Visual field of cultured striped trumpeter Latris lineata (Teleostei) larvae feeding on rotifer prey

The visual field of striped trumpeter Latris lineata larvae fed rotifer prey was determined from analysis of feeding behaviour in the horizontal plane. The visual field was forward and laterally directed, characterised by maximum reactive distances (distance at which the predator first detects and reacts to the prey) of 5.07 mm and 5.25 mm on days 13 and 17 post-hatching, respectively, 97% of mean larval length. This confirmed the predicted horizontal visual field, forward and laterally directed, derived from higher cone cell densities in the dorso-temporal and medial regions of the retina compared with ventral regions. The visual field of prey detection expanded laterally with ontogeny as a wider range of reactive angles was used by 17 day-old than 13 day-old larvae. Larvae displayed a saltatory searching pattern, periodically stopping to scan for prey throughout the visual field, and exhibited a side-to-side movement of the head as they approached and stopped, prior to striking at a detected prey item. Larvae on day 17 post-hatching terminated 35% of feeding sequences at the pre-strike position, at a mean distance from prey of 0.58 mm.