Measurement of Serum 1α-hydroxycorticosterone (1αOH-B), the Elasmobranch Stress Hormone, in Select Shark Species
An in-house enzyme immunoassay1 (EIA) was developed to measure the unique elasmobranch stress/ionoregulatory hormone 1α-hydroxycorticosterone (1αOH-B). Elasmobranch stress evaluations have been limited to secondary stressors, primarily blood gasses.2,3,4,5 Variability in the stress responses amongst different species has been noted which can be assessed with this assay and then compared to secondary stressors.6,7 In this pilot study, banked sera were analyzed for 1αOH-B in aquarium-managed bonnetheads (Sphyrna tiburo, N=10) and scalloped hammerheads (Sphyrna lewini, N=3), along with wild juvenile tiger sharks (Galeocerdo cuvier, N=32).
Initial findings show that 1) 1αOH-B has markedly different concentrations and ranges among species (Figure 1), and 2) 1αOH-B becomes elevated when animals undergo a stressful event (like illness). In S. tiburo, values clustered (7 to 122 ng/ml) except in one sick animal which experienced severe lactic acidosis. In S. lewini, values were 6 to 64 ng/ml, with 3.5-fold higher values in one critically ill animal. In comparison, long-line caught tiger sharks had an attenuated range (4 to 17 ng/ml).
In the bonnetheads and scalloped hammerheads, 1αOH-B concentrations increased in a linear fashion with increasing lactate values (Figure 2). Glucose increased and pH decreased with increased 1αOH-B, as expected. These data suggest that the 1αOH-B EIA can be a valuable tool. Additional testing is important to further biologically validate this assay. Improved measurement of stress, reproductive, and metabolic hormones in elasmobranchs will be important for many aspects of collection, transport, medical treatment, and aquaria and conservation management of these charismatic and ecologically important species.
The authors thank the Animal Husbandry and Animal Health teams at The Seas with Nemo and Friends at Epcot. Special thanks to Charlene Burns for her assistance in the project. We also thank the staff at the Bimini Biology Field Station
* Presenting author
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