Using Plasma Vitellogenin in Loggerhead Sea Turtles to Assess Reproductive Maturation and Estrogen‐Like Contaminant Exposure

摘要

Vitellogenin (VTG), an egg yolk precursor, is abnormally produced by male and juvenile oviparous speciesafter exposure to estrogens. Plasma VTG in loggerhead sea turtles (Caretta caretta) helped us understandtheir reproductive maturation and investigate it as a biomarker of contaminant exposure. The presence of VTG wasscreened in plasma from 404 loggerheads from the northwestern Atlantic Ocean using a freshwater turtle antibody inwestern blots. The concentrations of VTG were semiquantified using band intensities calibrated to results from a loggerheadantibody enzyme‐linked immunoassay. The detection and concentrations of VTG were in (from highest tolowest): nesting females, in‐water adult females, subadult females, smaller females, unknown sex, and males. Loggerheadsfrom this region begin vitellogenesis at ?77 cm straight carapace length. We classified VTG expression as abnormalin nine male or juvenile turtles. Organochlorine contaminant (OC) concentrations were measured in blood and/orfat biopsies of some turtles. One abnormal VTG female had the second highest fat polychlorinated biphenyl (PCB) and4,4′‐dichlorodiphenyldichloroethylene concentrations compared among 43 VTG‐negative juveniles. The nine VTGabnormalturtles had average blood PCB concentrations 8.5 higher, but not significantly different, than 46 VTGnegativejuveniles (p = 0.453). In turtles less than 77 cm, blood PCB concentrations were significantly, but weakly, correlatedwith semiquantified VTG concentrations (tau = 0.1, p = 0.004). Greater blood OC concentrations were found inadult females than in males, which motivated the creation of a conceptual model of OC, VTG, and hormone concentrationsacross a reproductive cycle. A decision tree is also provided incorporating VTG as a sexing tool. Abnormal VTGexpression cannot conclusively be linked to endocrine disruption caused by these OC concentrations. Studies shouldfurther investigate causes of abnormal VTG expression in wild sea turtles.