Persistence of occluded viruses in the nests of the paper waspPolistes hebraeus (Hym.: Vespidae)

Bioassays were used to study the infectivity of cytoplasmic polyhedrosis viruses (CPVs), nuclear polyhedrosis viruses (NPVs) and entomopoxviruses (EPVs) contained in 16 nests of the paper waspPolistes hebraues F. in Réunion Island. Several virosis were propagated from 6 nest contents in 5 Lepidoptera:Catopsilia thauruma Saalmüller,Catopsilia florella F.,Callixena versicolora Mabille,Polydesma umbricola Boisduval andEagris sabadius Boisduval. Each of the previous species supported the development of one or two virosis and therefore, wasp nests must be considered as accumulating centres where infectivity of occluded entomoviruses is preserved. The accurate origin of the virosis propagated through bioassays was searched for using ecological investigations on similar natural diseases, REN analysis and a cross-transmission test onSpodoptera mauritia Boisduval. The nuclear polyhedrosis and one cytoplasmic polyhedrosis appearing in bioassays can be assigned respectively to viruses produced byC. thauruma andC. versicolora; the other virosis must be considered as developing in alternate or substitution hosts. Wasp nests could therefore be used to detect the presence of specific viruses in an environment and to collect new virus isolates.     

Queen succession in the primitively eusocial tropical waspRopalidia marginata (Lep.) (Hymenoptera: Vespidae)

Females of the primitively eusocial wasp Ropalidia marginata can be classified into three behavioral groups: Sitters, Fighters, and Foragers. It has been speculated that both Sitters and Fighters may be hopeful queens and that the Foragers may have little or no opportunities for direct reproduction. Here we show that in 9 of 12 queen-removal experiments where such a behavioral differentiation could be discerned, the individual that became a queen (the potential queen) was a Sitter in 6 cases, a Fighter in 2 cases, and a Forager in only 1 case. Although potential queens spent significantly more time absent from the nest and showed significantly higher rates of dominance behavior compared to the mean values for nonqueens in their colonies, they were intermediate with respect to all behaviors and age when compared to the range of values for nonqueens in their colonies. Potential queens were not necessarily the highest-ranking individuals among the nonqueens. The pattern of queen succession in this species appears to be quite different from the temperate pattern, where an old and active forager of high dominance rank is the potential queen. Although somewhat similar to the tropical pattern of a relatively younger female that has performed relatively little foraging being the potential queen, it is perhaps more accurate to describe the potential queens of R. marginata as unspecialized intermediates.     

Figs (Ficus spp.) and fig wasps (Chalcidoidea, Agaonidae): hypotheses for an ancient symbiosis

Figs and their pollinating fig wasps are dependent on one another for propagation of their own kinds. The wasps reproduce by ovipositing through the styles of female flowers within the closed fig receptacles (syconia). About half of the female flowers within the syconia of monoecious figs have styles which are longer than the ovipositors of the wasp, and they will therefore produce seeds rather than wasp larvae. Since a longer ovipositor would enable a wasp to reach more ovules and deposit more eggs, the question arises at to why longer ovipositors have not evolved.
In an attempt to answer this question, four seemingly plausible hypotheses are examined but each is shown to be problematical in some way. Consideration is then given to a fifth hypothesis which proposes that ovipositor length is constrained by abortion of syconia with relatively few seed embryos and many agaonid larvae. It is argued first that this pattern of abortion will be selected during a sustained period of heavy wasp infestation because seeds will then become scarce relative to pollen-carrying wasps. Increased expenditure by the fig on seed production would therefore be favoured by natural selection. A greater expenditure on seeds would occur if young syconia with exceptionally heavy wasp infestations were dropped and the saved nutrients invested in syconia of a subsequent crop containing average levels of wasp larvae and seeds. Provided that the energy and nutrient cost of dropping young syconia is small, the selective advantage to the wasp of longer ovipositors is eliminated in this way. A stable coexistence of figs and wasps is therefore possible. The paper concludes by discussing two general predictions of the abortion hypothesis, and how these may be tested.     

