Orthosternarchus Tamandua - Biology and Ecology

Biology and Ecology

As in other apteronotids, O. tamandua generates a continuous weak electric field for electrolocation and communication. At 452-605 Hz, the electric organ discharge (EOD) of O. tamandua has a much lower frequency than most other apteronotids and approaches the frequencies of the sternopygid knifefishes. The EOD is also unusual in that the waveform is monophasic, with a head-negative spike followed by a positive baseline (the EOD of most apteronotids have both positive and negative spikes). The only other apteronotid known to have a monophasic EOD is the related Sternarchorhamphus muelleri. The monophasic waveform of these two genera is similar to the EOD of a larval Apteronotus, suggesting that it may be a paedomorphic or evolutionarily ancestral trait.