• Korean Journal of Ecology and Environment
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• v.33 no.2 s.90
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• pp.152-161
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• 2000

Simocephalus mixtus Sars was redescribed and illustrated from Korea. It had been frequently confused with S. vetulus (O.F. M$\"{u}$ller) and S. vetuloides Sars in the Far East. Redescription was based on the materials collected from various freshwater habitats at 97 localities in South Korea during the period from May 1981 to June 1999. Previous records of Simocephalus species from Korea were examined. S. mixtus is well distinguishable from other related species by having short and wide dorso-posterior carapace angle prominence, distally protruding dorsal margin of carapace, deep depression of the ventral head margin near the rostrum, elongate ocellus, and postabdominal claw lacking the basal pecten of denticles.

• Applied Microscopy
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• v.29 no.4
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• pp.451-457
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• 1999

Ultrastructure of adult Drosophila ocellus was compared with conventional electron microscopic method and osmium impregnation. When osmium impregnation was applied, some organelles of cells were strongly stained. Especially, subrhabdomeric cisternae (SRC) were strongly stained and showed network-iike structure as in compound eye. Other organelles including SSC, ER, nuclear envelope, pigment granules and mitochondria were also strongly stained. These organelles are known as a general calcium ion reservoir. In conclusion, the strong effect of light and shade by osmium impregnation was regarded as a result of strong binding between calcium ion and osmium tetroxide. Thus, we agree to the opinion that osmium impregnation is very useful methods to the comparative morphology of cell organelles.

• Applied Microscopy
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• v.29 no.2
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• pp.231-239
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• 1999

Morphological changes of Drosophila ocellar corneagenous cells were studied to the development with electron microscopy, and the movement of produced proteins was traced with autoradiography. Corneagenous cells of immediate postemergence showed very active secretion pattern. However, a few days after the emergence, the secretory activity of corneagenous cell was supposed to be dropped suddenly. In autoradiography, almost of proteins that produced by corneagenous cells moved toward lens. From this, it was supposed that the corneagenous cells do not function in photoreceptor cells rather in the formation of lens at the postemergence stage. Corneagenous cells of pupal stage were well developed. In the period of lens formation, rER of corneagenous cells were well developed and it suggested very active material metabolism. Granules and microtubules were also frequently observed and the later would be a pathway of the movement of materials. In conclusion, corneagenous cells were well developed at vigorous lens forming stage. After emergence, when the lens formation was completed, both the function and the size of corneagenous cells were reduced.

• Journal of Apiculture
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• v.34 no.2
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• pp.107-115
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• 2019

Bumblebees have apposition compound eyes (one on either side of the head) of about 6,000 ommatidia and three small single-lens ocelli on the frons of their head capsule. The surface of the eye is smooth and interommatidial hairs, as in the honeybee, are not developed. Each ommatidium (approx. 26 ㎛ in diameter) is capped by a hexagonal facet and contains in its centre a 3 ㎛ wide, columnar light-perceiving structure known as the rhabdom. Rhabdoms consist of thousands of regularly aligned, fingerlike microvilli, which in their membranes contain the photopigment molecules. Axons from each ommatidium transmit the information of their photic environment to the visual centres of the brain, where behavioural reactions may be initiated. Since bumblebee eyes possess three classes of spectrally different sensitivity peaks in a ratio of 1:1:6 (UV= 353 nm, blue= 430 nm and green=548 nm) per ommatidium, they use colour vision to find and select flower types that yield pollen and nectar. Ommatidial acceptance angles of at least 3° are used by the bumblebees to discriminate between different flower shapes and sizes, but their ability to detect polarized light appears to be used only for navigational purposes. A flicker fusion frequency of around 110Hz helps the fast flying bumblebee to avoid obstacles. The small ocelli are strongly sensitive to ultraviolet radiation and green wavelengths and appear to act as sensors for light levels akin to a photometer. Unlike the bumblebee's compound eyes, the ocelli would, however, be incapable of forming a useful image.

• Development and Reproduction
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• v.13 no.4
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• pp.291-296
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• 2009

In most larvae of ascidian, two sensory pigment cells, otolith and ocellus, lie in their brain vesicle. They also have a third type of sensory cells: hydrostatic pressure receptor (Hpr) cells. The Hpr cells were presumed to be hydrostatic pressure-detection cells, but their precise functions is still disputed. In this study, we investigated whether an FGF signaling is involved in formation of Hpr cells. When fertilized eggs were injected with Hr-FGF9/16/20 antisense MO, the resulting larvae showed severe abnormalities with no expression of the Hpr cell-specific Hpr-1 antigen. Similar results were obtained using an FGF receptor inhibitor, SU5402, and an MEK inhibitor, U0126. Embryos treated with SU5402 or U0126 during the 32-cell and hatching stages did not express the Hpr-1 antigen. To elucidate the temporal requirement for the FGF signaling in formation of Hpr cells, embryos were treated with SU5402 for 2 h, or U0126 for 20 min during various embryonic stages. Larvae treated with SU5402 from the 16-cell stage to the 64-cell stage did not express the Hpr-1 antigen, whereas those treated at the early gastrula stage expressed the Hpr-1 antigen. When U0126 treatment was carried out at various stages between the 8-cell and late gastrula stages, larvae scarcely formed the Hpr cells. They showed expression of the Hpr-1 antigen when embryos were placed in U0126 just before the neural plate stage. These results suggest that FGF9/16/20 signaling is involved in formation of Hpr cells from the primary neural induction stage to the late gastrula stage.