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The morphological characterisation of Diplozoidae spp. is highly reliant on the details of the sclerotised components of the hooks and clamps in the haptor. Only six species of Paradiplozoon (Diplozoinae) have been described from Africa, four of which have adequate morphological and even comparative ITS2 rDNA data available. However, the descriptions of Paradiplozoon ghanense (Thomas, 1957) and Paradiplozoon aegyptense (Fischthal & Kuntz, 1963) lack essential taxonomic information, specifically the details for their haptoral sclerites. As such, all available material from museum collections for these two species were studied using light microscopy to supplement the original morphometric descriptions. The holotype and paratypes of P. aegyptense were studied, but only voucher material for P. ghanense could be sourced. However, this voucher material for P. ghanense was deposited by the species authority and bore a striking resemblance to the illustrations and collection details from the original description. They were thus identified as the type series for the taxon, with a lectotype and paralectotype designated. Both P. ghanense and P. aegyptense could be readily distinguished from other taxa based on the supplementary data generated here, supporting their distinctness. The haptoral sclerites of P. aegyptense were most similar to those of Paradiplozoon krugerense Dos Santos & Avenant-Oldewage, 2016, also described from Labeo spp., while the sclerites of P. ghanense were most similar to Paradiplozoon bingolense Civáňová, Koyun & Koubková, 2013 and Paradiplozoon iraqense Al-Nasiri & Balbuena, 2016. Additionally, a voucher of P. aegyptense collected from the alestid type host of P. ghanense was reidentified as the latter species here. This greatly simplified the known host specificity for Paradiplozoon spp. in Africa, with P. aegyptense now exclusively reported from Cypriniformes (Cyprinidae and Danionidae), and P. ghanense restricted to Characiformes (Alestidae). The occurrence of all diplozoids from non-cyprinoid hosts was also investigated and several records of diplozoids occurring on non-cyprinoid hosts were collated and scrutinised. Excluding the two instances of diplozoids described and exclusively occurring on Characiformes fishes ( P. ghanense and Paradiplozoon tetragonopterini (Sterba, 1957)), most other non-cyprinoid collections appear sporadic and unsubstantiated, but warrant further investigation supported by diligent taxonomic data. Even though the morphometric descriptions of both P. ghanense and P. aegyptense were fully reported on here, additional material will be needed to study their genetic profiles and phylogeny., Competing Interests: Annemarie Avenant-Oldewage is an Academic Editor for PeerJ., (© 2024 Dos Santos and Avenant-Oldewage.)

Neoergasilus japonicus, a fish ectoparasite indigenous to eastern and southern Asia, has been introduced to various regions, including Europe and North and South America, where it spreads at an alarming rate. The parasite is not host-specific. It was also collected from the Vaal-Orange and Limpopo river systems in South Africa. This report describes the morphology of the wound-inflecting structures in N. japonicus and relates their morphology to the pathological effect on Tilapia sparrmanii. Host tissue with parasites attached was imbedded in resin for histological sectioning and stained with haematoxylin and eosin. Additional specimens were prepared for scanning electron microscopy. Adult female parasites attach by inserting the hooked tips of the antennae into the epidermis. The maxillulae are minute but have sharp tips. The maxillae have sharp tips on the endopod and brush-like setae on the exopod. The mandibles are armed with sharp tips. These structures are used to remove the epidermis of the host and brush it into the buccal cavity. Host tissue in the intestine confirms that adult females consume host tissue leaving the dermis exposed to opportunistic diseases. The microscopic size of the parasite prevents casual observation, and its occurrence in Africa is, therefore, probably underreported., (© 2023 The Authors. Journal of Fish Diseases published by John Wiley & Sons Ltd.)

