Epibionts of pond-reared adult Malaysian prawns, Macrobrachium rosenbergii (de Man), in South Carolina

Abstract

During 1976, epibionts were noted on adult Malaysian prawns reared in a special ‘brood stock pond’. These epibionts have not previously been recorded on Macrobrachium rosenbergii. Dense algal growths, covering much of the carapace, were observed on 58.3% of the males (mean size, 147.1 g) and on none of the females at harvest. Species composition was primarily (about 90%) the Chlorophyte Oedogonium crassiusculum, with the Cyanophyte Lyngbya, the secondary dominant. The large infested males were sluggish and in some cases functionally blind due to the algal covering. However, once moved to indoor culture tanks the algae were lost and the prawns' behavior returned to normal. Eggs of the water boatman, Ramphocorixa acuminata, were observed on 52.5% of the females (mean size, 78.0 g) and 5.9% of the males at harvest. Egg deposition was limited to the cephalothorax and/or the first and/or second abdominal segments. This epibiont was not noted in the six adjacent rearing ponds containing approximately 84,000 smaller prawns. The insect eggs appeared to cause no injury and disappeared shortly after the infested prawns were returned to laboratory tanks. Although both epibionts exhibited apparent sex specificity in the brood stock pond, data from other rearing ponds did not support this specificity. The occurrence of these epibionts should pose no problem to the successful pond culture of M. rosenbergii in South Carolina.