Study reveals secondary sexual characters in Bryconamericus

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A new study on a member of the characin genus Bryconamericus has revealed some interesting facts about the reproduction and secondary sexual characteristics of the fish.

Vinicius Renner Lampert, Marco Aurlio Azevedo and Clarice Bernhardt Fialho studied Bryconamericus iheringii, a member of the family Characidae from the Rio Vacaca in Brazil every month over a period of an entire year in an attempt to monitor how the fish changed over the course of the year.

The study, which sampled several hundred fish, showed that, like other characids from the Rio Vacacai, B. iheringii had a marked breeding season between September and January. In the Southern Hemisphere, this is the spring and early summer.

Counting the number of eggs in the ovaries of the females sampled also showed that the species spawns several times each season - not just once as in some other species from the region.

The field survey has also confirmed that males of Bryconamericus iheringii develop hooks on their fins - a feature known in biology as a secondary sexual characteristic.

The study showed that the hooks were bigger in the largest fish, and grew to their maximum size at the height of the breeding season.

For more information on the reproductive of this characin see the paper: Vinicius Renner Lampert, Marco Aurlio Azevedo and Clarice Bernhardt Fialho (2004) - Reproductive biology of Bryconamericus iheringii (Ostariophysi: Characidae) from rio Vacaca, RS, Brazil. Neotropical Ichthyology, 2(4): 209-215, 2004.