The Larval Shell of Some Prosobranch Gastropods

Abstract

Growth of shells of larvae ofNassarius reticulatus(L.) andCrepidula fornicata(L.) reared in the laboratory under constant temperature (14 °C) and illumination (155 lx) occurs by the addition of successive strips secreted at the mantle edge. Growth lines on the embryonic teloconch also indicate intermittent growth; the protoconch secreted by the shell gland has no such lines. There is evidence that growth periods are short and pauses separating them prolonged. The diameter of the older whorls of the shells of these and six other species examined increase with the volume of the viscera. This change in diameter is made possible by the flexibility of the organic matrix, the funda-mental constituent of the shell. The matrix, secreted as fibres at the mantle edge, forms sheets, and provides sites for the deposition of calcareous concretions; at metamorphosis the concretions apparently initiate the formation of crystals. The concretions also sculpture the surface of the shell producing a pattern sufficiently conspicuous to allow identification of some species with the aid of only the stereomicroscope. For example, large concretions form longitudinal rows over the protoconch and teloconch ofLittorina neritoides(L.) and smaller ones combine to form a more decorative pattern inRissoa sarsiLoven. In other species details of the surface design require a scanning electron micro-scope. Interspecific differences in the arrangement of concretions may be traceable to differences in the pallial glands which secrete the matrix.

Validation of a Short-Term Toxicity Test Endpoint by Comparison With Longer-Term Effects on Larval Red Abalone Haliotis Rufescens

“…The concretions are not apparent in the newly secreted viscous fibers that comprise the secretion from the edge of the mantle skirt. The binding sites are determined by differences in the organic matrix, which apparently induce the formation of crystal nuclei and to some extent determine the ultimate structural organization of the shell [26]. The presence or absence of calcium carbonate concretions and the fine-scale microstructure of the larval shell were investigated using SEM.…”

Taking Advantage of Disorder: Amorphous Calcium Carbonate and Its Roles in Biomineralization

“…In the former case mineralization takes place in a multicellular vesicle (syncitium), [61] whereas in the latter it is in an extracellular matrix. [62] In the sea urchin larva the ACC is not known to be formed in the syncitium, but in small intracellular vesicles located in the adjacent cells. [59] It is presumably transported into the syncitium.…”

The problem of similarity: analysis of repeated patterns of microsculpture on gastropod larval shells

“…It is well established that the initial cup-shaped larval shell is secreted by a small group of cells in the dorsal ectoderm, at the lip of the "shell gland" or "shellfield invagination," prior to differentiation of the mantle and fluid-filled extrapallial space. Furthermore, the initial "shell" or "pellicle" is wholly organic (Kniprath 1979), or with insufficient amounts of calcium carbonate to rigidify it (Fretter & Pilkington 1971;Collin & Voltzow 1998).…”