Transient nestmate recognition cues contribute to a multicolonial population structure in the ant,Leptothorax curvispinosus

Summary Individual nests of the facultatively polygynous and polydomous ant, Leptothorax curvispinosus, were mapped at two sites, collected, and maintained under uniform laboratory conditions. Tests of worker acceptability between nests were conducted 2–4 weeks and 13–17 weeks after collection. Nests collected near to one another (0.09–1.87 m) were sometimes nonaggressive, and were significantly less aggressive than those from different sites (7 km apart); and there was no significant difference in aggressiveness between tests for these distance categories. However, aggression between nests collected farther away from one another at the same site (1.52–4.65 m) decreased significantly between tests: initially, the level of aggressiveness was equivalent to that between nests from different sites but later it was reduced to that between near nests. These results indicate that polydomous colonies of this species occur within multicolonial populations; and that colony segregation within local populations is largely maintained by transient environmentally-based nestmate recognition cues. More stable cues of genetic or environmental origin (or both) are also present and contribute to discrimination even after extended periods of culture under uniform conditions. These results suggest that the maintenance of colony autonomy within genetically highly interrelated populations may be the prime function of environmentally-based nestmate recognition cues. Colony autonomy under such circumstances may be important to maintain a relatively small but optimal colony size, or because the mechanisms which regulate colony growth, development, etc., require a limited colony size.     

Duetting in the subdesert mesite Monias benschi: evidence for acoustic mate defence?

Despite numerous hypotheses proposed for the function of duets, there is currently no consensus as to why males and females should coordinate their songs in such a precise way. There is evidence indicating that duets sometimes serve in territory defence, but additional functions are rarely considered. The mate-defence hypothesis proposes that birds sing in response to their partner's song and the resulting duet repels rivals and may prevent desertion of a partner. We investigated this idea in the subdesert mesite Monias benschi using playback experiments in which we broadcast recordings of solos and duets to single birds and groups. Two predictions of the hypothesis were met: (1) the solo songs of both sexes incited aggressive responses from paired birds of the same sex; and (2) compared to solo songs, pair duets elicited weaker responses from groups and duetting pairs. However, groups responded to male duets with a vigour equal to that with which they responded to male solos. This indicated that the weaker responses of groups to pair duets compared to male solos was a function of the sex rather than number of vocalising birds. Groups responded more strongly to male solos than to either female solos or pair duets, and females' responses were generally weaker than those of males. This may reflect stronger competition among males for mates, due to a male-biased sex ratio in the population. We conclude that song serves similar functions in each sex and that duets may arise through mutual mate defence.     

The outcome of in-vitro contests between larvae of the endoparasitoid<Emphasis Type="Italic"> Venturia canescens</Emphasis> depends on both their relative and absolute ages

In a laboratory colony of the asexual solitary endoparasitoid Venturia canescens Grav. (Hymenoptera: Ichneumonidae), two genetically and phenotypically distinct lines (RP and RM) appear to coexist sympatrically, with the reproductive success of the RM-line being greater under con-specific superparasitism but lower under self superparasitism. To investigate the basis of the RM-lines advantage under con-specific superparasitism, we examined the outcome of inter-larval physical combat under in-vitro conditions. The results showed that the outcome depended on both the relative and absolute ages of the contestants, and that the competitive abilities of the two lines were not symmetric. In contests involving a larva and an egg, the unhatched wasp lost. In contests involving two larvae, at least one of which was newly hatched, the RP-larva tended to lose. Finally, if both larvae were at least 8–10 h post-hatching when the contest occurred, then the larger larva tended to lose, with the probability increasing with the difference in length between the two larvae. Thus, the higher reproductive success of the RM-line under competing superparasitism with the RP-line is due to a physiological difference between the newly hatched larvae of the two lines, which results in an advantage to the RM-larva independent of the order or time interval between ovipositions.Communicated by P. Heeb     

Compositional Limitations in Poly–3–Hydroxyalkanoates Produced by Pseudomonas oleovorans

It is well known that Pseudomonas oleovorans can utilize sodium octanoate for both cell growth and the synthesis of polyhydroxyalkanoates (PHAs), but it can utilize sodium butyrate only for limited cell growth and not for the polyester formation when this substrate is the sole carbon source. Therefore, these two substrates were evaluated as cofeeds for the possible incorporation of 3-hydroxybutyryl groups in the resulting PHA. When sodium butyrate and sodium octanoate were fed to P. oleovorans as cosubstrates in various proportions, the resultant cell density and polymer content were proportional to the amount of sodium octanoate in the feed. The PHA extracted from cells grown in all combinations of these cosubstrates had similar unit compositions of approximately 8 mole % 3-hydroxyhexanoate, 91 mole % 3-hydroxyoctanoate and 1 mole % 3-hydroxydecanoate. 3-Hydroxybutyrate units were not detected in any of the PHAs isolated, indicating that these units could not be incorporated in the copolymer synthesized by P. oleovorans either because the cell did not synthesize that monomer or, if it did, the PHA synthase could not copolymerize it with the longer chain monomers.     

