JP2004049159A - Method for producing male daphnia magna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for easily and efficiently producing male Daphnia magna. <P>SOLUTION: Male Daphnia magna is produced by breeding the female Daphnia magna while varying the environmental conditions, especially the light-dark cycle frequency and feeding rate. The light-dark cycle is shortened and the feeding rate is decreased. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Industrial applications]
The present invention relates to a method for producing a male Daphnia magna, which is used in a study for evaluating the effects of general chemicals, pesticides, natural products, and the like on ecosystems.
[0002]
[Prior art]
Although Daphnia magna has been used in toxicity evaluation tests without discriminating between males and females, recently, various chemical substances have been attracting attention as environmental hormones, and the development of a test system that differentiates between males and females of experimental organisms is expected. It is rare.
In general, daphnids usually produce only females due to parthenogenesis, but males appear when environmental conditions deteriorate. For example, a decrease in water temperature, deterioration of the bait environment, and a short-period light cycle (Takayuki Hanari, 1998, Daphnia magna, Nagoya University Press). It is also known that Daphnia magna is usually a long-day cycle, and when environmental conditions are favorable, only females are produced due to parthenogenesis, and that males are born due to changes in environmental conditions. (Anders Hobaek and Peter Larsson, 1990, Ecology 71 (6), pp. 2255-2268).
For use in biological tests, a large number of male individuals are required simply and efficiently at certain times. However, according to conventional knowledge, it was difficult to obtain a male at a time when it could be accurately predicted. In addition, a simple method for simultaneously obtaining a sufficient number of males for use in biological tests has not been found.
In addition, in order to compare with a female by a biological test, an individual within 24 hours after birth is required. The sex of Daphnia is mainly determined by the shape of the first antennae, but cannot be determined by the naked eye and requires microscopic observation. It is therefore very useful to be able to predict when a born individual will be male.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to provide a production method capable of stably securing a large amount of Daphnia magna used for research for evaluating the effects of general chemical substances, pesticides, natural products, and the like on ecosystems.
[0004]
[Means for Solving the Problems]
The present invention relates to a method for producing a male Daphnia magna (Daphnia magna), characterized in that the female Daphnia magna (Daphnia magna) is bred by changing the environmental conditions of the Daphnia magna, in particular, the light-dark cycle and the amount of feeding. And a method of reducing the amount of feed.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
Male production is performed as follows.
Larvae born from females that were bred under normal breeding conditions, that is, given a sufficient diet (single-cell green algae, yeast, etc.) on a long day cycle (lighting time of 12 hours or more), and that were healthy and repeated parthenogenesis (All females under these conditions) are placed in individual containers and are kept in normal rearing water (dechlorinated tap water, natural water, artificially prepared water, etc.) at an optimum temperature (15 to 25 ° C) under a long day cycle. Feed and rear. Under this condition, the first larva is usually produced within 10 days, and thereafter, the production is repeated every 2 to 3 days. To obtain males, at any time from one day before to one day after any birth, larvae born are removed and a short circadian cycle with reduced food concentrations. Due to this condition change, at least the next half of males can be obtained at the time of the second birth (the next next birth), and almost 100% of males can be obtained in some cases.
The period for reducing the food concentration is usually preferably 1 to 4 days, and the food concentration may be reduced by stopping the feeding.
[0006]
【Example】
Hereinafter, the present invention will be described specifically with reference to examples, but the scope of the present invention is not limited to the examples.
Example 1
Females born due to parthenogenesis were individually housed in glass containers and bred (breeding density: 1 individual / 50 mL of dechlorinated tap water, lighting: 16 hours light 8 hours dark, water temperature 20 ° C.). The animals were observed daily, the breeding water was changed every few days, and a sufficient amount of green algae and yeast were fed every day. After the first larval production, the larvae were removed, the breeding water was replaced, and a sufficient amount of food was given. Then, the lighting time was changed to 8 hours light 16 hours dark. Feeding was then stopped for 4 days. Due to this change in conditions, the larvae produced for the third time were 44 males and 45 females in total in four cases.
[0007]
Example 2
As in Example 1, females born due to parthenogenesis were individually housed in glass containers and bred (breeding density: 1 individual / 50 mL of dechlorinated tap water, lighting: 16 hours light 8 hours dark, water temperature 20 ° C.) ). The animals were observed daily, the breeding water was changed every few days, and a sufficient amount of green algae and yeast were fed every day. After the first larva was removed, breeding was continued, and after the second larva was produced, the lighting time was changed to 8 hours, 16 hours to dark, the breeding density was changed to 1 individual / 40 mL, Feeding was stopped for 3 days and for the other 3 animals for 4 days. Due to this change in conditions, the larvae produced for the fourth time were 82 males and 1 female in total in the four cases.
[0008]
【The invention's effect】
According to the present invention, a large number of male Daphnia magna can be easily and efficiently provided at a time, and thus can be used in studies for evaluating the effects of general chemicals, pesticides, natural products, etc. on ecosystems.

Claims (5)

A method for producing a male Daphnia magna, characterized by rearing with varying light-dark cycle and feeding amount. The production method according to claim 1, wherein the light-dark cycle is shifted to a short-day cycle, and the feed amount is reduced. The production method according to claim 1 or 2, wherein the feed concentration reduction period is 1 to 4 days. The production method according to any one of claims 1 to 3, wherein the feed amount is 0. 5. The production method according to claim 1, wherein the light-dark cycle is 6 to 9 hours light, 18 to 15 hours dark, and the feed amount is 0.