Family AGNEZIIDAE

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Introduction

The family Agneziidae Monniot & Monniot, 1991 is a group of diverse genera. There are two subfamilies, Agneziinae Monniot & Monniot, 1991 with stigmata spiralling around cones or infundibula projecting into the pharynx, and Ciallusiinae Huus, 1937 with straight stigmata. The latter subfamily is not yet recorded from Australia. The family is distinguished by the loss of the longitudinal branchial vessels (present in most phlebobranchs), although vestiges in the form of bifid or undivided papillae are present on the transverse vessels.

In Agneziinae the test is thin and often has embedded sand making it stiff and brittle. However (in contrast to the Plurellidae), parts of the body wall are not embedded in the test—rather the body musculature is modified to take advantage of the stiff test in other ways. Thus, short parallel bands of muscles around its outer margin, and along each side of the antero-median apertures, tend to flatten the body. When the muscles are contracted the soft, thin sand-free strips of test in which the sessile apertures are located, are withdrawn and folds of hard, sandy test close over them as protective lips. The short parallel bands of muscle around the median line of the body occur in other taxa in which the sand-embedded test is thin enough to be brittle rather than tough, e.g. Molgula Forbes, 1848 has species in which the apertures can be withdrawn and covered by the stiff brittle test in the same way.

A single species of Agnezia Monniot & Monniot, 1991 (a replacement name for Agnesia Michaelsen, 1898) and three of Adagnesia Kott, 1963 are recorded from Australia. They are not recorded often and probably occur principally on the sea floor, a habitat seldom explored around this continent. Two of the Adagnesia species have a novel orientation of gonoducts through the gut loop and directed anteriorly between the distal limb or pole of the loop and the outside of the parietal body wall. The papillae on the transverse branchial vessels of Adagnesia are bifid but in Agnezia they are not divided.

Caenagnesia Ärnbäck, 1938 from the Antarctic, and Proagnesia Monniot & Monniot, 1973 from deep water, have not been recorded from Australia.

The family, (as Agnesiidae Huntsman, 1912), is discussed in Kott (1985).

General References

Ärnbäck-Christie-Linde, A. 1938. Ascidiacea. Further Zoological Results of the Swedish Antarctic Expedition, 1901-1903 3(4): 1-54

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.

Huntsman, A.G. 1912. Ascidians from the coasts of Canada. Transactions of the Royal Canadian Institute 9: 111-148

Huus, J. 1937. Ascidiaceae. pp. 545-692 in Kükenthal, W. & Krumbach, T. (eds). Handbuch der Zoologie. Berlin : Walter de Gruyter Vol. 5(2).

Kott, P. 1963. Adagnesia opaca gen. nov., sp. nov., a remarkable ascidian of the family Agnesiidae from Moreton Bay, Queensland. University of Queensland Papers, Department of Zoology 2(3): 75-79

Kott, P. 1985. The Australian Ascidiacea Pt 1, Phlebobranchia and Stolidobranchia. Memoirs of the Queensland Museum 23: 1-440

Monniot, C. & Monniot, F. 1973. Ascidies abyssales récoltées au cours de la campagne océanographique Biaçores par le Jean Charcot. Bulletin du Muséum National d'Histoire Naturelle, Paris [published 1907-1971] 3 93(121): 389-475

Monniot, C. & Monniot, F. 1991. Tunicata: peuplements d'ascidies profondes en Nouvelle-Calédonie. Diversité des stratégies adaptatives. In, Crosnier, A. (ed) Résultats des Campagnes MUSORSTOM. Vol. 8 Mém. Mus. Natl. Hist. Nat. Paris (4)151(A): 357–448.

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