A harmless copy of a venomous fangblenny, often nesting inside a discarded bottle.
A slim blenny to about 11 cm, pale yellowish white with two or three clean dark brown-black stripes running from the snout to the tail and a blunt, rounded head. It is a close copy of the striped fangblenny Meiacanthus grammistes, whose bite carries venom and which predators leave alone; the resemblance is good enough that the two are regularly logged as one animal. The reliable separator is the tail: Meiacanthus grammistes has a forked caudal fin and its stripes break up into rows of spots and dashes over the rear third of the body, while Petroscirtes breviceps has a rounded to squared-off tail and stripes that stay continuous to the base of it. The mimic has enlarged canines but no venom gland, so the resemblance is the whole of its defence.
Lives on shallow sand, seagrass and rubble, and characteristically among discarded objects — bottles, cans, lengths of pipe, sections of tyre. Males nest inside them, guarding a clutch of eggs stuck to the inner surface of a bottle or an empty shell, and a bottle lying on a shallow muck slope is as likely to hold this fish as anything else. Feeds on small invertebrates, algae and organic material. Recorded from a metre down to about 15 m. Its habit of using litter for shelter makes it one of the animals that a muck site produces reliably and an adjacent reef does not, and a bottle occupied by a nesting male is worth leaving where it lies rather than turning over.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.