Antoine Orsini

SPERMIOGENESIS AND SPERMATOZOON ULTRASTRUCTURE OF NICOLLA WISNIEWSKII (DIGENEA: OPECOELIDAE), AN INTESTINAL PARASITE OF BROWN TROUT SALMO TRUTTA (PISCES: TELEOSTEI)

Spermiogenesis and ultrastructure of spermatozoon of Nicolla wisniewskii (Digenea, Opecoelidae), an intestinal parasite of Salmo trutta, were studied by electron microscopy. Spermiogenesis follows the general pattern found in the Digenea. It begins with the formation of a differentiation zone, including striated rootlets associated with 2 centrioles and an intercentriolar body. The flagella undergo a rotation of greater than 90°. Then, their fusion with the median cytoplasmic process is proximodistal and asynchronous. A peculiarity was observed before the fusion of flagella, i.e., the attachment zones joined as 2 pairs by an electron-dense bridge. The mature spermatozoon is characterized by 2 axonemes, cortical microtubules, a nucleus, 2 mitochondria, external ornamentation, and spinelike bodies. At the posterior end of flagella, the spermatozoon is also characterized by the presence of a central element of the axoneme and without the 9 microtubule doublets. These results were compared with those of the other digeneans and, in particular, with other species of Opecoelidae. It appears that the number of cortical microtubules and their localization in the spermatozoon may be an interesting feature of their phylogeny.

ULTRASTRUCTURAL STUDY OF SPERMIOGENESIS AND THE SPERMATOZOON OF CREPIDOSTOMUM METOECUS (DIGENEA: ALLOCREADIIDAE), A PARASITE OF SALMO TRUTTA (PISCES: TELEOSTEI)

Spermiogenesis and the spermatozoon of Crepidostomum metoecus, an intestinal parasite of brown trout Salmo trutta, were studied by transmission electron microscopy. Spermiogenesis begins with the formation of a differentiation zone in front of 2 centrioles associated by an intercentriolar body. Each centriole is linked to a striated rootlet, and gives rise to a flagellum. The rotation of flagella is greater than 90°; their fusion with the median cytoplasmic extension is proximodistal and asynchronous. The spermatozoon is formed after constriction of arched membranes. The spermatozoon possesses 2 axonemes of the 9 + “1” pattern, a nucleus, mitochondria, and glycogen. A major feature is the presence, in the anterior part, of external ornamentation and a lateral expansion associated with spinelike bodies. Another attribute is the presence of 2 mitochondria rather than just 1, as in most of the digenean spermatozoa. To our knowledge, this study is the first undertaken with a species of the Allocreadiidae.

Trophic transfer of arsenic and antimony in a freshwater ecosystem: a field study.

The distribution of arsenic and antimony discharges related to a past mining activity in the Bravona River and its tributary, the Presa River, was investigated. We determined levels of arsenic and antimony in the water and the biota (bryophytes, benthic macroinvertebrates and fish), along a pollution gradient. Concentrations of metalloids downstream mining wastes were significantly higher than those in reference station sites. The pattern of accumulation of arsenic in the food chain decreased as follows: macroinvertebrates>bryophytes>water>fish tissues. For antimony, the lowest concentrations were found in water. The accumulation of metals in invertebrate taxa depends on their place in the food chain, their feeding behavior, and their specific habit (lenitophilic/rheophilic species). Concentrations of both metalloids decreased with increasing trophic level.

