Ecotoxicological Effects of Potassium Dichromate on the Tadpole Shrimp Triops longicaudatus.

The tadpole shrimp Triops longicaudatus is a freshwater crustacean with fast embryonic and larval development, short life cycle, and high fecundity. They are very active swimmers of a reasonable size, easy to spot and record. Such characteristics make it a promising candidate as an experimental model in ecotoxicology to evaluate the effects of aquatic pollutants, particularly using its locomotor behavior as an endpoint. To evaluate the sensitivity of T. longicaudatus and develop endpoints of interest, we conducted exposure experiments with lethal and sub-lethal concentrations of potassium dichromate, a compound known for its ecotoxicological importance and as a hexavalent chromium source. The endpoints evaluated were mortality, growth, sexual maturation, reproductive output, cholinesterase activity and locomotor/swimming behavior. The 96 h median lethal concentration was found to be 65 µg/L. Furthermore, exposure to potassium dichromate at higher concentrations had a significant negative impact on the growth rate of T. longicaudatus in terms of both body mass and length. The time for maturation was also delayed at higher concentrations. In addition, locomotor behavior allowed for the discrimination of all tested chromium concentrations and the control group and from each other, proving to be the most sensitive endpoint. Overall, the data support the potential of T. longicaudatus as a model for ecotoxicity testing, using apical endpoints with impact at the population level; in particular, results suggest that behavior assessments in this species might be useful for detecting hazardous compounds in environmental monitoring of freshwater ecosystems.

Synopsis of the Species of Coccidians Reported in Marine Fish.

Eimeriid coccidians represent one of the largest groups of parasitic unicellular organisms and comprise many species of veterinary and medical importance. The aim of this work is to provide information, as complete as possible, concerning the oocyst phase of the species of coccidians (Apicomplexa: Eimeriorina) with four sporocysts, which were reported in marine fish. For each species, the accepted scientific name and respective authorities, its synonyms, reported hosts, site of infection (organ), and geographic distribution have been assembled. Available information on morphology (oocyst, sporocyst, and sporozoite) and GenBank accession numbers were also compiled. A total of 100 species of coccidians were described and reported from 60 families of marine fishes. Most species have been described from marine teleosts, with only 14 of the species described from marine elasmobranchs. Most of the species reported in marine fish belong to the genera Eimeria and Goussia, and only a handful belong to the genera Epieimeria, Calyptospora, and Crystallospora. Although marine coccidians have began to be described for more than one century, the collection of genetic data on marine fish coccidians only started in the 2010s and remains largely disconnected from the morphological analysis of specimens, which is available for only six formally described species.

Susceptibility of Sea Bream (Sparus aurata) to AIP56, an AB-Type Toxin Secreted by Photobacterium damselae subsp. piscicida.

Photobacterium damselae subsp. piscicida (Phdp) is a Gram-negative bacterium that infects a large number of marine fish species in Europe, Asia, and America, both in aquacultures and in the natural environment. Among the affected hosts are economically important cultured fish, such as sea bream (Sparus aurata), sea bass (Dicentrarchus labrax), yellowtail (Seriola quinqueradiata), and cobia (Rachycentron canadum). The best characterized virulence factor of Phdp is the Apoptosis-Inducing Protein of 56 kDa (AIP56), a secreted AB-type toxin that has been shown to induce apoptosis of sea bass phagocytes during infection. AIP56 has an A subunit that displays metalloprotease activity against NF-kB p65 and a B subunit that mediates binding and internalization of the A subunit in susceptible cells. Despite the fact that the aip56 gene is highly prevalent in Phdp isolates from different fish species, the toxicity of AIP56 has only been studied in sea bass. In the present study, the toxicity of AIP56 for sea bream was evaluated. Ex vivo assays showed that sea bream phagocytes are resistant to AIP56 cytotoxicity and that resistance was associated with an inefficient internalization of the toxin by those cells. Accordingly, in vivo intoxication assays revealed that sea bream is much more resistant to AIP56-induced lethality than sea bass. These findings, showing that the effect of AIP56 is different in sea bass and sea bream, set the basis for future studies to characterize the effects of AIP56 and to fully elucidate its virulence role in different Phdp susceptible hosts.

Synopsis of the species of Myxobolus (Cnidaria, Myxozoa, Myxosporea) described between 2014 and 2020.

