundance-variance relationships revealed that the parasite component communities in the two parts of the host range were quite distinct. In the native range, prevalence increased faster and variance increased more slowly with the increasing abundance of the parasites than in the introduced range. These features are mostly associated with considerably increased prevalence, abundance and aggregation of the host-specific cestode Nippotaenia mogurndae in recipient water bodies as compared with the native habitats., Competing Interests: Declaration of Competing Interest The authors declare no competing interests., (Copyright © 2022 Elsevier B.V. All rights reserved.)

A new species of parasitic copepod, Colobomatus deborae n. sp., belonging to the cyclopoid family Philichthyidae Vogt, 1877, is proposed based on adult female specimens collected from the interorbital canals of the Caitipa mojarra Diapterus rhombeus (Cuvier) (Gerreidae) from Sepetiba Bay, off the State of Rio de Janeiro, southeastern Brazil. The new species closely resembles six species of Colobomatus Hesse, 1873, but differs from these close congeners based on the combination of the following characters: lateral cephalic processes forked basally with sharp tips, midventral cephalic process representing about one third of the length of the laterals, thoracic processes forked and caudal rami with a pair of unequal processes. Together with the new species described in the present study, the philichthyid fauna of Brazil rises to 10 species reported from 14 Brazilian marine fish species. This is also the third report of Colobomatus in a gerreid fish, but the first species found parasitizing the genus Diapterus., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

The present study provides new host and first description of the male of Colobomatus stelliferi Pombo, Turra, Paschoal & Luque, 2015 (Copepoda, Philichthyidae), collected from the mandibular canals of the Argentine croaker Umbrina canosai Berg, off the State of Rio de Janeiro, Brazil. Four out of nine fish analyzed (prevalence 44.4%) were parasitized by C. stelliferi and showed a mean intensity of 2.5 (range 2-3, standard deviation 1.25). Adult males of C. stelliferi can be differentiated from their closest congeners based on the combination of the following characters: maxilliped with naked basal segment and small apical spine, the presence of two elements on the second endopodal segment of the antenna, and the presence of leg 4. This parasitic copepod is seemingly host-specific to fish of the family Sciaenidae and its occurrence is restricted to the Brazilian coast. The present results contribute to our knowledge of the biology of C. stelliferi and of the parasitic copepod fauna from Brazil., (© 2022. The Author(s), under exclusive licence to Springer Nature B.V.)

Haemulidae represents one of the most diverse, widespread and conspicuous families of Perciformes, in which most species are marine, some brackish and rarely from freshwater. From April 2009 to July 2012, 120 specimens of Conodon nobilis, 60 Orthopristis rubra and 50 Anisotremus virginicus were collected off the State of Rio de Janeiro, Brazil, and analyzed for metazoan parasites. A total of 16 parasite taxa were found on/in A. virginicus, 19 on/in Co. nobilis and 21 on/in O. rubra, in which ectoparasites were most common on A. virginicus and Co. nobilis and endoparasites in O. rubra. All parasites showed aggregate pattern of distribution (discrepancy index values higher than 0.70). Mean abundance, species richness and Brillouin index (diversity) differed among the host species, i.e., O. rubra showed the highest values, followed by A. virginicus and Co. nobilis with intermediate and lowest values, respectively. At infracommunity level was possible to observe high similarity of parasite composition among the three host species. The digeneans Leurodera decora and Monorchis latus, and the acanthocephalan Koronacantha sp. represent new locality records off Brazil. Moreover, five, four and two taxa are reported, for the first time, parasitizing Co. nobilis, A. virginicus and O. rubra, respectively.

