ASSOCIATIONS BETWEEN SENSORY DEVELOPMENT AND ECOLOGY IN 3 SPECIES OF CLUPEOID FISH

Sensory development was examined in larvae of three species of clupeoi d fish, Atlantic menhaden (Brevoortia tyrannus, Clupeidae), scaled sar dine (Harengula jaguana, Clupeidae), and bay anchovy (Anchoa mitchilli , Engraulidae). Differences in habitats occupied by these species allo wed the testing of hypotheses relating timing of sensory ontogeny to h abitat shifts in fish larvae. Migration of menhaden from offshore to e stuarine waters coincided with, or was preceded by, auditory bulla inf lation, development of rod photoreceptors, onset of retinal summation, improvements in visual acuity, and formation of cephalic lateral-line canals. Examination of developmental patterns in sardine and anchovy larvae, both of which live inshore throughout the larval period, showe d that some of these associations between habitat and sensory morpholo gy were adaptive and some coincidental. Inflation of the auditory bull ae occurred earlier in the larval period in anchovy than in menhaden. Specializations for enhanced visual sensitivity occurred earliest in a nchovy but were not different between sardine and menhaden. There was no correspondence between habitat and visual acuity or lateral-line de velopment. Thus, ontogeny of auditory bulla inflation and retinal sens itivity may coincide with habitat shifts, at least at the family level , but lateral-line development is more constrained by phylogeny than a dapted to ecology.