Singh Shashwat, Mishra Geetanjali
Ladybird Research Laboratory, Department of Zoology, University of Lucknow, Lucknow 226007, India.
J Therm Biol. 2018 Jan;71:180-188. doi: 10.1016/j.jtherbio.2017.11.010. Epub 2017 Nov 21.
All organisms are exposed to daily as well as seasonal variation in temperature in nature. However, ectotherms are strongly affected by temperature and its variations. Most laboratory studies on effect of temperature on life history traits employ constant instead of fluctuating temperature regimes, though the latter is more reflective of nature. We conducted investigations on the effect of constant, fluctuating and alternate temperature regimes on reproductive and developmental attributes of a biocontrol agent ladybird, Menochilus sexmaculatus (Fabricius) (Coleoptera: Coccinellidae). We used three constant, viz. cold, optimum and hot (15°C, 27°C and 35°C); two fluctuating with variation in mean temperature of the day (15°C/27°C, 35°C /27°C; 10/14h) and three alternating (15°C/27°C, 35°C/27°C, 15°C/35°C; 24/24h) temperatures to evaluate their effects on these life attributes. Oviposition and percent egg viability along with offspring development (immature life stages developmental time and developmental rate) and elytral colouration pattern of adults were observed. The best response in terms of oviposition and percent egg viability was recorded at the constant temperature of 27°C followed by the fluctuating regime with a mean temperature of 30.3°C. The fastest development was found at a constant temperature of 35°C, followed by a fluctuating temperature of 35°C/27°C for 10/14h. Among the different temperature cycles, the most uncustomary trend of oviposition and percent egg viability was recorded on an alternate temperature of 15°C/35°C for 24/24h. The constant (27°C) and fluctuating (35°C/27°C for 10/14h) temperatures caused an incremental effect on reproductive output and developmental rate. This study demonstrates that M. sexmaculatus is able to adjust its physiology according to surrounding environmental conditions and acclimatizes well with the fluctuating/alternate temperatures suggesting its wide range of tolerance. The findings of present work would be helpful in augmenting population dynamics of this biocontrol agent to suppress insect pest.
在自然界中，所有生物都会经历每日以及季节性的温度变化。然而，变温动物受温度及其变化的影响很大。尽管波动温度更能反映自然情况，但大多数关于温度对生活史特征影响的实验室研究采用的是恒定温度而非波动温度。我们研究了恒定、波动和交替温度对一种生物防治剂瓢虫，即六斑月瓢虫（Fabricius）（鞘翅目：瓢虫科）的生殖和发育特性的影响。我们使用了三种恒定温度，即低温、最适温度和高温（15℃、27℃和35℃）；两种波动温度，日平均温度有变化（15℃/27℃，35℃ /27℃；10/14小时），以及三种交替温度（15℃/27℃，35℃/27℃，15℃/35℃；24/24小时）来评估它们对这些生活特性的影响。观察了产卵量、卵的存活率百分比，以及后代发育情况（未成熟阶段的发育时间和发育速率）和成虫的鞘翅颜色模式。在产卵量和卵的存活率百分比方面，最佳反应出现在27℃的恒定温度下，其次是平均温度为30.3℃的波动温度条件。发育最快的是在35℃的恒定温度下，其次是10/14小时的35℃/27℃波动温度。在不同的温度循环中，产卵量和卵的存活率百分比最不寻常的趋势出现在24/24小时的15℃/35℃交替温度下。恒定温度（27℃）和波动温度（10/14小时的35℃/27℃）对生殖产量和发育速率有递增效应。这项研究表明，六斑月瓢虫能够根据周围环境条件调整其生理状态，并能很好地适应波动/交替温度，这表明它具有广泛的耐受性。本研究结果将有助于增加这种生物防治剂的种群动态，以抑制害虫。
