Micromorphology and Ultrastructure of the Foot of the Equilateral Venus <i>Gomphina veneriformis</i>(Bivalvia: Veneridae)

The shape and microscopic structure of the foot of the equilateral Venus, Gomphina veneriformis are described by light and electron microscopy along with the substrate conditions of their habitat. The habitat sediment of G. veneriformis is composed of sand (2 - 0.063 mm in diameter), mainly. The foot is wedge-shaped with multiple vertical furrows on the surface. Although the foot is composed of an epithelial layer, a connective tissue layer and a muscular layer, the boundary between the connective tissue and muscular layer is not clear. The epithelial layer was composed mostly of ciliated columnar epithelia and secretory cells. Epithelial cells forming the apical region of the fold were long columnar, while cells of the interfold were mostly short columnar. The cilia and microvilli were commonly observed on the free surface of epithelial cells, while tight junctions of apico-lateral aspect and membrane interdigitations were found between the epithelial cells. Secretory cells were found to contain acidic mucopolysaccharide, and were classified into two types in accordance with the shapes and ultrastructures of secretory granules. The muscle fibers were composed of thin and thick microfilaments, the proportions of which were 81.3% and 18.7%, respectively. It was determined that such morphology and structural characteristics of the foot of G. veneriformis would present advantageous conditions for borrowing into substrate and mobility.

Allele-specific PCR genotyping of the HSP70 gene polymorphism discriminating the green and red color variants sea cucumber (Apostichopus japonicus)

Color variation is a well-known feature of sea cucumbers （Apostichopus japonicus）, which are classified into three groups based on their colors of red, green and black. It is also one of the most important traits related to how they taste, and it thereby affects their market price. Attempts were made to identify single-nucleotide polymorphisms （SNPs） and to analyze differences associated with SNP genotypes between green and red color variants using HSP70 as the target gene. The HSP70 gene, which is found universally in organisms from bacteria to humans, is one of the most evolutionarily conserved genes and the most widely studied biomarker of stress response. DNA fragments of 1074 bp covering a partial sequence of the sea cucumber HSP70 gene, were amplified from both red and green variants, and subsequently analyzed for the presence of SNPs. Twenty-seven polymorphic sites in total, including heterozygous sites, were observed. Of these, six sites were found to be significantly different SNP genotypes between green and red variants. Furthermore, PCR with an internal primer designed to include an allelespecific SNP at the 3＇ end （site 443） showed differentiation between the two variants, 100% and 4.2% amplification in green and red variants, respectively. The validated SNPs may serve as informative genetic markers that can be used to distinguish variants at the early developmental stage, prior to color differentiation.

Digestive gland ultrastructure of the tunicate,Halocynthia roretzi(Ascidiacea:Pyuridae)in relation to function

Objective:To examine the glycogen storage and lipid digestion,as well as detoxification of the digestive gland of the tunicate,Halocynthia roretzi.Methods:Tunicates used in this study were collected from tunicate aquafarm located in Hansan Bay on the southern coast of Korea.Light and electron microscopy was performed.Results:The digestive gland was divided into the tubular and blind ampulla portions.Fine vacuolar granules were present,and lipofuscin granules were confirmed in the cytoplasm of the epithelia of the blind ampulla portion.Epithelial cells of the blind ampulla portion could be classified into three types.Conclusions:The results indicate that these three types of cells are involved in glycogen storage,lipid digestion and detoxification.