• Journal of Life Science
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• v.13 no.1
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• pp.34-41
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• 2003

The hatching of fertilized egg and early development of larval black seabream, Acanthopngrus schlegeli by immersion of 3,5,3'-triiodo-L-thyronine ($T_3$) with doses of 0.01~0.5 ppm in tank were examined for early development periods and compared with control fish immersed by 0.1 N NaOH and 99% alcohol. Larvae were fed with rotifers for first 5 days during experimental period. Yolk absorption of larvae from $T_3$ immersion groups were significantly faster than that of control. Although hatching times among each groups were not significant difference. the hatching rates of larvae in higher doses (0.1 ppm and 0.5 ppm $T_3$ groups) were significantly lower than control. The results of $T_3$ immersion experiments to newly hatching larvae indicated that exogenous $T_3$induced significant faster the absorption of yolk and oil globule, faster the development of myotome and digestive duct and higher the growth rate of larvae than larvae of control. These results indicate that $T_3$ immersion supplements appear to confer a distinct advantage to eggs and larvae of black seabream, which is in early fragile developmental stage.

• 한국해양학회지
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• v.4 no.1
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• pp.36-48
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• 1969

The larvae of Mytilus coruscus were grown at the room temperature of approximately 15.1C under several different sulture conditions, i.e., salinity, population of the larvae, density and kind of food organisms, etc. (1) The egg of Mytilus coruscus obtained in the laboratory measured about 73.0${\mu}$ in diameter. The embryos gradually developed into larvae up to 179.0${\mu}$ shell length with the shell height of 135.9${\mu}$ even in the absence of the algal food. Beyond this size, however, the growth of larvae was considerably retarded, indicating that the better growth could be expected if the food began to be fed four days after spawning. (2) The larvae began settling upon reaching 281.4${\mu}$ to 310.9${\mu}$ in shell length or 264.3${\mu}$ to 301.9${\mu}$ in shell height. When the shell length reaches 322.6${\mu}$ to 337.1${\mu}$, the shell height also reaches about the same, i.e., 321.5${\mu}$ to 346.2${\mu}$. (3) Daily rate of food consumption was determined by the size of the larvae and the species of the algal food. Regardless of the species of food given, the rage of food consumption remained almost the same until the larva reached the straight-hinge stage, and marked variations were found as the larvae grew larger. Daily rate of food consumption was shown as follow; Chaetoceros calcitrans : Y=2.99167e$\^$0.000018243x$\^$2// Cyclotella nana : Y=3.00324e$\^$0.000015481x$\^$2// Monochrysis lutheri : Y=3.000056e$\^$0.000014485$\^$2// (4) Suitable amount of the food to be given was about five times of the consumed food by Mytilus coruscus. (5) When the numbers of the larvae was higher than ten per milliliter, the growth was significantly retarded. (6) Monochrysis lutheri and Cyclotella nana were much better than Chaetoceros calcitrans as the food of Mytilus coruscus, and even the same food organism showed some difference with the age of the organism. (7) Sea water of higher salinity showed the better result in the growth of the larvae and the water with the specific gravity of 1.020 or below was dangerous for the larvae. (8) The mean growth of the larvae of Mytilus coruscus under lavorable condition was shown as follows: shell length 121.8${\mu}$ to 179.0${\mu}$ : Y=119.18+7.42X 196.7${\mu}$ to 322.6${\mu}$ : Y=203.144+7.687X 322.6${\mu}$ to 985.1${\mu}$ : Y=302.5978+11.8356X shell height 86.3${\mu}$ to 135.9${\mu}$ : Y=86.22+6.40X 158.1${\mu}$ to 321.5${\mu}$ : Y=162.998+10.027X 321.5${\mu}$ to 1,215.4${\mu}$ : Y=309.3701+16.258X Relationships between the shell length and shell height were shown as follows: shell length 121.8${\mu}$ to 179.0 : Y=0.83726X-15.79165 196.7${\mu}$ to 322.6 : Y=1.29909X-100.58610 322.6${\mu}$ to 985.1${\mu}$ : Y=1.3536X-101.6806

• Korean journal of applied entomology
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• v.39 no.3
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• pp.141-147
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• 2000

This study was carried out to investigate the population changes of Liriomyza trijolii (Burgess) on chrysanthemum and its relationship to plant growth and damages. In spring culture of chrysanthemum, L. trifolii adults begun to be attracted by the yellow sticky trap from early May and maintained high population until the middle of July. Larval density increased gradually from late May and reached peak in early July. In autumn culture, the population density of adult was lower than that of spring culture but the number of adult was great in late September and the middle of October. This trend was similar to that of larval stage. Damaged leaves by larva could be found from 4 weeks after transplanting and its rate was low until 5 weeks but increased abruptly after 6 weeks and maintained 70% level until flowering stage in spring culture. Damaged leaves increased with plant growth in some varieties tested in this experiment.

