Calcium homeostasis in crustacea: The evolving role of branchial, renal, digestive and hypodermal epithelia

Abstract

Crustaceans serve as an ideal model for the study of calcium homeostasis due to their natural molting cycle. Demineralization and remineralization of the calcified cuticle is accompanied by bidirectional Ca transfer across the primary Ca transporting epithelia: gills, antennal gland (kidney), digestive system, and cuticular hypodermis. The review will demonstrate how a continuum of crustaceans can be used as a paradigm for the evolution of Ca transport mechanisms. Generally speaking, aquatic crustaceans rely primarily on branchial Ca uptake and accordingly are affected by water Ca content; terrestrial crustaceans rely on intake of dietary Ca across the digestive epithelium. Synchrony of mineralization at the cuticle vs. storage sites will be presented. Physiological and behavioral adaptations have evolved to optimize Ca balance during the molting cycle in different Ca environments. Intracellular Ca regulation reveals common mechanisms of apical and basolateral membrane transport as well as intracellular sequestration. Regulation of cell Ca concentration will be discussed in intermolt and during periods of the molting cycle when transepithelial Ca flux is significantly elevated. Molecular characterization of the sarco‐/endoplasmic reticular Ca pump in aquatic species reveals the presence of two isoforms that originate from a single gene. This gene is differentially expressed during the molting cycle. Gene expression may be regulated by a suite of hormones including ecdysone, calcitonin, and vitamin D. Perspectives for future research are presented. J. Exp. Zool. 283:620–640, 1999. © 1999 Wiley‐Liss, Inc.

Impacts of temperature and acidification on larval calcium incorporation of the spider crab Hyas araneus from different latitudes (54° vs. 79°N)

“…Overall, the comparison of both populations under 380 ppm CO 2 revealed that Svalbard Megalopae during the first 14 days at 3°C could not set their calcification rate to the same level as Megalopae from Helgoland at the same temperature. Possibly, enzymes and transporters supporting the active influx of calcium ions and their assembly into the chitin layer (Giraud 1981;Neufeld and Cameron 1993;Wheatly 1999) differ in their expression or activity between both populations. Alternatively, energy allocation to calcification may be less in the population from Svalbard and thereby delay the accumulation of carbonates.…”

“…For mineralizing the matrix of the cuticle, calcium is transported to the extracellular space through the apical membrane by Ca 2? -ATPase (Wheatly 1999 (Neufeld and Cameron 1993;Wheatly 1999). Here, calcium and carbonate combine to form CaCO 3 (Cameron 1985a, b), which is precipitated to the chitin-protein fibres of the exo-and epicuticle (Travis 1955).…”

Excretory calcinosis: a new fatal disease of wild American lobsters Homarus americanus

“…The calcium budget of lobsters is highly dynamic, and is tightly coupled to their moult cycle, growth and to environmental conditions (Zhuang & Ahearn 1996, 1998, Klein & Ahearn 1999, Wheatly 1999, Flik & Haond 2000. These mechanisms are normally used to regulate intra-and extracellular calcium concentrations and to rapidly translocate calcium across epithelia during the moulting cycle (Wheatly 1999).…”

“…These mechanisms are normally used to regulate intra-and extracellular calcium concentrations and to rapidly translocate calcium across epithelia during the moulting cycle (Wheatly 1999). During the cycle, mineral calcium is usually stored in intracellular phosphate-storage granules and in extracellular gastroliths in the stomach , Wheatly 1999.…”

“…Epithelia known to have an abundance of calcium-regulation channels occur in the gills, the hepatopancreas, the antennal glands and the shell epithelium. While there are common types of calcium channels between these epithelia (such as those in the basolateral membranes: Ahearn et al 1999), it has been noted that there may be tissuespecific channels and discrete genetic regulation mechanisms, the exact nature of which has not yet been determined in vivo (Wheatly 1999). Differential distribution of different calcium-regulation channels may, in part, explain the distribution of calculi in lobster tissues.…”