0000000000037915
AUTHOR
François Graf
Unusual basement layer in the midgut of gammaridean Niphargus virei Chevreux (Crustacea, Amphipoda).
The basement membrane of the midgut and posterior caeca epithelium in the gammaridean amphipod Niphargus virei Chevreux, 1896 is made of an unusual structure. This basal lamina, properly called “basal layer”, shows a dense sheet formed by a system of dense hexagonal plates connected by thin filaments. Histochemical studies and enzymatic reactions lead to the conclusion that these structures are proteinaceous, without collagenous protein, and embedded in a neutral polysaccharide matrix. The possible mechanical significance of these mesenteric structures is discussed.
Carbonic anhydrase activity in a calcium-mobilizing epithelium of the crustacean Orchestia cavimana during molting
We investigated the involvement of the enzyme, carbonic anhydrase, in the calcification-decalcification processes occurring in the posterior caeca of the midgut of the terrestrial crustacean, Orchestia cavimana, before and after exuviation. This enzyme was ultrahistochemically localized throughout the membranes of the caecal epithelium as well as extracellularly, i.e., within pre-exuvial calcareous concretions and postexuvial calcified spherules. During the molt cycle, the pattern of carbonic anhydrase activity in the posterior caeca was correlated with the calcium content at this level. Acetazolamide treatment in vivo inhibited about 50% of the calcium uptake during both pre-exuvial secret…
Fine Determination of the Molt Cycle Stages in Orchestia cavimana Heller (Crustacea: Amphipoda)
ABSTRACT The successive stages of the molt cycle of the terrestrial crustacean amphipod Orchestia cavimana are finely described and illustrated in order to give precise reference marks for experimental, physiological, and biochemical studies. The method of determination, very rapid and easy, is based upon the observation of the morphogenesis of the dactylopodite and the propodite from the third pereiopod. The events of the early morphogenesis of the claw from the dactylopodite divide the intermolt period C into four stages. The formation of spines and the secretion of the epicuticle and then the procuticle at the level of the propodite divide the premolt period into seven stages. The entire…
Variations in haemolymph ionized calcium concentrations in the crustacean Orchestia cavimana during a moult cycle
Abstract Measurements of ionized calcium concentration in the haemolymph of the semi-terrestrial crustacean Orchestia cavimana were taken during the 14 successive moulting stages by ion-selective electrode direct potentiometry on pooled samples. Ionized calcium showed major variations associated with the moult cycle. Titres were low and relatively stable in intermoult and early premoult, then progressively increased during mid and late premoult to reach maximal values just at exuviation, and rapidly fell down during the postmoult. The variations of the ionized fraction showed a close correlation with those of the calcaemia (= total fraction), suggesting the presence of efficient haemolympha…
Variations of vitamin D-like reactivity in the crustacean Orchestia cavimana during the molt cycle
An investigation into vitamin D-like molecules has been performed on whole extracts of the terrestrial amphipod Orchestia cavimana, using a sensitive nonequilibrium assay employing 1,25-(OH)2 D receptor from calf thymus. Relatively large amounts of these secosteroid-like molecules were observed and they varied in concentration according to the stages of the molt cycle. The amplitude of these variations reaches a ratio of about 40 from the minimum in premolt to the intermolt sharp peak.
Orchestin, a calcium-binding phosphoprotein, is a matrix component of two successive transitory calcified biomineralizations cyclically elaborated by a terrestrial crustacean.
Orchestia cavimana is a crustacean that cyclically replaces its calcified cuticle during molting cycles in order to grow. Its terrestrial way of life requires storage of calcium during each premolt period, as calcareous concretions, in tubular diverticula of the midgut. During the postmolt period the stored calcium is reabsorbed and is translocated through the storage organ epithelium as calcified small spherules. In a previous study, we sequenced and characterized a remarkable component of the organic matrix of the premolt storage structures, Orchestin, which is a calcium-binding phosphoprotein. In this paper, we analyzed the spatiotemporal expression of the orchestin gene by Northern blot…