Les relations hotes-parasites dans le modele teleosteens-metacercaires de Labratrema minimus (Trematoda, Bucephalidae)

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Anguilla sp. Diseases Diagnoses and Treatments: the Ideal Methods at the Cross Roads of Conservation and Aquaculture Purposes

International audienceAnguilla anguilla, A. japonica and A. rostrata are the most fished and consumed eel species. However, these species are Critically Endangered, Endangered and Endangered respectively. A combination of factors is thought to be responsible for their decline including fisheries, climate change, habitat destruction, barriers to migration, pollution and pathogens. Among them, viruses, bacteria and parasites are causing weakening of wild eels and serious economic losses for fishermen and eel farmers. Early detection of pathogens is essential to provide appropriate responses both for conservation reasons and to limit economic losses. Classic diagnosis approaches are time consuming and invasive and usual treatments e.g. antipathogenic substances are becoming obsolete because of pathogen resistance and environmental impact problems. The need for early and noninvasive diagnostic methods as well as effective and environmentally friendly treatments has increased. Vaccine development and diet supplementation have known a growing interest since their use could allow prevention of diseases. In this review, we summarize the main pathogens-viruses, bacteria and parasites-of the three northern temperate eel species, the methods used to detect these pathogens, and the different treatments used. We discussed and highlighted the need for non-invasive, rapid and efficient detection methods, as well as effective and environmentally friendly treatments for both conservation and aquaculture purposes

Mathematical lipid correction of δ 13 C and effect of lipid extraction on δ 15 N of European eel ( Anguilla anguilla ) muscle

International audienceRationale Carbon (δ 13 C) and nitrogen (δ 15 N) stable isotope analysis is a powerful tool to investigate diverse questions in fish ecology, such as their trophic position or migration strategies. These questions appear particularly important to protect endangered European eel. However, elevated lipid content in eel muscle can bias δ 13 C values, as lipids are 13 C‐depleted compared to proteins and carbohydrates. Methods We measured δ 13 C and δ 15 N values of bulk and lipid‐free samples of eel muscle. Lipid‐free samples were obtained after the extraction of lipids with cyclohexane. Lipid‐corrected δ 13 C values, using five different mathematical equations based on bulk δ 13 C values, were compared to lipid‐free δ 13 C values. We also evaluated the effect of lipid extraction on δ 15 N values. The analyses were based on linear regression performed on 333 individuals captured in nine lagoons and four rivers. Results Independently to the capture site or habitat (river or lagoon), the predicted lipid‐corrected δ 13 C values were highly consistent with the measured lipid‐free δ 13 C values ( R 2 > 0.90). The application of specific equations for each habitat or capture site only slightly increases these R 2 (1.5% or less). The lipid extraction treatment significantly decreased by 0.2‰ the δ 15 N values compared to bulk samples. Conclusions Given the excellent prediction of mathematical equations and the small decrease of δ 15 N values after lipids extraction, we propose to use mathematical correction to estimate δ 13 C values of eel muscle. As the habitats or sites did not strongly influence the results, the coefficients from our study can be applied to other studies on European eel

Links between parasitism, energy reserves and fecundity of European anchovy, Engraulis encrasicolus, in the northwestern Mediterranean Sea

13 pages, 8 figures, 2 tablesThe European anchovy, Engraulis encrasicolus L. 1758, is one of the most sought-after target species in the northwestern Mediterranean Sea. However, this stock currently consists of small individuals, and landings are reported to have decreased considerably. The main purpose of this study was to assess, for the first time, the interrelationships between size, fecundity, energy reserves and parasitism in female anchovies, in order to analyse the potential implications for the health of northwestern Mediterranean anchovy stocks arising from the current shortage of large individuals. Results revealed that smaller individuals show lower fecundity, lower lipid content and a higher intensity of certain parasites. As it is known that smaller individuals now predominate in the population, the relationships found in this study indicate that the health of anchovies from the northwestern Mediterranean is currently impairedPeer reviewe

Proctophantastes nettastomatis (Digenea: Zoogonidae) from Vanuatu deep-sea fish: new morphological features, allometric growth, and phenotypic plasticity aspects

