Date of Award

Spring 1993

Project Type

Dissertation

Program or Major

Zoology

Degree Name

Doctor of Philosophy

First Advisor

John J Sasner, Jr

Abstract

Mya arenaria (L.) is susceptible to the disease, hematopoietic neoplasia (Hn), in which atypical cells invade the blood and connective tissue of the clam's organs. In this study impacts of Hn on the reproductive and excretory systems were examined in clams collected from New Bedford Harbor and Little Buttermilk Bay, Buzzards Bay, MA.

The relationships between Hn seasonality and reproduction were evaluated from fresh blood samples and histological analysis of gonads. Both clam populations had biannual reproductive cycles with spawnings in the spring and fall. Hn prevalence exhibited some seasonality with maxima in the fall and late winter-early spring. Reproductive activity may enhance Hn prevalence, which in turn diminishes reproductive output.

Clams between 40-70 millimeters in length showed the highest prevalence of disease. Prevalence of Hn in a single cohort increased as these clams grew into the disease-susceptible size ranges. Hn may alter the population size distribution by eliminating particular size classes.

The radiopharmaceuticals, Tc-99m-disofenin and Tc-99m-sulfur colloid, were injected into the sinus around the anterior adductor muscle, and their accumulation was determined through scintigraphy, gamma well counting and autoradiography. By 7 hrs, 60% of the Tc-99m-disofenin was localized within the kidney. Whole body levels indicate that 15% of the disofenin was lost over 7 hrs. While Hn cells increasingly invade the clam's connective tissue, it appears that the kidney may not be as heavily impacted as other organs. A reduction in phagocytosis was indicated by a decrease in hemocyte Tc-99m-sulfur colloid activity with increasing stages of Hn. This loss of phagocytic capability impairs the clam's ability to remove foreign material from circulation, transport nutrients and repair wounds. Overall, Hn affects physiological processes including reproduction and excretion and alters the population size distribution of this commercially important bivalve.

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