Lactoria diaphana (Bloch & Schneider, 1801)

Body and Carapace Structure

Lactoria diaphana, commonly called the roundbelly cowfish, has a thick, rectangular body that is mostly enclosed in a carapace formed by thickened, hexagonal, plate-like scales connected to one another. There are five horizontal ridges on the carapace: one poorly developed ridge along the back, and a pair of upper and lower ridges on each flank.

Spine Placement

A large spine grows above each eye, a spine sits at the rear end of each lower flank ridge, and a spine is located halfway along the back ridge.

Mouth and Tooth Features

It has small mouths positioned at the front of the snout, with fleshy lips and a row of no more than 15 moderately sized conical teeth in each jaw.

Gill Slit Characteristics

The gill slits are short and oblique, and sit in front of the pectoral fin bases.

Fin and Caudal Peduncle Structure

The dorsal and anal fins are located at the back of the carapace, the caudal peduncle is thin and flexible, and the caudal fin is fan-shaped. Both the dorsal fin and anal fin have 9 soft rays.

Body Profile Shape

The dorsal profile of the snout is steep and concave, while the ventral profile of the body is rounded.

Coloration and Pattern

The overall body is pale greenish-grey, patterned with honeycomb reticulation and brown blotches.

Maximum Size

This species reaches a maximum total length of 34 centimetres (13 inches).

Overall Distribution Range

Lactoria diaphana has a wide distribution across the Indo-Pacific region. Its range stretches from the eastern coast of Africa off Mozambique and South Africa in the western Indian Ocean, through the Indian and Pacific Oceans, all the way to the eastern Pacific between Santa Barbara, California and Chile.

Latitudinal Range Limits

It can be found as far north as Japan and as far south as Tasmania.

Atlantic Distribution

It is the only member of the genus Lactoria with a range that extends into the southeastern Atlantic, occurring around the Cape of Good Hope and along the southwestern coast of Africa as far north as Swakopmund, Namibia.

Adult Habitat and Depth

The roundbelly cowfish inhabits coastal and outer reefs, at depths down to 50 m (160 ft).

Juvenile Habitat Traits

Juveniles are semi-transparent and live in pelagic waters near the surface.

Toxin Release Mechanism

Like other boxfishes, this species (also referred to as the thornback cowfish) can release a soap-like toxin called pahutoxin through its skin when stressed.

Toxin Effects on Predators

This toxin can incapacitate or even kill potential predators.

Human Poisoning Record

One recorded case in Japan involved a human death from palytoxin poisoning after ingesting the flesh of this species.