title: A morphological and electron-microprobe study of the inorganic composition of the mineralized secretory products of the calciferous gland and chloragogenous.
abstract: The two pairs of lobes of the calciferous gland if the earthworm Lumbricus terrestris are specialized oesophageal diverticulae that secrete spherites ranging from 0.5 - 7.0 micrometers in diameter. Correlative transmission and scanning electron microscopy indicated that the spherites (which are predominantly CaCO3) are formed extracellularly in distinctive bays bounded by secretory-cell processes, and are mobilized anteriorly from the gland lumina to the lumen of a non-secretory pouch, where the majority coalesce and undergo phase transformation to concretions 0.5 - 1.0 mm in diameter consisting of a mass of cuboidal crystals with facets up to 40 micrometers. The distribution of Sr(0.1 ml 5% SrCl2 injected into the posterior coelomic cavity) was monitored in the mineralized secretory products of the calciferous glands by X-ray microanalysis of 10 micrometers - thick air-dried cryostat sections in a SEM. Strontium was not detected in chloragosomes at 2h and 24h post-injection. Strontium was transported anteriorly and specifically incorporated into gland spherites (detectable within 2h). This technique of Sr localization afforded sufficient structural and analytical resolutions to provide a confirmation of the sequence of extracellular changes in the gland/pouch system. In addition we were able to distinguish a population of growing spherites from the vast majority of mature spherites; size alone was a singularly poor indication of spherite growth. The major element constituents of the chloragosomes were P, Ca and Zn (Ca: P ranging from 0.4 to 1.0; Zn: P from about 0.05 to 0.45). Analysis of individual spherites showed that Ca was probably bound to P or P-containing matrix components, whilst Zn was probably linked to one or more different but unknown constituents.
mesh_terms: D000818:Animals; D002118:Calcium / Q000032:analysis*; D003594:Cytoplasmic Granules / Q000032:analysis*; D004577:Electron Probe Microanalysis; D005088:Exocrine Glands / Q000032:analysis / Q000648:ultrastructure; D009835:Oligochaeta / Q000032:analysis* / Q000648:ultrastructure; D010758:Phosphorus / Q000032:analysis; D013324:Strontium / Q000032:analysis*; D015032:Zinc / Q000032:analysis
chemical_list: D010758:Phosphorus; D015032:Zinc; D002118:Calcium; D013324:Strontium