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Gyrodactylus molweni sp. n. is described from the body surface and fins of the South African mullet, Chelon richardsonii (Smith, 1846) collected from Table Bay Harbour, Cape Town and is compared to five other Gyrodactylus species described from grey mullets globally namely G. zhukovi Ling, 1963 and G. mugili Zhukov, 1970 from Planiliza haematocheila (Temminck and Schlegel, 1845); G. mugelus Rawson, 1973 from Mugil cephalus L.; G. curemae Conroy and Conroy, 1985 from Mugil curema Valenciennes, 1836 and G. xiamenensis Zang,Yang and Liu, 2001 from Planiliza macrolepis (Smith, 1846). Morphologically, G. molweni sp. n. has prominent ventral bar processes that near cover the hamulus roots, marginal sickles with large rhomboid heels, slender shafts and fine points that extend beyond the sickle toes. Gyrodactylus molweni sp. n. can, however, be readily differentiated: G. mugili and G. xiamenensis have ventral bars with small ventral processes; G. zhukovi has marginal hooks sickles with slender shafts and proportionately short points and open-faced blades; G. mugelus possesses marginal hook sickles with deep, rounded heels, forward slanting shafts and an angular, square line to the inner face of the blades. Although the length of the marginal hooks of G. curemae are similar to G. molweni sp. n., their hamuli are double the size. A GenBank BlastN search with the 931 bp sequence covering ITS1, 5.8S and ITS2 gave no close hits; the nearest species for which sequences are available is G. nipponensis Ogawa and Egusa, 1978 (identity 96.56%, 899/931 bp). The proposal of G. molweni sp. n. as a new species, therefore, is well supported by both the molecular and morphological analyses presented herein. This Gyrodactylus species is the first to be described from C. richardsonii and only the second Gyrodactylus species to be described from the marine environment off the African continent.

Although Nile tilapia (Oreochromis niloticus) is a well-established aquaculture species globally, there are a limited number of commercial vaccines available or are used for this species. The majority of diseases affecting farmed tilapia are bacterial, with antibiotics frequently used to treat fish. The current study was performed to optimise the use of mucosal vaccines for tilapia by adapting an existing bacterin vaccine against Francisella noatunensis subsp. orientalis (Fno) as a proof of concept. This vaccine has previously provided excellent protection by injection, however, the preference for tilapia farmers would be to vaccinate fish by immersion or orally, due to the lower cost and ease of application. These vaccination routes, however, are often less efficacious probably due to the lack of adjuvants in immersion and oral vaccines. The aims of this study, therefore, were to optimise the formulation and dose of the Fno vaccine with mucosal adjuvants for oral and immersion delivery. Tilapia fry (av. 6 g) were given three concentrations (high, medium, low; i.e. 1×109, 1×108 and 1×107 CFU mL-1) of antigen combined with the oral adjuvant by oral gavage, to optimise the dose needed to induce an immune response to Fno, and the immune response obtained compared with fish vaccinated by immersion (with and without an immersion adjuvant). Fry were boosted by the same route at 420 degree days (DD), and samples (serum, mucus ) taken at 840 DD for specific antibody responses measured by ELISA and western blotting. Specific IgM titres were significantly elevated in serum and mucus of fish given the high dose adjuvanted vaccine by gavage. In addition, by western blotting with serum, a significant immunogenic reaction was evident between 20 and 37 kDa in the fish given the high dose oral vaccine by gavage. As protection against Fno provided by the injection vaccine was correlated with specific antibody responses these findings suggest the oral vaccine also has potential to provide protection. Further studies are needed to optimise delivery of the vaccine via feed.

The African continent has a rich diversity of fish and amphibians in its inland water systems that serve as hosts for monogeneans of seven genera of the Gyrodactylidae van Beneden et Hesse, 1832. In August 2011, eight gyrodactylid parasites were collected from the gills of two specimens of bulldog, Marcusenius macrolepidotus (Peters), from Lake Kariba, Zimbabwe. Morphometric evaluation and sequencing of 18S rDNA confirmed that the specimens represented a species of a new viviparous genus, Tresuncinidactylus wilmienae gen. et sp. n. The attachment apparatus consists of a single pair of large slender hamuli with prominently flattened roots that are connected by a simple, narrow dorsal bar. The ventral bar is small and possesses a thin lingulate membrane but no evident anterolateral processes. There are 16 marginal hooks of one morphological type, but of three different sizes, with large falculate sickles that are proportionaly equal in length to the length of their handles. The two largest pairs of marginal hooks are positioned closest to the opisthaptoral peduncle, the neighbouring two pairs of medium-sized marginal hook sickles are situated along the lateral margins of the opisthaptor. Four pairs of smallest marginal hooks are positioned along the posterior margin of the opisthaptor. The male copulatory organ consists of a muscular pouch armed with approximately 30 gracile spines. Phylogenetic analyses of partial sequences of the 18S rDNA using Maximum Likelihood and Bayesian Inference placed the new genus within the lineage of solely African genera and suggests Afrogyrodactylus Paperna, 1968, Citharodactylus Přikrylová, Shinn et Paladini, 2017 and Mormyrogyrodactylus Luus-Powell, Mashego et Khalil, 2003 as genera most closely related to the new genus.

Ornamental harlequin shrimp, Hymenocera picta, are commonly maintained on live comet sea stars, Linckia multifora. In Thailand, both species are commonly collected from the wild, raising concerns regarding the sustainability of such practices. As a step toward the sustainable aquaculture of both, methods of their culture and nutrition were investigated. Under captive conditions, harlequin shrimp readily predate, and can be maintained upon the astropectinid sand star Astropecten indicus as an alternative live feed during periods when comet sea stars are unavailable. Wild A. indicus subsequently spawned multiple times shortly after their collection; the eggs (300 μm diameter) were transferred to static aquaria. Following the appearance of planktonic bipinnaria, larval sea stars were fed a 50:50 Chaetoceros calcitrans and Isochrysis galbana diet. Eleven days post‐transfer, brachiolaria stages began to settle; stages were then fed concentrated I. galbana. When specimens measured 1–2 mm in diameter, they were transferred onto an in‐house formulated Amphiprion diet (>50% protein, >16% lipid). Sea stars were graded regularly; they matured and spawned after 6 months. Populations were maintained for more than three successive generations, demonstrating their ready culture under captive conditions, representing the first harvestable aquaculture of a sea star as a step toward supporting the sustainable culture of a primary, marine species.

Approximately 10% of Late Jurassic (Tithonian) horseshoe crabs collected from the Kcynia Formation in the Owadow-Brzezinki Quarry, Central Poland, display microborings covering the entire carapace of specimens. Detailed examination of the surrounding sediment indicates the occurrence of short-term fluctuations in the oxygenation level of bottom waters and their salinities. The identified palynomorph assemblage from the sediment suggests pathogenic algal blooms as the probable cause for mass mortality. Anoxic conditions resulting from algal blooms in restricted environments facilitated fungal infection evidenced by the damage (microborings) caused by the hyphae on the surface of the exoskeletons. Associated biochemical factors contributed to the excellent preservation of diversified fauna with soft tissues.

