• The Korean Journal of Pesticide Science
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• v.14 no.2
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• pp.157-163
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• 2010

This study was performed to investigate the hatching rate and eggs period until hatching in the laboratory against lantern fly, Lycorma delicatula eggs with different collecting date of eggs, and the susceptibility of 26 insecticides to the eggs, 1st and 2nd nymphs of Lycorma delicatula. The eggs of L. delicatula were increased the hatching rates as passed collecting date of eggs, and shorten in eggs period until hatching. By screening the susceptibility of 26 insecticides to the eggs, 1st, and 2nd nymphs, chlorpyrifos (312.5 ppm) showed the perfect inhibition effect of hatching against the eggs, however, the other insecticides did not show that effect. According to the collecting date of eggs, chlorpyrifos bioassayed the inecticidal effect with different concentration (625 ppm at double conc., 312.5 ppm at recommended conc., and 156.3 ppm at half conc.). The eggs collected from Apr. 20th 2010, were showed the inhibition effect of hatching over 94.5%, but the eggs collected from May 10th, 2010 were showed the inhibition effect of hatching as 86.7, 71.1, and 47.1%, respectively. However, hatched eggs were all killed perfectly within 24 hours. At recommended and half concentrations, the eggs collected from 15, May, are decreased the effect as 48.6%, 53.7%, respectively, and the mortality of eggs hatched also decreased as 61.0 and 22.0%, respectively, however, double concentrations did not show the changes. From the above results, it will be anticipate to show the higher mortality against the eggs of L. delicatula when treated chlorpyrifos until late-April.

• Journal of Aquaculture
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• v.14 no.1
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• pp.17-27
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• 2001

Effects of temperature (10, 12, 14, 16, 18 and 2$0^{\circ}C$) and salinity (22.0, 24.5, 27.0, 29.5, 32.0 and 34.5 ppt) were studied on incubation period, hatching success, survival and growth of alevin and juvenile seabass, L. japonicus. Embryonic development was accelerated with increasing temperature but it was not influenced by salinity. Hatching success was the highest at 14$^{\circ}C$ and 34.5 ppt. Higher temperature also accelerated the development of mouth opening, absorption of yolk and oil globules, and alevin growth. Survival of the 5-day old Juvenile was accelerated in the following order : 14<16<18<20<12$^{\circ}C$. Rearing experiment of the juvenile for 30-day indicated the faster growth at 13, 20 and 27 ppt than at 34 ppt.

• Ocean and Polar Research
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• v.39 no.4
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• pp.257-267
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• 2017

Although Pacific mackerel (Scomber japonicus) is an important commercial species in Korea, its recruitment mechanism remains largely unknown. Diel vertical positioning of larvae in the water column, which is affected by their specific gravity and the surrounding water density, may help to provide an understanding on recruitment success through predator avoidance and prey availability. The specific gravity measurement on Pacific mackerel eggs and larvae would seem to be essential information necessary to learn about the transport process from spawning to nursery grounds, and consequently the recruitment success. Eggs were artificially fertilized, and larvae were fed with rotifer when their mouths opened 3-4 days after hatching. We conducted the experiment using a density gradient water column to measure the ontogenetic changes in specific gravity from fertilization to 10 days after hatching. Egg specific gravity was stable during most of the embryonic period, but a sudden increase to $1.0249g\;cm^{-3}$ happened just before hatching. However, the specific gravity of newly hatched larvae was much lighter ($1.0195g\;cm^{-3}$), and specific gravity tended to increase continuously after hatching. Comparison of specific gravity with seawater density reveals that eggs and newly hatched larvae can float in the surface layer of the ocean. For the later period of the experiment, the specific gravity showed a cyclic diel pattern: the highest in the evening while the lowest at dawn. The fullness of larval stomach may be responsible for the observed differences in specific gravity, because stomach fullness was lower (40-60%) at midnight, and higher (80-85%) in evening. The diel pattern of specific gravity might provide clues regarding how larvae match the diel vertical migration of prey organisms.

• Ocean and Polar Research
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• v.28 no.2
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• pp.201-207
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• 2006

We studied variation in clutch size, hatching, fledging and breeding success of the Black-tailed Gull (larus crassirostris) at Hongdo Island, which supported the largest breeding colony of the species, in South Korea in 1997 and 2000 to 2003. Cluck size was recorded in 1,388 nests and breeding success was estimated in 83 nests. Mean clutch size was 1.89 t 0.65. A total of 63.9% of the eggs hatched and 53.5% of the chicks survived until fledged. Breeding success was 34.2%. Causes of breeding failure were eggs missing (14.9%), rotten eggs (15.5%) and predation (2.4%) during the incubation period and chicks missing(35.8%), starvation (7.4%) and pecked chicks (3.2%) during the chick rearing period. In 2002, the main causes of breeding failure were eggs missing (17.2%) and rotten eggs (6.9%) during the incubation period and missing chicks (15.5%), starvation (3.5%) and pecked chicks (6.9%) during the chick rearing period. Most chick mortality occurred within three days after hatching.