• Korean journal of applied entomology
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• v.4
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• pp.67-74
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• 1965

The work on the 'Studies of radiosensitivity' in Korea has been initiated since 1959 by the author at various institutions in home and foreign countries, and more than 20000 of plant materials in 73 varieties and 41 kinds are treated under varied conditions for the studies of radiosensitivity in plants. However, a study of the susceptibility to radiation in insect pests as well as their biological effects has not been previously reported in this country. During the year of 1964 and 1965, near 50000 of insects at the stages of adult, egg, larva and pupa in 14 different kinds are irradiated under acute X and gamma rays to investigate the behavior of growth and lethality after irradiation, and thrir general tolerances to radiations are compared by the kind of insects, stage of growth, radiation sources and exposured dosages. Through the experiments, it is shown that the lethality in most of insects are high as several kilo roentgens above and no significant effects on pupation. emergence, and oviposition in the treated generation at the dose of 3 Kr. below, but in the following generation , the rice stem borer for instance, no oviposition or decreased laying is observed from the dosages at 3 Kr. to 1 Kr., and the hatching was possible from 1.5 Kr. below of irradiated larvae although laying and hatching are seemed in normal. In general, the lethal dose $50\%$ of tested infect materials at the larval stage can he classified some what 60-80 Kr. for Pine caterpillar, Fall webworm, Camphor silk moth and their relatives, at 40-60 Kr. for Gypsy moth, Monley prominent and some relatives and at 20-30 Kr. for House fly, Rice weevil, Pine sawfly etc. Plant parasitic nematodes such as Hirschmannia and Paratylenchus shown very high resistance to radiation and the LD-50 is observed from 100 Kr. or above. A concept to evaluate the radiosensitivity in insects by taxological family line as a practical measure is not answerable yet, but it ran he solved within the near future through the continuing experiments.

• Korean journal of applied entomology
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• v.14 no.4 s.25
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• pp.215-219
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• 1975

The number of instars of pear sawfly larvae (Janus piri Okamoto) collected front field pear trees, were determined by measuring the width of head capsule, and the growth ratio in each instar was also studied. 1. The larval head width had six distinct peaks, which suggests that the larva of this insect passes six instars. 2. The head width tended to increase as the instars avdance, except in tile first and second instars. The coeffieient of variation decressed as the instars advanced. The growth ratio, which was similarly great in the first and second instars, decreased as the instars advanced. 3. Gains' and Campbell's formulae seemed to be more suitable than Dyer's for the determination of larval instars of this insect by the measurement of headwidth. 4. The larval instars could be inferred from the extent of damage to pear tree by this insect; that is the larvae in the second to fourth instars usually gave slight and invissible damage, while those in the fifth to sixth instars gave rapid and severe damage.

• Journal of Marine Life Science
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• v.3 no.2
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• pp.67-73
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• 2018

This study was conducted to investigate the influence of environmental factors such as water temperature, salinity, rearing density and feeding amount on the survival and development of larvae in surf clam, Tresus keenae. As a result of this study, the optimum conditions of larval rearing were as follows. The optimum range of water temperature is 20℃ to 24℃, the optimum salinity is 30 psu, the optimum rearing density is 5 ind./ml and the supply of mixed feed organism for larva rearing such as Isochrysis galbana, Chaetoceros simplex and Tetraselmis suecica is 10×10⁴ cells/ml. The results of this study suggest that the optimum conditions of environmental factors in larval rearing of Tresus keenae contribute to productivity improvement through rapid growth and high survival.

• Korean Journal of Ichthyology
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• v.13 no.1
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• pp.6-18
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• 2001

Larvae of the gunnel Pholis fangi were collected in coastal waters off Daecheon with a bag net from March to June, 1988, and with a ring larva net in February 1989. Maturity and spawning period were analyzed by examination of the gonads of adult fish collected with a bag net from May 1998 through November 1999. In February, the larvae were widely distributed in the outer and inner Cheonsu Bay. From March to April the larvae were present mainly the inner bay; they were absent there in May and found mainly in the outer bay. After June, few gunnel larvae were collected in the study area. This suggests a seaward movement of gunnel from the nursery grounds of the bay to offshore feeding grounds. The otolith of larvae smaller than 10 mm in total length did not show a distinct growth stop. The growth stop is believed to be formed in the early larval stage when the total length is about 10 mm. This period coincides with the time of shoreward migration, suggesting a metabolic change during this period. At a total length of 30 to 40 mm, the shape of the otolith changes from spherical to elongate. Daily growth rate in length was estimated by the Gompertz equation, which is represented as follows: TL = 6.702exp{2.925"1-exp (-0.008 t)"} ($r^2=0.94$, N = 92) Assuming daily deposition of growth increments in the otolith, the time of first growth increment formation was shown to be from December to January. Gonad observations show that Pholis fangi spawns from November to December. So, the hatching time is thought to be about one month.