Isolates of Vibrio parahaemolyticus (VpAHPND) that carry a plasmid encoding two Pir-like toxins cause acute hepatopancreatic necrosis disease (AHPND), a disease that has caused devastating economic losses to the shrimp industry, particularly in Asia. However, lower prevalence of AHPND infection has been associated with farms that operate with biofloc or lower salinity culture water. Therefore, the aim of this present study was to investigate the effects of biofloc and Nile tilapia (Oreochromis niloticus)-conditioned water prepared at different culture water salinities on survival of whiteleg shrimp (Penaeus vannamei) bath-challenged experimentally with VpAHPND. First, groups of shrimp were bath-challenged with VpAHPND in clear 15 ppt seawater (CW) or in the presence of a pre-cultured biofloc at 25%, 50% and 100% (v/v). Survival during 96 h post-challenge was significantly greater in groups cultured in 50% and 100% biofloc (p

The maturation and reproduction of Pacific whiteleg shrimp, Penaeus vannamei, through the practice of unilateral eyestalk ablation though common is an animal welfare concern. This study assessed the resilience of offspring from non-ablated P. vannamei when challenged with an isolate of Vibrio parahaemolyticus (Vp) causing acute hepatopancreatic necrosis disease (VpAHPND), and with white spot syndrome virus (WSSV). VpAHPND and WSSV challenges were conducted using PL and juveniles under controlled conditions, with both trials using four groups (i.e. shrimp from either ablated or non-ablated females and then either challenged with the pathogen or not challenged). For the VpAHPND challenge, ten replicate 20 L tanks (five replicates for each population) each containing 100 PL 17 (average weight 14 mg) in 15 ppt, 29.05 ± 0.13 °C water were challenged with 2 mL of 2.0 × 108 CFU mL−1 culture of V. parahaemolyticus. A further ten replicate tanks (five per population) served as the corresponding non-challenged controls. The shrimp mortalities were assessed every 3 h over the following 96 h. For the WSSV challenge, individual 1.4 g (average weight) shrimp (50 individuals per population) were housed in 1 L tanks and fed 0.1 g WSSV infected tissue (av. 2.02 × 109 WSSV). A further 50 shrimp per population served as non-challenged controls. The shrimp were maintained at 15 ppt, 26.3 ± 0.71 °C water and assessed every 3 h post-infection over the subsequent 168 h and mortalities at each time point noted. Postlarvae from non-ablated females had significantly (p = 2.4E-23) better survival (70.4%) than those from ablated females (38.8%) at 96 h post-challenge with VpAHPND. Both challenged populations had significantly (p ≤1.3E-36) lower survival than the control groups. The survival of the juveniles from non-ablated females (62%) at 168 h post-infection with WSSV was not significantly higher than that of the juveniles from ablated female (48%) although the difference was significantly different at 65 to 75 h. Both challenged populations also had significantly (p ≤1.0E-5) lower survival rates than the control groups. The study demonstrates that postlarvae and juveniles from non-ablated females are more resilient to typical pathogens (VpAHPND and WSSV) and may show higher survival rates during a disease outbreak.

The occurrence of the endocrine disruptors bisphenol-A (BPA) and 17β-estradiol (E2) in cultured populations of green mussel (Perna viridis) and water samples collected from selected fresh and marine coastal environments along the eastern coast of Thailand were investigated. Analysis found high levels of BPA in mussel tissues that correlated with levels found in coastal (maximum 37.13 ng/L) and freshwater (50.7 ng/L) sites situated near industrial and densely populated areas. By comparison, high levels of E2 (62.99 ± 5.03 ng/L) were found in freshwater sites near to urban areas. Higher concentrations of BPA and E2 were found in mature green mussels (>6 mo. old; 6.40 ± 0.52 cm shell length) than levels determined in juveniles (

Harlequin shrimp, Hymenocera picta , are commonly maintained on a diet of comet seastars, Linckia multifora , however, difficulties in sourcing a ready supply throughout the year, represent limitations to their sole use within commercial scale production. In a two-step approach, to address their limited availability, firstly the acceptability of several alternative prey items ( i.e. Astropecten indicus , Luidia maculata , Culcita novaeguineae and Holothuria leucospilota ) were assessed and then secondly, in-depth studies were conducted with the most acceptable species identified from the first step. In the first trial, the feeding responses, i.e. time taken to attack prey, by 120-day old, pre-starved shrimp were assessed. Shrimp quickly overturned specimens of A. indicus and began feeding within 5 min, while specimens of L. maculata and L. multifora were carefully assessed before a limb was selected and excised. As the seasonal availability of Linckia is limited, the performance of shrimp fed less frequently was explored. The second trial, therefore, investigated the growth, survival and reproductive capacity of shrimp fed different regimes of live L. multifora over a 5-month period compared to shrimp fed a favourable alternative prey identified from the first experiment, i.e. A. indicus . Shrimp were fed either: 1) live L. multifora daily (LMD); 2) live L. multifora every alternate week (LMW); 3) live A. indicus daily (AID); or, 4) live A. indicus every alternate week (AIW). There was 100% survival of those fed the LMD and LMW diets but 67% in those groups fed AID and AIW respectively; females displayed better growth than males but there were no significant differences ( p A. indicus appears to represent a favourable alternative live feed to the use of L. multifora that can be readily maintained within aquaria. During periods when the availability of live L. multifora is limited, a regime of either LMW or AID are appropriate for the maintenance of shrimp, however, minimising the time interval between feeding L. multifora would result in better performance. Statement of relevance “Evaluating alternative live diets for harlequin shrimp”. The study assesses locally available alternative live feeds for the potential commercial-scale aquaculture of harlequin shrimp in Thailand, focusing on the use of Astropecten indicus as an appropriate live feed that can be supplemented when Linckia multifora is not available.

Information relating to the effects of phytic acid (PA), an anti-nutritional factor (ANF) commonly found in plant protein ingredients, on the growth performance, feed conversion ratio (FCR), nutrient utilisation and whole proximate composition in the Malaysian giant freshwater prawn, Macrobrachium rosenbergii, is lacking. Replicate groups of M. rosenbergii (mean initial carapace length of 6.03 ± 0.30 mm; mean initial weight of 0.29 ± 0.02 g; n = 20 per replicate group) were fed graded levels of PA for 140 days. The basal diet, to which different levels of PA were added to obtain 0.26 (control), 6.48, 11.28, 16.53, 21.45 and 26.16 g PA kg− 1, contained fishmeal, soy protein concentrate and wheat meal. Terminal sampling indicated that the growth performance, FCR and survival did not differ significantly between the groups receiving the different inclusions of PA within their diets. The apparent protein, lipid and energy utilisation responded negatively, decreasing significantly (p 0.05) on the M. rosenbergii reared under the experimental conditions that were employed here.

