Cnemidocarpa pfefferi ( Michaelsen, 1898 )

Primo, Carmen & Vázquez, Elsa, 2007, Ascidians collected during the Spanish Antarctic expedition CIEMAR 99 / 00 in the Bransfield and Gerlache Straits, Journal of Natural History 41 (29 - 32), pp. 1775-1810 : 1798-1801

Cnemidocarpa pfefferi ( Michaelsen, 1898)

Styela pfefferi Michaelsen, 1898 ; Michaelsen 1900, 1907; Kott 1969.

Tethium serpentina Sluiter, 1912 .

Styela serpentina: Sluiter 1914 ; Van Name 1945; Kott 1969.

? Styela subpinguis Herdman, 1923 .

Styela paessleri: Kott 1954 ; Vinogradova 1962.

Cnemidocarpa pfefferi: Millar 1960 ; Monniot and Monniot 1983, 1994; Ramos-Esplá et al. 2005.

Distribution

New record: Bransfield Strait (Station B6: one specimen: 24 mm height; Station B7: one specimen; 25 mm height). Previously recorded: Antarctic Peninsula; South Shetland Islands; Davis, Ross, and Weddell seas ( Millar 1960; Vinogradova 1962; Monniot and Monniot 1983, 1994; Ramos-Esplá et al. 2005); South Georgia Islands ( Monniot and Monniot 1983); Kerguelen Island ( Kott 1954). From 66 to 433 m depth.

Description

This species, with transparent, soft and smooth tunic and four branchial folds, is easily recognizable by the gonad structure. There are two on each side of the body, formed by a tubular ovary with numerous short biramous branches; the testis follicles are intimately associated with the tips of these branches. The sperm ducts join the vas deferens on the medial surface of the ovary, running parallel to the oviduct.

Remarks

Although it has sometimes been confused with Styela paessleri Michaelsen, 1898 , the gonad structure is quite different since testis and ovary are not enclosed in a common envelope.

Cnemidocarpa verrucosa ( Lesson, 1830)

Cynthia verruosa Lesson, 1830 ; Cunninghan 1871.

Ascidia verrucosa: Dujardin 1840 .

Styela verrucosa: Michaelsen 1898, 1900 , 1907; Sluiter 1914.

Styela lactea Herdman, 1881 ; Herdman 1882, 1891, 1912, 1923; Hartmeyer 1927. Styela grandis Herdman, 1881 ; Herdman 1882, 1891.

Styela spirifera Michaelsen, 1898 ; Michaelsen 1900, 1907. Styela steineni Michaelsen, 1898 ; Michaelsen 1900, 1907. Styela flexibilis Sluiter, 1905 ; Sluiter 1906. Styela spectabilis Herdman, 1910 . Tethyum lacteum: Hartmeyer 1911, 1912 . Tethyum spectabile: Hartmeyer 1911 . Tethyum spiriferum: Hartmeyer 1911 . Tethyum steineni: Hartmeyer 1911 . Tethyum verrucosum: Hartmeyer 1911 . Cnemidocarpa verrucosa: Van Name 1945 ; Arnback-Christie-Linde 1950; Pérès 1952;

Vinogradova 1962; Kott 1954, 1969, 1971; Millar 1960, 1968; Monniot C 1970, 1978;

Vasseur 1974; Monniot and Monniot 1974, 1983, 1994; Tatián et al. 1998a, 1998b,

2005; Ramos-Esplá et al. 2005. Cnemidocarpa zenkevitchi Vinogradova, 1958 ; Vinogradova 1962; Kott 1969.

Distribution

New record: Bransfield Strait (Station B5: 18 specimens from 25 to 95 mm height). Previously recorded: Antarctic Region ( Kott 1954, 1969; Millar 1968; Monniot and Monniot 1983; Ramos-Esplá et al. 2005); Scotia Arc ( Tatián et al. 1998a, 1998b, 2005; Ramos-Esplá et al. 2005); Kerguelen ( Monniot and Monniot 1983) and Crozet Islands ( Millar 1960); Magellan Strait, Patagonia and Falkland Islands ( Millar 1960; Monniot and Monniot 1983). From 15 to 836 m depth.

