SPERMATOGONIA IMPLANTATION BY ANTENNULAR PENETRATION IN THE AKENTROGONID RHIZOCEPHALAN DIPLOTHYLACUS-SINENSIS (KEPPEN, 1877) (CRUSTACEA, CIRRIPEDIA)

Exposure of externae of the colonial akentrogonid rhizocephalan Diplot hylacus sinensis to cyprids of the same species competent to settle re sulted in numerous cases of attachment of the cyprids onto the surface of the externae, irrespective of the externae's size and state of mat urity. Following attachment one of the cyprid's antennules penetrates the cuticle and injects a small number of undifferentiated cells into the externa body. Before injection these cells occupy a dorsal and lat eral position within the anterior part of the cyprid's carapace and re present spermatogonia as they are probably the source of the sperm cel ls. The thousands of externae all become external simultaneously when the host crab moults. Contrary to other colonial rhizocephalans there is only a single generation.