Tonna (gastropod)

The thin shell is ventricose, inflated, generally globular, rarely oblong and encircled with ribs. The spire is short. The outer lip is crenulated and sometimes denticulated throughout its whole length. The oblong aperture is very large and emarginated inferiorly. The columella is channeled. There is no operculum.

The animal is very large, so as scarcely to be contained within its shell. The head is broad, swollen before, supporting two long, slender, obtuse, distant tentacles, dilated towards the base, where the eyes are situated. The mouth is large, muscular, strong and retractile. The respiratory tube is pretty stout. Its cavity is capacious, entirely open, provided with two branchiae placed on the left side, the larger of which, describes a pretty large semicircle. The trunk is cylindrical, very much developed, flexible, capable of being turned in every direction at the will of the animal, and of elongating itself in a remarkable manner. It is furnished internally with several rows of hooks. The foot is ovate, large, fleshy, bordering all parts of the shell. It is rounded, widened, lobed and dilated before, with a horizontal furrow. The posterior extremity has no trace of an. operculum. The generative organ of the male is very retractile. [2]

Anterior view of a live Tonna galea held in a human hand

The genus Tonna comprehends a small number of species, some of which attain so remarkable a growth, that they are sometimes as large as a man's head. In fact the general appearance of the shell, of an inflated, thick-set form, calls up the image of a tun, whence is derived its generic name. Thus, the characters which make up these species are a form more or less inflated, girdled, and very globular. The spire is much shorter than the body whorl. This causes the size of the aperture, which almost always occupies two thirds of the length of the shell. [2]

The animals of the tuns are in general strongly colored, and painted with different tints which form bands and spottings upon their entire exterior. [2]

This marine species is cosmopolitan.

Species within the genus Tonna include:

Species brought into synonymy

• Brünnich, M. & Stejneger, L. 1772. Zoologiae Fundamenta Praelectionibus Academicis Accomodata. pp. 254.
• Röding, P.F. 1798. Museum Boltenianum sive Catalogus cimeliorum e tribus regnis naturae quae olim collegerat Joa. Hamburg : Trappii 199 pp.
• Lamarck, J.B.P.A. de 1801. Systeme des animaux sans vertebres, ou tableau general des classes, des ordres et des genres de ces animaux. Paris : Chez Deterville 432 pp.
• Link, H.F. 1807. Beschreibung der Naturalien Sammlung der Universität zu Rostock. Rostock : Alders Erben.
• Montfort, P.D. de 1810. Conchyliologie Systematique, et Classification Methodique des Coquilles. Paris : F. Schoell Vol. 2 676 + 16 pp.
• Forbes, E. 1852. On the Mollusca collected by Mr MacGillivray during the voyage of the Rattlesnake. pp. 360-386 in MacGillivray, J. (ed). Narrative of the Voyage of H.M.S. Rattlesnake, commanded by the late Captain Owen Stanley, R.N., F.R.S. etc, during the years 1846-1850. London : Lords Commissioners of the Admiralty Vol. II 395 pp.
• Rovereto, G. 1899. Prime ricerche sinonimiche sui generi dei gasteropodi. Atti della Società Ligustica de Scienze Naturali e Geografiche 10: 101-110
• Iredale, T. 1931. Australian molluscan notes. No. 1. Records of the Australian Museum 18(4): 201-235, pls xxii-xxv
• Iredale, T. & McMichael, D.F. 1962. A reference list of the marine Mollusca of New South Wales. Memoirs of the Australian Museum 11: 1-109
• Vaught, K.C. (1989). A classification of the living Mollusca. American Malacologists: Melbourne, FL (USA). ISBN 0-915826-22-4. XII, 195 pp
• Wilson, B. 1993. Australian Marine Shells. Prosobranch Gastropods. Kallaroo, Western Australia : Odyssey Publishing Vol. 1 408 pp.
• Gofas, S.; Le Renard, J.; Bouchet, P. (2001). Mollusca, in: Costello, M.J. et al. (Ed.) (2001). European register of marine species: a check-list of the marine species in Europe and a bibliography of guides to their identification. Collection Patrimoines Naturels, 50: pp. 180-213
• Rolán E., 2005. Malacological Fauna From The Cape Verde Archipelago. Part 1, Polyplacophora and Gastropoda
• Vos, C. (2007). A conchological Iconography (No. 13) - The family Tonnidae. 123 pp., 30 numb. plus 41 (1 col.) un-numb. text-figs, 33 maps., 63 col. pls, Conchbooks, Germany
• Beu, A.G., Bouchet, P. & Tröndlé, J. 2012. Tonnoidean gastropods of French Polynesia. Molluscan Research 32(2): 61-120

• Powell A. W. B., New Zealand Mollusca, Auckland, New Zealand 1979 ISBN 0-00-216906-1

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