Rough boxfish

Lore & Background

The rough boxfish was first formally described in 1975 by American ichthyologist John Ernest Randall, with its type locality given as a patch reef about 800 m northeast of Grand Baie on Mauritius. The genus name *Ostracion* means 'little box', referring to the body shape of its type species, while the specific name *trachys* means 'rough', alluding to the feel of the carapace, especially where the scales have a spinule at their centre.

The carapace is oblong with convex dorsal and ventral surfaces and concave sides. The plate-like scales are hexagonal, with most having a spinule, particularly to the rear and on the back. Adult males are blackish on the upper body with small white spots extending to between the eyes, where there is a white band with black margins. Females are dark brown to black with white spots on the back and sides, and juveniles are similarly dark with small circular white spots.

This species is found in the Western Indian Ocean off Mauritius and Réunion. It is secretive, living at depths between 15 and 30 m, hiding in holes and crevices in rocky reefs.

Reader's Guide

The rough boxfish is a relatively small and secretive species, reaching a maximum total length of 11 cm. Its rough carapace, formed by hexagonal plate-like scales with spinules, distinguishes it from other boxfishes. The species was described relatively recently, in 1975, by John Ernest Randall, based on a specimen collected near Mauritius. Its restricted distribution to the Mascarene Islands in the Western Indian Ocean and its preference for hiding in rocky reef crevices at moderate depths make it a less commonly encountered fish. The sexual dimorphism in coloration—males having a white band between the eyes and a white stripe along the upper ridge, while females and juveniles are more uniformly dark with white spots—is a notable characteristic. The species' name directly references the rough texture of its carapace, a key identifying feature. Its secretive nature and limited range contribute to its relatively low profile in marine biology literature.

Did You Know?

• The rough boxfish was first described in 1975 by American ichthyologist John Ernest Randall.
• Its specific name *trachys* means 'rough', referring to the spinules on its carapace scales.
• Adult males have a white band with black margins between the eyes.
• It is found only in the Western Indian Ocean around Mauritius and Réunion.