Development of a Nonlethal and Minimally Invasive Protocol to Study Elasmobranch Reproduction

Abstract

An understanding of basic reproductive biology is essential for successful species‐specific management of elasmobranch fishes (sharks, skates, and rays). Such information is often gained through gross dissection or other lethal techniques, which are not appropriate for threatened and endangered species. Previous work on other vertebrates suggested that sex steroid hormones can be extracted from muscle tissues to identify reproductive status. Collecting for muscle biopsy is quick and minimally invasive and can be done without removing an animal from the water. Thus, the objective of the current study was to determine the efficacy of using muscle steroid hormones to assess the reproductive biology of elasmobranch fishes. The results suggest that concentrations of muscle progesterone, testosterone, and estradiol can be successfully quantified to study reproduction by radioimmunoassay. Additionally, there were significant correlations between the plasma and muscle estradiol concentrations in Spiny Dogfish Squalus acanthias and the progesterone, testosterone, and estradiol concentrations in Atlantic Sharpnose Sharks Rhizoprionodon terraenovae. The present investigation thus demonstrates that skeletal muscle is a nonlethally harvestable tissue that is well suited for studying the reproductive biology of elasmobranchs. Received October 12, 2012; accepted March 12, 2013

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

“…The five adult female S. acanthias (mean ± SEM; 80.8 ± 0.8 cm FL) were all in the candle gestational stage (Prohaska, Tsang, Driggers, Hoffmayer, & Sulikowski, and Prohaska, Tsang, Driggers, Hoffmayer, Wheeler et al, ). The overall mean recoveries of plasma P 4 , T, and E 2 were 71%, 90%, and 78%, respectively.…”

“…Despite significant fluctuations in hormone concentrations, particularly in regards to R. terraenovae P 4 and S. acanthias E 2 , the range of values observed in this study are useful in determining gestational stage in both species. For example, using the range of mean hormone concentrations per time period alone (P 4 : 1.9–6.4 ng ml −1 ; T: 4.7–10.1 ng ml −1 ; E 2 : 660–1,049 pg ml −1 ) R. terraenovae would be classified as early/mid gestation based on Prohaska, Tsang, Driggers, Hoffmayer, & Sulikowski () and Prohaska, Tsang, Driggers, Hoffmayer, Wheeler et al (). Similarly, in S. acanthias mean hormone concentrations per time period alone (P 4 : 80–304 pg ml −1 ; T: 47–207 pg ml −1 ; E 2 : 44–104 pg ml −1 ) would classify sharks as candle stage based on Prohaska, Tsang, Driggers, Hoffmayer, & Sulikowski () and Prohaska, Tsang, Driggers, Hoffmayer, Wheeler et al ().…”

“…For example, using the range of mean hormone concentrations per time period alone (P 4 : 1.9–6.4 ng ml −1 ; T: 4.7–10.1 ng ml −1 ; E 2 : 660–1,049 pg ml −1 ) R. terraenovae would be classified as early/mid gestation based on Prohaska, Tsang, Driggers, Hoffmayer, & Sulikowski () and Prohaska, Tsang, Driggers, Hoffmayer, Wheeler et al (). Similarly, in S. acanthias mean hormone concentrations per time period alone (P 4 : 80–304 pg ml −1 ; T: 47–207 pg ml −1 ; E 2 : 44–104 pg ml −1 ) would classify sharks as candle stage based on Prohaska, Tsang, Driggers, Hoffmayer, & Sulikowski () and Prohaska, Tsang, Driggers, Hoffmayer, Wheeler et al (). Hormone concentrations are inherently variable; however, concentrations between stages can be many of orders of magnitude different making actual concentrations potentially not as important as relative concentrations.…”

“…Five adult female Atlantic Sharpnose Sharks ( Rhizoprionodon terraenovae Richardson, 1836) and five adult female Spiny Dogfish ( Squalus acanthias Linnaeus, 1758) were captured and sampled using the methods described in Prohaska, Tsang, Driggers, Hoffmayer, and Sulikowski () and Prohaska, Tsang, Driggers, Hoffmayer, Wheeler et al (). Briefly, R. terraenovae were captured by bottom longline in the northern Gulf of Mexico in an area centered around 88.812°W and 27.887°N, while S. acanthias were captured by bottom trawl and gill net in the US Northwest Atlantic in an area centered around 70.115°W and 42.471°N.…”

Data collection in support of the Endocrine Disruption (ED) assessment for non‐target vertebrates

“…Whereas most studies measured sex steroids in serum or plasma, other matrices were also studied, such as hepatic tissue (Kurobe et al 2016, reference 16381 in Annex B -), muscle tissue (Prohaska et al 2013, reference 17351 in Annex B -), incubation medium from ex vivo testicular tissue incubations ( Schulz et al 1994, reference 8139 in Annex B -) and sperm (Fostier et al 1982, reference 283 in Annex B -). Attempts to use non-invasive methods were also made by measuring hormones in tank water (Sebire et al 2007, reference 1121 in Annex B -).…”