EGGS OF PALAEMON MACRODACTYLUS: II. ASSOCIATION WITH AQUATIC BACTERIA

¹ Aquaculture Program. Animal Science Department. University of California, Davis, CA 95616

Eggs of the shrimp, Palaemon macrodactylus, were studied under various conditions to determine their susceptibility to colonization by aquatic bacteria. Under constant conditions in a laboratory system, bacterial populations monitored over the shrimp's two-week brooding period reached a maximum by seven days and stabilized. Nutrient addition increased bacterial populations substantially and retarded embryonic development, a probable result of hypoxia. Bacterial populations on eggs that had been detached from the egg mass and suspended in the system water increased by nearly an order of magnitude, as did populations on eggs brooded by females whose first pereiopods, or "cleaning chelipeds," had been excised. This result implied that preening activities of the first pereiopods were responsible for dramatically reducing bacterial populations. Bacterial populations on fertilized and unfertilized eggs responded alike to conditions of detachment and nutrient addition, indicating no apparent differences caused by mating, fertilization or development. Eggs extruded without benefit of attachment by the outer investment coat, a condition artificially produced by excising the pleopods, supported high bacterial populations. This may have resulted from additional nutrient escaping from the ooplasm or the greater susceptibility of the exposed vitelline envelope.

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