温度和盐度对蒙古裸腹氵蚤种群内禀增长能力的影响

报道了蒙古裸腹氵蚤 (Moinamongolica)在 2 0℃～ 33℃温度和 5～ 40 ppt盐度条件下的种群内禀增长率(rm) .结果表明 ,2 0℃～ 30℃范围内蒙古裸腹氵蚤rm 随温度升高而升高 ,超过 30℃后继续升温 ,rm 显著降低 ;在低盐度下蒙古裸腹氵蚤的种群增长能力相对较强 ,盐度为 10 ppt时rm 最高 ,2 0～ 40 ppt范围内 氵蚤的rm 差别不明显 .本实验表明 ,2 5℃～ 30℃和 10 ppt分别是蒙古裸腹 氵蚤种群增长较快的温度和盐度条件 ,在海水中长期培养对蒙古裸腹氵蚤的种群增长能力不会产生明显的不良影响     

多刺裸腹溞在不同盐度下的种群增长参数及其驯化

在25±1℃及小球藻、酵母、牛粪+稻草+沃土3种食物条件下,研究了多刺裸腹溞在海水盐度为2‰、3‰、4‰、6‰和淡水5个浓度下的种群增长参数.实验表明无论投喂何种食物,在淡水至4‰盐度范围内,多刺裸腹溞种群的内禀增长率(rm无显著差异为0.725-1.070(d-1);净增殖率(Rn)以小球藻组平均数最高为55.13(ind.);世代时间(T)以酵母组最长,平均为5.38(d).6‰为多刺裸腹溞的生殖盐度上限.经过短期的海水驯化,其生殖的盐度上限可达9-10‰.     

可口革囊星虫胚胎与幼体的发育

解剖经降温8-10℃刺激30-40h后的可口革囊星虫(Phascolosomaesculenta)亲体取得精、卵,用人工授精法获得的受精卵进行胚胎和幼体发育的研究。结果表明:可口革囊星虫的卵为圆形或椭圆形,卵的大小为120μm×142μm-125μm×148μm。精子由头部、中段和尾部组成,全长约为32-40μm。在海水盐度23.8ppt、pH8.1、温度15℃的条件下,精、卵不能受精;在海水盐度23.8ppt、pH8.1、温度20℃的条件下,精卵能受精,但胚胎发育到原肠胚期停止;在海水盐度23.8ppt、pH8.1条件下,25℃、30℃和35℃的不同水温,精卵均能受精,受精卵发育到初期海球幼虫分别需要72h0min、47h08min和42h53min。在海水盐度23.8-25.5ppt,pH8.1-8.2,温度28-30℃条件下,从初期海球幼虫发育到稚虫需要15-20d。     

温度、盐度对海月水母碟状体生长及存活的影响

海月水母为我国近海主要大型灾害水母种类之一,当自然环境适宜其生长与繁殖时,易出现暴发性的增殖现象,严重破坏了我国近岸海洋生态系统的稳点与平衡。采用实验生态学方法,研究了温度(2.5、5、7.5、10、15、20、25、27.5、30℃)和盐度(15、20、25、30、35、40)对海月水母碟状体存活与生长的影响,实验共进行30d。结果显示,在实验设置的温盐范围内,温度、盐度均显著影响碟状体的存活与生长。在盐度15-35条件下,海月水母碟状体可以在温度2.5-25℃存活,在15-25℃范围内可正常生长;在温度20-25℃和盐度20-30条件下适宜海月水母碟状体生长,其中温度20℃和盐度25条件下海月水母碟状体特定生长率达到最大。与盐度相比,温度对碟状体的影响较大,在盐度15-35条件下,随着温度的升高,碟状体的伞径逐渐增大,其碟状体形态向水母体形态的转变速度加快。在达到临界点25℃时,若继续升高温度,碟状体的生存率与生长率显著下降。温度与盐度对海月水母碟状体的生存与生长具有明显的交互效应,碟状体在实验过程中表现出在较低温度条件下提高了对较高盐度的适应性。研究表明,温度、盐度的变化显著影响碟状体的生长与存活,直接导致碟状体种群数量变动,进而影响成熟水母体种群数量。结论为进一步探索大型水母暴发的生态环境机理提供重要科学依据。     

