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A pilot study to understand tooth replacement in near-harvest farmed saltwater crocodiles (Crocodylus porosus): Implications for blemish induction

Finger, John W., Thomson, Peter C., Isberg, Sally R.
Aquaculture 2019 v.504 pp. 102-106
Crocodylus porosus, alligators, crocodiles, eyes, juveniles, teeth, Australia
Saltwater crocodiles (Crocodylus porosus) are farmed in Australia primarily for their belly skin. The desirability and ultimately the value of each skin depends on the extent and location of various industry-defined defects. Anecdotal observations suggest that conspecific interactions are the main contributors with the protrusive 4th dentary teeth (i.e. eye teeth) the most likely cause. It is well known that crocodilians undergo continual tooth replacement, yet no study has investigated tooth replacement rates or tooth growth dynamics in juvenile saltwater crocodiles. In this pilot study, we repeatedly measured eye tooth crown height and observed eye tooth replacement in individually-housed juvenile saltwater crocodiles (n = 98) accounting for 290 individual teeth. The majority of teeth were replaced every three to six months (n = 172) but nine teeth were not replaced over the 15-month study period. After a tooth was lost, the need to replace it quickly was evidenced by a faster tooth growth rate in the first three months (11.07 ± 0.17 mm) but subsequently slowed to a model-adjusted asymptote of 14.03 ± 0.27 mm (p < .001). Interestingly, teeth on the left side of the mandible were, on average, 0.43 ± 0.16 mm shorter than those on the right (p < .001) and, although just outside 5% significance, were replaced 1.20 times as often. Together this is suggestive that crocodiles may preference food capture with the left-hand side of their mouth but requires more structured behavioural observations to confirm. Unusually, the eye-teeth of eight crocodiles did not protrude, which is a normal characteristic of crocodiles compared to alligators, but instead were observed to be growing into the interior of the mouth. This study begins to provide some context to tooth biology when preemptive solutions to tooth-induced blemishes are being sought.