The present paper deals with Proctophantastes nettastomatis (Digenea: Zoogonidae; Lepidophyllinae) found in the intestine of three species of deep-sea fish, Dicrolene longimana (Ophidiidae, Ophidiiformes), Bathyuroconger sp. (Congridae, Anguilliformes), and Venefica tentaculata (Nettastomatidae, Anguilliformes). The fish were collected near the islands of Espiritu Santo, Erromango, and Epi, respectively, in the archipelago of Vanuatu (Southern Pacific Ocean) at depths ranging from 561 to 990 m. Morphological and histological analyses showed that the Vanuatu specimens differ from Proctophantastes abyssorum, Proctophantastes gillissi, Proctophantastes glandulosum, Proctophantastes infundibulum, and Proctophantastes brayi but are close to P. nettastomatis discovered in Suruga Bay, Japan. P. nettastomatis is redescribed based both on the observations of our specimens and of the Japanese holotype and paratype. The morphological variability of the species is described. Morphometric data allowed the identification of positive allometric growth for the hindbody, negative allometric growth for the ventral sucker, and a growth phenotypic plasticity between Ophidiiformes and Anguilliformes definitive hosts

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

International audienceThe 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. Although European eels are found in fresh and brackish waters throughout Europe and North Africa, they escape to sea to spawn towards the end of their lives. European eels, like American eels, are presumed to spawn in the Sargasso Sea, where eel larvae of both species are found in the greatest abundance 1–3. The evidence for a single spawning area is strong and modern genetic studies indicate a panmictic species 4,5. European eels therefore need to undertake a spawning migration of at least 5000 km from the western margin of the continental habitat in Europe; this distance is much greater for eels escaping from more easterly locations, including those in the Baltic and Mediterranean Seas. However, despite the advent of marine remote sensing, genetic and otolith analyses, electronic tagging, and investigative computer modelling in the century since Schmidt

Links between parasitism, energy reserves and fecundity of European anchovy, Engraulis encrasicolus, in the northwestern Mediterranean Sea

International audienceThe European anchovy, Engraulis encrasicolus L. 1758, is one of the most sought-after target species in the northwestern Mediterranean Sea. However, this stock currently consists of small individuals, and landings are reported to have decreased considerably. The main purpose of this study was to assess, for the first time, the interrelationships between size, fecundity, energy reserves and parasitism in female anchovies, in order to analyse the potential implications for the health of northwestern Mediterranean anchovy stocks arising from the current shortage of large individuals. Results revealed that smaller individuals show lower fecundity, lower lipid content and a higher intensity of certain parasites. As it is known that smaller individuals now predominate in the population, the relationships found in this study indicate that the health of anchovies from the northwestern Mediterranean is currently impaired

Acute loss of European silver eel fitness by introduced (vs native) parasitic helminthes threatening spawning success

International audienceHelminth parasites were studied in 149 silver eels from five sites in northern Europe. In total, 88% were infected by 12 species including Monogena, Cestoda, Nematoda, and Acanthocephala. Anguillicoloides crassus was most common (56%), then Acanthocephalus clavula (30%) and Pseudodactylogyrus spp. (17%). The body condition (BC) was negatively influenced by the abundance of the introduced Pseudodactylogyrus spp. but not by the other parasite taxa. However, the introduced A. crassus was considered as a severe pathogen based on previous data, whereas the native A. clavula was supposed to have limited impact. Eels from Stockholm Archipelago (Sweden) were the less parasitized (30% vs ≥ 90% for other sites) with no parasites in gills. Burrishoole (Ireland) differed by absence of A. crassus and high prevalence of A. clavula (84%) but without consequences on BC. Gudenaa (Denmark), Corrib (Ireland) and Frmur (France) were close due to high prevalence of A. crassus (≥ 89%). Gudenaa and Corrib were the most similar because Pseudodactylogyrus spp. was also highly prevalent (≥ 60%) whereas absent in Frmur. Our results suggest that introduced parasites may threaten the spawning success of migrant silver eels from Gudenaa, Corrib and Frmur, but not of those from Stockholm Archipelago and Burrishoole

Health and reproduction of red mullet, Mullus barbatus, in the western Mediterranean Sea

International audienceThe reproductive and general health of exploited fish stocks is an essential element of sustainable and profitable fisheries. The main purpose of this study was to assess the relationships between reproduction and two important parameters of fish health (parasitism and energy reserves) in female specimens of red mullet, Mullus barbatus, from the western Mediterranean Sea. We present new data for this species on (i) the prevalence and intensity of infection by metazoan parasites; (ii) the total lipid content in muscle and gonads as a measure of condition and (iii) fecundity and egg quality as a measure of their reproductive capacity. The results show that M. barbatus is a batch spawner with an income breeding strategy, an asynchronous development of oocytes and indeterminate fecundity. The results also indicate that the three most abundant and prevalent parasites significantly affect the condition and reproduction of M. barbatus. Specifically, the digenean, Opecoeloides furcatus, causes a reduction in the female’s energy reserves, while the nematodes, Hysterothylacium fabri and H. aduncum, produce a rise in egg production but impair egg quality. These implications of the relationships between parasitism, fish health and fish reproduction should be taken into consideration in the assessment and management of exploited species