Reference: Biol. Bull., 150: 522-530. (June, 1976) HYDRATION IN THE SAND SHRIMP CRANGON SEPTEMSPINOSA: RELATION TO DIET J. ROSS WILCOX i AND H. PERRY JEFFRIES Graduate School of Oceanography, University of Rhode Island, Kingston, Rhode Island 02881 The sand shrimp Crangon septemspinosa Say 1818 is a common inhabitant of estuaries along the northwestern Atlantic from Newfoundland to eastern Florida (Squires, 1965; Williams, 1965; Price, 1962). The biology and ecology of the species is discussed by Enibich (1973), Haefner (1969a, 196%, 1970, 1971, 1972, 1973), Price (1962), Regnaiilt (1970, 1971, 1972), Regnault and Costlow (1970), Sandifer (1975), Wilcox (1972), Wilcox and Jeffries (1973, 1974). Hydration levels of crustaceans are affected by a variety of environmental and physiological parameters, and the literature detailing these factors is extensive (e.g., Passano, 1960; Roberston, 1960). For example, molting of crustaceans has been scientifically documented for almost fifty years, and its endocrinology and ancillary process of growth is known in detail (Hoar, 1975). The literature dealing with hydration in C rang on spp. is, however, quite limited. To document water content over a molt cycle, a generalized account suggested by Lockwood (1967) must be used. Thus, water content can vary from a high of 86% immediately after ecdysis (Drach Stage Ao) to a low of 59-61% during Drach Stage D. The time spent at high levels of hydration (greater than 80% water) is approximately 10% of a molt cycle. Weber and van Marrewijk (1972) negatively correlated percentage water content of muscle in Crangon crangon to increasing environmental salinity and determined that the shrimp possesses a relatively efficient water regulation system. Haefner (1969b) determined the osmoregulatory patterns of C. septemspinosa and found that all life stages were hyperosmotic in a dilute medium (15%o) : adults were isosmotic and juveniles \\ ere hypoosmotic in 45%c ', and all life stages were hypoosmotic in 30/e sea water. Cuzon and Ceccaldi (1973) determined that starvation affects the hydration levels of C. crangon and that percentage water of muscle varied from 76.1 1.4% to 77.7 0.5% over the four-week study. Adequacy of foods and their utilization are revealed by several indicies in C. septemspinosa. Growth of the shrimp on a variety of diets over a period of weeks has been discussed by Wilcox and Jeffries (1974). Freshly prepared foods (e.g., the clam Mercenaria lucrcenaria, the brine shrimp Artcmia salina, hard-boiled egg) promoted better growth than dried foods (e.g., Mercenaria, Artcmia, Crangon, fish meal, copepods). This difference in growth was attributed to loss of olfactory attractants upon drying. In this study, the effects of nutrition on hydration in C. septemspinosa were determined. 1 Present address : Florida Power and Light Company, Environmental Department, P.O. Box 013100, Miami, Florida 33101. 522
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