A synopsis of the species of Myxobolus Bütschli, 1882 (Cnidaria, Myxosporea, Myxobolidae) described from 2014 up till now is presented. It includes 122 nominal species described all over the world. For each of the species, the most relevant morphological and morphometric data, as well as data are provided related to the location in the host, type host and type locality. The GenBank accession numbers are provided whenever possible, and the spores were redrawn based on the original descriptions. The bibliography includes all the papers containing the species descriptions.

Survey of Kudoa spp. (Myxozoa, Cnidaria) in fishes from the Madeira Archipelago and the Portuguese mainland coast: detection of Kudoa thyrsites in new hosts Scomber colias and Micromesistius poutassou.

Myxozoan parasites of the genus Kudoa Meglitsch, 1947 are associated with post-mortem tissue degradation that causes great financial losses to commercial fisheries. Kudoa thyrsites (Gilchrist, 1924) is a species with a very wide host range including commercial tunas, mackerels, salmonids and flatfishes. A sample of 190 fishes of 18 species from the Madeira Archipelago and 30 Atlantic chub mackerel, Scomber colias Gmelin, and 30 blue whiting, Micromesistius poutassou (Risso), from the Portuguese mainland coast were examined for the presence of species of Kudoa. The prevalence of Kudoa spp. was 80% in M. poutassou and 60% in S. colias. No spore was detected in S. colias from Madeira, which was confirmed by specific PCR screening of the muscle from all individuals of S. colias. SSU rDNA analysis revealed that M. poutassou and S. colias from the Portuguese mainland coast were infected with K. thyrsites, an economically important myxozoan parasite. Both sequences were identical with sequences of the eastern Atlantic K. thyrsites genotype, including that from the type host of this parasite. This is the first report of K. thyrsites from M. poutassou and S. colias. The fact that spores of species of Kudoa were not detected in fishes screened in the Madeira Archipelago may be explained by various ecological factors, such as the absence of a continental shelf, a short insular shelf, and oceanic waters with low productivity, all resulting in reduced abundance of benthic organisms. Consequently, it is possible that as yet unknown annelid definitive hosts of Kudoa spp. are absent or very rare near Madeiran coasts.

Phylogenetic Affinities and Infection Patterns of Goussia Infecting Sardina pilchardus from the NE Atlantic.

PURPOSE: European pilchard (Sardina pilchardus) is a highly valued fish in many European countries, particularly in Portugal. Despite current stock declines and the threats coccidia pose to European pilchards (e.g. castration), little is known about coccidian parasites infecting pilchards captured off the Portuguese coast. METHODS: In this study, we analyzed the infection patterns, the morphology of oocysts and the phylogenetic relations of coccidian parasites from European pilchard captured in Northern Portugal. RESULTS: Only Goussia oocysts were detected in infected tissues and prevalence of infection was 64% (n = 61). Oocysts were detected primarily in the liver with fewer infections in the stomach, intestine and gonads. No differences were found in the prevalence between seasons. Phylogenetic analysis showed these parasites are closely related to Goussia clupearum, placing them within a recently described group of Goussia, the clupearum type. CONCLUSIONS: Our study provides more data on Goussia from the clupearum type with phylogenetic analysis indicating that these parasites cluster according to fish host taxonomy, thus suggesting some degree of co-evolution.

Effects of Goussia infecting the blue whiting and phylogenetic placement of Goussia infecting marine fish off Northern Portugal.

Coccidian parasites of fish have received considerably less attention than their terrestrial counterparts, and within piscine hosts, most studies have focused on freshwater fish. The present study aimed to describe oocyst morphology, phylogenetic affinities, and the impacts of coccidian parasites infecting the internal organs of a commercially valuable marine fish, the blue whiting (Micromesistius poutassou), captured off the Portuguese coast. As part of the phylogenetic analysis, sequences from coccidians infecting the pout (Trisopterus luscus) and the Atlantic chub mackerel (Scomber colias) were included, and the oocyst morphology of the coccidians infecting the former was also reported. Results showed that the prevalence of coccidiosis in the blue whiting was very high (> 82%), occurring in all analyzed organs, despite being more abundant in the liver. A significant negative correlation was found between the abundance of the parasites in the liver and host condition index (p < 0.05), which indicates a negative effect on the fitness of this host. Phylogenetic analyses of the parasites found in all three species examined identified three different species of Goussia, closely related to Goussia clupearum. Adding to previous research, we propose the existence of a fourth group of Goussia, the clupearum type, able to infect multiple organs and phylogenetic related with G. clupearum.

