. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Ca+ +-DEPENDENCE OF PIGMENT MIGRATION 365 Taylor, 1987). In the red integumental chromatosomes of Macrobrachium potiuna perfused with mM Ca++, A23187 (10~7 to 10~4 M) has a concentration-dependent aggregating effect, reversible by 10~x M a-PDH (Britto et ai, 1990). These various data demonstrate that pigment aggregation in the caridean shrimps and pigment dispersion in the brachyuran crabs can be brought about by changes in intra- cellular Ca+ + concentrations. The effector pathways of such concentration changes, whether
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Ca+ +-DEPENDENCE OF PIGMENT MIGRATION 365 Taylor, 1987). In the red integumental chromatosomes of Macrobrachium potiuna perfused with mM Ca++, A23187 (10~7 to 10~4 M) has a concentration-dependent aggregating effect, reversible by 10~x M a-PDH (Britto et ai, 1990). These various data demonstrate that pigment aggregation in the caridean shrimps and pigment dispersion in the brachyuran crabs can be brought about by changes in intra- cellular Ca+ + concentrations. The effector pathways of such concentration changes, whether increased by signal transduction or after A23187. are poorly known. Based on rightward shifting of the PCH dose-response curve by in- hibitors of intracellular effectors, Nery et al. (1997) have suggested that pigment aggregation in M. potiuna red in- tegumental chromatosomes may involve an inositol- trisphosphate-like cascade coupled to protein phosphatase 1 activation. This latter effect may down-regulate effector protein phosphorylation via the cyclic AMP-protein kinase A signaling pathway (Nery and Castrucci, 1997), given that increased intracellular cyclic AMP also induces pigment dispersion in caridean shrimps (Fingerman, 1969; Lambert and Fingerman, 1978; Nery et ai. 1998). Clearly, possible convergence or cross-talk between the Ca++-signaling and cyclic nucleotide-signaling pathways in crustacean pigment translocation mechanisms requires further investigation. Acknowledgments This study was financed by research grants to JCM (FAPESP 94/5981-7; CNPq 400517/95/7, 303282/84-3) and a postgraduate scholarship to MRR (FAPESP 94/ 4151-0). Velocity Aggregat. g> a Extracellular Ca** concentration. M Figure 6. Mean (±SEM, n > 7) maximum pigment aggregation velocities (R2 = ) and degree of maximum aggregation increase as a concentration-effect function (R2 = ) of increasing extracellular free [Ca"1"*] and are positively correlated (Pearson correlation. R =
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