Francisellosis, induced by Francisella noatunensis subsp. orientalis (Fno), is an emerging bacterial disease representing a major threat to the global tilapia industry. There are no commercialised vaccines presently available against francisellosis for use in farmed tilapia, and the only available therapeutic practices used in the field are either the prolonged use of antibiotics or increasing water temperature. Recently, an autogenous whole cell-adjuvanted injectable vaccine was developed that gave 100% relative percent survival (RPS) in tilapia challenged with a homologous isolate of Fno. In this study, we evaluated the efficacy of this vaccine against challenge with heterologous Fno isolates. Healthy Nile tilapia, Oreochromis niloticus (∼15 g) were injected intraperitoneally (i.p.) with the vaccine, adjuvant-alone or phosphate buffer saline (PBS) followed by an i.p. challenge with three Fno isolates from geographically distinct locations. The vaccine provided significant protection in all groups of vaccinated tilapia, with a significantly higher RPS of 82.3% obtained against homologous challenge, compared to 69.8% and 65.9% with the heterologous challenges. Protection correlated with significantly higher specific antibody responses, and western blot analysis demonstrated cross-isolate antigenicity with fish sera post-vaccination and post-challenge. Moreover, a significantly lower bacterial burden was detected by qPCR in conjunction with significantly greater expression of IgM, IL-1 β, TNF-α and MHCII, 72 h post-vaccination (hpv) in spleen samples from vaccinated tilapia compared to fish injected with adjuvant-alone and PBS. The Fno vaccine described in this study may provide a starting point for development a broad-spectrum highly protective vaccine against francisellosis in tilapia.

The presence of anti-nutritional factors such as phytic acid (PA) in a number of potentially useful plant ingredients has been a major impediment to their use as replacements for fishmeal in aquafeeds. This study builds on an earlier studying investigating the growth performance and nutrient utilisation in the juvenile Malaysian giant river prawn, Macrobrachium rosenbergii exploring the effects and interactions of dietary PA with minerals on growth (somatic tissue). Additionally, the study set out to determine the changes in whole-body mineral composition and also on muscle tissues and the carapace, when different levels of PA were included within the diet. The hypothesis under test was that PA, as a mineral-binding agent by chelating di- and trivalent cations inhibits mineral availability. To explore this, effects of graded levels of PA (i.e. 0.26–control, 6.48, 11.28, 16.53, 21.45 and 26.16 g PA kg−1) on the moult frequency and mineral availability in juvenile M. rosenbergii (mean initial carapace length of 6.22 ± 0.52 mm; mean initial weight of 0.20 ± 0.01 g; n = 20 per replicate) fed over a period of 140 days were determined. The levels of PA assessed in this feed trial had no major detrimental effects on moult frequency. Negative effects (p, This project was supported by the Ministry of Higher Education Malaysia and University Malaysia Terengganu (UMT) as part of a PhD programme of study.

Background Goodeid topminnows are live-bearing fishes endemic to the Mexican Highlands (Mesa Central, MC). Unfortunately, in the MC, environmental degradation and introduced species have pushed several goodeid species to the brink of extinction. Invasive fishes can introduce exotic parasites, and the most abundant goodeid, blackfin goodea Goodea atripinnis Jordan, is parasitised by six exotic helminths. Poeciliids are widely dispersed invasive fishes, which exert negative ecological effects on goodeids. Poeciliids host several species of the monogenean genus Gyrodactylus von Nordmann, 1832, including pathogenic, invasive parasites. Here, we looked for evidence of Gyrodactylus species switching hosts from poeciliids to goodeids. Methods Fish were collected in rivers draining the MC into both sides of the continental divide. Hosts were screened for gyrodactylid parasites in localities where G. atripinnis and poeciliids occurred sympatrically. Gyrodactylus specimens were characterised morphologically (attachment apparatus) and molecularly (internal transcribed spacer region, ITS). A Bayesian phylogenetic tree using ITS sequences established relationships between gyrodactylids collected from goodeid fishes and those from parasites infecting poeciliids. Results Gyrodactylids were collected from G. atripinnis in six localities on both sides of the watershed where exotic poeciliids occurred sympatrically. Morphological and molecular analyses indicated the presence of four undescribed species of Gyrodactylus infecting this goodeid host. Gyrodactylus tomahuac n. sp., the most abundant and geographically widespread species, is described here. The other three Gyrodactylus spp. are not described, but their ITS sequences are used as molecular data presented here, are the only available for gyrodactylids infecting goodeid fishes. Morphological and molecular data suggest that two distinct groups of gyrodactylids infect goodeids, one of which shares a common ancestor with gyrodactylids parasitizing poeciliids. Conclusions No evidence was found of gyrodactylids switching hosts from invasive poeciliids to endemic goodeids, nor vice versa. Moreover, considering that G. atripinnis is known to host both Gyrodactylus lamothei Mendoza-Palmero, Sereno-Uribe & Salgado-Maldonado, 2009 and Gyrodactylus mexicanus Mendoza-Palmero, Sereno-Uribe & Salgado-Maldonado, 2009, with the addition of G. tomahuac n. sp. and the three undescribed Gyrodactylus spp. reported, at least six gyrodactylids may infect this host. This would make monogeneans the second most abundant parasite group infecting G. atripinnis, which to date is known to harbour 22 helminth species: nine digeneans, five nematodes, four cestodes, three monogeneans and one acanthocephalan.

A new genus and species of monogenean belonging to the Gyrodactylidae, Citharodactylus gagei n. gen. et n. sp. (Plathyhelminthes, Monogenea), is described from the gills of the moon fish, Citharinus citharus (Geoffroy Saint-Hilaire), a characiform fish collected from Lake Turkana in northern Kenya. The new viviparous genus can be readily distinguished from the six other gyrodactylid genera recorded from Africa and from the other viviparous genera within the Gyrodactylidae based on the morphology of the male copulatory organ (MCO), which consists of a muscular ovate organ with an opening onto the tegument through which the narrow tapered end of a sclerotised curved cone-shaped structure protrudes. The tegumental opening of the MCO is surrounded by a collar of short spines. Sequencing of the nuclear ribosomal DNA internal transcribed spacers 1 and 2, the 5.8S and the 18S rDNA genes and a comparison with the gyrodactylid species listed in GenBank confirmed the specimens are unique and do not match with any existing entry. When phylogenies for each genomic region were conducted (i.e. 0.064 gamma-corrected pairwise genetic distance based on a alignment of 1750bp of the 1857bp long 18S rDNA gene), the most similar match was that of Afrogyrodactylus sp. [=A. girgifae (Folia Parasitol 61:529–536, 2014)] from Brycinus nurse (Rüppell). The proposed name of the new parasite is Citharodactylus n. gen. which represents the seventh gyrodactylid genus to be found in Africa and the 25th viviparous genus and the 32nd genus to be added to the Gyrodactylidae.

