A. Jespersen et J. Lutzen, Sex, seminal receptacles, and sperm ultrastructure in the commensal bivalve Montacuta phascolionis (Veneroida; Galeommatacea), ACT ZOOL, 81(1), 2000, pp. 69-75
It is argued that the paired structures in adult Montacuta phascolionis pre
viously claimed to be testes are seminal receptacles. The receptacles in 3.
0 mm long females are filled with sperm cells or spermatids. A 2.0-mm long
specimen had a well-developed testes exhibiting ripe sperm. It is concluded
that the species is a protandrous hermaphrodite and that the previously de
scribed dwarf males are rather complemental males. The ultrastructure of th
e sperm cells is described and compared with that of the sperm of related s
pecies.