Scientific Name: Hallaxa fuscescens
Common Name: Dusky Hallaxa

Adult Size: 10 – 20 mm
Depth Range: 5 – 20 m
Biotope / Habitat: Coral reef slopes, rocky outcrops, and rubble zones, often near sponges which it feeds upon
Diet: Sponge feeder, using its radula to gently scrape and consume sponge tissue for nourishment and chemical defenses
Reproduction: Hermaphroditic; mates reciprocally, with small, coiled egg ribbons laid in protected reef areas
Fun Fact: Hallaxa fuscescens is perfectly camouflaged with its greyish body and slightly raised tubercles, blending beautifully into the reef’s sponge-dominated environment.

This subtle yet intriguing nudibranch is often overlooked due to its drab coloration, but it’s a fascinating resident of sponge-rich reef environments, contributing to the delicate balance of the reef ecosystem.