Serological estimation of prey-protein gut-residence time and quantification of meal size for grass shrimp consuming meiofaunal copepods

A series of experiments using serological reagents was conducted to examine predation, ingestion and digestion in a model predator-prey system. The ha rpacticoid copepod Amphiascoides atopus, obtained from mass culture, was us ed as prey and the grass shrimp, Palaemonetes pugio, as predator. Bulk-gut passage time in P. pugio was measured by visualization of latex beads and r anged from 0.5 to 4 h in starved and continuously-fed grass shrimp. A polyc lonal antibody was prepared from crude extracts of A. atopus; cross reactio ns with P. pugio and three other crustaceans were ei ther negligible or not detected using slide agar-gel-double-immunodiffusion (AGID) and Western bl ot preparations. The presence of A. atopus antigens was detected with great sensitivity (e.g., seven copepods, 35 mu g dry weight, gave positive resul ts) in grass shrimp gut contents even when proteins of other crustacean pre y were present. Prey-proteins could be detected for as long as 4 h with AGI D and 8 h with Western blot techniques. Individual grass shrimp that were f ed A. atopus and consumed from 0 to 98 copepods h(-1) were subjected to Wes tern-blot preparation with chemiluminescence detection and densitometric ev aluation. There was a significant curvilinear relationship between protein content and the number of copepod prey ingested. Results suggest that serol ogical techniques can be modified to estimate the mass or abundance of stan dard-sized pl ey ingested by field-collected predators. (C) 2000 Elsevier S cience B.V. All rights reserved.