Didemnum congregatum, 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 : 2489-2500

Didemnum congregatum sp. nov.

( figure 18F )

Distribution. Type locality: Papua New Guinea (Madang, Stn 9 outer side of barrier reef off N end Milibag I., coll. S. Slacksmith, 17 August 1982, syntypes WAM192.90).

Description. The syntypes are small, fragile, paper-thin, colonies attached to weed fronds. A small spicule-filled papilla is associated with each branchial aperture, but these appear to be rubbed off in older specimens. Spicules are crowded throughout. The surface test is thin and thoraces of the small zooids cross the horizontal atrial cavity with their own independent ventral strip of test, which has a large vertical oval clump of spicules from the lateral organ along each edge. Abdomina are embedded in the basal test, although the zooids are disintegrated in these very thin colonies and details of their structure were not determined. The spicules are stellate, generally to 0.06 mm with 11–13 strong conical rays in optical transverse section. Scattered amongst these spicules are giant (to 0.1 mm between ray tips) spicules with up to six long, narrow spiky rays.

Remarks. Although the details of the zooids are not available and the general colony form does not differ in any way from many other small, thin, didemnids, the spicules of these colonies differ in the relatively numerous rays of the majority of the spicules. Didemnum membranaceum has both large and small spicules that most closely resemble those of the present species, but the smaller spicules have fewer rays. These small colonies, from Madang, with pointed papillae associated with each branchial aperture, resemble some specimens of D. nekozita Tokioka, 1967 . However, the spicules of the latter species have fewer and rodlike rays rather than the conical ones of the present species.

Didemnum coralliforme Kott, 2004

( figure 18G )

Didemnum coralliforme Kott, 2004 .

Distribution. Previously recorded (see Kott, 2004): Western Australia (W of Port Hedland). New records: Northern Territory (Angler Reef, QM G308610; Meigs Reef, QM G308629).

Description. In life, one (QM G308610) of the newly recorded colonies is pinkish red while the other is orange-red. Both are fleshy slabs with rounded swellings and some short lobes with white-rimmed terminal common cloacal apertures. In preservative both colonies are creamish orange to white flexible sheets and the preservative is a pinkish orange colour. In both colonies orange vesicles interrupt the spicules in the superficial layer of test. In the orange-red colony these vesicles are arranged in a circle around each branchial aperture, and in the other the vesicles are separated from one another by a thin network of spicules. Spicules also line the margins of the evenly spaced branchial apertures but they are only moderately crowded throughout the remainder of the colony, except for a more crowded layer on the base. Spicules are relatively small (to 0.05 mm diameter) with five to seven and occasionally nine long, almost rod-like rays in optical transverse section. The common cloacal cavity is thoracic, the thoraces crossing it in independent test sheaths. Abdomina are embedded in the basal test.

Zooids have large, orange thoraces with huge atrial apertures. An atrial lip is not present. Eight stigmata are in the anterior row. A long oesophageal neck has a fine retractor muscle projecting from about halfway down it. The gut loop is long and flexed ventrally. Seven coils of the vas deferens surround the undivided testis in one (QM G308610) colony but gonads were not detected in the other. Long-stemmed thoracic buds are attached to the oesophageal neck of the former specimen.

Remarks. The relatively small spicules with their few and long, straight rays are the principal diagnostic character of this species. Didemnum madeleinae Monniot and Monniot, 2001 has similar spicules but they have shorter and more conical rays. Also, the presence of vesicles in the surface test appears to be characteristic of the present species, although the number of these vesicles and their arrangement are variable, being arranged in a circle around the branchial apertures in the type material and one of the newly recorded colonies, but forming more of a mosaic in the surface in the other newly recorded colony. These vesicles resemble those described in Didemnum sordidum Kott, 2001 and in some Polysyncraton spp. (see Kott, 2001). The newly recorded colonies do not have the cylindrical thin colony branches and three-dimensional form of the type material of the present species although it occurs in other species in the present collection, namely D. grande (Herdman, 1886) and D. granulatum Tokioka, 1954 . The colony form does not appear to be a characteristic of the species, possibly being affected by the habitat.

