New Paedocypris is one of world's smallest fish

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A new species belonging to the miniature fish genus Paedocypris has been described from Western Borneo.

The new Paedocypris species, the third placed in the genus since 2006, was described by ichthyologists Ralf Britz of the Natural History Museum (London) and Maurice Kottelat of the Raffles Museum of Biodiversity Research (Singapore) in the most recent volume of the Raffles Bulletin of Zoology.

Paedocypris carbunculus

The new species has been named carbunculus, after the latin name for the gemstone ruby, in reference to the ruby colour exhibited by the tiny individuals of this species in life (the largest specimen examined, a female, was only a little over 1 centimeter in length).

Paedocypris carbunculus is distinguished from the two other species of the genus known to date (Paedocypris progenetica, currently the world s smallest fish species, and P. micromegethes) based on differences in head blotch pigmentation on the dorsal surface of the head and by a combination of body pigmentation features.

Like Paedocypris progenetica and P. micromegethes, the new species is an inhabitant of the small blackwater streams flowing through the highly endangered peat swamp forests of South East Asia.

The new species was first collected from a small peat swamp forest stream on the outskirts of Pangkalan Bun, Western Borneo, in 2005.

At this particular location, known as the type locality, Paedocypris carbunculus was reported to form shoals of 100-200 individuals in areas with slow current, near to the surface and usually close to overhanging or submerged vegetation.

Paedocypris spawning behaviour

In addition to its description, Britz and Kottelat also provide a brief account of the captive spawning of Paedocypris carbunculus reported by O. Perrin and P. Beyer in the German aquarist magazine DATZ earlier this year.

In their DATZ article, Perrin and Beyer reported that Paedocypris carbunculus spawned upside down, laying a very small number of eggs on the underside of plant leaves.

They also reported that prior to spawning reproductively active males displayed a prominent head blotch.

This head blotch was most prominently displayed by males when they are upside down under a leaf.

Britz and Kottelat hypothesize that this dorsal head blotch pigment, which is an important taxonomic character for distinguishing between species of Paedocypris, may play a significant role during courtship by representing a signal to ripe females that the male is ready to mate.

For more information on the new species of Paedocypris and its spawning habits, see the paper: Britz, R. and Kottelat, M. (2008). Paedocypis carbunculus, a new species of miniature fish from Borneo (Teleostei: Cypriniformes: Cyprinidae). Raffles Bulletin of Zoology, 56(2): 415-422.