不同食性甲虫的含能值、含水量及其变动规律研究

以干旱地区的肉食性步甲科(Carabidae)和植食性拟步甲科(Tenebrionidae)昆虫成体为材料,测定鞘翅目甲虫的含能值和含水量,分析其含能值和含水量的相互关系及其变动规律.结果表明,肉食性步甲科昆虫的含能值(22.64 J/mg无灰干重)显著高于植食性拟步甲科昆虫(20.55 J/mg无灰干重)(P<0.05),相反,前者的含水量(54.96%)却显著地低于后者(63.28%)(P<0.05).步甲科和拟步甲科昆虫的含能值都与其含水量成显著负相关(r=-0.5962,P<0.05).步甲科和拟步甲科昆虫的含能值或含水量具有明显的季节变动规律,两科的变动规律基本相同,其中,含能值在秋季最高(22.80 J/mg无灰干重),春季最低(20.42 J/mg无灰干重),含水量则相反,秋季最低(54.93%),春季最高(61.88%)(P<0.05).步甲科和拟步甲科昆虫的头、胸、腹和附肢不同体区的含能值具有显著差异(P<0.05),其中,腹部的含能值最高(22.65 J/mg无灰干重),其次为胸部(21.33 J/mg无灰干重),头部和附肢的含能值最低(20.89 J/mg无灰干重和20.60 J/mg无灰干重).不同体区的含能值也具有同样的季节变动,即含能值在秋季最高(22.30 J/mg无灰干重),春季最低(19.46 J/mg无灰干重)(P<0.05).步甲科和拟步甲科昆虫的个体含能值与其头、胸、腹和附肢各体区的含能值成正相关,相关系数分别为0.718、0.846、0.897和0.604(P<0.05);其中个体含能值与腹部或胸部体区含能值的相关系数显著地高于它们与头部和附肢含能值的相关系数(P<0.05);这些结果说明,脂质在甲虫腹部和胸部的积聚是引起甲虫个体含能值提高的主要原因.本文对不同食性甲虫含能值产生差异的原因,甲虫含能值和含水量变动的影响因素也进行了分析;并结合最佳摄食理论,就甲虫作为猎物,其含能值和含水量的这些变动规律对食虫动物食物选择所可能产生的影响也进行了探讨,就今后进一步检验食虫动物摄食对策所应开展的猎物喂养食虫动物的实验提出建议.

ENERGY DENSITY,WATER CONTENT AND THEIR VARIATIONS IN CARNIVOROUS AND HERBIVOROUS BEETLES

The energy density,water content and their variations of adult coleopteran insects were studied by determining carnivorous Carabidae and herbivorous Tenebrionidae in arid environment.The energy density of carnivorous Carabidae (22 64 J/mg AFDW) was significantly higher than herbivorous Tenebrionidae (20 55 J/mg AFDW),but their difference in water content (54 96% and 63 28% respectively) was converse ( P <0 05).The energy density in these two families of beetles correlated negatively to their water content ( r =-0 5962, P <0 05).Both the energy density and water content of these coleopteran insects exhibited significantly seasonal variations,in which the energy density was found maximum in autumn (22 80 J/mg AFDW) and minimum in spring (20 42 J/mg AFDW),conversely,the water content was lowest in autumn (54 93%) and highest in spring (61 88%) ( P <0 05).The energy density of different parts of body in these beetles also showed significant variations in which the energy density was highest in abdomen (22 65 J/mg AFDW) and then decreased in thorax (21 33 J/mg AFDW),head (20 89 J/mg AFDW) and legs (20 60 J/mg AFDW),and similarly,found maximum in autumn (22 30 J/mg AFDW) and minimum in spring (19 46 J/mg AFDW).The energy density of Carabidae and Tenebrionidae insects correlated positively to the energy density in their abdomen,thorax,head and legs ( r values were 0 897,0 846,0 718 and 0 604 respectively, P <0 05) in which the correlation coefficients of abdomen and thorax were significant higher than head and legs ( P <0 05).This results implied that main reason for the high energy density in beetles was the accumulated lipid in abdomen and thorax.In addition,the factors that affect the variations of energy density and water content,and the effects of these variations in these prey beetles on the food selection of insectivorous predators were also discussed.