Remarks

Cnemidocarpa verrucosa is easy to identify through the tunic that, although it can be very variable, is resistant and opaque (generally light pink or yellowish), but thin and flexible. The surface is covered by papillae (with spines in the young specimens). Other characters such as the body wall close to the tunic but separated, and four poorly marked branchial folds are characteristic of the species too. Two gonads on each side; one on the left is between body wall and gut loop. This species clearly differs from C. pfefferi because of the biramous branches of the ovaries of the last one.

Dicarpa insinuosa ( Sluiter, 1912)

Styela grahami Sluiter, 1905 ; Sluiter 1906, 1914; Kott 1969.

Tethyum insinuosum Sluiter, 1912 .

Styela insinuosa: Sluiter 1914 ; Herdman 1923; Van Name 1945; Kott 1954, 1969; Millar 1960.

Dicarpa insinuosa: Monniot and Monniot 1983, 1994 ; Tatián et al. 1998a, 1998b, 2005; Ramos-Esplá et al. 2005.

Distribution

New record: Bransfield Strait (Station B3: four specimens; Station B7: one specimen; from 12 to 28 mm height). Previously recorded: Antarctic Peninsula, Weddell Sea, Wilkes Land ( Kott 1954; Monniot and Monniot 1983, 1994; Ramos-Esplá et al. 2005); South Shetland

Islands ( Tatián et al. 1998a, 1998b; Ramos-Esplá et al. 2005); South Georgia Islands ( Monniot and Monniot 1983). From 18 to 620 m depth.

Remarks

Our specimens agree with the description by Kott (1969) under the name of Styela insinuosa . The genus Dicarpa , created by Millar (1955b), was initially described for only one species, D. simplex , the distinctive characters being: four-lobed siphons, endocarps in the whole body wall, simple oral tentacles, smooth dorsal lamina, three to four branchial folds and one Polycarpa -like gonad on each side. Later, more species were included and the characters that define the genus are the type of branchia and the presence of only one gonad on each side, although the morphology is variable. Dicarpa insinuosa has a tubular ovary and several groups of testicular follicles surrounding the ovary, especially abundant at the posterior end.

Dicarpa tricostata ( Millar, 1960)

( Figure 17 )

Cnemidocarpa tricostata Millar, 1960 .

Styelopsis tricostata: Kott 1969 .

Dicarpa tricostata: Monniot and Monniot 1980, 1994 .

Distribution

New record: Bransfield Strait (Station B7: one specimen). Previously recorded: Weddell Sea ( Monniot and Monniot 1994), Ross Sea ( Monniot and Monniot 1980), South Georgia Islands ( Millar 1960). From 35 to 462 m depth.

Description

Ovoid shape, 17 mm high and 9 mm across at the widest point. The lower part of the body narrows towards the base, which is covered by test hairs with a little adhered sand. No test hairs or foreign particles are present on the rest of the body, which is yellowish pink, smooth, very thin but tough.

Siphons, short, four-lobed, both dorsal and close to each other. There are over 32 simple branchial tentacles, of two sizes. The small dorsal tubercle is a simple oval transverse slit. The dorsal lamina, with a plain margin, is wider on the posterior part. The branchial sac has three longitudinal vessels on each side; up to 30 stigmata per mesh, with parastigmatic vessels. A short oesophagus is followed by the stomach, with internal folds and a small pyloric caecum. The intestine forms a closed gut loop after the stomach, and then bends anteriorly near the oesophagus. The anus has eight well-marked lobes. Only one gonad has been found, mainly situated on the left side, but it crosses the endostyle line, thus also occupying the right side ( Figure 17 ). The testes are located on the posterior side of the ovary. They are long narrow follicles arranged in a series along the length of the gonad. There are two long sperm ducts, one on each side of the body, projecting from both ends of the gonad, but not terminal. The oviducal opening was not observed.

Remarks

Our specimen is the largest collected up to now and agrees perfectly with the description of the holotype except in small details such as external appearance of the tunic—covered with wart-like swellings according to Millar (1960) —or the number of oral tentacles, which probably depends on the size. Monniot and Monniot (1980) described one gonad on each side, with the same general structure. The presence of two sperm ducts in the specimens with only one gonad may be a sign of the fusion of two initial gonads.

Figures

Figure 17. Dicarpa tricostata, open specimen without branchial sac; cut gonad.