Tucuxi
| Tucuxi | |
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| Size compared to an average human | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Infraorder: | Cetacea |
| Family: | Delphinidae |
| Genus: | Sotalia |
| Species: | S. fluviatilis |
| Binomial name | |
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Sotalia fluviatilis (Gervais & Deville, 1853) |
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| Range of tucuxi (inland–hatched pattern) and costero (coastal–solid pattern) | |
The tucuxi (Sotalia fluviatilis), alternatively in Peru bufeo gris or bufeo negro, is a species of freshwater dolphin found in the rivers of the Amazon Basin. The word tucuxi is derived from the Tupi language word tuchuchi-ana, and has now been adopted as the species' common name. Despite being found in geographic locations similar to those of 'true' river dolphins such as the boto, the tucuxi is not closely related to them genetically. Instead, it is classed in the oceanic dolphin family (Delphinidae).
Physically, the species resembles the bottlenose dolphin but differs sufficiently to be placed in a separate genus, Sotalia. The costero (Sotalia guianensis), related dolphins present in coastal and estuarine environments and formerly grouped together with the tucuxi, have recently been recognized as a distinct species.
The tucuxi is frequently described (see references below) as looking similar to the bottlenose dolphin, but it is typically smaller at around 1.5 m (4.9 ft). The dolphin is colored light to bluish grey on its back and sides. The ventral region is much lighter, often pinkish. It is theorized that this pinkish color may be caused or intensified by increased blood flow. The dorsal fluke is typically slightly hooked. The beak is well-defined and of moderate length. There are 26 to 36 pairs of teeth in the upper and lower jaws.
The tucuxi Sotalia fluviatilis was described by Gervais and Deville in 1853, and the costero Sotalia guianensis by Pierre-Joseph van Bénéden in 1864. These two species were subsequently synonymized, with the two species being treated as subspecies of marine and freshwater varieties. The first to reassert differences between these two species was a three-dimensional morphometric study of Monteiro-Filho and colleagues. Subsequently, a molecular analysis by Cunha and colleagues unambiguously demonstrated that Sotalia guianensis was genetically differentiated from Sotalia fluviatilis. This finding was reiterated by Caballero and colleagues with a larger number of genes. The existence of two species has been generally accepted by the scientific community.
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