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REPRODUKSI

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REPRODUKSI

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  1. REPRODUKSI

  2. Gonad : ♀ ovarium : menghasilkan sel telur ♂ testes : menghasilkan sperma • Proses pematangan telur berupa perubahan struktur, kedudukan, sitoplasma, dan mencakup kematangan fungsi dan fisiologis. • Sitoplasma akan menjadi tempat cadangan makanan : kuning telur (egg yolk) dan butiran minyak (oil globule) • Chorion : lapisan pembungkus telur paling luar • Pada chorion terdapat lubang sempit sbg pintu masuk spermatozoa ke dalam telur, disebut micropyle • Spermatozoa masuk hanya kepalanya (inti) saja • Setelah itu micropyle menutup untuk menghalangi masuknya sperma lain. • Setelah telur dilepas ke dalam air dan dibuahi, chorion akan mengeras untuk melindungi embrio yang masih sangat sensitif

  3. Fig.4.General pattern of development of sexual products in fishes

  4. Perkembangan telur melalui beberapa tahap, a.l: (contoh pada ikan Mas) Stage I: The primitive egg cells (ovogonium or archovogonium) are very small, their size being hardly bigger than that of other cells (8–12 microns). They multiply by normal mitosis. Stage II: The egg cells grow to a size of 12–20 microns, and a follicle begins forming around each egg cell. The follicle, whose function is to nurture and protect the developing egg, eventually becomes a double layer of cells. Stage III: During this stage, the egg cell grows significantly larger to attain a size of 40–200 microns and becomes enclosed by the follicle. These first three stages mark the period prior to the accumulation of nutrients in the developing eggs.

  5. Stage IV: During this stage the production and accumulation of the yolk begins; this is a process known as vitellogenesis. The egg continues to grow to a size of 200–350 microns with the accumulation of drops of lipoid materials in its cytoplasm. Stage V: This marks the second phase of vitellogenesis. The cytoplasm is now full of lipoid drops and yolk production begins. The egg size reaches 350–500 microns. Stage VI: This is the third phase of vitellogenesis, during which the yolk plates push the lipoid drops toward the edge of the cell where two rings begin forming. The nucleoli, which take part in protein synthesis and the accumulation of nutrients are seen adhering to the membrane of the nucleus. The size of the egg is now 600–900 microns. Stage VII: The process of vitellogenesis is completed during this stage and the egg attains a size of 900–1 000 microns. When the yolk accumulation ends, the nucleoli withdraw into the centre of the nucleus. The micropyle (a small opening on the egg shell) develops during this stage.

  6. Stages IV, V, VI, and VII are the stages of vitellogenesis, when yolk is synthesized and accumulated in the egg cell. The egg is now materially ready. To reach this stage of development, the female fish needs a lot of protein in its food and a favourable temperature range. On the completion of stage VII, the egg may remain as such for several months without any change, and this forms the “dormant” or “resting” phase. This resting or dormant phase will either end in ovulation if favourable conditions occur, or in follicular putrefaction and resorption in the absence of such conditions (Figure 6).

  7. Figure 5. Environment and maturation of fish eggs

  8. Figure 6.The fate of developing eggs

  9. Figure 7 The course of natural spawning • Figure 7 The course of natural spawning • Figure 7 The course of natural spawning Figure 7 The course of natural spawning

  10. PerkembanganEmbrioIkan • Cleavage : pembelahanzigot sec cepatmenjadi unit selyglebihkecil • Blastulasi : prosesygmenghasilkan blastula, yaitucampuransel-selblastoderm yang membentukronggapenuhcairansebagaiblastocoel. • Gastrulasi : prosespembelahanbakal organ yang sudahterbentuk pd saatblastulasi. • Organogenesis : prosespembentukanberbagai organ tubuh. Berbagaimacam organ terbentukdaribeberapabakal organ yang terbentuksaatgastrulasi. -Usus, ronggakupffer, subnotochord rod : dari endoderm -Notochord,jantung,ginjal,gonad,sirip dada : dari mesoderm -Insang, linealiteralissertalipatan-lipatansirip : dariektoderm