共培养大型海藻对蒙古裸腹溞培养体系的生态效应

为了解大型海藻与盐水枝角类共培养的生态作用,通过大型海藻与蒙古裸腹溞共培养的方法,研究了孔石莼和肠浒苔对共培养水体水质的静态净化效果以及对该溞生殖与种群增长的影响。结果表明:孔石莼和肠浒苔对共培养水体氨氮(NH3-N)、pH和溶解氧(DO)的影响显著(P0.05)且变化规律基本一致,其中NH3-N在第12 d降到最低(0.016mg·L~(-1)),随后维持在相对稳定范围内; pH和DO随孔石莼和肠浒苔生物量的增加而升高,pH变化范围8.2～9.0,DO变化范围4.2～6.4 mg·L~(-1);共培养条件下两种大型海藻对蒙古裸腹溞生殖和种群增长的影响表现出明显差异,在孔石莼共培养体系中,蒙古裸腹溞的平均生殖量、内禀增长率rm、周限增长率λ和世代周期T随孔石莼生物量的增加呈波动升高,当生物量为2.5 g·L~(-1)时均达峰值,之后逐渐下降,平均寿命随孔石莼生物量的增加而减少;孔石莼共培养体系显著优于对照组单一蒙古裸腹溞培养效果(P0.05),而肠浒苔共培养体系与对照组相差不显著(P0.05)。研究结果证明了孔石莼对共培养体系水质和养殖动物的有利作用,即共培养一定生物量(2.5～3.5 g·L~(-1))的孔石莼不但有利于培养水体中NH3-N、DO等水质净化,还可以促进蒙古裸腹溞的生长与繁殖,为蒙古裸腹溞规模化培养工艺优化与新模式构建提供了科学依据。     

大亚湾裸甲藻种群的季节变化与环境条件的关系

研究了大亚湾1997年7月至1998年6月裸甲藻种群季节变化及其与环境因子的关系。裸甲藻在大亚湾主要出现在4－5月份,并在4月至5月份出现了4个密度高峰,最高密度可达每毫升996个细胞,6月至9月份偶有出现,10月至2月份则未出现。裸甲藻高密度出现的温度、盐度范围分别为25－30℃和24‰-32‰。裸甲藻在大亚湾的出现及4、5月份的密度高峰与水温的季节变化密切相关,3月份水温存在一个急升期,水温由3月初的15.5℃以下上升至3月底的23.5℃左右,为裸甲藻种群密度的急剧增长提供了合适的温度条件。大亚湾盐度的季节波动较小,与裸甲藻种群的种群的季节变化无关。大亚湾氮、磷、硅等营养物质含量丰富,不存在营养元素缺乏,但高密度的裸甲藻种群仅在氮、磷含量及氮磷比分别为50－100μg/L,5-20μg/L和5－30范围内出现,氮、磷、硅3种营养盐的含量及它们之间的比值特别是氮磷比是影响裸甲藻高密度出现的重要内容。     

