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Data from: Ontogenetic development of otoliths in alligator gar

Citation

Long, James M.; Snow, Richard A. (2017), Data from: Ontogenetic development of otoliths in alligator gar, Dryad, Dataset, https://doi.org/10.5061/dryad.t1d8k

Abstract

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 as the fish grew. Based on size measurements and ring counts in all three pairs of otoliths from known-age Alligator Gar sampled weekly through 91 days after hatch (N =101), we developed regression models to examine otolith growth and predict age. All relationships were significant and highly explanatory (r² ≥ 0.93), but the strongest relationship between otolith and fish size existed for measurements from sagittae (r² = 0.98) and age predictions from the lapillus (r² = 0.99). Age prediction models all resulted in a slope near unity, indicating that ring deposition occurred approximately daily. The first ring in sagittae and lapilli corresponded to swim-up whereas the first ring formed in asterisci approximately 8 days after swim-up. These results fill a gap in knowledge and can aid understanding of evolutionary processes as well as provide useful information for management and conservation.

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