OP
A kind user over on wetpixel has identified it as an Isopod, Gnathiidae juvenile male
The Gnathiidae are a family of isopod crustaceans. They occur in a wide range of depths, from the littoral zone to the deep sea. The adults are associated with sponges and may not feed. The juvenile form is known as a 'praniza' larva, and it is a temporary parasite of marine fish.
Gnathiidae - Alchetron, The Free Social Encyclopedia
The Gnathiidae are a family of isopod crustaceans. They occur in a wide range of depths, from the littoral zone to the deep sea. The adults are associated with sponges and may not feed. The juvenile form is known as a 'praniza' larva, and it is a temporary parasite of marine fish.
Gnathiidae - Alchetron, The Free Social Encyclopedia