With growing world trends in the consumption of raw and undercooked aquatic products, anisakiasis, resulting from infection by anisakid nematodes, currently affects over 2000 people per annum worldwide. In response to new EC regulatory requirements regarding the processing of farmed fish to reduce the risk of nematode infections, the aim of this study was to provide evidence of the prevalence and intensity of anisakids in relevant Scottish mariculture species and to identify potential probability of nematode infection by analysing the current farming practices for these species. A sample of 225 marine rainbow trout, Oncorhynchus mykiss , and 150 Atlantic halibut, Hippoglossus hippoglossus , was obtained from three and two farms, respectively, on the West Coast of Scotland. A further 12 Atlantic halibut were obtained from wild fisheries. Fish flesh examined for nematode larvae using standard techniques provided no evidence for the presence of anisakid nematodes in any of the farmed fish sampled. In addition, no food items other than pelleted feed were found in the stomach and intestines of any farmed fish. Sampled wild halibut showed a prevalence of 75% and intensity of 12.75 ± 25.81 of Anisakis simplex although no Pseudoterranova decipiens were found. An analysis of current farm practices for the culture of halibut, rainbow trout and sea trout, Salmo trutta , in Scotland suggests that the probability of infection with anisakids is extremely low. To acquire an infection, a fish must consume infected prey, and as commercial aquaculture in Scotland relies on processed, pelleted feed, the probability of wild infected prey being consumed is very low, particularly since fish are generally fed to satiation. Given the results of this study and evidence from previous studies, it must be concluded that under current farming practices, the risk of contracting anisakiasis from Scottish farmed halibut and rainbow trout is extremely low to negligible. Consequently, they do not pose a significant risk to consumers in terms of the ingestion of these parasites.

In the period 2013-2015, wild dusky grouper, Epinephelus marginatus (Lowe), caught in Libyan coastal waters and ranging in size from 42 to 92 cm in total length, were observed to have distinctive skin lesions of unknown aetiology. Histopathologically, the lesions comprised a multifocal, unilateral or bilateral dermatitis, involving the epidermis, superficial dermis and scale pockets, and sometimes, in severe cases, the hypodermis. Severe lesions had marked epidermal spongiosis progressing to ulceration. Healing was observed in some fish. Bacteria and fungi could be isolated from severe lesions, although they were not seen histopathologically in early-stage lesions. By contrast, metazoan parasite eggs were observed in the dermis and epidermis of some fish with mild and moderate dermatitis. Unidentified gravid digenean trematode parasites carrying similar eggs were also seen within the blood vessels of the deep and superficial dermis. The cause of this distinctive condition, termed dusky grouper dermatitis (DGD), and its potential impact upon already threatened Mediterranean wild dusky grouper populations and upon cultured grouper more widely have yet to be established.

In this study we examined the effect that a Francisella noatunensis (Fno) infection had on hybrid red tilapia (Oreochromis niloticus × Oreochromis mossambicus) subsquently infected with Streptococcus agalactiae. A variety of hemato-immunological parameters (haematocrit, total red blood cell count, mean corpuscular volume, total white blood and differential cell counts, total plasma protein, plasma lysozyme and plasma peroxidase activities, and respiratory burst and phagocytic activities of head-kidney macrophages) were measured in hybrid red tilapia that had been previously exposed to an Fno outbreak in a tilapia grow-out farm. The head-kidneys of these apparently healthy survivors, when checked by PCR were found to be Fno-positive with hemato-immunological parameters that were similar to fish without an a priori infection. The only exception was the percentage lymphocyte count in the peripheral blood, which was slightly, but significantly, lower in the Fno-infected fish, compared to those without the infection. When experimentally infected with S. agalactiae, the Fno-infected fish died more rapidly and at a significantly higher rate than fish without the infection. During the challenge, the hemato-immunological parameters of both groups of fish were very similar, although the Fno-infected fish, challanged with S. agalactiae expressed significantly higher plasma lysozyme and peroxidase activities, and their head kidney macrophages had significantly higher respiratory burst activity compared to non-Fno-infected fish challanged with S. agalactiae. The only two parameters for which Fno-infected fish showed significantly lower expressions than that of their non-infected counterparts were haematocrit and total red blood cell count. The cause of the rapidity and higher rates of mortality observed in the Fno-infected fish when challenged with S. agalactiae is unknown; but it may be due to a reduced erythropoiesis capability within the head-kidney because of the presence of Fno.

The prevalence and intensity of polyopisthocotylean monogeneans on the gills of three commercially important species of sparid caught in Omani coastal waters close to the city port of Muscat were determined and compared. Throughout May 2012 to April 2013, infections on bi-weekly samples of the soldier seabream, Argyrops filamentosus (Valenciennes, 1830), the king soldier seabream, Argyrops spinifer (Forsskål, 1775), and, the silver seabream, Rhabdosargus sabra were evaluated. From a total of 200 specimens (standard length of 26–52 cm), caught by line angling or by traps, at least three species of gill monogenean, namely Omanicotyle [Bivagina] heterospina, Heteromicrocotyla sp. and Microcotyle sp., were commonly encountered. Silver bream, which was infected by all three monogeneans, bore the highest infections (100% prevalence; mean intensity of 20.14 ± 0.92 parasites fish-1), whilst the soldier bream, which was infected only by O. heterospina had the lowest levels of infection (of the three sparids with 63.8% prevalence; mean intensity 5.8 ± 0.17 parasites fish-1). Comments on the distribution of monogeneans on each host are provided but to what extent this is influenced by water current speeds passing through the buccal and opercular cavities, gill morphology, parasite size, and / or the morphology and efficiency of the parasite’s attachment apparatus requires establishing and forms the basis of ongoing investigations.

This paper describes a study in which environmental manipulation of salmon swimming depth was tested in an attempt to reduce farm infection of Atlantic salmon, Salmo salar by the salmon louse, Lepeophtheirus salmonis. The effects of submerged artificial lighting (positioned at 10 m depth) in combination with submerged feeding (delivered at 5 m depth) were tested with respect to salmon swimming depth and sea lice infection, following the hypothesis that L. salmonis infection in a commercial salmon population is reduced when exposed to deep lighting and feeding. This is based on two assumptions, firstly that planktonic L. salmonis larvae principally remain in surface waters (top 4 m) and secondly, that deep lighting and feeding attract salmon to deeper water depths. Results from commercial scale trials confirmed that salmon swimming behaviour is altered under submerged feeding conditions with fish attracted to the feeding corridor during the feeding process. When the fish reached satiation or feeding ceased, they returned to the surface waters during the day. Submerged lighting attracted the fish to the illuminated water depths during the night. During the day, natural light overruled these effects to some extent. The number of L. salmonis on fish exposed to deep submerged lighting was significantly lower than the number of lice found on salmon in cages with surface lighting during the summer months. Submerged feeding showed no advantage over surface feeding with respect to the number of L. salmonis found in these trials. The results of the study suggest that swimming depth manipulation can be used at a commercial scale to reduce salmon lice burdens on Atlantic salmon stocks.

