Molgula Forbes & Hanley, 1848

Lambert, Gretchen, 2003, New records of ascidians from the NE Pacific: a new species of Trididemnum, range extension and redescription of Aplidiopsis pannosum (Ritter, 1899) including its larva, and several non-indigenous species, Zoosystema 25 (4), pp. 665-679 : 676-677

Genus Molgula Forbes & Hanley, 1848 Molgula manhattensis ( De Kay, 1843)

Ascidea manhattensis De Kay, 1843: 259 (type locality: NE United States).

Molgula manhattensis – Verrill 1871: 54. — Van Name 1945: 385-389, figs 271-273. — Monniot 1969: 191-196, figs 7-9 (for a detailed description and extensive synonymy). — Kott 1985: 379, 380.

MATERIAL EXAMINED. — Canada. Vancouver I., French Creek Marina, B.C., 4.IX.1998, 4 small specimens on tire.

USA. Puget Sound, Shelton Yacht Club floats, 9.IX.1998, many, all sizes.

Willapa Bay, WA (see A. Cohen et al. 2001), 22. V.2000, several from 3 sites (not abundant).

DISTRIBUTION. — Worldwide now in temperate waters: Japan, Australia, US east and west coasts, Europe.

DESCRIPTION

Globular, usually 4 cm or less in diameter, with a soft, thin, translucent, colorless tunic through which some of the internal organs can occasionally be seen. Usually, however, the tunic is covered by greyish fine sediment trapped in the numerous small tunic hairs. The divergent siphons are fairly close together at the anterior end; as in other molgulids the oral siphon has six lobes, the atrial four. There are six branchial folds per side. The spiral stigmata are usually quite broken up and irregular. The intestine makes a closed deep loop, somewhat U-shaped but more pronounced; “the whole loop is bent in a curve of about threefourths to four-fifths of a circle” ( Van Name 1945). This species is a free spawner; the embryos form swimming larvae.

REMARKS

See Van Name (1945), Monniot (1969) and Kott (1985) for a detailed description of the morphology of this species and its probable routes of anthropogenic transport. Individuals often occur by the millions in dense clumps on artificial structures in harbors, especially where the salinity is 27-30 parts per thousand.