Pyura pilosa Monniot C. & Monniot F., 1974

Maggioni, Tamara, Taverna, Anabela, Reyna, Paola B., Alurralde, Gastón, Rimondino, Clara & Tatián, Marcos, 2018, Deep-sea ascidians (Chordata, Tunicata) from the SW Atlantic: species richness with descriptions of two new species, Zootaxa 4526 (1), pp. 1-28 : 20-21

Pyura pilosa Monniot C. & Monniot F., 1974

References: Pyura pilosa Monniot C. & Monniot F. 1974: 97 ; 1983: 97 (synonymy); Sanamyan & Sanamyan 1999: 1861, fig. 19.

Material examined: Two individuals; trawl; -38.0083 lat. -54.4178 long. (station 11); 1200 m; 12 August 2012.

The specimens are rounded and flattened dorso-ventrally. They measure two and 2.5 cm in diameter. Both were strongly attached to the substratum, adhered by the left side of the body. The tunic is delicate, transparent and thin, but it is completely covered by a thick layer of grains of sand and a few foraminifera. The mantle is yellowish and remarkably thick. The atrial and oral apertures are inconspicuous; both placed at the level of the border of the tunic. Both apertures are four-lobed. There are from 13 to 21 oral tentacles distributed on a single ring. They are filiform but stout and have small branches of the first order. There is a wide velum with undulated margins that extends from the base of the oral tentacles to the base of the oral aperture. The dorsal tubercle is small. It was Vshaped in one specimen and oval-shaped in the other. The pre-pharyngeal band could only be distinguished in the smaller specimen. It forms a deep dorsal V surrounding the dorsal tubercle. The dorsal lamina is divided into approximately 28 equally short pointed languets. Thick musculature covers the totality of the body. Closely packed circular bands surround both apertures and extend almost to the base of the animal. The longitudinal fibers are more separately distributed. They radiate from the apertures and reach the mid-ventral line of the body. The branchial sac has six folds on each side. There are around six to eight rectangular stigmata per mesh. The branchial formula on the right side corresponding to the smallest specimen is:

E-4- 7 -1- 9 -2- 11 -2- 14 -2- 11 -2- 10 -0-DL

The smooth-walled stomach is small and elongated transversely. It is completely covered by several branched hepatic lobes. The primary loop of the gut is widely open. The border of the anus is smooth. There is one gonad on each side. They consist of approximately 11 sac-like testicular follicles aligned on both sides of a central tubular ovary. The oocytes are big and spherical; almost the same size as each individual testicular sac. No endocarps are present.

Remarks. This is the deepest record of the species, increasing its bathymetric range in 600 m. This is also the northernmost record of the species in the SW Atlantic Ocean, increasing its known range of distribution which also includes the South Western Pacific and Southern Indian Oceans.