Degeneration of the alimentary tract in sexually maturing European Anguilla anguilla (L.) and American eels Anguilla rostrata (LeSueur)

• Published in: Canadian Journal of Zoology
• Main Authors: Pankhurst, N. W., Sorensen, P. W.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1984
• Subjects: Anguilla anguilla
• Online Access: http://dx.doi.org/10.1139/z84-165; http://www.nrcresearchpress.com/doi/pdf/10.1139/z84-165

Gut morphology was examined in untreated and artifically matured European and American eels. In both species there was a decrease in gut size and gut muscle thickness with increasing sexual maturity. Hormone-treated, fully mature eels displayed advanced degeneration of the muscle layers. Total muscle thicknesses decreased from as high as 740 μm in sexually immature eels to less than 100 μm in sexually mature eels. Numbers of villi also decreased with maturity, with mature fish having relative lumenal circumferences that were less than half of those of immature fish. Epithelial structure changed with maturation and the number of mucous cells decreased. It is suggested that the degenerative changes are caused by elevated cortisol levels. Possible effects of gut changes on osmoregulation in seawater are discussed.