The lateral line system and its innervation in Zenarchopterus dunckeri (Beloniformes: Exocoetoidei: Zenarchopteridae): an example of adaptation to surface feeding in fishes

Abstract

Examination of the lateral line system and its innervation in a freshwater halfbeak, Zenarchopterus dunckeri (Beloniformes: Exocoetoidei: Zenarchopteridae), revealed adaptations of a surface insect feeder. Superficial neuromasts (SNs) occurred on the head (ventral surface of lower jaw, snout, cheek, supratemporal region and opercle), trunk (forming four longitudinal rows: middorsal, dorsolateral, lateral and ventrolateral rows) and caudal fin (two rows). The middorsal row was broad, involving three longitudinal scale series (middorsal and left and right adjacent series) anteriorly on the trunk and including 809 SNs (counted on the left side); up to 108 SNs formed a more or less crescentic patch on each scale. The supratemporal ramus of the posterior lateral line nerve (PLLN) extended strongly posterior to innervate the middorsal row. The lateral ramus (of PLLN) gave off an anterior dorsal ramule innervating the dorsolateral row, four short ventral ramules innervating the lateral row, and 15 long ventral ramules innervating SNs of the ventrolateral row and canal neuromasts of the trunk lateral line.