Notes on the Egg Deposition, Larval Migration and Intermediate Host of the Nematode Anguillicola crassa Parasitic in the Swimbladder of Eels

Abstract

A. crassa deposits its thin-membraned eggs already containing fully formed sheathed-larvae in the lumen of the swimbladder. Occasionally eggs are released in large numbers by rupture of the body wall and uterus. The sheathed-larvae hatched out in the lumen of the swimbladder are passed through the pneumatic duct and digestive tract into the water, where they can survive for some months without shedding the sheath. Part of the larvae invade the wall tissues of the swimbladder, though their fate is not known.The larvae eaten by the copepod Eucyclops serrulatus pierce the intestinal wall and penetrate the body cavity within a few days at the latest, in which they start to grow immediately. The larvae moved to the body cavity have no sheath. On the contrary the larvae eaten by Sinodiaptomus chaffanjoni can penetrate the body cavity, but no copepod habouring the larvae in its body cavity can be found 24 hours after infection. This fact is possibly due to death of the infected copepods.