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ISSN : 1225-3480
The developmental stage of germ cells during oogenesis can be categorized into six stages with histological features: (1) oogonium, (2) previtellogenic oocyte, (3) initial vitellogenic oocyte, (4) early active vitellogenic oocyte, (5) late active vitellogenic oocyte and (6) ripe oocyte. The size of oocyte, nucleus and nucleolus illustrated the increase tendency but size ratio of nucleolus to nucleus was decreased during oogenesis. During oogenesis the stainability in the cytoplasm of oocyte changes from basophilic to eosinophilic in H-E stain. And egg stalk and outer jelly membrane was developed in the oocyte. These histological changes are seemed to be yolk accumulation in the oocyte and preparation process for spawning.
This study was conducted to find out biological response of the oyster Crassostrea gigas exposed to lead (Pb). Experimental period was four weeks. Experimental groups were composed of one control condition and three lead exposure conditions (0.20, 0.40 and 0.80 mg/L). The results of the study confirmed that lead induces reduction of survival rate and oxygen consumption rate and degeneration of organ structure of the bivalve. Oxygen consumption rate was observed exposure groups lower than control decline by 15%-55%. Histological analysis of organ system illustrated expansion of hemolymph sinus, degeneration of epithelial layer and connective tissue layer of the mantle. Also, epithelial degeneration and disappearance of cilia band are recognized in the gill filament and it was observed disruption of epithelial layer and degeneration of basophilic cell and epithelial cell in the digestive tubules.
Ultrastructural studies of oocyte development and vitellogenesis associated with the follicle cells in female Phacosoma japonicus were investigated by electron microscope observations. Vitelloogenesis in the oocytes occured by way of endogenous autosynthesis and exogenous heterosynthesis: vitellogenesis occurred through a process of endogenous autosynthesis, which involves a combined activity of the Golgi complex, rough endoplasmic reticulum, and mitochondria. However, the process of exogenous heterosynthesis involved endocytotic incorporation of extraovarian precursors into the basal region of the early vitellogenic oocytes. In this study, follicle cells, which attached to the previtellogenic and vitellogenic oocytes, were easily found. In particular, the follicle cells were involved in the development of previtellogenic oocytes by the supply of nutrients, and vitellogenesis in the early and late vitellogenic oocytes by endocytosis of yolk precursors. The functions of follicle cells, which attached to mature oocytes, accumulate reserves of lipid granules and glycogen particles for vitellogesis in the cytoplasm of the follicle cells.
Growth-line analysis was carried out on 80 hard clam (Meretrix petechialis) from the Neolithic Age Eurwang-dong Shell Midden, Incheon, Korea, to determine the seasonality of shellfish collection and site occupation. Growth increments and the marginal index (MI) of the specimens were examined. And then the marginal index was compared to the monthly MI of modern specimens under the assumption that the growth pattern was the same as it is today. MI of the archaeological specimens ranged from 0.12 to 1.55 and was divided into four categories: < 0.63, spring; 0.63-0.76, summer; 0.76-0.89, fall; <TEX>$${\geq}_-0.89$$</TEX>, winter collection. As a result, 57 specimens (71.25%) of 80 specimens represented spring, 8 (10.0%) summer, 3 (3.75%) fall and 12 (15.0%) winter collection. The result indicates that shellfish could be collected year-round at the site with an emphasis on spring. Based on the size distribution of shells and the content of the midden, however, it seems that the midden site was not occupied permanently throughout the year but was used repeatedly but temporally for shellfish gathering and processing.
In the present study, we observed a unique association of the flat oyster, Ostrea denselamellosa obtained from a muddy substrate at Haechang Bay, the south coast of Korea in the spring of 2013. Fossilized or semi-fossilized veneriid clam shells, possibly Ruditapes philippinarum, were found adhering to the umbonal area of the flat oyster valves. This unique association of the flat oyster shells with the fossilized clam shells suggested that the flat oyster larvae utilized the clam shells as substrate during settlement. Since availability of clam shells in the muddy subtidal environment is limited, this unique substrata for the flat oyster larvae may limit recruitment of the flat oysters in the bay.
