Social wasps desert the colony and aggregate outside if parasitized: parasite manipulation?

Infection of the paper wasp, Polistes dominulus (Christ), bythe strepsipteran parasite Xenos vesparum Rossi results in adramatic behavioral change, which culminates in colony desertionand the formation of extranidal aggregations, in which up to98% of occupants are parasitized females. Aggregations formedon prominent vegetation, traditional lek-sites of Polistes males,and on buildings, which were later adopted as hibernating sitesby future queens. First discovered by W.D. Hamilton, these aberrantaggregations are an overlooked phenomenon of the behavioralecology of this intensively studied wasp. For 3 months in thesummer of 2000, during the peak of colony development, we sampled91 extranidal aggregations from seven areas, numbering 1322wasps. These wasps were parasitized by both sexes of X. vesparum,but males were more frequent from July until mid-August, duringthe mating season of the parasite. Aggregations were presentfor days at the same sites (in one case a leaf was occupiedfor 36 consecutive days) and were characterized by extreme inactivity.After artificial infection, parasitized "workers" deserted thenest 1 week after emergence from their cell and before the extrusionof the parasite through the host cuticle. Infected individualsdid not work, were more inactive, and did not receive more aggressionthan did controls. We suggest that early nest desertion andsubsequent aggregations by parasitized nominal workers and "futurequeens" is adaptive manipulation of host behavior by the parasiteto promote the completion of its life cycle.     

Rank order of success favors longer duration of imidazole-based therapy for Helicobacter pylori in duodenal ulcer disease: a randomized pilot study

Background. Studies on eradication therapy in developing countries have shown a success rate of 70–85%, which is suboptimal. Duration of therapy may be an important factor dictating eradication success in such regions. Aim. The study was undertaken to evaluate the effect of increasing the treatment period on eradication of Helicobacter pylori in duodenal ulcer disease. Methods. A randomized trial was carried out in which 64 consecutive H. pylori‐infected patients with duodenal ulcer disease were enrolled. The patients were randomized to one of the three trial arms. Therapy consisted of lansoprazole 30 mg twice a day (b.i.d.), amoxycillin 1 g b.i.d. and tinidazole 500 mg b.i.d. The treatment period was 1 week in group I, 2 weeks in group II and 3 weeks in group III. At inclusion, patients underwent endoscopy and the presence of H. pylori was documented by a positive urease test and C14 urea breath test. Four weeks after completion of eradication therapy, the patients were subjected to repeat endoscopy to assess ulcer healing and tests for H. pylori infection. Results. Sixty‐four patients (55 male and nine female; mean age 35.5 years) were enrolled in each group. The H. pylori eradication rate for group I (1 week of therapy) was 47.6%, that for group II (2 weeks of therapy) was 80%, and that for group III (3 weeks of therapy) was 91.3% (p = .003). The ulcer healing rates were 71.4, 80 and 95.6% in groups I, II and III, respectively (p = .09). Conclusion. The 3‐week regimen significantly improved the eradication rate as compared with the 1‐week regime. Increasing the duration of therapy significantly improved the chances of eradication of H. pylori in duodenal ulcer disease.     

Reducing the computational complexity of protein folding via fragment folding and assembly

Understanding, and ultimately predicting, how a 1-D protein chain reaches its native 3-D fold has been one of the most challenging problems during the last few decades. Data increasingly indicate that protein folding is a hierarchical process. Hence, the question arises as to whether we can use the hierarchical concept to reduce the practically intractable computational times. For such a scheme to work, the first step is to cut the protein sequence into fragments that form local minima on the polypeptide chain. The conformations of such fragments in solution are likely to be similar to those when the fragments are embedded in the native fold, although alternate conformations may be favored during the mutual stabilization in the combinatorial assembly process. Two elements are needed for such cutting: (1) a library of (clustered) fragments derived from known protein structures and (2) an assignment algorithm that selects optimal combinations to "cover" the protein sequence. The next two steps in hierarchical folding schemes, not addressed here, are the combinatorial assembly of the fragments and finally, optimization of the obtained conformations. Here, we address the first step in a hierarchical protein-folding scheme. The input is a target protein sequence and a library of fragments created by clustering building blocks that were generated by cutting all protein structures. The output is a set of cutout fragments. We briefly outline a graph theoretic algorithm that automatically assigns building blocks to the target sequence, and we describe a sample of the results we have obtained.     

Determinants of sperm transfer in the scorpionfly Panorpa cognate: male variation, female condition and copulation duration

Recent studies suggest that sperm production and transfer may have significant costs to males. Male sperm investment into a current copulation may therefore influence resources available for future matings, which selects for male strategic mating investment. In addition, females may also benefit from actively or passively altering the number of sperm transferred by males. In the scorpionfly Panorpa cognata, the number of sperm transferred during copulation depended on copulation duration and males in good condition (residual weight) copulated longer and also transferred more sperm. Moreover, sperm transferred and stored per unit time was higher in copulations with females in good condition than in copulations with females in poor condition. Males varied greatly and consistently in their sperm transfer rate, indicative of costs associated with this trait. The duration of the pairing prelude also varied between males and correlated negatively with the male's sperm transfer rate, but no other male character correlated significantly with male sperm transfer rate. The results are consistent with strategic mating effort but sperm transfer could also be facilitated by the physical size of females and/or females in good condition may be more cooperative during sperm transfer.     

