December 14, 2006
From: Hans Kemps
Dear Slug Forum,
A friend of mine phtographed this charging dorid at Ningaloo Reef. Would you be able to help us with the identification and an explanation for this unsluglike behaviour? Thank you!
Locality: Ningaloo Reef, 10 m, Western Australia, Indian Ocean. Photographer: Craig Kitson.
email@example.comKemp, H., 2006 (Dec 14) Charging slug? - Aphelodoris karpa. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/18997
It's a bit hard from a still photo to get the feeling that it is 'charging towards the viewer' but it certainly seems to be off the ground so I'll take your word that it was moving towards the photographer with unsluglike haste.
As it happens I think I have an explanation for you. This dorid, Aphelodoris karpas, has only recently been descibed so we know very little about its biology. However one thing that Nerida Wilson noted about this animal in her description was that it can swim by an up and down [dorso-ventral] flexion of the whole body, much like the Spanish Dancer, Hexabranchus sanguineus. I have no idea how fast they swim once they are moving, but certainly it is much faster than they crawl. You don't mention how large the animal was, but this species can reach at least 10 cm in length - so I guess if you saw something that size swimming towards your camera lens you could describe it as 'charging'. But 'charging' suggests they are aiming at something, and I am afraid that nudibranchs, although they have small eyes, are effectively blind, so the direction they travel in when swimming, is quite by chance.