Didymozoids in Muscle of Atlantic Chub Mackerel (Scomber colias).

BACKGROUND: Digenean trematodes of the family Didymozoidae are tissue parasites that are particularly common in scombrid fish. These parasites can reduce the commercial value of fish, especially the ones occurring in the muscle. PURPOSE: In the present study and for the first time, we report the occurrence of didymozoids in muscle tissue of Atlantic chub mackerel (Scomber colias) collected in northeast Atlantic (Portuguese coast). METHODS: The entire musculature of 64 Scomber colias was removed and examined macroscopically and under a stereomicroscope to search for parasites. RESULTS: The prevalence (3.1%) and abundance (0.03) of infection detected were quite low, but the parasites cause muscle softening decreasing the quality of the infected fish. If the infection levels increase, this may constitute a cause of concern for the fisheries and canning industry. CONCLUSION: Didymozoids identified in this study are closely related to muscle parasites detected in other fish species of the genus Scomber, most probably the same species. Phylogenetic analysis also corroborates the hypothesis that muscle-parasitizing didymozoids are distinct from the ones parasitizing other fish organs.

Lymnaea stagnalis as a freshwater model invertebrate for ecotoxicological studies.

Lymnaea stagnalis, also referred to as great or common pond snail, is an abundant and widespread invertebrate species colonizing temperate limnic systems. Given the species importance, studies involving L. stagnalis have the potential to produce scientifically relevant information, leading to a better understanding of the damage caused by aquatic contamination, as well as the modes of action of toxicants. Lymnaea stagnalis individuals are easily maintained in laboratory conditions, with a lifespan of about two years. The snails are hermaphrodites and sexual maturity occurs about three months after egg laying. Importantly, they can produce a high number of offspring all year round and are considered well suited for use in investigations targeting the identification of developmental and reproductive impairments. The primary aims of this review were two-fold: i) to provide an updated and insightful compilation of established toxicological measures determined in both chronic and acute toxicity assays, as useful tool to the design and development of future research; and ii) to provide a state of the art related to direct toxicant exposure and its potentially negative effects on this species. Relevant and informative studies were analysed and discussed. Knowledge gaps in need to be addressed in the near future were further identified.

Parasites of amberjacks from the archipelago of Madeira, Eastern Atlantic.

Amberjacks, Seriola spp., are a group of carangid fishes of economic importance for fisheries and aquaculture worldwide. A survey of the parasites of greater amberjack S. dumerili and almaco jack or longfin yellowtail S. rivoliana from the Madeira archipelago (including the Madeira and Selvagens Islands) was carried out. This work is the first parasitological study of these 2 species in the Eastern Atlantic. A total of 14 parasite taxa were detected in the 47 fish analysed: Allencotyla mcintoshi, Stephanostomum petimba, Rhadinorhynchus sp. and Caligus aesopus (in both Seriola spp.); Dionchus agassizi, Zeuxapta seriolae, Tormopsolus orientalis, Didymocystis sp. and Anisakis sp. (in S. rivoliana); Tetrochetus coryphaenae, Stephanostomum sp., S. ditrematis, Oncophora melanocephala and Hysterothylacium seriolae (in Seriola dumerili). The monogenean Dionchus agassizi and the nematode O. melanocephala constitute new host records for the genus Seriola, and the species Allencotyla mcintoshi, Z. seriolae, Tormopsolus orientalis, H. seriolae, and C. aesopus are reported in the region of Madeira for the first time. Some of the parasites detected, in particular Z. seriolae and C. aesopus, could constitute a threat to amberjack aquaculture, and measures should be taken to prevent their introduction into sea cages.

Synopsis of the species of Ceratomyxa Thélohan, 1892 (Cnidaria, Myxosporea, Ceratomyxidae) described between 2007 and 2017.

A synopsis of the species of Ceratomyxa Thélohan, 1892 (Cnidaria, Myxosporea, Ceratomyxidae) described between 2007 and 2017 is presented, including 83 nominal species. For each species, the most important morphological and morphometric features are indicated in tabulated format. Included are also the site of infection within the host, and geographical location, plus a full bibliography of the original records of species. Molecular data (GenBank accession numbers) are also provided whenever possible.