温度对西花蓟马生长发育、 繁殖和种群增长的影响

西花蓟马Frankliniella occidentalis (Pergande)是一种入侵我国的重要害虫, 温度是决定蓟马能否建立稳定种群的最基本因素。为明确温度对西花蓟马种群增长的影响, 本研究在室内观察了西花蓟马在15℃, 20℃, 25℃, 30℃和35℃温度条件下的生长发育、 存活与繁殖能力, 并计算各温度条件下的种群增长参数。结果表明： 在35℃条件下, 西花蓟马不能完成发育, 其他温度条件下西花蓟马从卵孵化至蛹羽化成成虫, 以20℃条件下的存活率最高, 为62.8%。西花蓟马发育速率随温度升高明显加快, 在15℃下, 完成发育需要近30 d; 而在30℃下, 西花蓟马完成发育仅需10 d 左右。西花蓟马成虫寿命随温度的升高而明显缩短, 在15℃下, 平均寿命为36 d, 最长寿命达60 d; 在30℃下, 西花蓟马的平均寿命为10 d。西花蓟马在 15℃, 20℃和25℃条件下的平均繁殖力差异不显著, 分别为37.70, 32.56, 37.80头1龄若虫/雌, 但显著高于30℃条件下的平均繁殖力（9.36头1龄若虫/雌）。西花蓟马的种群增长参数净生殖率(R0)、 内禀增长率(rm), 在25℃时达最高值, 分别为20.10和0.178 d-1, 而在15℃下分别仅为18.67和0.096 d-1。据此得出, 20~25℃是最适宜西花蓟马生长发育和繁殖温度范围, 温度过高或过低都不利于西花蓟马种群增长。西花蓟马的发育起点温度为7.4℃, 充分完成发育所需的有效积温为208.0日·度。不考虑其他阻碍生长发育因素的情况下, 华南、 华中、 华北和东北地区的年发生代数分别为24~26, 16~18, 13~14和1~4代, 西南地区昆明与丽江分别为13~15和8~10代。     

近亲裸腹溞对海水盐度的适应性

为了解淡水枝角类对海水盐度的适应性,在实验室内采用种群实验生态学方法研究25 ℃±0.5 ℃恒温条件下不同盐度（0、1、2、3、4、5）对近亲裸腹溞(Moina affinis)生存、生长和生殖的影响.结果表明,在各盐度梯度范围内,近亲裸腹溞的平均寿命随盐度升高而缩短,盐度4和5组内禀增长率与其它各组差异显著;盐度4和5组平均每窝产幼量与对照及其他组差异显著.一生产幼量除盐度1组和对照组较高外,其他各组均显著下降.对照组体长增长幅度与日增长率均低于各处理组.日增长率随着盐度的升高而增大.个体平均每胎产幼量以盐度1、2组最高.盐度5为近亲裸腹溞的生存和生殖盐限,但经过短期的海水驯化,其生殖耐盐上限有所提升,可达6.5.     

温度和食用藻密度对发头裸腹潘种群动态和两性生殖的影响

研究了不同温度和食用藻密度对发头裸腹潘种群动态和两性生殖的影响.结果表明:温度、食用藻密度对发头裸腹溞的种群密度、雄体密度和卵鞍数均有显著影响.高食用藻密度组的发头裸腹潘种群密度明显高于中、低食用藻密度组,其最大种群密度出现在20℃下的高食用藻密度组.在相同的温度下,发头裸腹溞的首次产幼溞数随食用藻密度的降低而减少,平均每个母潘首次产出的最大幼潘数出现在25℃下的高食用藻密度组.高食用藻密度组发头裸腹潘产生的雄体密度明显高于中、低食用藻密度组.发头裸腹溞的雄体密度与其种群密度之间存在极显著的相关性.发头裸腹溞所产的卵鞍数随食用藻密度的下降而下降,且25℃下发头裸腹溞所产的卵鞍数明显高于其他温度组.与温度相比,食用藻密度对发头裸腹潘的种群动态和两性生殖的影响更大.     

温度和食用藻密度对发头裸腹溞种群动态和两性生殖的影响

研究了不同温度和食用藻密度对发头裸腹溞种群动态和两性生殖的影响.结果表明： 温度、食用藻密度对发头裸腹溞的种群密度、雄体密度和卵鞍数均有显著影响.高食用藻密度组的发头裸腹溞种群密度明显高于中、低食用藻密度组,其最大种群密度出现在20 ℃下的高食用藻密度组.在相同的温度下,发头裸腹溞的首次产幼溞数随食用藻密度的降低而减少,平均每个母溞首次产出的最大幼溞数出现在25 ℃下的高食用藻密度组.高食用藻密度组发头裸腹溞产生的雄体密度明显高于中、低食用藻密度组.发头裸腹溞的雄体密度与其种群密度之间存在极显著的相关性.发头裸腹溞所产的卵鞍数随食用藻密度的下降而下降,且25 ℃下发头裸腹溞所产的卵鞍数明显高于其他温度组.与温度相比,食用藻密度对发头裸腹溞的种群动态和两性生殖的影响更大.     

