The karyotype of the orange-red variety or the d-rR strain of the medaka, Oryzias latipes, was first investigated by 0 j ima and Hitotsumachi (1969) possible to obtain a number of ideal metaphase figures and to demonstrate the characteristic banding patterns in fish chromosomes. In the present study, a detailed karyotype study was undertaken with the application of differential staining techniques, use being made of fin-cultures.Materials and methods. Wild and orange-red varieties of the medaka (Oryzias latipes) were subjected to this study. Wild fishes were collected at Matsuyama, Ehime Prefecture.For the orange-red varieties, the d-rR strain established by Yamamoto (1953) and the domestic himedaka were used as material.Fin-cultures were set up following the method of Hayashi et al. (1976). One or several specimens were used in every culture. The posterior parts of caudal fins were removed from anaesthetized fishes and sterilized by immersion in 1 % sodium hypochlorite for a few seconds, followed by flush dipping in 70% ethanol. They were washed three times with PBS(-) for 10 mins each. Fins were transferred to a flask containing 5 ml of trypsin solution (0.1% trypsin in PBS (-)).Cells were liberated by low speed stirring at 4°C for 2 hrs. Liberated cells were collected by centrifugation at 1000 rpm for 5 mins, suspended in L-15 medium, and inoculated into a plastic
The loach, Misgurnus anguicaudatus, is a common fresh water teleost having a wide distribution in Japan. They easily breed in captivity, and are largely domesticated in small ponds for food.Oj ima and Hitotsumachi Hitotsumachi et al. (1969) reported the chromosomal morphology of this species with some cytophotometric data on the amount of DNA. It was shown that the chromosome number was 2n=50 consisting of 7 pairs of meta-and submetacentric type, and 18 pairs of telo-and subtelocentric type. Recently we had chanced to find unexpectedly the occurrence of polyploid specimens in the Japanese common loaches which were obtained in the market and the field.
Materials and methods.Thirteen individuals were collected from the Chinai river of Shiga prefecture in Japan, and 67 specimens were obtained in the market.For chromosome study, kidneys were freshly removed, minced with scissors and isolated cells were cultured with MEM for 2 hrs. They were treated with colchicine solution at the dosage of 0.5 ~g/ml for 2 hrs. Following KC1-hypotonization (0.068 M) for 20 min, and Carnoy-fixation as usual, slides were air-dried and Giemsa-stained.In order to carry out the cytochemical studies on diploid, triploid and tetraploid loaches, liver tissue was fixed with Carnoy's solution, embedded in paraffin, and cut at 8-10 a in thickness required for microspectrophotometry.DNA amount was estimated in individual nuclei and division figures by Feulgen cytophotometry (Olympus DMSP-1) using the two wave-length method after Ojima and Yamasaki (1968).
Results and remarks.Of the eighty specimens karyotyped, 4 (~ 3, 1) were tetraploid with 4n=100, while 1(~) was triploid with 3n=75. The diploid chromosome complement was 50 in number consisting of 5 pairs of metacentrics, 2 pairs of submetacentrics, and 18 pairs of telo-and subtelocentrics (Fig. 1). A polymorphism was found to occur in the population of diploid
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