Development of the visual system and inferred performance capabilities of larval and early juvenile scombrids

Abstract

Development of the visual system in larval and early juvenile Euthynnus lineatus, Auxis spp., and Scomberomorus sierra was examined histologically. First‐feeding larvae of all three taxa possess a pure cone retina, with theoretical acuities ranging from 50 min of arc in Scomberomorus sierra to about 60 min of arc in Euthynnus lineatus and Auxis spp. Accommodative structures (lens retractor muscle and suspensory ligament) first appear during the late preflexion stage. Rod precursors appear in the flexion and early postflexion stages. By the late postflexion stage, the appearance of retinomotor movements indicates functionality of rods. The optic tectum is prominent in the midbrain at the first‐feeding stage and exhibits rapid growth and differentiation. The torus longitudinalis, an important sensory integration center of the tectum, does not develop until the early postflexion stage. Development of the visual system in larval scombrids is advanced and is likely involved in rapid improvements in foraging abilities and piscivory.