Ossubtus xinguense

Ossubtus xinguense
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Characiformes
Family:	Characidae
Subfamily:	Serrasalminae
Genus:	Ossubtus Jégu, 1992
Species:	O. xinguense
Binomial name
Ossubtus xinguense Jégu, 1992

Ossubtus xinguense is a species of serrasalmine characin and is the only species of the genus Ossubtus. It has an unusual downturned mouth that gives the appearance of a beak.

Distribution

It originates from the Xingu River basin, but is restricted to the rapids area around Altamira City, Pará, Brazil.^[1]

Description

This species reaches 17.6 centimetres (6.9in) SL.

The body is ovoid. The profile of the snout is blunt. In young fish, the mouth is terminal (pointing forward); however, as the fish grows, the mouth turns downward and becomes strictly ventral in individuals larger than 5 cm (2 in) SL.^[1] This gives the mouth a beak-like appearance.^[1]

Ecology

O. xinguense is a strictly rheophilic species. Young specimens of up to 4 cm (1.6 in) SL could be observed in schools of 20–30 individuals, sheltered under broad stones.^[1] This species is omnivorous. Shrimp, dead or alive, blood worm, vegetable matter, brine shrimp, daphnia etc, are foods this species will consume in captivity. In captivity, it exhibits high territoriality which results in a strong aggressiveness towards conspecifics. This species is parasitized by Anphiira xinguensis, an isopode of the family Cymothoidae. This parasite lives in the gill chamber of the fish and also develops a contorted morphology, presumably in response to its host's cursive ontogeny.^[2] The female is far more dominant than the male and will often seek caves to which no other fish may enter. This is believed to be due to reproductive dominance (protecting the young), once a suitable breeding location is found the female will not surrender it.

Conservation

This fish is endangered.^[1] However, it is not listed on the IUCN Red List.^[3]

O. xinguense is endemic to the rapids of Xingu River around Altamira City. The planned construction of a large hydroelectric plant in the lower Xingu River at the limit of the rapids and the main Amazon floodplain may result in a highly negative impact to the population of O. xinguense and numerous other rheophilic (and apparently endemic) fish species occurring in the Xingu River rapids.^[1]

References

1. ^ ^{a b c d e f} Jégu, Michel, Michel Jégu; Zuanon, Jansen (2005). "Threatened fishes of the world: Ossubtus xinguense (Jégu 1992) (Characidae: Serrasalminae)". Environmental Biology of Fishes 73 (4): 414. doi:10.1007/s10641-004-4230-5. 
2. ^ Thatcher, E. (1995) Anphiira xinguensis sp. nov. (Isopoda, Cymothoiclae) a gill chamber parasite of an Amazonian serrasalmid fish, Ossubtus xinguense Jegu, 1992. Amazoniana XIII(314): 293-304.
3. ^ Froese, Rainer, and Daniel Pauly, eds. (2007). "Ossubtus xinguense" in FishBase. July 2007 version.

Calum and Jock Chalmers - Keepers and Researchers