Ascidia paratropa (Huntsman 1912)

Attached to assorted hard substrata

Depth Range: Rarely very low intertidal, more commonly subtidal, extending to about 80m depth in well-circulated waters

A large solitary ascidian, body roughly cylindrical, taller than wide, 5-15cm tall. Clear, transparent, colorless tunic with pink-washed areas covered with prominent warty tubercles. Siphons close together at one end

How to Distinguish from Similar Species: Molgula pacifica also is large and solitary, has a transparent tunic, and is taller than wide, but M. pacifica usually has foreign material such as algae incorporated into the tunic, has red on the siphons, and has no scattered large papillae as seen on A. paratropa.

Biology/Natural History: Ascidia paratropa probably breeds only in the summer, and it does not brood its eggs. Its diploid chromosomes complement is 18. It can be hybridized experimentally with A. callosa. The egg envelopes must be removed manually. With this precaution about two-thirds of A. callosa eggs and one-half of A. paratropa eggs fertilized by the other species develop into only slightly distorted tadpoles; a few settle and metamorphose to zooids that appear functionally competent except for aberrant guts. An attempt to raise offspring through sexual maturity has not been made yet. The tunic of A. paratropa, glasslike in its transparency, has received some study. It is very largely sea water, the organic matter constituting only .8 percent of tunic wet weight. About half the organic matter is carbohydrate resembling plant cellulose, and about half is protein. Investigation of the brain of A. paratropa shows the presence of neurosecretory cells of the sort characteristic of the Ascidian suborders Aplousobranchia and Phlebobranchia

Geographical Range: Unga Strait at least to southern Monterey Co.