Condominium floreum, Kott, 2008

Kott, Patricia, 2008, Ascidiacea (Tunicata) from deep waters of the continental shelf of Western Australia, Journal of Natural History 42 (15 - 16), pp. 1103-1217 : 1125-1128

Condominium floreum sp. nov.

( Figures 3E–H )

Distribution

Type locality: Western Australia CSIRO SS10 / 05 (Albany, Stn 22, 118.2940E 35.3350S, 100 m, 22 November 2005, holotype WAM Z27514 QM G328116 ) .

Description

The colony is upright, and divided into laterally flattened undulating fans with an additional secondary lobe. Each lobe expands into a flat platform at the top. Uniform, rounded, small papillae are crowded cauliflower-like over the platformlike surface. Basally the colony narrows into a short, irregular attachment. Each of the surface papillae contains the anterior end of a zooid with its two independent openings each on a short siphon opening separately to the exterior. The branchial aperture is terminal but is turned ventrally to open at one side of the rounded top of a sand-covered surface papillum. The opening of the anterodorsal atrial siphon projects straight up to open on the opposite side of the surface papillum. The rim of each of the apertures is divided into six wide shallow lobes with a narrow pointed papillum in the narrow interval between these lobes. In the preserved specimens narrow longitudinal lines of pigment extend along the length of each siphon from the middle of each scallop on the rim of each opening to the base of the siphon. The internal structure of the thoraces is obscured by contraction in the holotype.

On the thorax a coat of transverse muscles is beneath the longitudinal muscle bands which continue over the abdomen and the long posterior abdomen. There appear to be about 20 rows of at least 30 long, narrow stigmata separated from one another by a wide transverse vessel that extends into a pointed tongue as it crosses the dorsal mid-line. A conspicuous circular neural ganglion and funnel-shaped neural duct has a large circular opening into the pharynx at the anterior end of the dorsal lamina. The long, robust muscular zooids have relatively long thoraces, a narrow gut loop of about the same length with a stomach halfway down, and an especially long posterior abdomina. The large, globular stomach is smooth externally, but sometimes is irregularly creased internally, presumably as a result of the collapse of the stomach wall. A short, wide, post-pyloric duodenal region, a relatively small posterior stomach and a long, wide rectum are separated from one another by short lengths of narrow mid-intestine. Small testis follicles appear to be in a single row in the posterior two-thirds of the long, thread-like posterior abdomen.

Remarks

The small, pointed lobes that alternate with the six shallow scallops of the rim of the apertures resemble those in the rim of apertures of Phallusia spp. associated with yellow pigment spots once erroneously referred to as ocelli (see Kott 1985). However, each of the six streaks of yellow pigment along the siphons in the present species is associated with the centre of the wide, shallow scallops rather than the small pointed projections that alternate with them. The body muscles are unusual in that the coat of circular muscles on the thorax resembles the coat of relatively crowded thoracic muscles that, in Eudistoma spp. , lies beneath the longitudinal bands. With the congeneric Condominium areolatum (the type species of the genus), it differs from other Protopolyclinidae in the apparent absence of any trace of longitudinal branchial vessels. Its long, threadlike posterior abdomina and the form of its colony readily distinguish it from C. areolatum .

Like Ritterellidae and Pseudodiazona longigona , the posterior abdomen of the present species ( C. floreum ) is long and narrow, while C. areolatum and most Monniotus spp. have bunched testis follicles in a short posterior abdomen. The length of the posterior abdomen and the arrangement of the testis follicles may be artefacts caused by the post-mortem events affecting the zooid.

Family PSEUDODISTOMIDAE Harant, 1931

The family is characterized by its separately opening six-lobed apertures, three rows of stigmata, smooth stomach, relatively short gut loop, a distinct rectal valve and incubation of one to three large larvae in a brood pouch at the postero-dorsal end of the thorax. The larvae have similar large antero-median adhesive organs consisting of clumps of adhesive cells recessed into everting cups of larval epithelium (see Kott 1990a, 1992a, 2007). Formerly ( Kott 1992a), the family was thought to contain the relatively speciose genus Pseudodistoma and the monotypic genera Citorclinum Monniot and Millar, 1988 and Anadistoma Kott, 1992a , all with gonads in a posterior abdomen. More recently, Kott (2007) has discussed the relationships of the genus Sigillina to Pseudodistoma . The former genus is distinguished primarily in the presence of the gonads in the gut loop in the abdomen (rather than being in a posterior abdomen where they are located in the latter genus), the narrow posterior abdominal stolon from the concavity of the gut loop (rather than a posterior abdomen) and an almost spherical (rather than four-chambered) stomach. Both zooids and larvae of these genera otherwise are similar; a close phylogenetic relationship is implied and in this work Sigillina is proposed as a member of the family Pseudodistomidae .