Parasites of skipjack, Katsuwonus pelamis, from Madeira, Eastern Atlantic.

Skipjack tuna, Katsuwonus pelamis, is a tropical species of economic importance for fisheries around the world. It occurs seasonally in subtropical waters around Madeira archipelago, in the warmer months. In this study, a parasitological analysis was carried out on a sample of 30 skipjack caught near Madeira Island. A total of 24 parasite taxa were found in this sample. The skipjack parasite community detected was characterized by a wide diversity of parasites, with a predominance of adult didymozoid trematodes, and high prevalences of Tentacularia coryphaenae cestode larvae and Anisakis sp. larvae. Microhabitat distribution of gill parasites was assessed for the most prevalent species, and correlations between parasite abundance and various host features such as size, condition, and fat content were investigated. Parasite taxa which might be useful as biological tags in future studies of skipjack migrations in the Eastern Atlantic were selected.

Observations on non-random distribution of spores of Henneguya spp. (Cnidaria: Myxosporea: Myxobolidae) within plasmodia.

Species of the cnidarian genus Henneguya Thélohan, 1892 (Myxosporea: Myxobolidae) are histozoic parasites commonly found in freshwater and, more rarely, in marine fish. The development of these parasites in fish tissues includes the formation of plasmodia within which occurs the sporogony originating spores with two caudal processes, which are usually randomly distributed within the plasmodia. In this report the authors present some cases of non-random distribution of the spores of six species of Henneguya within their plasmodia. Two different patterns of non-random distribution were found based on a literature survey. These patterns and their origin are discussed. Apparently this non-random distribution of the spores is due to both internal and external factors.

Parasites of the mutton snapper Lutjanus analis (Perciformes: Lutjanidae) in Alagoas, Brazil.

A parasitological survey was carried out on a sample of sixty mutton snappers (Lutjanus analis) that were caught on the coast of Alagoas, northeastern Brazil. The parasite diversity and infection levels were low. The ectoparasite Rocinela signata Schioedte & Meinert, 1879 (Isopoda: Aegidae), and larvae of two endoparasites, Trypanorhyncha gen. sp. and Hysterothylacium sp. (Nematoda: Anisakidae), were detected. The significance of these parasites is discussed in the context of their transmission pathways and potential impact.

Parasites of the Mutton Snapper Lutjanus analis (Perciformes: Lutjanidae) in Alagoas, Brazil / Parasitas de Cioba Lutjanus analis (Perciformes: Lutjanidae) em Alagoas, Brasil

A parasitological survey was carried out on a sample of sixty mutton snappers (Lutjanus analis) that were caught on the coast of Alagoas, northeastern Brazil. The parasite diversity and infection levels were low. The ectoparasite Rocinela signata Schioedte & Meinert, 1879 (Isopoda: Aegidae), and larvae of two endoparasites, Trypanorhyncha gen. sp. and Hysterothylacium sp. (Nematoda: Anisakidae), were detected. The significance of these parasites is discussed in the context of their transmission pathways and potential impact.

Um estudo parasitológico foi realizado em 60 exemplares de cioba, Lutjanus analis, capturados ao largo de Alagoas, no Nordeste do Brasil. A diversidade e níveis de infecção parasitária foram baixos. Foram detectados o ectoparasito Rocinela signata Schioedte & Meinert, 1879 (Isopoda: Aegidae) e dois endoparasitos, larvas de Trypanorhyncha gen. sp. e larvas de Hysterothylacium sp. (Nematoda: Anisakidae). O significado desses parasitos é discutido no âmbito das suas vias de transmissão e potencial impacto.

Synopsis of the species of Kudoa Meglitsch, 1947 (Myxozoa: Myxosporea: Multivalvulida).

A synopsis of the species of Kudoa Meglitsch, 1947 (Myxozoa, Myxosporea, Multivalvulida) is presented, including 95 nominal species. For each species the most relevant morphological and morphometric features are indicated in tabulated format. Included are data on the site of infection within the host, the type-host and type-locality, plus a full bibliography of the original records for these species. Molecular data (GenBank accession numbers) are also provided whenever possible.

Distribution of Hatschekia pagellibogneravei (Copepoda: Hatschekiidae) on the gills of Pagellus bogaraveo (Teleostei: Sparidae) from Madeira, Portugal.

