• Korean Journal of Ichthyology
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• v.21 no.2
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• pp.87-92
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• 2009

Histological investigation of seasonal changes of the mucus cells of ricefield-dwelling mud loach Misgurnus mizolepis was carried out on the skin in three regions of the fish: dorsal, lateral, and occipital. Although there were no significant differences in general morphology, the mucus cells of the epidermis showed a severe change in size and number by skin region. The density of the mucus cells was generally the highest in winter and the lowest in summer in all three skin regions. In particular, during two distinct periods, March to April when water is supplied to the ricefields, and August to September when the ricefields become dry after harvest, showed that the change in density and distribution of the mucus cells in both lateral and occipital regions is greater than during any other period. Moreover, the mucus cells for the dorsal and occipital regions temporally increased in size in June during the period of the highest water temperature of the year. Therefore, we may consider these seasonal changes as part of a protective adaptation to overcome extreme environmental conditions and to increase uptake of oxygen by cutaneous respiration.

• Korean Journal of Environmental Agriculture
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• v.21 no.1
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• pp.50-56
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• 2002

This experiment was carried out to obtain some information about overwintering, physiological and ecological characteristics of apple snails. Another purpose of this experiment was to characterize an appetite for rice plants by apple snails and to elucidate their choice of fresh green ones (vegetables, some other crops, weeds in rice fields). The freshwater snails were found with higher population at sites abundant organic compounds such as plant debris and at regions with high temperature. They also prefer calcium-rich water. This is a naturally occurring process. Apple snails were exceptionally veil-adapted to the south regions of Korea, especially Janghang, Jangseong and Haenam, even if the temperature of winter season is cold below 0$^{\circ}C$. Apple snails were not very selective in their food choice and eat almost everything available in their environment. A snail have something called a radula in its mouth for grinding up its food. A apple snail also chews on fruits and young succulent plant barks. In case of reproduction. apple snails deposit about 157$\sim$784 (average of 321 eggs) milky white to pale orange colored eggs above the waterline. In approximately every 22.4 seconds a new egg appears. The total time needed to deposit a egg mass varies from 58 minutes$\sim$4 hours 13 minutes. Apple snails reproduct actively from May to June and from September to October. An appetite of apple snails for rice plants was the different depending on their size and glowing stage for rice plants. Apple snails had a great appetite of rice plants as well as dropwort, tomato, cabbage, radish, aquatic plants etc. They preferred to eat young rice plants and drastically quit eating rice plants of over 40 cm in height. Thus considering the food preference of apple snail for various plants including rice, they were thought to be a potentially strong predator in fields, especially, at regions with warmer winter.