Roles of crustacean hyperglycaemic hormone in ionic and metabolic homeostasis in the Christmas Island Blue crabDiscoplax celeste

Abstract

SUMMARYThere is a growing body of evidence implicating the involvement of crustacean hyperglycaemic hormone (CHH) in ionic homeostasis in decapod crustaceans. However, little is known regarding hormonally influenced osmoregulatory processes in terrestrial decapods. As many terrestrial decapods experience opposing seasonal demands upon ionoregulatory physiologies, we reasoned that these would make interesting models in which to study the effect of CHH upon these phenomena. In particular, those (tropical) species that also undergo seasonal migrations might be especially informative, as we know relatively little regarding the nature of CHHs in terrestrial decapods, and hormonally mediated responses to seasonal changes in metabolic demands might also be superimposed or otherwise integrated with those associated with ionic homeostasis. Using Discoplax celeste as a model crab that experiences seasonal extremes in water availability, and exhibits diurnal and migratory activity patterns, we identified two CHHs in the sinus gland. We biochemically characterised (cDNA cloning) one CHH and functionally characterised (in terms of dose-dependent hyperglycaemic responses and glucose-dependent negative feedback loops) both CHHs. Whole-animal in situ branchial chamber 22 NaCl perfusion experiments showed that injection of both CHHs increased gill Na + uptake in a seasonally dependent manner, and 51Cr-EDTA clearance experiments demonstrated that CHH increased urine production by the antennal gland. Seasonal and salinity-dependent differences in haemolymph CHH titre further implicated CHH in osmoregulatory processes. Intriguingly, CHH appeared to have no effect on gill Na + /K + -ATPase or V-ATPase activity, suggesting unknown mechanisms of this hormoneʼs action on Na + transport across gill epithelia.Supplementary material available online at

Structure-based functional study of a peptide of an ecdysozoan superfamily: reveling a common molecular architecture and receptor-interacting residues

“…In addition, the molecular target(s) on which CHH acts to achieve its osmo-ionic regulation were however not directly addressed by these studies, although it has been suggested that increase in energy availability as a result of CHH-stimulated glycogen mobilization is a probable mode of action (42), a suggestion compatible with the data showing that exposing the shore crabs C. maenas to dilute seawater increased the levels of glucose in the gills and hemolymph CHH (44). In this regard, it is relevant to note that in the Christmas Island blue crab Discoplax celeste, 2 CHHs were found effective in stimulating Na + transport across the gill epithelia in a seasonally dependent manner but have no effect on gill Na + /K + -ATPase or V-ATPase activity (45). On the other hand, Pt-CHH2, a CHH-L peptide of the crab Portunus trituberculatus, was suggested to be a regulator for gill Na + /K + -ATPase and carbonic anhydrase activity as CHH dsRNA treatment that decreased Pt-CHH2 transcript levels significantly reduced the enzyme activity in the gills (46).…”

“…Asp 12 in Sco-CHH and Asn 13 in Pej-MIH have been shown to be functionally important (4,9). Similarly, there are 2 negatively charged residue (Glu 45 and Asp 69 ) in Sco-CHH-L that are characteristically absent in Pej-MIH ( Fig. 9).…”

“…6), which is brought towards each other in the structure of Sco-CHH-L. Thus, Ile 71 , Gly 73 , Glu 45 and Asp 69 are on a continuous stretch of the surface, with the 2 N-terminal end residues (Ile 2 or Phe 3 ) being located nearby ( Fig. 9).…”

“…6; Liu et al, 2015). In addition, Glu 45 , located in π4, occupies a conserved position where among CHH-L peptides a negatively charged residue (Glu or Asp) is present ( Fig. 6; Liu et al, 2015) and 2 negatively residues (Glu 62 and Glu 63 ) located in α5-helix were also chosen for alanine substitution.…”

In silico Neuropeptidome of Female Macrobrachium rosenbergii Based on Transcriptome and Peptide Mining of Eyestalk, Central Nervous System and Ovary

“…We found that both isoforms are present within eyestalk and CNS transcriptomes. Despite inducing hyperglycemia, CHH is pleiotropic and can also exhibit an osmoregulartory role [ 121 ] as well as an inhibitory role for molting and methyl farnesoate synthesis [ 122 ]. CHH genes and associated peptides appear to be polymorphic, where at least two isoforms could be present in a single species [ 123 ].…”