Behavioural modification of a social spider by a parasitoid wasp

1. Manipulation of host behaviour by parasitoids has long captured the imagination of ecologists. Parasitoid wasps in the Polysphincta group of genera develop as external parasitoids of spiders. 2. In the present study, the previously undescribed interaction between a Zatypota sp. wasp (Ichneumonidae) and a social spider Anelosimus eximius (Theridiidae) is described. The larva of this Zatypota wasp is found to induce its host to disperse from their communal web and build an entirely enclosed web consisting of densely spun silk. 3. The wasp is observed to target primarily immature A. eximius individuals, with 37.5–44% of nests in a given area being parasitised. Of those nests, approximately 1.3–2.0% of individuals are hosts to the parasitoid larvae. Larger spider colonies had a significantly higher probability of harbouring parasitoids. 4. This interaction results in unusual behaviours for A. eximius induced by the parasitoid: (i) leaving the protection of the social nest and (ii) building a unique, altered web that it would not otherwise build. It is suggested that the wasp may be tapping into ancestral dispersal behaviours in its host and that a social species provides this wasp an evolutionary advantage by allowing a stable host source.     

A Bird’s Eye View of Discard Reforms: Bird-Borne Cameras Reveal Seabird/Fishery Interactions

Commercial capture fisheries produce huge quantities of offal, as well as undersized and unwanted catch in the form of discards. Declines in global catches and legislation to ban discarding will significantly reduce discards, but this subsidy supports a large scavenger community. Understanding the potential impact of declining discards for scavengers should feature in an eco-system based approach to fisheries management, but requires greater knowledge of scavenger/fishery interactions. Here we use bird-borne cameras, in tandem with GPS loggers, to provide a unique view of seabird/fishery interactions. 20,643 digital images (one min⁻¹) from ten bird-borne cameras deployed on central place northern gannets Morus bassanus revealed that all birds photographed fishing vessels. These were large (>15 m) boats, with no small-scale vessels. Virtually all vessels were trawlers, and gannets were almost always accompanied by other scavenging birds. All individuals exhibited an Area-Restricted Search (ARS) during foraging, but only 42% of ARS were associated with fishing vessels, indicating much ‘natural’ foraging. The proportion of ARS behaviours associated with fishing boats were higher for males (81%) than females (30%), although the reasons for this are currently unclear. Our study illustrates that fisheries form a very important component of the prey-landscape for foraging gannets and that a discard ban, such as that proposed under reforms of the EU Common Fisheries Policy, may have a significant impact on gannet behaviour, particularly males. However, a continued reliance on ‘natural’ foraging suggests the ability to switch away from scavenging, but only if there is sufficient food to meet their needs in the absence of a discard subsidy.     

Do pollen beetles need pollen? The effect of pollen on oviposition,survival, and development of a flower‐feeding herbivore

Abstract.  1. Pollen is considered to be an important dietary component for many species of flower-feeding herbivores. Its influence on oviposition site selection by the pollen beetle Meligethes aeneus , and on the development of its larvae was investigated.
2. The effects of pollen presence and absence on adult, egg, and larval incidence in the field, and on larval development in the laboratory were compared through the use of Synergy, a composite hybrid oilseed rape Brassica napus variety comprising male-fertile (with pollen) and male-sterile (without pollen) plants.
3. In the field, adult females were more abundant on male-fertile plants during flowering, and a greater proportion of male-fertile than male-sterile buds were accepted for oviposition. These data indicate a possible role of pollen in oviposition site selection by female pollen beetles.
4. The numbers of first instar larvae on the two plant lines did not differ; however, more second instars were found on male-fertile than on male-sterile flowers. This suggests a greater larval survival on male-fertile plants, possibly due to the more readily available food resources and better nutrition afforded by the presence of pollen.
5. Laboratory experiments confirmed that a diet which included pollen improved survival to adulthood and resulted in heavier pupae and adults; however, pollen was not obligatory for larval survival and development.
6. The pollen beetle, previously thought to be an obligate pollen feeder, is therefore more generalist in its requirements for development. These findings may relate to the nutritional and behavioural ecology of other flower-feeding herbivores.     

Olaquindox resistance in the coliform flora of pigs and their environment: an ecological study

Faecal samples were taken weekly from a chosen pen on each of four commercial pig farms, two of which used olaquindox as a feed additive. Coliform bacteria were isolated from the samples and the incidence and level of resistance to olaquindox and to four therapeutic antibiotics determined. The coliforms isolated were biotyped to follow the emergence of drug-resistant sub-populations. The results showed that the coliform flora was complex and that a turnover of biotypes was associated with changes in the occupancy of the pen and, possibly, diet. This turnover led to large fluctuations in both incidence and level of resistance to olaquindox and the antibiotics. Olaquindox resistance was not specifically linked with resistance to any therapeutic antibiotic, and the possible origin of olaquindox-resistant strains is discussed in relation to the biotypes.     

Sensitivity to X-irradiation of peripheral blood lymphocytes from ageing donors

The proliferation of human blood lymphocytes from ageing donors, responding to concanavalin A, showed greater sensitivity to inhibition by X-rays than similar cells from younger donors. This increased sensitivity was associated with deficiency in repair of X-ray-induced damage to nuclear material, as measured by density in sucrose gradients, and with increased incidence of chromosomal damage following exposure of freshly isolated lymphocytes. There was also an increased frequency of spontaneous chromosomal aberrations in ageing subjects whose lymphocytes were deficient in repair of DNA damage.     

Molecular homology and incompatibility relationships between F and IncH1 plasmids

IncH1 plasmids and the F plasmid of Escherichia coli display one-way compatibility. An entering IncH1 plasmid is incompatible with a resident F plasmid, but is compatible when it is the resident plasmid. There is little molecular homology between IncH1 plasmids and the F plasmid. A single 5 MDal EcoRI restriction enzyme fragment from digests of several IncH1 plasmids hybridizes with probes constructed from the primary replication region of F. Homology can be demonstrated only with the gene for the essential replication protein of F (gene E), but the expression of incompatibility behaviour appears to be associated with the presence of the secondary replicon of the F plasmid. Thus R27 and F are compatible under growth conditions allowing replication and maintenance of F by the secondary replicon. However, a mutant F plasmid which lacks the secondary replicon of F is incompatible with R27 in both directions, irrespective of the growth conditions used.     

Genetic basis for opine secretion from crown gall tumour cells

Summary Plant cells neoplastically transformed by insertion of T-DNA from Ti plasmids of agrobacteria produce and secrete opines. Secretion of two of these opines (octopine and nopaline) is shown to require the expression of a single gene, which we designate ons.Dedicated to Professor Georg Melchers to celebrate his 50-year association with the journal     

The ecology of Escherichia coli in market calves fed a milk-substitute diet

Dynamic changes in the Escherichia coli population in the calf gut were studied over 21 days in a group of 18 intensively-reared market calves. Isolates were identified by O-serogrouping, biotyping and resistogram patterns. Seventy O-serogroups were identified among nearly 3000 E. coli isolates examined and these were subdivided into 416 strains by means of their biotype and resistogram. Seventy-five per cent of these strains were detected only once or twice, which points to the continual replacement of the E. coli flora with strains that showed low persistence in the gut. The rise in the frequency of antibiotic resistance observed during the study was not due to a change in the proportion of resistant to sensitive strains in the gut flora. It was a consequence of the displacement of the original flora by multiply-resistant strains, which presumably originated from the calves' environment.