Halgerda tessellata from Indian Ocean

March 16, 2009
From: Sandrine Flodrops


Concerning message #2950:

Dear Bill and Valda,
here are some pictures of Halgerda tessellata with the same pattern as in Valda Fraser's message. South Africa, Mayotte and Reunion have a lot of similarities in their sea slug fauna.

Locality: Balcon sur le bleu "Passe en S", 12 metres, Mayotte, Indian Ocean, 4 march 2009. Length: 25 mm . Photographer: Sandrine Flodrops.

I thinks it's interesting for the forum.
Best regards.
Sandrine.

hugues.flodrops@wanadoo.fr

Flodrops, S.H., 2009 (Mar 16) Halgerda tessellata from Indian Ocean. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22320

Dear Sandrine,

It is indeed interesting for the Forum. My first experience with this species was when I found a specimen in Tanzania [see Fact Sheet photo], so I was quite puzzled when I first saw western Pacific animals with a concentration of white near the mantle edge [see message #22035]. Whether we should consider these geographic differences to be 'just variations' or 'subspecies' or 'geographic species pairs', is really a semantic argument. What the differences indicate is that the Indian Ocean and Western Pacific populations have been isolated from each other for a long time. One valuable consequence of the Forum is the growing evidence we are getting of how the western Indian Ocean fauna stretches right across to Thailand, with Indian Ocean 'forms' rather than western Pacific 'forms' occurring their. For example, Erwin Koehler's animal from Thailand [message #3607] looks like the one from East Africa.

Best wishes,
Bill Rudman

Rudman, W.B., 2009 (Mar 16). Comment on Halgerda tessellata from Indian Ocean by Sandrine Flodrops. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/22320

Factsheet

Halgerda tessellata

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