Hexabranchus sanguineus

November 20, 1999
From: Danielle Manacop

Hello my name is Danielle,

I would like to know more about the Hexabranchus sanguineus. I have a report due in 2 weeks and I am having trouble finding information. If you could please help me by telling me of what you know, and if you know of sites about them then please could you e-mail them to me. I need to know all about them, like their sexual reproduction, eating habits, interior organs, and things like that. I live on Saipan and our library does not contain much information on these organisms. If you could please help. Please e-mail me.

Thank you
Danielle Manacop


Manacop, D., 1999 (Nov 20) Hexabranchus sanguineus. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/1551

Dear Danielle,
I guess the Saipan your are talking of is in the Northern Mariana Islands north of Guam. Sounds a great place to find nudibranchs.

I have prepared a list of references on Hexabranchus sanguineus for you. Hopefully you will be able to obtain a few of these. The one by Francis in The Veliger is quite comprehensive.

In brief, Hexabranchus can be found in tropical waters worldwide from the intertidal to quite deep water - deeper than scuba divers can safely venture. It is a sponge-feeder but does not seem to be a specialised feeder on a particular species of sponge. The skeletal spicules of many encrusting sponges have been found in its stomach. Hexabranchus seems to breed all year, though in the Red Sea it is reported to stop breeding during the coldest period of the year. The bright red egg ribbons are quite characteristic.

Like many nudibranchs, Hexabranchus seems to be protected somehow from fish predation. The bright red colour on their mantle has long been considered a 'warning' colouration to fish. In the last ten years or so we now have evidence to show that Hexabranchus has distasteful, and potentially toxic, chemicals in its body and egg masses. These chemical molecules (macrolides) are almost identical to antifeedant chemicals found in Halichondria, one of the sponges that Hexabranchus eats. The sponge produces the molecules to protect it from fish predation. It is thought that Hexabranchus obtains the molecules from the sponge during feeding, and after modifying the structure of the molecule slightly, stores them in its skin and egg masses for its own protection.

I hope this will help you with your project. You will also find more information in the other messages about Hexabranchus below yours on this page. Also have a look at the Index of general topics for more information on other aspects of dorid and nudibranch biology.

Best wishes,
Bill Rudman.

Rudman, W.B., 1999 (Nov 20). Comment on Hexabranchus sanguineus by Danielle Manacop. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/1551

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