Polyclinum corbis, KOTT, 2003

KOTT, PATRICIA, 2003, New syntheses and new species in the Australian Ascidiacea, Journal of Natural History 37 (13), pp. 1611-1653 : 1626-1627

Polyclinum corbis sp. nov.

Polyclinum tsutsuii: Kott, 1992a: 463 ; not Tokioka, 1954: 240; 1967: 47.

Distribution. Type locality: Western Australia (W. of Cervantes, coll. L. Marsh, April 1990, holotype WAM 476.91; paratype WAM 475.91).

Description. (See Kott, 1992a: 463, figure 34a, b.) Sessile colonies, rounded to wedge-shaped lobes with a light, sometimes patchy sandy superficial coating interrupted where zooids open to the surface. Sand sparse in internal test. Dark anterior surfaces of zooids, arranged in crowded circles, show through the surface test.

Zooids, impossible to remove from the test, are about 3 mm long overall, with a small six-lobed branchial aperture, a circular atrial aperture directed anteriorly and a strap-like atrial lip with a serrated tip projecting from the body wall anterior to the opening. Eight short, fine muscle bands on each side radiate from the branchial aperture and fade half-way down the thorax. The branchial sac has 14–16 rows of about 18–20 stigmata per row and about the same number of tongue-shaped papillae on each transverse vessel. The gut forms a horizontal loop posterior to the thorax. It is twisted to the left, as is usual in this genus. A tear drop-shaped posterior abdomen with a finely tapering vascular stolon is constricted off from the abdomen by a narrow neck. The holotype and paratype have about three embryos in a spherical brood pouch constricted off from the thorax outside the anus. Larvae are small, the trunk to 0.5 mm long. Four tall conical median ampullae alternate with the three stalked adhesive organs and four shorter, rounded lateral ampullae are on each side. Epidermal ampullary vesicles branch off a stalk projecting posteriorly from the anterior end of the endostyle on each side of the dorsal mid-line and another group of vesicles branches off a stalk projecting posteriorly from each side of the middle of the ventral mid-line. The tail is wound almost three-quarters of the way around the trunk. Tips of both lateral and median ampullae have caps of columnar epidermal cells.

Remarks. Polyclinum tsutsuii Tokioka, 1954 , described originally from the tropical Tokhara Is of Japan, forms small, dark, encrusting colonies with zooids in circular systems, 10–12 rows of 20–25 stigmata, a similar number of tongue-shaped papillae on the transverse vessels, a tongue-shaped atrial lip (serrated at the tip) from the body wall anterior to the circular aperture and 8–14 testis follicles in a posterior abdominal sac. Although F. and C. Monniot (1996) imply that it is immature, Tokioka (1954: figure 2) shows male and female gonads and what appears to be an embryo being incubated in the atrial cavity. Kott (1992a) found similar zooids and colonies from tropical north-eastern and north-western Australia, and since those from the north-west have embryos being incubated in a brood pouch, she assumed that (despite Tokioka’s type specimen) the brood pouch was a characteristic of P. tsutsuii and that, accordingly P. pute Monniot and Monniot, 1987 from French Polynesia was a junior synonym. However, Monniot and Monniot later (1996) pointed out that the specimen of P. tsutsuii from the Palau Is (Tokioka 1967), like the type, had embryos free in the atrial cavity and that accordingly P. tsutsuii: Kott, 1992a (which has a brood pouch) is a junior synonym of P. pute Monniot and Monniot, 1987 but not of P. tsutsuii . However, Polyclinum tsutsuii: Kott, 1992a < Polyclinum corbis n. sp. is a third species. Like P. pute it has a brood pouch but is distinguished by its conical median ampullae (absent from P. pute larvae) alternating with the three adhesive organs and its 14–16 rows of stigmata (rather than 10–12).

Polyclinum tsutsuii: Tokioka, 1967 from the Phillipines, with about 50 male follicles and the atrial tongue from the anterior rim of the opening (like P. pute ) may be yet another species (see P. saturnium ). It has median and lateral ampullae like P. corbis but like P. tsutsuii it lacks a brood pouch. Other specimens from Japan and Korea with a brood pouch (see P. saturnium: Tokioka, 1962 and P. saturnium: Rho, 1966, 1971 , 1975) are more likely northern temperate species than synonyms of P. pute .

In Polyclinum tsutsuii the dark brown test, possibly like P. pute , has many dark pigment cells crowded in it. The present species from Australia has brown zooids but the test is translucent. A specimen from Noumea (Monniot, F., 1987) is a sand-impregnated cushion and probably is not conspecific with any of the species discussed here.

The relationships between these species is summarized in the following couplets, which replace the couplets 3 to 4 in the key to the Polyclindae (Kott, 1992a):

3 Stigmata in more than 12 rows (14–16)............ 3a – Stigmata in not more than 12 rows (10–12)........... 4

3a Zooids in single system per colony lobe; no brood pouch..... P. orbitum – Zooid not in single system per colony lobe; with a brood pouch.. P. corbis n. sp.

4 Brood pouch present............... P. pute – Brood pouch not present................ 4a

4a Median larval ampullae present............ P. saturnium – Median larval ampullae not present........... P. tsutsuii