Distribution and fitness effects of the son-killer bacterium inNasonia

Summary Maternally inherited microorganisms that kill male (but not female) progeny are widespread in nature. Three hypotheses have been proposed for the evolution of male-killing microorganisms: inbreeding reduction, release of resources to remaining females and inoculum for horizontal transmission. The sonkiller bacterium,Arsenophonus nasoniae, is a maternally inherited bacterium that causes lethality of male embryos of infected females in the parasitoid wasp,Nasonia vitripennis. In this paper we describe the geographical distribution and frequency of the son-killer bacterium in North American populations ofN. vitripennis andNasonia longicornis. We tested the resource release hypothesis using the body size measurements of infected and uninfected females from natural populations. No evidence was found for a fitness increase of females infected with the bacterium compared to uninfected females. We propose a modification of the existing models, termed the incremental gain hypothesis. According to this model, the bacteria are maintained in host populations due to horizontal transmission and male killing provides an incremental gain in the fitness of infected females relative to females infected with non-male-killing bacteria.     

A nectar-secreting gall wasp and ant mutualism: selection and counter-selection shaping gall wasp phenology, fecundity and persistence

Abstract.

• 1 The natural history of a gall wasp including interactions with inquilines, parasites, and a mutualistic ant are examined. The stability of the system is described from the perspective of influences on gall wasp life history characteristics.
• 2 An exclusion experiment demonstrated that the nectar-secreting gall of Disholcaspis perniciosa mediates a mutualism with the tending ant, Formica obscuripes. Survivorship increased from 0% in the absence of ants to 25.3% in their presence, largely due to the exclusion of inquilines.
• 3 Specialized parasites, Eudecatoma spp., attacked before the ant-gall interaction began, when the developing gall was still beneath the host plant (Quercus gambellii) epidermis and ants were not in attendance. They may select for later developing gall wasps, which benefit by having fewer individuals parasitized. However, counter-selection for earlier development may result from decreased gall wasp size, decreased fecundity, and an increase in gall failures resulting from late development.
• 4 Local persistence of the gall wasp population despite increased pressure from inquilines and parasites was attributed to gall wasp escape in time due to polymorphic emergence resulting from diapause. Most individuals emerge at the end of the summer, but approximately 15% remain in the galls as prepupae for 1–5 years.

     

Tachykinin NK-1 receptor probed with constrained analogues of substance P

The action of rotameric probes introduced either in position 7 or 8 in the sequence of substance P (SP) was investigated, i.e. -tetrahydroisoquinoleic acid (Tic), -fluorenylglycine (Flg), -diphenylalanine (Dip), the diastereoisomers of -1-indanylglycine (Ing) and -benz[ƒ]indanylglycine (Bfi), the Z- and E-isomers of dehydrophenylalanine and dehydronaphthylalanine (Δ^ZPhe, Δ^EPhe, Δ^ZNal, Δ^ENal) and (Dmp). The aim of this study was the topographical characterization of the binding subsites of human NK-1 receptor expressed in CHO cells, especially the S₇ and S₈ subsites, corresponding to residues Phe⁷ and Phe⁸ of substance P. According to the binding potencies of these substituted-SP analogues, the S₇ binding subsite is smaller than the S₈ subsite: the S₇ subsite accepts only one aromatic nucleus, while the S₈ can accommodate three coplanar nuclei altogether. These findings are compatible with the idea that the S₈ binding subsite may reside in the extracellular loops of the hNK-1 receptor. NK-1 agonists bind to human NK-1 receptor and activate the production of both inositol phosphates and cyclic AMP. As already quoted for septide, [pGlu⁶, Pro⁹]SP(6–11), discrepancies are observed between affinity (K_i) and activity (EC₅₀) values for IPs production. While a weak correlation between K_i and EC₅₀ values for IPs production could be found (r = 0.70), an excellent correlation could be demonstrated between their affinities (K_i) and their potencies (EC₅₀) for cAMP production (r = 0.97). The high potency (EC₅₀) observed for ‘septide-like’ molecules on PI hydrolysis, compared to their affinity is not an artefact related to the high level of NK-1 receptors expressed on CHO cells since a good correlation was found between EC₅₀ values obtained for PI hydrolysis and those measured for spasmogenic activity in guinea pig ileum bioassay (r = 0.94).

