Lissoclinum laneum, Kott, 2010

Kott, Patricia, 2010, New and little-known species of Didemnidae (Ascidiacea, Tunicata) from Australia (part 2), Journal of Natural History 38 (26), pp. 2455-2526 : 2510-2514

Lissoclinum laneum sp. nov.

( figure 13A )

Distribution. Type locality: South Australia (Port Victoria Jetty, Yorke Peninsula, 3–4 m, coll. K. Gowlett Holmes, 3 May 1998, holotype SAM E2923).

Description. The colony is a soft, translucent aspicular sheet, the test with a cotton-wool consistency. Zooids are seen through the test, embedded along the sides of the common cloacal canals. Spicules were not detected, although there are varying-sized spherical clumps of irregular morulae or smooth plate-like to rounded bodies on each side of the thoraces and in the test around the zooids. Clumps of similar bodies form a half collar on each side of the duodenum at the base of the stomach, and they also are found in abundance around the common cloacal apertures and in the surface test. Zooids are large, with a moderately long branchial siphon and a sessile atrial aperture exposing much of the large branchial sac to the common cloacal cavity. About 12 stigmata are in the anterior row. An oesophageal muscle is around the oesophageal neck, but a retractor muscle was not detected. A small egg is in a sac attached to the abdomen by a narrow neck. The testis is spherical and undivided and the proximal part of the straight vas deferens is expanded into a seminal vesicle.

Remarks. The species has plate-like and morula bodies in the test that resemble those in the larval test of many Lissoclinum spp. , as well as in the adult test of Lissoclinum concavum Kott, 2001 (causing it to be cloudy). The homologue of the half collar of morula bodies around the duodenum at the base of the stomach is not known, although the ball of similar bodies on each side of the thorax appears to be homologous with the lateral organs. Similar clumps of morula bodies are scattered in the test of Diplosoma fecundum and D. ferrugeum Kott, 2001 , and other Diplosoma species such as D. velatum Kott, 2001 superficially resemble this aspiculate colony. However, Diplosoma spp. usually have zooids suspended in the common cloacal cavity in strands of test, rather than being embedded in the test along each side of the common cloacal canals.

Lisssoclinum calysis Monniot, 1992 has the egg in a sac attached to the body wall as in the present species, lacks a retractor muscle, has an undivided testis and may be related. However, it has distinctive spicules that separate it from the present characteristically aspicular species. Lissoclinum notti Brewin, 1958 from New Zealand has a similar undivided testis and the ovary constricted off from the abdomen, but it is also distinguished from the present species by its spicules.

Lissoclinum levitum Kott, 2001

( figure 21D )

Lissoclinum levitum Kott, 2001: 307 ; 2004.

Distribution. Previously recorded (see Kott, 2001, in press): South Australia (Ward I.). New record: South Australia (Kangaroo I., SAM E3219).

Description. The newly recorded colony is mauve, translucent with sparse spicules evenly distributed in a surface and a basal layer. Only occasional spicules are in the remainder of the colony. The surface spicules are slightly more crowded in clumps in each of the branchial lobes than they are in the remainder of the surface, thus creating a daisy-like pattern. Common cloacal openings, on large flaccid cylindrical protrusions here and there on the surface, are also ringed in white. Spicules are less than 0.03 mm diameter, burr-like with numerous pointed or irregular ray tips.

Zooids cross the vast common cloacal cavity in groups of about six, each zooid attached separately at the surface but joined to the basal test by a single common ligament. They have about eight stigmata in the anterior row. A small lateral organ is on each side of the endostyle opposite the middle transverse vessel. Two male follicles are present. The proximal end of the vas deferens is often swollen into a seminal vesicle. Zooids contain the usual dark haemocoel cells.

Remarks. The newly recorded specimen differs from the type material in its more extensive common cloacal cavity, the abdomina previously being found embedded in the basal test. Nevertheless, the spicules and their distribution, the colour of the colony and the form of the zooids are identical.

Lissoclinum limosum Kott, 2001

Lissoclinum limosum Kott, 2001: 308 ; 2002c: 42.

Distribution. Previously recorded (see Kott, 2001, 2002c): Queensland (Capricorn Group, Swain Reefs), Northern Territory (Darwin). New record: Northern Territory (Weed Reef II, QM G308660).

Description. The newly recorded colony is not in good condition. The test is soft and contains dark pigment cells around the zooids encapsulated in white spicules. Spicules, colony and zooids are as previously described.

Remarks. These fragile, thin colonies, with the white capsule of spicules around each zooid showing through the black, slightly translucent test, are characteristic of this species.

Lissoclinum multifidum ( Sluiter, 1909)

Leptoclinum multifidum Sluiter, 1909: 83 .

Lissoclinum multifidum: Kott, 2001: 311 and synonymy; 2002c: 42.

Distribution. Previously recorded (see Kott, 2001, 2002c): Northern Territory (Darwin, Port Essington), Indonesia, Gulf of Thailand, Mauritius. New record: Northern Territory (Plater Rock, QM G308677).

Description. The colony is soft and encrusting, with long rounded branches growing over the coralline rubble substratum. It is orange in life and white in preservative. Rounded prominences with large terminal common cloacal apertures are relatively evenly spaced along the centre of the rounded almost cylindrical branches. The common cloacal apertures are large with smooth transparent rims. Spherical, white granular bodies to 0.1 mm diameter are in patches in the surface test.

