Varicose Wart Slug

Overview

The Varicose Wart Slug is a large, striking dorid nudibranch widely distributed across the Indo-Pacific region and the Red Sea. Unlike many other sea slugs, this species is diurnal and frequently observed crawling openly across coral reefs and rocky substrates during the day.

Appearance

This nudibranch features an elongated, oval body characterized by three to six longitudinal ridges on its mantle. These ridges, along with the base of the mantle, are typically a blue-grey color, while the numerous irregular, conical tubercles atop the ridges are tipped with bright yellow. The areas between the ridges are marked by distinct black lines. It possesses bright yellow rhinophores and a characteristic black longitudinal stripe running along the center of its foot sole.

Biology & behavior

This species is well-known for its potent chemical defense system. By consuming specific sponges, it sequesters toxic sesquiterpenes, which it stores in its body to deter predators. When stressed or disturbed, it can secrete a toxic mucus that is highly effective against fish and crustaceans. Due to this chemical protection, it has few natural predators and serves as a classic example of aposematism, where its vibrant coloration warns potential threats of its toxicity.

Feeding

It is a specialized carnivore that feeds exclusively on specific types of sponges. During feeding, it extends its pharyngeal bulb onto the sponge to consume it, which can cause visible damage to the prey.

Reproduction

As a simultaneous hermaphrodite, the species reproduces by exchanging eggs and sperm with a partner. It typically lays its eggs in a flat, cream-colored ribbon on solid substrates. The resulting larvae are planktonic before eventually settling and developing into adults.