This study was carried out to determine the optimal water temperature for the embryonic development and laboratory culture of larvae of an intertidal mud snail, Nassarius festivus. The embryos and hatched veliger larvae of N. festivus were incubated at six different temperatures (5, 10, 15, 20, 25 and <TEX>$30^{\circ}C$</TEX>). Developmental time for each stage decreased as water temperature increased. The elapsed time to develop to the veliger larva at 15, 20, 25 and <TEX>$30^{\circ}C$</TEX> was 559, 155, 131 and 103 hrs, respectively. At 5 and <TEX>$10^{\circ}C$</TEX>, embryo developed to veliger larvae but failed to hatch out of the egg capsule. In contrast, all embryos successfully hatched in the temperature range from 15 to <TEX>$30^{\circ}C$</TEX>. The biological minimum temperature during the embryonic development of N. festivus was estimated to be <TEX>$9.5{\pm}0.4^{\circ}C$</TEX>. The cumulative water temperatures for blastula, gastrula and veliger stages were calculated as <TEX>$111{\pm}84$</TEX>, <TEX>$486{\pm}185$</TEX>, <TEX>$1,164{\pm}72^{\circ}C$</TEX>, respectively. Temperature also affected the larval survival. Five days after hatching, more than 84% of larvae survived at all experimental temperatures. However, survival began to decrease after 6 days. It was 0% at <TEX>$30^{\circ}C$</TEX>. Survival of larvae incubated for 8 days was higher at 15 and <TEX>$20^{\circ}C$</TEX> than other experimental temperatures. We therefore suggest that the optimal range of temperature for embryonic development and larval survival of N. festivus is <TEX>$15-20^{\circ}C$</TEX>.
To evaluate the applicability of cellular energy allocation (CEA) in the bivalves as a biomarker for the assessment of environmental contamination, the energy contents and energy consumption in several tissues of the Manila clam, Ruditapes philippinarum were analyzed. The contents of lipid, glucose, protein and electron transport system (ETS) activity in the foot, siphons, gills, and body of R. philippinarum exposed to crude oil-spiked sediments were measured at 1, 2, 4, 7, 10 days after exposure. The reserved energy (energy available, EA) in the lipid, glucose and protein decreased as contamination level and exposure time increased. In contrast, the ETS activity (energy consumed, EC) showed the reverse tendency. The order of available energy contents were foot > siphons > gill > body. Significant differences in both EA and EC were found only at the highest contamination level (58.3 mg TPAHs/kg DW). EA decreased significantly in the foot and gill at 1 day, in the body at 2 and 7 days after exposure. EC increased significantly in the body at 4 days after exposure. CEA showed higher sensitivity to the contamination than EA or EC. Especially, CEA in the foot and body decreased significantly at lower ranges of contamination level (as low as 6.5 mg TPAHs/kg DW) during 1 to 7 days after exposure. The CEA is more useful than EA or EC alone for the assessment of sediment contamination at lower level that acute toxicity could not be detected. CEA analyses in the body of R. philippinarum after 4 days' exposure to contaminated sediments seem to be the most sensitive and reliable.
In this study, an attempt has been made to analyze the morphology of Cephalopods distributed in Korea and collected samples from South-East Asian countries including Thailand, Indonesia, Vietnam, and China. A phylogenetic analysis was performed using the mitochondrial gene, Cytochrome c oxidase subunit I (COI) to understand the genetic divergences of the species and validate their origins. For achieving the objectives, samples were collected directly from Thailand Hat Yai, Songkhla, Indonesia Medan, Vietnam Ho Chi Minh, and Vung Tau in August 2015 and from China in September 2015. A total of 23 species of Cephalopods were identified falling under three orders, four familyies and nine genus. The species were distributed under Order: Octopoda (1 family, 3 genus, and 9 species), Order: Sepiolioda (1 family, 2 genus, and 8 species), and Order Teuthoidea (2 family, 4 genus, and 6 species). 23 species which is 1 family 3 genus 9 species in Octopoda, 1 family 2 genus 8 species in Sepiolioda, 2 family 4 genus 6 species in Teuthoidea. Phylogenetic analysis using COI gene was conducted for 18 species. For the remaining 5 species sequencing results showed severe variation and hence were not considered further. The COI phylogenetic analysis for the 18 species of Cephalopods were found consistent with the morphological identification. The excluded species will be subjected for a further detailed analysis.
Carbonic anhydrase (CA), which is involved in shell formation processes in bivalves, is one of the major biocatalysts for carbon capture and storage. In this study we investigated CA activity in the total hemocytic proteins of five bivalves. The highest CA activity was observed in Scapharca broughtonii, which had more than twice the activity found in Crassostrea gigas. No CA activity was observed among the total hemocytic proteins of Pinctada fucata and Saxidomus purpuratus. The results suggest that marine invertebrates may provide a better source of CA, as an alternative to mammalian sources.