Life history of hawthorn spider mite Amphitetranychus viennensis (Acarina: Tetranychidae) on various apple cultivars and at different temperatures

Development duration and reproduction rate of hawthorn spider mite Amphitetranychus viennensis (Zacher) were carried out on five different apple cultivars (Amasya (local cultivar), Golden Delicious, Granny Smith, Starking Delicious and Starkrimson Delicious) at 25 degrees C, 65 +/- 10% RH and 16:8 L:D. In addition, the same parameters were determined on Golden Delicious leaves at three constant temperatures (20, 30 and 35 degrees C, 65 +/- 10% RH and 16:8 L:D) in the laboratory. A. viennensis showed a better performance on Golden Delicious than on the other apple cultivars. This was mainly due to a short development time (10.7 days), high daily egg production (5.2 eggs/female/day) and early reproduction peak. The highest intrinsic rate of natural increase (rm) was determined on the variety Golden Delicious (rm = 0.247/day), while the lowest one was observed on the variety Starking Delicious (rm = 0.215/day). The developmental periods of A. viennensis varied from 7.4 to 18.8 days at 35 and 20 degrees C for females, while it varied from 7.9 to 17.2 days at 30 and 20 degrees C for males. The development threshold of the eggs and pre-adult stages were 9.72 and 9.07 degrees C, total effective temperature was 72.99 and 185.18 degree-days, respectively. The mean generation time (To) of the population ranged from 16.13 days at 30 degrees C to 29.15 days at 20 degrees C. The net reproductive rate (R0) increased from 54.33 female/female at 20 degrees C to 78.34 female/female at 25 degrees C, and decreased to 75.71 female/female at 30 degrees C. The highest intrinsic rate of increase (rm) was reached at 30 C (rm = 0.268/day), the lowest one at 20 degrees C (rm = 0.136/day).     

Influence of temperature on the development, reproduction and longevity of Ceratothripoides claratris (Thysanoptera: Thripidae) on tomatoes

Ceratothripoides claratris (Shumsher) is a serious pest attacking tomatoes in Thailand. Temperature-dependent development of C. claratris was studied at seven constant temperatures, i.e. 22, 25, 27, 30, 34, 35 and 40 degrees C. Pre-adult survivorship was greatest (95%) at 25 and 30 degrees C and shortest at 22 degrees C. Egg-to-adult time decreased within the range of 20 to 30 degrees C and at 34 degrees C it started to increase. The lower thermal threshold for egg-to-adult development was estimated at 16 and 18 degrees C by linear regression and the modified Logan model, respectively. The optimum temperature for egg-to-adult development was estimated at 32-33 degrees C by the modified Logan model. The influence of temperature on reproduction and longevity of C. claratris was determined at 25, 30 and 35 and 40 degrees C. Both inseminated and virgin females failed to reproduce at 40 degrees C. Virgin females produced only male offspring, confirming arrhenotoky. The sex ratio of the offspring of fertilized females was strongly female-biased, except at 25 degrees C. Mean total fecundity per female and mean daily total fecundity per female were highest for both virgin and inseminated females at 30 degrees C. Female longevity was longest at 25 degrees C and shortest at 40 degrees C. Male longevity was longest at 30 degrees C and shortest at 40 degrees C. The net reproductive rate (R0) and intrinsic rate of natural increase (rm) was greatest at 30 degrees C while, mean generation time (G) and the doubling time (t) were highest at 25 degrees C. The finite rate of increase (lambda) was fairly constant (1.1-1.5 days) over the three temperatures tested. The pest potential of C. claratris for tropical Asia is discussed.     

