Ontogenetic development of otoliths in alligator gar

Alligator Gar Atractosteus spatula is a species of conservation concern throughout its range and an examination of otoliths during early development would aid understanding its life history and ecology. We conducted X-ray computed tomography (CT) scans, scanning electron microscopy (SEM), and light microscopy to examine the three pairs of otoliths and how they developed over time in relation to fish size and age. The sagittae are the largest, with distinct dorsal and ventral lobes, and covered with small otoconia concentrated in the sulcul region. The sagittae exhibited allometric growth, increasing more rapidly in the ventral lobe than in the dorsal. The asterisci were smaller and also exhibited small otoconia on their surface, but much less than the sagittae. The lapilli were oriented laterally, in contrast to the sagittae and asterisci that were oriented vertically, with a hump on the dorsum and very large otoconia on the lateral surface that appeared to fuse into the main otolith a...