Breeding aggregation of Chelidonura punctata

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