The cephalic lateral line system and its innervation in Pardachirus pavoninus (Soleidae: Pleuronectiformes): comparisons between the ocular and blind sides

Abstract

The cephalic lateral line system and its innervation were examined and compared between the ocular and blind sides in Pardachirus pavoninus (Soleidae). On the ocular side, the otic and preopercular canals were partly (posteriorly and dorsally, respectively) formed by canalized scales (one and five, respectively), each containing a canal neuromast (i.e., “lateral line scales”) and innervated by the anterior lateral line nerve (otic and mandibular rami, respectively). The canal neuromasts of the five scales were recognized as homologous with superficial neuromasts in other taxa based on innervation. The scales, each with a canal perpendicular to the long axis of the scale, bridged the wide gap between the otic region of the cranium and preopercle. The superficial ophthalmic ramus was bifurcated on both sides, the dorsal ramule emerging from the cranium via a frontal foramen. The buccal ramus on the blind side was intensively ramified in the area made available by migration of the eye to the ocular side. The numbers of canal and superficial neuromasts differed greatly between the sides, being 19 and 173 on the ocular side, and 1 and 465 on the blind side, respectively. Sensory strips of superficial neuromasts on the blind side had clear long and short axes. Numerous dermal papillae occurred on the blind side, forming complex channels, according to directions of the long axes.