BACKGROUND: Sea lice infection is the most expensive disease factor for Atlantic salmon sea-cage farming. For triploid salmon tobeacceptedasacommercialpossibility,investigationofsusceptibilityoftriploidsalmontosealiceinfectionisafundamental milestone. The susceptibility of diploid and triploid salmon to infection with Lepeophtheirus salmonis was examined in a tank trial in Scotland, a tank trial in Norway and a cage trial in Scotland. RESULTS: Following a single infection challenge, results indicated a significant correlation betweenfish size and the number of attached sea lice. Triploid fish were larger than diploids at the smolt stage. In the tank trials, no difference was found between infection levels on diploids and triploids after a single infection challenge. The tank trial in Scotland continued with a second infection challenge of the same fish, which also showed no infection differences between ploidies. A borderline correlation between first infection and re-infection intensity was found for PIT-tagged diploid salmon examined after each challenge. No significant difference in louse infection between diploid and triploid salmon (∼2kg) was found in the cage trial undertaken under commercial conditions. CONCLUSION: This study concludes that triploid Atlantic salmon are not more susceptible to sea louse infection than diploid fish. c � 2013 Society of Chemical Industry

Gill disorders have emerged in recent years as a significant problem in the production of marine-stage Atlantic salmon Salmo salar L. The multi-aetiological condition 'proliferative gill inflammation' (PGI) has been reported to cause heavy losses in western Norway, yet reports of Scottish cases of the disease have remained anecdotal. In the present study, histopathological material from a marine production site in the Scottish Highlands experiencing mortalities due to a seasonal gill disease with proliferative-type pathology was examined using light microscopy, special staining techniques and transmission electron microscopy (TEM). The microsporidian Desmozoon lepeophtherii Freeman et Sommerville, 2009 (syn. Paranucleospora theridion) was identified by staining using a Gram Twort method and TEM associated with distinctive proliferative and necrotic pathology confined to the interlamellar Malpighian cell areas of the primary filaments. Epitheliocystis was not a feature of the gill pathology observed. It is believed this is the first report of D. lepeophtherii being identified associated with pathology in a Scottish gill disease case, and supports anecdotal reports that a disease at least partly synonymous with PGI as described by Norwegian researchers is present in Scottish aquaculture.

Gyrodactylus salaris (Monogenea, Platyhelminthes) is a notifiable freshwater pathogen responsible for causing catastrophic damage to wild Atlantic salmon stocks, most notably in Norway. In some strains of Baltic salmon (e.g., from the river Neva) however, the impact is greatly reduced due to some form of innate resistance that regulates parasite numbers, resulting in fewer host mortalities. Gyrodactylus salaris is known from 17 European states; its status in a further 35 states remains unknown; the UK, the Republic of Ireland and certain watersheds in Finland are free of the parasite. Thus, the parasite poses a serious threat if it emerges in Atlantic salmon rearing regions throughout Europe. At present, infections are generally controlled via extreme measures such as the treatment of entire river catchments with the biocide rotenone, in order to remove all hosts, before restocking with the original genetic stock. The use of rotenone in this way in EU countries is unlikely as it would be in contravention of the Water Framework Directive. Not only are such treatments economically and environmentally costly, they also eradicate the potential for any host/parasite evolutionary process to occur. Based on previous studies, UK salmon stocks have been shown to be highly susceptible to infection, analogous to Norwegian stocks. The present study investigates the impact of a G. salaris outbreak within a naïve salmon population in order to determine long-term consequences of infection and the likelihood of coexistence. Simulation of the salmon/ G. salaris system was carried out via a deterministic mathematical modelling approach to examine the dynamics of host-pathogen interactions. Results indicated that in order for highly susceptible Atlantic strains to evolve a resistance, both a moderate-strong deceleratingly costly trade-off on birth rate and a lower overall cost of the immune response are required. The present study provides insights into the potential long term impact of G. salaris if introduced into G. salaris-free territories and suggests that in the absence of external controls salmon populations are likely to recover to high densities nearing 90% of that observed pre-infection.

A histochemical and ultrastructural investigation of the cellular inflammatory response within the intestines of tench Tinca tinca L. naturally infected with the caryophyllidean cestode Monobothrium wageneri was conducted and the data obtained compared to those in uninfected counterparts. Cestode infections within the intestines were evident through the appearance of raised inflammatory swellings induced by the deep penetration of their scolices into the intestinal wall. Cestodes typically attached in tight clusters, inducing a massive hyperplastic granulocyte response of mast cells and neutrophils, which were significantly more numerous (P < 0·01) in the intestines of infected (n = 14) than of uninfected (n = 9) tench. Neutrophils were more abundant than mast cells (P < 0·01) in host tissues in close proximity to the parasite tegument. In transmission electron microscopy sections, mast cells and neutrophils were frequently observed in contact with or inside capillaries, and in close proximity to the cestode. Degranulation of both cell types was seen in the submucosa and lamina muscularis, notably in the immediate tissues surrounding the scolex of M. wageneri. No tegumental secretions were seen at the host-parasite interface. Occasional rodlet cells were encountered in the submucosa of infected fish.

Saprolegnia infections can account for the significant loss of salmonid eggs and adults in breeding condition and although there are a number of chemical agents available to control infections in hatcheries, treatment is difficult and there are reservations regarding their efficacy, prompting a search for suitable replacements. Here, the efficacy of 24 crude plant extracts and 3 bioflavonoids on the growth of Saprolegnia australis were assessed using an in vitro agar diffusion method against a set of synthetic chemotherapeutants commonly used within the aquaculture industry. The 12 best extracts inhibiting growth at ≤ 100 ppm, were then added to cultures of S . australis in a GP broth and the daily growth was monitored spectrophotometrically over a 7-day period. All 12 plant extracts reduced growth, however, only Atractylodes macrocephala , Zingiber officinale seed, Chrysanthemum and Yucca were as effective as 10 ppm malachite green in slowing growth. A subsequent trial, where doses of the plant extract were given at 72 and 120 h post-inoculation, found that Rumex obtusifolius , Sophora flavescens , Echinacea and Z . officinale were the most effective compounds impacting growth. The study demonstrates that certain plant extracts impact on the growth dynamics of S . australis but further research is required to assess their performance in vivo.

