Red-lined Jorunna

Overview

The Red-lined Jorunna (Jorunna rubescens) is a large, distinctive dorid nudibranch known for its elongated, elevated body and velvety texture. Often compared to a log-shaped cake, this species is frequently identified by its unique, erect gill structure housed within a prominent, high branchial pocket.

Distribution & habitat

This species is widely distributed across the Indo-West Pacific, ranging from the East African coast to Papua New Guinea. It is commonly found in shallow reef environments, including lagoons, reef flats, and areas with mixed coral, sand, and rubble, as well as seagrass beds.

Appearance

Reaching lengths of up to 35 cm, the body is typically a pale beige, pinkish, or orange-white, patterned with an irregular network of fine, brownish-red longitudinal streaks. The entire mantle is covered in dense, tiny sensory papillae known as caryophyllidia, which give it a soft, velvety appearance. Its rhinophores are lamellated and dark brown, often tipped with white, and emerge from tall, cup-like sheaths.

Biology & behavior

Jorunna rubescens is a sponge predator that uses specialized chemoreceptors on its rhinophores to locate food and mates. During reproduction, individuals are often observed in pairs, and they are well-known for producing conspicuous, convoluted pink egg ribbons that are frequently spotted on the reef.

Feeding

This nudibranch feeds exclusively on sponges. It consumes its prey by inserting a feeding tube into the sponge tissue and secreting digestive fluids, which partially liquefy the sponge before the resulting mixture is ingested.