- . ; ' . V I • ' . .. ;.""' ....il ¥': 4?..,) AUSTRAliAN NATURAl HISTflRY ~~ .. ~~ ,~ RCH 1976 VOLUME 18 NO.9 $1* Hermit-crabs aren't really hermits. In fact most of them are quite gregarious. Neither are they crabs. The Southern Red They have much more in common Hermit-Crab with lobsters or crayfish and could be regarded as a soft-bellied cousin which sticks its tail in an old mollusc shell for protection. These enigmatic crustaceans depend entirely upon a supply of old sea shells to survive. Without these dead mollusc shells to protect their soft abdomens, would the hermit-crabs turn to discarded tin cans or bottles as a substitute? Learn about these creatures and many other aspects of zoology, anthropology, geology, our environment and all of the diverse things that happen at your Australian Museum by joining TftMS The Australian Museum Society-TAMS. Just ring 33-5523-in the morning only­ or write to TAMS, The Australian Museum, 6-8 College Street, Sydney, and all the details will be sent out to you. MARCHAUSTRAliAN 1976 VOLUME 18 NUMBER 9 PUBLISHED QUARTERLY NATURAl SV THE AUSTRALIAN MUSEUM. HISTORY 6·8 COLLEGE STREET , SYDNEY PRESIDENT, MICHAEL PITMAN ACTING DIRECTOR, DESMOND GRIFFIN SNAILS WITHOUT SHELLS 310 BY J. B. BURCH THE REDISCOVERY OF LUFI 316 BY PETER D. DWYER DISGUISE DEFENSE AND AGGRESSION 324 BY BARRY C. RUSSELL THE WAYANG WORLD OF THE BALINESE 330 BY ZOE WAKELIN-KING COVER: A modern Balinese BIRDS FROM AUSTRALIA'S PAST 338 shadow puppet of Hanoman, BY P. VICKERS R ICH AND G. F. VAN TETS the white monkey - hero of the Ramayana. Its wayang (shadow) appears on the back cover. (Photos: Gregory Millen/ IN REVIEW The Australian Museum) IN GENERAL AND IN PARTICULAR 342 EDITOR/DESIGNE R NANCY SM ITH Annual S ubscription: $4.50 -Australia: $5-New Zealand and New ASSISTANT EDI TOR G umea: $6-other countries. Single copies: $1 ($ 1.40 posted ROBERT STEWART A ustralia ): $1.45-New Zealand and New Guinea: $ 1.70- other PRODUCTION ASS I ST ANT countnes. Cheque o r money order payable to The Australian LEAH RYAN Museum sho uld be sent to The Secretary. The Australian Museum. C l RCULATION PO Box A 285. Sydney South 2001. Overseas subscribers please note ROY H ELM that rates are to be paid in A ustralian currency. EDITORIAL COMMITTEE HAROLD COGGER Opinio ns expressed by the authors are their own a nd do not K INGSLEY GREGG necessarily represent the policies o r view s o f T he Australian PATRICIA McDONALD Museum. · RONALD'STRAHAN 309 • RECQMMEN0 £ 0 R ETAIL PRI CE INTERNATIONAL ST ANDARD SERIAL "''UMUER 000• ·9840 SNAILS WITHOUT SHELLS BY J. B. BURCH he largest group of molluscs, the gastropods or the native species. Tsnails, are soft-bodied invertebrate animals with The ancestors of slugs were snails with large well· their internal organs enclosed in a hard, usually developed shells. A snail's shell is its means of spiralled shell, composed mainly of calcium carbonate. protection from periods of unfavourable climate, Not all snails have this protective covering. These especially drought, and from predators from which the naked molluscs are called slugs, snails without external shell not only provides stiff mechanical resistance, but shells. Their shells have been lost through a long also criptic coloration by which to escape notice. Slugs evolutionary process which continually reduced the no longer have this means of protection and so small relative size and thickness of the shell. The fact that cracks and crevices that would otherwise be inaccess­ slugs do not have external shells does not necessarily ible now provide a refuge from enemies and a cool, imply that they do not have internal shells. Most slugs moist and dark environment during the day and during have a small bit of remnant shell buried within their hot, dry periods. Although still quite 'sluggish' in mantle (the hump or triangular patch on their dorsal movement, the reduction and loss of shell in semi­ surface). In one slug (Testacella) the small remnant slugs and slugs has probably allowed somewhat greater shell is not imbedded in the mantle but actually is still speed, at least in some of the slug and slug-like groups. external. Slugs are well-known but unfortunately those A protective device exhibited by slugs may be a best known to Australians are the introduced pests mucus noxious to their potential predators. Some from Europe, the common garden slugs, such as the slugs are known to be distasteful to predators which spotted Leopard Slug (Limax maximus). Australia's normally eat shelled snails. The bright colors of animals truly native slugs are found in the less urbanized areas, with disagreeable flavors often serve as a warning of especially in bush country and rainforests. They are their bad taste to potential enemies. A predator will not only among the most colourful in the world, but rarely make a second meal of a gastronomically foul are also among the most scientifically