Dwarf pufferfish

Description

The dwarf pufferfish (Carinotetraodon travancoricus), also known as the Malabar pufferfish, pygmy pufferfish, or pea pufferfish, is a small freshwater pufferfish endemic to Kerala and southern Karnataka in Southwest India. Dwarf pufferfish are slow-moving and, unlike other species of pufferfish, found in large groups in the wild. They dwell at the bottom of heavily vegetated waterways, predating small animals. They are popular in aquaria for their bright colours and small size. At a maximum length of 3.5 cm, dwarf pufferfish are one of the smallest pufferfish in the world. They closely resemble the related Carinotetraodon imitator, and the two can be difficult to distinguish. C. imitator was not recognised as a different species until 1999. Habitat loss and overharvesting for the aquarium trade threaten wild populations of dwarf pufferfish. The maximum documented size is 3.5 cm (1.4 in) total length (TL), with individuals typically reaching less than 2.5 cm (0.98 in) TL, making dwarf pufferfish one of the smallest pufferfish in the world. Both sexes are primarily greenish-yellow, with dark green to brown-black iridescent patches on the flanks and dorsal surface. Patterns and colouration vary considerably between individuals. Their pectoral fins are short, fan-shaped, and described as "slightly emarginate", that is to say, slightly indented at the tip. The dorsal and anal fins are situated opposite each other toward the posterior of the fish, both short and round, while the caudal fin is larger than the other fins and truncate, in that it terminates in a more-or-less vertical edge. Their bodies are round and oblong. As with other members of the genus, sexual dimorphism is apparent in mature fish, with males being more brightly coloured than females and having a yellow ventral surface. Males can also have a dark stripe down the centre of their pale belly and iridescent, blue "eye wrinkle" patterns that females do not have. Females are more rounded, tend to be larger than males, and may or may not show more small spots between their larger dark markings. Their abdomens are white, and they may have a yellow patch on their throat. Although closely related to marine pufferfish, they are not found in salt water, and reports to the contrary are based on misidentification. Dwarf pufferfish are one of only 27 known species of Tetraodontidae known to be adapted to freshwater.