区域气温和降水对关帝山不同海拔华北落叶松径向生长的耦合效应

为揭示区域气温和降水在不同海拔对山地林区林木径向生长的耦合效应,在关帝山林区孝文林场和庞泉沟国家自然保护区外围4个不同海拔选取立地条件相似的华北落叶松(Larix principis-rupprechtii Mayr.)人工林设置调查样地,采集典型样木样芯,采用建立年表的方法,获取年轮宽度指数,结合区域气温和降水进行相关性分析和单年分析。结果表明:在研究地区4个海拔上华北落叶松的径向生长均与区域气温和降水量有密切关系,但不同海拔响应机制不同;在1600 m海拔处,年轮宽度指数与当年4月气温极显著负相关,与当年9月降水量显著正相关;在1800 m海拔处,年轮宽度指数与上年6月气温显著负相关,降水量显著正相关;在2000 m海拔处,年轮宽度指数与当年9月气温和当年3月降水量显著负相关;在海拔2200 m处,年轮宽度指数与上年8月气温显著正相关,降水量显著负相关;随着海拔的升高,气温逐渐降低,降水量增加,两者对华北落叶松径向生长的耦合效应也发生变化,当海拔到达2000 m时,生长季降水量的增加使耦合效应关系发生转换。     

Why does the hoverfly Metasyrphus corollae migrate?

Abstract. 1. Migration pattern and mass appearance of the hoverfly Metasyrphus corollae (F.) (Diptera, Syrphidae) were investigated on the SE coast of Sweden in 1981. In total, 4433 hoverflies, belonging to fifteen species, were collected in water traps during 4–6 August. All but 2.2% were M.corollae , 3282 specimens being caught on 4 August, 1021 on 5 August and thirty-five on 6 August.
2. The sex ratios ( ♂/♀ ) on these dates were 1/1.6, 1/1.3 and 1/1.7. The average dry weights did not significantly differ between sexes (males 4.01 mg, females 4.02 mg).
3. M.corollae females were reproductively immature.
4. Females mostly had Senecio pollen in their guts while males mainly had Rubus pollen. The average number of pollen grains per specimen was 210 for females and 1100 for males.
5. In the summer 1980 aphids were numerous, forming a basis for a high abundance of adult hoverflies (with hibernating larvae) in 1981. Aphid density in 1981 was low and stimuli inducing egglaying were sparse. It is suggested that this pattern of aphid abundance triggers migration in M.corollae and in other aphidophagous species at irregular intervals.     

APOPTOSIS,REDIFFERENTIATION AND ARRESTING PROLIFERATION SIMULTANEOUSLY TRIGGERED BY OXIDATIVE STRESS IN HUMAN HEPATOMA CELLS

The effects of oxidative stress (ascorbic acid—ferrous system) on the proliferation, differentiation and apoptosis of the human hepatoma cell SMMC-7721 were studied. Oxidative stress significantly inhibited cell proliferation and induced morphological differentiation. Whatever the indices related with cell malignancy, such as α-fetoprotein and c-glutamyltranspeptidase or the index related with cell differentiation, such as tyrosine-α-ketoglutarate transaminase, all inclined evidently to normalization. The tumour's clonogenic potential decreased significantly. Moreover, together with differentiation, the phenomenon of apoptosis was found by the appearance of apoptotic bodies, detached cells, and apoptotic morphological feature. Although, their DNA was not degraded into oligonucleosomal fragmentation, the DNA was cut into larger fragments (about 21.2kbp) of a size associated with chromatin loops. These findings indicated that oxidative stress can induce both differentiation and apoptosis simultaneously in tumour cells. All the results showed that oxidative stress may initiate the tumour cells reverse transformation. The possible mechanism of the differentiation and apoptosis induced by oxidative stress may be related to the lipid peroxidation of cell membrane.     

