Polysyncraton cabofriense Oliveira & Rocha, 2019

Oliveira, Livia M., Hoeksema, Bert W. & Rocha, Rosana M., 2019, Polysyncraton (Ascidiacea, Didemnidae): a re-examination of some specimens and descriptions of three new species, European Journal of Taxonomy 519, pp. 1-25 : 10-12

Polysyncraton cabofriense Oliveira & Rocha sp. nov.

urn:lsid:zoobank.org:act:356E2138-BAED-47B4-8E06-8182B064EB7B Fig. 6

Etymology

The name refers to the region where the species was found.

Material examined

Holotype BRAZIL • 1 colony; Rio de Janeiro, Cabo Frio, Pargos Island, Enseada do Pinguim ; 22°51′10″ S, 41°54′22″ W; ~ 10 m depth; 7 May 2014; L.F. Skinner leg.; scuba; DZUP POSC-50, slide DZUP DID5.02 .

Paratypes

BRAZIL • 2 colonies; same collecting data as for holotype; DZUP POSC-46, DZUP POSC-49, slide DZUP DID5.05 • 2 colonies; Comprida Island , Ponta Leste; 22°51′41″ S, 41°56′12″ W; ~ 8 m depth; 6 May 2014; L.F. Skinner leg.; DZUP POSC-47, DZUP POSC-48, slides DZUP DID5.03 , DZUP DID5.04 .

Description

Living colonies are yellowish, with a diameter of 3 to 15 cm and a thickness of 2 to 3 mm. When preserved in formalin, colonies usually lose their colour and become cream coloured, sometimes white. They have an irregular shape, molding themselves to the substrate. The colony surface has several common cloacal apertures, each one with short lobes ( Fig. 6 a–b). The tunic is firm, brittle and smooth. Green algae were observed on the surface of some colonies. Spicules are distributed in the whole tunic, with relatively high concentrations on each side of the thorax at the level of the lateral thoracic organ. There are two kinds of spicules: stellate, 32 to 40 µm in diameter, with 6 or 7 blunt-tipped conical rays in transverse optical section; others are smaller (25 to 28 µm in diameter), with round and short rays ( Fig. 6c ).

Zooids are 0.8 to 1.0 mm long. The oral siphon has six small triangular lobes. The atrial aperture is wide, exposing most of the pharynx. The atrial languet is pointed and thin ( Fig. 6d ) or wide and rounded. In some specimens it was absent, probably lost during dissection. The lateral thoracic organs are circular, not protruding and localised between the first and second rows of stigmata on the border of the atrial aperture. The pharynx has seven stigmata in the first two half rows and six stigmata on the posterior two half rows. The muscular process is lacking. The testis is divided in three oval follicles surrounded by three coils of the sperm duct. The oocyte is single, measuring 0.6 mm.

The larvae are elliptical, gemmiparous, the trunk measuring 0.9 to 1.0 mm. A tail with a diameter of 95 µm winds about ¾ of a turn around the trunk. The three adhesive papillae show a short and wide peduncle. The sucker of the central adhesive papilla is 124 µm in diameter. There are 10 pairs of rounded ectodermal ampullae. The ocellus is 45 µm long and 346 µm distant from the anterior region of the tail.

Remarks

Only two species of Polysyncraton have been reported from Brazil, P. amethysteum with a distribution along the whole coastline and P. maurizelae Paiva et al., 2015 from Rocas Atoll ( Paiva et al. 2015). Polysyncraton cabofriense sp. nov. differs from P. amethysteum by its colour, higher density of spicules, lobed cloaca and larvae with more pairs of ectodermal ampullae. Polysyncraton maurizeliae has orange colonies with smooth common cloacal apertures, zooids longer and with 12 stigmata in the 1 st row, and the lateral thoracic organ in the 3 rd row. Among other species from the Atlantic, P. louminae F. Monniot, 1984 has a colony of similar shape and spicules, but the colony is grey, zooids have longer oral siphons and two testis follicles surrounded by 3 to 5 coils of the sperm duct, and the larvae are not gemmiparous and have more pairs of ectodermal ampullae (F. Monniot 1984).

Distribution

Type locality: Brazil (Rio de Janeiro).

Figures

Fig. 6. Polysyncraton cabofriense Oliveira & Rocha sp. nov. (DZUP POSC-50). a. Colony in situ. b. Colony surface (arrows indicating common cloacal apertures with lobes). c. Spicules. d. Thorax stained (big arrow indicating the lateral thoracic organ and small arrow the atrial languet). e. Abdomen (arrow indicating the sperm duct coil). f. Larva. Scale bars: d–f = 0.1 mm. Photo (a) courtesy of L.S. Skinner.