• The Korean Journal of Malacology
• /
• v.27 no.2
• /
• pp.91-97
• /
• 2011

This study examines the morphological features of larval and postlarval shells of the paedomorphic bivalve Crenella decussata Montagu, 1808 from the Sea of Japan. During the early morphogenesis of the shell of C. decussata the following characteristics appear: prodissoconch I -the anterior and posterior provincular teeth, a broad primary ligament pit located on the chondrophore; nepioconch - the anterior and posterior juvenile teeth,primary lateral teeth, fine commarginal and radial sculpture. Larvae of C. decussata distinctly differ from other mytilid larvae by a D-shaped shell, absence of umbo, astraight hinge margin, and homogeneous fine-grained sculpture without co-marginal lines of growth. These shell characters indicate lecithotrophic development of this species. Some morphostructures are revealed which might be used in crenellin taxonomy.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.7 no.1
• /
• pp.1-6
• /
• 1974

Meretrix lusoria is one of the most favorite edible bivalves inhabiting wide inter-tidal flats along the western coast of Korea. Over the period of July to September 1973, some specimens from a tidal flat near AnMyun Island were submerged in sea water with various concentrations of ammo-mum hydroxide added and careful observations were made on their fertilization, early development, and metamorphosis of the larvae. The highest rate of fertilization was demonstrated by individuals treated with 1/1000 normal solution of ammonium hydroxide, and their fertilized eggs followed normal development, i. e., two cell stage in 1.2 hours after fertilization, gastrula stage after 4.7 hours, and trochophore stage after 5.6 hours. Within 24 hours after fertilization M. lusoria larvae have acquired the form of early straight-hinge veliger with the mean prodissoconch I length of $112\mu$. It takes seven days to get the umbo stage with the mean shell length of $172\mu$ and twenty days to get the metamorphosing stage with the mean shell length of $232\mu$. The larvae were cultured to the metamorphosing stage with the shell length of $272\mu$ in the laboratory condition. The relationship between the shell length (L) and the shell height (H) in veliger stage is shown as H=1.02325L-24.46425 with a significant difference.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.6 no.1_2
• /
• pp.76-80
• /
• 1973

Cyclina sinensis is an edible bivalve inhabiting wide tidal flats which are exposed to the air at ebb tide along the western coast of Korea. Over the period of June to September 1971, some specimens from a tidal flat near Inchon were submerged in sea water with various concentrations of ammonium hydroxide added and careful observations were made on their fertilization, early development, and metamorphosis of the larvae. The highest rate of fertilization was demonstrated by individuals treated with 1/1000 normal solution of ammonium hydroxide and their fertilized eggs followed normal development, i.e., two cell stage 1.5 hours after fertilization, blastular stage after 4 hours, and trochophore stage after 6 hours. Within 24 hrs after fertilization C. sinensis larvae have acquired the form of early straight-hinge veliger with the mean prodissoconch I with the length of $110\mu$. It takes seven days to get the umbo stage with the mean shell length of $190\mu$ and twenty days to get the morphosing stage with the mean shell length of $260\mu$. The larvae were cultured to the metamorphosing stage with the shell length of $270\mu$ in the laboratory condition.

• The Korean Journal of Malacology
• /
• v.30 no.4
• /
• pp.311-319
• /
• 2014

Early sexual maturation through temperature stimulation was induced in female and male of yezo scallop. Gonadosomatic index (GSI) in female showed $9.12{\pm}2.9$ in January, $14.89{\pm}2.9$ in February and $21.3{\pm}1.4$ in March in experiment I. GSI in experiment I showed a significant increase (P < 0.05) and in experiments II and III were not show significant variations (P > 0.05). It also showed significant between the control and the experiments I, II, and III in February (P < 0.05) measurements. Experiment I has showed good results in sexual maturation and spawning when compared with other experiments II and III and the control. Histological observation showed that ovary condition was in a growing stage in all the experiments I, II, and III. In February, ovary condition through histological observation was a late mature stage in all the experiments I, II, and III except the control of a growing stage. GSI and gonad weight were $4.4{\pm}0.88$ and 2.8 g, respectively in November whereas it was $15.1{\pm}2.8$, and 11.7 g, respectively in January and $21.7{\pm}5.4$, and 19.4 g, respectively in February after rearing at a water bath of $12^{\circ}C$ depending on the condition of experiment I. It was possible early releasing of eggs and sperms of yezo scallop in February instead of the middle of April to the end of May being spawning period. Fertilized eggs have become a gastrula stage through a spiral cleavage and then become a trochophore larvae after 36 hours. After 10 days, D-shaped larvae have changed into an umbo stage larvae and attached to juveniles in the post larvae after 20-23 days.