Uncorrected Proof ARTICLE IN PRESS Comparative Biochemistry and Physiology Part A xx (2002) xxx–xxx 1095-6433/02/$ - see front matter  2002 Published by Elsevier Science Inc. PII: S1095-6433 Ž 02 . 00202-7 2 Review 3 4 Calcium balance in crustaceans: nutritional aspects of physiological 5 regulation 6 7 F.P. Zanotto *, M.G. Wheatly a, b 8 9 Department of Physiology, Biosciences Institute, University of Sao Paulo, 05508-900 Sao Paulo, SP, Brazil a ˜ 10 Department of Biological Sciences, Wright State University, Dayton, OH 45435, USA b 11 12 Received 5 January 2002; received in revised form 10 April 2002; accepted 10 April 2002 13 22 23 Abstract 24 25 Calcium homeostasis in crustaceans is influenced by their natural molting cycle that periodically requires replacement 26 of the calcified exoskeleton in order for growth to occur. Whole body Ca balance transitions from intermolt (zero net 27 flux) to premolt (net efflux) and postmolt (net influx at the rate of 2 mmol kg h ). As such, molting provides a y1 y1 28 convenient model to study up- and down-regulation of epithelial Ca transporting proteins (such as Ca pumps and 29 exchangers), the genes that encode them, and the steroid hormone (ecdysone) that putatively regulates the genes. Species 30 residing in either freshwater or in terrestrial environments are more limited in their Ca availability than are marine 31 species. Further the advance towards terrestriality is accompanied by decreased reliance upon branchial Ca uptake and 32 increased reliance upon digestive uptake. This review will correlate Ca handling strategies with environment in semi- 33 terrestrial and terrestrial crabs through examining environmental sources of Ca uptake. Ca homeostasis will also be 34 discussed at the whole animal level, cellular, subcellular and molecular levels of regulation. 35  2002 Published by Elsevier Science Inc. 36 37 Keywords: Environmental calcium; Purified diets; Calcium homeostasis; Calcium regulation; Calcium transporters 51 53 1. Introduction 54 While whole animal Ca homeostasis has been 55 well reviewed in crustaceans (Ahearn and Zhuang, 56 1996; Wheatly, 1996, 1999; Flik et al., 1999; 57 Ahearn et al., 1999; Wheatly et al., 2001), the role 58 of the digestive epithelium has never been com- 1225 1226 Abbreviations: IC, intracellular; EC, extracellular; SW, sea- 1227 water; FW, freshwater; PMCA, plasma membrane Ca- 1228 ATPase; NCX, Na yCa exchanger; BBMV, brush border 2q q 2q 1229 membrane vesicles; BLMV, basolateral membrane vesicles;IV, 1230 intravesicular; EV, extravesicular; IOV, inside out vesicle; 1231 ROV, right side out vesicle; NHE, Na yH exchanger; ER, q q 1232 endoplasmic reticulum; SR, sarcoplasmic reticulum; SERCA, 1233 sarcoyendoplasmic reticulum Ca ATPase; mAb, monoclonal 2q 1234 antibody; CT, calcitonin. 1235 *Corresponding author. Tel.: q55-11-3091-7503; fax: q55- 1236 11-3031-50-28. 1237 E-mail address: fzanotto@usp.br (F.P. Zanotto). 59 prehensively reviewed, largely because it is 60 believed to play a secondary role to other ‘primary’ 61 transporting epithelia namely gills and antennal 62 gland (kidney). At the same time, the existing 63 model for transcellular Ca transport has been 64 largely developed from in vitro studies of vesicles 65 prepared from hepatopancreas, which is a large 66 and accessible organ (15 g in lobster, Ahearn et 67 al., 1987; 2 g in crayfish, Wheatly et al., 1998). 68 Further, the role of feeding in crustacean Ca intake 69 is believed to increase with the advance towards 70 terrestriality and increased dependence upon die- 71 tary Ca. This justifies a critical review of the role 72 of the digestive tract in Ca balance during routine 73 feeding (intermolt) in addition to the unique role 74 it plays in storage and remobilization of Ca around 75 ecdysis (non-feeding stages).