Didemnum crescente Kott, 2001

( figures 7A, B , 18H )

Didemnum crescente Kott, 2001: 166 .

Trididemnum spiculatum: Kott, 1972: 178 .

Distribution. Previously recorded (see Kott, 2001): Tasmania (Triabunna), Victoria (Mallacoota Inlet, Western Port), New South Wales (Eden). New record: South Australia (Waterloo Bay in caves, SAM E3208).

Description. Colonies are thin, flat, hard sheets encrusting fronds of kelp. In preservative they are white with crowded spicules. The common cloacal cavity is shallow and at thorax level. The spicules are stellate, moderately large to 0.062 mm diameter with seven to nine and sometimes 11 conical pointed rays in optical transverse section. The ray length/spicule diameter ratio is 0.375. Zooids are small, with a short branchial siphon, contracted thorax with six stigmata in the anterior row reducing to three in the last row and lateral organs projecting from each side of the endostyle at the posterior end of the thorax. The oesophageal neck is relatively short and the abdomen is bent up at right angles to the thorax. Four conspicuous stolonic vessels project forwards from the ventral concavity of the gut loop. Nine coils of the vas deferens surround the undivided testis.

Remarks. Although Kott (2001) reported large posterior abdominal cavities in this species, they were not detected in the re-examined material from the Great Australian Bight, which have been assigned on the basis of the spicules and their distribution, the number of coils of the vas deferens, the small number of stigmata, and the conspicuous projecting thoracic lateral organs. The short fourth row of stigmata in the small contracted thoraces in specimens from Waterloo Bay (SAM E3208) was overlooked by Kott (1972).

The present species is distinguished from the sympatric D. incanum by its larger spicules with seven to nine and occasionally 11 rays in optical transverse section (seven to nine and occasionally five in D. incanum ).

Didemnum delectum Kott, 2001

( figure 19A )

Didemnum delectum Kott, 2001: 171 and synonymy.

Distribution. Previously recorded (see Kott, 2001): South Australia (Great Australian Bight, Yorke Peninsular, Spencer Gulf, Gulf St Vincent, Investigator Strait). New record: South Australia (Kangaroo I., SAM E3226).

Description. The colony is thin, and brittle, slightly pinkish white in preservative with creamish yellow zooids. Common cloacal canals are oesophageal and the apertures are about 1.0 cm apart on slight elevations of the otherwise smooth surface of the colony. Zooid openings are not present immediately around the common cloacal apertures. Branchial openings appear as white points from the surface owing to the small plug of spicules in the siphon lining. Spicules are crowded throughout the test. They are small, 0.035 mm diameter with seven to nine long, rod-like or conical rays in optical transverse section. The ray-length/spicule diameter ratio in spicules with rod-like rays is about 0.4.

Zooids have small orange thoraces, short and cylindrical branchial siphons, wide atrial apertures and a retractor muscle from halfway down the oesophageal neck. Abdomina are white and gonads were not detected in the newly recorded specimen.

Remarks. Species with rod-like spicules include Didemnum candidum Savigny, 1816 (which has spicules with shorter and fewer rays), D. fuscum Sluiter, 1909 (which has larger spicules and dark cells in the test and around the zooids) and D. mantile Kott, 2001 (which has larger spicules with fewer rays and a leathery rather than brittle colony).

Although the more conspicuous lobes with terminal common cloacal apertures are nor present in the newly recorded specimen, the spicules and their distribution and the colour of the colonies are as previously described.

Didemnum grande (Herdman, 1886)

Leptoclinum albidum var. grande Herdman, 1886: 291 .

Didemnum grande: Kott, 2001: 185 and synonymy; 2004.

Distribution. Previously recorded (see Kott, 2001, 2004): Western Australia (Port Hedland); Queensland (Hervey Bay, Capricorn Group, Swain Reefs, Whitsunday Is), Indonesia, Philippines. New records: Northern Territory (Angler Reef, QM G308606-7).