• Journal of Environmental Health Sciences
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• v.34 no.4
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• pp.292-299
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• 2008

The purpose of this study was to investigate the teratological effects of enrofloxacin, a veterinary antibiotic, on the embryos and fetus of hatching chicken eggs. A control group and four experimental fertilized egg groups were set up. The four experimental groups were injected with 0.05 ml, 0.1 ml, 0.2 ml, and 0.3 ml enrofloxacin ($50{\mu}g/ml$) respectively. During the hatching period, the weights of total eggs, inside material(yolk and white) and embryos or fetuses, embryo growth, and teratological effects were investigated. In the experimental groups (fertilized eggs injected with 0.05 ml, 0.1 ml, 0.2 ml and 0.3 ml enrofloxacin), the weights of total eggs were decreased, but the yolk and white weights were increased by the higher amount of antibiotics. The weights of embryos (fetuses) in experimental groups were 86.1%, 78.6%, 65.6% and 61.4% of the control, respectively. Retarded growth, deformity and embryo loss were observed in experimental groups. Teratological effects such as undeveloped eyes, wings and legs, and deformed head and bill were also detected. In conclusion, we found that veterinary antibiotics, enrofloxacin have made teratological effects on the embryos and fetus of hatching eggs.

• Korean journal of applied entomology
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• v.58 no.1
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• pp.69-76
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• 2019

This study was evaluated to increase the production efficiency of Gryllus bimaculatus De Geer, which are recently increasing attention as industrial insects in Korea. In this study, the hatching rate and larval period were investigated along with temperature and humidity, as well as the survival rate and ovipositional temperatures along with rearing density. The optimum relative humidity for hatching was highest at 90%, which shows the hatching rate of 90%. The highest hatching rate was 98.3% at $20^{\circ}C$. The hatching period was shortest at $35^{\circ}C$ incubation, which shows 7.1 days in average. The survival rate at 3,000-20,000 individuals in the breeding container was 34-18% after rearing for 35 days. In the effect test of feeding vegetables, the survival rate was 1.8 times and the biomass weight 2.5 times higher than that of normal individuals respectively. The number of laying eggs by temperature was highest at $25^{\circ}C$, which shows 1,710 eggs after reading for 30 days.

• Development and Reproduction
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• v.17 no.4
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• pp.427-434
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• 2013

The histological changes in the Ussurian bullhead, Leiocassis ussuriensis, and the Korean bullhead, Pseudobagrus fulvidraco, were observed during the early period of growth. The retinas size of both species increased in the 9 days post-hatching (DPH) (p<0.05). In the just-hatched Ussurian bullhead, the retina already consisted of six layers: the epithelial layer, ganglion cell layer, inner nuclear layer, inner plexiform layer, outer limiting membrane layer, and rod and cone layer. The Korean bullhead had the same components. At 50 DPH, the thickness of the retina was $538.0{\pm}7.19{\mu}m$ in the Ussurian bullhead and $558.9{\pm}9.44{\mu}m$ in the Korean bullhead. The relative thickness of each layer of the retina did not differ significantly in the two species. Although the growth of the Korean bullhead's retina was faster, the relative thickness of each layer in the retina did not change during early development. After hatching, some parts of the tissue gradually became denser. Immediately after hatching, the kidney and midgut epithelium of the Ussurian bullhead and Korean bullhead were already formed and grew gradually thereafter. From 0 DPH to 30 DPH, the nuclear height in the midgut epithelium did not differ significantly between the two species, but at 50 DPH, it was $11.4{\pm}2.45{\mu}m$ in the Korean bullhead and $9.9{\pm}2.13{\mu}m$ in the Ussurian bullhead. During the experimental period, the major axes, minor axes, surface areas, and volumes of the proximal tubule cells in the kidney did not differ significantly between the two species. Thus, the early histological development of the Ussurian bullhead is similar to that of the Korean bullhead.

• Korean Journal of Ecology and Environment
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• v.42 no.1
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• pp.32-38
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• 2009

The hatching rate of the eggs of Triops longicaudatus (LeConte), an endangered tadpole shrimp species in Korea, was experimented in different levels of temperature (10, 15, 20, 25, 30, 35, 40, 45, and $50^{\circ}C$) under 24 L photoperiod conditions in incubator. Eggs of T. longicaudatus in this study were obtained from the adults collected from Andong-si, Gyeongsangbuk-do, Korea, in July 2006. The highest hatching rate was the 80.0 (${\pm}9.43$)% in average at $35^{\circ}C$. The thermal threshold for hatching was derived at $6.66^{\circ}C$. However, eggs were not hatched both at $10^{\circ}C$ and at $50^{\circ}C$ during the experimental period.