Effects of temperature and salinity on nitrogenous excretion by Litopenaeus vannamei juveniles

Excretion rates of ammonia-N, nitrite-N, nitrate-N, and dissolved organic nitrogen (DON) for juvenile Litopenaeus vannamei (3.85+/-0.83 g) were quantified in response to nine different combinations of temperature (24, 28, and 32 degrees C) and salinity (10, 25, and 40 ppt) under laboratory conditions. Results indicated that L. vannamei is ammonotelic, with ammonia-N accounting for 61.9-84.3% of total nitrogen (TN) excretion. There were significant effects of temperature and salinity, but no significant interaction between them, on ammonia-N excretion rate (R(AN)). R(AN) increased with increasing temperature, over the interval 24-32 degrees C. R(AN) was lower at 25 ppt than at 10 and 40 ppt, at all temperatures. DON excretion rate (R(DON)) was not significantly influenced by either temperature or salinity; the overall mean R(DON) was about 5.24 μg-N g -1 h -1. However, the percentages of DON in TN (P(DON)) varied from 15.4 to 36.4% under the various temperature-salinity combinations. P(DON) at 28 and 32 degrees C was significantly lower than at 24 degrees C, and P(DON) at 10 ppt was significantly lower than at 25 and 40 ppt. Only very small amounts of nitrogen were excreted by L. vannamei as nitrite-N and nitrate-N.     

Developmental and reproductive biology of Scirtothrips perseae (Thysanoptera: Thripidae): a new avocado pest in California

The developmental and reproductive biology of a new avocado pest, Scirtothrips perseae Nakahara, was determined in the laboratory at five constant temperatures, 15, 20, 25, 27.5 and 30 degrees C. At 20 degrees C, S. perseae exhibited greatest larval to adult survivorship (41%), and mated females produced a greater proportion of female offspring at this temperature when compared to 15, 25, 27.5 and 30 degrees C. Average lifetime fecundity and preoviposition period was greatest at 15 degrees C at 39.6 eggs per female and 17.6 days, respectively. Jackknifed estimates of net reproduction (Ro), capacity for increase (rc), intrinsic rate of increase (rm), and finite rate of increase (lambda) were all significantly greater at 20 degrees C than corresponding values at 15, 25 and 27.5 degrees C. Population doubling time (Td) was significantly lower at 20 degrees C, indicating S. perseae populations can double 33-71% faster at this temperature in comparison to 15, 25 and 27.5 degrees C. Mean adult longevity decreased with increasing temperature, from a maximum of 52.4 days at 15 degrees C to a minimum of 2.4 days at 30 degrees C. Developmental rates increased linearly with increasing temperatures for eggs and rates were non-linear for development of first and second instar larvae, propupae, pupae, and for egg to adult development. Linear regression and fitting of the modified Logan model to developmental rate data for egg to adult development estimated that 344.8 day degrees were required above a minimum threshold of 6.9 degrees C to complete development. An upper developmental threshold was estimated at 37.6 degrees C with an optimal temperature of 30.5 degrees C for egg to adult development. Unmated females produced only male offspring confirming arrhenotoky in S. perseae.     

Survival and development of horseshoe crab (Limulus polyphemus) embryos and larvae in hypersaline conditions

The horseshoe crab Limulus polyphemus spawns in the mid- to upper intertidal zone where females deposit eggs in nests below the sediment surface. Although adult crabs generally inhabit subtidal regions of estuaries with salinities from 5 to 34 ppt, developing embryos and larvae within nests are often exposed to more extreme conditions of salinity and temperature during summer spawning periods. To test whether these conditions have a negative impact on early development and survival, we determined development time, survival, and molt cycle duration for L. polyphemus embryos and larvae raised at 20 combinations of salinity (range: 30-60 ppt) and temperature (range: 25-40 degrees C). Additionally, the effect of hyperosmotic and hypoosmotic shock on the osmolarity of the perivitelline fluid of embryos was determined at salinities between 5 and 90 ppt. The embryos completed their development and molted at salinities below 60 ppt, yet failed to develop at temperatures of 35 degrees C or higher. Larval survival was high at salinities of 10-70 ppt but declined significantly at more extreme salinities (i.e., 5, 80, and 90 ppt). Perivitelline fluid remained nearly isoosmotic over the range of salinities tested. Results indicate that temperature and salinity influence the rate of crab development, but only the extremes of these conditions have an effect on survival.     

