FEEDING BEHAVIOR AND REPRODUCTIVE CYCLES IN PISASTER OCHRACEUS

¹ Department of Zoology, University of Washington, Seattle, Washington, and Friday Harbor Laboratories, University of Washington, Friday Harbor, Washington

1. Pisaster ochraceus shows a definite seasonal feeding periodicity, in terms of per cent of the population feeding at one time, dry weight ingested, and in composition of ingested prey. Less than 5% are feeding in January and February; 60% to 80% in July and August. The dry weight ingested varies from about 3 grams per tidal cycle per 100 animals in the winter to about 30 grams in the summer months. Chitons are the principal winter prey, while barnacles and limpets are fed on most often in the summer.

2. Cyclic changes in gonad and pyloric caeca size and histological appearance characterize this species. The gonads are smallest in the fall, and grow during the winter to a maximum in the late spring, when spawning occurs. The pyloric caeca size-changes are approximately inverse to those of the gonads. Seasonal histological changes of the oocytes, and storage granules in the pyloric caeca, are correlated with the gross organ patterns.

3. Two factors are suggested as explanations for these cyclic phenomena. (a) More favorable summer feeding for both the adult and larval Pisaster may have led to evolution of a storage function for the pyloric caeca; nutrients could then he transferred to the gonads in the winter. (b) It would seem evolutionarily advantageous to fill more of the limited space available in the arms with gonads than with pyloric caeca in the spring, at the time of spawning.

This article has been cited by other articles:

				C. D. G. Harley, M. S. Pankey, J. P. Wares, R. K. Grosberg, and M. J. Wonham Color Polymorphism and Genetic Structure in the Sea Star Pisaster ochraceus Biol. Bull., December 1, 2006; 211(3): 248 - 262. [Abstract] [Full Text] [PDF]

				E. Sanford Water Temperature, Predation, and the Neglected Role of Physiological Rate Effects in Rocky Intertidal Communities Integr. Comp. Biol., August 1, 2002; 42(4): 881 - 891. [Abstract] [Full Text] [PDF]

				E. Sanford Regulation of Keystone Predation by Small Changes in Ocean Temperature Science, March 26, 1999; 283(5410): 2095 - 2097. [Abstract] [Full Text]