In this minute of relaxation, we’d like to focus your attention on a curious-looking sea creature digging in the sand, named the “Moon-headed sidegill slug” (Euselenops luniceps).
We hope you’ll enjoy your minute with this weird and wonderful creature …
Watch the dark side of the moon: Euselenops luniceps
Euselenops luniceps is a species of sea slug, a pleurobranchomorph gastropod mollusc in the family Pleurobranchaeidae. This family of sea slugs is known as „side-gilled slugs“ since they have their gills hidden on the right side of the body under the mantle (the body edge).
Moon-headed sidegill slug is a sand crawler
This slug is perfectly adapted for living in a sandy environment. In most pleurobranchs, the foot and mantle are of similar size but in Euselenops the foot is much larger, which makes it easier to crawl over sand, or burrowing underneath it. Posterior, the mantle folds into a relatively long siphon or tube, which allows the mantle cavity and gills to remain in contact with fresh seawater while the animal is buried in the sand. With the incoming seawater, the animal can also sense chemical released by potential prey nearby.
Euselenops luniceps is sensing its prey
It has a large oral veil fringed with lots of sensory ‚hairs‘ on the underside to detect prey. This unique looking creature roams along sandy and silty sea bottoms for food with a very pronounced large oral veil, which underneath is fringed with tiny sensory „hairs“ (papillae), to help it detect prey. Although it is a predator, little is known about what it eats. It appears they have a particular fondness for anemones, however, they have also been observed on sand flats at low tide, where they hunt and swallow whole any invertebrates that they touch with their large oral veil.
Fast, but not furious: Moon-headed sidegill slug
While most sea slugs move quite slowly, Euselenops with their active food gathering approach can move surprisingly fast. Not only does it have speed, but this slug can also actually swim for some distance by flapping the sides of its body, much in the same way as its more famous cousin, the “Spanish Dancer” (Hexabranchus sanguineus) does.
Despite the fact that many websites claim the maximum size of this creature is approximately 7cm, this particular specimen filmed in Amed (Bali), was closer to 20cm.