Malabar pufferfish, Pygmy pufferfish, Pea pufferfish
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. They are popular in aquaria for their bright colours and small size. At a maximum total 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.
Dwarf pufferfish dwell at the bottom of heavily vegetated waterways, predating small animals. Unlike other species of pufferfish, they are found in large groups in the wild. They breed throughout most of the year, with spawning pairs producing 1–5 eggs in 1–4 day intervals. Habitat loss and overharvesting for the aquarium trade threaten wild populations of dwarf pufferfish.
Ov
OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
Mi
MigratingAnimal migration is the relatively long-distance movement of individual animals, usually on a seasonal basis. It is the most common form of migrati...
D
starts withThe 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 have 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 adapted to freshwater. They are a potamodromous species, meaning they migrate within freshwater river systems, and are endemic to rivers, lakes, and estuaries in Kerala and southern Karnataka in the Western Ghats of Peninsular India. They can be found in waters with a pH of 7.5–8.3 and temperatures of 22–28 °C (72–82 °F). Inhabiting heavily vegetated waters with beds of gravel and rock or clay loam with silt and sand, the species is reported from 13 rivers in Kerala, lakes such as Vembanad, the Nilambur harbours, and Kallar Stream, part of the Neyyar Wildlife Sanctuary. They have been reported as rare in Bharathapuzha and the Nilgiri Biosphere Reserve. The species was also found in inundated brickyards in Puthukkad, as well as ditches, ponds, irrigation channels, and artificial tanks or abandoned water bodies in paddy fields. Their presence in small, isolated water bodies is likely due to unintentional dispersal by waterfowl.
Dwarf pufferfish are euryphagous carnivores in that they consume a wide variety of animals. Dwarf pufferfish favour insect larvae but will rely on crustaceans and annelids as alternate feed when the availability of preferable prey decreases. Their diet in the wild mainly consists of small animals such as water fleas, rotifers, copepods, and seed shrimp, and aquatic larvae such as those of Odonata, Hemiptera, mayflies, and flies, with some amounts of plant matter, largely diatoms and green algae. Sand and detritus, presumably ingested by mistake when feeding on small, bottom-dwelling animals, have also been found in their gut.
In captivity, dwarf pufferfish benefit from a varied diet and will eat small freshwater snails, shrimps, as well as foods like frozen mussel meat or other frozen shellfish. They will also readily eat live foods such as red and white mosquito larvae and other small animals they would predate in the wild. Dwarf pufferfish are commonly associated with plants in the genus Cabomba, and the presence of these plants has been shown to reduce mortality among captive specimens.
Dwarf pufferfish are a slow-swimming, demersal, or bottom-dwelling, species. Unlike many pufferfish species, which are primarily solitary and potentially aggressive or territorial between conspecifics (members of the same species), dwarf pufferfish are found in large shoals, occasionally consisting of hundreds of individuals. They are found mainly during the summer months (January to May) and rarely during the rainy season. Shoaling fish experience stress or weight loss when kept in solitude or in groups too small.
In the wild, males with ripe gonads have been found during all months of the year but December and January, with the peak spawning period extending from May to August, concurring with the South-West monsoon period. Within the Pamba River, the minimum size at which half the population becomes sexually mature is approximately 1.83 cm (0.72 in). Environmental and dietary conditions may influence the maturation rate of individuals.
The mid-dorsal and mid-ventral skin ridges of males become brown in colour during the spawning season. The belly of the female will swell, and the courting male will frequently chase the female and nibble at its belly. The female will then search for a suitable location to spawn while the male chases away other males. In the aquarium, dwarf pufferfish are often plant-spawners, laying eggs in plants, including java moss, or on the substrate hidden within plants. A female will scatter approximately 1–5 eggs, 1.43 mm (0.056 in) in mean diameter. The eggs are adhesive and appear transparent and round, with a mass of small oil globules. After laying, the eggs are then fertilized externally by the male. Spawning has been observed in the evening, with the female resting on the spawning site and the male slowly approaching. After spawning, both fish will leave the site. The male will then quickly return to guard the eggs. Sneaking ejaculation by other males has also been observed. The pair may spawn multiple times in 1–4 day intervals.
Eggs hatch after five days at 27 °C (81 °F), with larvae and fry in captivity initially fed infusoria, Brachionus (a genus of rotifers), frozen bloodworms, and brine shrimp when they are a week old. There is little information on what the larvae eat in the wild. Hatched larvae are a mean of 3.15 mm (0.124 in) total length, with eyes incompletely developed and the body a red-brown. The yolk sac is consumed in four days, and the larvae commence swimming after six days, at which point their eyes are completely developed.
There is no information available on the lifespans of these fish in the wild, but aquarists report specimens live for approximately five years in captivity.
Several researchers have considered the species endangered, though with no rationale provided. The dwarf pufferfish is officially classified as vulnerable on the IUCN Red List due to declining populations because of damming, indiscriminate deforestation for agriculture, pollution from wastewater, and, primarily, overfishing for the aquarium trade. In 2010, some researchers estimated that the population would decline by 30–40% from 2005 to 2015, while others estimated it had already declined by the same amount between 2005 and 2010.
