BEHAVIORAL (FEEDING) RESPONSES OF THE CRAYFISH, PROCAMBARUS-CLARKII, TO NATURAL DIETARY ITEMS AND COMMON COMPONENTS OF FORMULATED CRUSTACEAN FEEDS

We have examined the behavioral (feeding) response of Procambarus clar kii to natural dietary items (zooplankton, live fishes, dead fishes, a nd fish eggs) and common components of formulated feeds used in the aq uaculture industry (soybean meal, fish meal,;om meal, alfalfa meal, an d vitamin C). The feeding response by P. clarkii was determined using an ordinally ranked, whole-animal bioassay that included the following behaviors: (1) movement of the maxillipeds for longer han three secon ds, (2) increased movement of the walking legs with dactyl ''probing,' ' (3) movement of walking legs to the mouth, and (4) orientation of th e entire body towards the odor source. Feeding behavior was determined in response to intact items: bathwater containing aqueous leachates f rom intact items, water and methanol fractions of bathwater eluted thr ough a C-18 resin Rash chromatography column, and size fractions of ba thwater containing either molecules less than or equal to 10,000 Da or molecules > 10,000 Da. All fractions tested were significantly stimul atory. Zooplankton was the most stimulatory of the natural dietary ite ms tested. However, the C-18 water fraction of the soybean meal bathwa ter before size fractionation (containing molecules both < 10,000 and > 10,000 Dal was the most stimulatory of the common feed components an d more stimulatory than the zooplankton. Proximate analysis indicated that the compounds present in this fraction were ca. 51% soluble carbo hydrate, 4% soluble protein, and 45% unknown (assumed to be insoluble carbohydrates, insoluble proteins, and ash). We hypothesize that the p rimary compounds in soybean meal responsible for eliciting a feeding r esponse in P. clarkii are soluble carbo hydrates and/or glycoproteins.