Anatomy of finfish and shellfish

Unit 8 - Urino – Genital System

8.4.2. Hag fishes
As in lampreys, a single elongate gonad is present in both sexes; the testis is irregular and lobate, without a sperm duct and sperm released into the body cavity. Unlike the lampreys, hag fishes produce large eggs with tough shells. There is no oviduct. Both eggs and sperm reach the exterior through an abdominal pore just behind the anus. In hag fishes the gonads are suspended by a mesentery from the gut.