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. 2021 Jul 26;11(1):15168.
doi: 10.1038/s41598-021-94557-y.

Correlations between environmental salinity levels, blood biochemistry parameters, and steroid hormones in wild juvenile American alligators (Alligator mississippiensis)

Patricia C Faulkner  1 , Ruth M Elsey  2 , David Hala  3 , Lene H Petersen  3
Affiliations

Correlations between environmental salinity levels, blood biochemistry parameters, and steroid hormones in wild juvenile American alligators (Alligator mississippiensis)

Patricia C Faulkner et al. Sci Rep. .

Abstract

American alligators (Alligator mississippiensis) inhabit freshwater wetlands that are vulnerable to salinization caused by anthropogenic alterations to freshwater flow, in addition to storm surges, sea level rise, and droughts. Salinization of coastal freshwater habitats is a growing concern in a changing climate due to increased frequency and intensity of storm surges and drought conditions. This study opportunistically sampled juvenile male and female wild alligators in various salinities each month excluding November, December, and January for one year at Rockefeller Wildlife Refuge in coastal Louisiana. Blood plasma biochemistry parameters including electrolyte levels were subsequently measured. In addition, levels of various renin-angiotensin-aldosterone system hormones, glucocorticoids, androgens, estrogens, and progestogens were analyzed using liquid chromatography and tandem mass spectrometry. Only males were sampled in hyperosmotic environments (> 10‰) during dry conditions in late summer 2018. In juvenile males, plasma Na+, Cl-, and the progestogen 17α,20β-dihydroxypregnenone were significantly and positively correlated with environmental salinity. However, variation in glucocorticoids, androgens, and estrogens were not associated with hypersaline water while sex steroids showed significant seasonal variation. This study demonstrated significant correlation of environmental salinity with electrolyte levels and a sex steroid in wild juvenile alligators, and to our knowledge represents the first measurement of 17α,20β-dihydroxypregnenone in alligators.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Rockefeller Wildlife Refuge in Grand Chenier, Louisiana (U.S.A.) where wild American alligators (Alligator mississippiensis) were sampled from various locations. Map generated using ArcMap version 10.8 (https://desktop.arcgis.com/en/arcmap/) with satellite imagery obtained from the GIS Community Maps Program. (https://www.arcgis.com/home/item.html?id=10df2279f9684e4a9f6a7f08febac2a9).
Figure 2
Figure 2
Monthly variation in total length (a) of wild juvenile American alligators (Alligator mississippiensis) and environmental salinity in which animals were located (b). *Denotes significant differences between males and females during the indicated month.
Figure 3
Figure 3
Partial redundancy analysis using environmental salinity in which American alligators (Alligator mississippiensis) were found as a predictor and holding total length, sex, and month constant. Abbreviated are angiotensin II (ANG II), aldosterone (ALDO), 11-deoxycortisol (11-DC), corticosterone (CORT), pregnenolone (P5), 17α-hydroxypregnenolone (17-OHP5), progesterone (P4), 17α-hydroxyprogesterone (17-OHP4), 17α,20β-dihydroxypregnenone (DHP), androstenedione (A4), 5α-dihydrotestosterone (DHT), testosterone (T), estrone (E1), 17β-estradiol (E2), estriol (E3), sodium (Na), chloride (Cl), potassium (K), calcium (Ca), phosphorus (P), alkaline phosphatase (ALP), aspartate aminotransferase (AST), and alanine aminotransferase (ALT).
Figure 4
Figure 4
Spearman rank correlation between environmental salinity and plasma sodium (a,d), chloride (b,e), and potassium (c,f) in juvenile male and female American alligators (Alligator mississippiensis). rho Spearman’s rho, p significance of correlation.
Figure 5
Figure 5
Spearman rank correlation between environmental salinity and plasma hormone levels found to be significant (p < 0.05) in juvenile male (a–c) and juvenile female (d–f) American alligators (Alligator mississippiensis). rho Spearman’s rho, p significance of correlation.
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References

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