羊草（Leymus chinensis）对刈割响应的特征研究

羊草是高品质的牧草，羊草草地是优良的割草场，刈割是人类对草地的主要利用手段之一，其对羊草草地造成的影响一直受到学者和生产管理者的关注并开展了大量研究。但以往刈割的相关研究主要集中在整个草地的水平上，羊草个体对刈割的响应迄今还没有深入研究。随着畜牧业的发展对草场质量要求的不断提高，发掘耐刈割的羊草种质势在必行，而羊草在不同时期对刈割的响应状况及不同生态型羊草对刈割的响应则是其中必不可少的研究环节。 本文以羊草为实验材料，对其在不同发育时期进行了刈割研究，主要以高度作为动态研究的手段，包括四个部分： 实验1，羊草在苗期对刈割的响应，结果表明，苗期进行的刈割，对羊草第1片叶生长速率没有影响。 实验2，两种生态型羊草在三四叶期及七八叶期两次刈割的响应，表明三四叶期进行的刈割，羊草能达到85.1%的恢复，灰绿型比黄绿型多恢复8.5%。七八叶期进行的刈割，刈除茎尖使羊草停滞生长。三四叶期的刈割能导致灰绿型增加1个分株，黄绿型则减少1个分株。 实验3，四年生羊草草地对不同程度刈割的响应，表明羊草草地在重度刈割后所受影响更严重，但每株羊草分蘖数目会增加1。 实验4，赖草属十一个物种生长期刈割响应，表明羊草对刈割的恢复性明显高于所研究的赖草属其他物种，达到超补偿水平。 在对羊草草原合理利用时，适度刈割是关键的，刈割的频次及程度关系重大。羊草生态型的选择也有举足轻重的作用，选用适应性强的灰绿型羊草对于提高羊草草地具有一定的积极作用。

Otolith characteristics and age determination of an endemic Ptychobarbus dipogon (Regan, 1905) (Cyprinidae: Schizothoracinae) in the Yarlung Tsangpo River, Tibet

We describe the microincrements, checks and annuli in the lapilli of the schizothoracine Ptychobarbus dipogon, an endemic species of the Tibetan plateau. We collected samples in the Yarlung Tsangpo River and its tributaries on a monthly basis (from April 2004 to August 2006). We describe the shape features of the three pairs of otoliths and document the full trajectory of lapillus development. We found that five to seven checks were clearly visible in the opaque zone of the first annulus. The pattern of 21-23 daily growth increments within each check might be explained as a lunar-induced deposition. We counted between 137 and 154 increments within the first annulus. Annuli appeared as a sequence of gradually declining increment widths, whereas false rings were characterized by abrupt checks. Our oldest estimates were 23(+)years for males and 44(+) for females. The time of annulus completion was clearly between March and April each year using monthly marginal increments analysis. We consider the factors responsible for daily increment formation as an endogenous circadian rhythm. Environmental information, such as strong sunlight and cold water temperatures in the Tibetan Plateau, could reinforce the endogenous daily cycle. Our results provided important data addressing the ecology and population dynamics of P. dipogon.

Transport-determined early growth and development of jack mackerel Trachurus japonicus juveniles immigrating into Sagami Bay, Japan

Oceanographic conditions and transport processes are often critical factors that affect the early growth, survival and recruitment of marine fishes. Sagittal otoliths were analysed to determine age and early growth for 381 jack mackerel (Trachurus japonicus) juveniles from Sagami Bay on the Pacific coast of Japan. Two separate hatching periods ( December and February-March) were identified. They originated from the spawning grounds in the East China Sea. Early growth and developmental rates of December-hatching fish were lower than those for February-March-hatching fish. It is likely that these differences were determined in the Kuroshio Current during transport from the spawning grounds to Sagami Bay, and the lower December water temperatures in the bay. Origin and hatch dates of juveniles in Sagami Bay were in contrast to previous research on Fukawa Bay, where April-or-later-hatching fish from spawning grounds in the coastal waters of southern Japan constituted about half of the juvenile population. Management of these two jack mackerel stocks needs to consider these differences in hatch date composition and spawning origins, as these differences could affect early growth and subsequent mortality.

