Amplified fragment length polymorphism analysis to identify the genetic structure of the Gymnocypris przewalskii (Kessler, 1876) population from the Qinghai Basin, China

Amplified fragment length polymorphism (AFLP) was used to analyse the genetic structure of 45 individuals of Gymnocypris przewalskii (Kessler, 1876), an endangered and state-protected rare fish species, from three areas [the Heima (HM), Buha (BH) and Shaliu rivers (SL), all draining into Qinghai Lake]. A total of 563 polymorphic loci were detected. The HM, BH and SL populations have 435, 433 and 391 loci, respectively (Zhu and Wu, 1975), which account for 77.26%, 76.91% and 69.45% of the total number of polymorphic loci of each population, respectively. The Nei indices of genetic diversities (H) of the three populations were calculated to be 0.2869 (HM), 0.2884 (BH) and 0.2663 (SL), respectively. Their Shannon informative indices are 0.4244, 0.4251 and 0.3915, respectively. Research results show that the mean genetic distance between HM and BH is the smallest (0.0511), between BH and SL is the second shortest (0.0608), and between HM and SL is the largest (0.0713), with the mean genetic distance among the three populations being over 0.05. Data mentioned above indicate that the three populations have a certain genetic differentiation. The total genetic diversity (H-t = 0.3045) and the mean value of genetic diversity within the population (H-s = 0.2786) indicate that the variations have mainly come from within the population.

Sinibrama longianalis, a new cyprinid species (Pisces : Teleostei) from the upper Yangtze River basin in Guizhou, China

Sinibrama longianalis, a new cyprinid species from the Wu Jiang (upper Yangtze River basin) in Guizhou, China is distinguished from other congeners in having the following combination of characters: last simple dorsal-fin ray well-ossified; a snout shorter than eye diameter; eye diameter 27.1-31.6% HL; lateral line scales 56-64 (mean 59.5); circumpeduncular scales 18-21; anal fin with 24-28 (mean 25.2) branched rays, originating opposite to or slightly in advance of posterior end of dorsal-fin base, basal length 27.0-31.1% SL; pectoral fin reaching to or slightly beyond pelvic-fin insertion.

Garra tengchongensis, a new cyprinid species from the Upper Irrawaddy River basin in Yunnan, China (Pisces : Teleostei)

Garra tengchongensis, a new cyprinid species from the upper Irrawaddy River basin in Tengchong county, Yunnan province, China, is differentiated from all other Chinese and Southeast Asian Garra species except G. kempi by having a combination of the following characters: two pairs of barbels, no proboscis on snout, 12 circumpeduncular scales and 37-42 lateral line scales. Garra tengchongensis is distinguished from G. kempi in having a cylindrical anterior body, a deeper body, a smaller mental adhesive disc, a scaled breast and belly, and a blunt snout.

Methane hydrate growth velocity in seepage system of Qiongdongnan Basin, South China Sea

The occurrences of diapirs, gas-filled zones and gas plumes in seawater in Qiongdongnan Basin of South China Sea indicate that there may exist seepage system gas-hydrate reservoirs. Assuming there has a methane venting zone of 1500 m in diameter, and the methane flux is 1000 kmol/a, and the temperature of methane hydrate-bearing sediments ranges from 3 degrees C to 20 degrees C, then according to the hydrate film growth theory, by numerical simulation, this paper computes the temperatures and velocities in 0 mbsf, 100 mbsf, 200 mbsf, 425 mbsf over discrete length, and gives the change charts. The results show that the cementation velocity in sediments matrix of methane hydrate is about 0.2 nm/s, and the seepage system will evolve into diffusion system over probably 35000 years. Meanwhile, the methane hydrate growth velocity in leakage system is 20 similar to 40 times faster than in diffusion system.