Elisabeth Faliex

Endoparasite species richness of New Caledonian butterfly fishes: host density and diet matter.

Ecological factors may influence the number of parasites encountered and, thus, parasite species richness. These factors include diet, gregarity, conspecific and total host density, habitat, body size, vagility, and migration. One means of examining the influence of these factors on parasite species richness is through a comparative analysis of the parasites of different, but related, host species. In contrast to most comparative studies of parasite species richness of fish, which have been conducted by using data from the literature, the present study uses data obtained by the investigators. Coral reef fishes vary widely in the above ecological factors and are frequently parasitized by a diverse array of parasites. We, therefore, chose to investigate how the above ecological factors influence parasite species richness in coral reef fishes. We investigated the endoparasite species richness of 21 species of butterfly fishes (Chaetodontidae) of New Caledonia. We mapped the diet characters on the existing butterfly fish phylogeny and found that omnivory appears to be ancestral. We also mapped the estimated endoparasite species richness, coded from low to high parasite species richness, on the existing butterfly fish phylogeny and found that low parasite species richness appears to be associated with the ancestral state of omnivory. Different dietary and social strategies appear to have evolved more than once, with the exception of obligate coralivory, which appears to have evolved only once. Finally, after controlling for phylogenetic relationships, we found that only the percentage of plankton in the diet and conspecific host density were positively correlated with endoparasite species richness.

Resorption of unemitted gametes in Lithognathus mormyrus (Sparidae, Teleostei): a possible synergic action of somatic and immune cells.

The resorption of unemitted gametes during the post-spawning period of the male and female reproductive cycles in Lithognathus mormyrus was studied by histochemical, histological and cytological methods. The resorption of residual spermatozoa involved the phagocytotic activity of Sertoli cells bounding the seminiferous cysts of spermatozoa, and those associated with spermatogonia lining the lobular lumen. Spermatozoa remaining in the sperm duct were phagocytozed by the lining epithelial cells. Eosinophilic granulocytes and macrophages were identified in the vicinity of residual spermatozoa. The remnants of oocytes underwent an atretic phenomenon in which follicle cells were firstly involved, inducing a progressive fragmentation of the oocyte cytoplasm. Subsequently, eosinophilic granulocytes invaded oocyte degenerative areas and clung to the remaining vitelline inclusions ensuring their biotransformation into waste products (brown bodies). The analogy of the resorption processes of both male and female unemitted gametes during the post-spawning period of natural reproductive cycle, involving first the enveloping somatic cells and then immune cells, is emphasized.

Dynamic expression of immune response genes in the sea bass, Dicentrarchus labrax, experimentally infected with the monogenean Diplectanum aequans.

The sea bass, Dicentrarchus labrax, is one of the most extensively farmed marine fishes in the Mediterranean. Under the high-density condition common in aquaculture, the monogenean gill parasite Diplectanum aequans can cause significant economic losses. This study used real-time quantitative PCR to investigate the dynamic expression of immune response genes in sea bass infected with Diplectanum aequans. The target genes, interleukin-1 (IL-1beta, transforming growth factor (TGF-beta and T-cell receptor (TCR-beta), were studied in the gills and spleen of the sea bass from the first day of infection until thirty days post- infection. Our results showed that there was an increase in IL-1beta gene expression in the spleen and gills and in TGF-beta gene expression in the gills of infected fish. These results show that parasitic infection induced a local inflammatory reaction and that reaction was restricted to the site of infection. Finally, the absence of relationship between TCR-beta expression and the parasitic infection suggests that the adaptive immune system is not involved in the response against this parasite.

A NEW SPECIES OF DITRACHYBOTHRIDIUM (CESTODA: DIPHYLLIDEA) FROM GALEUS SP. (SELACHII, SCYLIORHYNIDAE) FROM THE SOUTH PACIFIC OCEAN, WITH A REVISION OF THE DIAGNOSIS OF THE ORDER, FAMILY, AND GENUS AND NOTES ON DESCRIPTIVE TERMINOLOGY OF MICROTRICHES

Ditrachybothridium piliformis is a new species from the spiral intestine of a cat shark, Galeus sp., from the southern Pacific Ocean. This is only the second species assigned to Ditrachybothridium. It differs from the type species D. macrocephalum in lacking spines on the scolex, a character originally used to diagnose the genus. The diagnoses of the Ditrachybothridiidae and of Ditrachybothridium have been revised to reflect this difference. This new species is further differentiated from the type species in its possession of pectinate spinitriches on the tegument of the scolex. The holdfast structures of this species are weakly muscularized, with no membrane-bound layer of radial muscles, indicating that the holdfast structures are bothria rather than bothridia as described in the most recent literature. Several reports for other species have indicated the same situation in other diphyllideans. The diagnosis of the order has been revised to reflect this finding.

Parasitism of Gobius bucchichii Steindachner, 1870 (Teleostei, Gobiidae) in protected and unprotected marine environments.

We collected 396 Gobius bucchichii, Steindachner, 1870 (Teleostei, Gobiidae) in and around the marine reserve of Cerbère-Banyuls, in the southeast of France, between March and July 1994. Five species of adult parasites were found: one acanthocephalan, Acanthocephaloides propinquus Dujardin, 1845 (Acanthocephala, Arhythmacanthidae); one nematode, Cucullanus sp. (Nematoda, Cucullanidae); and three species of digenetic trematodes, Helicometra sp. (Digenea, Opeccelidae), Derogenes sp. (Digenea, Hemiuridae) and Deretrema scorpaenicola Bartoli, 1990 (Digenea, Zoogonidae). Fishes collected in a protected area were on average, larger, older, had a higher percentage of regenerated scales, and harbored more parasites.