Ichthyophthirius multifiliis Fouquet, 1876 infections on intensively reared fish stocks can increase rapidly, which if left unmanaged, can result in the heavy loss of stock. The present study explores the efficacy of long duration, low dose (1, 2 and 5 mg L(-1)) treatments of bronopol (marketed as Pyceze™, Novartis Ltd.) in reducing the number of trophonts establishing on juvenile Oncorhynchus mykiss held under small scale culture conditions. The effect of bronopol on the colonisation success of infective theronts was also investigated by adding 2 mg L(-1) bronopol to the water prior and during the infection process. The number of parasites surviving on fish treated this way was compared to groups of fish that only received treatment after infection had occurred. The effect of bronopol on exiting trophonts throughout their external development to the point of theront release was also assessed through the delivery of 1 mg L(-1), 2 mg L(-1) and 5 mg L(-1) bronopol for up to 27 days consecutively (days 9-36 post-infection). The trial showed that a nominal dose of 2 mg L(-1) bronopol administered prior to infection significantly reduced the number of theronts surviving in the water column at the time of the initial challenge by 35-40% (P

Pyceze™ (Novartis Animal Vaccines Ltd.) is licensed as a veterinary medicine to treat fungal infections in salmon, trout and their eggs. The active ingredient is bronopol, which due to its broad-spectrum activity has the potential to be an effective treatment against other important aquatic pathogens. In this study the efficacy of bronopol against Ichthyophthirius multifiliis was tested both in vitro and in vivo. In vitro trials demonstrated a 30 min exposure to 100 mg L(-1) bronopol killed 51.7% of the infective theronts. In vitro exposure of the protomonts to bronopol (0, 20, 50 and 100 mg L(-1)) for 30 min was observed to kill 0%, 76.2%, 97.2% and 100% respectively. Protomonts surviving treatment, demonstrated delayed development with the time taken from protomont until the release of theronts ranging from 28.3h for 0 mg L(-1) exposure, to 70 h for parasites in 20 and 50 mg L(-1) exposure groups. These concentrations also caused asymmetric cell division of the encysted tomonts. Exposure of encysted tomonts (min. 8 cell stage) to 100 mg L(-1) bronopol for 30 min, killed 50% within this period, with the remainder dying within the subsequent 42 h post exposure. Lower doses of bronopol were less effective in killing encysted tomonts than the higher doses (3.3% of parasites were killed in 20 mg L(-1); 10% in 50 mg L(-1)), but they still delayed theront release significantly (25.7 h for 0 mg L(-1) to 46.2h for parasites exposed to 20-50 mg L(-1)). Long, low dose (1 mg L(-1)) exposure to bronopol was also efficacious against theronts. Survival after 12h was 29% (c.f. 100% in control parasites), and

Marine aquaculture relies on coastal habitats that will be affected by climate change. This review assesses current knowledge of the threats and opportunities of climate change for aquaculture in the UK and Ireland, focusing on the most commonly farmed species, blue mussels (Mytilus edulis) and Atlantic salmon (Salmo salar). There is sparse evidence to indicate that climate change is affecting aquaculture in the UK and Ireland. Impacts to date have been difficult to discern from natural environmental variability, and the pace of technological development in aquaculture overshadows effects of climatic change. However, this review of broader aquaculture literature and the likely effects of climate change suggests that over the next century, climate change has the potential to directly impact the industry. Impacts are related to the industry's dependence on the marine environment for suitable biophysical conditions. For instance, changes in the frequency and strength of storms pose a risk to infrastructure, such as salmon cages. Sea-level rise will shift shoreline morphology, reducing the areal extent of some habitats that are suitable for the industry. Changes in rainfall patterns will increase the turbidity and nutrient loading of rivers, potentially triggering harmful algal blooms and negatively affecting bivalve farming. In addition, ocean acidification may disrupt the early developmental stages of shellfish. Some of the most damaging but least predictable effects of climate change relate to the emergence, translocation and virulence of diseases, parasites and pathogens, although parasites and diseases in finfish aquaculture may be controlled through intervention. The spread of nuisance and non-native species is also potentially damaging. Rising temperatures may create the opportunity to rear warmer water species in the UK and Ireland. Market forces, rather than technical feasibility, are likely to determine whether existing farmed species are displaced by new ones.

The last detailed morphological descriptions of the juvenile stages of the parasitic copepod Lernaeocera branchialis (L., 1767) were written more than 70 yr ago, since which time both taxonomic nomenclature and available imaging technologies have changed substantially. In this paper a re-description of the free-swimming juvenile stages of L. branchialis is presented using a combination of traditional light microscopy and modern laser scanning confocal microscopy (LSCM) techniques. Detailed descriptions are provided of the nauplius I, nauplius II and copepodid stages and comparisons are made with the findings for other siphonostomatoids. Nauplius II is previously undescribed and several structures are described at the terminal tip which have not been found in other pennellids. With renewed interest in L. branchialis as a result of expanding gadoid aquaculture in North Atlantic countries, this re-description provides im - portant information on its life history that may be useful for further research into this potentially devastating pathogen.

The use of laser scanning confocal microscopy (LSCM) for creating taxonomic descriptions of copepods is investigated. A new technique is described, which employs a contour filter to process digital LSCM images, allowing taxonomic information to be quickly and accu- rately distilled into a simple illustration. LSCM allows the imaging of whole specimens, which can be rotated and viewed from any angle—a major benefit over light microscopy. Using this tech- nique, it is suggested that taxonomic descriptions can be rapidly produced in a fraction of the time required to produce similar descriptions using traditional light microscopy and hand drawing techniques. Good staining of specimens is, however, essential to produce accurate descriptions and more research is required in this area. The use of LSCM for morphological taxonomy shows great potential, not only for producing taxonomic descriptions, but also providing a comple - mentary adjunct to traditional type specimens in the form of 3D digital 'e-types' deposited in recognised international databases.

Despite growing concern of the ecological risks posed by the European catfishSiluris glanisL. in freshwater fisheries, little information exists on the parasite fauna of this silurid catfish in Britain. Parasitological examinations of releasedS. glanisfrom four still-water fisheries in England revealed the presence ofThaparocleidus vistulensis(Siwak, 1932) andErgasilus sieboldi(Nordmann, 1832), both non-native parasites, the latter known to be an important fish pathogen. This represents the first record ofT. vistulensisfrom British freshwater fish. The human-assisted movement ofS. glanisbetween UK recreational still-water fisheries provides a clear avenue for the introduction and spread of non-native parasites.

Recent developments in semi-automated identification techniques and the increasing ability to rapidly access digital images and taxonomic descriptions offer to increase the range of individuals capable of performing taxonomic identifications. The present study details methodological approaches undertaken in developing a dedicated stain for the visualisation of monogenean haptoral skeletal elements and reproductive sclerites. The histochemical protocols centre around the use of fluorescent dyes and standard light and laser scanning confocal microscopy to support studies of the functional morphology of these hard structures in small, relatively uncompressed specimens, making these structures more amenable to semi-automated analysis and identification techniques. Staining of the sclerites was achieved using a tissue digestion step to remove the tegument and tissues enclosing the sclerites and then staining them in situ with 40 mM chromothrope 2R (C2R) containing 3 mM phosphotungstic acid (PTA) and 0.5% acetic acid (AA) at room temperature for up to 2 days. Visualisation of the armature of the male copulatory organ of warm water Gyrodactylus species was achieved using 40 mM C2R containing 3 mM PTA for 3 days, whilst cold water species were best stained in 6.4 mM C2R for 1 day without an NaOH pre-treatment. The developed techniques allow for good visualisation of the skeletal elements in a number of monogenean groups and promise to assist the preparation and identification/description of specimens. The 2D/3D digital images of specimens prepared in this manner should provide a useful resource for taxonomists and others needing material to assist specimen identification.