Females of species of Lamproglena von Nordmann, 1832 are parasitic on the gills of teleost fishes and the 38 nominal species are based on mainly morphological data. Only four of these species have been genetically characterised and no mitochondrial data are available for the genus. The present study aimed to provide representative ribosomal DNA (rDNA) data for two additional species of Lamproglena from Africa: Lamproglena clariae Fryer, 1956 and Lamproglena hoi Dippenaar, Luus-Powell et Roux, 2001, alongside mitochondrial DNA (mtDNA) for these and two other African species, Lamproglena hemprichii von Nordmann, 1832 and Lamproglena monodi Capart, 1944. The four species were collected from Clariidae, Cyprinidae, Alestidae and Cichlidae, respectively. Representative 18S rDNA and 28S rDNA data were obtained for L. clariae and L. hoi, while cox1 mtDNA was obtained for all four species. The respective haplotypes supported the distinctness of all species using all three gene regions investigated. Interestingly, species appeared to be grouped more by geographical origin than host family, with L. hoi more closely related to other African species than to Asian species also collected from cyprinid hosts. Even though the results presented here greatly add to the molecular data available for Lamproglena, there are still 32 (>80%) species for which no genetic data are available. The interpretation of the results presented here is thus preliminary and much more data are required before the phylogeny of this genus, and other members of the family, such as Lernaea Linnaeus, 1758, can be studied appropriately.

Gyrodactylus sprostonae Ling, 1962 is a highly invasive parasite reported across freshwater environments of the northern hemisphere. The taxon was originally described from Carassius auratus (Linnaeus, 1758) and Cyprinus carpio Linnaeus, 1758 in China. This parasite has never been reported in Africa or the southern hemisphere. Recently, this taxon was collected from an indigenous yellowfish, Labeobarbus aeneus (Burchell, 1822), in the Vaal River, South Africa. The present study includes the conclusive identification of the gyrodactylid parasites collected from L. aeneus , including additional taxonomic data, using microscopy and molecular techniques. Microscopy included light microscopy (LM) of whole worms and scanning electron microscopy (SEM) of isolated haptoral sclerites. Additionally, morphometric data were obtained from SEM and compared to that generated using LM. For molecular analysis, the internal transcribed spacer (ITS) region of rDNA was amplified and phylogenetic topologies constructed. The specimens were morphometrically and genetically highly similar to other data for G. sprostonae. Additional point-to-point measurements and ITS rDNA sequences were generated for the taxon, contributing to the morphometric and molecular data for G. sprostonae. The study also includes the first study of the isolated haptoral sclerites of the taxon using SEM, with similar morphometric results to LM. This is the first record of G. sprostonae in the southern hemisphere and from a new, indigenous African host, L. aeneus , indicating host switching to smallmouth yellowfish. Furthermore, these results expand on the knowledge of the distribution of invasive parasites in South Africa, as well as Gyrodactylus species diversity in Africa.

In nematodes, the structure of male copulatory organs is a significant taxonomic distinguisher and includes the morphometry of the spicules. The description of these structures mainly relies on the study of whole mounts using light microscopy. In rare instances, protruding spicules have been described with scanning electron microscopy. Even fewer studies have described the ultrastructure of isolated spicules following their isolation. In the present study, two different methods of spicule isolation were performed on two parasitic camallanid nematodes, Procamallanus (Procamallanus) pseudolaeviconchus Moravec & van As, 2015 and Paracamallanus cyathopharynx (Baylis, 1923), from African sharptooth catfish to determine the practicality and efficiency of the methodologies. The first method involved using sharpened tungsten needles and microdissection of the spicule pouch to free the spicules, followed by soft tissue digestion if necessary. Alternatively, the spicules were isolated through mechanical release instead of dissection in a method developed in the current study. This involved freeing the spicules from surrounding soft tissue by placing live specimens between a coverslip and a glass slide in a drop of water and exerting pressure with small rotational movements. Both methods yielded favourable results, but Method 2 is recommended for future studies due to the many advantages.

