STORAGE OF EXOGENOUS SPERM BY THE COMPOUND ASCIDIAN DIPLOSOMA-LISTERIANUM

Experimental evidence is presented for the storage of exogenous sperm by zooids of the simultaneously hermaphroditic didemnid ascidian Diplosoma listerianum. Cross-fertilized zygotes can be produced up to 1 mo after a ramet is placed in reproductive isolation. Previously published observations, considered in the light of the present data, suggest that the lumen of the ovary is the site of sperm storage. This is believed to be the first report of post-transmission storage of sperm by an ascidian. Existing records of storage of exogenous sperm in other taxa rarely involve aquatic animals in which spermatozoa are transmitted between mates singly through the surrounding water, as in D. listerianum. The potential significance of sperm storage in the mating systems of sessile aquatic invertebrates is discussed.