Saturday, March 25, 2006
Nembrotha lineolata with its head inside an ascidian. According to Bill Rudman at the Sea Slug Forum, solitary ascidians like this, often known as 'sea squirts', have an outer sac which protects the delicate sieve-like basket which filters their food out of the sea water and encloses the rest of the body. It looks like species of Nembrotha feed on solitary ascidians by inserting their extensible oral tube through one of the siphons to get to the fleshier parts of the body.
Wednesday, March 22, 2006
Sunday, March 19, 2006
Wednesday, March 15, 2006
Diane and I got a bit of a shock last night at Sandy Bottom. Hanging out at about 15M, and just a few meters away from us, was a very large Manta Ray. I'm not sure how big he was, but he was bigger than Diane. Sorry, my heart was beating too hard to take a photo as he soared away from us.
Tuesday, March 14, 2006
Sunday, March 12, 2006
Friday, March 10, 2006
Tuesday, March 07, 2006
Sunday, March 05, 2006
The cyclone has finally passed without much trouble, leaving a clear, sunny Sunday. But it also left Sandy Bottom scoured by surge and strong currents. The bottom now has a layer of fine sediment a few inches deep. But we have seen this before at Sandy Bottom. Life will return quickly with new soft corals making their way up through the silt and sand. In a week or so, it should be back to normal. Who knows, the storm may have brought in a few new species just waiting to be discovered.
Saturday, March 04, 2006
Friday, March 03, 2006
Could this be a Spanish Dancer?
March 3, 2006 From: Brian Francisco
Is it possible that these photos are of a juvenille Spanish Dancer Hexabranchus sanguineus. This individual was quite small, about 12 mm, and I'm not sure I can count 6 gills.
Locality: Beach, 7 meters, East Timor, Banda Sea, 26 February 2006, Sandy Bottom. Length: 12mm. Photographer: Brian Francisco.
Thanks very much
Francisco, B., 2006 (Mar 3) Could this be a Spanish Dancer?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find.cfm?id=16000
Yes this is indeed a juvenile Hexabranchus. Good call! The gills in juveniles are quite interesting. The dorid nudibranchs are divided into two large groups depending on whether their gills can retract into a protective pocket Cryptobranchia or Eudoridoidea or do not have such a pocket Phanerobranchia or Anadoridoidea. Obviously in adults, Hexabranchus has no sign of a gill pocket and each gill is separately inserted into the skin. It would seem to be clearly a phanerobranch. However phanerobranchs are usually the elongate forms, such as the nembrothids, while the large flat dorids with wide mantle skirts are usually cryptobranchs, with a gill pocket. Cryptobranchs are also sponge feeders, like Hexabranchus, while the phanerobranchs are all specialised feeders on a wide variety of invertebrates. There are of course other anatomical differences.
However if you look at juvenile Hexabranchus, you can see there seems to be a ridge around the gills and the tissue inside that is translucent, without the colour pattern of the rest of the mantle. I wouldn't be surprised if that is all that is left of a gill pocket, which has been lost in the evolution of this species, but is still indicated in juveniles. Does that make Hexabranchus a very special cryptobranch, or does it suggests that it is a link between the two groups, indicating that the phanerobranchs evolved from the cryptobranchs? I wouldn't like to say.at this stage, but it is certainly something that students of phylogeny should consider. I'm glad you picture shows it so clearly. In living animals they gills can almost completely disappear.
Best wishes, Bill Rudman
Rudman, W.B., 2006 (Mar 3). Comment on Could this be a Spanish Dancer? by Brian Francisco. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find.cfm?id=16000