Two species of Spinitectus Fourment, 1884 have been recorded from southern Africa, namely Spinitectus polli Campana-Rouget, 1961 and Spinitectus petterae Boomker, 1993, both from the Limpopo River system. Spinitectus petterae was described from North African catfish, Clarias gariepinus (Burchell), whereas S. polli infects squeakers, Synodontis spp. During parasitological surveys in the Vaal River system (Orange River catchment), Spinitectus specimens were collected from C. gariepinus. These systems are adjacent but not connected. Therefore, this study aimed to identify the specimens collected using morphological and molecular techniques. The morphological study included light and scanning electron microscopy of whole specimens and excised spicules. Specimens were genetically characterised using 18S rDNA, 28S rDNA and cox1 mtDNA. Additionally, immature specimens of S. petterae were collected near the type locality. Morphological characteristics were most similar to S. petterae from C. gariepinus, whereas genetic data were dissimilar to all available data for the genus. Additional morphological characteristics noted for S. petterae in the present study were the details of the left and right spicule structure and the porous structures on the pseudolabia. Specimens from the Vaal River system differed from those originally described as S. petterae by additional spines posterior to the third ring, lacking caudal alae and variable total body and male oesophagus length. Based on 18S rDNA, haplotypes from the type locality varied only slightly from the study material, supporting the morphological identification. However, 28S rDNA and, more conspicuously, cox1 mtDNA displayed substantial variation between specimens from these localities, which needs further investigation. Haplotypes generated in the present study were highly dissimilar to those characterised for S. petterae from Tanzania and Egypt. Nevertheless, the nematodes collected from C. gariepinus in the Vaal River system are considered S. petterae. This study expands the geographical distribution and adds additional morphological and genetic information for S. petterae, contributing to the limited knowledge of African species of Spinitectus.

Clarias gariepinus collected from Lake Heritage, Crocodile River, were found to harbour camallanid nematodes. Previously, Boomker (1982) surveyed the Hartbeespoort Dam, downstream of the current study site, and identified a high prevalence of Procamallanus (Procamallanus) laeviconchus and Paracamallanus cyathopharynx. Since then, Procamallanus (Procamallanus) pseudolaeviconchus was described from C. gariepinus suggesting reconsideration of the identifications of Procamallanus species in historical studies from clariids . The aim of the current study was to definitively identify the nematodes collected from C. gariepinus in Lake Heritage , using morphological and molecular analyses . Morphological study consisted of light and scanning electron microscopy which confirmed the identity P. (P.) pseudolaeviconchus and P. cyathopharynx. This included descriptions of the detailed morphology of isolated buccal capsules for both species using soft tissue digestion, notably for the first time for P. (P.) pseudolaeviconchus . The morphology of isolated spiculae of both species was described for the first time using SEM. Molecular analyses included genetic characterisation of the small ribosomal subunit (18S) rDNA and cytochrome oxidase 1 (CO1) mtDNA. Genetic data supported the morphological identification of both species, however, divergence was detected in CO1 mtDNA data for P. cyathopharynx indicating two distinct lineages . Due to this variation, the morphometry of P. cyathopharynx specimens were revisited including statistical re-evaluation. No robust morphological traits were identified to support CO1 mtDNA lineages and all specimens were considered conspecific. In terms of camallanid biodiversity in the Crocodile River system, it is similar to that in Boomker (1982), despite the altered water quality from past acid mine pollution in the river., Competing Interests: The authors confirm that there is no conflict of interest., (© 2022 The Authors.)

