Effects of delayed phlebotomy on plasma steroid hormone concentrations in two elasmobranch species

Abstract

Summary Measuring circulating concentrations of steroid hormones can be used as a method for determining reproductive maturity and cycles in elasmobranchs. However, it is unknown how long steroid hormones remain stable in elasmobranch blood following capture, and thus how quickly these samples should be collected for the results of subsequent steroid hormone analyses to be accurate. The objectives of this study were to determine if the sex steroid hormones progesterone, testosterone and estradiol would remain at stable concentrations in the blood of the Spiny Dogfish (Squalus acanthias Linnaeus, 1758) and the Atlantic Sharpnose Sharks (Rhizoprionodon terraenovae Richardson, 1836) that were captured, left on deck and un‐refrigerated for 24 hr. Blood samples were serially drawn from five initially live sharks over a period of 24 hr. While concentrations of all three hormones did significantly fluctuate over the sampling period in both species, the resulting hormone concentrations from each sampling period still fell within the range of previously reported values for each species in their respective reproductive stage. Additionally, no significant changes in hematocrit were detected in either species over the 24‐hr period. This research represents an extreme situation in which sharks were left on deck and un‐refrigerated, and suggests that even when subjected to these conditions steroid hormone concentrations may fluctuate, but the resulting values may still be useful for assessing reproductive stage.

Using reproductive hormones extracted from archived muscle tissue to assess maturity and reproductive status in porbeagles Lamna nasus

“…However, it is important to note that there was overlap in hormone concentrations among stages for both sexes, suggesting there is potential for misclassification of individuals if muscle hormone concentrations are used as the sole predictor of reproductive stage. This overlap is likely associated with individual level variation in hormone concentrations (i.e., Verkamp et al, 2022) rather than the age (Prohaska et al, 2018;Figure S3) or dryness of the sample (Figure S4) given concentrations were found to be variable (from below the detection limit to hundreds of pg g -1 ) among samples that were collected from animals in the same reproductive stage, in the same year, and homogenized with the same ratio of PBS.…”