Search

The microstructures of the carapaces of the spider crabs Schizophrys dahlak and Hyastenus hilgendorfi were examined under both scanning and transmission electron microscopes. Image analyses of the cross-sectioned carapaces showed that both species have a hierarchical microstructure with three well-defined layers. The two innermost layers (exocuticle and endocuticle) consist of stacked fibers arranged in a twisted plywood fashion producing a "Bouligand structure". They have a similar structure but different thicknesses and height of the stacks. The cuticles are inter-stitched with pore canals of varying width between the studied species, running transversely to the layered structure. This variation in the width of the pore canals in the two species seems to be proportional to the size of the carapace and its surface area. [ABSTRACT FROM AUTHOR]

The present study is an approach to investigate the chromosomal pattern of Biomphalaria alexandrina snails. This may be useful for breaking the hostparasite relationship, which is very specific and dependable on the genetic (chromosomal) status of these hosts. Freshwater snails are essential for the transmission of schistosomiasis by acting as intermediate hosts for the diseasecausing parasite. The objective of this study clarifies the four meiotic divisions that begin with Interphase, prophase, metaphase, and anaphase by Transmission Electron Microscope (TEM) and measuring the lengths of chromosomes by Scanning Electron Microscope (SEM). Results showed the number of the chromosomes of B. alexandrina snails N=18, 2N=36 including 4 types of chromosomes, 5 metacentric pairs, 4 submetacentric pairs, 3 acrocentric pairs, and 6 telocentric pairs chromosomes, they were arranged in a descending manner according to the total length that between 12-2 µm. Notably, the present work is the first chromosomal study of B. alexandrina snails by using TEM and SEM. So high-resolution SEM has proven to be a useful tool for chromosomal study. [ABSTRACT FROM AUTHOR]