interesting; species. The bright colours of some slugs provide such however, little is known about the biology of most of a warning. JACK BURCH, formerly Professor of Zoology at the University of Michigan, USA, is Curator of Molluscs at The Australian 310 AUS TRALIAN NATURAL H IST ORY Why is there a tendency for different land snail calcareous rock formations, are such regions. groups to evolve slug-like and slug forms? The answer The land slugs of the world belong to eleven probably lies in the snails' response to their environ­ families. The semi-slugs, i.e., those in the process of ment. Snails have four basic needs: moisture, food, evolving into a slug condition but still possessing a calcium and shelter. Calcium is needed for the con­ functional external shell, occur in two of these same struction of their shell and the shell in turn helps to families, plus eight additional families which do not conserve body moisture, although they still need contain true slugs, but to which some of the true moist shelters during the drier daytime periods. The slug families are closely related. Thus, slugs do not importance of moisture to land molluscs cannot be form a natural group among themselves, most of the over-emphasised. In their evolutionary history, snails slug families each having closer relatives among one with a rather constant su pply of moisture but little of the shelled groups than to another slug group. 'Slug' calcium could still survive quite well, assuming food refers to a body type (a shell-less snail), and not to an was available and predation not too severe. Under overall taxonomic group. such favourable moisture conditions, the protective The slugs of Australia may be grouped into seven value of the shell for preserving water would be families, of which three, the Limacidae (including the diminished. In fact, the bulky, heavy shell, which also Milacinae), Arionidae and Testacellidae, have been requires a considerable amount of metabolic energy introduced from Europe. The two species in Australi a to construct, might prove to be a disadvantage. There· of the fourth introduced family, the Veronicellidae, fore, under such circumstances, small mutations probably came from Africa and from South America reducing the shell would be selected for rather than or the West Indies. The three native slug families are Helicarion, a semi­ the Rathouisiidae, Cystopeltidae and Athoracophoridae. slug, in which the against. As might be expected, slug and semi-slug mantle flaps nearly species are abundant in regions with high rainfall and Another family, the Helicarionidae, although not full conceal the reduced reduced availability of calcium. Australia's eastern slugs, are semi-slugs-well on their way to becoming shell. This specimen was found in humid subtropical and tropical forests, which generally slugs. These semi-slugs are more common in Australia Chichester State Forest by W.F. Ponder and Museum. He is one of the world's leading authoritie~ on freshwater and t errestrial molluscs. P.H. Colman. VOLUME 18 NUMBER 9 311 The bright scarlet than the native true slugs. The Athoracophoridae are a most interesting relict Triboniophorus from near Narrabri, The Rathouisiidae have few species, two of which group, restricted in distribution to eastern Australia, New South Wales. are rare and found in Queensland, and several others New Zealand, New Hebrides, New Caledonia, New Co llected by R. Tali ana. in New Guinea, the Ph ilippines, western India, Indo­ Britain and the Admiralty Islands. Any close relatives China and China. The Australian species, triangular in seem to have vanished in antiquity •. their only distant cross-section and often reaching 4cm or more in present-day relatives being the archaic Succineidae, length, are carnivorous as can be determined by their world-wide in distribution. The athoracophorid's radular teeth, but the type of animals on which they internal respiratory sac or 'lung', instead of being feed is not known. In fact, very little is known about an entirely sac-like space, contains a system of the Australian rat houisiids. Their method of tentacle branching tubes. This impressed the early investi­ (eye stalk) retraction, is basicall y different from other gators, reminding them of the t rachial respiratory land snails. While their eyes sit at the top of the upper system of insects. Accordingly, these slugs were placed and larger pair of tentacles, and the tentacles can be in a separate order, to which the name Tracheopul­ shortened by contraction, the eyes and stalks can monata was applied. Several other peculiar characteris­ neither be inverted nor withdrawn into the slug's tics distinguish the athoracophorid slug s. For example, haemocoel or body cavity. A bit more is known about they have only two tentacles, one pair on the head, t he Cystopeltidae which is an exclusively Austra lian rather than two pair like other 'land pulmonates'.