An undescribed species of KannaphallusUnnithan, 1957 (Monogenoidea: Heteraxinidae) was collected from the gills of the golden trevally Gnathanodon speciosus (Forsskål) (Carangidae) from Moreton Bay, Queensland, during January 2016 and from Ningaloo Reef, Western Australia, during December 2021 and June 2022. The diagnosis for Kannaphallus was emended and the new species, Kannaphallus raphidium, was described. Kannaphallus virilis of Young, nec Unnithan was placed in synonymy with K. raphidium. The distal components of the male reproductive system and the arrangement of the clamp rows of the haptor occurred as mirror images among specimens of K. raphidium, suggesting that the respective antipodes of K. raphidium may have reproductive implications and function in the site selection of the parasite on the host's gills. A specimen of K. raphidium from Western Australia was sequenced for the cytochrome c oxidase subunit 1 (COI) mtDNA and ITS2 rDNA barcoding markers, and the phylogenetically informative 28S rDNA marker. Maximum likelihood and Bayesian inference analyses based on a partial 28S rDNA alignment, including all comparable heteraxinid sequence data available, resolved the Heteraxininae and Cemocotylinae as reciprocatively paraphyletic and provided evidence that Kannaphallus may be paraphyletic. No taxonomic changes concerning the subfamilies and genera of the Heteraxinidae were proposed. Finally, Kannaphallus univaginalisRamalingam, 1960 and Cemocotylelloides univaginalis (Ramalingam, 1960) Nitta, Kondo, Ohtsuka, Kamarudin, and Ismail, 2022 are considered nomen nuda sensu the International Code of Zoological Nomenclature., (© American Society of Parasitologists 2023.)

Copper alloy sheets have been shown to prevent cryptocaryoniasis. Therefore, we studied the potential efficiency of copper alloy mesh (CAM) in aquaculture tanks to prevent cryptocaryoniasis outbreaks. The effectivenesses of CAM against the tomont stage of Cryptocaryon irritans and in protecting fish from cryptocaryoniasis were tested both in vitro and in vivo. The mortality rate of C. irritans tomonts increased as the contact time with CAM rose and peaked at 70 min (100% of mortality). Morphological changes were observed such as the shrinking of the protoplasm of the treated tomonts, resulting in a larger gap between the cytoplasm and the cyst wall. Mitochondrial dysfunction due to shrinkage in the inner portion, outer and inner mitochondrial membrane damage and cytoplasmic vacuolation was revealed by ultrastructural analysis. The use of CAM effectively preventing reinfection was also provided. In comparison with group B (infected fish without CAM), both groups A (uninfected fish as a control group) and C (infected fish treated with CAM) had a 100% survival rate until the end of the trial. CAM has the same anticryptocaryoniasis effect as copper alloy sheets but is more advantageous due to its lightweight, reduced labor cost and lower purchase cost. It is noticeable that CAM exposure also prevents the excessive accumulation of copper ions in aquaculture sea water., (© 2022 John Wiley & Sons Ltd.)