The association of Gyrodactylus anguillae Ergens, 1960 with the glass eel stage of Anguilla anguilla (L.) (total body length 61.4 ± 4.9 mm; range 55–70) is reported from the north-western Mediterranean coast of Spain for the first time. A sample of 12,600 glass eels, caught by professional fishermen operating in the mouth of the rivers Fluvia, La Muga and Ter (north-east Spain), was subject to mortalities of ∼1.75% of stock/day following transfer to a research facility. Subsequent losses over a 31-day period amounted to 56% of the initial stocked biomass. Although the moderate burdens of G. anguillae /host (20.2 ± 6; range 11–32) were the primary reason for a subsequent treatment, a simultaneous infection with Trichodina jadranica Raabe, 1958, Trichodina anguillae Wu, 1961 and Ichthyophthirius multifiliis Fouquet, 1876, makes it impossible to attribute the high mortality of glass eels in this case to a single pathogen. A histopathological examination of the gills of moribund fish showed them to be swollen, hyperplastic and necrotic. This study also redescribes G. anguillae , providing for the first time a full 27 character morphometric description of the attachment hooks, and importantly, a photographic record of the armature of the haptor and the male copulatory organ.

The increased use of large tanks for fish cultivation has led to the need for considerations towards hydrodynamic design. Tank velocities must be optimal for maintaining fish health, muscle tone, and respiration. Velocities must also provide adequate biosolid removal to prevent oxygen depletion and the spread of pathogens. As it is not always possible to reach equilibrium of these requirements, regular house-keeping must be maintained to keep culture tanks clean. In larger tank systems, the task of cleaning may be highly labour-intensive or even impractical due to access issues. A bespoke automated mechanical cleaning device was designed and constructed to aid the removal of biosolids. An unpaired t -test confirmed that tanks with the cleaning device showed a significant (P

This paper is a brief introduction to epidemiology and its application to farmed fish health and welfare with examples from the United Kingdom. Epidemiology has the potential to do a great deal more than just identify risk factors. Indeed in many cases useful risk factors cannot be identified due to the complexity of the disease problems and the lack of resources. Epidemiological principles or analytical techniques have been applied in animal welfare studies, and they can reduce the cost of disease monitoring or surveillance and disease control. However, for epidemiological studies to make a real contribution to farmed fish health and welfare it is often necessary to use multidisciplinary teams, obtain good data and coordinate efforts on the major problems.

Despite routine screening requirements for the notifiable fish pathogen Gyrodactylus salaris, no standard operating procedure exists for its rapid identification and discrimination from other species of Gyrodactylus. This study assessed screening and identification efficiencies under real-world conditions for the most commonly employed identification methodologies: visual, morphometric and molecular analyses. Obtained data were used to design a best-practice processing and decision-making protocol allowing rapid specimen throughput and maximal classification accuracy. True specimen identities were established using a consensus from all three identification methods, coupled with the use of host and location information. The most experienced salmonid gyrodactylid expert correctly identified 95.1% of G. salaris specimens. Statistical methods of classification identified 66.7% of the G. salaris, demonstrating the need for much wider training. Molecular techniques (internal transcribed spacer region-restriction fragment length polymorphism (ITS-RFLP)/cytochrome c oxidase I (COI) sequencing) conducted in the diagnostic laboratory most experienced in the analysis of gyrodactylid material, identified 100% of the true G. salaris specimens. Taking into account causes of potential specimen loss, the probabilities of a specimen being accurately identified were 95%, 87% and 92% for visual, morphometric and molecular techniques, respectively, and the probabilities of correctly identifying a specimen of G. salaris by each method were 81%, 58% and 92%. Inter-analyst agreement for 189 gyrodactylids assessed by all three methods using Fleiss' Kappa suggested substantial agreement in identification between the methods. During routine surveillance periods when low numbers of specimens are analysed, we recommend that specimens be analysed using the ITS-RFLP approach followed by sequencing of specimens with a "G. salaris-like" (i.e. G. salaris, Gyrodactylus thymalli) banding pattern. During periods of suspected outbreaks, where a high volume of specimens is expected, we recommended that specimens be identified using visual identification, as the fastest processing method, to select "G. salaris-like" specimens, which are subsequently identified by molecular-based techniques.

Histochemical and ultrastructural investigations were conducted on the mucous cells of the intestine of brown trout, Salmo trutta L., naturally infected with the cestode Cyathocephalus truncatus (Pallas, 1781) and the acanthocephalan Echinorhynchus truttae Shrank, 1788. A subpopulation of 45 S. trutta were examined of which 15 specimens harboured E. truttae, 15 of which were infected with C. truncatus and 15 fish, the control group, were uninfected. In histological sections, hyperplasia and hypertrophy of the mucous cells were evident at the site of parasite infection. Enhanced mucus secretion was also recorded in infected fish. The number of mucous cells close to the site of parasite attachment within the intestine was significantly higher than the number detected in uninfected individuals and in infected individuals at sites 1 cm or greater from the point of parasite attachment. There were no significant differences between the number of mucous cells found at the latter two sites. Alcian blue and periodic acid-Schiff's staining of representative histological sections revealed a significant increase in the number of mucous cells staining positively for acid glycoconjugates compared to the number of cells found in the intestines of uninfected S. trutta. In transmission electron microscopy sections, each mucous cell typically possessed an elongated, basally positioned nucleus. The cytoplasm was observed to possess numerous electron dense and lucent vesicles, in addition to well-developed rough endoplasmic reticulum, Golgi apparatus and a few round mitochondria.

Gyrodactylus eyipayipi sp. n. is described from the skin, gills, flute and male brood pouch of captive specimens of the greater pipefish Syngnathus acus L., collected for and maintained at the Two Oceans Aquarium in Cape Town, South Africa. It is the first marine Gyrodactylus species reported from the African continent. The new species is compared to the three known Gyrodactylus species affecting syngnathiform hosts (G. pisculentus Williams, Kritsky, Dunnigan, Lash et Klein, 2008, G. shorti Holliman, 1963, and G. syngnathi Appleby, 1996). Although all four species have similar-sized and shaped attachment hooks with some overlap, separation of the species is possible using marginal hook morphology. The marginal hooks of G. eyipayipi measure (mean) 30 pm in total length and are larger than those of the three other species (mean, 24-28 tm). Gyrodactylus eyipayipi can also be discriminated based on differences in the shape of the marginal hook sickle notably by its long sickle point which extends far beyond the toe, its blunt rounded toe and, by the approximate rectangular shape to the base of the sickle. By comparison, the sloping toe regions of G. pisculentus and G. syngnathi give the sickle bases an approximately triangular shape, whilst the short sickle point and open aperture to the sickles of G. shorti allow for their discrimination from G. eyipayipi.

