title: First Assessment of the Sex Ratio for an East Pacific Green Sea Turtle Foraging Aggregation: Validation and Application of a Testosterone ELISA.
abstract: Determining sex ratios of endangered populations is important for wildlife management, particularly species subject to sex-specific threats or that exhibit temperature-dependent sex determination. Sea turtle sex is determined by incubation temperature and individuals lack external sex-based traits until sexual maturity. Previous research utilized serum/plasma testosterone radioimmunoassays (RIA) to determine sex in immature/juvenile sea turtles. However, there has been a growing application of enzyme-linked immunosorbent assay (ELISA) for wildlife endocrinology studies, but no study on sea turtles has compared the results of ELISA and RIA. This study provides the first sex ratio for a threatened East Pacific green sea turtle (Chelonia mydas) foraging aggregation, a critical step for future management of this species. Here, we validate a testosterone ELISA and compare results between RIA and ELISA of duplicate samples. The ELISA demonstrated excellent correspondence with the RIA for providing testosterone concentrations for sex determination. Neither assay proved reliable for predicting the sex of reproductively active females with increased testosterone production. We then applied ELISA to examine the sex ratio of 69 green turtles foraging in San Diego Bay, California. Of 45 immature turtles sampled, sex could not be determined for three turtles because testosterone concentrations fell between the ranges for either sex (females: 4.1-113.1 pg/mL, males: 198.4-2,613.0 pg/mL) and these turtles were not subsequently recaptured to enable sex determination; using a Bayesian model to predict probabilities of turtle sex we predicted all three 'unknowns' were female (> 0.86). Additionally, the model assigned all turtles with their correct sex (if determined at recapture) with 100% accuracy. Results indicated a female bias (2.83F:1M) among all turtles in the aggregation; when focusing only on putative immature turtles the sex ratio was 3.5F:1M. With appropriate validation, ELISA sexing could be applied to other sea turtle species, and serve as a crucial conservation tool.
authors.affiliation: Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, California, United States of America.
authors.forename: Camryn D
authors.initials: CD
authors.lastname: Allen
authors.affiliation: Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, California, United States of America.
authors.forename: Michelle N
authors.initials: MN
authors.lastname: Robbins
authors.affiliation: Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, California, United States of America.
authors.forename: Tomoharu
authors.initials: T
authors.lastname: Eguchi
authors.affiliation: Grice Marine Lab, University of Charleston South Carolina, Charleston, South Carolina, United States of America.
authors.forename: David W
authors.initials: DW
authors.lastname: Owens
authors.affiliation: Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, St. Petersburg, Florida, United States of America.
authors.forename: Anne B
authors.initials: AB
authors.lastname: Meylan
authors.affiliation: Natural Sciences, Eckerd College, St. Petersburg, Florida, United States of America.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Meylan
authors.affiliation: Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, California, United States of America.
authors.forename: Nicholas M
authors.initials: NM
authors.lastname: Kellar
authors.affiliation: Grice Marine Lab, University of Charleston South Carolina, Charleston, South Carolina, United States of America.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Schwenter
authors.affiliation: Veterinary Services, SeaWorld San Diego, San Diego, California, United States of America.
authors.forename: Hendrik H
authors.initials: HH
authors.lastname: Nollens
authors.affiliation: Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, California, United States of America.
authors.forename: Robin A
authors.initials: RA
authors.lastname: LeRoux
authors.affiliation: Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, California, United States of America.
authors.forename: Peter H
authors.initials: PH
authors.lastname: Dutton
authors.affiliation: Marine Mammal and Turtle Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, California, United States of America.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Seminoff
mesh_terms: D063147:Animal Distribution / Q000502:physiology; D000818:Animals; D001499:Bayes Theorem; D002140:California; D056727:Endangered Species; D004797:Enzyme-Linked Immunosorbent Assay / Q000592:standards / Q000662:veterinary*; D005260:Female; D008297:Male; D011863:Radioimmunoassay; D012680:Sensitivity and Specificity; D019849:Sex Determination Processes / Q000502:physiology*; D012744:Sex Ratio; D013739:Testosterone / Q000097:blood*; D014426:Turtles / Q000502:physiology*
chemical_list: D013739:Testosterone