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Monthly Gonadal and Sex Hormonal Changes of Indoor-Reared Seabass, Lateolabrax japonicus during Annual Reproductive Cycle

실내사육 농어, Lateolabrax japonicus의 생식소 및 성호르몬의 주년 변화

  • 강덕영 (국립수산과학원 거제수산종묘시험장) ;
  • 한형균 (국립수산과학원 거제수산종묘시험장) ;
  • 백혜자 (부경대학교 해양생물학과)
  • Published : 2002.11.01

Abstract

The sea bass, Lateoiabrax japonicus is a highly valued fish in aquaculture in South Korea. For establishment of seedling production of sea bass,1 japonicus, we examined change of gonadal development and plasma steroid levels of sea bass reared in indoor tank. Male matured unsimultaneously faster than females and spawning of females took place between the end of January and March. After the spawning period, and until the following January, all the females were in preyitello genesis and in some males, spermatogenetic activity restarted gradually. In October, under reducing photoperiod, cortical alveoli appeared in growing oocyte and the development of spermatogenesis greatly increased. Between October and february, vitellogenesis and spermatogenesis occurred respectively in female and male and gonadosomatic index increased from 4.31 to $24.07\%$ in female and upper 6o/o in male. Also, two sex hormones were analyzed during the course of a reproductive cycle in the sea bass: plasma levels of the gonadal steroid testosterone (T) and estradiol-l7$\beta$ (E_{2}). Variation of the plasma concentrations of T and E, appeared to depend on gonad stages. Plasma T and E, levels were high from November to January, suggesting that an sufficient gonadal stimulation by both hormones may undergoing a processes for the formation of sperm and oocyte.

본 연구는 3년생 양식 가두리산 어미를 실내 수조로 옮긴 뒤 연중 생식소와 호르몬의 주년 변화를 파악하기 2년 동안 매달 샘플을 실시하였다. 형태학적 내분비학적 분석 결과 수컷은 암컷에 비해 앞서 성숙이 진행되고, 산란은 1월말에서 3월 사이에 이루어졌다. 산란기 이후 다음해 1월까지 모든 암컷은 난황형성 이전 단계에 머물러 있었고, 수컷 중 일부는 정자형성 활성을 다시 나타내기 시작했다. 10월에 접어들면서 일조량의 감소와 함께 성장 중인 난모세포에서 cortical alveoli이 나타나기 시작하고, 정자 형성이 점차 늘어났다. 10월과 2월 사이 암컷은 vitellogenesis, 수컷은 spermatogenesis가 일어나며, 난소 성숙지수는 암컷이 4.3$\~$$24.1\%$, 수컷은 $6\%$ 이상으로 증가하였다. 그리고 산란력 평가를 통해 농어는 다른 해산어류와 유사한 산란 전략을 지니고 있었으며, 다회산란의 특성을 지니고 있었다. 또한 농어의 생식기 과정동안에 이루어진 성호르몬인 testosterone (T)과 estradiol-17$\beta(E_{2})$ 의 분석 결과 생식기 발달에 따른 농도의 변화가 있는 것으로 확인되었다. 특히 11월에서부터 2월까지 높은 혈중 T와 $E_{2}$의 농도는 이 시기 수컷의 정자형성과 난소의 성숙란 형성에 있어 이들 호르몬의 관련성이 확인되었다. 이상의 결과로 양식산 농어의 생식기능은 실내 수조에서 발현이 되며, 따라서 인공종묘생산에 필요한 수정란 생산이 실내 수조에서 가능하다고 할 수 있다.

Keywords

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