Oviposition preferences and antennal size in carrion flies

Carrion-feeding flies use odours emanating from the decomposing corpse as cues for oviposition and are described as generalists because the larvae feed on the corpses of diverse species. Whereas several features of the corpse may influence the oviposition choices of these flies, it is not known whether there is a preference for a particular species of corpse. We provided carrion flies with ovipositional (and feeding) choices in a field experiment, in which various odour sources were presented simultaneously. We found novel evidence of broadly consistent choices of carrion by flies from four families. Traps baited with decaying fish flesh captured the greatest number of individuals, whereas traps baited with decaying pig liver typically attracted the least. We also asked whether individuals captured in the various baits vary in antennal size, perhaps reflecting different capacities for odour detection. There was a trend for individuals of Lucilia sericata Meigen (Diptera: Calliphoridae) and the platystomatid collected from the traps baited with pig liver to have significantly larger antennae, whereas individuals of Muscina stabulans (Fallen) (Diptera: Muscidae) captured in traps baited with marine fish flesh had relatively longer antennae for their body size. Our data reveal a more nuanced pattern of oviposition behaviour in these generalist carrion flies, which may reflect differences in their preference of carrion with different nutrients, and in their capacity to detect particular odours.     

Antagonistic coevolution between hosts and sexually transmitted infections

Sexually transmitted infections (STIs) are predicted to play an important role in the evolution of host mating strategies, and vice versa, yet our understanding of host-STI coevolution is limited. Previous theoretical work has shown mate choice can evolve to prevent runaway STI virulence evolution in chronic, sterilizing infections. Here, I generalize this theory to examine how a broader range of life-history traits influence coevolution; specifically, how host preferences for healthy mates and STI virulence coevolve when infections are acute and can cause mortality or sterility, and hosts do not form long-term sexual partnerships. I show that mate choice reduces both mortality and sterility virulence, with qualitatively different outcomes depending on the mode of virulence, costs associated with mate choice, recovery rates, and host lifespan. For example, fluctuating selection—a key finding in previous work—is most likely when hosts have moderate lifespans, STIs cause sterility and long infections, and costs of mate choice are low. The results reveal new insights into the coevolution of mate choice and STI virulence as different life-history traits vary, providing increased support for parasite-mediated sexual selection as a potential driver of host mate choice, and mate choice as a constraint on the evolution of virulence.     

Artificial selection on sexual aggression: Correlated traits and possible trade-offs

Forced copulation is an extreme form of sexual aggression that can affect the evolution of sex-specific anatomy, morphology, and behavior. To characterize mechanistic and evolutionary aspects of forced copulation, we artificially selected male fruit flies based on their ability to succeed in the naturally prevalent behavior of forced matings with newly eclosed (teneral) females. The low and high forced copulation lineages showed rapid divergence, with the high lineages ultimately showing twice the rates of forced copulation as the low lineages. While males from the high lineages spent more time aggressively pursuing and mounting teneral females, their behavior toward non-teneral and heterospecific females was similar to that of males from the low lineages. Males from the low and high lineages also showed similar levels of male-male aggression. This suggests little or no genetic correlations between sexual aggression and non-aggressive pursuit of females, and between male aggression toward females and males. Surprisingly however, males from the high lineages had twice as high mating success than males from the low lineages when allowed to compete for consensual mating with mature females. In further experiments, we found no evidence for trade-offs associated with high forced mating rates: males from the high lineages did not have lower longevity than males from the low lineages when housed with females, and four generations of relaxed selection did not lead to convergence in forced mating rates. Our data indicate complex interactions among forced copulation success and consensual mating behavior, which we hope to clarify in future genomic work.     

Do dung beetle larvae need microbial symbionts from their parents to feed on dung?

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Maternal obesity disrupts circadian rhythms of clock and metabolic genes in the offspring heart and liver

Early life nutritional adversity is tightly associated with the development of long-term metabolic disorders. Particularly, maternal obesity and high-fat diets cause high risk of obesity in the offspring. Those offspring are also prone to develop hyperinsulinemia, hepatic steatosis and cardiovascular diseases. However, the precise underlying mechanisms leading to these metabolic dysregulation in the offspring remain unclear. On the other hand, disruptions of diurnal circadian rhythms are known to impair metabolic homeostasis in various tissues including the heart and liver. Therefore, we investigated that whether maternal obesity perturbs the circadian expression rhythms of clock, metabolic and inflammatory genes in offspring heart and liver by using RT-qPCR and Western blotting analysis. Offspring from lean and obese dams were examined on postnatal day 17 and 35, when pups were nursed by their mothers or took food independently. On P17, genes examined in the heart either showed anti-phase oscillations (Cpt1b, Pparα, Per2) or had greater oscillation amplitudes (Bmal1, Tnf-α, Il-6). Such phase abnormalities of these genes were improved on P35, while defects in amplitudes still existed. In the liver of 17-day-old pups exposed to maternal obesity, the oscillation amplitudes of most rhythmic genes examined (except Bmal1) were strongly suppressed. On P35, the oscillations of circadian and inflammatory genes became more robust in the liver, while metabolic genes were still kept non-rhythmic. Maternal obesity also had a profound influence in the protein expression levels of examined genes in offspring heart and liver. Our observations indicate that the circadian clock undergoes nutritional programing, which may contribute to the alternations in energy metabolism associated with the development of metabolic disorders in early life and adulthood.     

Darker female pigeons transmit more specific antibodies to their eggs than do paler ones

Melanin‐based coloration is widespread among vertebrates, yet the adaptive significance of such pigments remains elusive, particularly with regard to the link between melanin and immune‐mediated maternal effects. The aim of this study was to investigate whether melanin‐based coloration could signal the ability of mothers to mount a humoral response and to transfer maternal antibodies (Ab) to their young. We injected differently coloured (pale and dark) female feral pigeons (Columba livia) with Chlamydiae (a natural antigen) and Keyhole Limpet Haemocyanin (KLH, an artificial antigen), and found no significant difference in humoral response between differently coloured females. However, darker females transferred more Ab against Chlamydiae into their eggs than paler ones, despite similar circulating levels of Ab. In addition to this, melanin‐based coloration showed a high heritability value. This suggests that a genetically based coloured trait might be linked to the ability of females to transfer specific Ab against Chlamydiae (but not against KLH) to their offspring, independent of their ability to produce Ab. This suggests that transmission of maternal Ab is antigen dependent, and that melanin‐based coloration might signal female ability to transmit specific Ab against natural pathogens. © 2013 The Linnean Society of London     

Insect diapause of very variable duration: the case of the palm nut bruchid Pachymerus nucleorum (Coleoptera: Chrysomelidae)

Data are provided here showing that larval diapause in the tropical palm nut bruchid Pachymerus nucleorum (Fabricius) can extend up to a maximum of about five years, although for most individuals the duration ranges from 15 to 48 months. The data were obtained for insects originating from one source only that were held under one set of temperature and photoperiod conditions only so the wide variation in duration is attributed to maternal control. Staggering the adult emergence times of a parent’s progeny can be regarded as an evolutionary strategy that increases the chance that some at least encounter favourable biotic or abiotic conditions. It is believed that extended diapause may be quite widespread amongst insects, including those of temperate climates.     

The neonate nutrition hypothesis: early feeding affects the body stoichiometry of Daphnia offspring

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