• Fisheries and Aquatic Sciences
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• v.27 no.4
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• pp.213-224
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• 2024

Betta rubra, classified as endangered fish species by the International Union for Conservation of Nature (IUCN), has been successfully bred and raised in captivity for two generations under laboratory conditions. This study aimed to provide comprehensive information on the captive breeding of B. rubra, focusing on various parameters crucial for ex-situ conservation and domestication. The research involved breeding trials, embryo and larvae observation, first feeding experiments, larva and fry rearing trials, and the evaluation of growth and reproduction in two generations. The study revealed that the female B. rubra, with an average total length of 5.17 ± 0.15 cm and weight of 1.61 ± 0.06 g, produced an average of 73.67 ± 7.09 eggs, 34.33 ± 5.13 total larvae, and exhibited a hatching rate of 46.67 ± 5.77%. The embryogenesis process commenced on the day of spawning (dps) and continued until the eggs hatched at 6 dps. Larvae development and yolk absorption occurred from 0 to 6 days post-hatching (dph). The study also examined the impact of different initial feeding options, with chopped Tubifex resulting in the most significant in- crease (p < 0.05) in length. The growth pattern of B. rubra larvae showed slow initial growth during the first seven days, followed by a rapid exponential growth phase from day 8 to day 39. Two generations of B. rubra (G1 and G2) were successfully bred in captivity, with G2 showing a better tendency for growth in length and weight compared to G1. Notably, there were no significant differences (p > 0.05) in reproductive success between the wild-origin broodstock (G0), G1, or G2. This research contributes valuable insights into the captive breeding of B. rubra and its early life stages, offering critical information for the conservation and sustainable management of this endangered species. Further research is needed to explore the long-term effects of domestication on behavior, physiology, and phenotypic diversity.

• Journal of Life Science
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• v.27 no.6
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• pp.702-707
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• 2017

Insects and their extract have been traditionally used as medicinal resources in Asia. Recently, Gryllus bimaculatus and the larva of Tenebrio molitor, Protaetia brevitarsis, and Allomyrina dichotoma were enlisted as general food ingredients by Korean Ministry of Food and Drug Safety. As the interest in these insects is growing, the detailed investigation is needed for the standardization of suitable and safe rearing techniques. This survey was conducted via personal interviews about edible insect rearing farms in Korea. The basic feed is fermented oak sawdust for P. brevitarsis and A. dichotoma and wheat bran for T. molitor. The various feed additives are blended with each farm's own recipes. The overall growth condition, including sawdust fermentation method, feeding period, and rearing density, varies among the investigated farms. It seems that weight of last instar larva was correlated with the rearing density and duration of the larval period. The heavy metal contents were analyzed after 48 hour starvation and they were very small amount or not detected in investigated insects. We believe that the present data will contribute to develop and standardize the safe rearing techniques of edible insects in Korea.

• Korean Journal of Environmental Agriculture
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• v.6 no.1
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• pp.50-60
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• 1987

Sensitivity, expressed in the $96h-LC_{50}$ determined with continuous flow system, was compared for eight developmental stages of Oryzias latipes with butachlor, diazinon and fenitrothion. Significance of the laboratory determined $96h-LC_{50}$ in real field situation was evaluated for butachlor using outdoor model agrosystem. In the laboratory tests, the most sensitive stage was post-larva stage IV(7 days after hatching) with $96h-LC_{50}$ of 0.14, 1.4, and 1.6ppm for butachlor, diazinon and fenitrothion, respectively, whereas the least sensitive stage was early embryo stage(1 day after fertilization), and then the susceptibility was somewhat stable after 21days after hatching. In the model agrosystem test, the highest concentration of 0.53ppm of butachlor in water was obtained at the 2nd day after application. The stages IV and VIII showed mortality of over 50% at 96 hours after application. It is concluded that the conventional use of butachlor in the field would cause significant adverse effect on O. latipes. It is suggested that sensitivity test at the early life stages with fish is an important part of the ecotoxicological assessment of chemicals.