409 Dive Log Australasia December 24

Swallow-Tailed Sea Slugs S ea Slugs of the Aglajidae family are not true nudibranchs, but instead belong to a group commonly called the headshield slugs or cephalaspideans - Order Cephalaspidea. The aglajids are ranked second in diversity among the families of Cephalaspidea. They have a broad triangular headshield the broad leading edge of which possesses tufts of sensory bristles - for testing the substate in search of their prey, two large parapodia - lateral extensions of the foot that wrap-up in varying degrees over the mostly tubular-shaped bodies, a pair of posterior caudal lobes or “tails” of varying length and a reduced internal shell. They are active carnivore predators moving quickly across and through the substrate in their hunt for prey. (Note: The sp. numbers refer to species on the NudibranchDomain.org website) An Assortment of Aglajids - Part 1

Above: Four presentations of Mariaglaja tsurugensis ( Mariaglaja sandrana is a well-known synonym as is the less well known Chelidonura babai) . Previously placed in the Chelidonura genus, molecular sequencing found them to be genetically indistinguishable from each other and separate from Chelidonura . This is considered to be a highly variable species in external presentation, as evidenced in the images above.

Above: Two variations of Mariaglaja inornata (also previously Chelidonura ). Presents with a broad white band anteriorly on the head combined with yellow/orange laterally. White spots, sometimes limited to parapodia, but when combined with orange spots covers headshield, posterior-shield and caudal lobes as well. A white edge around the rear margin of the headshield is present.

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DIVE LOG Australasia #409 - December ‘24

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