Moseley's Flatworm

Overview

Moseley's flatworm (Prostheceraeus moseleyi) is a striking marine flatworm known for its elegant, undulating swimming movements. It is primarily found in the eastern Atlantic Ocean and the Mediterranean Sea, where it inhabits rocky environments rich in algae and ascidians.

Appearance

This species features a flattened, leaf-shaped body that can reach up to 4 cm in length. Its coloration is highly variable, ranging from creamy white to brownish, bluish, or violet, often decorated with small blue-to-violet spots and white marbling. A distinctive thin yellow line traces the entire circumference of its wavy body margin. At the front, two prominent, purple-tinted tentacles serve as sensory organs.

Distribution & habitat

Prostheceraeus moseleyi is commonly encountered on rocky substrates, particularly in areas with abundant coralline algae and tunicates. It is typically found in relatively shallow waters, ranging from the surface down to approximately 30 meters deep.

Feeding

This flatworm is a specialized predator that feeds primarily on ascidians, such as the colonial tunicate Clavelina lepadiformis. Its presence is often a good indicator to look closely at local tunicate colonies.

Biology & behavior

Prostheceraeus moseleyi is a simultaneous hermaphrodite that reproduces via cross-fertilization. Like many other flatworms, it possesses a remarkable capacity for self-regeneration. When moving through the water column, it displays a graceful, rhythmic, and undulatory swimming style.