Description. Both colonies are thin cylindrical anastomosing stalks little more than 1.0 cm in diameter forming an open three-dimensional reticulum. Sometimes a flat web-footed-like expanse of the colony forms in the fork of the branches. One (QM G308606) specimen is bright red in life and the other is marbled orange-white. Both colonies are white in preservative, although the preservative is orange-red or brown-orange. Spicules are present throughout the colony and they form an especially hard core (like an axial skeleton) in the centre of the cylinder. The spicules are stellate with 9–11 strong conical rays in optical transverse section. Some are up to 0.09 mm diameter, although more often the maximum diameter is 0.06 mm. The common cloacal cavity is thoracic. The abdomina are embedded in the test that surrounds the central axial core of crowded spicules.

Zooids have large, orange thoraces with large sessile atrial apertures and a conspicuous retractor muscle projecting from the top of the oesophageal neck. The vas deferens coils seven times around the undivided, dome-shaped testis follicle.

Remarks. In the present collection, colonies of D. granulatum and Polysyncraton peristroma sp. nov. have a similar form to these newly recorded colonies of the present species. Also, similar colonies have been reported for D. coralliforme Kott, 2004 , D. clavum Kott, 2001 and D. ossium Kott, 2001 . Although it is a colony form not previously reported for the present species, other characters such as the form and distribution of the spicules, large thoraces, number of vas deferens coils and the intense colour of the preservative are characteristic.

Didemnum granulatum Tokioka, 1954

( figure 19B )

Didemnum (Didemnum) moseleyi f. granulatum Tokioka, 1954: 244 .

Didemnum granulatum: Kott, 2001: 188 ; 2002c: 35.

Distribution. Previously recorded (see Kott, 2001, 2002c): Western Australia (Cervantes, Montebello Is); Queensland (Whitsunday Is, Hardy Reef, Bowden Reef) Northern Territory (Darwin, Bathurst I.), Palau Is, French Polynesia, Tokara Is, Fiji; French Polynesia, Hawaii. New records: Northern Territory (Bottlewasher artificial reef, QM G308601; Angler Reef, QM G308602).

Description. Each of the newly recorded specimens has flat expanses of colony with narrow cylindrical outgrowths that tend to form an open reticulum. They are white in life as well as in preservative. Spicules are crowded throughout and are especially crowded in the centre of the branching stalks and projecting lobes where they form a hard central axial rod of packed spicules. The spicules are never more than 0.05 mm and have seven to nine long conical to almost rod-like rays, slightly rounded rather than sharply pointed at the tip. The common cloacal cavity is thoracic, sometimes projecting behind the zooids. Six coils of the vas deferens surround the undivided testis.

Remarks. This species lacks very distinctive characters and its wide range could be the result of misidentification. The small spicules resemble those of D. madeleinae Monniot and Monniot, 2001 , although the conical spicule rays of the latter species are more pointed than the present one. However, the spicule rays of the present species are more conical than the long rod-like ones of Didemnum coralliforme Kott, 2004 . The relatively few vas deferens coils also help to distinguish the species.

Didemnum incanum (Herdman, 1899)

( figures 8A, B , 19C )

Leptoclinum incanum Herdman, 1899: 90 .

Didemnum incanum: Kott, 2001: 191 and synonymy; in press.

? Leptoclinum tuberatum Nott, 1892: 314 .

Didemnum moseleyi: Kott, 1972: 179 .

Distribution. Previously recorded (see Kott, 1972, 2001): South Australia

(Waterloo Bay, SAM E3209; Gulf St Vincent; Cape Jervis); Victoria (Gabo I.,

Lorne); New South Wales (Illawarra, Port Jackson). New records: Tasmania (Triabunna, SAM E2925), New Zealand (Wellington Harbour, QM G308590; Nelson, QM G308591; Picton Ferry Wharf, QM G308938; Pelorus Sound, QM G308592).

Description. The species has small stellate spicules to 0.03 mm diameter with five to nine conical rays in optical transverse section, sometimes crowded throughout, but sometimes less crowded or even sparse in the lower part of the colony. The thoraces of the small evenly spaced zooids, with not more than six stigmata in the anterior row (reducing to three in the last row), cross the shallow horizontal common cloacal cavity with a ventral strip of test. Occasionally a slightly deeper primary common cloacal canal separates groups of zooids from one another. Nine coils of the vas deferens surround the testis. The small larval trunk (to 0.5 mm long) has the tail wound about three-quarters of the way around it, and four lateral ampullae are along each side of the three anteromedian adhesive organs.

