Lissoclinum pacificense ( Kott, 1981 )

Kott, Patricia, 2004, New and little-known species of Didemnidae (Ascidiacea, Tunicata) from Australia (part I), Journal of Natural History 38 (19), pp. 731-774 : 768-769

Lissoclinum pacificense ( Kott, 1981)

( figure 20C )

Echinoclinum pacificense Kott, 1981: 193 (part, specimens from Viti Levu).

Lissoclinum pacificense: Kott, 2001: 295 .

Distribution. New records: Queensland (Hinchinbrook I., QM G300973). Previously recorded (see Kott, 2001): Fiji ( Viti Levu).

Description. The colony is said to have been yellow and amorphous in life. In preservative the test is soft transparent and small groups of zooids surround a solid mass of test, their abdomina completely, and the thoraces partially, embedded in it. Zooids are also surrounded by a thin, close capsule of spicules that leaves only the dorsum of the thorax exposed to the common cloacal cavity. The spicules are tetrahedral to six-rayed stars, the arms formed from many long crystals crowded together. Maximum-sized spicules have up to 0.05 mm between the tips of adjacent rays. In the centre is a mass of similar, but shorter spicule rays often graded in length and sometimes broken up into short, crowded needles, forming a brush-like collar around the base of the long, thick arms. Zooids are as previously described, with an entire (undivided) testis.

Remarks. The thin layer of spicules encapsulating the zooids is similar in L. punctatum Kott, 1977 , L. roseum Kott, 2001 , L. limosum Kott, 2001 and L. calycis Monniot, 1992 . However, L. roseum and L. punctatum have globular spicules, and only in L. calycis , L. limosum and L. pacificense do the spicules have rays like those in the verrilli group of species (see Kott, 2001). In this group, L. taratara Monniot and Monniot, 1987 from French Polynesia, Indonesia and Lizard Island (see Kott, 2001), L. tuheiavae Monniot and Monniot, 1987 from French Polynesia, and L. vulgare Monniot, 1992 have similar spicules and also have undivided testes, but their spicules are scattered throughout the colony rather than encapsulating the zooids. Further, the spicules are either larger ( L. taratara , L. tuheiavae ) or smaller ( L. vulgare ) than those of the present species. Lissoclinum calycis and L. limosum , with similar spicules encapsulating the zooids, appear to be most closely related to the present species. The former has smaller larvae with fewer lateral ampullae than the present species and the central rays of the spicules divided into a brush-like mass of needle-like rays. In L. limosum the larval trunk is only slightly shorter than that of the present species but it has many more lateral ampullae per side and the spicules lack variation in the length and thickness of their rays.

Lissoclinum guinense Monniot and Monniot, 2001 is another related species and unequivocal distinguishing characters of colonies and zooids have not been detected. However, the distribution of spicules is not reported and they are known from the micrograph of only one ( Monniot and Monniot, 2001: figure 67A). Although that spicule resembles some in the present species, it is within the range (size and form) of spicules of L. calycis . The relatively short larval trunk with four pairs of ectodermal ampullae resembles L. calycis rather than the present species (which has a larval trunk 1.2 mm long and five pairs of ectodermal ampullae). Although the larvae of L. guinense are said to lack blastozooids, it is apparent from Monniot and Monniot (2001: figure 66B) that better-developed embryos may be found to contain buds, as in L. calycis , which appears to be the senior synonym of L. guinense . Larvae of L. tuheiavae are about the same size as L. calycis and L. guinense and also have only four pairs of ectodermal ampullae. However, the spicules and their distribution are different.

Figures

FIG. 20. Lissoclinum levitum (SAM E3204): (A) abdomen; (B) spicules. Lissoclinum pacificense (QM G300973): (C) spicules. Lissoclinum patella (ZMA TU500): (D) spicules. Scale: (A) 0.1 mm.