Carotenoid accumulation in the psychrotrophic bacterium Arthrobacter agilis in response to thermal and salt stress

A psychrotrophic strain of Arthrobacter agilis, isolated from Antarctic sea ice, grows from 5 degrees C to 40 degrees C and in culture media containing 0-10% (w/v) NaCl. Maximum growth rate occurred at 30-35 degrees C with a drastic decline as the cultivation temperatures diverged. Adaptation to extremes of low temperature may be partially attributed to the production of the C-50 carotenoid bacterioruberin, and its glycosylated derivatives. Lowering of the cultivation temperature resulted in a concomitant increase in carotenoid production, which may contribute to membrane stabilisation at low temperature. Maximum biomass accumulation occurred at 5-30 degrees C with a tenfold reduction at 40 degrees C. Changes in growth rates were minimal in culture media containing 0-2% (w/v) NaCl at 10 degrees C while a gradual decrease in growth rates occurred at higher salinity. Biomass accumulation at different salinity followed a trend similar to that observed with different cultivation temperatures. Maximum biomass accumulation was observed in culture media containing 0-5% (w/v) NaCl with a tenfold reduction at 10% (w/v) NaCl. Carotenoid production also decreased as salinity increased.     

Cryopreservation of mouse oocytes using a medium with low sodium content: effect of plunge temperature

The effect of various combinations of plunge temperature and thawing protocol on the survival and viability of mouse oocytes was examined. The oocytes were frozen either in a standard freezing medium (ETFM, embryo transfer freezing medium) or in a low-sodium, choline-based freezing medium (CJ2), with 1.5 M 1,2-propanediol and 0.1 M sucrose, and using a conventional slow cooling method. The criteria used to assess survival were morphological state after thawing (intact or lysed), ability to become fertilized, and ability to develop to the two-cell, morula, and blastocyst stage in vitro. Oocytes frozen in CJ2 and plunged into liquid nitrogen (LN(2)) from -10, -20, or -33 degrees C remained intact and developed to the blastocyst stage at significantly higher rates than oocytes frozen in ETFM. For oocytes plunged into LN(2) from -33 degrees C, very rapid thawing (10 s in 30 degrees C water) was more detrimental than rapid or slow thawing (holding in air at room temperature for 10 or 30 s, respectively, prior to submersion in water at 30 degrees C for 10 s). By contrast, oocytes plunged into LN(2) from -10 or -20 degrees C survived better when thawing was very rapid or rapid than when thawing was slow. With the current protocol CJ2 was very effective over a wide range of plunge temperatures (-20 to -33 degrees C), although the optimal thawing protocol depended on the particular plunge temperature. Over 90% of oocytes surviving after slow cooling in CJ2 to -33 degrees C could be plunged to -196 degrees C with little or no further damage.     

The effects of temperature upon the electrophysiological properties of Tetrahymena pyriformis-NT1