Impact of arsenic and antimony contamination on benthic invertebrates in a minor Corsican river

The chemical and biological characteristics of a Corsican river that drains contaminated waters and sediment from an abandoned realgar mine were studied. The concentrations of pollutants such as As and Sb were found to be notably high. For example, in the Presa River, downstream the realgar mine, the mean As concentrations in the water and in the sediment were 3010 μg 1-1 and 9450 μg g-1 respectively. Species richness and abundance of benthic invertebrates decreased downstream the As mine. The disappearance of oligochaetes, leeches and a rarity of mayfly populations have been evidenced. On the contrary, a large increase in species belonging to stoneflies and gastropods was found. Some species like Baetis cyrneus, Ephemerella ignita, Sericostoma clypeatum and Ibisia marginata were more sensitive to As and Sb concentrations while others species like Ancylus fluviatilis, Isoperla insularis, Hydropsyche cyrnotica, Caenis luctuosa and Silonella aurata were less sensitive. The benthic invertebrates show different reactions in this contaminated environment, which could be explained by their feeding behaviours and certain morphological characteristics.

Arsenic accumulation in a freshwater fish living in a contaminated river of Corsica, France

The impact of arsenic (As) discharge related to a past mining activity in the Bravona River and its tributary, the Presa River, was investigated in an edible fish, the brown trout (Salmo trutta). Fish was sampled in four stations along a contamination gradient. Arsenic was measured in five organs type (operculum, gills, liver, muscle, and axial skeleton). Almost 70 years after the suspension of the mining activity, As levels in water remain high. The results indicated a strong As contamination in fish collected downstream from the mine. The operculum, liver, and gills showed the highest As concentrations whereas levels in muscle were lower. A strong positive correlation between As concentrations in water and in tissues was observed. Bioaccumulation occurred preferentially in the gills, operculum, and liver. Since As levels in tissues of S. trutta followed the pollution gradient, this species appears useful as biomonitor for metalloid accumulation.

Arsenic and antimony contamination in a riverine environment affected by an abandoned realgar mine

A minor river in eastern Corsica is highly contaminated by an abandoned realgar mine. Its As and Sb net supply to the Tyrrhenian Sea is assessed, with emphasize on their behaviour in the mixing zone, where their concentrations strongly increase, probably in relation with the organic matter content.

Distribution and status of the large Branchiopoda (Crustacea) in Corsica, France

Knowledge of the Branchiopoda of Corsica is limited. Their distribution is updated, on the basis of eight years of investigations on 20 ponds. To date, three species of Anostraca and one species of Notostraca have been reported (Tanymastix stagnalis, Chirocephalus salinus, Branchipus schaefferi and Triops cancriformis cancriformis). B. schaefferi (recorded for the first time in Corsica) occurs in a single locality, C. salinus and T. cancriformis cancriformis are limited to restricted distributions, while T. stagnalis is common in temporary ponds of Corsica. Their status is assessed according to IUCN Red List criteria. Temporary habitats are endangered by human activities and require a proper conservation management.

Statistical Analysis of the Parasites Distribution in Corsican Salmonids

The parasitofauna of 148 salmonids has been analyzed. Three host species have been recorded in the insular hydrographic network: the brown trout, Salmo trutta, the rainbow trout, Oncorhynchus mykiss and the brook trout, Salvelinus fontinalis. In order to characterize the parasites in these salmonids a Factorial Analysis of Correspondances (FCA) has been used. Four parasites species have been found in Salmo trutta, one in Oncorhynchus mykiss and one in Salvehnus fontinalis. Data on parasites species composition, and infection levels, would help improve in the biodiversity conservation by preventing the fusion of autochtonous stocks of Salmo trutta (Corsican and Mediterranean) and the introduced stocks (Atlantic) in only one stock.

Parasites Communities in Brown Trout Salmo Trutta (Pisces, Teleostei) from Corsican Rivers

A great number of rivers characterize Corsica. Salmonides are the main fishes which populate them. They are very appreciated by the fishermen and, are represented by three species in the insular hydrographic network of which an autochthonous specie, the brown trout (Salmo trutta). In the present work, we have performed the parasitofauna of this species. Previously, this work had never been carried out in Corsica. Thus, we initially drew up an inventory of the parasites found in this freshwater fish. Then, we tried to understand the differences which appeared in the composition of parasities communities of this species.