Plasma steroid concentrations of adult male Atlantic sharpnose sharks, Rhizoprionodon terraenovae, in the northern Gulf of Mexico, with notes on potential long term shifts in reproductive timing

• Published in: Environmental biology of fishes Vol. 88; no. 1; pp. 1 - 7
• Main Authors: Hoffmayer, Eric R, Sulikowski, James A, Hendon, Jill M, Parsons, Glenn R
• Format: Journal Article
• Language: English
• Published: Dordrecht Dordrecht : Springer Netherlands 01-05-2010; Springer Netherlands; Springer; Springer Nature B.V
• Subjects: Agnatha. Pisces; Animal and plant ecology; Animal reproduction; Animal Systematics/Taxonomy/Biogeography; Animal, plant and microbial ecology; Animals; Autoecology; Biological and medical sciences; Biomedical and Life Sciences; Environment; Freshwater & Marine Ecology; Fundamental and applied biological sciences. Psychology; Life Sciences; Males; Marine; Marine biology; Nature Conservation; Reproductive cycle; Rhizoprionodon terraenovae; Sea surface temperature; Sharks; Spring; Steroids; Vertebrata; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Zoology; Gulf of Mexico; ASW, USA, Alabama, Mississippi Sound; ASW, Mexico Gulf; Testosterone; Atlantic sharpnose shark; Estradiol; Gonadosomatic index; Reproductive cycle; Steroid; Androgen; Male; Long term; Blood plasma; Concentration measurement; Marine environment; Vertebrata; Reproduction; Pisces; Testicular hormone; Timing; Sex steroid hormone; Chondrichthyes
• ISSN: 0378-1909; 1573-5133
• DOI: 10.1007/s10641-010-9603-3

In previous literature it was proposed that Atlantic sharpnose sharks, Rhizoprionodon terraenovae, from the western Atlantic Ocean (WAO) population exhibited differences in their reproductive timing when compared to the northern Gulf of Mexico (GOM) population. The objective of the current study was to examine the reproductive cycle of mature male sharpnose sharks from the northern GOM population. Plasma testosterone (T) and estradiol (E₂) were measured from 76 mature male sharpnose sharks sampled from 1999 to 2001, and the gonadosomatic index (GSI) was determined for 53 additional mature males sampled from 2007-2008. Plasma T, E₂, and GSI exhibited similar cycles with peak values occurring in late spring (April/May) and lowest values occurring during the summer. These results suggest that male sharpnose sharks in the northern GOM are reproductively active one to two months earlier than previously reported, which now brings them into synchrony with the WAO population. Interestingly, this shift in reproductive timing corresponds with a 3.0°C (13.4%) increase in spring sea surface temperature (SST) from the Mississippi Sound over a 29 year period, which could translate into GOM male sharpnose sharks becoming reproductively active earlier in the year thus explaining the late spring peak in GSI.