The genus Pseudodistoma is known from a number of species primarily in the southern hemisphere, but also from north of the equator into Japanese waters, tropical western Africa ( Senegal) and the Mediterranean ( Corsica). Species are known from South Africa (Cape Province) and the West Indian Ocean ( Madagascar), the tropical waters of the western Pacific, Australian tropical and temperate waters and New Zealand. Sigillina also is known from a range of locations in the Indo-West Pacific. Neither genus has been recorded from the eastern Pacific or the western Atlantic (see Kott 1992a). Generally, their zooids are conservative, showing little inter-specific variation. Larvae also are very similar to one another, being invariably large, with large antero-median adhesive organs and a relatively large mass of yolk. It is not likely that these large larvae are free swimming for long periods and the large mass of yolk is most probably associated with a long incubatory period during which the oozooid develops to an advanced stage. The unusually large adhesive organs with conspicuous cones of adhesive cells may also be associated with the attachment of a large oozooid (see Kott 1992a). Of known larvae only P. aureum has a larval trunk that is less than 1.0 mm long and Kott (1992, p. 424) thought larval adhesive organs were different from other species, indicating a polyphyletic origin for the genus. However, the adhesive organs with their tufts of adhesive cells arising from the base of cup-shaped depressions in the anterior end of the larval trunk (see Kott 1992a, P. aureum Figure 16c and P . australe Figure 17f ) in due course develop stalks, evert into balloon-like structures and subsequently form flattened plates with a patch of adhesive cells in the centre of the everted adhesive organ (see P. australe: Kott 1992a , Figure 17g : P. candens Kott, 1992a , Figure 18c ). Larvae found in the newly recorded material of both genera, although not in good condition, show a range of developmental stages and confirm the lack of diversity in both zooids and larvae of these genera. Possibly the lack of conspicuous distinguishing characters resulting in misidentification could be the explanation of the wide geographic range of many of the species.

Anadistoma Kott, 1992a , thought to be a related genus in the family Pseudodistomidae , is known from the type specimen of its type species A. attenuatum . The morphology of the zooids (including the relative lengths of parts of the body) resembles contracted zooids of Pseudodistoma spp. However, on reexamination, these unusually large and very much contracted zooids are found to have an almost continuous coat of transverse muscles beneath the longitudinal muscles of the thorax. With their smooth stomach, these transverse muscles clearly distinguish them from Pseudodistoma spp. The long oesophageal neck, three rows of stigmata, separately opening six-lobed apertures and the coat of transverse muscles on the thorax may indicate a phylogenetic connection with the genus Eudistoma in the Polycitoridae .

Figures

Figure 3. Condominium areolatum (QM G328441): A, thorax; B, abdomen; C, posterior abdomen; D, anterior end of larval trunk. Condominium floreum sp. nov (QM G328116): E, colony; F, thorax and abdomen; G, posterior abdomen showing ovary and testis; H, details of the anterior part of the thorax showing branchial tentacles, dorsal tubercle neural gland and ganglion and the anterior part of the branchial sac. Scales: A–C, F–G; 1.0 mm; D, H, 0.5 mm; E, 1.0 cm.

Figure 16. Scanning electron micrographs of didemnid spicules: A, Atriolum tubiporum, QM G328004; B, Leptoclinides durus, QM G328158; C, Leptoclinides fungiformis, QM G328444; D, Leptoclinides vesica, QM G328458; E, F, Polysyncraton calculum, QM G328140; G, Polysyncraton dealbatum, QM G328119; H, Polysyncraton fistulum, QM G328446.

Figure 17. Scanning electron micrographs of didemnid spicules: A, Polysyncraton millepore, QM G328050; B, Polysyncraton?palliolum, QM G328161; C, Polysyncraton pavimentum, QM G328058; D, Didemnum?candidum, QM G328457; E, Didemnum cygnuus, QM 328456; F, Didemnum dolium, QM G328008; G, Didemnum jedanense, QM G328005; H, Didemnum moseleyi, QM G328455.

Figure 18. Scanning electron micrographs of didemnid spicules: A, Didemnum multiampullae, QM G328057: B, Didemnum ossium, QM G328055; C, Didemnum perplexum, QM G328034; D, Didemnum plebeium, QM G328451; E, Didemnum tapetum, QM G328016; F, Didemnum velum, QM G328120; G, Didemnum sp 1, QM G328160; H, Didemnum sp. 2, QM G328166.