Spawning of Siamese crocodile, Crocodylus siamensis Schneider
1994
Khemchart Nimsomboon (Nakornsawan Inland Fisheries Development Center (Thailand))
Siamese crocodile (Crocodylus siamensis Schneider, 1801) is a large reptilian of the family Crocodylidae. Siamese or freshwater crocodile is the same genus of estuarine crocodile (Crocodylus porosus Schneider, 1801). This species had been abundance throughout the wetlands of the Central Thailand and Mekong River, espectually in Boraped Swamp (Nakornsawan province). The differenciate between Siamese crocodile and estuarine crocodile is the presence of four post occipital scales of the former. The species reaches maturity at 8-10 years old. The male present a penis whereas absent in female, This study, there are 12 brooders (10 years old, 8 female and 4 male) reared in 4 cement ponds (5*10 m). The stocking rate was 1:2 (male:female) per pond. The result showed that the spawning period of Siamese crocodile started in February to March, 1993. The couples has mating submerge behaviour all day. Female lay eggs in April until May 1993. Mating period usually occur at 2-5 AM. Female give 32-36 eggs per clutch. Egg sizes 7.71+-0.11 cm long, and weighing 94.06+-1.57 g Fertiled eggs show an opaque band circumferencially. The eggs were transferred to incubation cement tank within 24 hours under temperature 31.67+-3.12 deg C in tank 1 and 32.8+-2.53 deg C in tank 2 Relative humid 86.07+-1.16 percent in tank 1 and 86.75+-3.08 in tank 2. Study on developments of crocodile show that nervous system, digestive system and internal organ developed in 22 days. Eye and limb bud and scales developed in 46 days and fully developed at 60 days. The babies hatched at 72-77 days, with 56.67-76.47 percent hatching rates. and have size 28.26+-1.05 cm long, weighing 66.74+-2.61 g.
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