PubMed · 4581562
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S A Shukoliukov. [Visual pigments in fish].. https://pubmed.ncbi.nlm.nih.gov/4581562/
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Genes encoding spermatogenesis-related substance (eSRSs) show unique expression patterns during spermatogenesis. To analyze their function, we developed a new assay system using gene transfer techniques combined with coculture of the eel germ-somatic cells. First, we investigated the efficacy of in vitro electroporation transfer of gene into germ-somatic cell pellets using green fluorescent protein (GFP) gene. Second, in order to define the function of the eSRSs, we electrophoretically transferred eel spermatogonial stem cell renewal factor (eSRS34) and eel spermatogenesis-preventing substance (eSRS21) genes into germ-somatic cell pellets. Presence of the transferred cDNA was examined by reverse transcription-polymerase chain reaction (RT-PCR). Furthermore, proliferating cells were detected histologically, after labeling with BrdU. Transfer of the eSRS34 gene induced spermatogonial stem cell renewal in the pellets. Moreover, 11-ketotestosterone (11-KT) treatment stimulated the proliferation of spermatogonia, which resulted in the appearance of late type B spermatogonia in the pellets. The proliferation of spermatogonia by 11-KT stimulation was suppressed by transfer of the eSRS21 gene. These results indicate that the transferred eSRS34 and 21genes were functional in the pellets. Thus, an efficient in vitro gene transfer technique for coculture system of germ and somatic cell of Japanese eel was established.
Adult trematodes of the genus Stegodexamene Macfarlane, 1951 were recorded from the intestines of two species of freshwater eels, the Pacific short-finned eel Anguilla obscura Günther and the speckled longfin eel Anguilla reinhardtii Steindachner from the Pouembout and La Foa Rivers, New Caledonia, South Pacific. They were identified as Stegodexamene anguillae Macfarlane, 1951, a species previously reported only from eels in New Zealand. The morphology of adult S. anguillae seems to be practically identical with that of the later described Stegodexamene callista Watson 1984 from eels in Australia. The finding of S. anguillae in A. obscura and A. reinhardtii in New Caledonia represents new geographical and host records. In addition to this trematode, two larval specimens of a cestode of the order Proteocephalidea were found in the intestine of one A. obscura from the Pouembout River. No monogenean was found in eels of New Caledonia.
The European eel is a vulnerable fish by its complex life cycle, by the impact of pollution of the near total of freshwater aquatic environments, and by the gravity and the diversity of its parasites (nematodes, cestodes, trematodes, the Copepoda, Coccidia...). It is classified in the red book of threatened species. The anguillulose is the principal parasitic pathology of an eel either in the natural environment or in the aquaculture. The eels taken in the three zones of the Sebou estuary of varied environmental conditions were dissected for the research of parasites. Of the fish, 85.7% are infested upstream of the estuary, whereas only 71% shelter this parasite in their swim bladder, with an abundance of 2.09 per fish downstream and 83.8 in zone 2. The present study suggests the development stage of the fish, and therefore its diet, has an influence on the parasitic infestation. The estuaries and the lagoons constitute a very significant medium for the safeguarding and the disinfection of parasitized eels.