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.     

Tracking wind‐dispersed seeds using 15N‐isotope enrichment

Seed dispersal influences a wide range of ecological processes. However, measuring dispersal patterns, particularly long‐distance dispersal, has been a difficult task. Marking bird‐dispersed seeds with stable ¹⁵N isotopes has been shown to be a user‐friendly method to trace seed dispersal. In this study, we determined whether ¹⁵N urea solution could be used to enrich seeds of two common wind‐dispersed plants, Eupatorium glaucescens (Asteraceae) and Sericocarpus tortifolius (Asteraceae). We further tested if the water type (distilled versus tap) in ¹⁵N urea solutions influences the level and variability of enrichment of plant seeds, and if increasing spraying frequency per se increases enrichment. Because droughts may lower seed set or kill plants, we wanted to investigate if the additional use of an externally applied anti‐transpirant affects the intake of externally applied ¹⁵N into seeds. The results demonstrate that ¹⁵N enrichment of seeds can facilitate dispersal experiments with wind‐dispersed plants. The use of distilled water in ¹⁵N urea solutions did not increase ¹⁵N enrichment compared to tap water. Further, enrichment was more efficient at lower spray frequencies. Both the use of tap water and low frequencies could lower time, effort and project costs. The results suggest that species can be protected from drought using an anti‐transpirant without decreasing the incorporation of ¹⁵N into seeds.     

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.     

The effect of tetrodotoxin on the sodium gating current in the squid giant axon.

The effect of tetrodotoxin (TTX) on the sodium gating current in the squid giant axon was examined by recording the current that flowed at the pulse potential at which the ionic current fell to zero, first in the absence and then in the presence of TTX. The addition of 1 microM TTX to the bathing solution had no consistent effect on the size of the initial peak of the gating current, but resulted in small changes in the timecourse of its subsequent relaxation which were mainly caused by a reduction of about one quarter in the component that has a delayed onset and may possibly arise from changes in the state of ionization of groups in the channel wall when the lumen fills with water. Our findings suggest that the binding of TTX at the outer face of the sodium channel does not interfere with the mechanisms of activation and inactivation by the voltage sensors, but has an allosteric effect on the access of internal cations to the inside of the channel.     

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.     

The effects of decreased growth temperature on the cystine content of cystinotic fibroblasts

Cystinotic fibroblasts transferred from 37 degrees C to 28 degrees C accumulated additional cystine over the period from 4 to 7 days of incubation at 28 degrees C, after which the additional cystine was lost; warming (to 37 degrees C) of cells with elevated cystine stores led to rapid cystine loss. These results, taken together with previously published data showing cystine release from cystinotic fibroblasts incubated at above-normal temperature, are interpreted as indicating the presence in the cystinotic fibroblast lysosome membrane of a cystine-porter whose efficacy is increased by an increase in membrane fluidity. This porter may be the residual activity of the cystine porter that is known to be deficient in cystinosis, or it may be a second as yet unrecognized porter. It is further proposed that this porter is responsible for the presumed efflux of cystine from cystinotic lysosomes.     

The complete nucleotide sequence of the potexvirus white clover mosaic virus.

The complete nucleotide sequence (5845 nucleotides) of the genomic RNA of the potexvirus white clover mosaic virus (WC1MV) has been determined from a set of overlapping cDNA clones. Forty of the most 5'-terminal nucleotides of WC1MV showed homology to the 5' sequences of other potexviruses. The genome contained five open reading frames which coded for proteins of Mr 147, 417, Mr 26,356, Mr 12,989, Mr 7,219 and Mr 20,684 (the coat protein). The Mr 147,417 protein had domains of amino acid sequence homology with putative polymerases of other RNA viruses. The Mr 26,356 and Mr 12,989 proteins had homology with proteins of the hordeivirus barley stripe mosaic virus RNA beta and the furovirus beet necrotic yellow vein virus (BNYVV) RNA-2. A portion of the Mr 26,356 protein was also conserved in the cylindrical inclusion proteins of two potyviruses. The Mr 7,219 protein had homology with the 25K putative fungal transmission factor of BNYVV RNA-3.