Streams in the Mediterranean Region are not for mussels: Predicting extinctions and range contractions under future climate change.

Climate change is becoming the leading driver of biodiversity loss. The Mediterranean region, particularly southwestern Europe, is already confronting the consequences of ongoing global warming. Unprecedented biodiversity declines have been recorded, particularly within freshwater ecosystems. Freshwater mussels contribute to essential ecosystem services but are among the most threatened faunal groups on Earth. Their poor conservation status is related to the dependence on fish hosts to complete the life cycle, which also makes them particularly vulnerable to climate change. Species Distribution Models (SDMs) are commonly used to predict species distributions, but often disregard the potential effect of biotic interactions. This study investigated the potential impact of future climate on the distribution of freshwater mussel species while considering their obligatory interaction with fish hosts. Specifically, ensemble models were used to forecast the current and future distribution of six mussel species in the Iberian Peninsula, including environmental conditions and the distribution of fish hosts as predictors. We found that climate change is expected to severely impact the future distribution of Iberian mussels. Species with narrow ranges, namely Margaritifera margaritifera and Unio tumidiformis, were predicted to have their suitable habitats nearly lost and could potentially be facing regional and global extinctions, respectively. Anodonta anatina, Potomida littoralis, and particularly Unio delphinus and Unio mancus, are expected to suffer distributional losses but may gain new suitable habitats. A shift in their distribution to new suitable areas is only possible if fish hosts are able to disperse while carrying larvae. We also found that including the distribution of fish hosts in the mussels' models avoided the underprediction of habitat loss under climate change. This study warns of the imminent loss of mussel species and populations and the urgent need of management actions to reverse current trends and mitigate irreversible damage to species and ecosystems in Mediterranean regions.

Is parasite taxonomy really in trouble? A quantitative analysis.

In recent years, several authors have warned that the number of trained experts in parasite taxonomy and systematics is declining rapidly, and that the whole field is at risk. However, to date there has been no quantitative analysis to support these claims. Here, we provide the first such assessment, focusing on helminths parasitic in fish as an example, and using a representative dataset comprising over 2000 helminth species described in the past two decades. Based on standard indices of inequality, we demonstrate that a small group of highly prolific taxonomists are associated with the vast majority of new species descriptions, indicating that the research output in parasite discovery is concentrated in the hands of a small number of individuals. This situation has not improved over time. Furthermore, there has been no turnover over time, i.e., no replacement of the most prolific taxonomists: the individual researchers ranking among the most prolific describers of new parasite helminth species in the past decade were generally also the most prolific in the decade before that. Finally, based on the year in which these most prolific taxonomists published their first species description, we estimate that a large proportion of them are in the latter stages of their career. Inequalities in research output are the norm across scientific disciplines. However, persistent inequality in the number of species description per author, coupled with the same individuals ranking as most prolific over time and a majority of them in late career, all combine to support earlier claims that parasite taxonomy may well face a crisis in the form of an impending loss of taxonomic expertise.

Sea lice (Copepoda: Caligidae) from South Africa, with descriptions of two new species of Caligus.

Thirteen species of sea lice (family Caligidae) are reported from a range of elasmobranch and actinopterygian fishes caught off South Africa or obtained from public aquaria in South Africa. Two new species of Caligus Müller, 1785 are described: C. linearis n. sp. from Pomatomus saltatrix (Linnaeus) and C. tumulus n. sp. from Chrysoblephus cristiceps (Valenciennes). A supplementary description is provided for both sexes of Caligus tetrodontis Barnard, 1948 taken from Amblyrhynchotes honckenii (Bloch) and previous records of this parasite from South African fishes are critically reviewed. It is concluded that Caligus material from Arothron hispidus Linnaeus was previously misidentified as C. tetrodontis and is in urgent need of re-examination. Morphological and molecular observations on Caligus furcisetifer Redkar, Rangnekar & Murti, 1949 indicate that this copepod is phenotypically and genetically identical to Lepeophtheirus natalensis Kensley & Grindley, 1973, and the latter becomes a junior subjective synonym of C. furcisetifer. We include new geographical distribution records for Caligus longipedis Bassett-Smith, 1898, C. rufimaculatus Wilson, 1905 and Lepeophtheirus spinifer Kirtisinghe, 1937, extending into South African waters, as well as both new distribution and host records for Alebion gracilis Wilson, 1905, Caligus dakari van Beneden, 1892 and Lepeophtheirus acutus Heegaard, 1943. The molecular analysis confirmed the monophyly of the genus Caligus. The South African species of Caligus did not cluster together, but the two included South African species of Lepeophtheirus were recovered as sister taxa.

