Portoni, B., Smith, N., Dixon, B., Kawahigashi, D.
Abstract:
The cyanobacteria Spirulina spp. is commercially produced for human consumption as well as agricultural feed ingredients. Recently, whole Spirulina and cell extracts were found to enhance immunity in animals by increasing phagocytic activity. The purpose of this study was to determine the effect of a Spirulina enhanced diet on the nonspecific immune response of Channel catfish, Ictalurus punctatus.
The sample population consisted of "young of the year" channel catfish obtained from Fish Producers, Niland, CA. Fish (50/tank) were maintained in glass aquaria equipped with undergravel filters. All fish were fed a diet of Trout starter diet (Ranger, Inc.) for a month until they were large enough to ingest adult brine shrimp (Artemia franciscana). The control diet consisted of adult brine shrimp. The test diet consisted of adult brine shrimp bioencapsulated with Spirulina. Adult brine shrimp were allowed to feed on dried Spirulina powder for 3-4 hours to maximize bioencapsulation.
Preliminary studies in our laboratory indicated that channel catfish fed Spirulina had an increase in the number of splenic macrophages determined by esterase staining compared to controls. Not only were more macrophages present in the spleen, but also the macrophages appeared "activated". Activation, determined by morphology on scanning electron microscopy, was characterized by the presence of numerous surface folds and ruffles. This research was performed on a single population of catfish over a period of months. While the data suggest nonspecific immunostimulation elicited by Spirulina in the diet, further study on different populations of fish is underway to confirm the preliminary data.
(Department of Biological Sciences, California State University, Hayward, CA 94542)
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