• Journal of Fisheries and Marine Sciences Education
• /
• v.29 no.3
• /
• pp.702-710
• /
• 2017

Recently, in many reptiles (14 genera of turtles in five families), common characteristics of incubation temperatures are known to determine the sexes of hatchlings in many species of turtles, including the map turtles, painted turtles and snapping turtles, emys turtle, etc. According to many researcher's reports, in general, incubation at $25^{\circ}C$ (cooler temperatures) produces all or mostly males, however, incubation at $31^{\circ}C$ (higher temperatures) or higher produces all or mostly females. Exceptionally, even cooler temperature ($20^{\circ}C$) produce females, they produced all or mostly females. Accordingly, it is well-known that incubation temperature is the sex determining agent in these turtles. However, this paper presents study of the sex ratio and nest ecology in natural spawning nest: Observations on hatching sex ratios of eggs collected from natural nests of T. sinensis are similar to a previous report of the same genus Trionyx in the soft-shelled turtles. However, this genus (or species) showed some different phenomena to other kinds of turtles such as various kinds turtles mentioned above. After collection of naturally spawned eggs (17 eggs of T. sisnensis) on the natural nests, a laboratory experiment by the constant incubation temperatures was conducted with natural fluctuating soil temperatures in the natural nest with the soft-shelled turtle, T. sinensis. And also laboratory experiments were conducted using constant incubation temperatures of $25^{\circ}C$ (cooler temp.) and $30^{\circ}C$ (higher temp.) with the turtle, T. sinensis. Exceptionally, it was confirmed that the first and second incubation temperatures can't control sex-determination in the freshwater soft-shelled turtle, T. sinensis. The sex ratio approximated 1:1 (${\chi}^2=0.06$, P>0.05 (the Ist experiment). And the sex ratio approximated 1:1 independently of incubation temperature (${\chi}^2=0.33$, P>0.05 (the 2nd experiment). Consequently, temperature has no effect on sex determination in the genus Trionyx in a soft-shelled turtle.

• Development and Reproduction
• /
• v.21 no.1
• /
• pp.101-110
• /
• 2017

On June 14, 2008 (the first experiment) and July 24, 2008 (the second experiment), the shores of the Boseong River and the sandy beaches, Seokgok-myun, Moksadong-myun, Gokseong-gun in Jeollanam Province were investigated and a total of 29 soft-shelled turtle (Tryonyx sinensis) eggs in the natural spawning nest eggs were collected (13 eggs were collected in the first experiment and 16 eggs in the second experiment). The temperatures in the natural spawning nests were $25.9-36.9{\pm}0.5^{\circ}C$, the depth of the eggs was $5.2-7.5{\pm}0.5cm$ as the distance of the average $6.4{\pm}0.5cm$. 29 eggs were scattered at least 0.2 cm interval. Artificial incubation of 29 eggs was conducted in artificial nest boxes in thermo-plastic composition of the incubator, and then incubated at $26.5-35.5{\pm}0.5^{\circ}C$, and an average constant temperature was $31.2-32.1{\pm}1.0^{\circ}C$. The incubation days ranged from 53 to 55. In case of most turtles, incubation at $31^{\circ}C$ (higher temperatures) generally produces all or mostly females, while incubation at $25^{\circ}C$(cooler temperatures) produces all or mostly males. Exceptionally, in case of genus Trionyx, the sex ratio of female : male of T. sinensis of a freshwater soft-shelled turtle was approximately 1:1, which differs from other genera of turtles and makes T. sinensis Strauch only turtles presently known to lack temperature-dependent sex determination.

• Development and Reproduction
• /
• v.15 no.2
• /
• pp.133-141
• /
• 2011

The marine ornamental industry has become a multi-billion dollar industry these days. As developing, however, this industry has been criticized for the indiscriminate captures and the destruction of the surrounding environment. To circumvent these problems, it is suggested to breed the organisms artificially. While clownfishes Amphiprion sp. and Premnas sp. are the most famous ornamental organisms in the trade, few studies are yet available on the culture and commercial production of these fishes. These studies were performed to investigate the spawning periodicity, behavior and the habits during egg incubation, and to provide the information on the mass hatching system. The spawning periodicity and frequency were different in 4 pairs under the constant condition, temperature, salinity and photoperiod. On the contrary, the male's behaviors for egg incubation are almost same in the all. The egg-fanning activity of the male increased as the developing eggs reaching to the hatching day. Based on the above results, we designed a new artificial hatching system, the rotating type (RT), and compared it with the aeration type (AT) and spray type (ST) that were previously described. RT showed higher hatching rate of 87.3% than AT (74.4%) and ST (60.5%). Also, there were no significant differences in the hatching rate regardless of the number (2, 3, 5) of hatching plates. We suggest RT may accommodate various number of hatching plates and constitute a better hatching system for clownfishes.