Megaleporinus obtusidens

Megaleporinus obtusidens is a South American species of headstander that inhabits the basins of the Paraná River and the Río de la Plata, the Uruguay River, and the São Francisco River (including minor rivers and tributaries like the Bermejo, Pilcomayo, Salí, Juramento, Dulce, and Uniguay). It may be found in the main courses and streams, as well as in lakes and lagoons; it often shelters among stones and aquatic vegetation.

In Argentina and Uruguay its common name is boga (sometimes augmentative bogón); in Brazil it is known as piapara. There is also a variant called piava and another called tres puntos ("three dots"). This species is also known by the technical synonym Curimatus obtusidens. The common name boga is applied to many other species of fish, usually unrelated to this one.

Megaleporinus obtusidens has an elongated wide body, with a comparatively small head and a blunt mouth; its teeth are reminiscent of the incisors of Lagomorpha, whence the name of the genus (leporinus, "hare-like", as in Leporidae). Its basic colour is a light greenish-gray, with three rounded dark spots in mid-flank, which may not be visible in some specimens. In young individuals there are also eight broad vertical streaks, joined in the back and coming down to the middle line. The back, as usual in this habitat, is darker than the belly.

The length and weight of the individuals are extremely variable according to the area, probably influenced by different feeding habits, opportunities and exploitation, as well as local sub-specific variants. In the Río de la Plata L. obtusidens is reported as weighing an average of 2 kg, with a maximum of 4 kg; in the upper course of the Paraná River it is about 4.5 kg; and in the middle course of the Paraná there are specimens of boga over 6 kg (with exceptionally developed ones over 8 kg). Adult individuals are reported between 40 and 80 cm long. The larger fish probably belong to other species of Leporinus (either L. friderici, which is still not very well known, or Megaleporinus macrocephalus, only recently classified as a separate species).

Megaleporinus obtusidens is an omnivore: it eats water plants, crabs and river snails. However, it prefers grain and seeds (wheat and maize), and it often gathers in large banks near ports, where cargo ships drop grains into the water. It is preyed upon by larger fish like the surubí and the dorado. It prefers warm waters and reproduces in spring and summer, starting at 2 years of age.