Berthella sp. 1 is a fascinating and delicate marine sea slug endemic to the 🌊 Red Sea. While often mistaken for a nudibranch by divers, it actually belongs to the Pleurobranchidae family, commonly known as sidegill slugs. The name comes from their anatomy: instead of exposed gills on their back, they have a single, prominent gill hidden on the right side of their body, tucked neatly beneath their mantle.
A Network of Camouflage
This specific, yet-to-be-officially-named species is easily identifiable by its unique texture. It features a translucent, almost jelly-like body covered in a network of opaque white lines radiating from a central dark spot (which is actually the outline of its internal organs showing through the skin). Growing to a maximum of about 25 mm, it is a tiny and elusive creature.
Life in the Rubble
Like most sidegill slugs, this species is highly light-sensitive and strictly nocturnal. During the day, it hides deep under stones, dead coral formations, and rubble in sandy areas near the reef. It emerges at night to hunt for its highly specialized diet, which consists entirely of encrusting sponges. Because of its size and excellent camouflage, spotting one requires a sharp eye and a good macro lens.
