Functions of the testicular gland in two blenniid fishes, Salaria (=Blennius) pavo and Lipophrys (= Blennius) dalmatinus (Blenniidae, Teleostei) as revealed by electron microscopy and enzyme histochemistry

The functions of the testicular gland in two different blenniid fishes, Salaria pavo and Lipophrys dulmutinus , are described by fine structural and enzyme histochemical methods. In the testes of the two fishes no mature spermatozoa are found. Sperrniogenesis occurs only until the spermatidal stage. Spermatids are released into the testicular gland. During the spawning period the testicular gland functions in differentiation of spermatids, nutrition of spermatids, and secretion of sialomucins. After spawning, the testicular gland has phagocytotic functions in resorbtion of remaining spermatids, which are transformed into lipids in the gland cells. During the interspawning period the testicular gland is a storage reservoir for lipids and phospholipids which are re-transformed into testicular gland secretion in the next reproductive season. Testicular gland cells themselves do not have steroidogenetic functions, but steroids are synthesized by interstitial cells homologous to Leydig cells in other fish. Possible explanations for the reduction of the testis in L. dalmatinus and implications of the testicular gland in taking over testicular functions are discussed.