Sexual competition in an acanthocephalan parasite of fish.

Acanthocephalans are polygamous parasites of vertebrates and some species are known to aggregate in sexual congress to mate. Such a reproductive behaviour could lead to male-male competition for access to females and could have consequences for sexual selection. We dissected 87 gobiid fish, Gobius bucchichii, harbouring 891 acanthocephalans, Acanthocephaloides propinquus. The parasites were sexed and their body sizes were measured. Testicular volume was also evaluated in 82 males in order to establish their phenotypic sexual investment in relation to the estimated sex ratio. We found that parasite intensity (i.e. the number of individuals/fish) was not correlated with fish size, but that parasite size was significantly related to host size. Our results showed that there was a significant relationship between the mean female body size and their number within one host. We found that when the percentage of male parasites in a host increased, presumably increasing male-male competition for access to females, males had a larger testicular volume. We discuss these results in terms of energy allocation, sexual and sperm competition. We conclude that competition for space should be less important for males than competition for access to females. Moreover, increasing testis size should confer advantages to males especially for their reproductive success when sperm competition occurs.

Fish Health and Fisheries, Implications for Stock Assessment and Management: The Mediterranean Example

Although fish health may influence key population-level processes, particularly those dealing with natural mortality, reproduction, and growth, which, in turn, affect stock productivity, little emphasis has been placed on the links between fish health and the management of marine fisheries. This article addresses this gap and illustrates how knowledge of fish health could provide insight for marine fisheries biologists, stock assessment modelers, and managers. The study proposes ways in which the consideration of condition indicators (energy reserves) and parasitism improves stock assessment and fisheries management, especially in situations of data shortage when standard methods cannot be applied, as is the case in many Mediterranean fish stocks. This article focuses on seven case studies of different fish species from the Mediterranean and Black Seas. Overall, and although the relationship between fish health and productivity cannot always be found or quantified, the article emphasizes the importance of the physical health of exploited stocks, particularly during critical life periods of the fish (e.g., prior to spawning, migration, or in the early life stages), as an essential element of sustainable and profitable fisheries. On the basis of these results, stock assessment and fisheries management implications are discussed.

Complete genomic sequence and taxonomic position of Eel virus European X (EVEX), a rhabdovirus of European eel

Eel virus European X (EVEX) was first isolated from diseased European eel Anguilla anguilla in Japan at the end of seventies. The virus was tentatively classified into the Rhabdoviridae family on the basis of morphology and serological cross reactivity. This family of viruses is organized into six genera and currently comprises approximately 200 members, many of which are still unassigned because of the lack of molecular data. This work presents the morphological, biochemical and genetic characterizations of EVEX, and proposes a taxonomic classification for this virus. We provide its complete genome sequence, plus a comprehensive sequence comparison between isolates from different geographical origins. The genome encodes the five classical structural proteins plus an overlapping open reading frame in the phosphoprotein gene, coding for a putative C protein. Phylogenic relationship with other rhabdoviruses indicates that EVEX is most closely related to the Vesiculovirus genus and shares the highest identity with trout rhabdovirus 903/87.

First evidence of European eels exiting the Mediterranean Sea during their spawning migration

The migration route and the spawning site of the European eel Anguilla anguilla are still uncertain. It has been suggested that the Mediterranean eel stock does not contribute to spawning because there is no evidence of eels leaving the Mediterranean Sea. To test this hypothesis, we equipped eight female silver eels from the south of France with pop-up satellite tags during escapement from coastal waters. Once in deeper water, the eels quickly established diel vertical migration (DVM) between the upper and lower mesopelagic zone. Five tagged eels were taken by predators within the Mediterranean, but two eels reached the Atlantic Ocean after six months and at distances greater than 2000 km from release. These eels ceased their DVM while they negotiated the Gibraltar Strait, and remained in deep water until they reached the Atlantic Ocean, when they recommenced DVM. Our results are the first to show that eels from Mediterranean can cross the Strait of Gibraltar and continue their migration into the Atlantic Ocean. This finding suggests that Mediterranean countries, as for other EU states, have an important role to play in contributing to conservation efforts for the recovery of the European eel stock.

Study on the life cycle of a sexually transmitted nematode parasite of a terrestrial snail

A technique for the artificial infection of the snail Helix aspersa by its parasite the nematode Nemhelix bakeri is described. The snail is relaxed by injection of an anesthetic, and 1 gravid female worm is introduced into the genitalia through the genital pore. Half of the injected snails were successfully infected. Following the course of infection over time indicated a 1:1 sex ratio, that the maximum number of progeny produced by injected female worms was 7, and that the development time of female worms was 56 days. The first generation of gravid females was found 100 days after infection. A survey of naturally parasitized snails was also conducted. The sex ratio of worms was in equilibrium, with a mean number of 2.4 larvae per female. The development time (56 days) and the body size (2.47-4.00 mm) of female N. bakeri are similar to those of a related species Cosmocercoides dukae (52-57 days and 1.66-4.34 mm), although the life cycle and biogeographic distribution for each of them are distinct.