Polyandrocarpa aurorae, Monniot, 2018

Monniot, Françoise, 2018, Ascidians collected during the Madibenthos expedition in Martinique: 2. Stolidobranchia, Styelidae, Zootaxa 4410 (2), pp. 291-318 : 298-299

Polyandrocarpa aurorae n. sp.

Figs 7–8

Station AD 267: 14°54,9 N-61°08,9 W, 77m. (MNHN S1 POL.A 60, slide S1 2734). This species is dedicated my second grand-daughter: Aurore

A single specimen 2.5cm in length was fixed by a few basal rhizoids ( Fig. 7A ) which may represent tunic expansions or broken stolons. The tunic is wrinkled with irregular swellings but not thick, clear in formalin. The siphons are sessile at a short distance from each other. Removed from the tunic the body is elongated yellowish and opaque with brown pigment on the siphons. Internally both siphons have a large velum with patches of chalky pigment ( Fig. 7B ) a colour which is also present in the oral tentacles. The 16 oral tentacles are curled alternating with button-like smaller ones. The prepharyngeal area has no papillae. The dorsal tubercle opens in a slit and is located in a deep V of the prepharyngeal band ( Fig. 7B ). The branchial sac has 4 low well spaced folds on each side ( Fig.8 ). There is a particularly wide space between the dorsal lamina and the first right branchial fold in the posterior region of the branchial sac with 20 longitudinal vessels ( Fig. 8 ). Between the folds there are only 2-3 stigmata in a mesh.

The digestive loop ( Fig. 7B ) is loosely attached to the body wall and occupies a small part of the left body side. The olive shaped stomach is very posterior with indistinct folds. The intestine forms an opened loop; the rectum is dorsal and vertical ending in an anus in 2 lips, the internal lip with a slit. The sausage-shaped polycarps are not arranged in lines ( Fig. 7B ): on the right side 6 of them are dorsal and 4 are grouped ventrally On the left body side 3 polycarps are ventral and one located in the gut loop. Some polycarps are branched. The tubular ovary is sided with 2 lines of testis vesicles ( Fig. 7C ). The polycarps are loosely linked to the body wall by trabeculae. Numerous clear endocarps of varied sizes are scattered on the whole internal body wall ( Fig. 7B ). A line of thread like papillae limits the base of the atrial velum.

The combination of an elongate body shape, basal thread-like roots, 4 low spaced branchial folds, the absence of a secondary intestinal loop and the irregular arrangement of the oval polycarps do not correspond to any styelid species recorded in the Atlantic Ocean and leads to a new species. The anatomical organisation may fit as well a Polycarpa species or a Polyandrocarpa but the general aspect of the Madibenthos specimen resembles the anatomy of the other species of Polyandrocarpa from Martinique which essentially differ by their absence of endocarps which are numerous here. Provisionally without genetic information the Madibenthos specimen is placed in the genus Polyandrocarpa .

Figures

FIGURE 7. Polyandrocarpa aurorae n.sp.. A, zooid, scale bar = 5mm; B,body ventrally opened, scale bar = 1cm; C, detail of some polycarps.

FIGURE 8. Polyandrocarpa aurorae n.sp. Branchial sac cut transversallyand stained, scale bar = 1cm.