Yellow-eyed piranhas produce louder sounds than red-eyed piranhas in an invasive population of Serrasalmus marginatus

Serrasalmus marginatus is a piranha species native from the lower Paraná River basin and
has been invasive in the upper Paraná River basin since the 1980s. In piranhas, sounds
of different species have different features. The aim of this study was to investigate if
the sounds produced by this species could be used to distinguish two morphotypes:
red- and yellow-eyed S. marginatus from the Araguari River (upper Paraná River basin).
All the temporal and frequency features of the sounds were equivalent in both groups
of eye colour; it corresponds to the species-specific signature described for
S. marginatus. Nonetheless, the amplitude features were all statistically different
between red- and yellow-eyed piranhas. Yellow-eyed specimens produced louder
sounds. In different fish species, colour change in eyes can be due to the absence or the
presence of a dominant allele. It can also be involved in social rank or during reproduction. Different hormones and neuropeptides can modulate vocal features. It is hypothesized that a mutation or different hormonal concentrations could explain both sound
amplitude and eye colour playing a role in animal communication in S. marginatus