Parasites may have various effects on their host's health. It is important to determine the type of the effects but also to decipher the physiological mechanisms underlying a parasitic infection. In this study, swimming ability (by a fixed swim speed test) and haematological analyses (by blood parameters) were compared between juvenile fish Girella laevifrons non-parasitised and parasitised with metacercariae of Prosorhynchoides sp. Fish were infested in the laboratory using natural parasitised mussels. Aerobic swimming time, total erythrocyte and leukocyte counts were compared among four groups of fish: non-parasitised (NP), non-parasitised but manipulated (NPM), parasitised 3 days (PT1), and 10 days (PT2) post-infection. Differentiated haematological components were also compared among NP, PT1 and PT2 fish groups. Parasitised fish (PT1 and PT2) swam between 32% and 55% less time than unparasitised fish. Erythrocyte counts were lower in PT1, indicating anemia, and total leukocyte counts were higher in PT1, showing immune action. Macrophages and basophils were observed only in parasitised fish, independent of the post-infection time. There was a negative correlation between swimming time and leukocyte counts. Increased leukocytes in the blood indicate activation of the innate cellular immune response, which may be metabolically costly for the host. Moreover, the anemia in parasitised fish would reduce the oxygen transport necessary to carry out aerobic exercise, reducing the swimming capacity. In fish several days post-infection (PT2), the erythrocytes count reached normal values, and some kinds of leukocytes decreased in comparison to fish PT1. This suggests that parasitised fish with metacercariae were recovering., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Patterns of the rockcod Notothenia coriiceps infection with helminths were analysed to understand the dynamics of parasite communities in this Antarctic fish and to test their stability over time. The study was performed using helminth samples collected from 183 N. coriiceps in 2014-2015 and 2020-2021 in the vicinity of the Ukrainian Antarctic station (UAS) "Akademik Vernadsky", Galindez Island, Argentine Islands, West Antarctica. Overall, 25 helminth taxonomical categories (nine trematodes, four cestodes, five nematodes, and seven acanthocephalans) were subjected to analysis. A direct comparison of the helminth population characteristics showed that nine species significantly changed their infection parameters during the 6 years between the samples. Seven of them (Pseudoterranova sp., Contracaecum sp., Ascarophis nototheniae, monolocular metacestodes, bilocular metacestodes, Metacanthocephalus rennicki, and Diphyllobothrium sp.) were found to have a significant impact on the differences between helminth infracommunities in 2014-2015 and 2020-2021. Most studied patterns of helminth component community appeared to show a stable tendency, and observed fluctuations were close to the steady trend. Slight but significant changes in the infection patterns observed in this study might have been caused by changes in the populations of intermediate, paratenic, and definitive hosts of helminths (marine invertebrates, mammals, and birds), which participate in helminth transmission in Antarctic ecosystems., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: Behavioral variation among conspecific organisms can have substantial ecological impacts, particularly affecting parasite infection. Bluegill sunfish (Lepomis macrochirus) exhibit multiple male reproductive morphotypes that differ in their size, feeding dynamics, and reproductive behavior. This study investigated how these morphological and ecological differences contribute to the patterns of infection by strigeid trematodes., Methods: A total of 1961 L. macrochirus was collected from 14 lakes and ponds in northwestern Virginia, USA, and were necropsied to identify and enumerate three common strigeid parasites, white grub (Posthodiplostoum spp.), black grub (Uvulifer ambloplitis), and yellow grub (Clinostomum marginatum) infecting the fish and determine if there were different infection patterns among sexes and morphotypes., Results: Strigeid infections in L. macrochirus α-males were in greater abundance compared to females and β-males. Additionally, α-males had greater strigeid infection in the kidneys and fins, while females and β-males accumulated more parasites in the liver and body tissues., Conclusions: Increased nesting responsibilities and potential interaction with snail intermediate hosts by α-males may lead to the differences in infection patterns. The distinction of morphotypes revealed significant differences in abundance and distribution of parasite infections between the sexes of L. macrochirus, trends that were masked when male morphotypes are combined., (© 2022. The Author(s) under exclusive licence to Witold Stefański Institute of Parasitology, Polish Academy of Sciences.)

Purpose: The present study deals with a redescription of the copepod Lernaeenicus longiventris Wilson, 1917 (Copepoda: Siphonostomatoida: Pennellidae) found on the Pacific crevalle jack Caranx caninus Günther, using morphological and molecular analyses., Methods: Fish were collected off Mazatlán Port (23° 12' N, 106° 26' W), in the State of Sinaloa, Mexico (southeastern Gulf of California). The copepods were morphologically analyzed by light microscopy. Sequences of the COI mtDNA gene were generated for the first time for this species. These sequences were compared to COI sequences from six species of Lernaeenicus available in GenBank., Results: The specimens of the present study exhibited a cephalosome without apparent lateral processes, which were originally described for L. longiventris. No remarkable differences were observed with previous descriptions regarding appendages and body proportions. The phylogenetic tree based on COI sequences showed that L. longiventris was closer to L. radiatus although with low bootstrap values support in ML tree, both species formed a sister clade of L. sprattae., Conclusions: Lernaeenicus longiventris is the unique species of the genus in the Mexican Pacific and the Gulf of California, and also the unique species of Lernaeenicus infecting C. caninus. Molecular data of L. longiventris from host and locality type are required to avoid misidentification of this species., (© 2022. The Author(s) under exclusive licence to Witold Stefański Institute of Parasitology, Polish Academy of Sciences.)