Juvenile Ribbontail Stingray, Taeniura lymma (Forsskål, 1775) (Chondrichthyes, Dasyatidae), demonstrate a unique suite of physiological adaptations to survive hyperthermic nursery conditions

Abstract

Juvenile ribbontail stingrays, Taeniura lymma (Forsskal, 1775) of the tropical West Pacific inhabit mangal and seagrass nurseries that often experience rapid and extreme increases in water temperature. We hypothesized that juvenile rays possess a thermal strategy similar to other hyperthermic specialists, in which fish prefer high temperatures, are always prepared for thermal extremes regardless of previous thermal history, and exhibit low metabolic thermal sensitivity. Critical thermal methodology was used to determine the thermal niche, and a thermal gradient used to estimate stingray final preferendum. Temperature quotients (Q10) were calculated from metabolic rates determined at three temperatures using flow-through respirometry. As predicted, juvenile rays showed a relatively small thermal niche dominated by intrinsic tolerance with limited capacity for acclimation. Thermal preference values were higher than those reported for other elasmobranch species. Interestingly, the temperature quotient for juvenile rays was higher than expected, suggesting that these fish may have the ability to exploit the thermal heterogeneity in their environment. Temperature likely acts as a directing factor in this species, separating warm tolerant juveniles from adults living in deeper, cooler waters.