Abstract
The aim of this study was a longitudinal description of the ontogeny of the adult electric organ of Campylomormyrus rhynchophorus which produces as adult an electric organ discharge of very long duration (ca. 25 ms). We could indeed show (for the first time in a mormyrid fish) that the electric organ discharge which is first produced early during ontogeny in 33-mm-long juveniles is much shorter in duration and has a different shape than the electric organ discharge in 15-cm-long adults. The change from this juvenile electric organ discharges into the adult electric organ discharge takes at least a year. The increase in electric organ discharge duration could be causally linked to the development of surface evaginations, papillae, at the rostral face of the electrocyte which are recognizable for the first time in 65-mm-long juveniles and are most prominent at the periphery of the electrocyte.
Highlights
The speciose weakly electric gymnotiform and mormyrid fishes (Froese and Pauly 2008) possess an active sensory system comprising electric organs (EOs) and electroreceptors (e.g., Moller 1995)
At around 48 mm length, the duration of Juveniles of various sizes showing the change in pigmentation, the allometric growth of the snout and the increase in body height during development. l Adult female. a1 Shows the larval electric organ discharges (EODs), b1 the transitional stage with both, the larval and the adult EO active. c1 EOD of the adult EO alone; we termed this EOD the juvenile EOD, because it is produced by a juvenile fish
The aim of this study was a longitudinal description of the ontogeny of the adult electric organ of C. rhynchophorus which produces as adult an EOD of very long duration
Summary
The speciose weakly electric gymnotiform and mormyrid fishes (Froese and Pauly 2008) possess an active sensory system comprising electric organs (EOs) and electroreceptors (e.g., Moller 1995). Investigations on the ontogeny of the EOs suffered from a lack of embryological material and juveniles (Keynes 1961; Szabo 1960, 1966) The reproduction of these weakly electric fishes is based on the imitation of rainy season conditions (Kirschbaum 1975) and opened the way for detailed ontogenetic descriptions (Kirschbaum and Schwassmann 2008; Kirschbaum 1977, 1981). This led to the discovery of larval electric organs (Kirschbaum 1977)
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