HERMAPHRODITIC FRESH-WATER CLAMS IN THE GENUS CORBICULA PRODUCE NON-REDUCTIONAL SPERMATOZOA WITH SOMATIC DNA CONTENT

Hermaphroditic freshwater clams in the genus Corbicula produce non-red uctional spermatozoa, The DNA content of spermatozoa was almost identi cal with that of somatic cells in C. leana from Mie Prefecture, Japan. Hermaphroditic C. aff. fluminea from Saga Prefecture and C. fluminea from Taiwan also produce non-reductional spermatozoa. On the other han d, spermatozoa of the dioecious C. sandai had half the DNA found in so matic cells. Analysis of chromosome numbers suggests that C. leana (3n = 54 in somatic cells and 18 in meiotic cells) from Mie Prefecture an d C. aff, fluminea (2n = 36 in gills and 18 bivalents in meiotic cells ) from Saga Prefecture are triploids and diploids, respectively. C. le ana, C. aff. fluminea, and C. fluminea may lack either first or second meiosis, resulting in non-reductional spermatozoa. We assume that gyn ogenetic reproduction occurs in both species; maternal chromosomes are also non-reductional, and spermatozoa activate development of the egg s, but do not contribute to the offspring.