Corella parallelogramma (Müller, 1776), Muller, 1776

Monniot, Françoise, 2013, The genus Corella (Ascidiacea, Phlebobranchia, Corellidae) in the Southern Hemisphere with description of a new species, Zootaxa 3702 (2), pp. 135-149 : 145

Corella parallelogramma (Müller, 1776)

Fig. 10

Ascidia parallelogramma Müller, 1776: 224 –226.

Corella parallelogramma: Alder & Hancock 1907 , Berrill 1950 and synonymy, Lambert, 2004.

Several specimens from Sweden, the Channel and the western Mediterranean Sea have been examined to evaluate the morphological variability. The body shape is always the same with a maximum size of 4cm ( Fig. 10 A). The siphons are not protruding and distant of twice their diameter. In life the body is more or less pigmented in red or yellow. The tunic is cartilaginous and vitreous. The body wall is thin. In addition to the muscular sphincters of the siphons, the body musculature is made of strong ribbons ( Fig. 10 BC). Over the anterior part of the body on each side, short and well separated longitudinal muscles arise from the base of the oral siphon, ( Fig 10 B,C). On the right side only a few short fibres start from the upper part of the ventral line and no muscles are found above the gut. On the left body side and on the dorsal side a series of transverse muscular bundles are interrupted in the middle of the body. This characteristic design ( Fig. 10 C) was observed in specimens of all localities. The oral tentacles are long and thin planted at the base of a thick rod. The pre-pharyngeal band has two rims, it is poorly indented around a Cshaded dorsal tubercle.The branchial sac has 22 to 25 longitudinal vessels on each side. The meshes are square and contain spiral stigmata of at least 7 turns ( Fig. 10 D). Very few exo-infundibula can be found and the stigmata rows appear regular. The dorsal papillae are pointed and arise from a tissue tightly united to the rectum. The digestive tract is located in the posterior part of the right side. The oesophagus opens by a wide membrane. It is short narrow and curved. The stomach is surrounded by the gonads and difficult to observe but about 10 longitudinal folds are present. The intestine forms a closed loop. It opens in a multilobate anus. The rectum adheres strongly to the dorsal lamina along its whole length. The gonads have not a precise outline. The testis has small vesicles arranged in ramified lobules spread over the internal side of the gut loop. The primary sperm ducts are few, on the internal side of the gonad and then they join on the external side of the gut loop to form a common duct lying along the oesophagus and the rectum. A protruding male papilla opens above but close to the anus ( Fig. 10 C). The ovary is located in the centre of the gut loop against the stomach. The oviduct is linked to the rectum.

C. parallelogramma differs from C. borealis and C. brewinae n. sp. by the musculature design, the gonad ducts and a larger number of stigmata turns. This shallow species is distributed along the European coast from Scandinavia down to the Mediterranean Sea.

Figures

FIGURE 10. Corella parallelogramma (Müller, 1776), specimen from Kristineberg (Sweden): A, right side of a specimen 36 mm long; B, left side of the body devoid of tunic; C, body opened along the ventral line, the tunic removed; D, part of the branchial sac.