According to the binding potencies of constrained analogues of phenylalanine, the S₇ binding subsite of human NK-1 receptor is small, whereas the S₈, which can accommodate three coplanar nuclei, might probably reside in the extracellular loop. The discrepancies observed between affinity (K_i) and activity (EC₅₀) values for IPs production are not an artefact of CHO cells since a good correlation was found between EC₅₀ for PI hydrolysis and those measured in guinea pig ileum bioassay.     

Fitness effects of sex ratio response to host quality and size in the parasitoid wasp Spalangia cameroni

The parasitoid wasp Spalangia cameroni oviposited a greaterproportion of daughters in stable fly pupae than in house flypupae, even when I controlled for stable flies being smallerthan house flies. Sex ratio manipulation in response to hostquality has been modeled as being adaptive through an effectof host quality on the size and hence offspring production ofdaughters. 5. cameronis response to host species may insteadbe adaptive through an effect on larval survivorship, the developmenttime of daughters, and the size of sons. There was greater survivalof daughters than sons on stable flies. Controlling for hostsize, I found that development time of daughters was about 2%less on stable flies than on house flies. The decrease in developmenttime corresponds to a 2% increase in fitness as estimated byr, the intrinsic rate of increase, and is equivalent to abouta 9% increase in offspring production. Sons were about 2% largerfrom house flies than stable flies, which may increase offspringproduction by up to 3%. Host species had no consistent effecton size of daughters or development time of sons. In additionto the response to host species, mothers oviposited a greaterproportion of daughters in larger stable fly hosts. Whetherthis behavior is adaptive is unclear. Although offspring werelarger when they developed on larger stable flies, the rateof increase was less for daughters dian for sons. Effects ofstable fly size on offspring development time were negligible.     

Alternaria infectoria , a Promising Biological Control Agent for the Fig Wax Scale, Ceroplastes rusci (Homoptera: Coccidae), in Egypt

Alternaria infectoria E . G . Simmons was isolated from naturally infected eggs of the fig wax scale insect , Ceroplastes rusci L . (Homoptera: Coccidae) , that were showing different degrees of shriveling . This fungus proved to be pathogenic to eggs , nymphs and adults of this pest . The fungus had significant effects on both the mortality and hatchability of the eggs ( P = 0 . 0001) . Three days after exposure to the fungus , nearly one - third (31 . 5%) of the fungus - treated eggs became discolored and 17% showed moderate shrinking but no mortality . Fifteen days post - application , 91% of the fungus - treated eggs were diseased (74 . 8% of them were dead) due to A. infectoria, while no disease developed on the untreated eggs . Hatching decreased by 39 . 6% over a 15 - day period in the fungus - treated eggs compared to the control . Additionally , crawlers hatching from fungus - treated eggs became infected . The fungus seemed to induce crawlers to enter the settling stage . Seventy - two per cent of the fungus - treated crawlers versus 9% of the untreated controls entered the settling stage 6 days after exposure to the fungal inoculum . The highest level of nymphal mortality attributed to A. infectoria occurred when 30% (wet w:v blended mycelium in water containing 0 . 5% w:v Metamucil) inoculum was applied , and a high relative humidity was maintained for the following 48 h . This is the first record of A. infectoria on the fig wax scale and for the genus Alternaria as an entomopatho genic fungus .