Probopyrus pandalicola: Discontinuous ingestion of shrimp hemolymph

Abstract

Grass shrimp, Palaemonetes pugío, were injected with 14C-labelled amino acids to determine hemolymph losses caused by an ectoparasite, the isopod Probopyrus pandalícola (Packard) (Epicaridea; Bopyridae). The female parasites were removed from labelled shrimp at intervals over 36 hr to monitor hemolymph ingestion. The parasites were found to feed discontinuously throughout the host's molt cycle, ingesting an average of 7–9 μl of hemolymph over a 24-hr period. Feeding was curtailed in darkness; probopyrids consumed only 2–3 μl of hemolymph after 12 hr in the dark. In all experiments, a number of parasites did not feed. The results of this study indicate that significant losses of the host's hemolymph result from the feeding activity of P. pandalicola. The determination of these losses is essential to begin testing the hypotheses that losses of hemolymph inhibit gonadogenesis in the host by either (i) creating a nutrient imbalance or (ii) depleting titers of reproductive hormones.