Young Aphids Avoid Erroneous Dropping when Evading Mammalian Herbivores by Combining Input from Two Sensory Modalities

Mammalian herbivores may incidentally ingest plant-dwelling insects while foraging. Adult pea aphids (Acyrthosiphon pisum) avoid this danger by dropping off their host plant after sensing the herbivore's warm and humid breath and the vibrations it causes while feeding. Aphid nymphs may also drop (to escape insect enemies), but because of their slow movement, have a lower chance of finding a new plant. We compared dropping rates of first-instar nymphs with those of adults, after exposing pea aphids to different combinations of simulated mammalian breath and vibrations. We hypothesized that nymphs would compensate for the greater risk they face on the ground by interpreting more conservatively the mammalian herbivore cues they perceive. Most adults dropped in response to breath alone, but nymphs rarely did so. Breath stimulus accompanied by one concurrent vibrational stimulus, caused a minor rise in adult dropping rates. Adding a second vibration during breath had no additional effect on adults. The nymphs, however, relied on a combination of the two types of stimuli, with a threefold increase in dropping rates when the breath was accompanied by one vibration, and a further doubling of dropping rates when the second vibration was added. The age-specificity of the aphids' herbivore detection mechanism is probably an adaptation to the different cost of dropping for the different age groups. Relying on a combination of stimuli from two sensory modalities enables the vulnerable nymphs to avoid costly mistakes. Our findings emphasize the importance of the direct trophic effect of mammalian herbivory for plant-dwelling insects

Almost There: Transmission Routes of Bacterial Symbionts between Trophic Levels

Many intracellular microbial symbionts of arthropods are strictly vertically transmitted and manipulate their host's reproduction in ways that enhance their own transmission. Rare horizontal transmission events are nonetheless necessary for symbiont spread to novel host lineages. Horizontal transmission has been mostly inferred from phylogenetic studies but the mechanisms of spread are still largely a mystery. Here, we investigated transmission of two distantly related bacterial symbionts – Rickettsia and Hamiltonella – from their host, the sweet potato whitefly, Bemisia tabaci, to three species of whitefly parasitoids: Eretmocerus emiratus, Eretmocerus eremicus and Encarsia pergandiella. We also examined the potential for vertical transmission of these whitefly symbionts between parasitoid generations. Using florescence in situ hybridization (FISH) and transmission electron microscopy we found that Rickettsia invades Eretmocerus larvae during development in a Rickettsia-infected host, persists in adults and in females, reaches the ovaries. However, Rickettsia does not appear to penetrate the oocytes, but instead is localized in the follicular epithelial cells only. Consequently, Rickettsia is not vertically transmitted in Eretmocerus wasps, a result supported by diagnostic polymerase chain reaction (PCR). In contrast, Rickettsia proved to be merely transient in the digestive tract of Encarsia and was excreted with the meconia before wasp pupation. Adults of all three parasitoid species frequently acquired Rickettsia via contact with infected whiteflies, most likely by feeding on the host hemolymph (host feeding), but the rate of infection declined sharply within a few days of wasps being removed from infected whiteflies. In contrast with Rickettsia, Hamiltonella did not establish in any of the parasitoids tested, and none of the parasitoids acquired Hamiltonella by host feeding. This study demonstrates potential routes and barriers to horizontal transmission of symbionts across trophic levels. The possible mechanisms that lead to the differences in transmission of species of symbionts among species of hosts are discussed

Predictive role of hand-foot syndrome in patients receiving first-line capecitabine plus bevacizumab for HER2-negative metastatic breast cancer

BACKGROUND: Correlations between development of hand-foot syndrome (HFS) and efficacy in patients receiving capecitabine (CAP)-containing therapy are reported in the literature. We explored the relationship between HFS and efficacy in patients receiving CAP plus bevacizumab (BEV) in the TURANDOT randomised phase III trial. METHODS: Patients with HER2-negative locally recurrent/metastatic breast cancer (LR/mBC) who had received no prior chemotherapy for LR/mBC were randomised to BEV plus paclitaxel or BEV-CAP until disease progression or unacceptable toxicity. This analysis included patients randomised to BEV-CAP who received 1 CAP dose. Potential associations between HFS and both overall survival (OS; primary end point) and progression-free survival (PFS; secondary end point) were explored using Cox proportional hazards analyses with HFS as a time-dependent covariate (to avoid overestimating the effect of HFS on efficacy). Landmark analyses were also performed. RESULTS: Among 277 patients treated with BEV-CAP, 154 (56%) developed HFS. In multivariate analyses, risk of progression or death was reduced by 44% after the occurrence of HFS; risk of death was reduced by 56%. The magnitude of effect on OS increased with increasing HFS grade. In patients developing HFS within the first 3 months, median PFS from the 3-month landmark was 10.0 months vs 6.2 months in patients without HFS. Two-year OS rates were 63% and 44%, respectively. CONCLUSIONS: This exploratory analysis indicates that HFS occurrence is a strong predictor of prolonged PFS and OS in patients receiving BEV-CAP for LR/mBC. Early appearance of HFS may help motivate patients to continue therapy.British Journal of Cancer advance online publication, 10 December 2015; doi:10.1038/bjc.2015.419 www.bjcancer.com