Remarks. Although Kott (2001: 191) regarded the colonies as ‘invariably’ thin, encrusting sheets, she assigned some with lobed surfaces to the species. The same variations in colony form occur in the newly recorded specimens, those from similar New Zealand habitats and one from Edithburgh Jetty (Kott, 2001: pl. 10D: QM G302766) having the same lobed surfaces.

The moderate-sized spicules with five to nine conical rays and the simple colony form resemble the tropical species D. perplexum Kott, 2001 and D. granulatum Tokioka, 1954 , however, the nine coils of the vas deferens distinguish the present species.

Aspects of the Guadeloupe Didemnum perlucidum Monniot, 1983 are similar to the present species (small stellate spicules with relatively few rays, and nine coils of the vas deferens). However, the spicule rays appear to be shorter and the spicules are sparser than those of the present species (sometimes being absent altogether) and the zooids of the Atlantic species are arranged along each side of conspicuous, deep, circular primary common cloacal canals, rather than being evenly spaced.

Monniot et al. (1985, 1991) and Monniot and Monniot (1987) believe that D. perlucidum has been transported to the western Pacific on the hulls of ships. The specimen shown in Monniot et al. (1991: 176) has smaller and more crowded systems than D. perlucidum and appears to be a different species altogether. Specimens referred to D. perlucidum from French Polynesia ( Monniot et al., 1985; Monniot and Monniot, 1987) apparently have evenly spaced zooids like D. incanum (see Monniot et al., 1985: pl. 1), but specimens from the same location (possibly the same specimens) are said ( Monniot and Monniot, 1987) to have conspicuous cloacal canals and an ‘average’ of seven stigmata per row (which is more than is known for the present species). Although their identity is not resolved, these specimens do not seem to be either D. perlucidum or D. incanum .

Although there are few trans-Tasman species, there are some that may be part of a Gondwana fauna, and the present species may be part of that fauna (see Kott, in press).

Didemnum jucundum Kott, 2001

( figures 8C , 19D )

Didemnum jucundum Kott, 2001: 197 and synonymy.

Distribution. Previously recorded (see Kott, 2001): Western Australia (Esperance), South Australia (?West I., Kangaroo I.). New record: Tasmania (Forestier Peninsula, SAM E3201). Description. In life the newly recorded colony is translucent beige with clouds of black and yellow pigment in the surface, white dots where the branchial apertures open, and a ring of black pigment around each common cloacal aperture. In preservative the colony is white. Spicules are crowded throughout, but do not line the margins of the branchial apertures. They are large, to 0.82 mm diameter, with 13–15 relatively long rays in optical transverse section. The rays are obelisk-shaped with conical tips. The colony is relatively thick and fleshy owing to the thick layer of basal test in which abdomina are embedded. The zooids are along each side of shallow circular common cloacal canals which surround solid stands of test in which the ventral surface of each zooid is embedded. The surface layer of test over the common cloacal canals is thin and breaks up readily.

The most conspicuous aspect of the zooids of this species is the particularly long oesophageal neck, which, though usually contracted anterior to the point where the retractor muscle separates from it (at least two-thirds of its total length), is about three times the length of the contracted thorax. The gut forms a double loop and 12 coils of the vas deferens surround a spherical testis. The larval trunk is 0.9 mm long, the tail is wound two-thirds of the way around it, and four ampullae are along each side of the three antero-median adhesive organs.

Remarks. The specimen accords with previously recorded material, especially in regard to its appearance in life. It appears to have a wide range across the southern coast of Australia.

Didemnum lissoclinum Kott, 2001

( figure 19E )

Didemnum lissoclinum Kott, 2001: 202 and synonymy.

Distribution. Previously recorded (see Kott, 2001): South Australia (Great Australian Bight, Yorke Peninsula, Kangaroo I., Gulf St Vincent), Victoria (Mallacoota Inlet, Deal I.), New South Wales (Jervis Bay, Port Hacking). New record: South Australia (Kangaroo I., SAM E2922).

