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.     

Haematobia irritans parasitism of F1 yak × beef cattle (Bos grunniens × Bos taurus) hybrids

The horn fly Haematobia irritans (Diptera: Muscidae) is a blood obligate ectoparasite of bovids that causes annual losses to the U.S. beef cattle industry of over US$1.75 billion. Climate warming, the anthropogenic dispersion of bovids and the cross‐breeding of beef cattle with other bovid species may facilitate novel horn fly–host interactions. In particular, hybridizing yaks [Bos grunniens (Artiodactyla: Bovidae)] with beef cows (Bos taurus) for heterosis and carcass improvements may increase the exposure of yak × beef hybrids to horn flies. The present paper reports on the collection of digital images of commingled beef heifers (n = 12) and F1 yak × beef hybrid bovids (heifers, n = 7; steers, n = 5) near Laramie, Wyoming (～ 2200 m a.s.l.) in 2018. The total numbers of horn flies on beef heifers and F1 yak × beef heifers [mean ± standard error (SE): 88 ± 13 and 70 ± 17, respectively] did not differ significantly; however, F1 yak × beef steers had greater total horn fly abundance (mean ± SE: 159 ± 39) than female bovids. The present report of this experiment is the first such report in the literature and suggests that F1 yak × beef bovids are as susceptible as cattle to horn fly parasitism. Therefore, similar monitoring and treatment practices should be adopted by veterinarians, entomologists and producers.     

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.     

In vitro regulation of the pathogenic autoantibody response of New Zealand black mice. I. Loss with age of suppressive activity in T cell populations

An investigation of the regulation of specific anti-self responses was initiated with the development of an in vitro system in which spleen cells from NZB mice were stimulated by syngeneic mouse erythrocytes (MRBC) to produce MRBC-specific autoantibody-secreting cells. The response was measured by a modification of the focus-forming cell (FFC) assay, which enumerates cells secreting IgG, which specifically bind MRBC. Spleen cells from 9- to 12-mo-old NZB mice developed MRBC-specific FFC after 3 to 5 days in culture with MRBC. Few FFC were detected in the absence of MRBC in culture. Spleen cells from young (1- to 4-mo-old) NZB mice developed few if any FFC. Spleen cell populations containing T cells from young NZB mice suppressed this anti-MRBC response, whereas B cell populations from these young mice did not. In contrast, spleen cells, including T cell-enriched populations from old, Coombs'-positive mice were not capable under the same conditions of producing equivalent suppression of this in vitro autoimmune response. These data suggest that a population of suppressor T cells that may control the autoimmune anti-MRBC response in young NZB mice is lost, or else its activity is masked in old NZB mice that are actively producing anti-MRBC antibody.     

Estimating denitrification rates in estuarine sediments: A comparison of stoichiometric and acetylene based methods

We compared denitrification rates obtained using an adaptation of the acetylene block technique to rates estimated from benthic flux nutrient stoichiometry in the subtidal sediments of Tomales Bay, California (USA). By amending whole cores with acetylene and saturating nitrate concentrations, we obtained potential denitrification rates, which ranged between 4 and 30 mmol N m^–2 d^–1. We determined the apparent Michaelis constant (K_app) and the maximum potential rate (V_mp) of the denitrifying community and used these constants in a rectangular hyperbola to estimatein situ denitrification rates. Both the K_app and V_mp of the denitrifying community exhibited significant variation over both depth in the sediment column and time of sampling.Estimates ofin situ denitrification obtained using our kinetic-fix adaptation of the acetylene block ranged between 1.8 (March) and 9 (Sept.) mmol N m^–1 d^–1. Denitrification rates obtained using benthic flux stoichiometry ranged between 0.7 and 4.1 mmol N m^–2 d^–1. Average denitrification rates obtained using the kinetic-fix acetylene block approach exceeded those obtained from net benthic flux stoichiometry; however, these differences were not significant. We conclude that our kinetic-fix adaptation of the acetylene block technique provides realistic estimates of denitrification in sediments, even when pore water nitrate concentrations are low and nitrification and denitrification are closely coupled.     

Blown away? Wind speed and foraging success in an acoustic predator

Mammal Research - Foraging animals must contend with fluctuating environmental variables that affect foraging success, including conditions like wind noise, which could diminish the usefulness of...     

Pattern-based clustering of daily weigh-in trajectories using dynamic time warping

“Smart”-scales are a new tool for frequent monitoring of weight change as well as weigh-in behavior. These scales give researchers the opportunity to discover patterns in the frequency that individuals weigh themselves over time, and how these patterns are associated with overall weight loss. Our motivating data come from an 18-month behavioral weight loss study of 55 adults classified as overweight or obese who were instructed to weigh themselves daily. Adherence to daily weigh-in routines produces a binary times series for each subject, indicating whether a participant weighed in on a given day. To characterize weigh-in by time-invariant patterns rather than overall adherence, we propose using hierarchical clustering with dynamic time warping (DTW). We perform an extensive simulation study to evaluate the performance of DTW compared to Euclidean and Jaccard distances to recover underlying patterns in adherence time series. In addition, we compare cluster performance using cluster validation indices (CVIs) under the single, average, complete, and Ward linkages and evaluate how internal and external CVIs compare for clustering binary time series. We apply conclusions from the simulation to cluster our real data and summarize observed weigh-in patterns. Our analysis finds that the adherence trajectory pattern is significantly associated with weight loss.