Spinitectus spp. (Rhabdochonidae) are enteric nematodes characterized by annular spines. At the anterior end, these spines assist attachment and aid penetration into the host tissue. During parasitological surveys of the Vaal River system from three localities, below the Vaal River Barrage in the Vaal Dam surrounding UJ island and below the Grootdraai Dam, Spinitectus specimens were collected from the stomach lining of the sharptooth catfish, Clarias gariepinus (Burchell, 1822). Histopathological effects induced by Spinitectus petterae Boomker, 1993 on C. gariepinus has not been studied. Thus, the aim of this study was to describe the histopathology induced by S. petterae. For light microscopic examination, tissue samples with attached S. petterae were sectioned and stained with haematoxylin and eosin. Additionally, attached nematodes were also studied using scanning electron microscopy. Leukocytes were counted with the Disector principle. Standard infection parameters (prevalence, mean intensity and abundance) were calculated and compared to host parameters. Prevalence varied greatly (11.77% to 100%) between localities. Histopathology induced by S. petterae to C. gariepinus stomach (cardiac region) consisted of significant leukocyte infiltration, acute ulcerations and chronic granuloma formation. This was similar to the pathology of other Spinitectus occurring in host anterior intestine and stomach, but granuloma formation had not been previously reported and this suggests chronic infection in wild caught fish., (© 2022 John Wiley & Sons Ltd.)

Clarias gariepinus (Burchell, 1822) is one of the two most actively cultured freshwater fish in Africa and therefore, economically important. Specimens of this species were purchased from a fish farm near Hartbeespoort Dam (North West, South Africa) and introduced into the tanks of the research aquarium in the Department of Zoology at the University of Johannesburg. However, the skin of these fish was infected with Macrogyrodactylus congolensis (Prudhoe, 1957), which proliferated profusely in the favourable conditions of the aquarium, posing a potential threat to its host. The current study was aimed at examining the pathology caused by M. congolensis on the skin of C. gariepinus. Species identification of the parasite was confirmed using light microscopy (LM), scanning electron microscopy (SEM) and DNA barcoding of the internal transcribed spacer region. Examination of the pathology was studied using LM of haematoxylin and eosin-stained sections (epoxy embedded) and SEM of parasites attached to the hosts' skin. Infected skin exhibited excessive mucus production, corroborated by an increased number of mucus cells alongside proliferated and abnormally enlarged club cells, resulting in varying thickness of the epidermal layer. At the site of attachment, the basement membrane detached from the dermis. Hamulus points and marginal hooks of the parasite pierce through the hosts' skin resulting in tearing. Epidermal cells and melanin granules were observed in the intestinal lumen of the parasite. Melanin granules were absorbed by the parasite's intestinal epithelium confirming that the parasite feeds on host skin tissue., (© 2022 John Wiley & Sons Ltd.)

Macrogyrodactylus congolensis (Prudhoe, 1957) is one of six species of Macrogyrodactylus, all of which are endemic to Africa. This monogenean is a host-specific ectoparasite of the African sharptooth catfish, Clarias gariepinus (Burchell, 1822). It attaches to the host with a posterior haptor armed with sclerites. The specific morphology of sclerites is taxonomically significant and usually studied using light microscopy. The aim of the present study was to confirm the identification of macrogyrodactylid parasites using classic morphology (light microscopy of glycerine ammonium picrate mounted specimens) and molecular techniques (18S rDNA, ITS rDNA and cytochrome oxidase subunit 1 (COI) mtDNA). Additionally, the sclerites were accurately described with a technique not previously used for the genus, whereby haptoral sclerites were isolated by removing the encapsulating soft tissue with a digestion buffer and studied with scanning electron microscopy (SEM). Morphology and morphometry of studied specimens corresponded to available data for M. congolensis, confirming the identity of the parasite. All previous descriptions were summarized in a table and discrepancies discussed. Molecular analysis also confirmed the specimens to be M. congolensis, but ITS rDNA and COI mtDNA was more reliable than 18S rDNA in this regard. The isolation of haptoral sclerites and their study using SEM was successful, resolving the morphology of all sclerites. This study provided the first reconstruction of the haptor of a Macrogyrodactylus species following SEM analysis, as well as the first mtDNA for M. congolensis. Further study of isolated haptoral sclerites of other macrogyrodactylids is required to determine the full benefits of studying their isolated sclerites.

