Stable-isotope and amino acid profiles of the New Zealand giant Pliocene oyster Crussostreu ingens

Mitchell, L., Curry, G.B. & Fallick, A.E. 1995 11 30: Stable-isotope and amino acid profiles of the New Zealand giant Pliocene oyster Crassostrea ingens .
Oxygen and carbon stable-isotope profiles and intracrystalline amino acid profiles (free and total) were determined for the New Zealand giant Pliocene oyster Crassostrea ingens by sampling annual growth increments along a sagittal section. These profiles reflect both ontogenetic and environmental change over the life-time of the oyster (approximately 20 years). There is a gradual increase in δ¹⁸O from the umbo towards the shell margin and a subsequent levelling-off about halfway along the shell. This pattern probably reflects a decrease in the growth rate of the oyster rather than a temperature effect. The δ¹³C profile initially increases sharply at the umbo and then gradually decreases towards the shell margin. This may be due to kinetic or metabolic effects associated with the development of a fast-growing juvenile into a slower-growing, sexually mature adult, or it may be due to the influence of ¹³C-depleted carbon derived from the oxidation of organic matter in the surrounding sediment. The amino acid profile reveals a gradual decrease in abundance from the umbo to the shell margin, indicative of a progressive increase in the relative amounts of inorganic carbonate to protein over the life of the oyster, that may also be a consequence of decreasing growth rate. Glycine and alanine are the two most common amino acids in both the free and total amino acid profiles: free (i.e. naturally hydrolysed) amino acids account for about three quarters of the total amino acids present. □ Biogeochemistiy, stable isotopes, amino acids, environment, ontogeny .     

Mature Raphid and Raphid Idioblast Structure in Plants of the Edible Aroid Genera Colocasia, Alocasia, and Xanthosoma

Mature raphid idioblasts examined in this study appear to consistof a bundle of raphid crystals contained within a polysaccharidematrix. The cytoplasm consists of a thin parietal layer withfew discernible organelles. These cells appear to be true idioblasts,and no intercellular connections were observed between thesecells and adjacent parenchyma cells. Dissolution of the middlelamella occurs in Colocasia and to some extent in Xanthosoma.The mechanism of crystal release in the five species studiedis the same, e.g. a swelling of a polysaccharide material whichbreaks the idioblast wall and forces the release of the raphides.In Colocasia this results in a forceful ejection with releaseof a relatively few number of crystals at any one time. Xanthosomaand Alocasia do not exhibit a forceful ejection of their crystals,but a less forceful release of a crystal mass which then disassociatesto free the individual crystals. The raphides differ in structureand size, however, they have three structural features in common.First, the crystals have two distinct points, one tapering toan elongate point, the other abruptly pointed. Second, the crystalshave surface barbs with tips oriented away from the taperingpoint. And third, deep grooves are present along the lengthof the crystals. The possible relationship between raphid structureand the acrid nature of the idioblasts is discussed.