Gastroliths in<Emphasis Type="Italic"> Yanornis</Emphasis>: an indication of the earliest radical diet-switching and gizzard plasticity in the lineage leading to living birds?

Yanornis martini is an Early Cretaceous basal ornithurine bird. Its fish-eating diet was previously recognized from a discrete mass of disarticulated fish remains discovered in its abdominal region. A new complete and articulated specimen of Yanornis martini preserves abundant in-situ gastroliths such as have been associated with a herbivorous diet. We suggest that the occurrence of gastroliths in this specimen, fish remains in a second, and the lack of gastroliths in three others, is consistent with diet-switching in Yanornis martini. Incompatibility of the preserved data with explanations of the grit as an artifact of preservation or result of accidental ingestion is discussed. This discovery indicates the earliest presence of intermittent diet change (and associated gizzard plasticity) observed in extant birds seasonally and in response to changes in available food sources.     

Diphenylamine and derivatives in the environment: a review

Diphenylamine (DPA) is a compound from the third European Union (EU) list of priority pollutants. It was assigned by the EU to Germany to assess and control its environmental risks. DPA and derivatives are most commonly used as stabilizers in nitrocellulose-containing explosives and propellants, in the perfumery, and as antioxidants in the rubber and elastomer industry. DPA is also widely used to prevent post-harvest deterioration of apple and pear crops. DPA is a parent compound of many derivatives, which are used for the production of dyes, pharmaceuticals, photography chemicals and further small-scale applications. Diphenylamines are still produced worldwide by the chemical industries. First reports showed that DPA was found in soil and groundwater. Some ecotoxicological studies demonstrated the potential hazard of various diphenylamines to the aquatic environment and to bacteria and animals. Studies on the biodegradability of DPA and its derivatives are very sparse. Therefore, further investigation is required to determine the complete dimension of the potential environmental hazard and to introduce possible (bio)remediation techniques for sites that are contaminated with this class of compounds. This is the first detailed review on DPA and some derivatives summarizing their environmental relevance as it is published in the literature so far and this review will recommend conducting further research in the future.     

Variations in exposure to in-vehicle particle mass and number concentrations in different road environments

Road environments significantly affect in cabin concentration of particulate matter (PM). This study conducted measurements of in-vehicle and on-road concentrations of PM10, PM2.5, PM1, and particle number (PN) in size of 0.02–1 µm, under six ventilation settings in different urban road environments (tunnels, surface roads and elevated roads). Linear regression was then used to analyze the contributions of multiple predictor variables (including on-road concentrations, temperature, relative humidity, time of day, and ventilation settings) to measured variations. On-road measurements of PM2.5, PM1, and PN concentrations from the open surface roads were 5.5%, 3.7%, and 16% lower, respectively, than those measured in tunnels, but 7.6%, 7.1% and 24% higher, respectively, than those on elevated roads. The highest on-road PM10 concentration was observed on surface roads. The time series pattern of in-vehicle particle concentrations closely tracked the on-road concentrations outside of the car and exhibited a smoother profile. Irrespective of road environment, the average I/O ratio of particles was found to be the lowest when air conditioning was on with internal recirculation, the highest purification efficiency via ventilation was obtained by switching on external air recirculation and air conditioning. Statistical models showed that on-road concentration, temperature, and ventilation setting are common factors of significance that explained 58%-80%, 64%-97%, and 87%-98% of the variations in in-vehicle PM concentrations on surface roads, on elevated roads, and in tunnels, respectively.

Implications: Inside vehicles, both driver and passengers will be exposed to elevated particle concentrations. However, for in-vehicle particles, there has been no comprehensive comparative study of the three-dimensional traffic environment including tunnels surface roads and elevated roads. This study focuses on the analysis of the trends and main influencing factors of particle concentrations in different road environments. The results can provide suggestions for the driver's behavior, and provide data support for the environmental protection department to develop pollutant concentration limits within the vehicle.