Zooids are in clumps surrounded by deep trench-like common cloacal cavities that here and there are continuous with the vast posterior abdominal common cloacal cavities that interrupt the zooid layer from the basal test. Larvae are being incubated in the zooid layer of test rather than in the basal layer. Zooids are large with 10 stigmata in the anterior row, seven male follicles, a straight vas deferens and a long straight retractor muscle. Larvae have a trunk 0.8 mm long with the tail wound three-quarters of the way around it. Three lateral ampullae are each side of the three antero-median adhesive organs. The blastozooid is separated from the oozooid by a deep anterior groove. The sensory vesicle with ocellus and otolith is also separated from the oozooid by a marked constriction.

Remarks. The specimen conforms with others assigned to this species. Kott’s statement that the abdomina are embedded in the basal test is incorrect; they are in the zooid layer of test, separated from the basal test by the posterior abdominal common cloacal cavity. The aspiculate nature of the colony, the extensive common cloacal cavity, the soft test, numerous testis follicles and the large larva, with deeply separated blastozooid and oozooid at the base of the lateral ampullae, and the sensory vesicle constricted off from the oozooid, is distinctive, resembling a Diplosoma larva more closely than most other Lissoclinum larvae. In this and other characters it resembles other Lissoclinum species in the aureum group, which are separated from Diplosoma by the presence of spicules and their numerous testis follicles.

Lissoclinum ostrearium ( Michaelsen, 1930)

( figure 21E )

Diplosomoides ostrearium Michaelsen, 1930: 526 .

Lissoclinum ostrearium: Kott, 2001: 314 and synonymy.

Distribution. Previously recorded (see Kott, 2001): Western Australia (Cockburn Sound, Albany), South Australia (Great Australian Bight, Gulf St Vincent), Victoria Western Port). New record: South Australia (Kangaroo I., SAM E3215).

Description. The colony is a flat sheet, orange pink in life. In preservative it is brownish pink in the surface and white in the remainder of the colony. Orange pigment cells are in the surface test. Spicules are crowded throughout the colony, which is hard and brittle. They are up to 0.3 mm diameter, and are burr-like with 15–17 club-shaped rays in optical transverse section. Zooids are yellowish brown, their structure often obscured by brown cells in the haemocoel (especially in the interstigmatal bars and transverse vessels) and in the test. Common cloacal apertures about 0.5–1.0 cm apart are on short chimney-like protrusions filled with spicules. These are closed with their rims gathered in the newly recorded specimen. Branchial apertures are not depressed into the surface. The common cloacal cavity in the newly recorded colony is shallow and thoraces cross it in test connectives. The abdomina, embedded in the relatively thick layer of basal test, are bent up at right angles to the thorax.

Remarks. The species is distinguished from L. durabile by its smaller and more crowded spicules, by the branchial apertures not being depressed into the surface of the colony and by the pigmentation of the colonies. Kott (2001) believed that the common cloacal cavity of the present species was more extensive than that of L. durabile , but this was not confirmed in the newly recorded specimen. As in L. durabile and L. levitum , the depth of the common cloacal cavity and the extent to which the abdomina are embedded in the basal test probably are variable. The newly recorded colony also differs from previously described specimens in not having such needle-like spicule rays. Until further material becomes available to test the stability of these characters, the present specimen is assigned to L. ostrearium , which has many similar features.

Lissoclinum reginum Kott, 2001

( figure 21F )

Lissoclinum reginum Kott, 2001: 319 and synonymy; 2004.

Distribution. Previously recorded (see Kott, 2001): Queensland (Capricorn Group, Swain Reefs, Lizard I.), Indian Ocean (Cocos Keeling Is). New record: Northern Territory (Plater Rock, QM G308617).

Description. The colony is a thin, brittle, fragile sheet, crowded with spicules and brownish white in preservative with spherical brown cells scattered throughout. Spicules are burr-like, to 0.04 mm diameter, with numerous narrow rod-like rays with irregular tips. Zooids cross a vast horizontal common cloacal cavity in separate test sheaths. They have brown spherical cells in the haemocoel. Numerous terminal ampullae of vascular stolons project from the zooids into the basal test.

Remarks. The colonies are as previously described, being characteristically thin and fragile and with the usual burr-like spicules and the brown spheres in the haemocoel.

Lissoclinum roseum Kott, 2001

( figure 21G )

Lissoclinum roseum Kott, 2001: 322 .

Distribution. Previously recorded (see Kott, 2001): Hervey Bay, Capricorn Group, Swain Reefs (Queensland). New record: Western Australia (Exmouth Gulf, WAM 882.89).

Description. The newly recorded colonies are small, soft, pinkish cushions on worm tubes. The spicules, burr-like, to 0.028 mm diameter, encapsulate the zooids.

Remarks. Although this is the first record of this species from Western Australia, its characters conform with all those reported from the eastern Australian tropical material (see Kott, 2001).

Figures

FIG. 13. (A) Lissoclinum laneum (SAM E2923), zooid with spherical and morula cells in the surrounding test. (B, C) Lissoclinum stellatum (SAM E2926). (B) Colony surface showing scattered spherical vesicles; (C) thorax. Scale bars: 0.1 mm (A, C); 2 mm (B).

FIG. 21. (A) Lissoclinum conchylium (QM G308632); (B) Lissoclinum diversum (WAM 140.93); (C) Lissoclinum durabile (SAM E3218); (D) Lissoclinum levitum (SAM E3219); (E) Lissoclinum ostrearium (SAM E3215); (F) Lissoclinum reginum (QM G308617); (G) Lissoclinum roseum (WAM 882.89); (H) Lissoclinum stellatum (SAM E2926).