Abstract
Species differences of external features and cellular components of the Leydig and epigonal organs in the elasmobranchs were studied macroscopically and histologically using 5 species of Japanese fishes.The mutual relationship between the epigonal organs and the gonads is roughly divided into 3 types, while no noticeable difference is detected in the Leydig organs among 5 species.As the posterior lobe of the epigonal organ is elongated to reach the area of rectal gland, the term “subgonal” is proposed to the cases of smoothhound and its relatives.Both organs consisted of many eosinophilic granulocytes in various immature stages, and a small number of heterophilic granulocytes, lymphocytes and plasma cells.The cells with large vacuoles ori-ginated from the granulocytes in the process of degeneration were also found in addition to some lymphoid and/or blast cells.Hassall's corpuscle-like structures were infrequently demonstrated in both Leydig and epigonal organs of the sting ray and skate.The presence of lymphomyeloid cells in both organs may support their possible role in the immune response and the process of inflammation.
