Acochlidea
Order: ACOCHLIDEA
See message from Michael Schrödl & Timea P. Neusser [#15744 ] which summarises our knowledge of the group and describes their present research.
Related messages
Information on Tantulum elegans
August 31, 2006
From: Sarsha Lall
Could you please give me the taxonomic classification of the sea slug Tantulum elegans, giving especially the Family to which it belongs.
The only reference that I could find on this forum about Tantulum elegans is that it is found in a swamp in St. Vincent. Is this reference related to the work done by Harrison and Rankin 1976?
Do you know if it has been recorded anywhere else in the Caribbean?
With thanks,
Sarsha.
sarsha_l@yahoo.com
Lall, S., 2006 (Aug 31) Information on Tantulum elegans. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/17685Dear Sarsha,
Have a look at my comments to message #16865 and Michael Schrödl's message [#15744]. I am pretty sure the reference is Rankin, 1979. Michael Schrödl may be able to give you more up to date information, but these microscopic animals are difficult to find and difficult to 'dissect', so we still have much to learn about their biology, natural history and their phylogenetic relationships. Until that is done 'families' and even 'genera' are a bit tentative.
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Rankin, J. R. (1979) A freshwater shell-less mollusc from the Caribbean: structure, biotics, and contribution to a new understanding of the Acochlidioidea. R O M Life Sciences Contributions 116: 1-123.
Best wishes,
Bill Rudman
Are there freshwater sea slugs?
June 17, 2006
From: Dave
Hi.
My apologies if this was placed in the wrong area but I have only recently heard of a (or possibly several?) freshwater species of slug and after a lot of googling come across only vague refrences but no real details or species name(s). Would it be possible to finds out more information or if you'd rather, point me in a general direction?
Thanks,
Dave
wanabenaturalist@aol.com
Dave, 2006 (Jun 17) Are there freshwater sea slugs?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16865Dear Dave,
There is one Order of opisthobranchs - the Acochlidea - which have freshwater species. Most acochlidian species are small worm-like marine slugs found living between sandgrains - part of what we call the interstitial fauna. However some have invaded brackish water and others freshwater. One small species, Tantulum elegans, is found in a mountain swamp on the Caribbean island of St Vincent. However most of the others we know of are much larger than usual, up to 3 cm in length, and live in rivers and streams on several tropical Pacific islands.
I can't guarantee a complete list of freshwater species, but here are some I know of:
Strubellia paradoxa (Strubell, 1892) - Solomon Islands
Acochlidium amboiense Strubell, 1892 - Amboina, Indonesia
Acochlidium weberi bergh, 1896 - Flores, Indonesia
Acochlidium suteri Wawra, 1979 - Sumba, Indonesia
Acochlidium bayerfehlmanni Wawra, 1980 - Palau
Acochlidium fijiiensis Haynes & Kenchington - Fiji.
Tantulum elegans Rankin, 1979 - St Vincent Is., Caribbean
If anyone has photos of any of these species I would like to include them on the Forum.
See the message from Michael Schrödl & Timea P. Neusser [#15744] which summarises our knowledge of the group. A recent publication is:
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Haynes, A. & Kenchington, W. (1991) Acochlidium fijiiensis sp. nov. (Gastropoda: Opisthobranchia: Acochlidiacea) from Fiji. The Veliger, 34(2): 166-171.
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Rankin, J. R. (1979) A freshwater shell-less mollusc from the Caribbean: structure, biotics, and contribution to a new understanding of the Acochlidioidea. R O M Life Sciences Contributions 116: 1-123.
Best wishes,
Bill Rudman
Phylogeny and evolution of acochlidian opisthobranchs
February 6, 2006
From: M. Schrödl & T. P. Neusser
Acochlidian opisthobranchs are amongst the most fascinating gastropods combining an almost incredible number of aberrant morphological and biological features. Most of the 27 species known worldwide are marine, with tiny specimens inhabiting interstitial spaces of intertidal or (shallow) subtidal sands. As in other mesopsammic opisthobranchs, such as Rhodopemorpha, Philinoglossidae (Cephalaspidea), Platyhedyle (Sacoglossa), and Pseudovermidae (Nudibranchia), extreme ecological conditions are thought to have caused drastic morphological adaptations: miniaturization, development of an elongate, worm-like body shape, and reductions of shell, mantle cavity organs, pigments, and eyes. In addition, many interstitial acochlidian species show special reproductive features, e.g. the copulatory organs are modified to allow hypodermal fertilization, or are completely reduced. In the latter case, sperm transfer occurs via spermatophores. Several species forming spermatophores have separate sexes, a condition that is unique amongst the otherwise hermaphroditic opisthobranchs.
Some acochlidian species invaded brackish or even freshwater systems; again unique amongst opisthobranchs. With exception of the small limnic Tantulum elegans that was so far only reported from a mountain spring swamp on the Caribbean St. Vincent Island, there is an array of large (up to 3 cm) acochlidian species occurring in freshwater systems of several Indo-Pacific islands. Besides showing a remarkable (secondary?) gigantism, most of the latter species have giant penial papillae armed with cuticular spines and thorns, and a complex system of penial glands with so far unknown homology and functions.
Morphological knowledge on acochlidians still is largely restricted to external features and gross anatomy presented in old original descriptions. The current structural and systematic knowledge on acochlidians was reviewed recently by Sommerfeldt & Schrödl (2005). Within our current project on the "Phylogeny and Evolution of Acochlidia", we are preparing a detailed species by species account using modern histological techniques and 3D-visualization (see Neusser et al., 2005). Every help regarding biological observations, distributional data, or sending specimens for histological, ultrastructural or molecular analyses would be highly appreciated.
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Neusser, T.P., Haszprunar, G., Hess, M., Schrödl, M. 2005. Computerbased 3-dimensional reconstruction of the anatomy of Microhedyle remanei (Marcus, 1953), an interstitial acochlidian gastropod from Bermuda. Journal of Morphology 267: 231-247.
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Sommerfeldt, N. & Schrödl, M. 2005. Microanatomy of Hedylopsis ballantinei, a new interstitial acochlidian gastropod from the Red Sea, and its significance for phylogeny. Journal of Molluscan Studies, 71: 153-165.
Michael Schrödl & Timea P. Neusser
schroedl@zi.biologie.uni-muenchen.de
Schrödl, M. & Neusser, T.P., 2006 (Feb 6) Phylogeny and evolution of acochlidian opisthobranchs. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/15744Dear Michael & Timea,
I look forward to many more messages on these interstitial animals. They certainly deserve more 'press' than they normally get.
Best wishes,
Bill Rudman
