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.     

Integration of a barcode reader with a commercial flow cytometer.

This report describes the application and installation of a barcode reader on a standard EPICS Elite flow cytometer. The barcode reader system eliminates keyboard entry of sample information on the cytometer. The system automates the transfer of sample information already present in our laboratory database to the cytometer at run time. The system uses a standard "off-the-shelf" bar code wand with a personal computer keyboard interface and requires no additional software at run time. No typing of sample information is required by the operator at any stage of normal sample operation at the cytometer. All operations are automatically coded into the cytometry software using the macro functions of the software. Tubes are inserted into the tube reader and sample information is transferred automatically into the cytometer. We have found that the system allows rapid and continuous operation of routine clinical and research samples. This automated data entry also reduces the possibility of data input errors.     

Regulation of magnesium but not calcium transport by phorbol ester

Phorbol esters in the presence of Ca2+ apparently mimic diacylglycerol in activating protein kinase C. Resulting phosphorylations alter multiple cellular processes including inhibition of the action of Ca2+-mobilizing agonists. In contrast to this inhibition of Ca2+ mobilization, addition of 4 beta-phorbol 12-myristate 13-acetate (PMA) to murine S49 lymphoma cells stimulated Mg2+ influx severalfold without any detectable alteration of Mg2+ efflux or of Ca2+ influx or efflux. Stimulation of Mg2+ influx did not require extracellular Ca2+, was half-maximal at 10 nM PMA, and was characterized by a marked increase in the Vmax of Mg2+ influx without change in the Ka for Mg2+. Stimulation of Mg2+ influx was not mimicked by 4 alpha-phorbol didecanoate, which does not activate protein kinase C and was not the result of Na+/H+ exchange activity. The effect of PMA on Mg2+ influx was inhibited by the beta-adrenergic agonist (-)-isoproterenol, which we have previously shown to inhibit Mg2+ influx by a non-cyclic AMP-dependent mechanism (Maguire, M. E., and Erdos, J. J. (1980) J. Biol. Chem. 255, 1030-1035). Forskolin, a direct activator of adenylate cyclase, also inhibited PMA stimulation of Mg2+ influx, suggesting the presence of both cyclic AMP-dependent and -independent influences on Mg2+ influx. We have also previously demonstrated that Mg2+ influx occurs solely into a small subcytoplasmic pool (Grubbs, R. D., Collins, S. D., and Maguire, M. E. (1984) J. Biol. Chem. 259, 12184-12192). PMA did not alter this compartmentation; rather, it almost doubled the content of this cytosolic Mg2+ pool. These data indicate that, in addition to phorbol ester modulation of intracellular Ca2+ mobilization, substantial changes in Mg2+ flux and content occur. They further demonstrate that Mg2+ influx is regulated by a variety of stimuli. It seems likely that such alterations in Mg2+ flux and content would have physiological consequences.     

Surfactants as Stimulants of Enzyme Production by Microorganisms

The addition of Tween 80 and sucrose monopalmitate, nonionic surfactants, to fungal cultures resulted in marked increases in yields of the enzymes cellulase, amylase, sucrase, beta-1 --> 3 glucanase, xylanase, purine nucleosidase, and benzoyl esterase. The action appears to be an effect of the surfactant on cell permeability.