The Black-blotched Porcupinefish (Diodon liturosus) is one of many fascinating species within the Porcupinefish family and is closely related to, but distinct from, Pufferfish. Porcupinefish belong to the family Diodontidae, while Pufferfish are part of the family Tetraodontidae. The main difference is that Porcupinefish have specialized scales that turn into spines when they puff up in defense, whereas Pufferfish do not have these spines.
Distinguishing Features
Black-blotched Porcupinefish, also known as Short-spine Porcupinefish, feature a light brown background with dark brown or black blotches outlined in white. Their prominent eyes, typical of nocturnal feeders, are covered in blotches. The anal and dorsal fins are positioned close to the tail and are usually light yellow, though some may have darker yellow fins. When not inflated, their spines lie flat against their body, pointing backward.
They can grow up to 65 cm in length, but seeing one this large is rare; they are usually found around 35 cm. Their mouth is relatively large, and if you look closely, you’ll notice that the skin around it is wrinkled.
Behavior and Movement Patterns
Black-blotched Porcupinefish are usually seen alone but can be found in pairs or groups during mating. By day, they often hide in small reef crevices and may inflate to fit tightly. Sometimes, they rest on the bottom in the open, and they usually ignore divers, moving away only if approached too closely. They swim slowly using their pectoral, dorsal, and anal fins but can make quick bursts of speed with their tail fin. Despite their bulky look, Porcupinefish are quite agile and can turn quickly.
Defensive Behavior
Like all pufferfish, Black-blotched Porcupinefish can inflate themselves by swallowing large amounts of water or air. This makes them bigger and harder for predators to eat, and their spines stick out, making them look less tasty. They also have a special relationship with certain bacteria, such as Pseudoalteromonas tetraodonis, which produces a powerful toxin called tetrodotoxin. This toxin helps protect them from being eaten by predators.
Feeding and diet
Black-blotched Porcupinefish are nocturnal feeders. Their diet mainly includes hard-shelled prey such as crustaceans (crabs and shrimp), gastropods (snails), and sea urchins. They use their strong jaws and beak-like teeth to crack open these tough shells with ease.
Reproduction
Black-blotched Porcupinefish are prolific spawners. During spawning, males push females to the surface where they release and fertilize a large number of eggs. These eggs float on the surface for several days before hatching into well-developed larvae. Over the next three weeks, the larvae grow fins and teeth and, once they reach about 6 to 7 cm, they migrate to inshore areas in search of shelter and better food sources.
Fun Facts:
- Despite their charming appearance and unique features, Black-blotched Porcupinefish aren’t the best swimmers. They have small fins and bulky bodies, making them slow and somewhat awkward in the water.
- An interesting tidbit from Charles Darwin: Dr. Allen of Forres often found porcupinefish still alive and inflated inside sharks’ stomachs. Some even managed to chew their way out, showing their impressive toughness!
- When inflated, porcupinefish can still swim, but the air trapped in their belly makes them float upside down at the surface. They draw in water through their mouth to help release the air and sink back to deeper water.
- The Black-blotched Porcupinefish is the only fish you’ll encounter on a dive around Koh Tao that seems to smile at you! They also have a unique ability to move each eye independently, allowing them to keep a constant lookout while swimming.
- Diodon comes from Greek, meaning "two-toothed," referring to the fused, beak-like teeth of these fish.
Where to Find the Black-blotched Porcupinefish on Koh Tao
You can spot the Black-blotched Porcupinefish while scuba diving at various dive sites around Koh Tao. Though they can be a bit shy, you’ll often find them hiding under ledges and between rocks at different spots :
