Superfund Research Program
Sentinel Species: Xenobiotics, Toxicity, and Reproduction
Project Leader: Ian P. Callard
Grant Number: P42ES007381
Funding Period: 1995 - 2000
Analysis of data indicates significant reproductive deficits in turtles on Cape Cod, from a site adjacent to toxic plumes emanating from the Massachusetts Military Reservation (MMR). These reproductive deficits, detailed below, may be the result of past and/or continuous exposure to unidentified endocrine disruptors, which interfere with the hypothalamic-pituitary-gonadal axis at one or more sites. Researchers found that for a given body weight at which 95% of females are normally sexually mature (375-395 gm), significantly more animals were immature, based on ovarian and oviduct weight, and follicular maturation. In the sexually mature females, gonadosomatic index (GSI) was marginally lower at the impacted site, and as a correlate of this, the number of follicles in the 1-5 mm size class was significantly less (p< .05) in these animals. Numbers of follicles in other size classes (5-10 mm; 10-15 mm) were not different from the two sites, nor were the numbers of ovulated eggs (average clutch size 6 at each site). Follicles less than 1.0 mm remain to be counted. Plasma estradiol (E2) levels over the cycle were significantly lower at the impacted site; this correlates well with two indices of E2 action: oviduct weight and plasma vitellogenin (vtg) level, both being significantly lower in animals from the impacted site. No vtg was detectable in males or immature females, indicating that these animals are not exposed to significant levels of xenoestrogen. Plasma levels of progesterone (P) and testosterone (T) remain to be assayed for both sexes. In males, no significant differences were found in testis weight between the two sites; however, sperm numbers, but not viability (95%), were much lower (600,000 per ml on average) in Cape Cod animals (whether from impacted or non-impacted sites) than animals from Wisconsin (1.2 million per ml). This suggests a geographic difference that may or may not be due to local xenobiotic conditions. Other factors such as body weight may be important. Histological studies of the testis reveal a vacuolated, disorganized tubular epithelium in several animals from the impacted site. These are reminiscent of testicular changes reported for rats treated with phthalates. Histological work is not yet complete. Researchers hypothesize that these data indicate a significant degree of hepatic induction, due to exposure to a low-level mixture of interacting xenobiotic species (hydrocarbons, metals and possibly other endocrine disruptors). The observed impact on the liver can be correlated with previously described changes in hepatic heavy metals, glutathione-s-transferase and CYP1A1.