• Korean Journal of Ichthyology
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• v.11 no.2
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• pp.126-133
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• 1999

Ultrastructure of the zona radiata and the micropyle of ripe eggs in the rainbow trout (Oncorhynchus mykiss), catfish (Silurus asotus) and loach (Misgurnus anguillicaudatus) were examined by light, scanning and transmission microscopes. The egg micropyle of rainbow trout and catfish consists of a funnel-shaped vestibule and a tapered canal transversing the zona radiata. The micropyle of rainbow trout and catfish showed the similar structure with flat pit and long canal. The micropylar wall showed the clockwise spiral structure in rainbow trout. The micropyle of the loach showed the type with a hollow pit leading into a short canal and the micropylar wall showed the counterclockwise spiral structure. There are numerous and various size pores at the surface area around the opening in every experimented fish. Interconnecting ridges were observed in the unfertilized eggs of every fish.

• Korean Journal of Environmental Biology
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• v.38 no.2
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• pp.323-331
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• 2020

The method of natural spawning is very passive and inconvenient for the study of developmental engineering in marine medaka, Oryzias dancena. The optimum concentration of human chorionic gonadotropin (HCG) and carp pituitary extract (CPE) for ovulation and spawning, and the injection time for the artificial spawning of marine medaka were analyzed in this study. The success rate, survival rate, and hatching rate were highest with 100IU HCG kg^-1 BW and 5mg CPE L^-1 in both male and female marine medaka (p<0.05). After obtaining unfertilized eggs and sperm by the injection of HCG and CPE into the broodstock of marine medaka, artificial fertilization could be successfully achieved any time fertilized eggs are needed in this species. This result should be useful for developing a study program for marine medaka as an experimental animal.

• Development and Reproduction
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• v.22 no.1
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• pp.111-117
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• 2018

The objective of this study was to determine the mitotic intervals (${\tau}_0$) of two consecutive cell divisions and synchronous embryonic cleavage in grass puffer, Takifugu niphobles at different water temperatures (18, 20, 22, and $24^{\circ}C$). The color of the fertilized egg was light yellowish. The egg type was demersal and unadhesive. Egg weight was $0.09{\pm}0.002mg$. The sizes of unfertilized eggs were smaller than fertilized eggs in major axis and minor axis at $20^{\circ}C$ (p<0.05). The size of the fertilized egg of $18^{\circ}C$ water temperature group at the blastodisc stage was the smallest (p<0.05), but no significant differences were observed in the other water temperatures group except $18^{\circ}C$ water temperature group (p>0.05). The first cleavage stages at 18, 20, 22, and $24^{\circ}C$ were at 75, 90, 105, and 120 mins, respectively. As water temperature was increased, embryonic development and formation time of the first cleavage furrow were accelerated. There were negative correlation between ${\tau}_0$ and water temperature for grass puffer (Y=-1.225X+70.05, $R^2=0.988$, n=10, where Y was ${\tau}_0$ and X was temperature). This study confirmed that successful hatching of grass puffer was related to water temperature. Chromosome manipulation will be helpful for this species using cleavage frequency and ${\tau}_0$.

• Journal of Aquaculture
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• v.10 no.1
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• pp.25-32
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• 1997

Develoment precess and characteristics of eggs of the geoduck clam, Panope japonica are reporting in this study. Eggs and sperm were excised from gonad, artificially fertilized in an aquarium, reared under various temperature regimes, and record and record the larval period and the time need to reach a certain larval stage from ferilization. Unfertilized eggs of P. japonica appeared to be oval with a mean diameter of $70\mu$m and they became spherical after fertilization. The eggs of P. japonica can be classified as demersal. At a constant water temperature of $ 11^{citc}C$, it took 4 hours form fertilization to become four-cell stage, two days to become trochophore larvae, three days to become D-shape larvae, twenty-three days to become umbo stage, and thirty-six days to become fully grown veliger ready form settlement. A negative correlation was observed between the water temperature and the larval period of P. japonica. From fertilization to D-shape larvae, it took five days at 8$^{\circ}C$, while it was only two days to become D-shape larvae at $ 17^{citc}C$. Time required to D-shape larvae from fertilization was proportional to temperature, and the relationships were expressed as follows : To 8-cell stage, 1/t=0.0209 w-0.1167 (r=0.9967) To blastula stage, 1/t=0, 0055 w-0.0192 (r=0.9825) To trochophore stage, 1/t=0.0034 w-0.0155 (r=0.9907) To D-shape larvae stage, 1/t=0.0014 w-0.0023 (r=0.9843) (t, time in hours ; w, water temperature) Bioligical minimum temperature for egg development was calculated as 3.82$^{\circ}C$ in average.

• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 2003.10a
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• pp.158-158
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• 2003

Bioassays using gametes of sea urchins are widely used in ecotoxicological assessments of marine environments. Since most of sea urchin species in Korean coastal water spawn from spring to autumn, bioassay with them during the winter is impossible. In the course of developing standard methods for bioassays with Korean species, we found a winter-spawning starfish, Asterias amurensis, Since reproductive mode of asteroids is similar to echinoids, the bioassay protocol for sea urchins could be applied similarly to the starfish. Here, we tested and determined several conditions for the acceptability of bioassay with A. amurensis. The least required time for formation of fertilization membrane of fertilized eggs to be easily distinguished from unfertilized ones was 60 min. The threshold of sperm to egg ratio that could make acceptable fertilization rates in controls was 3000. The allowed time for manipulation of sperm after dilution in seawater was at most 3 hr. The optimal exposure time of sperms when the response against toxicant solution was relatively stable was in the range of 20-60 min. The tolerance range of sperms to the salinity of test solution was 26-38 psu. The sensitivity of A. amurensis sperm was intermediate among marine organisms commonly used in aquatic toxicity tests. The sperm bioassay with A. amurensis can be satisfactorily applied to toxicity assessments of marine environments.

• Parasites, Hosts and Diseases
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• v.61 no.2
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• pp.198-201
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• 2023

In the past decade, experts have conducted parasitological research on archaeological specimens in Korea to collect historical parasite infection data. In these studies, parasitologists successfully described the infection pattern of each parasite species in history. However, in the first half of the 20th century, archaeoparasitological reports have been scant. In 2021, we conducted a parasitological examination of a toilet-like structure that emerged in the early 20th century. This structure was built by stacking 2 wooden barrels; and in the study samples, we found ancient Trichuris trichiura, Ascaris lumbricoides (unfertilized), and Taenia spp. eggs and therefore proposed a higher possibility that the barrels could have been used as a toilet at the time. To understand how the antihelminthic campaign since the 1960s helped reduce parasite infection rates in Korea, more research should focus on early-20th-century toilet ruins.

• Korean Journal of Ichthyology
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• v.2 no.2
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• pp.169-181
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• 1990

The development of eggs and larvae, and minute scale-like tubercles on the skin surface of larval Acantlaorhodeus gracilis from Korea were observed. They spawned from late March through the middle of June. A fish spawned at least 5 times and the number of eggs averaged 304 per oviposition. Unfertilized eggs are nearly ovoid-shaped(mean$\pm$SD=$2.09{\pm}0.04\;mm$ in length with range of 2.05 to 2.13 mm and mean$\pm$SD=$1.26{\pm}0.02\;mm$ in breadth with range of 1.24 to 1.30 mm measured for the 50 eggs) and opaque yellow color. The tip of egg membrane at the animal pole side swelled and formed a few hilly projections. The shape of the eggs was just like a loquat. Most of embryos began to hatch out in thirty-eight hours after insemination at $22{\pm}1^{\circ}C$ in water temperature. As regards the morphological characters of the eggs and larval development, Acan. gracilis was similar to Acan. asmussi, Acheilognathus rhombeus, A. longipinnis and Pseudoperilampus typus. The larvae of this species is unique particularly in the following two characters, i.e., 1) scale-like tubercles ellipsoided in a diagonal cross section on the whole body and 2) incessant wiggly movement pattern as that of fly maggot, with the larvae of the above mentioned species. These characters seem to reflect the phylogenetic relationships among acheilognathine fishes. On the other hand, this species and Acan. asmussi are spring-summer spawning bitterlings. And also these species never retard the larval growth in such larval stage as the duration from Stage B to Stage D.