A population of the gill parasite Hatschekia pagellibogneravei (Hesse, 1878) was studied on one of its sparid fish hosts, the blackspot seabream, Pagellus bogaraveo (Brünnich), off the coast of Madeira Island, Portugal, northeast Atlantic. Very high infection levels of this copepod were detected, with no significant seasonal differences. Abundance was negatively correlated with fish size. There were significant differences in the distribution of this copepod among the gill arches of the host, which seem to be best explained by differences in water flow within the gill habitat.

Infection levels and diversity of anisakid nematodes in blackspot seabream, Pagellus bogaraveo, from Portuguese waters.

The blackspot seabream, Pagellus bogaraveo, is a sparid fish of great economic importance in the northeast Atlantic. The main aim of this work was to assess the infection levels and diversity of anisakid nematodes parasitizing P. bogaraveo from Portuguese waters. The anisakid larvae were identified by polymerase chain reaction-restriction fragment length polymorphism analysis and ten different patterns were observed, four of which were not previously reported in the literature. Moreover, several species were detected for the first time in this host: Anisakis simplex × Anisakis pegreffii hybrids, Anisakis ziphidarum, Anisakis typica, Anisakis physeteris, as well as three undescribed anisakids Anisakis sp. PB-2009, Anisakis sp. PB-2010, and Contracaecum sp. PB-2010. The ITS1-5.8S-ITS2 region was sequenced and analyzed phylogenetically, revealing that our anisakids were distributed by the two distinct clades reported previously, corresponding to the two recognized larval morphotypes. Moreover, a group of organisms, including our specimens from Madeira and the previously reported Anisakis sp. HC-2005, cluster together and seem to belong to clade I. A certain degree of intraspecific diversity was also detected. Samples from mainland waters had the highest infection levels and were dominated by A. pegreffii. Madeira had the highest diversity overall, dominated by Anisakis sp. PB-2010. Fish from the Azores had the lowest infection levels, and the species with the highest relative abundance was A. physeteris. The anisakid nematode communities were relatively similar in mainland waters but very distinct in both the Azores and Madeira islands, suggesting the existence of at least three different stocks of P. bogaraveo in the northeast Atlantic.

Two species of Rhabdochona Railliet, 1916 (Nematoda: Rhabdochonidae) parasitising cyprinid fishes in Iraq, with a redescription of R. tigridis Rahemo, 1978 (emend.).

Two species of Rhabdochona Railliet, 1916 (Nematoda: Rhabdochonidae) were recorded from cyprinid fishes in the basin of the River Tigris, northern Iraq: adults of R. (R.) tigridis Rahemo, 1978 (emend.) from Capoeta trutta (Heckel) and Cyprinion macrostomum Heckel and fourth-stage larvae of R. (Globochona) sp. from C. macrostomum, Barbus barbulus Heckel and Barbus kersin Heckel. Light and scanning electron microscopical studies of this material made possible a detailed redescription of R. tigridis, which is characterised by 14 anterior prostomal teeth and filamented eggs. It differs from the most similar species, R. fortunatowi Dinnik, 1933, mainly in the presence of large deirids close to the prostom. R. grandipapillata Rahemo & Kasim, 1979 is considered a junior synonym of R. tigridis. Fourth-stage larvae of Rhabdochona (G.) sp., characterised by eight anterior prostomal teeth and the presence of caudal processes on the tail tip, represent the first record of a Rhabdochona species of the subgenus Globochona Moravec, 1972 in Iraq.

Scuticociliate infection and pathology in cultured turbot Scophthalmus maximus from the north of Portugal.

During the years 2004 and 2005 high mortalities in turbot Scophthalmus maximus (L.) from a fish farm in the north of Portugal were observed. Moribund fish showed darkening of the ventral skin, reddening of the fin bases and distended abdominal cavities caused by the accumulation of ascitic fluid. Ciliates were detected in fresh mounts from skin, gill and ascitic fluid. Histological examination revealed hyperplasia and necrosis of the gills, epidermis, dermis and muscular tissue. An inflammatory response was never observed. The ciliates were not identified to species level, but the morphological characteristics revealed by light and electronic scanning microscopes indicated that these ciliates belonged to the order Philasterida. To our knowledge this is the first report of the occurrence of epizootic disease outbreaks caused by scuticociliates in marine fish farms in Portugal.