Eudistoma laysani ( Sluiter, 1900 )

Monniot, Françoise, 2009, Some ascidians from Indonesian marine lakes (Raja Ampat Islands, West Papua), Zootaxa 2106, pp. 13-40 : 26-27

Eudistoma laysani ( Sluiter, 1900)

( Figure 11 A,B)

Distoma laysani Sluiter 1900: 9 , pl.1fig.2–pl.2 fig.7.

= Eudistoma laysani: Tokioka, 1967:119 fig. 42

= Eudistoma toealensis: Millar, 1975:222 fig. 14; Monniot & Monniot, 1996: 194 fig.32, pl. 5E. not Eudistoma laysani: Millar, 1975

Material. Indonesia. West Papua, Gam Island, Bay Besir, War Manak, Mangrove fringing reef, 00°29.877’S – 130°35.947’E, 0.25m, 06/XII/2007, coll. L.J. Bell, WMM 0 0 7 ( MNHN A3 EUD 341); West Papua, Gam Island, Danau Hidden Gam marine lake 00°26.959’S – 130°30.071’E, 0–1m, 09/XII/2007, coll. L.J. Bell and L.E. Martin, DHG 0 17 ( MNHN A3 EUD 342). West Papua, Gam Island, Danau Nine Gam marine lake,, 00°26.970’S – 130°29.149’E, 0.5m, 02/XII/2007, coll. L.J. Bell and L.E. Martin, DNG 0 0 3 ( MNHN A3 EUD 343). East Kalimantan, Maratua Island, Danau Tanah Bamban, marine lake,, 2°13.825’N – 118°34.785’E, 26/X/2003, 0.5m, coll. L.J. Bell, TBM001 ( MNHN A3 EUD 274). Palau, Ngeruktabel Island, Uet era Ngchas, marine lake, 7°15.24’N – 134°20.64’E, 0.5m, 15/XI/2001, coll. Coral Reef Research Foundation, 0 CDN 8189L ( MNHN A3 EUD 310).

The lobes of the colony have an orange peduncle in life and a translucent colourless expanded head ( Fig. 11 A). The siphons are slightly protruding; they have no pigment spots. The branchial sac is rectangular with an average of 20 stigmata in the second half row, the first row is curved dorsally. The abdomen is ten times longer than the thorax in some relaxed zooids, but it is short in other zooids of the same colony. A single mature larva occurs in the peribranchial cavity, sometimes accompanied by an embryo. The trunk measures 1.1mm and has 3 adhesive papillae separated by large vesicles with an irregular dentate tip ( Fig. 11 B). The tail has the same length as the trunk. This larva corresponds to those figured for E. toealensis by Millar (1975 fig. 14e) and Monniot & Monniot (1996 fig. 32C).The latter is considered here as a junior synonym of E. laysani .

Millar (1975) identified as E. laysani an ascidian with a larva 0.5mm long, saying at the same time that his identification was uncertain, so it may be E. viride . Kott (1990) following Millar (1975) named E. laysani specimens with a small larva but this species is certainly E. viride as she also indicated “in preservative the pigment occasionally persists”.

Figures

FIGURE 11. Eudistoma laysani: A, colony; B, stained larva, scale bar: 0.5 mm. Eudistoma viride: C, colony; D, stained larva, scale bar = 0.25 mm.