Monandrocarpa humilis

Dataset
A new species of Monandrocarpa (Ascidiacea, Styelidae) from Vanuatu I. (South Pacific Ocean): Rank
SPECIES: Published in
Monniot, Françoise (2009): A new species of Monandrocarpa (Ascidiacea, Styelidae) from Vanuatu I. (South Pacific Ocean). Zootaxa 2044: 65-68, DOI: 10.5281/zenodo.186418

Classification

kingdom
Animalia: phylum
Chordata: class
Ascidiacea: order
Pleurogona: family
Styelidae: genus
Monandrocarpa: species
Monandrocarpa humilis

discussion

Remarks. Only a few species of the genus Monandrocarpa have been recorded: they belong to different oceans. They may be solitary or colonial, with a single testis lobe in each polycarp, a structure characteristic of the genus. Monandrocarpa abyssa Sanamyan & Sanamyan, 1999 is a deep sea solitary ascidian from the Antarctic. The 3 cm individuals are in balls on a peduncle. They possess only 2 branchial folds on each side, the stigmata are small and not numerous. The stomach is short and the rectum is long.

materials_examined

Type: Vanuatu, Espiritu Santo, Aore Island, 15 ° 31.92 ’ S – 167 ° 11.61 ’ E, 30 m, 30. I. 2000, coll. CRRF n ° CRCHO 463. (Registered in the Muséum National d’Histoire Naturelle Paris n ° S 1 MON 2) Several specimens, some of them solitary but others in groups of 2 or 3 individuals, were found attached to a colony of Amphicarpa agnata (Kott, 1985). The body is oval, 1 cm in maximum length, covered with sparse adhering sand (Fig. 1). Some individuals are sessile, others are erect on a common base making a short and thick stolon. The siphons are slightly protruding and well apart. The tunic is leathery, but the body remains soft. The internal body wall is opaque. In formalin it has a dark-pigmented superficial reticulate design. Internally, on each side of the body wall, a longitudinal darker pigmented band extends alongside the polycarp line. The siphons have strong sphincters. The body musculature forms a continuous network of thin fibres. The number of oral tentacles is variable, in 3 orders of size. The peripharyngeal band is dorsally curved in a low V; it has a single crest. The dorsal tubercle is button-like. The branchial tissue (Fig. 2) is thin and contains less pigment than other tissues. Among the 4 branchial folds, the first and the third, counted from the dorsal lamina, are higher. Two to 3 longitudinal vessels can be counted anteriorly between the folds, they progressively join the folds as the sac narrows posteriorly. A representative formula in a large specimen, near the peripharyngeal band is: R-E; 5 - 2 - 8 - 3 - 6 - 2 - 8 - 1 - DL- 8 - 3 - 5 - 2 - 6 - 3 - 6 - 1 - E-L There are 4 to 5 stigmata in a mesh between the folds. The number of stigmatal rows is difficult to count, but about 18 – 20, basally grouped two by two due to a more or less complete division by parastigmatic vessels. The last rows are narrow with only a few stigmata. The dorsal lamina forms a high blade. The digestive loop (Fig. 3 B) occupies a reduced posterior part of the left side (Fig. 3 A). The oesophagus is narrow and straight, well delimited from the long cylindrical stomach. There are 8 to 9 longitudinal stomach folds. The pyloric caecum is long. The intestine curves in a single closed loop. The anus with a plain edge opens close to the oesophagus entrance. A pigmented network of vessels covers the intestine. An endocarp lies in the loop (Fig. 3 B). Round endocarps are scattered on the body wall (Fig. 3 A), some of them intercalated between the polycarps. A ring of short thread-like papillae encircles the cloacal siphon. An average of 10 polycarps are arranged in a line on each body side along and close to the ventral line (Fig. 3 A). The left row curves to become parallel to the rectum. Each polycarp comprises a single testis follicle covered by the ovary which contains many oocytes (Fig. 3 C). The gonadal papillae are short and close together.

Name

Homonyms: Monandrocarpa humilis