Ultrastructure of Germ Cells, Cyst Epithelial Cells and Interstitial Cells during Spermatogenesis of the Stone Flounder, Kareius bicoloratus

돌가자미 Kareius bicoloratus의 정자형성과정 중 생식세포, Cyst 상피세포 및 간질세포의 미세구조

  • Jun, Je-Cheon (West Sea Fisheries Research Institute, National Fisheries Research and Development Institute) ;
  • Chung, Ee-Yung (School of Marine Life Science, Kunsan National University) ;
  • Yang, Young Chul (Department of Anatomy, Yonsei University Wonju College of Medicine)
  • 전제천 (국립수산과학원 서해수산연구소) ;
  • 정의영 (군산대학교 해양생명과학부) ;
  • 양영철 (연세대학교 원주의과대학 해부학교실)
  • Received : 2006.10.31
  • Accepted : 2006.12.07
  • Published : 2006.12.31

Abstract

Ultrastructure of germ cells, the cyst epithelial cells and interstitial cells during spermatogenesis of the stone flounder, Kareius bicoloratus (Pleuronectidae) sampled on the west coast of Korea were investigated by electron microscopic observations. In the primary spermatocyte, the synaptonemal complexes appear in the zygotene stage of the prophase during maturation division. In the growing testis, especially, the interstitial cells (Leydig cells) appear near the primary, secondary spermatocytes and spermatids. Well-developed interstitial cells (steroid hormone secreting cells) which are located in the interlobular space in growing testis have three morphological characteristics of a vesicular nucleus, mitochondria with tubular cristae and smooth endoplasmic reticulum. During spermatogenesis, the primary and secondary spermatocytes attach to the cyst epithelial cell (Sertoli cell) having an elongated ovoid or triangular nucleus and several mitochondria in the cytoplasm. In the growing testis, lipid droplets, the mitochondrial rosettes and glycogen particles appear in the cytoplasm of the cyst epithelial cells near the secondary spermatocytes and spermatids. Particularly, the mitochondria, endoplasmic reticulum, little lipid droplets and the large amount of glycogen particles are present in the cytoplasm of the cyst epithelial cell in the late growing testis. In the late stage of spermiogenesis, the proximal centriole is joined to the nuclear envelope, the distal centriole forms the basal body of the flagellum and gives rise to the axial filament of the flagellum. No acrosome of the sperm is formed as seen in other teleost fish. The head of the spermatozoon is approximately $3{\mu}m$ in length and its tail is about $30{\mu}m$ in length. The axoneme of the tail flagellum of the spermatozoon consists of nine outer doublet microtubules at the periphery and two centrial singlet microtubules at the center. The spermatozoon of this species has two axonemal lateral fins. Especially, the cyst epithelial cells which located near groups of gametes in the various stages, show three functions: nutrition, phagocytosis and steroidogenesis. Especially, the nuclei of cyst epithelial cells in the recovery stage of the testicular developmental stages appear to be irregular in shape after spermiation. Of three functions of the cyst epithelial cell, several characteristics of phagocytosis are showed in the cytoplasm of the cyst epithelial cells in the recovery stage of the testicular developmental stages. At this stage, therefore, it is assumed that the cyst epithelial cells are involved in degeneration and resorption of undischarged germ cells after spermiation.

한국 서해안에서 채집한 돌가자미 Kareius bicoloatus의 정자형성과정 중 생식세포, Cyst 상피세포 및 간질세포들의 미세구조를 전자현미경 관찰에 의해 조사하였다. 제1차 정모세포에서 연접사복합체(synaptonemal complex)들이 성숙분열 중 전기의 쌍사기에 출현하였다. 특히, 감수분열을 위한 테스토스테론 호르몬을 분비하는 세포로 알려진 간질세포(Leydig cell)들은 제1차 정모세포 및 정세포 가까이에서 뚜렷하게 출현하였다. 포상핵을 가지는 이들 간질세포들은 소엽 간 간질조직 내의 섬유모세포들에 의해 둘러싸여 출현하였다. 특히, 이들 세포들은 타원형 또는 구상의 미토콘드리아들을 가지는데, 미토콘드리아들은 관상 크리스테(cristae)를 갖는 것이 특징이다. 또한, 활면소포체와 여러 개의 공포들도 세포질 내에서 출현하였다. 성장 발달 중인 정소 내에서 정소소엽 간 간질조직에서 나타나는 잘 발달된 간질세포들(스테로이드호르몬분비세포)은 포상의 핵과 관상 크리스테를 갖는 미토콘드리아를 가지며, 활면소체를 갖는 형태적 특징을 보였다. 정자형성과정 중, 제1차, 제2차 정모세포들은 cyst 상피세포 (Sertoli cell)들에 인접하거나 부착하여 나타났다. cyst 상피세포들의 핵은 길게 신장된 타원형 또는 삼각형의 핵을 가지며 세포질 내에 여러 개의 미토콘드리아가 출현하였다. 성장 발달 중인 정소 내에서 제2차 정모세포들과 정세포 가까이에 위치한 cyst 상피세포의 세포질 내에는 지방적, 미토콘드리아 로제트(mitochondeial rosettes)들과 글리코겐 입자들이 나타났다. 특히, 후기 성장 중인 정소 내에서 cyst 상피세포의 세포질 내에는 미토콘드리아, 소포체, 작은 지방적 및 다량의 글리코겐입자들이 출현하였다. 정세포 발달(정자변태) 후기에 기부중심립이 핵막에 부착하며, 원위중심립은 편모의 기저체를 형성하고, 편모축사를 형성하였다. 정자 첨체는 다른 경골어류에서와 같이 첨체를 형성하지 않았다. 정자 두부의 길이는 대략 $3{\mu}m$ 정도이며, 미부길이는 약 $30{\mu}m$ 정도이다. 정자 미부편모의 축사(axoneme)는 주변에 9쌍의 주변이중미세관 (nine outer doublet microtubule)이 있고 중앙에 두 개의 중앙미세관(two centrial singlet microtubules)으로 구성되어 9+2구조를 나타내었다. 본 종의 정자는 체외수정 종들이 갖는 두 개의 axonemal lateral fin을 가진다. 본 연구에서 여러 단계의 생식세포들 가까이에서 출현하는 cyst 상피세포(Sertoli cell)들은 영양공급, 식세포작용, 스테로이드형성의 3가지 기능을 나타내었다. 특히, 정소 발달단계 중 퇴화 회복기에 출현하는 cyst 상피세포들의 핵은 배정 후에는 모양이 불규칙하게 나타나며, 식세포작용을 나타내는 여러 특징들이 cyst 상피세포의 세포질 내에서 나타나고 있어, cyst 상피세포들은 배정 후 방출되지 않은 생식세포들의 퇴화 흡수에 관여하는 것으로 추정된다.

Keywords

Acknowledgement

Supported by : National Fisheries Research and Development Institute

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