"A New Quantitative Evaluation Technique (Fragmented Method) for Detection of Testis-Ova in Medaka (Oryzias latipes) " 

Lin Bin-Le¹, Satoshi Hagino², Michio Kagoshima², Shouji Ashida², Akihiro Tokai¹, Kikuo Yoshida¹, Yoshitaka Yonezawa¹, Mamoru Tominaga¹, Junko Nakanishi¹

¹National Institute of Advanced Industrial Science and Technology
²Sumika Technoservice Corporation

6th International Symposium on Environmental Endocrine Disrupters 2003 Program (Sendai, Japan 2003/12/2)

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Abstract

A new quantitative evaluation method named as fragmented method for detection of testis-ova in male fish using medaka (Oryzias latipes) S-rR strain has been developed. 

Current histological method has been still applied to detect the testis-ova in fish exposed to estrogenic or suspected endocrine disrupting chemicals, even though some of the disadvantages, such as an oversight in the testis-ova due to observation in the limited area of the testis, are obviously indicated. 

The fragmented method we developed is exactively capable of determining number and the developmental stages (size) of oocytes in a whole testis. The testis from the specimen fixed with formalin solution was broken into small fragments with a dissecting needle and aciform forceps in glycelin solution containing small amount of methylene blue, etc. on a slide glass.

 All developing oocytes of various sizes were clearly stained and thereby were observable if present under a dissecting microscope. Spermatozoa were also distinguishable in this method.

 In conclusion, this method not only demonstrated as a convenient and cost-effective method for quantitatively detecting testis-ova appearance in fish, but also is expected to contribute the understanding of testis-ova and the biological significances in the future studies for endocrine disruption. 

Keywords

New Quantitative Evaluation Technique, Fragmented Method, Testis-Ova