Aktivitas Poros Pineal - Hipotalamus-Gonad pada Ikan Nilem (Osteochilus hasselti C.V.) di Bawah manipulasi Fotoperiode : Kajian Selular dan Molekular

Norman Arie Prayogo, Dr. Pudji Astuti, M.P,

2012 | Disertasi | S3 Bioteknologi

Reproduksi ikan dipengaruhi oleh fotoperiode melalui pengaturan aktifitas kelenjar pineal dalam memproduksi hormon yang digunakan dalam pertumbuhan dan perkembangan gonad, gametogenesis, dan siklus reproduksi. Penelitian ini bertujuan untuk mengkaji kemampuan reproduksi ikan nilem yang dipelihara dengan berbagai fotoperiode. Penelitian ini dilaksanakan menurut rancangan acak lengkap dengan empat perlakuan fotoperiode yaitu 14L:10D, 16L: 8D and 18L:6D dan kontrol. Pada setiap perlakuan disediakan 4 bak pemeliharaan masing-masing berisi 9 ekor ikan. Ikan dipelihara selama 4 bulan, data diambil setiap bulan. Variabel penelitian adalah aktivitas poros pineal-hipotalamus-hipofisis-gonad pada ikan nilem. Aktivitas pineal diamati dengan mengukur fluktuasi melatonin dengan menggunakan ELISA, aktivitas hipotalamus dievaluasi dengan mengukur ekspresi gen cGnRH-II dan sGnRH dengan menggunakan Real Time PCR, dan aktifitas gonad dievaluasi dengan mengukur indeks kematangan gonad (IKG) serta kadar estradiol dengan menggunakan ELISA. Pada penelitian ini untuk pertama kalinya didapatkan genomik cGnRH-II (632 bp) dan sGnRH (486 bp), dan cDNA cGnRH-II (253 bp) dan sGnRH (285 bp). Kadar melatonin ikan nilem secara signifikan (P<0,05) menurun dari bulan ke-0 hingga bulan pertama dan terdapat perbedaan signifikan antara setiap kelompok perlakuan (P<0,05). Ekspresi gen cGnRH-II and sGnRH pada setiap kelompok perlakuan cenderung meningkat sesuai dengan lama waktu pemelihraan (P<0,05) dan terdapat perbedaan yang nyata antar kelompok perlakuan fotoperiode. Pola yang sama juga didapatkan pada kadar 17β-estradiol (P<0,05). Hasil ini mengindikasikan bahwa fotoperide bersifat stimulatori terhadap kemampuan reproduksi pada ikan nilem.

Fish reproduction is influenced by photoperiods through regulation on endocrine gland activities in producing hormones necessary for gonadal growth and development, gametogenesis and reproductive cycles. Research needs to be conducted to find out nilem’s reproductive performance by manipulating photoperiod. Design experimental with four photoperiod treatments namely 14L:10D, 16L: 8D and 18L:6D and control were conducted. Four aquaria consisting of nine fishes each were served as replicates. Fishes were kept under these photoperiods for 4 months. The observed variable was the end point pineal-hyphothalamus-hipofisis-gonad axis activities. Pineal activity was evaluated by measuring melatonin, hypothalamus activity was evaluated by measuring gene expression of cGnRH-II and sGnRH using Real Time PCR, Gonadal activity was evaluated by measuring Gonado somatic index (GSI), and serum level of estradiol was assayed using ELISA. Two Genomic DNA GnRH and cDNAs of Hard-lipped barb, namely GnRH-II and GnRH-III, were cloned from the brain reverse transcription- polymerase chain reaction (RT-PCR). The length of genomic DNA cGnRH-II was 632 bp and cDNA cGnRH-II was 253 bp, the length of genomic DNA sGnRH was 486 bp and cDNA sGnRH was 285 bp. The average of melatonin in each experimental group significantly decreased according to time (P<0.05) and there was significantly different was observed between each experimental groups. The average of cGnRH-II and sGnRH in each experimental group significantly increased according to time (P<0.05) and there was significantly different was observed between each experimental groups. Similar patterns were also observed for estradiol serum (P<0.05). These results indicated that stimulatory effect of extended photoperiod have been proven in improving nilem reproductive performance.

Kata Kunci : Fotoperiode, melatonin, cGnRH, sGnRH, estradiol, dan ikan nilem