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Ontogenetic development of electric‐organ discharges in a mormyrid fish, the bulldog Marcusenius macrolepidotus (South African form)
Author(s) -
Werneyer M.,
Kramer B.
Publication year - 2006
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.2006.01195.x
Subject(s) - biology , ontogeny , juvenile , larva , electric fish , zoology , electric organ , metamorphosis , anatomy , fish <actinopterygii> , ecology , fishery , endocrinology , genetics , torpedo , acetylcholine receptor , receptor
The emergence and development of the electric‐organ discharge (EOD) in larvae and juvenile bulldog Marcusenius macrolepidotus was investigated. Larvae hatched 4–5 days after spawning, and the first EODs were recorded on days 9 and 10 at a standard length ( L S ) of c. 6·5 mm. The larval EOD waveform was virtually monopolar, with a strong head‐positive phase followed by a weak head‐negative phase of long duration. A small separate potential preceded the EOD by c. 1·6 ms (believed to represent postsynaptic potential from electrocyte stalks). In contrast to previous reports on Pollimyrus adspersus with its distinct larval and adult EODs, in M. macrolepidotus there was a gradual transformation of the larval into the adult EOD waveform. The transformation started at an L S of c. 17 mm (at an age of c. 40 days), first indications being a decrease in duration of the head‐negative phase, and an increase of its peak amplitude relative to that of the head‐positive phase. Still later, the weak postpotential of the adult EOD emerged on the rising edge of the head‐negative phase. The transformation was nearly completed at an L S of c. 30 mm (at an age of c. 60 days). Evolutionary and behavioural consequences of this alternative path of EOD ontogeny are discussed.