The development of lateral-line receptors in Eigenmannia (Teleostei, Gymnotiformes) . I. The mechanoreceptive lateral-line system

Vischer, H.A.

Brain Behavior and Evolution 33(4): 205-222


ISSN/ISBN: 0006-8977
PMID: 2758311
Accession: 021906861

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The South American weakly electric fish of the genus Eigenmannia were induced to spawn by simulating the conditions of the rainy season. Whole animals were viewed using scanning electron microscopy, and skin from embryos and larvae of different ages was prepared for histological examination. Additional live fish were stained with vital dyes. Neuromasts develop within the epidermis and then rise to the surface, at which time a cupula is forming. The first neuromasts appear on the head, forming the temporal, mechanoreceptive lateral line, at 3.5 days after spawning, and 1 day later neuromasts appear on the trunk as a ventral trunk line. On day 8 all the cephalic neuromasts have appeared and a secondary, medial trunk line begins to form. A dorsal trunk line forms when the fish are juvenile. Eight neuromasts of the cephalic lines, 7 neuromasts of the medial trunk line and all neuromasts of the ventral and dorsal trunk lines remain at the surface and do not become enclosed in canals. The opercular neuromasts and 7 neuromasts of the ventral trunk line degenerate later. The formation of the head canals begins on day 17, whereas the canal of the medial trunk line starts to develop on day 25, and both head and trunk canal systems are completed by day 33. The mechanosensory system develops before the electrosensory system. Behavioral observations also indicate that the mechanoreceptive system is functional as early as day 5.