• Korean Journal of Environmental Biology
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• v.38 no.4
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• pp.586-593
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• 2020

This study was conducted to investigate the biological characteristics of Phanuromyia ricaniae (Hemiptera: Platygastroidea), an egg parasitoid of Ricania sp. (Hemiptera: Ricaniidae) as a biological control agent to control Ricania sublimata. The developmental period of P. ricaniae was 3.8 days for eggs, 11.1 days for larvae, and 16.3 days for pupae at 25℃, and 3.4 days for eggs, 7.8 days for larvae, and 15.3 days for pupae at 30℃. Except for the larval stage, the developmental periods were not significantly different, but the egg-to-pupa period at 30℃ was significantly shorter than that at 25℃. P. ricaniae emerged at the photophase in 24 hours, but not at the scotophase. A higher emergence rate (34.5%) was seen from 10:00 to 12:00 after the lights were turned. The female-to-male ratio of P. ricaniae was 3:1. The longevity of P. ricaniae adults was 49.0 days for females and 44.0 days for males at 20℃, 27.6 days for females and 28.4 days for males at 25℃, and 18 days for females and 14.0 days for males at 30℃. Its longevity at a low temperature (20℃) was longer than that at higher temperatures (25 and 30℃). Adult females laid eggs during all days except from 00:00-02:00 (scotophase time). The ovipositional distribution rate was 26.1% from 20:00 to 22:00, which was the peak, and the next peak was 15.7% at 10:00 to 12:00. P. ricaniae showed arrhenotokous parthenogenesis in which unfertilized eggs develop into males. Therefore, the results suggest that P. ricaniae may be a biological control agent for R. sublimata.

• Korean Journal of Animal Reproduction
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• v.22 no.4
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• pp.395-403
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• 1998

In this study we determined fertilization processes and developmental ability of porcine oocytes following injection of round spermatid in the presence and absence of artificial activation. Electrical stimulation at 2 h before spermatid injection significantly increased the incidence of normal fertilization as compared to those following injection without stimulation or with stimulation immediately after injection. The incidences of two pronuclear formation and apposition were not different in oocytes between following intracytoplasmic spermatid and spermatid nucleus injection. Indirect immunocyto chemistry and laser scanning confocal microscopy study revealed that microtubuels were organized from the oocyte cortex following round spermatid injection, and this seemed to move both male and female pronuclei into the oocyte center. At 6 days following injection blastocoele formation was seen in the eggs following round spermatid (25%) and round spermatid nucleus injection (27%). However, none of oocytes developed to the blastocyst stage at 6 days following sham injection. The average cell numbers of blastocysts at 8 days following injection of spermatid and spermatid nucleus were 87 to 99. These results suggested that either round spermatid or it's nudeus can be used to produce viable embryos by injection into unfertilized oocytes in the pig.

• Korean Journal of Ichthyology
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• v.2 no.2
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• pp.159-168
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• 1990

Parental fish of R. uyekii(Mori) were colleted from the Nakdong River, Korea. Artificial insemination was carried out 4 times during June using the same pair (a female 52.70 mm TL and a male 56.80 mm TL). Unfertilized eggs are nearly spindly, opaque yellow in colour, measuring about 3.20-3.50 mm in length, about 1.50-1.80 mm in breadth. Hatching began about 50 hours after insemination at water temperature of $16.5{\sim}18.5^{\circ}C$. The newly hatched larvae are 4.10-4.50 mm in total length(TL), with 29-30 myomeres. Nine days after hatching, the larvae averaged 8.40 mm in total length and caudal notochord flexed at $45^{\circ}$. Eighteen days after hatching, total length reached 8.90 mm. The part of the fin-fold of the future dorsal and anal fins became high. Twenty-eight days after hatching, total length was 9.35 mm. The caudal fin-rays began to fork into two branches. The increased number of melanophores appeared newly on the head dorsal and anal fin-rays. The larvae reached the juvenile stage at 50-60 days after hatching and attained 14.50-16.20 mm in total length, and all fin-rays was formed.