PERKEMBANGAN SALURAN DAN SISTEM PENCERNAAN PADA LARVA IKAN TUNA SIRIP KUNING, Thunnus albacares (Bonnaterre, 1788)

Abstract

Penelitian ini bertujuan untuk mengetahui perkembangan saluran dan sistem pencernaan pada larva ikan tuna sirip kuning Thunnus albacores (Bonnaterre, 1788). Sampel larva diambil setiap hari dari larva baru menetas (D-0) sampai D-13, dan selanjutnya dilakukan sampling pada D-15 dan D-20. Semua sampel di foto dengan program ACT-1 dan diproses secara histologi. Hasil pengamatan menunjukkan larva D-0 belum memiliki saluran pencernaan, mulut, dan mata belum terbuka. Pada D-1 saluran pencernaan mulai terbentuk, tetapi masih dalam bentuk tabung lurus. Mulut larva mulai terbuka pada D-2 (45 jam setelah menetas pada suhu air pemeliharaan 28°C). Kuning telur sudah diserap sepenuhnya pada D-3, saluran dan organ pencernaan seperti mulut, esofagus, lambung, ginjal, hati, pankreas, usus, rektum, dan anus sudah terbentuk. Pada D-5 mulai muncul mikro philli pada usus untuk mengabsorbsi nutrisi. Sel-sel penyusun hati, jantung, saluran pencernaan sudah tumbuh dan berkembang menyerupai organ ikan dewasa, ditandai adanya pakan dalam usus. Saluran dan sistem pencernaan telah berdiferensiasi menjadi organ dalam seperti pada ikan dewasa pada hari ke-6 (D-6) dan akan sempurna pada D-20 dengan TL ± 2 cm. Berdasarkan perkembangan pencernaan, maka pakan awal berupa rotifer sebaiknya diberikan pada hari ke-2 (43 jam setelah menetas pada suhu air 28°C).The aim of this study was to observe the development of tract and digestive system on yellowfin tuna larvae. Tuna larvae were collected daily from rearing tank at hatching day 0 (D-0) to 13 (D-13). Samples of larvae were selected at D-15 and D-20. All samples were observed under light microscopy, documented and then histologically processed. The results showed that the digestive tract began to form on the larvae at day-1 which was still in the form of a straight tube. The mouth of the larvae starts to open on D-2 (45 hours after hatching at a water temperature of 28°C). At D-3, the larvae’s yolk sac was fully absorbed, and its intestine contained a single type of food which was rotifer. The digestive tract and internal organs were formed such as the mouth, esophagus, stomach, kidney, liver, pancreas, intestine, rectum, and anus which indicated that the larvae can eat and digest food. At D-5, microvilli began to develop in the intestine to absorb nutrients. The cells of the liver, heart, digestive tract had grown and evolved to resemble that of mature fish organs characterized by feed in the gut. The tract and digestive system have differentiated into internal organs such as in adult fish at D-6 and fully developed in D-20 with TL ± 2 cm. Based on the present finding, it is suggested that the initial feeding of tuna larvae using zooplankton (rotifer) could be done at day two (43 hours) post-hatching at a water temperature of 28°C.