Mi Ae Jeon

Gonadal Development and Reproductive Cycle of the Boring Bivalve Barnea Da Vidi (Deshayes, 1874) in Hampyeong Bay, Korea (Bivalvia: Pholadidae)

ABSTRACT This study describes histologically the reproductive cycle of Barnea davidi inhabiting Hampyeong Bay on the western seashores of Korea. A total of 578 B. davidi, collected from February 2010 to January 2011 with a shell length of 89.5 ± 7.7 mm and a total weight of 47.5 ± 13.7 g, were used for analyses. The sex of B. davidi was distinguishable by both the ovary and testis, which were contained in multiple gametogenic follicles. The gonads displayed histologically definitive seasonal changes. Although the sex ratio (female to male) was 1:1.32 (n = 229:303), the proportion of males increased as the shell length increased. The gonad index (GI) of both males and females was the highest in May, and was the lowest in November for females and in December for males. The pattern of changes in the GI was similar to the pattern of seasonal changes in gonadal tissues and water temperature. The condition index was highest in April and lowest in October. The correlation between the pattern of monthly changes in condition index and the monthly changes in GI and development of gonads was low. The main spawning period of B. davidi was June to July, and the reproductive cycle was divided into the inactive stage (November to December), early active stage (January to March), late active stage (March to May), ripe stage (May to June), and the spent and degenerative stage (July to October).

Gonadal Development and Reproductive Cycle of Cultured Abalone, Haliotis discus hannai (Gastropoda: Haliotidae) in Korea: Implications for Seed Production

ABSTRACT The objective of this study was to examine gonad development and reproductive cycle of the abalone Haliotis discus hannai at three main abalone aquaculture farms (Uljin, Wando, and Jeju Island) in Korea to obtain information on artificial seed production. The sex ratio (female:male) was approximately 1:1 without significant difference among the three regions or between females and males. Average gonad index was the highest during July in Uljin and Jeju Island and during August in Wando. There was no definitive seasonal change in condition index and meat weight index throughout the year in the three regions. The gonad of H. discus hannai displayed seasonal change histologically, thereby enabling us to distinguish the following stages: inactive (November–December), early active (January–March), late active (March–April), ripe (May–July), spent (August–October), and degenerative (October–November). The main spawning period of H. discus hannai was determined to be during September–October in Uljin and Wando, and August–September in Jeju Island.

Sex change and sequential hermaphroditism in Tegillarca granosa (Bivalvia: Arcidae)

This study aimed to confirm sex change in Tegillarca granosa to determine whether this species is a sequential hermaphrodite. Samples of bivalves were divided into two groups, namely, a 1+ year class (14 months) and a 2+ year class (26 months), for analysis. At the beginning of the study, 44.3% of T. granosa were female, and after one year, this increased to 53.9% in the same population. The increase of females in the population was greater in the 1+ year class (12.3%), when compared with the 2+ year class (6.5%). Overall, a sex change ratio of 15.1% (n = 104/688) was recorded for T. granosa. The sex change ratio of the 1+ year class (17.8%) was higher than that of the 2+ year class (12.1%), and displayed the tendency of being higher in the males (21.2%), than the females (6.2%). The results of this study indicate that T. granosa is a sequential hermaphrodite.

Microanatomy and ultrastructure of outer mantle epidermis of the cuttlefish, Sepia esculenta (Cephalopoda: Sepiidae).

This study describes the ultrastructural characteristics of external epidermis of mantle of Sepia esculenta using light and electron microscopy. The epidermis was thicker on the ventral surface than on the dorsal surface, with a higher secretory cell distribution on the ventral surface than on the dorsal surface. The epidermis was a single layer composed of epithelial cells, secretory cells, ciliated cells and neuroglial cells. Epithelial cells were columnar with well-developed microvilli on the free surface, and the microvilli were covered with glycocalyx. The epithelial cells were connected to the neighboring cells by tight junctions and membrane interdigitations of the apico-frontal surface. Well-developed microfilaments were arranged in a vertical direction in the cortical cytoplasm. The secretory cells were categorized into three types (A, B and C) in accordance with the light microscopical characteristics and ultrastructures of the secretory granules. The distribution of these cells was in the following order: Type A>Type B>Type C. SEM observation revealed that the secretory pore size of the Type A secretory cells was approximately 8.6 μm×12.2 μm. Cytoplasm displayed a red color as the result of Massons trichrome stain and H-E stain, and contained polygonal granules of approximately 1.2 μm2 with a high electron density. The secretory pore size of the Type B secretory cells was approximately 10.1 μm×12.1 μm. As the results of AB-PAS (pH 2.5) and AF-AB (pH 2.5) reactions, the cytoplasm displayed a red color. The cells contained membrane bounded secretory granules with very low electron density. The secretory pore of the Type C secretory cells was circular shape, and approximately 5.5 μm×5.5 μm. Cytoplasm was found to be homogeneous under H-E stain and Massons trichrome stain, and displayed a red color. As the result of AB-PAS (pH 2.5) reaction, the cytoplasm displayed a red color. The electron density of the secretory substance was the highest among the three types of secretory cells. The ciliated cells had a ciliary tuft on the free surface and were distributed throughout the mantle with the exception of the adhesive organs. Neuroglial cells were connected to the basal membrane, epithelial cells, secretory cells and nerve fibers through cytoplasmic process, and contained neurosecretory granules with high electron density within the cytoplasm.

Intersexuality of Scomberomorus niphonius from the Coastal Area around Jeju Island, Korea (Teleostei: Scombridae).

This study histologically describes the intersexuality of Scomberomorus niphonius collected from the coastal area near Jeju Island. A total of 126 S. niphonius, collected from March to July 2012 with a total length of 62.4 cm (±17.5) and a total weight of 1,701.9 g (±1,528.9) were used for analyses. From a histological perspective, two types of intersex were confirmed. One type had scattered germ cells from the opposite sex within the gonad. The second type developed germ cells from the opposite sex in the connective tissue of the outer gonadal membrane. The intersexuality was 14.3% (n=18/126), with females (21.3%; n=16/75) exhibiting a higher rate than males (3.9%; n=2/51). There was no displayed correlation between intersexuality and the total length and weight.