Anisakis Nematodes in Fish and Shellfish- from infection to allergies.

Anisakidosis is a zoonotic parasitosis induced by members of the family Anisakidae. The anisakid genera includes Anisakis, Pseudoterranova, Hysterothylacium and Contracaecum. The final definitive hosts of these nematodes are marine mammals with a complex life cycle. These nematode parasites use different crustaceans and fish species as intermediate or paratenic hosts and humans are accidental hosts. Human anisakiasis, the infections caused by members of the genus Anisakis, occurs, when seafoods, particularly fish, contaminated with the infective stage (third stage larvae [L3]) of this parasite, are consumed. Pseudoterranovosis, on the other hand is induced by members of the genus Pseudoterranova. These two genera of anisakids have been implicated in human disease globally. There is a rise in reports of gastro-intestinal infections accompanied by allergic reactions caused by Anisakis simplex and Anisakis pegreffii. This review provides an update on current knowledge on Anisakis as a food-borne parasite with special focus on the increasingly reported diversity of fish and crustacean hosts, allergens and immunological cross-reactivity with invertebrate proteins rendering this parasite a significant public health issue.

Motility, morphology and phylogeny of the plasmodial worm, Ceratomyxa vermiformis n. sp. (Cnidaria: Myxozoa: Myxosporea).

The Myxozoa demonstrate extensive morphological simplification and miniaturization relative to their free-living cnidarian ancestors. This is particularly pronounced in the highly derived myxosporeans, which develop as plasmodia and pseudoplasmodia. To date, motility in these stages has been linked with membrane deformation (e.g. as pseudopodia and mobile folds). Here we illustrate a motile, elongate plasmodium that undergoes coordinated undulatory locomotion, revealing remarkable convergence to a functional worm at the cellular level. Ultrastructural and confocal analyses of these plasmodia identify a highly differentiated external layer containing an actin-rich network, long tubular mitochondria, abundant microtubules, a secreted glycocalyx layer, and an internal region where sporogony occurs and which contains homogeneously distributed granular/fibrillar material. We consider how some of these features may support motility. We also describe the species based on spore morphology and SSU rDNA sequence data, undertake molecular phylogenetic analysis to place it within an early-diverging clade of the ceratomyxids, and evaluate the resultant implications for classification (validity of the genus Meglitschia) and for inferring early host environments (freshwater) of ceratomyxids.

Utilizing ribosomal DNA gene marker regions to characterize the metacercariae (Trematoda: Digenea) parasitizing piscine intermediate hosts in Manipur, Northeast India.

Freshwater fishes in Manipur, Northeast India frequently harbour several types of metacercariae, which based on morphological criteria were identified as Clinostomoides brieni, Euclinostomum heterostomum (Clinostomidae) and Polylekithum sp. (Allocreadiidae). Molecular techniques utilizing PCR amplification of rDNA regions of larger subunit (LSU or 28S), smaller subunit (SSU or 18S) and inter transcribed spacers (ITS1, 2) were used for molecular characterization of these types. Sequences generated from the metacercariae were compared with their related sequences available in public databases; an analysis of the identity matrices and phylogenetic trees constructed was also carried out, which confirmed their identification. Similarly, the sequences generated from Polylekithum sp. were found to be highly similar to the species of the same genus. The rDNA ITS2 secondary structure provided additional confirmation of the robustness of the molecular marker as a tool for taxon-specific characterization.

The importance of wild fish in the epidemiology of Clonorchis sinensis in Vietnam.