Age and growth of an endemic cyprinid fish, Spinibarbus yunnanensis, from Lake Fuxian, China

Age and growth of Spinibarbus yunnanensis Tsu in Lake Fuxian were investigated by examination of annuli from scales, dorsal fin spines, and otoliths. Sectioned otoliths exhibited the clearest and the most regular annuli. The formation of false annuli, which regularly arose on scales and dorsal fin spines during the juvenile stage, may be caused by a change in diet during development. The parameters for the von Bertalanffy growth curve were: K = 0.105, L-infinity = 950 mm, t(0) = -0.22 year for both sexes. W-infinity, calculated from the relationship W-infinity = aL(infinity)(b), was 10,352 g.

Screening of genes related to ovary development in Chinese shrimp Fenneropenaeus chinensis by suppression subtractive hybridization

The ovary of triploid shrimp Fenneropenaeus chinensis was apparently impaired compared to that of the diploid shrimp at the same age. Therefore triploid shrimp ovary is possible to be taken as a model to understand the mechanism of ovary development of shrimp compared to that of the ovary of diploid shrimp at the same age. In the present study, a suppression subtractive hybridization (SSH) technique was applied to identify differentially expressed genes in the ovary between diploid and triploid shrimp. For the forward library (RNA from the ovary of triploid shrimp as the tester), 54 genes were identified. For the reverse library (RNA from the ovary of diploid shrimp as the tester), 16 genes were identified. The identified genes encoded proteins with multiple functions, including extracellular matrix components, cytoskeleton, cell growth and death, metabolism, genetic information processing, signal transduction/transport or immunity related proteins. Eleven differentially expressed genes were selected to be confirmed in the ovaries of triploid and diploid shrimp by semi-quantitative RT-PCR. Genes encoding spermatogonial stem-cell renewal factor, cytochrome c oxidase subunits I and II, clottable protein, antimicrobial peptide and transposase showed up-regulated expressions in the ovary of triploid shrimp. Genes encoding tubulin, cellular apoptosis susceptibility protein, farnesoic acid O-methyltransferase, thrombospondin and heat shock protein 90 genes showed higher expressions in the ovary of diploid shrimp. The differential expressions of the above genes are suggested to be related to the ovary development of shrimp. It will provide a new clue to uncover the molecular mechanisms underlying the ovarian development in penaeid shrimp. (C) 2010 Elsevier Inc. All rights reserved.

Effect of graded levels of rapeseed oil in isonitrogenous diets on the development of the gastrointestinal tract, and utilisation of protein, fat and energy in broiler chickens

The effect of feeding 0, 4, 8 and 16% rapeseed oil from 12-42 days of age was studied in broiler chickens on performance, digestibility of nutrients, and development of gastrointestinal tract, protein and energy metabolism. Thirty six female chickens (Ross 208) with initial body weight average 246 g were allocated to the four groups and kept pair-wise in metabolism cages. The chickens were fed similar amounts of metabolisable energy (ME) per day and similar amounts of essential amino acids relative to ME by adjusting with crystalline amino acids. The chickens were subjected to four balance periods each of five days with two 24 h measurements of gas exchange in two open-air-circuit respiration chambers inserted on the second and third day of each period. The addition of rapeseed oil increased the amount of gutfill indicating a reduced rate of passage and causing a hypertrophy of the gastrointestinal tract. There was a positive effect on feed utilisation as well as on digestibility especially of dietary fat together with higher utilisation of protein with addition of rapeseed oil. The partial fat digestibility of rapeseed oil estimated by regression was 91.1% and the partial metabolisability (ME/GE) of the rapeseed oil was estimated to 85% yielding an apparent metabolisable energy value of 34.30 MJ/kg.