The membranaceous tube which protects the aulophora larva of Pectinaria koreni is elaborated by glands announcing the adult cement glands. Sphaerular secretions, belonging to the single type "heterogenous with membrane", form this tube by expanding in a layer of hollow and flat elements, making up a thin wall. When metamorphosing, some other secretions intervene to build up the adult interstitial cement, but the early spherules soon possess a mineral composition comparable to the adult ones. Three microanalysis methods characterised a main phosphated component, in association with calcium and some magnesium, plus traces of aluminium. These characteristics allow us to compare the make up, structure and chemical composition of the larval sheath with the adult cement, and emphasize an original feature of the aulophora stage of Amphictenidae. |
