Family CLAVELINIDAE

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Introduction

Species of the family Clavelinidae, Forbes & Hanley 1848, usually are colonial with partially or completely embedded zooids, length about 10 to 100 mm, and with four to 40 rows of stigmata. A few solitary species have been described in which a connection to another zooid has not been detected. In all species, the branchial and atrial apertures have smooth rims, internal longitudinal branchial vessels are not present in the pharynx and the gut loop is of various lengths-sometimes short, with the stomach halfway along the abdomen but sometimes three or four times the length of the thorax with the stomach near the distal end of the loop. Large gonads-a sac-like to tubular ovary and a mass of small pear-shaped male follicles-are enclosed by the gut loop. Strong thoracic longitudinal muscles extend from around the apertures or from each side of the endostyle, and converge to form a band along each side of the abdomen. Zooids are very contractile. The test is soft and transparent and usually does not have sand included. Buds are formed in the isolated terminal ampullae of a posterior abdominal vascular stolon. In this family, the regenerative tissue is mesodermal. Endodermal tissue from either the gut or the epicardial sacs is not involved in replication, although epicardial sacs, as in other aplousobranch families, are present. Eggs are fertilised in the atrial cavity or in the top of the oviduct at the posterior end of the thorax, where embryos are brooded in large numbers (up to 100). They are liberated as tailed larvae. The larval trunk is from 0.5 mm to 1.5 mm long, with wide, shallow adhesive organs, arranged triradially on a robust frontal plate.

Only two genera, Clavelina Savigny, 1816, and the monotypic Nephtheis Gould, 1856, are now recognised in this family (Kott 1990). The genus Clavelina is well represented in Australian tropical and temperate waters, but is not known from the Antarctic. Nephtheis occurs in tropical waters, which are part of its western Pacific range. The Australian fauna, which includes temperature species, appears to have tropical affinities.

General References

Forbes, E. & Hanley, S.C.T. 1952. A History of British Mollusca and their Shells. 1848–1952. London : John van Voorst Vol. 1,2 & 4 (appendix) pp. 1-54, 369-376, 244-246.

Gould, A.A. 1856. Mollusca and shells. In, United States Exploring Expedition during the Years 1838–1842 under the Command of Charles Wilkes Atlas: 1–16, pls 1–56. London : Wiley & Putnam.

Kott, P. 1990. The Australian Ascidiacea Pt 2, Aplousobranchia (1). Memoirs of the Queensland Museum 29(1): 1-266

Savigny, J.C. 1816. Recherches anatomiques sur les ascidies composées et sur les ascidies simples—Système de la classe des Ascidies pp. 1–239. In Mémoires sur les Animaux sans Vertèbres, Pt 2. Paris : G. Dufour.

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