Paedocypris progenetica is the known smallest fish in the world. Paedocypris is a fish genus in the family Cyprinidae (which also includes carps and minnows) which is recorded form Indonesia. Before discovering the smallest frog as well as vertebrate named Paedophryne amauensis from Papua New Guinea in August 2009, this fish was also a smallest vertebrate in the world. The length of smallest mature female was measured 7.9 mm (0.31 inch) and longest known individual 10.3 mm (0.41 inch).
Species: P. progenetica
Paedocypris was discovered and identified by ichthyologist Maurice Kottelat from Switzerland and Tan Heok Hul from the Raffles Museum of Biodiversity Research and the National University of Singapore in 1996. The Paedocypris progenetica was found in the slow-flowing black-water streams and peat swamps. The genus Paedocypris was first discovered in 2006. “Poideios” is Greek for children and “Cypris” is Greek for ‘Venus’ and is a common suffix for Cyprinid genera; the gender is feminine progenetica (from the word Progenetic) is used as an adjective.
Paedocypris is considered a danionin genus by “Tyson Roberts”; it was found that Sundadanio and Paedocypris share a sister group relationship supporting its close relationship to danionin genera.
Their miniature transparent body backs typical features characteristics of adult fish instances a bony skull structure around its brains and it retains the post and larval fin fold along the ventral edge of the caudal peduncle, characteristic of fish larvae. They have a unique sexual dimorphism. The males have highly modified pelvic fins with the first day terminating with a hook-like projection of keratinized skin, supported by hypertrophied pelvic musculature. Male also have a pad of keratinized skin in front of the pelvic fins. It is hypothesized that these modified fins are used to grasp the female during mating or to keep position over a spawning surface.
Paedocypris progenetica lives in the dark colored peat swamps of the Indonesian island of Sumatra. Its small size helps to survive through extreme droughts as they can live in small remaining puddles of acid water (pH as low as 2.9 at least 100 times more acidic than rain water). Their habitat is threatened by forest fires, logging and plantations.
- Male individuals of the species angler fish (Photocorynus spiniceps) have been documented to be 6.2-7.3 mm at maturity and thus claimed to be smaller species. However, these survive only be sexual parasitism and the female individuals reach significantly larger size of 50.5 mm.
- The previous record for smallest vertebrate was held by an 8mm species of Indo Pacific goby. The UK’s smallest fish is the marine Guillet’s goby, Lebetus guilleti , reaching 24mm in length.
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