Actinocyclus in the Red Sea?

July 8, 1998
From: Erwin Koehler


Dear Bill

I send 2 photos to you. I took them in the Red Sea at a nightdive in October 97. The size of the slug is about 1.5 cm (maybe smaller), depth 6-7m, place: Shabror, near Marsa Alam, Egypt. The rhinopores remind me of genus Dendrodoris. The thing at the back looked like a little bubble or ball, not like gills. Can you turn my "no idea" into ID?

Thank you

Erwin
Erwin Koehler
Darmstadt, GERMANY.

E.Koehler@deutschepost.de

Koehler, E., 1998 (Jul 8) Actinocyclus in the Red Sea?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/107

Note added 4 August 2004: This is Actinocyclus verrucosus.

Erwin,
Your animal is almost certainly Actinocyclus japonicus, and if it is only 1.5cm long it is a juvenile because it can grow to about 12cm long. It is very hard and leathery to touch and the little "bubble-like" circlet of gills is very characteristic of Actinocyclus and the related genus Hallaxa. I often describe them as "goblet" shaped because of their resemblance to a wine glass. Some authors consider Actinocyclus and Hallaxa to belong in a distinct family Actinocyclidae. Apart from their goblet-shaped gill circlet their radular teeth bear a remarkable resemblance to those of some chromodorids. This is possibly a functional convergence as like, chromodorids, they tend to feed on sponges without spicules. I have found Actinocyclus and a number of species of Hallaxa on Dendroceratid sponges of the family Halisarcidae. These sponges form tough leathery, almost slimy layers over rocks or other hard surfaces and look more like a compound ascidian colony than a sponge, though they lack any obvious pores. Specimens of Actinocyclus japonicus range in colour and shape from a pale yellow with few spots and nodules to a very nodulose darker form. ... Bill Rudman

Rudman, W.B., 1998 (Jul 8). Comment on Actinocyclus in the Red Sea? by Erwin Koehler. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/107

Related messages

  1. Actinocyclus verrucosus on prey sponge
    From: Scott Johnson, February 1, 2006
  2. Actinocyclus verrucosus from Hawaii
    From: Scott Johnson, September 23, 2005
  3. Actinocyclus verrucosus (?) from the Marshall Islands
    From: Scott Johnson, September 23, 2005
  4. Re: Actinocyclus japonicus eggs
    From: Gary Cobb, September 17, 2005
  5. Actinocyclus verrucosus from southern Queensland
    From: Gary Cobb, September 9, 2005
  6. Actinocyclus verrucosus from eastern Australia [2]
    From: Bill Rudman, August 10, 2005
  7. Actinocyclus verrucosus from eastern Australia [3]
    From: Bill Rudman, August 10, 2005
  8. Actinocyclus verrucosus from eastern Australia
    From: Bill Rudman, August 4, 2005
  9. Actinocyclus verrucosus - egg ribbon
    From: Bill Rudman, August 4, 2005
  10. Actinocyclus japonicus eggs
    From: Wayne Ellis, October 17, 1998

Show factsheet and all related messages