Sciences marines : recherche et développement

Abstrait

Freshwater Eels' Origins in the Deep Ocean

Goverse E

Only fresh eels-genus Anguilla, that has 16 species and three subspecies-spend the foremost of their lives in fresh throughout their catadromous life cycle out of the over 800 species of eels that structure the order Anguilliformes. However, as a result of their spawning grounds area unit call at the open ocean, they migrate back to their explicit breeding grounds within the ocean, that area unit of thousands of kilometres away. Thanks to the fresh eels’ ambiguous phyletic position at intervals the primarily marine anguilliforms, the biological process genesis of this uncommon behavior remains a mystery. supported the phyletic study of entire mitochondrial ordering sequences from 56 species encompassing all 19 anguilliform families, we have a tendency to offer compelling support for the deep oceanic origin of fresh eels. The fresh eels area unit the top members of the anguilliforms and belong to a monophyletic cluster with several species of oceanic mid water eels. Moreover, the reconstruction of the expansion habitats on the ensuing tree once and for all shows that the fresh eels originated within the deep ocean’s mid water. The japanese eel’s recent assortment of mature adults within the higher mid water of the Pacific Ocean demonstrates robust agreement with this, indicating that they need maintained their biological process origin as a behavioral feature in their spawning regions.

Even once a number of the fresh eels’ offshore spawning grounds were known nearly a century past, the natural fruitful ecology of those fish remained a mystery. During this study, we have a tendency to use collections of eggs, larvae, and spawning-condition adults of two species within their shared spawning home ground in the Pacific to look at the spawning ecology of fresh eels for the primary time. Female person Japanese eels and big patterned eels had polycyclic ovaries, which indicate that fresh eels can spawn over once during a season. The primary assortment of Japanese eel eggs discovered on the brink of the West Mariana Ridge, wherever adults and freshly born larvae were additionally discovered, demonstrates that spawning happens around phase of the moon times throughout the spawning season. This kind of spawning might scale back predation and facilitate fruitful success.