Cells of Tetrahymena pyriformis--NT1 were cultured at 38 degrees C (Tg 38 degrees C) and 20 degrees C (Tg 20 degrees C) and their properties investigated over the range 0-40 degrees C. Tg 20 degrees C cells were viable in the range 3-33 degrees C and changes in their properties were readily reversible between 10 degrees C and 30 degrees C. Tg 38 degrees cells were viable in the range 40-10 degrees C and their property changes were immediately reversible in the range 40-23 degrees C. The I-V relations of Tg 38 degrees C cells showed increased excitability as the cells were cooled from 40 degrees C. At 10 degrees C there was a considerable loss of excitability and slope resistance. Cooling Tg 20 degrees C cells from 20 degrees C gave a similar pattern, although over a narrower temperature range. Warming Tg 20 degrees C Tetrahymena above 20 degrees C led to a progressive loss of excitability and the cells were markedly less viable above 35 degrees C. Within physiological limits the regenerative spike magnitude, repolarization time, time to peak and input resistance increased as temperature was lowered, whereas resting potential was diminished. When compared at their growth temperatures and most intermediate temperatures, the value of the various parameters monitored were generally different for the two cultures. The Q10 value for resting potential changes of Tg 20 degrees C cells about 20 degrees C was 1.20. As in T. vorax this was significantly (P less than 0.01) greater than that predicted for a diffusion potential and suggested that T. pyriformis--NT1 may have an electrogenic pump component in its membrane potential.     

Effect of temperature on life history of the predatory mite Amblyseius (Neoseiulus) californicus (Acari: Phytoseiidae)

Amblyseius (Neoseiulus) californicus is an indigenous mite in Japan that feeds on many spider mite species. We evaluated the development, survivorship and life-history parameters of A. californicus on a diet of eggs of Tetranychus urticae (red form). More than 97.3% of A. californicus eggs hatched and more than 81.6% of newly hatched larvae attained maturity at temperatures between 15 and 35 degrees C. Females oviposited at 37.5 degrees C, but no eggs hatched. At 40 degrees C, no females laid eggs. The lower threshold temperature from egg to oviposition was 10.3 degrees C and the thermal constant was 86.2 degree-days. Based on these data, the maximum number of generations that could complete development in a year under field conditions in Ibaraki, central Japan, would be between 21 and 28. At 25 degrees C, females laid a mean of 41.6 eggs during a mean oviposition period of 19.4 days. The intrinsic rates of natural increase (rm) were 0.173 at 20 degrees C, 0.274 at 25 degrees C and 0.340 at 30 degrees C.     

Temperature-dependent development and population growth of Tetraneura nigriabdominalis (Homoptera: Pemphigidae) on three host plants

The root aphid Tetraneura nigriabdominalis (Sasaki) (Homoptera: Pemphigidae) is a pest of many Gramineae species; however, little is known about its biology and relationships with host plants. The objectives of this study were to quantify the effects of temperature on development, longevity, fecundity, and population growth of T. nigriabdominalis and to assess the effects of host plant on development of T. nigriabdominalis. The effects of temperature on performance of this root aphid were determined at 10, 15, 20, 25, 30, and 35 +/- 1 degrees C on rice roots, Oryza sativa L. Nymphal stages from birth to adult decreased from 46.3 d at 10 degrees C to 8.5 d at 30 degrees C. Aphid survival and development were lowest at 35 degrees C, and no aphid produced progeny at this temperature. Average adult longevity decreased from 23.3 d at 15 degrees C to 8.2 d at temperatures up to 35 degrees C. Average number of nymphs produced per female was highest at 25 degrees C; averaging near 30 nymphs per female, but it dropped to near zero at both 10 and 35 degrees C. The highest intrinsic rate of increase (r(m)) was 0.241 at 30 degrees C. Net reproductive rate (R(0)) ranged from 29.8 at 25 degrees C to 0.2 at 10 degrees C. The generation time (GT) decreased with increasing temperatures from 60.3 d at 10 degrees C to 13.8 d at 30 degrees C. In addition, root aphids reared at 30 degrees C on three host plants [O. sativa, Zea mays L. and Sorghum bicolor (L.) Moench] revealed that the developmental time of the nymphal stages averaged 6.9 d when reared on O. sativa and 10.7 d when reared on Z. mays. Comparison of the nitrogen content of the three host plants indicated that the root nitrogen content was highest in O. sativa. The effect of nitrogen content on aphid performance, however, is still not clear. Other factors, such as plant secondary chemistry, may play a role in affecting aphid performance.