Ichthyophthirius multifiliis , more commonly known as ‘white spot’ is recognised as one of the most pathogenic diseases of wild and cultured freshwater fish. In trout hatchery systems infections can quickly establish and result in high mortality if left unregulated. Current control centres around the use of regular bath treatments with formalin, however, treatments are not always effective and are labour intensive. Environmentally safe, non-chemical alternatives are required. This paper describes the performance of a mechanical system developed to remove cysts from commercial trout raceways. The system consists of two parts: a specially designed suction head connected to a pump that is used to vacuum the bottom of hatchery raceways, and a low-adhesion polymer raceway lining. Following tests on a series of potential linings, the most efficacious product in preventing settlement of cysts was used to line three raceways in a commercial rainbow trout ( Oncorhynchus mykiss ) hatchery. Over a period of three months, lined raceways were vacuumed on a daily basis. The three control raceways were maintained according to the farms normal husbandry procedures. Approximately thirty fish were sampled from each raceway at fortnightly intervals, and the abundance of the parasite in each raceway determined. The mechanical system led to a significant reduction in the abundance of the parasite in the test raceways, with a mean abundance of 361.88 ± 260.75 parasites per fish in control raceways compared with 1.64 ± 1.59 parasites per fish in the test raceways at the peak of the infection. Additionally fish survival was significantly higher in test raceways over control, with a mean of 84.5% of the stock surviving in the test raceways compared with only 70.6% in the controls by trial end.

The monogenean Gyrodactylus salaris Malmberg, 1957 is considered one of the most important parasites of wild salmonids in the European Community due to the heavy ecological and economical damage it has inflicted on Atlantic salmon (Salmo salar) parr populations. Rainbow trout (Oncorhynchus mykiss) is susceptible to G. salaris and can act as a suitable carrier host and, consequently, its trade in EU territory is restricted in relation to the status of ‘‘recognized free’’ zones. Despite the economic importance of rainbow trout farming in Italy, information on the Italian gyrodactylid fauna is lacking and prior to this study, G. salaris had not been officially reported. During a routine health examination of farmed rainbow trout stock throughout Central and Northern Italy in 2004–2005, five fish farms were found to be infected with G. salaris alongside three other gyrodactylids. Morphological and molecular characterisation confirmed the presence of G. salaris, Gyrodactylus teuchis Lautraite, Blanc, Thiery, Daniel et Vigneulle, 1999 and Gyrodactylus derjavinoides Malmberg, Collins, Cunningham et Jalali, 2007, while Gyrodactylus truttae Glasser, 1974 was identified by morphological analysis only. The findings from this study extend the distribution of G. salaris within Europe and highlight the importance of the rainbow trout trade in its dissemination.

Since Norway experienced the devastating Gyrodactylus salaris (Monogenea) epidemics in Atlantic salmon Salmo salar, there has been heightened interest in how to treat gyrodactylosis in fish. Here we summarize chemical treatments previously used against gyrodactylids and discuss the main problems associated with these control measures including efficacy, host toxicity, human health concerns and application of treatments. Unfortunately, for these reasons and because of the different methodologies and different parasite and host species used in previous studies, it is difficult to recommend effective chemotherapeutic treatments. However, we suggest a method for manual removal of gyrodactylids from the host suitable for use in small-scale research facilities.

A recent investigation into the myxozoan fauna of common gobies, Pomatoschistus microps, from the Forth Estuary in Scotland, revealed numerous myxosporean cysts within the gill cartilage. They were composed of polysporous plasmodia containing myxobolid spores that were morphologically different from the other known species of Myxobolus and from the myxosporeans previously recorded from this host (i.e. the ceratomyxid Ellipsomyxa gobii, infecting the gall bladder, and the kudoid Kudoa camarguensis, infecting the muscle tissues). Spores were ovoid, 9.4 x 9.1 microm with a thickness of 6.6 microm, with two pyriform polar capsules, the polar filaments of which had four to five turns. Molecular analysis of the parasite's small subunit rDNA region, based upon a contiguous sequence of 1,558 base pairs, discriminated it from other myxosporean species that have been characterized so far. A comparison of the spore morphology and the molecular sequences determined for this new isolate with other myxozoans described to date, confirmed its identity as a previously unknown myxobolid supporting the proposal that this isolate be elevated to the species level as a new species within the genus Myxobolus. A phylogenetic analysis places this new myxobolid, Myxobolus albi n. sp., in a basal position of a clade containing the majority of Henneguya spp. sequenced to date and various Myxobolus spp.

Gyrodactylus orecchiae sp. n. (Monogenea, Gyrodactylidae) is described from the skin, fins, eyes and gills of juvenile Sparus aurata L. (gilthead seabream) following two outbreaks of gyrodactylosis amongst stocks held in inshore floating cages on the Adriatic coast of Albania and Croatia. Fish were heavily infected (1000+ gyrodactylids/fish) with G. orecchiae which reportedly resulted in approximately 2-10% mortality amongst the infected stock. Morphologically, the haptoral hooks of G. orecchiae most closely resemble those of Gyrodactylus arcuatus Bychowsky, 1933 in the approximate shape of the ventral bar with its pronounced ventral bar processes and marginal hook sickles which possess a square line to the inner edge of the sickle blade and large rounded heels. The marginal hooks are also morphologically similar to those of Gyrodactylus quadratidigitus Longshaw, Pursglove et Shinn, 2003 and Gyrodactylus colemanensis Mizelle et Kritsky, 1967, but G. orecchiae can be readily discriminated from all three species by the characteristic infolding of the hamuli roots and the shape of the marginal hook sickle. Molecular sequencing of the ITS1, 5.8S, ITS2 regions (513+157+404 bp, respectively) of G. orecchiae and alignment with other gyrodactylids for which these same genomic regions have been determined, suggests that this is a new species. No similarities were found when the ITS1 region of G. orecchiae was compared with 84 species of Gyrodactylus available on GenBank.

SUMMARYGyrodactylus salaris is a serious pest of wild pre-smolt Atlantic salmon (Salmo salar) in Norway. The closely related G. thymalli, originally described from grayling (Thymallus thymallus), is assumed harmless to both grayling and salmon. The 2 species are difficult to distinguish using traditional, morphometric methods or molecular approaches. The aim of this study was to explore whether there is a consistent pattern of morphometrical variation between G. salaris and G. thymalli and to analyse the morphometric variation in the context of ‘diagnostic realism’ (in natural populations). Specimens from the type-material for the 2 species are also included. In total, 27 point-to-point measurements from the opisthaptoral hard parts were used and analysed by digital image processing and uni- and multivariate morphometry. All populations most closely resembled its respective type material, as expected from host species, with the exception of G. thymalli from the Norwegian river Trysilelva. We, therefore, did not find clear support in the morphometrical variation among G. salaris and G. thymalli for an a priori species delineation based on host. The present study also indicates an urgent need for more detailed knowledge on the influence of environmental factors on the phenotype of gyrodactylid populations.