昆虫神经肽研究进展

近年来鉴定了化学结构的昆虫神经肽数目呈快速上升趋势, 家蚕滞育激素和性信息素合成激活肽被分离纯化.三种近年出现的研究方法对寻找新型昆虫神经肽起到重要作用,已经成功地鉴定了数个新型神经肽.昆虫神经肽cDNA或基因组DNA克隆显示了新的结构信息和神经肽间的相互关系.     

Methoprene does not affect juvenile hormone titers in honey bee (Apis mellifera) workers

Methoprene, a juvenile hormone (JH) analog, is a widely used insecticide that also accelerates behavioral development in honey bees (Apis mellifera). JH regulates the transition from nursing to foraging in adult worker bees, and treatment with JH or methoprene have both been shown to induce precocious foraging. To determine how methoprene changes honey bee behavior, we compared JH titers of methoprene‐treated and untreated bees. Behavioral observations confirmed that methoprene treatment significantly increased the number of precocious foragers in 3 out of 4 colonies. In only 1 out of 4 colonies, however, was there a significant difference in JH titers between the methoprene‐treated and control bees. Further, in all 4 colonies, there was no significant differences in JH titers between precocious and normal‐aged foragers. These results suggest that methoprene did not directly affect the endogenous JH secreted by corpora allata. Because methoprene caused early foraging without changing workers’ JH titers, we conclude that methoprene most likely acts directly on the JH receptors as a substitute for JH.     

Color Processing in the Early Visual System of Drosophila

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Fusarium solani invader of the eggs of the insectPanstrongylus geniculatus in a vivarium

A strain ofFusarium solani sensu Snyder & Hansen invaded the eggs of the insectPanstrongylus geniculatus in a vivarium. None of the invaded eggs hatched. To establish experimentally the pathogenicity of thisFusarium species against the eggs ofP. geniculatus, the fungus and the eggs were incubated together under different relative humidities and temperatures. At 64% relative humidity and 26 °C, the fungus grew well colonizing and penetrating all of the chorions.Three embryos died and were also colonized byF. solani. Only 4 nymphs hatched and survived to day 20. It is concluded that the isolate ofF. solani was capable of colonizing and invading the chorion of the eggs under certain humidity and temperature conditions and cause the death of the embryos.     

The relationship of hemolymph osmotic pressure to spermatogenesis in the tobacco budworm,Heliothis virescens

The hemolymph osmotic pressure of male Heliothis virescens last instar larvae and pupae can be correlated with the state of spermatogenesis: intermediate (approx. 325 mOsm/kg) osmotic pressures are found in pre-meiotic animals, low (approx. 300 mOsm/kg) osmotic pressures characterize meiosis and elongation, and high (approx. 370 mOsm/kg) osmotic pressures, characterize the tests of diapausing pupae, where mature sperm have disappeared and only pre-meiotic sperm are found. In vitro studies show that, as the osmotic pressure of the medium is increased, spermatogenesis is inhibited and the survival of pre-meiotic cysts is enhanced. It is proposed that the osmotic pressure of the hemolymph plays a role in spermatogenesis and in the preservation of immature cysts during diapause.     

Sowing of margin strips rich in floral resources improves herbivore control in adjacent crop fields

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Optimal foraging and community structure: The allometry of herbivore food selection and competition

I address the selection of plants with different characteristics by herbivores of different body sizes by incorporating allometric relationships for herbivore foraging into optimal foraging models developed for herbivores. Herbivores may use two criteria in maximizing their nutritional intake when confronted with a range of food resources: a minimum digestibility and a minimum cropping rate. Minimum digestibility should depend on plant chemical characteristics and minimum cropping rate should depend on the density of plant items and their size (mass). If herbivores do select for these plant characteristics, then herbivores of different body sizes should select different ranges of these characteristics due to allometric relationships in digestive physiology, cropping ability and nutritional demands. This selectivity follows a regular pattern such that a herbivore of each body size can exclusively utilize some plants, while it must share other plants with herbivores of other body sizes. I empirically test this hypothesis of herbivore diet selectivity and the pattern of resource use that it produces in the field and experimentally. The findings have important implications for competition among herbivores and their population and community ecology. Furthermore, the results may have general applicability to other types of foragers, with general implications for how biodiversity is influenced.     

Relationships between ontogenetic changes in prey selection,head shape,sexual maturity,and colour in an Australasian python (Morelia viridis)

We describe a 15‐year study of the loss of reproductive fitness and population decline in Adenostoma sparsifolium, a rosaceous shrub endemic in the fire‐prone chaparral vegetation of southern California (USA) and adjacent northern Baja California, Mexico. Our studies of background extinction concentrated on small relict populations occurring in the eastern Santa Monica Mountains where reproduction is genetically compromised by uniquely high rates of embryonic/endosperm abortion (97–99%) resulting largely from self‐pollination in highly heterozygous populations. Environmental factors further reduce reproductive fitness. The relatively few viable seeds produced are not well adapted to survive wildfires that are a regular (approximately 21 years) occurrence in chaparral. Seedling recruitment after burning is rare and any established seedlings ultimately die from the annual 4–9‐month summer droughts typical of Mediterranean climates. Adult mortality is manifest from wildfire (approximately 6%) and occasional multiple‐year droughts (approximately 15%). Given the virtual absence of new post‐fire reproduction and a low but persistent rate of adult mortality, slow population demise resulting in background extinction is inevitable. We posit that A. sparsifolium is ecologically ‘out of place’ in the present chaparral environment and appears best adapted to a moister climate with summer rains and few wildfires that prevailed before the increasing aridity and warming from mid‐Holocene to the present. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 269–292.