Ultrastructure and Cytochemistry of Periostracum and Mantle Edge ofBiomphalaria glabrata(Gastropoda, Basommatophora)

Risk assessment of iron oxide nanoparticles in an aquatic ecosystem: A case study on Biomphalaria glabrata

Iron oxide nanoparticles (IONPs) have been applied in several sectors in the environmental field, such as aquatic nanoremediation, due to their unique superparamagnetic and nanospecific properties. However, the knowledge of chronic toxicity of IONPs on aquatic invertebrate remains limited. Thus, the present study aimed to analyze the chronic toxicity of gluconic acid-functionalized IONPs (GLA-IONPs) and their dissolved counterpart (FeCl₃) to freshwater snail Biomphalaria glabrata. GLA-IONPs were synthesized and characterized by multiple techniques, and the snails were exposed to both Fe forms at environmentally relevant concentrations (1.0-15.6 mg L^-1) for 28 days. The bioaccumulation, mortality rate, behavior impairments, morphological alterations, fecundity and fertility of snails were analyzed. Results showed that GLA-IONPs induced high iron bioaccumulation in the entire soft tissue portion. Chronic exposure to GLA-IONP increased the behavioral impairments of snails compared to iron ions and control groups. Both Fe forms reduced the fecundity, while the mortality and reduced fertility were observed only after the exposure to GLA-IONPs at 15.6 mg L^-1. Overall results indicated the behavioral impairments and reproductive toxicity associated, possibly, to bioaccumulation of GLA-IONPs in the B. glabrata. These results can be useful for the development of eco-friendly nanotechnologies.

Connecting pattern to process: Growth of spiral shell sculpture in the gastropod Nucella ostrina (Muricidae: Ocenebrinae)

Shell morphology is a well-suited and underused system to examine the development of novel forms. The three-dimensional structure produced (the shell) is separate from the largely two-dimensional tissue that secretes it (the mantle), allowing us to disentangle the pattern from the process. Despite knowing a great deal about the mechanics of shell secretion (process), and the variety of shell shapes that exist (pattern), no effort has been made to understand how the mantle changes to produce different shell shapes. We investigated this question in the dimorphic snail Nucella ostrina, which exhibits both smooth and ribbed shells to determine how ribs are formed by the mantle. Rib thickenings are produced only in the outer calcitic shell layer and secreted by the distal Outer Mantle Epithelium (OME) with increased acid phosphatase activity. The evenly thick inner aragonitic layers are secreted by the proximal OME which expresses acid phosphatase. Here we show that locally thicker ribs in N. ostrina are produced by changing the dimensions of the distal OME: elongation in the direction of growth and increased cell height. This should increase the amount of shell material secreted, producing locally thicker shell (ribs). Preliminary evidence suggests this mechanism may be widespread in gastropods.

The major soluble 19.6 kDa protein of the organic shell matrix of the freshwater snail Biomphalaria glabrata is an N-glycosylated dermatopontin

The major Biomphalaria glabrata shell matrix protein of 19.6 kDa was isolated by preparative electrophoresis and sequenced. The sequence of 148 amino acids showed 32% sequence identity to mammalian dermatopontin sequences and 34-37% identity to two invertebrate dermatopontins described previously. A unique feature of the shell matrix dermatopontin was the presence of a single N-glycosylation consensus sequence, the asparagine of which was completely modified with a pentasaccharide. Sequence analysis of this short N-glycan by mass spectrometry and carbohydrate composition analysis indicated that it was the ubiquitous N-glycan core oligosaccharide with the exception that the terminal mannoses were 3-O-methylated. Dermatopontin is widespread in mammalian extracellular matrices, including the matrix of biominerals such as bone and teeth. Its occurrence in an invertebrate biomineral indicates that such phylogenetically distant biomineral-forming systems as vertebrate bone and mollusk shell share components which have undergone surprisingly few changes during a long evolution.

Calcium carbonate modifications in the mineralized shell of the freshwater snail Biomphalaria glabrata

The mineralized shell (consisting of calcium carbonate) of the tropical freshwater snail Biomphalaria glabrata was investigated with high resolution synchrotron X-ray powder diffractometry and X-ray absorption spectroscopy (EXAFS). Parts from different locations of the snail shell were taken from animals of different age grown under various keeping conditions. Additionally, eggs with ages of 60, 72, 120, and 140 hours were examined. Traces of aragonite were found as first crystalline phase in 120 h old eggs, however, Ca K-edge EXAFS indicated the presence of aragonitic structures already in the X-ray amorphous sample of 72 h age. The main component of the shell of adult animals was aragonite in all cases, but in some cases minor amounts of vaterite (below 1.5%) are formed. The content of vaterite is generally low in the oldest part of the shell (the center) and increases towards the mineralizing zone (the shell margin). In juvenile snails, almost no vaterite was detectable in any part of the shell.

Influence of microgravity on crystal formation in biomineralization

Biomineralized tissues are widespread in animals. They are essential elements in skeletons and in statocysts. The function of both can only be understood with respect to gravitational force, which has always been present. Therefore, it is not astonishing to identify microgravity as a factor influencing biomineralization, normally resulting in the reduction of biomineralized materials. All known biominerals are composite materials, in which the organic matrix and the inorganic materials, organized in crystals, interact. If, during remodeling and turnover processes under microgravity, a defective organization of these crystals occurs, a reduction in biomineralized materials could be the result. To understand the influence of microgravity on the formation of biocrystals, we studied the shell-building process of the snail Biomphalaria glabrata as a model system. We show that, under microgravity (space shuttle flights STS-89 and STS-90), shell material is built in a regular way in both adult snails and snail embryos during the beginning of shell development. Microgravity does not influence crystal formation. Because gravity has constantly influenced evolution, the organization of biominerals with densities near 3 must have gained independence from gravitational forces, possibly early in evolution.