Description. Living colonies are white, with irregular, knobbly surface lobes, each with a terminal common cloacal aperture. Cloacal apertures are numerous and conspicuous, always on elevations of the surface. They have spicule-free test in the rim of the aperture. Beneath a very thin spicule-free superficial layer of test, spicules are moderately crowded throughout the colony. Branchial apertures are sometimes (but not always) lined with spicules. Spicules are small, to 0.07 mm diameter, with seven to nine and sometimes 11 conical rays in optical transverse section. These colonies are complex, the primary common cloacal canals surrounding clumps of zooids are deep and often posterior abdominal, and the surface lobes often overgrow and fuse with other parts of the colony surface.

Zooids are small with not more than six stigmata per row, a large open atrial aperture, a long, fine retractor muscle from the top of the long oesophageal neck and buds at its base, about three to five stolonial vessels with conspicuous terminal ampullae, and a club-shaped abdomen. Gonads were not detected.

Remarks. The species has been recorded from Kangaroo I. previously and it appears to be a common component of the southern ascidian fauna. The zooids and larvae are similar to those of Didemnum incanum . The spicules also are similar, but are larger and have more rays, the deep three-dimensional cloacal system does not occur in D. incanum and the very long oesophageal neck appears to be a unique character of the present species.

Didemnum madeleinae Monniot and Monniot, 2001

( figure 19F )

Didemnum madeleinae Monniot and Monniot, 2001: 268 ; Kott, 2002c: 35.

Distribution. Previously recorded (see Kott, 2002c): Northern Territory (Darwin), Papua New Guinea. New record: Northern Territory (Channel I., QM G308630).

Description. The colony is an irregular encrusting sheet, red in life. In preservative, it is yellowish and blotchy on the surface and the preservative is stained yellow. The colony is thin, brittle and packed hard with spicules. Spicules are stellate, to 0.05 mm diameter with seven to nine sharply pointed conical rays in optical transverse section. The common cloacal cavity is shallow and thoracic and the abdomina are embedded in the basal test. Zooids are small, with a rounded atrial lip; a circular, concave lateral organ; a thick retractor muscle from halfway down the oesophageal neck; eight coils of the vas deferens and large yellow eggs. The specimen, collected in September, has larvae in the basal test with the tail wound three-quarters of the way around the 0.6 mm-long, cigar-shaped trunk. Four lateral ampullae are along each side of the three antero-median adhesive organs.

Remarks. The regular, relatively small stellate spicules with sharply pointed conical rays and the large number of vas deferens coils help to distinguish this species.

Didemnum membranaceum Sluiter, 1909

( figure 19G )

Didemnum membranaceum Sluiter, 1909: 58 ; Kott, 2001: 205 and synonymy; 2002c: 36.

Distribution. Previously recorded (see Kott, 2001, 2002c): Western Australia (Montebello Is to Dongara); Queensland (Moreton Bay, Heron I., Swain Reefs, Broadhurst Reef, Fantome I., Davies Reef); Northern Territory (Darwin); Timor Sea, Indonesia, Micronesia, French Polynesia, Hong Kong. New records: Western Australia (Passage Is, WAM 531.92; Marmion Lagoon, WAM 54.89); South Australia (Kangaroo I., SAM E3227).

Description. One (WAM 531.92) of the Western Australian colonies is an extensive sheet enveloping a branch of a coral skeleton, but the other newly recorded colonies are small and flat. All the colonies have large horizontal common cloacal cavities and spicules crowded throughout. The South Australian colonies have minute spicule-filled papillae crowded on the surface between the branchial apertures and the large colony from Western Australia enveloping the coral has six spicule-filled papillae encircling each branchial aperture. In all the specimens, the spicules are characteristic, giant spicules with up to six long, attenuated, spiky rays being scattered amongst smaller stellate ones with seven to nine conical pointed rays in optical transverse section. The maximum diameter in the South Australian specimens is only 0.056 mm diameter for giant spicules and 0.035 mm diameter for the smaller ones. Other aspects of the zooids are as previously described (see Kott, 2001).

