바다 송사리 Oryzias dancena의 번식과 발생에 미치는 스테로이드 및 내분비계 장애물질의 영향

Abstract

For induction of an infertile population and monosexual development in the marine medaka Oryzias dancena, which is believed to keep ecosystems from being biologically polluted, the effects of known inducers such as steroids and endocrine disrupting chemicals on the two reproductive and development events were studied in three salinities (0, 15 and 30 psu). The steroids and endocrine disrupting chemicals used for the induction of an all-female population were 17α-ethinylestradiol (EE2), diethylstilbestrol (DES), 17β-estradiol (E2) and estrone (E1) for the submerging induction of eggs. Steroid E2 and endocrine disrupting chemicals bisphenol-A (BPA), octylphenol (OP) and nonylphenol (NP) were used as infertility inducers and administered orally.

1. Induction of monosexual development In the induction of the all-female population for four weeks from fertilized eggs to two weeks after hatching in salinity ranging from 0-30, treatments of EE2 0.1-100.0 ㎍/L, DES 0.1-100.0 ㎍/L, E2 0.1-100.0 ㎍/L and E1 0.2-2.0 ㎍/L at 0 psu and E1 20.0 ㎍/L at 15 psu showed a hatching rate over 50%. The lower concentration of steroid and chemicals induced higher hatching rates: treatments EE2 0.1 ㎍/L, DES 0.1 ㎍/L and E2 10.0 ㎍/L at 0 psu exhibited a hatching rate over 80%. In higher salinity, 30 psu, a strong chemical reaction between vehicle ethanol and NaCl inhibited the normal hatching process: 0% for vehicle control and 0-3.3% for chemical treatment groups which were extremely low compared with intact control. The larval mortality of the fish treated with different steroids and chemicals was highly dependent on salinity. Fish larvae showed higher mortalities in higher salinities. Treatments of EE2 0.1-10.0 ㎍/L, DES 0.1-100.0 ㎍/L, E2 1.0-10.0 ㎍/L and E1 0.2, 20.0 ㎍/L at 0 psu and E1 0.2 ㎍/L at 15 psu showed agreeable larval mortality at around 20%, while the treatments at 30 psu revealed total mortality.

In 78 days after hatching, all the larval fish treated with EE2 0.1-100.0 ㎍/L, DES 10.0-100.0 ㎍/L, E2 1.0, 100.0 ㎍/L and E1 0.2, 20.0 ㎍/L at 0 psu exhibited an all-female population. None of the steroid treatments at salinity 15 psu showed total female monosexuality. Submerging treatments showing over 50% hatching rates, less than 20 % early mortality, and 100% monosexuality were achieved in combined treatments consisting of EE2 0.1-10.0 ㎍/L, DES 10.0-100.0 ㎍/L, E2 1.0 ㎍/L and E1 0.2 ㎍/L at 0 psu during the experiment period of four weeks from fertilized eggs to two weeks after hatching. Among them treatment EE2 0.1 ㎍/L at 0 psu was best showing an over 80% hatching rate, less than 20 % early mortality, and total monosexuality.

2. Induction of infertile population The female spawners marine medaka were orally administrated with E2 and different endocrine disrupting chemicals at salinity ranging from 0 to 30 psu for 42 days. During the last 14 days of the total treatment period, a lower spawning amount of about 200 was obtained from the treatments of BPA 2.0-20.0 ㎎/g, OP 20.0 ㎎/g and NP 20.0 ㎎/g at 0 psu, and BPA 20.0 ㎎/g, OP 20.0 ㎎/g and NP 20.0 ㎎/g at 30 psu. The best results with spawning amount 0 were from treatments of OP 20.0 ㎎/g and NP 20.0 ㎎/g at 0 psu and NP 20.0 ㎎/g at 30 psu. The infertile effects of the chemical treatments began from day 11 for OP 20.0 ㎎/g and day 8 for NP 20.0 ㎎/g at 0 psu, and from day 20 for NP 20.0 ㎎/g at 30 psu with no further spawning process thereafter. Less than 60% fertilization rates during the last 14 days of the total treatment period were observed in E2 1, 10 ㎍/g at 0 psu and OP 20.0 ㎎/g at 30 psu. Fertilization rates from treatments of OP 20.0 ㎎/g and NP 20.0 ㎎/g at 0 psu and NP 20.0 ㎎/g at 30 psu could not be calculated due to the spawning amount being 0. The mortalities of spawners treated with E2 or other endocrine disrupting chemicals at 0 salinity or 30 psu ranged from 0 to 8.3% in tests for E2 1, 10 ㎍/g, BPA 0.2-2.0 ㎎/g, OP 0.2 ㎎/g and NP 2.0 ㎎/g at 0 psu, and for BPA 0.2-20.0 ㎎/g, OP 0.2-2.0 ㎎/g and NP 0.2-20.0 ㎎/g at 30 psu. The results suggest that treatments of OP 20.0 ㎎/g and NP 20.0 ㎎/g at 0 psu and NP 20.0 ㎎/g at 30 psu were agreeable for the induction of infertile spawners. The oral administration of NP 20.0 ㎎/g at 30 psu was best in terms of the mass production of infertile populations with less than 8.3% spawner mortality.

In conclusion, the present study provides methodology for the best induction of a monosexual and infertile population of marine medaka by submersion and oral administration of steroids and endocrine disrupting chemicals which are believed to be biologically safe in an open ecosystem.