Cnemidocarpa irene ( Hartmeyer 1906 )

Monniot, Françoise, 2018, Ascidians collected during the Madibenthos expedition in Martinique: 2. Stolidobranchia, Styelidae, Zootaxa 4410 (2), pp. 291-318 : 308-311

Cnemidocarpa irene ( Hartmeyer 1906)

Figs 16-17-18

Styela irene Hartmeyer, 1906

Cnemidocarpa areolata: Monniot C. 1983 , Monniot C. & F. 1984 and synonymy.

Cnemidocarpa irene: Nishikawa 1991 and synonymy

Stations : AB: 102, 123, 150, 155, 157, 159, 163, 169, 173, 181, 183, 191, 193, 195, 197, 199, 350, 353. AD: 111, 150, 208. AM: 0 6, 20. AR: 72, 89, 101, 103, 107, 110, 170, 182, 353. AS: 66. ( MNHN S1 CNE 239-240 )

The size of the numerous specimens collected varies from 2cm to 5cm but most of them measure 2.5 to 3.5 cm in length. Their aspect varies depending on the presence of epibionts and on a more or less dark colour but the tunic is always corrugated with bumps and deep ridges ( Fig.18A ). The siphons are sessile, more or less distant from each other. The tunic is thick, cartilaginous and internally white. The body is attached by its left or posterior side.

Removed from the tunic the siphons are black and the body wall dark brown (in formalin) ( Fig 17A ) except in a few paler specimens. There is a large velum lining both siphons; the oral tentacles are dark brown, not numerous, 20 of them counted in a medium size specimen ( Fig.17A ). The pharyngeal band is double. There are no papillae on the prepharyngeal space. The dorsal tubercle is U-shaped with generally one horn curved externally. The dorsal lamina is flat and low ( Figs 16B , 17B ). The 4 folds on each side are high but do not overlap ( Figs 16B , 17B ); the branchial tissue is brown and sometimes very dark. The longitudinal vessels of each fold converge and unite without papillae at the oesophagus level. It is difficult to exactly determine whether a longitudinal vessel belongs to a fold or not as they are spaced at the base of the folds. An example of a branchial formula in a specimen 3.5cm large is:

R- E- 9 (12) 8 (13) 8 (11) 8 (9) 5 - DL - 7 (10) 9 (14)7 (13) 8 (13) 6 –E- L

There are 7 to 9 stigmata in a mesh between the folds, parastigmatic vessels are present.

The body wall is generally very dark and the muscular design is often difficult to see except in paler specimens ( Fig.16A ). Muscular longitudinal bundles well spaced extend from each siphon to the body sides where they divide in a span; they are crossed by a dense network of thin transverse muscular fibres. The digestive tract ( Figs 16B , 17B ) occupies half of the left body side and is tightly attached to the body wall until the extremity of the rectum. The anus ends with numerous petal-like lobes ( Fig. 18B ). The stomach with 18 to 20 longitudinal folds is short, not distinctly separated from the intestine it has no caecum. Numerous foliated endocarps are placed around the first gut loop but also along the internal side of the loop ( Fig. 16A , 17A ). On the remainder of the body wall the number of endocarps is very variable, either one or 2 between each gonad ( Fig. 16A ) or several endocarps around the gonads and elsewhere ( Fig.17A ).

The number of gonads varies and does not depend on the specimen size. They are from 2 to 6 on the right side and 1 to 4 on the left side. Each gonad is a long tubular ovary with numerous testis vesicles on each side ( Fig. 16A , 17A ); some of them are bifurcated ( Fig. 16A ). The sperm ducts unite in a single duct at the surface of the ovary ending in a short tube. The male papilla can be simple but in the majority of the specimens its extremity is divided in 2 or several lobes ( Fig. 18B ). The oviduct is short with a fringed aperture situated against the body wall and under the male papilla.

A ring of thread-like tentacles lies at the base of the atrial velum ( Fig.18B ).

C. irene is the single Cnemidocarpa species known in the Caribbean area. Its taxonomic status has changed several times. It was described and figured from Guadeloupe and Martinique by C. Monniot (1983) under the name Cnemidocarpa areolata ( Heller, 1878) . After examination of Heller’s type Monniot & Monniot (1984) considered the Caribbean material as different from Heller’s type but identical to the Australian C. valborg Hartmeyer, 1919 and some other synonyms. Nishikawa (1991) examined the type of C. irene ( Hartmeyer 1906) and found it similar to material from Japan and other Pacific regions and established a synonymy with the West Indies species. C. irene has also been more recently recorded from Cabo Verde Islands ( Monniot 1994) and it is common in Brazil (Rocha et al. 2012). It is obviously an invading species.

Figures

FIGURE 16. Cnemidocarpa irene station AS 66 not stained. A, dissection; B, branchial sac.Scale bars = 1cm.

FIGURE 17. Cnemidocarpa irene station AD 150. A, dissection not stained; B, branchial sac stained.Scale bars =1cm.

FIGURE18. Cnemidocarpa irene A, threespecimens informalin, scalebars = 1cm; B,detail ofthe gonoducts, anus and atrial aperture, scale bar = 2mm.