Unusual distribution of floating seaweeds in the East China Sea in the early spring of 2012

Floating seaweeds play important ecological roles in offshore waters. Recently, large amounts of rafting seaweed have been observed in the East China Sea. In early spring, juveniles of commercially important fish such as yellowtail accompany these seaweed rafts. Because the spatial distributions of seaweed rafts in the spring are poorly understood, research cruises were undertaken to investigate them in 2010, 2011, and 2012. Floating seaweed samples collected from the East China Sea during the three surveys contained only Sargassum horneri. In 2010 and 2011, seaweed rafts were distributed only in the continental shelf and the Kuroshio Front because they had become trapped in the convergence zone of the Kuroshio Front. However, in 2012, seaweed was also distributed in the Kuroshio Current and its outer waters, and massive strandings of seaweed rafts were observed on the northern coast of Taiwan and on Tarama Island in the Ryukyu Archipelago. Environmental data (wind, currents, and sea surface height) were compared among the surveys of 2010, 2011, and 2012. Two factors are speculated to have caused the unusual distribution in 2012. First, a continuous strong north wind produced an Ekman drift current that transported seaweed southwestward to the continental shelf and eventually stranded seaweed rafts on the coast of Taiwan. Second, an anticyclonic eddy covering northeast Taiwan and the Kuroshio Current west of Taiwan generated a geostrophic current that crossed the Kuroshio Current and transported the rafts to the Kuroshio Current and its outer waters. Such unusual seaweed distributions may influence the distribution of fauna accompanying the rafts.     

Levels and distribution patterns of mitochondrial cox3 gene variation in brown seaweed,Sargassum polycystum C. Agardh (Fucales,Phaeophyceae) from Southeast Asia

Sargassum polycystum C. Agardh is one of the most abundant marine brown algae and is distributed widely in warm and temperate waters, particularly in the Indo-west Pacific region and Australia. Although its commercial potential and ecological and evolutionary importance are recognized, many pivotal aspects of its biology remain unexplored. Current knowledge of the historical biogeographical affinities and patterns is limited, but some data are available about its genetics, the genetic variation among populations, and spatial patterns. This study aimed to analyze the genetic population structure and distribution patterns of S. polycystum populations in 13 different locations from Indonesia to Japan using the mitochondrial gene cox3. The seven haplotypes of cox3 identified in this study indicated a low level of genetic diversity. Homogeneity of this haplotype was observed particularly in the Gulf of Thailand, Cambodia, and Japan, whereas higher haplotype diversity was found in Phuket (Thailand), Bali (Indonesia), and Singapore. Those data suggest that S. polycystum is likely to have expanded from the south of Indonesia and the west of the Malay Peninsula towards the northeast of the region. Geological studies showed that Sundaland, now corresponding to the Gulf of Thailand, was submerged due to sea level rises after the last glacial period. Therefore, the decrease in the genetic diversity of S. polycystum populations is interpreted here as a population expansion after the rise in sea levels.     

A novel method of caenophidian snake sex identification using molecular markers based on two gametologous genes

Sex identification provides important information for ecological and evolutionary studies, as well as benefiting snake conservation management. Traditional methods such as cloacal probing or cloacal popping are counterproductive for sex identification concerning very small species, resulting in difficulties in the management of their breeding programs. In this study, the nucleotide sequences of gametologous genes (CTNNB1 and WAC genes) were used for the development of molecular sexing markers in caenophidian snakes. Two candidate markers were developed with the two primer sets, and successfully amplified by a single band on the agarose gel in male (ZZ) and two bands, differing in fragment sizes, in female (ZW) of 16 caenophidian snakes for CTNNB1 and 12 caenophidian snakes for WAC. Another candidate marker was developed with the primer set to amplify the specific sequence for CTNNB1W homolog, and the PCR products were successfully obtained in a female‐specific 250‐bp DNA bands. The three candidate PCR sexing markers provide a simple sex identification method based on the amplification of gametologous genes, and they can be used to facilitate effective caenophidian snake conservation and management programs.     

Root cortical aerenchyma,characteristics and nutrient use efficiency of different maize hybrids during drought and rehydration process

The importance of cortical aerenchyma in flood and drought resistance is well established. However, effects of the combination of the two factors remain unclear. We tested the hypothesis that under conditions of substantial water alteration, enhanced root cortical aerenchymas (RCAs) could not only exert a positive effect on root functions under drought periods but also influence nitrogen capture, soil exploration and compensation growth after rehydration. Three maize varieties, Yurui2 (YR2), Yunrui6 (YR6) and Yunrui167 (YR167), were grown under rainfed field conditions, and a subset was grown initially under well-watered and extreme-drought conditions, followed by the same simulated rainfed field conditions, in order to compare the effects on the RCAs during the growing season. Root morphology and function parameters were measured, and variation in the RCAs was induced by water stress. Under extreme drought, we found substantial variation in the RCAs (from 0% to 37%) and drought tolerance performance. During the rehydration stage, different RCA components exerted different effects on maize, recovery parameters and plant N use efficiency. YR6 showed resilient growth, whereas recovery was inhibited in YR167 and YR2, respectively, which possessed the lowest and highest RCA area percentages. The results support the hypothesis that RCA area percentage under drought periods are important for maize recovery after post-drought rehydration.