Diving with Porcupinefishes

Lanta Marine Life | Diodontidae

Closely related to pufferfish, porcupinefish are medium to large sized fish with short, wide bodies, and large eyes. The mouth contains teeth which are fused to form a strong, beak-like crushing structure which can give a nasty bite. These curious fish are regularly spotted when diving Koh Lanta.

The rounded dorsal and anal fins are set far back on the body and lack spines. Most species found around Koh Lanta are typically coloured light grey, light tan or brown, usually overlain with dark brown to black spots, bars, and/or blotches; green overtones and yellowish spots may also be present.

Just like pufferfish, porcupinefish have the ability to inflate their bodies by swallowing water or air, making themselves up to twice as big when feeling threatened.

Even when inflated, porcupinefish are able swimmers, however when on the surface, air absorbed into the soft belly causes the fish to float upside down, with water being drawn through the mouth into the gills until it is able to release the air and return to depth.

This increase in size quickly limits the range of potential predators to those with much bigger mouths.

Porcupinefish have an additional defence system provided by hundreds of short, sharp spines, which in most species normally lie flat against the skin. When inflated, these spines radiate outward, presenting a potential predator with a large spiky ball.

Some species of porcupinefish have yet another defence mechanism, again, similar to pufferfish, they can be very poisonous, carrying powerful toxins in their internal organs which they obtain from certain bacteria in their diet.

As a result of these three defences, porcupinefish have few predators, although adults are sometimes preyed upon by sharks.

Incredibly, Charles Darwin reported that porcupinefish have been found floating alive in the belly of sharks, and have even been known to eat their way through the stomach and body of a shark in order to escape.

Porcupine fish are generally slow movers, feeding on hard-shelled benthic invertebrates that are crushed with powerful jaws such as crabs, snails and sea urchins.

3 species found on this page:

Spotted Porcupinefish (Diodon hystrix)
Black-blotched Porcupinefish (Diodon liturosus)
Spotfin Burrfish (Chilomycterus reticulatus)

Spotted Porcupinefish

(Diodon hystrix)

Diodon hystrix @ Koh Haa

The Spotted Porcupinefish has a generally whitish body, perhaps pale grey, and many small black spots on the head, body and fins.

There are no dark, dusky or black blotches on the body. There are many movable spines on the body, however the belly is smooth with no spines.

The Spotted Porcupinefish grows to 71 cm, but more usually observed 30 cm - 50 cm. This is a solitary species and usually seen over sand and rubble areas at the reef edge.

This curious species likes to follow divers, especially around Koh Haa lagoon, and the diet includes sea urchins, snails and crustaceans.

Black-blotched Porcupinefish

(Diodon liturosus)

Diodon liturosus @ Koh Bida

The Black-blotched Porcupinefish has a brownish-grey body with large dark brown to black blotches on the body. The blotches on the back have white margins, and there is always a black blotch through the eye and under the chin. There are numerous movable spines.

The Black-blotched Porcupinefish grows to 50 cm, but more usually observed 25 cm - 35 cm.

This is a shy species, normally found hiding is coral or rocky crevices or under ledges. May show some curiosity to the patient and still diver.

Spotfin Burrfish

(Chilomycterus reticulatus)

Chilomycterus reticulatus @ Hin Bida

The Spotfin Burrfish body colour varies from greyish to brownish. The body and fins are covered in many small black spots and there are 3 dusky body bars and a dusky bar under the eye.

The top of the head is also often dusky. There are many fixed triangular spines.

The Spotfin Burrfish usually grows to roughly 50 cm, however, occasionally we can see larger individuals at some of the dive sites around Koh Lanta.

This is a solitary species which feeds on hard-shelled invertebrates such as snails, crabs, shrimp, etc.