Reproduction in three species of rainbowfish (Melanotaeniidae) from rainforest streams in northern Queensland, Australia

Abstract – The reproductive biology of three species of rainbowfish (Melanotaeniidae) in northeastern Australian rainforest streams was investigated. Two species, Melanotaenia eachamensis and Cairnsichthys rhombosomoides are endemic to the area, whereas the third, M. splendida splendida, is more widespread. The species were all highly fecund, producing many hundreds of eggs between 1.10 and 1.24 mm in diameter. Melanotaenia eachamensis was the most fecund, produced the largest eggs of the three species, and consequently exhibited the greatest maternal investment (as measured by gonadosomatic index). The majority of reproductive effort occurred during the dry season, although reproductively active fish were present year-round for each of the species, but particularly so for M. s. splendida and C. rhombosomoides. No evidence for a role by temperature or photoperiod as environmental cues for reproduction was found, and it was suggested that gonad development was strongly tied to somatic growth. The concentration of reproduction to the dry season ensures that larvae are produced during a period of relatively stable and benign physical conditions. Comparison of temporal changes in gonadosomatic index values suggest that the spawning season of M. eachamensis , which occurs in high-elevation streams, is more restricted and commences about 1 month earlier than either other species. A similar phenology was observed for the M. s. splendida population found at high elevation and highlights the potential for spatial differences in stream productivity to influence life history. ^Note     

Neutrophil Phagocytosis Following Inoculation of Salmonella choleraesuis into Swine

Neutrophils are an important mediator of host defence, especially in early stages of infection. A major function of neutrophils is the uptake and killing of invading microbes. Little is known about the effect of neutrophil activity on the pathogenesis and development of the carrier state in swine following infection with Salmonella choleraesuis. A human whole-blood microassay using flow cytometry was modified to measure the effect of S. choleraesuis infection in vivo on the rate of ingestion, or rate of uptake, of homologous bacteria by porcine neutrophils. Pigs were inoculated intranasally with 5–8×10⁸ CFU S. choleraesuis and blood was collected in heparinized tubes at –5, 0, 1, 2, 3 and 4 days post inoculation (PI). Heat-killed S. choleraesuis were labelled with fluorescein isothiocyanate and incubated for various times with diluted whole blood. Red blood cells were lysed, external non-phagocytized bacteria were quenched with a commercially available lysing solution, and fluorescence from internalized bacteria labelled with fluorescein isothiocyanate was detected by flow cytometry. The rate of uptake by neutrophils did not increase until 2 days PI and then remained elevated to 4 days PI. The minimal uptake of S. choleraesuis early after exposure to these organisms may provide an opportunity for the pathogen to colonize and/or replicate to levels that facilitate establishment of a carrier state or clinical infection in swine.     

Fixed location hydroacoustic monitoring of fish populations in the tidal River Hull, north-east England, in relation to water quality

Abstract  Fixed location hydroacoustic fish monitoring was carried out at a series of sites in the tidal River Hull, north-east England, in July 1996 during periods of moderate freshwater flows and spring tides. This was followed by a corresponding series during a period of lower freshwater flows and spring tides in autumn 1996. The surveys indicated substantial numbers of fish living upstream and downstream of a depleted oxygen zone which exists in the tidal Hull. Conditions in this zone of poor water quality deteriorated further during low flow periods due to reduced dilution of effluents. Fish populations moved with the tide apparently in response to gradients of dissolved oxygen and salinity. Under conditions of low freshwater flow and high tides, gradients of salinity and oxygen were steeper and fish responses appeared more marked: at higher salinities, the response to increasing salinity overrode the response to decreasing oxygen availability.     

输油管道水力流态区域判别法的计算

以雷诺数形式给出的判别式,对水力计算的二、三类问题(Q或d未知)不能预先判明流体流动所属流态区域,计算时需试算或迭代。以推荐的石油工业部门常用的湍流区域界限为基础,对判别式做了推导或变形,并用最小二乘法拟合有关常数,由此得出的判别式对于管道水力计算的三类基本问题均能预先判明流态区域,不需试算。     

管壁特性与摩阻关系

对憎液表面的水力摩阻特性进行了试验研究,实验中憎液表面材料采用聚四氟乙烯,试验工质采用水和7号机械油。试验结果表明,内衬聚四氟乙烯管较普通钢管具有一定的减阻效果,对工质水而言,其减阻效果大约为12％,对7号机械油而言,其减阻效果为6％左右,减阻效果取决于壁面材料对介质的憎液程度,即聚四氟乙烯对水的憎液性能比对7号机械油的好。通过对憎液表面流动机理的理论分析表明,表面经憎液处理后,由于降低了表面能级,使得固壁对液体分子的吸引力小于液体分子间的吸引力,壁面部分流体产生滑移现象,从而达到了一定的减阻效果。