Dear Fabrice,

This is Chelidonura punctata which is found in the western Indian Ocean and around the northern Indian Ocean to Thailand.

Best wishes,
Bill Rudman

Dear Eric,

This is Chelidonura punctata. It is not a nudibranch, but belongs to a related group of sea slugs called cephalaspidians or Bubble Shells because many of the group have external, bubble-shaped, shells. Until quite recently we had no idea what species of Chelidonura ate, and because they were often found and photographed on large coral colonies - like in your photo - authors of many colour picture books wrote that they fed on coral mucus! We now know they feed on small flatworms, and the most likely reason they are found on large corals, is because small flatworms occur there as well.

Species of Chelidonura, and other members of the family Aglajidae, have unique sensory bristles arranged in clusters around their mouth - which apparently are used to sense the chemical trails of flatworms. I have included a closeup alongside to show 3 of these clusters as whitish patches on the front of the head. You can see them more clearly in some wonderful photos of C. flavolobata in message #16039.

Best wishes,
Bill Rudman

Dear Valda,
It is good to get another record to complement Colin Ogden's [#14132] record from what I guess will be near the southern limits of its distribution. Previously known only from Tanzania and Madagascar, contributors to the Forum have greatly increased the known distribution of this species from South Africa in the south across to Thailand and Burma in the north east of the Indian Ocean.

Best wishes,
Bill Rudman

Dear Jose,
I am sorry you  missed the whale shark experience but I am glad you found this interesting cluster of Chelidonura punctata. They are definitely mating. In the close-up of one of your photos alongside you can see three animals forming a mating ring. Species of Chelidonura have their penis on the right side of the head and their female genital opening on the right side, about two-thirds of the way down the body. If you see and animal with its head on the right side just under the parapodial flap then you can be pretty sure it is mating. As they are hermaphrodites they can act as male and female at the same time. In this photo all three animals appear to be mating simultaneously.

There is a photo on the Forum showing three Chelidonura livida mating in a chain [see message #8036]. The Sea Hares are another group which can mate in chains like this [see Mating Chain Fact Sheet].

I am not sure if groups of Chelidonura together like this can be compared with the huge aggregations we sometimes find with Sea Hares [see Mass Mortality Fact Sheet]. I think the ecology of hunting carnivores would be different from that of grazing herbivores like the Sea Hares. Perhaps the Chelidonura were attracted by a population explosion of small flatworms. which they eat. We still have much to learn about these animals. They may be a lot smaller than Whale Sharks but they are just as fascinating.

Best wishes,
Bill Rudman

Dear Vie,
This is a nice find. It is a species, Chelidonura punctata which was only known from East Africa until the Forum participants started finding it as far east as Burma and Thailand. It is a good example of how interested amateurs can play an important role in building up our knowledge of these animals.

Best wishes,
Bill Rudman

Thanks Sergey,
As we get more records from the Andaman Sea region it is interesting to see how many species previously considered to be endemic to the western Indian Ocean have a distribution extending along the northern coasts of the Indian Ocean to Thailand and Burma
Best wishes,
Bill Rudman

Dear Philibert,
Yes this is Chelidonura punctata. The main colour difference with C. sandrana is that the yellow spots in that species, if present, are much smaller and are not found on the ventral surface, while in C. punctata the spots are relatively large and do occur on the sole of the foot. C. sandrana is also usually smaller. Although it can reach 20 mm in length, it is seldom more than half that size.

One interesting thing about your photo is the yellowish brown stain in the water at the posterior end of its body. This is the secretion from its yellow gland, which is a gland found only in the Aglajidae. Like the purple gland  found in the Sea Hares, its function is unknown.
Best wishes,
Bill Rudman

Dear Colin,
Your ID is correct, and yes I'm pretty sure this is a new record from South Africa. It is not a surprise that this species occurs on the tropical waters of eastern South Africa, but it is certainly good to have evidence.  Can I assume you saw it crawling over this live coral colony? Why I ask is that there are many photos of species of Chelidonura crawling over corals like this is popular colour photo books, sometimes with captions suggesting they feed on the coral mucus. We now know that the reason they crawl over corals like this is to search for their prey - small flat worms which often occur on coral colonies in large numbers.
Best wishes,
Bill Rudman

Thanks Marina,
Nice to get some more photos of this species from the western Indian Ocean
Best wishes,
Bill Rudman

Dear Erwin,
Thanks for this interesting information. Firstly with your earlier record from the Maldives, your finds are bringing Chelidonura punctata right across to the eastern side of the Indian Ocean.

'Trailing' in aglajids is quite a common phenomenon and often ends in mating. In aglajids the penis is on the right side of the head and the female genital opening is at the posterior end of the body. These animals therefore often mate 'head to tail' with the anterior one acting as female and the posterior one as male. Sometmes in the field, and often in captivity, aglajids will form mating chains of 5-10 animals with the most anterior one acting as female, the most posterior as male, and the ones in the middle acting as both male and female.

The jelly mass you describe them crawling out of is apparently a protective coat of mucus they often produce when they are resting or when they are disturbed. When crawling, aglajids secrete a coat of mucus which can cover their whole body, so they are really crawling along in a tube of mucus. When still this coat can increase to form a temporary 'nest'.
Best wishes,
Bill Rudman.

Dear Erwin,
This is Chelidonura punctata, a spectacularly coloured species of Chelidonura which seems to be restricted to the Indian Ocean.
Best wishes,
Bill Rudman.