Care
The Blue Velvet Sea Slug is a small marine opisthobranch from the order Cephalaspidea, the Headshield Slugs. It is widespread throughout the Indo-West-Pacific region, where it may be observed feeding on flatworms in shallow water lagoons and reefs with sandy or muddy substrates. Blue Velvet Sea Slugs are often sold to help control turbellarian flatworms, but they will require an ongoing source of these if they are to thrive. This creates a somewhat tricky situation, as the sea slugs will perish without these flatworms to feed on, but most aquarists do not wish to sustain large numbers of them, lest they become detrimental to their prized sessile invertebrates. Turbellarian flatworms reproduce rather readily, so it is best to culture them in a fishless refugium, so that some can be introduced back into the main aquarium when numbers start to become depleted, otherwise the Blue Velvet Sea Slugs will simply starve; alternatively the sea slugs could be moved into the refugium for a time, whilst the turbellarian population is allowed to build back up in the main aquarium again, at which point the sea slugs could be moved back. These opisthobranchs are black in colour, with vibrant electric blue lines along the margins of the parapods and the distinctive hammer-shaped head. The two long "tails" (the left always being longer than the right) at the posterior are characteristic of the
Chelidonura genus. Sensory cilia on the anterior edge of the head are used to find flatworms, and these are then taken up by a tube-like proboscis. There is an internal shell, and although they may look superficially like the true nudibranchs, these sea slugs are distinguished by the head-shield and parapods that fold over the top of the body.
Chelidonura varians is sometimes mistaken for the similarly coloured
Philinopsis gardineri, also known from the Indo-West-Pacific region; however, they can be told apart fairly easily as
P. gardineri does not possess the long tails of
C. varians. These non-aggressive creatures are very sensitive to changes in water chemistry, so they must be acclimatised very carefully, preferably by using the drip acclimatisation method over a course of a couple of hours. Ensure that all pump intakes etc are screened off in order to prevent the Blue Velvet Sea Slugs from being drawn in. Do not use copper based treatments with this species present, and keep nitrates as low as possible. Not suitable for beginners. May also be seen on sale as the Headshield Sea Slug or Blue Velvet 'Nudibranch'.
Feeding
Obligate feeder of flatworms and requires an ongoing source of these; particularly enjoys the Red Acoelomorph Flatworm
Convolutriloba retrogemma.
Breeding
These sea slugs reproduce sexually. Spawning has been reported in the home aquarium when groups have been maintained together; however, there has been little success in raising the resultant larvae. Sometimes, these sea slugs will lay egg masses when stressed or dying, but to be viable, there needs to be more than one individual present for successful mating (and mating can occur some time before egg laying, as it is thought the sperm can be stored in a special pouch).