EXTRA-ECTODERMAL STRANDS IN THE CILIATED BANDS OF THE ECHINOPLUTEUS

An ectodermal nerve net and some extra-ectodermal, axon-like elements have been demonstrated in the ciliated bands of Psammechinus miliaris larvae. It is proposed that these extraectodermal structures, together with the microvillous epithelial cells and the ectodermal nerves, participate in the co-ordination of responses on sensory stimulation from the outside of the larvae.     

Nuptial gift size prolongs copulation duration in the dance fly Empis borealis

Abstract. 1. The time that pairs of the dance fly Empis borealis (L.) (Diptera: Empididae) spent in copula was positively correlated with the volume of the nuptial gift.
2. In some cases the copulation duration was short although prey volume was large. Females engaged in these matings had more worn wings, were therefore older, and most probably had sperm already stored in the spermatheca. It is suggested that these copulations were interrupted because either the spermatheca was full of sperm and the male was not able to transmit any sperm, or because prey content was depleted (males may have fed on the prey or the prey had been used in a previous mating). The latter explanation seemed more probable.
3. A male providing a large nuptial gift may transfer larger quantities of sperm. Quantitative sperm competition is more likely than last-male sperm predominance.     

One and the same: integrative taxonomic evidence that Bactrocera invadens (Diptera: Tephritidae) is the same species as the Oriental fruit fly Bactrocera dorsalis

The invasive fruit fly Bactrocera invadens Drew, Tsuruta & White, and the Oriental fruit fly Bactrocera dorsalis (Hendel) are highly destructive horticultural pests of global significance. Bactrocera invadens originates from the Indian subcontinent and has recently invaded all of sub‐Saharan Africa, while B. dorsalis principally occurs from the Indian subcontinent towards southern China and South‐east Asia. High morphological and genetic similarity has cast doubt over whether B. invadens is a distinct species from B. dorsalis. Addressing this issue within an integrative taxonomic framework, we sampled from across the geographic distribution of both taxa and: (i) analysed morphological variation, including those characters considered diagnostic (scutum colour, length of aedeagus, width of postsutural lateral vittae, wing size, and wing shape); (ii) sequenced four loci (ITS1, ITS2, cox1 and nad4) for phylogenetic inference; and (iii) generated a cox1 haplotype network to examine population structure. Molecular analyses included the closely related species, Bactrocera kandiensis Drew & Hancock. Scutum colour varies from red‐brown to fully black for individuals from Africa and the Indian subcontinent. All individuals east of the Indian subcontinent are black except for a few red‐brown individuals from China. The postsutural lateral vittae width of B. invadens is narrower than B. dorsalis from eastern Asia, but the variation is clinal, with subcontinent B. dorsalis populations intermediate in size. Aedeagus length, wing shape and wing size cannot discriminate between the two taxa. Phylogenetic analyses failed to resolve B. invadens from B. dorsalis, but did resolve B. kandiensis. Bactrocera dorsalis and B. invadens shared cox1 haplotypes, yet the haplotype network pattern does not reflect current taxonomy or patterns in thoracic colour. Some individuals of B. dorsalis/B. invadens possessed haplotypes more closely related to B. kandiensis than to conspecifics, suggestive of mitochondrial introgression between these species. The combined evidence fails to support the delimitation of B. dorsalis and B. invadens as separate biological species. Consequently, existing biological data for B. dorsalis may be applied to the invasive population in Africa. Our recommendation, in line with other recent publications, is that B. invadens be synonymized with B. dorsalis.     

SOME ASPECTS ON PIGMENT CELL DISTRIBUTION AND FUNCTION IN THE DEVELOPING ECHINOPLUTEUS OF PSAMMECHINUS MILIARIS

Pigment cells in Psammechinus miliaris larvae are frequently found in regions which are morphogenetically active. They can be seen in living larvae from the the midgastrula stage up to metamorphosis. Their early development and typical characters as seen by the electron microscope are described. Histochemical methods have revealed carotenoids which are preferentially located in the pigment granules. The findings are discussed in relation to published data on photopigments. It is suggested that caroteno-proteins of the pigment cells are involved in photo-activated processes which support larval migration and/or morphogenesis.