• Korean Journal of Ecology and Environment
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• 제45권2호
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• pp.190-199
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• 2012

The reproductive ecology of an endangered species, Gobiobotia macrocephala (Pisces: Cyprinidae), was investigated in the Seom River, a tributary of the Han River drainage system, from March 2010 to February 2011. During the non-spawning season, no difference in the external morphology was observed between males and females; however, during the spawning season, clear differences merged for the depth and width of the body, preventral length and preanal length in the standard length. The sex ratio of females to males was 1 : 1.01. The spawning season was estimated to last from late April to middle of June, at water temperatures of $15{\sim}25^{\circ}C$. The number of mature eggs in the ovary averaged about $2,134{\pm}930$ (mean${\pm}$SD), and the mean diameter was approximately $0.88{\pm}0.04$ mm. The spawning area was composed of pebble and cobble bottoms (3~10 cm), with current velocities of 13~24 cm $s^{-1}$ and water depths of 12~18 cm. Spawning behavior between males and females was observed in a water tank 14~15 h after injecting females with Ovaprim to promote reproduction. Fish spawned near the water surface with monogamous pairing.

• Journal of Aquaculture
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• 제16권1호
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• pp.24-30
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• 2003

Studies of the seed production of Urechis unicinctus were conducted under the laboratory conditions to obtain some information for the U.unicinitus culture. The experiment included developmental studies of the egg development, larval culture, sediment preference and growth of young U.unicinctus. The experiment were conducted from March to August, 2000. The adults of U.unicinctus collected in Namhae-do, Korea. The developments of the fertilized eggs were observed under a light-microscope at intervals of one hour after containing with density of one individual per 1 $m\ell$. The larvae were fed with Phaeodactylum tricornutum cultured at the laboratory. The concentration of the phytoplankton for the feed was 30,000 cells per individual larva. With progress of development, the food concentration was gradually increased, up to 10,000 cells per individual for the young U.unicinctus. Trochophore larvae appeared on the 68 hours after hatching. On the 32 days after hatching, over 50% of fertilized eggs developed into young U.unicinctus. In order to investigate the effect of sediment on the growth and burrowing of U.unicinctus, the young worms were reared in tanks with different grain sizes. The highest value of sediment preference and survival rate of U.unicinctus was shown in the mixture sediment group with below 0.10 mm, 1.01∼12.00 mm, over 3.01 mm and shell. The lowest value in both sediment preference and survival rate of U.unicinctus was observed in 1.0l∼2.00 mm grain size.

• The Korean Journal of Malacology
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• 제28권1호
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• pp.65-71
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• 2012

Protozoan parasites belonging to the genus Perkinsus elicit severe inflammatory responses and are associated with mass mortality of commercially important marine shellfish worldwide. In the present study, we examined the external features of P. olseni zoospores in detail using light and scanning electron microscopy. Our study showed that the zoospores have an oval body with a long anterior flagellum and a short posterior flagellum. The anterior flagellum has a unilateral array of mastigonemes. Mean body dimensions were $3.37{\pm}0.33{\mu}m{\times}1.72{\pm}0.22{\mu}m$. The average length of the anterior and posterior flagella was $16.34{\pm}1.52{\mu}m$ and $8.25{\pm}1.39{\mu}m$, respectively. Zoospores of P. olseni found in Korean waters have shorter and narrower bodies, longer anterior flagella, and shorter posterior flagella than zoospores of Perkinsus spp. found in the mollusks of North America and Europe.

