Jessore University of Science & Technology

About: Jessore University of Science & Technology is a based out in . It is known for research contribution in the topics: Adsorption & Population. The organization has 811 authors who have published 974 publications receiving 10471 citations.

Ovarian Development of the Mud Crab Scylla paramamosain in a Tropical Mangrove Swamps, Thailand

Abstract: The present study describes the ovarian development stages of the mud crab, Scylla paramamosain from Pak Phanang mangrove swamps, Thailand. Samples were taken from local fishermen between June 2006 and December 2007. Ovarian development was determined based on both morphological appearance and histological observation . Ovarian development was classified into five stages: proliferation (stage I), previtellogenesis (II), primary vitellogenesis (III), secondary vitellogenesis (IV) and tertiary vitellogenesis (V). The formation of vacuolated globules is the initiation of primary vitellogenesis and primary growth. The follicle cells were found around the periphery of the lobes, among the groups of oogonia and oocytes. The follicle cells were hardly visible at the secondary and tertiary vitellogenesis stages. Yolk granules occurred in the primary vitellogenesis stage and are first initiated in the inner part of the oocytes, then gradually concentrated to the periphery of the cytoplasm. The study revealed that the initiation of vitellogenesis could be identified by external observation of the ovary but could not indicate precisely. Keywords: Ovarian maturation; Ovarian histology; Mud crab; Scylla paramamosain . © 2010 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v2i2.3543 J. Sci. Res. 2 (2), 380-389 (2010)

Geochemical characteristics of modern river sediments in Myanmar and Thailand: Implications for provenance and weathering

Abstract: The elemental composition of organic matter and the major and trace element compositions of stream sediments from Myanmar (Ayeyarwady and Sittaung rivers) and Thailand (Mekong and Chao Phraya rivers, and their tributaries) were determined to examine their distributions, provenance, and chemical weathering processes. Higher total organic carbon (TOC) and total nitrogen (TN) contents in the finer grained sediments indicate hydrodynamic energy may control their distributions. TOC/TN ratios indicate inputs of both aquatic macrophyte and higher vascular plant material to the river sediments. The major element abundances of the sediments are characterized by predominance of SiO2 in coarser fractions and a marked negative correlation with Al2O3, representing primary grain size primarily control on SiO2 content. Marked depletion of most labile elements (Na2O, CaO, K2O, Ba and Sr) relative to UCC (upper continental crust), indicate destruction of feldspar during chemical weathering in the source area or during transport. However, enrichment of some high field strength elements (Zr, Th, Ce and Y) relative to UCC and higher Zr/Sc ratios indicate moderate concentration of resistant heavy minerals in finer-grained samples. Discriminant diagrams and immobile trace element characteristics indicate that the Mekong, and Chao Phraya river sediments were largely derived from felsic sources with compositions close to typical rhyolite, dacite/granodiorite, UCC, I- and S-type granites. Relative enrichment of ferromagnesian elements (e.g. MgO, Cr, Ni) and high Cr/V and low Y/Ni ratios in Ayeyarwady and Sittaung sediments indicate the presence of a mafic or ultramafic component in their sources. The ICV (Index of Compositional Variability), CIA (Chemical Index of Alteration), PIA (Plagioclase Index of Alteration), αAl, Rb/Sr and K2O/Rb ratios indicate that the Ayeyarwady and Sittaung sediments record low to moderate degrees of chemical weathering in their source, compared to moderate to intense chemical weathering in the Mekong and Chao Phraya river basins. These results are compatible with existing major ion data for river waters collected at the same locations.