Preliminary findings of a high prevalence of Clonorchis sinensis in wild-caught fish in a North Vietnam reservoir (Thac Ba reservoir, Yen Bai Province) prompted a longitudinal epidemiological study of fish infections. Monthly collections of fish from September 2014 to August 2015 were processed for recovery of metacercariae; 1219 fish, representing 22 species, were examined. Seven species were infected with C. sinensis metacercariae. Four species, Toxabramis houdemeri, Hemiculter leucisculus, Cultrichthys erythropterus, and Culter recurvirostris, had high prevalence (31.1 to 76.7 %); metacercarial intensities ranged from 3.9 to 65.7 metacercariae/fish. A seasonal variation of C. sinensis prevalence was observed in T. houdemeri. Variation in intensity of infection occurred in C. erythropterus and H. leucisculus. Intensity and prevalence of C. sinensis in the most highly infected species, T. houdemeri, varied by fish size; prevalence was higher in fish weighing more than 3 g, and intensity was higher in fish weighing more than 5 g. The distribution of metacercariae in the body region of T. houdemeri was significantly higher in the caudal fin (14.7 metacercariae/g), compared to the body and head regions (0.7 and 1.4 metacercariae/g, respectively). Further epidemiological investigations on C. sinensis in this reservoir region should include assessing the relative risk of the different fish species for humans based on the latter's food preferences, and the prevalence of C. sinensis in the community. The snail intermediate host(s) in the reservoir should also be identified along with the ecological factors influencing its exposure to C. sinensis eggs and its subsequent transmission of cercariae to fish. Also needed are investigations on the relative importance of wild and domestic reservoir hosts as sources of egg contamination of the reservoir.

Studies on the life cycle of Haplorchis pumilio (Looss, 1896) (trematoda: heterophyidae) in Venezuela

El ciclo de vida de Haplorchis pumilio se estudió del redia al adulto bajo condiciones naturales y experimentales. La etapa precercarial (redia) se encontró en la glándula digestiva de Melanoides tuberculata (infección natural), de la localidad de Aguasanta, estado Sucre, Venezuela. Las metacercarias se localizaron en los tejidos de la musculatura, debajo de las escamas de la aleta caudal de Rivulus harti (infección natural). Las metacercarias se suministraron a patos, pollos, ratas y ratones; y 3 días después de la infestación fueron encontrados en intestino delgado de los patos, 28 adultos de H. pumilio. Las cercarías producidas por M. tuberculata fueron usadas para intentar infestar experimentalmente a R. harti. Poecilia reticulata, Oreochromis mossambicus y Astyanax spp. y solamente R. harti fue infectado. Las metacercarias de 30 días de edad se usaron en ensayos experimentales en patos y pollos. Un total de 32 adultos de H. pumilio fueron encontrados en los patos, 3 días después de la infección con una inoculación de 40 metacercarias de H. pumilio. Butorides striatus resultó ser el hospededor definitivo natural de H. pumilio. Las características morfométricas de adultos de H. pumilio de los hospederos naturales y experimentales difieren de los descritos previamente. Estas diferencias pueden ser debidas a la diversidad de hospederos y a la distribución geográficas. R. harti y B. striatus son reportados como nuevos hospederos para H. pumilio.

The life cycle of Haplorchis pumilio was studied from redia to adult under natural and experimental conditions. The precercarial stage (redia) was found in the digestive gland of Melanoides tuberculata (natural infection), collected from Aguasanta, Sucre State, Venezuela. Metacercariae were located in muscular tissues, under the scale of the caudal fin of Rivulus harti (natural infection). Metacercariae were supplied to ducks, chickens, rats and mice, and 3 days after infection, 28 adult H. pumilio were recovered from the small intestine of the ducks. R. harti, Poecilia reticulata, Oreochromis mossambicus and Astyanax spp. were exposed experimentally to cercariae emitted by M. tuberculata: only R. harti was found infected. The 30 days old metacercariae were experimentally supplied to ducks and chickens, and a total of 32 adult trematodes were found 3 days after inoculation of 20 metacercarias to each duck. Butorides striatus was found to be the natural final host of H pumilio. Morphometric characteristics of adult H. pumilio from both natural and experimental hosts differ from adults described previously. These differences may be due to differences in host and geographical variations. H. pumilio in R. harti and B. striatus report new host records.