Adult trematodes of Allocreadium Looss, 1900 (Digenea) infect the intestine of mostly freshwater fishes in Asia, Europe, Africa and the Americas. During routine parasitological surveys in the Vaal River system, adult trematodes were collected from the intestine of smallmouth yellowfish, Labeobarbus aeneus (Burchell). The trematodes were confirmed to represent a member of Allocreadium and did not match any existing taxon. Therefore, they are described as a new species, Allocreadium apokryfi sp. n. The morphology of the new species most closely resembles that of Allocreadium aswanense El-Naffar, Saoud et Hassan, 1984, but it differs from it by having a bipartite internal seminal vesicle, wider eggs, a shorter intertesticular distance, an intestinal bifurcation at the ventral sucker level, a ventral sucker that is larger than the oral sucker, and a genital pore near the intestinal bifurcation or the ventral sucker. The surface topology of the new species is notably different from that of other allocreadiids. Papillae were observed in the ventral sucker and surrounding both ventral and oral suckers, but the number and arrangement of the latter were not consistent among specimens. The protruding cirrus of A. apokryfi sp. n. was described using SEM and is the first such observation for the genus. Genetic characterisation showed that the new species was clearly distinct from other Allocreadium spp. using both 18S (nucleotide difference 1.3-9.1%) and 28S (4.7-6.5%) rDNA, forming a well-supported clade in Allocreadium. The presence of A. apokryfi sp. n. in a well-studied river is unexpected, and considering the diet of its host and the scarcity of Allocreadium in Africa, the possible biology of this species is discussed herein.

This study reports on the status of metazoan fish parasites in Lake Victoria following the establishment of introduced Lates niloticus (Latidae) and Oreochromis niloticus (Cichlidae) and changes in environmental quality. For this study, 412 fish specimens were examined for parasites: 103 L. niloticus, 165 O. niloticus, 82 Haplochromis piceatus and 62 H. humilior (endemic cichlids). In total, 25 parasite taxa were identified: Lates niloticus (6), O. niloticus (19) and Haplochromis spp. (13). The myxosporean Henneguya ghaffari, prevalence (P) = 79% and the monogenean Diplectanum lacustris (P = 34%), were the dominant parasites on L. niloticus. Myxobolus sp. (P = 44%) was dominant on O. niloticus while for the haplochromines, metacercariae of 'Neascus' sp. (Diplostomidae) was dominant (P = 37%). Contrary to reports of high diversity of monogeneans on endemic species, the haplochromines harboured only Cichlidogyrus gillardinae (P = 6.9%). Oreochromis niloticus harboured seven monogenean species: Cichlidogyrus sclerosus, C. halli, C. tilapiae, C. quaestio, Scutogyrus longicornis, Gyrodactylus cichlidarum and G. malalai-they appear to have been co-introduced with the fish. Cichlidogyrus gillardinae, C. quaestio, G. malalai and the acanthocephalan Acanthogyrus (Acathosentis) tilapiae are recorded for the first time in Lake Victoria, representing new geographical records. Presence of A. (A) tilapiae in Haplochromis spp. indicates possible spillover from O. niloticus. Low prevalence and diversity of monogeneans, crustaceans and glochidia on the fish corresponded with increased pollution in the lake. Overall, changing environmental conditions and introductions of fish species have contributed to parasite community changes in Lake Victoria.

In 2016, an intense copepod infection was recorded from a reservoir in proximity to the Danube River in Hungary from visibly emaciated wels catfish, Silurus glanis . The parasite-induced pathology was described but parasite identity was not conclusive. Additional sample collections in 2017 and 2018 allowed for identification using both light and scanning electron microscopy, alongside genetic characterisation. The copepods were confirmed to be ergasilids, Sinergasilus major , distinctly different from any previous infection on silurids in Europe. This is the first record of this parasite from Hungary and the first host record from wels catfish., (© 2021 The Author(s).)

