Calcium movements during pigment aggregation in freshwater shrimp chromatophores.
Pigment granule migration within crustacean chromatophores provides an excellent model with which to investigate cytoplasmic movements, given the antagonistic, neurosecretory peptide regulation of granule translocation, and the absence of innervation in these large, brightly colored cells. Red pigment-concentrating hormone (RPCH) induces pigment aggregation in shrimp chromatophores via an increase in intracellular Ca2+; however, how this increase is brought about is not known. To examine the putative Ca2+ movements leading to pigment translocation in red, ovarian chromatophores of the freshwater shrimp, Macrobrachium olfersii, this study manipulates intra- and extracellular Ca2+ employing ER Ca2+-ATPase inhibitors, ryanodine-sensitive, ER Ca2+ channel blockers, and EDTA/EGTA-buffered A23187/Ca2+-containing salines. Our findings reveal that during pigment aggregation, cytosolic Ca2+ apparently increases from an intracellular source, the abundant SER, loaded by the SERCA and released through ryanodine-sensitive receptor/channels, triggered by capacitative calcium influx and/or calcium-induced calcium release mechanisms. Aggregation also depends on external calcium, which may modulate RPCH/receptor coupling. Such calcium-regulated pigment movements form the basis of a complex system of chromatic adaptation, which confers selective advantages like camouflage and protection against ultra-violet radiation to this palaemonid shrimp.
Ribeiro
Márcia
M
Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, FMRP, Universidade de São Paulo, Ribeirão Preto, 14040-901 São Paulo, Brazil.
McNamara
John Campbell
JC
D000818:Animals; D002021:Buffers; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D002856:Chromatophores / Q000378:metabolism*; D033364:Decapoda / Q000187:drug effects / Q000378:metabolism*; D004492:Edetic Acid / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005618:Fresh Water; D009068:Movement / Q000187:drug effects; D009842:Oligopeptides / Q000494:pharmacology; D010860:Pigments, Biological / Q000032:analysis / Q000378:metabolism*; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D012965:Sodium Chloride / Q000494:pharmacology
D002021:Buffers; D004791:Enzyme Inhibitors; D009842:Oligopeptides; D010860:Pigments, Biological; C022059:red pigment-concentrating hormone; D000001:Calcimycin; D012965:Sodium Chloride; D004533:Egtazic Acid; D004492:Edetic Acid; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D002118:Calcium; D011761:Pyrrolidonecarboxylic Acid