420 Dive Log Australasia OCTOBER 2026

This undescribed Coryphellina aeolid has autotomised at least three large cerata from the first row on the right side (compare to its left side). Short stubs are evident (arrowed) indicating the first stage of regeneration, to full cerata size, has commenced.

Autotomy in action. An undescribed Gymnodoris attacks a Unidentia aeolid. The foreground in the image is littered with writhing autotomised cerata. These have been cast off by the aeolid in the desperate attempt to distract the Gymnodoris - but to little effect in this case.

This Melibe viridis has cast off the first ceras on the left side. It is fairly common to see Melibe with missing cerata. With the loss of such a large appendage an efficient system of autotomy, sealing off the wound and recovery has developed. Research has shown that Melibe cerata undergo a cellular change in the autotomy plane allowing the cerata to “unglue” when the sphincter musculature contract rather than tearing away, allowing for a manageable uncomplicated repair process.

Aeolids aren’t the only sea slugs to autotomise appendages. Here the sacoglossan Lobiger viridis has cast off one of its four large parapodial appendages - the anterior left. These can unfurl and lay out horizontally in the first instance almost doubling in size the appearance of the slug creating a deimatic display, but if the aggravation continues they may be autotomised along with a sticky secretion and even writhe as a distraction. The disassociation point is arrowed.

Species of the sacoglossa genus Oxynoe are known to autotomise their tail under extreme agitation where it will continue to flex vigorously for some time as a distraction, not unlike a lizard. Left: An entire specimen of Oxynoe jacksoni with its long tail intact and assisting its attachment in a surge-prone habitat. Right: This specimen of Oxynoe jacksoni has lost its tail but was still feeding normally.

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DIVE LOG Australasia #420 Oct ‘ 26

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