Remarks. The newly recorded specimens have characteristic large horizontal thoracic cloacal cavities and small zooids with comma-shaped thoraces, and they appear to be conspecific, despite the fact that the record from South Australia is the first from temperate waters for this species.

Didemnum pecten Kott, 2001

( figure 19H )

Didemnum pecten Kott, 2001: 220 .

Didemnum pellucidum Kott, 2001: 222 (part, specimens SAM 2606, E2651, E2654-5, E2658).

Distribution. Previously recorded (see Kott, 2001): South Australia (Kangaroo I., Point Souttar, Gulf St Vincent), Victoria (Lorne), New South Wales (Jervis Bay). New records: South Australia (Stansbury Jetty, SAM E2856; Kangaroo I., SAM E2858).

Description. One colony (SAM E2856) is an upright lobe with a terminal common cloacal aperture. The other specimen (SAM E2585) has slightly translucent vertical lobes each with a terminal common cloacal aperture. Both specimens have large posterior abdominal common cloacal cavities separating the central test core from the outer zooid-bearing layer. Spicules are evenly distributed but not crowded in the surface at branchial siphonal level and a clump is in the siphon lining. They are absent from or sparse in the internal test core. Spicules are stellate, with 7–11 conical rays in optical transverse section and up to 0.08 mm diameter (although smaller ones predominate).

Remarks. The sympatric species D. pellucidum has vertical colony lobes with terminal common cloacal apertures projecting from the upper surface, spicules in the surface layer of test but absent from the inner core, stellate spicules with 7–11 rays in optical transverse section, a three-dimensional common cloacal cavity and conspicuous projecting columnar epidermal cells, as in the present species. Both colony and zooids are so alike it would be difficult to separate the species, were it not for the smaller larvae with fewer lateral ampullae and 10 coils of the vas deferens around the beehive or dome-shaped testis in D. pecten , while D. pellucidum has larger spicules, longer branchial siphons, more (12) larval lateral ampullae, a larger larval trunk and more (11) coils of the vas deferens around a flatter lens-shaped testis.

The newly recorded specimens have neither mature testis nor larvae and have been identified by their spicules, which do not exceed 0.08 mm diameter, and by the relatively short branchial siphons. Conspicuous pointed projecting columnar epithelial cells cover the thorax and branchial siphons.

Spicules are shown in Kott, 2001: figure 170–1 (not figure 170A).

Didemnum poecilomorpha Monniot and Monniot, 1996

( figure 20A )

Didemnum poecilomorpha Monniot and Monniot, 1996: 226 ; Kott, 2001: 226 and synonymy.

Distribution. Previously recorded (see Kott, 2001): Western Australia (Broome), Papua New Guinea, Palau Is, Indonesia. New record: Western Australia (Dongara, WAM142.93).

Description. The newly recorded colony is a white, smooth sheet enveloping a kelp stalk. Large, sessile common cloacal apertures are randomly spaced on the surface, amongst the small, evenly spaced (about 7 mm apart) stellate branchial apertures, which are slightly depressed into the surface, the margins of the apertures lined with white spicules. Spicules are packed throughout the test. They are to 0.06 mm diameter, globular to stellate, with 11–13 truncated or conical pointed rays in optical transverse section. The common cloacal cavity is relatively shallow, at thorax level. The surface layer of test is relatively thick, accommodating the long branchial siphons, which are about half the length of the contracted thorax. Otherwise the thoraces are small. The oesophagal neck is longer than the rest of the thorax, and the retractor muscle projects from about three-quarters of the way down it. The vas deferens coils eight times around the undivided testis. Pools of green pigment are in the basal test.

