Paraganitus sp
Order: ACOCHLIDEA
Suborder: MICROHEDYLOIDEA
Family: Microhedylidae
DISTRIBUTION
Known only from tropical Pacific
PHOTO
extracted from a shallow subtidal sand sample from the Palolo Deep reserve on Upolu Island, Western Samoa. 4 mm when crawling. Photo: Michael Schroedl.
This is the first report of the interstitial acochlidian genus Paraganitus from Western Samoa. The specimen (4 mm when crawling) was extracted from a shallow subtidal sand sample from the Palolo Deep reserve on Upolu Island. The species may be P. ellynnae Challis, 1968, that was originally described from the Solomon Islands and later reported from some other tropical Indo-Pacific localities. Internally, Paraganitus (as well as Ganitus) is characterized by having single sacoglossan-like, dagger-shaped radular teeth; rhinophores are relatively short in Paraganitus while completely reduced in Ganitus.
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Challis, D.A. 1968. A new genus and species of the order Acochlidiacea (Mollusca: Opisthobranchia) from Melanesia. Transactions of the Royal Society New Zealand (Biol. Sci.) 10: 191-197.
Schroedl, M., 2006 (February 3) Paraganitus sp [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/parasp
Related messages
Paraganitus sp. from Western Samoa
February 6, 2006
From: Michael Schroedl
Dear Bill,
This is the first report of the interstitial acochlidian genus Paraganitus from Western Samoa. The specimen (4 mm when crawling) was extracted from a shallow subtidal sand sample from the Palolo Deep reserve on Upolu Island. The species may be P. ellynnae Challis, 1968, that was originally described from the Solomon Islands and later reported from some other tropical Indo-Pacific localities. I think Clay Carson's "Microhedyle sp." from Guam [message #251 ] may refer to P. ellynnae as well, since the very elongate visceral hump that is coiled when the animal is disturbed seems characteristic for this species. Internally, Paraganitus (as well as Ganitus) is characterized by having single sacoglossan-like, dagger-shaped radular teeth; rhinophores are relatively short in Paraganitus while completely reduced in Ganitus.
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Challis, D.A. 1968. A new genus and species of the order Acochlidiacea (Mollusca: Opisthobranchia) from Melanesia. Transactions of the Royal Society New Zealand (Biol. Sci.) 10: 191-197.
Michael Schroedl
schroedl@zi.biologie.uni-muenchen.de
Schroedl, M., 2006 (Feb 6) Paraganitus sp. from Western Samoa. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/15739Dear Michael,
Thanks for drawing our attention to this fascinating group of slugs - part of the interstitial fauna - so called because they live between the 'interstices' or small spaces between the sandgrains. Most are very worm-like in shape, and as we suspect they have evolved from larger forms, the worm-like shape has been achieved by losing and modifying both internal and external body parts. because they have apparently 'lost' so much it makes it difficult to know just who their ancestors were.
I knew Derek Challis well when I was a student at Auckland University and watching him diligently sifting and seiving sand and finding these fascinating hair-like slugs has given me a life long interest in them - although I must admit I am almost a complete failure at finding them.
I would agree that your animal is most probably his P. ellynae. However I don't think Clay's animal is the same. It is not that clear in the photo, so you may have missed it, but the pair of recurved tentacles are in fact rhinophores not the oral tentacles, so it is quite different from Paraganitus with very reduced rhinophores. I note in my reply to Clay's message that I suggested it might be Microhedyle cornuta. I'm afraid I can't recall why I put it in the genus Microhedyle, but it is a species described by Challis as Hedylopsis cornuta Challis, 1970, which is characterised by the long recurved 'hornlike' rhinophores. In an earlier paper it is named Microhedyle sp. 1. (Challis, 1969).
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Challis, D. A. (1969) An ecological account of the marine interstitial opisthobranchs of the British Solomon Islands Protectorate. Philosophical Transactions of the Royal Society, B 255: 527-539.
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Challis, D. A. (1970) Hedylopsis cornuta and Microhedyle verrucosa, two new Acochlidiacea (Mollusca: Opisthobranchia) from the Solomon Islands Protectorate. Transactions of the Royal Society of New Zealand, Biological Sciences, 12: 29-40.
Best wishes,
Bill Rudman
