Ciona savignyi Herdman, 1882

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 : 675

Ciona savignyi Herdman, 1882

Ciona savignyi Herdman, 1882: 236 , 237 (type locality: Japan). — Hoshino & Nishikawa 1985: 69-71, figs 1D-G, 3. — Nishikawa 1991: 33. — Cohen et al. 1998: 31, 33. — Lambert & Lambert 1998: 675-688. — Mills et al. 2000: 135.

MATERIAL EXAMINED. — USA. S of Seattle, WA, Des Moines Marina, on ropes on covered floating docks, 1 m, C. Lambert coll., 1-8.IX.1998, 3 specimens ( CASIZ 162514), 2 specimens ( USNM 1006927), 3 specimens ( MNHN P1 CIO 77).

Puget Sound, WA, Brownsville Yacht Club float, 10.IX.1998, 3 large specimens in sabellid/mussel clumps.

N of Seattle, Edmonds Marina, on covered floating docks, IX.1999, numerous individuals of all sizes.

Tacoma, WA, Yacht Club adjacent to Pt Defiance ferry dock, only on covered floats, 23.IX.2001, many. DISTRIBUTION. — Ciona savignyi is apparently native to Japan ( Nishikawa 1991). It was first recorded from the Pacific coast of North America (as C. intestinalis (Linnaeus, 1767)) by Ritter (1913) from a collection made in 1903 in Loring, Alaska ( USNM 5633). A second specimen (American Museum of Natural History 1427) was collected from British Columbia in 1937 (also identified as C. intestinalis ). Hoshino & Nishikawa (1985) reexamined these two museum specimens and determined that they were actually C. savignyi . Lambert & Lambert (1998) first noted C. savignyi on the US west coast in 1985 in Long Beach Harbor, CA. Their first Pacific NW sightings were at Des Moines Marina south of Seattle in 1998, where the species was very abundant (A. Cohen et al. 1998; Mills et al. 2000). Though absent in 1998 at Edmonds Marina north of Seattle, it appeared there in large numbers in 1999. It remains abundant at these two marinas and now extends south to Tacoma (unpublished observations).

DESCRIPTION

See Hoshino & Nishikawa (1985) for a detailed comparison of C. savignyi with C. intestinalis . Individuals are long and slender (up to 15 cm), with usually five (but may be four to six) strong longitudinal muscle bands on each side showing through the translucent yellowish/green tunic. White pigment flecks are scattered in the body wall. As indicated by Hoshino & Nishikawa (1985) for this species, there is no endostylar appendage at the base of the endostyle and no red pigment spot at the end of the sperm duct, though both are present in US west coast Ciona intestinalis . Also agreeing with the description by Hoshino & Nishikawa (1985), there is a pair of large pharyngeo-epicardiac openings very close to the opening of the esophagus, one on each side of the mid-ventral line. The siphons, both anterior, are long and divergent. The oocyte follicle cells of C. savignyi contain multiple small refringent droplets as compared with the single droplet per follicle cell in C. intestinalis ( Byrd & Lambert 2000) .

REMARKS

This species favors shaded locations such as covered floats. Even if it is abundant on these surfaces it is nearly always absent from adjacent uncovered floats.