The use of molecular tools in the study of parasite taxonomy and systematics have become a substantial and crucial component of parasitology. Having genetic characterisation at the disposal of researchers has produced mostly useful, and arguably more objective conclusions. However, there are several groups for which limited genetic information is available and, coupled with the lack of standardised protocols, renders molecular study of these groups challenging. The Diplozoidae are fascinating and unique monogeneans parasitizing mainly freshwater cyprinid fishes in Europe, Asia and Africa. This group was studied from a molecular aspect since the turn of the century and as such, limitations and variability concerning the use of these techniques have not been clearly defined. In this review, all literature and molecular information, primarily from online databases such as GenBank, were compiled and scrupulously analysed for the Diplozoidae. This was done to review the information, detect possible pitfalls, and provide a "checkpoint" for future molecular studies of the family. Hindrances detected are the availability of sequence data for only a limited number of species, frequently limited to a single sequence per species, and the heavy reliance on one non-coding ribosomal marker (ITS2 rDNA) which is difficult to align objectively and displays massive divergences between taxa. Challenging species identification and limited understanding of diplozoid species diversity and plasticity are also likely restricting factors, all of which hamper the accurate taxonomic and phylogenetic study of this group. Thus, a more integrated taxonomic approach through the inclusion of additional markers, application of more rigorous morphological assessment, more structured barcoding techniques, alongside thorough capturing of species descriptions including genetypes, genophore vouchers and reference collections in open sources are encouraged. The pitfalls highlighted are not singular to the Diplozoidae, and the study of other groups may benefit from the points raised here as well.

This study provides additional taxonomic features based on scanning electron microscopy (SEM) and molecular data for Paracamallanus cyathopharynx ( Baylis, 1923 ) (Nematoda: Camallanidae). Parasites were collected from the posterior end of the intestine of cultured freshwater Sharptooth catfish Clarias gariepinus (Burchell, 1822) from Kibos fish farm, Kisumu County, Kenya, from December 2017 to March 2018. Additional taxonomic features recorded for P. cyathopharynx include the occurrence of 4-5 equal length digitate processes on the caudal end of the female, 4 processes (2 smaller and 2 larger) on the male caudal end, and a description of the shape of the distal tip of the right spicule. The study provides SEM images of the exposed sclerotized buccal capsule. This gives more information on the tridents, the sclerotized plate that extends laterally from the buccal capsule, and the narrow isthmus separating the anterior buccal capsule from the posterior. The prevalence, intensity, mean intensity, and mean abundance was 52.91%, 2-38, 12.37 and 6.54, respectively. 18S rDNA fragments were amplified, sequenced, and compared to other camallanid taxa, and 18S data confirmed the identity of the newly obtained sequences (MN396556) as that of P. cyathopharynx, being identical to sequence DQ813445 from Tanzania. This represents the first geographical record of P. cyathopharynx in Kenya.

A new species of Masenia Chatterji, 1933 is described based on material from the intestine of Clarias gariepinus (Burchell) in the Incomati River, Mozambique. The combination of morphological characteristics and analysis of 18S and 28S rDNA sequences delineated the specimens found in the present study as a distinct species. The new form is distinguished from other Masenia spp. in having a large reniform seminal receptacle, a cirrus-sac ending anterior to the ventral sucker, intestinal caeca extending into the hindbody to the level of the posterior testis, and the vitelline fields extending anteriorly to the ventral sucker and posteriorly to the middle of the ovary. Notably, the new form is the only record of African species having a sac-shaped excretory vesicle. Analysis of 28S rDNA sequence data supported its placement in the Cephalogonimidae Looss, 1899. 18S analyses also supported its placement in this family but showed it was not closely related to Masenia bangweulensis (Beverley-Burton, 1962), the sole other African species for which genetic data is currently accessible. The total pairwise differences for 18S and 28S sequences showed the new form differing from other cephalogonimids. Thus, both morphological and genetic characteristics indicate that the present form represents a distinct species, here described as Masenia nkomatiensis n. sp. An updated key to African Masenia spp., now five, is provided.