Nest relocation in the golden spiny ant, <Emphasis Type="Italic">Polyrhachis ammon:</Emphasis> environmental cues and temporal castes

Summary Despite its apparent costs, nest relocation is a common phenomenon among ants. Polyrhachis ammon, a common ant in open habitats of eastern Australia, exhibits a high rate of colony emigration to new nest sites. We conducted a field survey and shading experiments in different seasons and years to determine which factors affect colony emigration in this species. We also compared morphological features characterising workers involved in adult transport to determine if workers performing different tasks belong-ed to discernible temporal castes. Nests that were abandon-ed after four weeks were smaller, although distance from a food source and low-level disturbance did not alter re-location rates. The effects of shading and nest temperature on nest survival varied between seasons, as did rates of nest relocation. Transporter workers could not be distinguished from foragers, but had greater mandibular wear and smaller dry mass than transportees. Our results suggest that cues promoting nest relocation in P. ammon may be the result of a combination of factors with varying temporal importance.     

Use of terrestrial chemical trails for nest orientation in an open nesting wasp, <Emphasis Type="Italic">Dolichovespula saxonica</Emphasis> F.

Summary The long-cheeked wasp Dolichovespula saxonica typically constructs exposed nests which can be reached by flying. Usually foragers do not walk on substrates in the close vicinity of the nests as cavity breeding wasps do (Steinmetz et al., 2002). Unexpectedly, when forced to walk outside the nest instead of flying in an artificial tunnel system, D. saxonica foragers lay a terrestrial trail and use it for orientation in the nest area in our experiments. 41% of the foragers followed the trail in a direction they were not accustomed to. We suggest that the foragers have employed the same orientation cues normally used for orientation in the close vicinity of the nest when approaching a free-hanging nest by flying, for example nest odour. Nest odour substances may have been transferred to the substrate as a trail as a consequence of foragers walking through the tunnels.Received 23 August 2002; revised 27 January 2003; accepted 30 April 2003.     

Factors involved in the post-copulatory neural inhibition of pheromone production in Choristoneura fumiferana and C. rosaceana females

Normal mating lasts approximately 3 h in Choristoneura fumiferana and C. rosaceana. Data generated from interrupted matings showed that the act of mating did not suppress pheromone production (pheromonostasis) in either species although, in C. rosaceana, pheromone titre declined slightly the night following mating. In both species the migration of sperm to the spermatheca (SP) occurred several hours after mating, and coincided with a significant and permanent depression in pheromone titre, as well as egg fertilisation and oviposition. However, disrupting matings within 2 h of the onset resulted in oviposition patterns similar to virgins in both species, with mostly infertile eggs being laid by C. fumiferana females while oviposition was totally inhibited in C. rosaceana. The transection of the ventral nerve cord (VNC) 1 h post-mating did not result in the depression of pheromone titres the following night in either species but if the VNC was transected 3 h post-mating, pheromonostasis was observed. While 25% of C. fumiferana females had sperm in their SP 2 h after mating, it took at least 4 h in C. rosaceana. This suggests that while the physical presence of sperm in the SP may play some role in the termination of pheromone production in C. fumiferana, other factors must trigger the neural signal that elicits pheromonostasis in both species. A better understanding of the temporal dynamics of both apyrene and eupyrene sperm within the different parts of the female reproductive system might clarify these interspecific differences.     

Diving behaviour, dive cycles and aerobic dive limit in the platypus Ornithorhynchus anatinus

We investigated the diving behaviour, the time allocation of the dive cycle and the behavioural aerobic dive limit (ADL) of platypuses (Ornithorhynchus anatinus) living at a sub-alpine Tasmanian lake. Individual platypuses were equipped with combined data logger-transmitter packages measuring dive depth. Mean dive duration was 31.3 s with 72% of all dives lasting between 18 and 40 s. Mean surface duration was 10.1 s. Mean dive depth was 1.28 m with a maximum of 8.77 m. Platypuses performed up to 1600 dives per foraging trip with a mean of 75 dives per hour. ADL was estimated by consideration of post-dive surface intervals vs. dive durations. Only 15% of all dives were found to exceed the estimated ADL of 40 s, indicating mainly aerobic diving in the species. Foraging platypuses followed a model of optimised recovery time, the optimal breathing theory. Total bottom duration or total foraging duration per day is proposed as a useful indicator of foraging efficiency and hence habitat quality in the species.     

Organic matter processing by chironomid larvae (Diptera: Chironomidae)

In laboratory experiments, we used fluorescent dye markers to investigate processing of organic matter by larvae of Psectrocladius limbatellus (Holm.) (Diptera: Chironomidae). 59% of the organic matter used was incorporated into tubes, 39% was present in faecal pellets (both after 24 h), and 2% was found in the larval gut at the end of experiments. Ingested matter passed through the gut rapidly, resulting in the gut being emptied more than 20 times each day. Further 24-h experiments using dye-marked faecal pellets showed that 6% of pellets produced were re-ingested and 12% were incorporated into tubes. There was no preference for conditioned faecal pellets as food over those that had recently been egested and tubes also provided a food reserve on which larvae feed. Chironomid larvae recycle organic matter resulting in its mineralization and their ‘engineering’ has a dramatic effect on the substratum. This revised version was published online in July 2006 with corrections to the Cover Date.     

金毛弓背蚁的巢穴结构、头宽频数分布及活动节律

对金毛弓背蚁Camponotus tonkinus Santschi的巢穴结构、工蚁头宽频数特征及巢外活动节律作了系统的观察和分析。发现金毛弓背蚁地下巢穴极为复杂,有纵横交错的通道系统和众多的小室,蚁后室位于巢穴底部,工蚁的头宽为连续性,范围在1.05-3.85mm,频数分布为不对称的单峰,头宽在1.4～2.Omm的个体最多,占总数的72.7%,晴朗天气里工蚁出入巢活动在上午和下午各有一个高峰,中午随温度升高金毛弓背蚁外出活动进入低谷.