Remarks. The quilted surface appearance of previously described specimens was not evident in the newly recorded colony, although other characters, such as the size and form of the spicules, the zooids (including the number of vas deferens coils) are as reported for the type material. Didemnum diversum Kott , in press has similar spicules and eight coils of the vas deferens, but is distinguished by its pectinate spicule rays. Of the known species with a similar diversity of spicules, D. moseleyi (Herdman, 1886) has a shorter branchial siphon, not more than 11 spicule rays in optical transverse section and nine coils of the vas deferens; D. bisectatum Kott, 2001 , D. chartaceum Sluiter, 1909 , D. multispirale Kott, 2001 and D. nambucciensis Kott , in press have spicules with more rays; D. bicolor Kott, 2001 , D. guttatum Monniot and Monniot, 1996 , D. macrosiphonum Kott, 2001 and D. ossium Kott, 2001 have fewer spicule rays; and Didemnum elongatum Sluiter, 1909 has a similar long branchial siphon, similar but larger spicules with fewer rays, and only six coils of the vas deferens.

Didemnum scopi Kott, 2001

( figure 20B )

Didemnum scopi Kott, 2001: 232 .

Distribution. Previously recorded (see Kott, 2001): Queensland (Caloundra, Hervey Bay, Capricorn Group, Swain Reefs, Barrow Point). New record:? Western Australia (Jurien Bay, WAM 203.93).

Description. The newly recorded specimen is a small scrap of a colony with brown zooids giving it a pinkish colour when seen through the single, one spicule-thick layer of spicules in the surface. Stellate branchial apertures are packed with spicules around them and also there is a layer on the base of the colony. The spicules have the characteristic 9–11 almost rod-shaped rays in optical transverse section. The common cloacal cavity is thoracic and abdomina are embedded in the basal test.

Remarks. Although this species has not previously been recorded from northwestern Australia, its brown zooids and rod-shaped spicule rays are characteristic. The spicules are like those of Didemnum candidum Savigny, 1816 , but the rays are more numerous.

Didemnum sordidum Kott, 2001

( figure 20C )

Didemnum sordidum Kott, 2001: 234 and synonymy.

Distribution. Previously recorded (see Kott, 2001): Western Australia (Lord Mayors Shoal, Pilbara); Queensland (Moreton Bay to Noosa, Heron I.); Hong Kong; Philippines; French Polynesia; Christmas I. (Indian Ocean). New record: Western Australia (Rottnest I., WAM 189.93).

The new record is the most southerly one for this widespread and relatively commonly occurring Indo-West Pacific species.

Remarks. In the newly recorded colony, characteristic brown spherical cells are free in the test and around the zooids and spicules of characteristic size and form crowd the test and outline the branchial apertures as previously reported for this species (see Kott, 2001).

Figures

FIG. 18. (A) Polysyncraton rostrum (QM G398628); (B) Polysyncraton tegetum (SAM E3213); (C) Polysyncraton textus (WAM 556.88); (D) Didemnum albopunctatum (QM G308627); (E) Didemnum candidum (WAM 557.88); (F) Didemnum congregatum (WAM 192.90); (G) Didemnum coralliforme (QM G308629); (H) Didemnum crescente (SAM E3208).

FIG. 7. Didemnum crescente (SAM E3208). (A) Thorax; (B) abdomen. Scale bars: 0.1 mm.

FIG. 19. (A) Didemnum delectum (SAM E3226); (B) Didemnum granulatum (QM G308601); (C) Didemnum incanum (SAM E3209); (D) Didemnum jucundum (SAM E3201); (E) Didemnum lissoclinum (SAM E2922); (F) Didemnum madeleinae (QM G308630); (G) Didemnum membranaceum (WAM 54.89); (H) Didemnum pecten (SAM E2858).

FIG. 8. (A, B) Didemnum incanum [(A) SAM E3209; (B) QM G308592]. (A) Vertical section through colony (semi-diagrammatic); (B) thorax. (C) Didemnum jucundum (SAM E3201), zooid. Scale bars: 1.0 mm (A); 0.1 mm (B, C).

FIG. 20. (A) Didemnum poecilomorpha (WAM 142.93); (B) Didemnum scopi (WAM 203.93); (C) Didemnum sordidum (WAM 189.93); (D) Didemnum spumante (WAM 194.90); (E) Didemnum tabulatum (WAM 143.93); (F) Didemnum ternerratum (SAM E2920); (G) Didemnum vahatuio (WAM 204.93); (H) Lissoclinum coactum (WAM 1136.89).