A COMPARISON OF ARTIFICIAL INCUBATION METHODS USING OVA OF THE RED CRAB GERYON QUINQUEDENS SMITH (DECAPODA, BRACHYURA)

Abstract

The efficacy of culture systems for incubating eggs of the commercially important red crab Geryon quinquedens was investigated. Three artificial systems, two flow-through and one static, were designed and tested over a 60-day incubation period. During the incubation period, death was due primarily to the fungus Lagenidium and other diseased conditions reported herein. Although the long development time of Geryon eggs precluded hatching during the study period, development did proceed to the C+ stage of Meredith (1952). A comparison of egg incubation techniques for decapod crustaceans shows that certain techniques are more successful than others, and the two alternative methods evaluated in the current study are among the most effective. Recent investigations into the physiology, biochemistry, genetics, embryology, taxonomy, aquaculture, and the effects of toxicants on decapod crustaceans have resulted in a marked increase in interest in methodology for hatching and larval rearing of these organisms (Kinne, 1977). In spite of the fact that the decapods are a large and diverse group relatively few techniques for incubating ova have emerged. Allowing the eggs to mature and hatch while still attached to the specialized setae of the female pleopods (Rice and Williamson, 1970) is still the most widespread technique. While release of larvae from ovigerous females is successful in some instances, this method of incubation may be neither possible nor desirable in many others. Successful techniques for the artificial incubation of decapod eggs have used either flow-through or static designs. Flow-through systems are far less intensive and permit mass culture, but static systems permit the effective use of chemotherapeutic agents to control bacterial and fungal pathogens. Hagmeier (1933), in order to hatch eggs of Homarus gammarus, used a flow-through incubator in which a small egg container was maintained in an aquarium with a continuous flow-through of sea water. Phillips (1971) hatched eggs of the English prawn Palaemon serratus using an inverted Fiberglas? cone with a ceramic air diffuser set at its base to provide aeration and circulation while water flowed continuously through the vessel. Lochhead and Newcombe (1942) hatched a high percentage of Callinectes sapidus eggs in a static system consisting of shallow pans providing neither circulation nor chemotherapeutic agents, but they reported increased rates of mortality as egg densities increased. Costlow and Bookhout (1960) developed a static system now widely used. In this system, eggs are placed in compartmentalized plastic boxes, the water treated with antibiotics, and the boxes agitated on a mechanical shaker during incubation. Wickins (1972) hatched ova of Palaemon serratus in a static system, but used gentle water currents created by rising air bubbles to provide continuous circulation of the eggs. The present study was undertaken to develop and evaluate additional artificial hatching methods and to ascertain parameters necessary for successful egg hatching of the red crab Geryon quinquedens in the laboratory. Geryon was selected because data were available for comparison with hatching of eggs carried by the female (Perkins, 1973) and with the static system of Costlow and Bookhout (Sulkin and Van Henkelem, unpublished). In addition, Geryon quinquedens was chosen be