Diplozoidae infects the gills of cyprinid fishes in Africa, Europe, and Asia. Traditionally the hardened internal structures, crucial for identification of diplozoid species, are studied using light microscopy. Recently, the sclerotised haptoral structures of an African diplozoid, Paradiplozoon vaalense, were successfully isolated and visualised using scanning electron microscopy (SEM). In this paper, the haptoral sclerites of three diplozoid species are compared using SEM for the first time. Paradiplozoon ichthyoxanthon and Paradiplozoon vaalense occur on Labeobarbus and Labeo species, respectively, in the Vaal River system, South Africa, while Diplozoon paradoxum is widely-distributed in Europe and Asia, infecting several host species. Diplozoon paradoxum is a well-studied species, as well as being the type species of the family and ideal for inclusion in an exploratory study for comparative purposes. SEM study of D. paradoxum and P. ichthyoxanthon provided valuable information regarding surface morphology of the attachment structures hitherto not observed. Elaborate morphometric study of the haptoral hooks were incorporated, adding 12 point-to-point measurements to current morphometric characteristics. The results were analysed statistically, and significant differences support absolute separation (100.00%) of the three species following discriminant analysis. These point-to-point measurements could also be used for light microscopical study in the future and aid species delimitation within the Diplozoidae., Competing Interests: The authors have declared that no competing interests exist.

A new species of Gyrodactylus von Nordmann, 1832 is described from the gills of Alcolapia grahami, a tilapian fish endemic to Lake Magadi. This alkaline soda lake in the Rift Valley in Kenya is an extreme environment with pH as high as 11, temperatures up to 42 °C, and diurnal fluctuation between hyperoxia and virtual anoxia. Nevertheless, gyrodactylid monogeneans able to survive these hostile conditions were detected from the gills the Magadi tilapia. The worms were studied using light microscopy, isolated sclerites observed using scanning electron microscopy, and molecular techniques used to genetically characterize the specimens. The gyrodactylid was described as Gyrodactylus magadiensis n. sp. and could be distinguished from other Gyrodactylus species infecting African cichlid fish based on the comparatively long and narrow hamuli, a ventral bar with small rounded anterolateral processes and a tongue-shaped posterior membrane, and marginal hooks with slender sickles which are angled forward, a trapezoid to square toe, rounded heel, a long bridge prior to reaching marginal sickle shaft, and a long lateral edge of the toe. The species is also distinct from all other Gyrodactylus taxa based on the ITS region of rDNA (ITS1-5.8s-ITS2), strongly supporting the designation of a new species. These findings represent the second record of Gyrodactylus from Kenya, with the description of G. magadiensis bringing the total number of Gyrodactylus species described from African cichlids to 18., (© Q.M. Dos Santos et al., published by EDP Sciences, 2019.)

The analysis of stable isotopes of carbon and nitrogen has been used as a fingerprint for understanding the trophic interactions of organisms. Most of these studies have been applied to free-living organisms, while parasites have largely been neglected. Studies dealing with parasites so far have assessed the carbon and nitrogen signatures in endoparasites or ectoparasites of different hosts, without showing general trends concerning the nutritional relationships within host-parasite associations. Moreover, in most cases such systems involved a single host and parasite species. The present study is therefore the first to detail the trophic interactions of a freshwater monogenean-host model using δ13C and δ15N, where a single monogenean species infects two distinctly different hosts. Host fishes, Labeobarbus aeneus and Labeobarbus kimberleyensis from the Vaal Dam, South Africa, were assessed for the monogenean parasite Paradiplozoon ichthyoxanthon, individuals of which were removed from the gills of the hosts. The parasites and host muscle samples were analysed for signatures of δ13C and δ15N using an elemental analyser connected to an isotope ratio mass spectrometer. Host fish appear to use partly different food sources, with L. aeneus having slightly elevated δ13C signatures compared to L. kimberleyensis, and showed only small differences with regard to their nitrogen signatures, suggesting that both species range on the same trophic level. Carbon and nitrogen signatures in P. ichthyoxanthon showed that the parasites mirrored the small differences in dietary carbon sources of the host but, according to δ15N signatures, the parasite ranged on a higher trophic level than the hosts. This relationship resembles predator-prey relationships and therefore suggests that P. ichthyoxanthon might act as a micropredator, similar to blood-sucking arthropods such as mites and fleas.