• Journal of Aquaculture
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• v.11 no.4
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• pp.529-546
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• 1998

Gonadal part that developed by indifferentiation period for 6 months after hatching is made as gonad and fat body. These gonad are thin semi-transparant and undistinguished germ cell. Germinal epithelium is distinguished by development of gonad epithelial tissue from 7 months after hatching. Sex differentiation is begun by oogonia develoment at 8 months after hatching. Primary oocytes grow over germinal epithelium of gonadal cavity, at 9 months after hatching, gonadal cavity become ovarian cavity as they increasing. As soon as oocytes at 13 months after hatching are filled with the whole part of gonad, degeneration of oocyte is begun. And then, gonad has cavity tissue, a small number of oocyte are located in gonadal cavity. At 15 months after hatching, new primary oocyte develop and cavity of ovarian tissue in the central of ovarian cavity. Spermatogonia multiplicate and cavity tissue consist of testicular tissue. These gonad become hermaphrodite and then ditermine the sex of female and male. These results show the red sea bream is juvenile hermaphrodite and undif-ferentiated gonochoristic teleost. Male and female differentiation type of gonad is divided in undifferentiation stage, oogonia-like stage, ovary-like stage, ovary development stage, hermaphroditic testis stage, hermaphroditic ovary stage, and testis development stage. Undifferentiation stage is continued total lenth 18cm at 13 months after hatching. ovary-like stage is continued total length 11~18cm at 13 months after hatching. Ovary-like stage is continued total length 14~26cm at 10~14 months after hatching. Ovary development stage begins from total length 20cm, 14 months after hatching. At 20 months after hatching, 44 percent of total sampled individuals had ovary. Hermaphroditic ovary stage first begins total length 19~20 cm at 15 months after hatching, but it is not observed total length 28~29cm at 20months after hatching. Hermaphroditic testis stage first begins total length 21~22cm at 20months after hatching and is continued for 20months. Testis development stage first begins total length 20~21cm at 20 months after hatching, and is occupied 33 percent total length 28~29cm at 20 months. The beginning of sex differentiation more than 50 percent is from total length 16cm at 11 months after hatching. Sex determination begins total length 20cm, 14months after hatching in female and total length 20cm, 15 months after hatching in male. Sex determination more than 50 percent begins total length 23cm,, 17 months after hatching. Undifferentiated gonadal part of red sea bream consist gonad and fat body. As differentiation is going on and gonad is growing, fat body shrinks. This appearence is showed the same tendency in 3-year old red sea bream. 1.9mm larvae after hatching grow about 19mm larvae for 47 days. The relationship between the total length and body weight of larvae and juveniles in $BW=4.45{\times}10^{-6}TL^{3.4718}$ r=0.9820. Fishes in cage culture grow to maximum total length 28.4cm. The relationship between the total length and body weight of these fishes is $BW=2.36{\times}10^{-2}TL^{2.9180}$, r=0.9971. Undifferentiated gonadal part of red sea bream consist gonad and fat body. As differentiation is going on and gonad is growing, fat body shrinks.

• Korean Journal of Agricultural Science
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• v.44 no.4
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• pp.531-540
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• 2017

A study was conducted to compare growth performance of six female commercial Korean native chicken (KNC) crossbreeds from hatching to twelve weeks of age. Three hundred and twelve, 1-day-old female commercial KNC were used within 1 paternal line and 6 maternal lines. The chickens were allocated to 24 battery cages to give 4 replicates per strain with 13 chickens per cage. The chickens were reared under continuous lighting (24 h) and water was available at all times. Ad-libitum feeding was practiced throughout the experimental period. Among the six different strains, 2A had the greatest bodyweight (BW) at 42 days after hatching (p < 0.05). No BW difference between six crossbreed strains (p > 0.05) was found thereafter. Crossbreed 1A had the higher average daily gain (ADG) than crossbreed 2A and 3A chickens (p < 0.05), whereas crossbreed 4A, 5A, and 6A had similar ADGs to that of crossbreed 1A (p > 0.05) at 84 days after hatching. Furthermore, crossbreed 4A had a great average daily feed intake (ADFI) from hatching to 84 days (p < 0.05). Nonetheless, there was no difference in the feed conversion ratio (FCR) and uniformity between six crossbreed strains for the experimental period (p > 0.05). Despite that 1A, 4A, and 6A had the higher viability (p < 0.05) than crossbreed 2A and 5A, they had a similar viability than crossbreed 3A (p > 0.05). With this in mind, crossbreed 2A had greater BW, ADG, and FCR than other chicken crossbreeds from hatching to 84 days, although they had a lower viability than others.