Divided Flatworm

Overview

The Divided Flatworm (Pseudoceros dimidiatus), also known as the Tiger Flatworm, is a striking marine polyclad flatworm found in tropical waters. It is widely recognized for its vivid, aposematic coloration, which serves as a warning to potential predators that the animal may be inedible.

Appearance

This species features an elongated, oval body with a velvety dorsal surface. While highly variable in pattern, it typically displays a black background with a distinct orange marginal band. Common color variations include two broad, longitudinal yellow-green stripes separated by a central black line, though some individuals may exhibit transverse stripes or blotches. The ventral side is generally grey-black, and the anterior margin features short, simple pseudotentacles formed by folds of the body edge.

Distribution & Habitat

The Divided Flatworm is widespread throughout the tropical Indo-Pacific region, ranging from the Red Sea and the Indian Ocean to the Western Pacific, including the Great Barrier Reef and Hawaii. It is primarily a reef-dwelling species, frequently observed in coral reef environments.

Feeding

This flatworm is a specialized carnivore that feeds exclusively on colonial ascidians, commonly known as sea squirts. It consumes these sessile invertebrates by everting its complex, folded pharynx to digest their soft tissues.

Biology & Behavior

As a simultaneous hermaphrodite, this species is capable of both sexual reproduction and asexual reproduction through transverse fission. It is typically a solitary animal and is often seen active during the day on reef slopes. Its bright, contrasting colors are believed to be aposematic, helping the flatworm deter predators in its competitive reef ecosystem.