The sclerotized structures of monogeneans have traditionally been studied by light microscopy and different staining techniques. Recently, enzymatic digestion followed by scanning electron microscopy (SEM) has enabled the examination of structural details not visible with light microscopy. In order to obtain better, and more accurate, morphological information on sclerotized structures not affected by mounting medium or cover slip pressure, the sclerites of Cichlidogyrus philander Douëllou, 1993 (Monogenea, Ancyrocephalidae), collected from Pseudocrenilabrus philander (Weber, 1897), were redescribed using SEM. Parasites were collected from Padda Dam, Gauteng, South Africa and soft tissue was digested to release the sclerotized structures. The digested tissue also provided sufficient genetic material for molecular characterization of this species. Cichlidogyrus philander is characterised by a penis with a sharp, curved, lateral termination, an accessory piece with a hook-like extremity that may appear forked terminally, and lack of a visible vagina. The transverse bars have concave and convex surfaces with ribs on the concave surface. The dorsal bar bears fenestrations at the base of the auricles and the ventral and dorsal gripi are dissimilar. Furthermore, the large first pair of uncinuli shows lateral wings on the left side of the base. On top of this wing, a ball-like structure with a small fenestration is visible. Genetic characters derived from the 28S rDNA, the COI mitochondrial DNA and ITS1 rDNA regions distinguish C. philander from all other Cichlidogyrus sequenced species., (© P.C. Igeh et al., published by EDP Sciences, 2017.)

Classification of most monogeneans is primarily based on size, shape, and arrangement of haptoral sclerites. These structures are often obscured or misinterpreted when studied using light microscopy, leading to confusion regarding defining characters. Scanning electron microscopy (SEM) has predominantly been used to study haptoral sclerites in smaller monogeneans, focusing on hooks and anchors. In the Diplozoidae, SEM has not been used to study haptoral sclerites. Using new and modified techniques, the sclerites of diplozoids collected in South Africa were successfully studied using SEM. The digestion buffer from a DNA extraction kit was used to digest the surrounding tissue, and Poly-L-lysine-coated and concavity slides were employed to limit the movement and loss of sclerites, with the latter being more user-friendly. In addition to the success of visualizing the sclerites using SEM, the digested tissue from as little as half of the haptor provided viable genetic material for molecular characterization. From the results presented here, the study of the sclerites of larger monogeneans using SEM, including those bearing clamps, is a viable possibility for future research. Also, this method may be beneficial for the study of other, non-haptoral sclerites, such as cirri in other families of monogeneans. During this study, Labeo capensis was noted as a valid host of Paradiplozoon vaalense in a region of the Vaal River where the type host, Labeo umbratus, appears to be absent.

An unidentified monogenean diplozoid species was collected from the gills of moggel in the Vaal River and Vaal Dam, South Africa. Specimens were removed from gills of the hosts and observed using light and electron microscopy to compare these diplozoids with known species. The second internal transcribed spacer (ITS2) of the ribosomal gene was amplified, sequenced and compared to that of other diplozoid taxa. Morphological species delimitation was used to determine the identity of these diplozoids, but they did not match the description of any diplozoid taxa. This species is recognized by the specific size of the hooks, number of plicae in posterior and trapezoid anterior projection of the median sclerite connecting to the clamp jaws via a single sclerite, occasionally with two small additional sclerites. Genetic characteristics based on sequence data from the ITS2 region also distinguish this taxon from all other diplozoid taxa. This South African diplozoid grouped in the same clade as Paradiplozoon ichthyoxanthon Avenant-Oldewage, 2013. Data clearly indicate that diplozoids collected from moggel represent a new, distinct taxon of Paradiplozoon Akhmerov, 1974 and are described here as Paradiplozoon vaalense n. sp.