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.     

Why do males of the dance flyEmpis borealis refuse to mate? The importance of female age and size

Empis borealisfemales form swarms, and males carrying a nuptial gift come to swarms to mate. Males either mated with one of the females (accepted swarms) or left swarms without mating (refused swarms). Males mated with the younger (low wing-wear) and relatively larger females in accepted swarms. They seemed to be able to judge the relative size of the females but to ignore their absolute size. Visiting males stayed shorter in accepted swarms as female size variation increased. This probably reflects their greater ease in choosing a mate among females of relatively different sizes. Females in accepted swarms tended to be larger and to have less worn wings than females in rejected swarms.     

Development of twenty-five polymorphic microsatellite markers for the endangered red-cockaded woodpecker (Picoides borealis)

Twenty-five polymorphic microsatellite markers were developed for the endangered red-cockaded woodpecker (Picoides borealis). The number of alleles ranged from two to five and observed heterozygosities ranged from 0.036 to 0.750. These loci should be useful tools for conducting research towards the management and conservation of this species.     

Globin evolution in the genusXenopus: Comparative analysis of cDNAs coding for adult globin polypeptides ofXenopus borealis andXenopus tropicalis

Summary Globin mRNAs ofXenopus borealis andXenopus tropicalis have been cloned and sequenced. The nucleotide and derived amino acid sequences were compared with each other and with already available data fromXenopus laevis. This analysis rendered clear evidence that the common ancestor ofX. laevis andX. borealis, but not ofX. tropicalis, had lost one amino acid of the -globins prior to a genome duplication event that preceded the segregation of the former two species. Replacement-site substitutions were used to calculate a rough time scale of genome duplication and species segregation. The results suggest an ancient separation between theX. laevis and theX. tropicalis groups occurring approximately 110–120 million years ago. Analysis of the amino acid chains demonstrated various alterations. However, some functional domains, like heme-binding sites and₁₂ contact sites, were subject to a high degree of conservation, indicating the existence of functional constraints on them also in the genusXenopus.     

Post-fertilization functions of annulate lamellae in the periphery of the egg of Spirorbis borealis (Daudin) (Serpulidae=Annelida)

Summary Post-fertilization changes in the periphery of the egg of Spirorbis borealis are described. The nuclear envelope and cell membrane are formed by the coalescence of short strands of membrane perhaps produced by the Golgi complex. Annulate lamellae are abundant in the forming cells giving rise to endoplasmic reticulum and apparently contributing to genesis of mitochondria. This possibility is discussed.We are grateful to Professor E. W. Knight-Jones in whose department the work was carried out.     

Field Release and Establishment of the Decapitating Fly Pseudacteon curvatus on Red Imported Fire Ants in Florida

Decapitating phorid flies in the genus Pseudacteon are being studied as classical biological control agents of the red imported fire ant, Solenopsis invicta Buren (Hymenoptera: Formicidae). Pseudacteon curvatus Borgmeier (Diptera: Phoridae) is a small decapitating fly that attacks small fire ant workers. We released a biotype of P. curvatus from Formosa, Argentina, at three sites near Gainesville, FL. Field releases were conducted in the spring and summer of 2003 and monitored monthly. Flies were discovered within 5 weeks at the spring site and then monthly thereafter. By late spring 2004, flies released at this site had expanded 1.6 km both north and south and about 0.8 km westward. Initially, we found no flies from the two summer 2003 releases but we were successful at finding them 8 months after release during spring 2004. This paper documents the first successful release(s) of P. curvatus on red imported fire ants in the United States.     

Microsatellite Analysis of Olive Fly Populations in the Mediterranean Indicates a Westward Expansion of the Species

Bactrocera oleae is the major insect pest of the olive fruit. Twelve microsatellite loci isolated from the genome of this insect were used in a Mediterranean-wide population analysis. These loci were highly polymorphic with a mean number of alleles per locus of 10.42 and a mean effective number of alleles of 2.76. The analysis was performed on a sample of 671 flies collected from nineteen locations around the European part of the Mediterranean basin. Despite the high level of gene flow across the Mediterranean, results support the notion of a differentiation of three subpopulations: one of the Iberian Peninsula, one of Greece and Italy and one of Cyprus. In addition, the gradual decrease of heterozygosity from the Eastern to the Western part of the Mediterranean indicates a westward expansion of the species.     

Sex and environmental sensitivity in blue tit nestlings

In birds and mammals with sexual size dimorphism (SSD), the larger sex is typically more sensitive to adverse environmental conditions, such as food shortage, during ontogeny. However, some recent studies of altricial birds have found that the larger sex is less sensitive, apparently because large size renders an advantage in sibling competition. Still, this effect is not an inevitable outcome of sibling competition, because several studies of other species of altricial birds have found the traditional pattern. We investigated if the sexes differ in environmental sensitivity during ontogeny in the blue tit, a small altricial bird with c. 6% SSD in body mass (males larger than females). We performed a cross-fostering and brood size manipulation experiment during 2 years to investigate if the sexes were differently affected as regards body size (body mass, tarsus and wing length on day 14 after hatching) and pre-fledging survival. We also investigated if the relationship between body size and post-fledging survival differed between the sexes. Pre-fledging mortality was higher in enlarged than in reduced broods, representing poor and good environments, respectively, but the brood size manipulation did not affect the mortality rate of males and females differently. In both years, both males and females were smaller on day 14 after hatching in enlarged as compared to reduced broods. In one of the years, we also found significant Sex × Experiment interactions for body size, such that females were more affected by poor environmental conditions than that of males. Body size was positively correlated with post-fledging survival, but we found no interactive effects of sex and morphological traits on survival. We conclude that in the blue tit, females (the smaller sex) are more sensitive to adverse environmental conditions which, in our study, was manifest in terms of fledgling size. A review of published studies of sex differences in environmental sensitivity in sexually size-dimorphic altricial birds suggests that the smaller sex is more sensitive than the larger sex in species with large brood size and vice versa.     

遗传位点影响小鼠对约氏疟原虫易感性的研究

探讨Listr1遗传位点影响小鼠对疟原虫易感性的可能性及其初步作用机制。致死型约氏疟原虫(Plasmodium yoelii 17XL,P.y17XL)感染C.B6By Listr1小鼠（BALB/c小鼠基因背景下引入C57BL/6小鼠Listr1遗传位点的同类系小鼠）和BALB/c小鼠,分析二者生存率和感染率的差异;HE染色分析P.y17XL感染后第5天C.B6By Listr1小鼠和BALB/c小鼠肝脏组织损伤情况;定量PCR法检测P.y17XL感染后小鼠肝脏组织第1、2、5天IL-1β、IL-6、TNF-α、IFN-γ的表达含量。结果显示,P.y17XL感染后4~8 d C.B6By Listr1小鼠虫血症水平显著高于BALB/c小鼠（P＜0.05）。C.B6By Listr1小鼠于感染后7~9 d全部死亡;而半数BALB/c小鼠于感染后8~9 d死亡,其余BALB/c小鼠至感染后第13天仍存活,两种小鼠生存率差异具有统计学意义（P＜0.01）。C.B6By Listr小鼠P.y17XL感染后第5天肝组织HE染色可见到明显的疟色素沉积;而BALB/c小鼠全片基本未见到疟色素的沉积。P.y17XL感染后第2天BALB/c小鼠肝组织IL-6（P＜0.05)、TNF-α（P＜0.05)mRNA水平显著高于C.B6By Listr1小鼠。结果表明Listr1遗传位点可以影响小鼠对疟原虫的易感性,与肝脏固有免疫相关。