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Comparative histology of gonadal neoplasms in 14 marine bivalve species or hybrids from 5 countries described in the literature and/or archived in the Registry of Tumors in Lower Animals (RTLA), Washington. DC. USA, revealed 3 basic histotypes. Hundreds of cases were of germ cell origin with hfferent stages of development. They consisted of undifferentiated germ cells that filled individual follicles (stage l ) , were present throughout the gonadal area (stage 2), or had spread to outlying tissues (stage 3). Five cases were of stromal origin. The connective tissue comprising these tumors ranged from vesicular to myxoid to spindle-cell. As these tumors grew, they invaded and destroyed normal follicles. Three cases representing a third histotype appeared to be of both germ cell and stromal origin. Two of these 3 were among 15 Crassostrea virginica recently collected from the Pawcatuck River, Rhode Island, USA. In the most advanced case, basophilic hypertrophied neoplastic germ cells were rapidly proliferating along the walls of gonadal follicles and the ducts that extended into the mantle, while the central region of the tumor mass was densely flbrous. Some neoplastic cells in follicles adjacent to normal ova-bearing follicles were differentiating into spermatocytes. Tumor cells aggressively crossed the follicular basement membrane, invaded the vesicular connective tissue supporting the gill axis, and formed a cystic mass along the lumina1 wall of the branchial vein. The less advanced C. virginica case had a smaller, less aggressive tumor but its basic features were similar. The third case similar in composition, pattern, and behavior was in a C. gigas that had been collected during the 1960s from the Willapa Bay. Washington, USA, and had originally been interpreted as a fibroma. All 3 of these mixed gonadal-stromal neoplasms are presently diagnosed as gonadoblastomas.

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The gene for vitellogenin, an egg yolk protein precursor, is usually silent in male fish but can be induced by estrogen exposure. For this reason, vitellogenin production in male fish has become a widely used indicator of exposure to exogenous estrogens or estrogen mimics in the aquatic environment. The utility of this indicator to predict impacts on fish reproductive success is unclear because information on the relationship between male plasma vitellogenin and reproductive end points in male and female fish is limited. In the research reported in this article, we investigated whether the presence of male plasma vitellogenin is a reliable indicator of decreased reproductive success in mature fish. Adult and sexually mature male and female cunner (Tautogolabrus adspersus) were exposed to 17ss-estradiol, ethynylestradiol, or estrone, three steroidal estrogens that elicit the vitellogenic response. Data were gathered and pooled on egg production, egg viability, egg fertility, sperm motility, and male plasma vitellogenin concentrations. All males, including two with plasma vitellogenin levels exceeding 300 mg/mL, produced motile sperm. Neither percent fertile eggs nor percent viable eggs produced by reproductively active fish demonstrated a significant correlation with male plasma vitellogenin concentrations. Male gonadosomatic index and average daily egg production by females showed significant, but weak, negative correlation with male plasma vitellogenin concentrations. Results suggest that male plasma vitellogenin expression is not a reliable indicator of male reproductive dysfunction in adult cunner exposed to estrogens for 2-8 weeks during their reproductive season, at least in relation to capacity to produce motile sperm or fertilize eggs. Male plasma vitellogenin expression may serve as an indicator of reduced female reproductive function caused by estrogen exposure.

No abstract