• Parasites, Hosts and Diseases
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• 제32권3호
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• pp.143-148
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• 1994

The metacercanae of the genus Stictodora encysted in gobies, Acnnthogobiln Snuimanw, purchased from a local market of Haenarn-gun, Chollanam-do, were identified as those of S. fuscotum A total of 1,437 metacercariae were collected from 30 gobies and sonle of them were orally fed to cats in order to obtain the adult worms. The metacercariae were 0.194-0.301 mm by 0.168-0.270 mm In size, yellowish brown, round to elliptical, and with a thin and transparent cyst wall. The excysted larvae were 0.280-0.423 mm long and 0.150-0.184 mm wide, beset with numerous tegumental spines on the anterior half of the body, and equipped 10 a characteristic ventrogenital sac. Total 21 adult worms were recovered from 2 cats 7 days after infection. The adult worms were small, leaf-like, 0.514-0.918 mm long and 0.235-0.377 mm wide. The ventrogenital sac was elliptical and its gonotyl was armed with 13-18 spines which were radially arranged and appeared as fan-shape. It has been confirmed that A. flavimanus is a second interinedlate host of 5. Juscatum In Korea.

• Journal of Aquaculture
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• 제19권4호
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• pp.275-280
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• 2006

Effect of the various sources of dietary additives on growth, body composition and shell color of abalone Haliotis discus hannai was investigated for 16 weeks. Forty juvenile abalone averaging 13.5 g were randomly stocked into 21 of 50 L plastic rectangular containers each. Eight kinds of additives were prepared for this study: four commercially available microalgae [Haeatococcus (Hae), Isochrysis galbana (Iso), Shizochytrium (Sch) and Spirulina (Spi)], three crustacean meals [krill meal (KM), shrimp head meal (Shm) and red crab meal (Rcm)], and green tea by-product (Gre). In addition, dry sea tangle (Dst), Laminaria japonica, as a control, was prepared. Casein, dextrin and a mixture corn oil and fish oil was protein, carbohydrate and lipid sources, respectively, in the experimental diets. The 2% each additive was included into the experimental diets. The experimental diets were fed to abalone once a day at the ratio of $1.5{\sim}2.0%$ total biomass of abalone with a little leftover throughout the 16-week feeding trial. Survival of abalone was not significantly (P>0.05) affected by the experimental diets. However, weight gain of abalone fed the all experimental diets containing the various sources of additives was significantly (P<0.05) higher than that of abalone fed the Dst diet. Weight gain of abalone fed the Spi diet was highest and Shi, KM and Iso diets in order. Shell length and the ratio of soft body weight to body weight of abalone was not significantly (P>0.05) affected by the experimental diets. However, shell width of abalone fed the all experimental diets containing the various sources of additives was significantly (P<0.05) higher than that of abalone fed the Dst diet. The shell color of abalone fed the Spi diet was improved the most distinctively and similar to that of natural abalone. Therefore, it can be concluded that the experimental diets with the various sources of additives (microalgae and crustacean meals) was effective to improve growth of abalone and dietary inclusion of Spirulina was most effective to improve shell color of abalone.

• Korean journal of applied entomology
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• 제24권1호
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• pp.15-18
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• 1985

Studies were made on the morphology and life cycle of the mite, Pyemotes tritici $Lagr{\acute{e}}z$-Fossot & $Montagn{\acute{e}}$ (Trombidiformes; Pyemotidea) ,parasitic on larvae of cigarette beetle, Lasioderma serricorne F., which is one of the most serious pests of stored tobacco, cigar, and cigarette in Korea. One generation time was $20.9{\pm}0.7$ days out of which $9.5{\pm}0.3$ days were spent for feeding and $10.3{\pm}0.8$ days for reproduction of progenies. A female of this insect-parasitic mite produced $56.7{\pm}6.9$ progenies during her reproduction period. The body size of a newly-laid male or female was $280{\mu}m$ long and $85{\mu}m$ wide. As female of this mite sucked on, their abdomen grew larger and larger to reach $825{\mu}m$ in width and $0.346mm^3$ in volume after $9{\sim}10$ days. By sucking the humor of a host, the abdomen of a female mite became almost a global shape in two days. The increase rate of abdominal width was the biggest on the second or the third day of feeding while the volume of abdomen reached to the largest on $6{\sim}8$ days after feeding. The largest number of the daily young produced on 4-th day after a female began to reproduce.