Food quality affects the expression of antimicrobial peptide genes upon simulated parasite attack in the larvae of greater wax moth

Predator-prey interactions are an important evolutionary force affecting the immunity of the prey. Parasitoids and mites pierce the cuticle of their prey, which respond by activating their immune system against predatory attacks. Immunity is a costly function for the organism, as it often competes with other life-history traits for limited nutrients. We tested whether the expression of antimicrobial peptides (AMP) of the larvae of the greater wax moth Galleria mellonella (L.) (Lepidoptera: Pyralidae) changes as a consequence of insertion of a nylon monofilament, which acts like a synthetic parasite. The treatment was done for larvae grown on a high-quality vs. a low-quality diet. The expression of Gloverin and 6-tox were upregulated in response to the insertion of the nylon monofilament. The expression of 6-tox, Cecropin-D, and Gallerimycin were significantly higher in the low-quality diet' group than in the high-quality diet' group. As food quality seems to affect AMP gene expression in G. mellonella larvae, it should always be controlled for in studies on bacterial and fungal infections in G. mellonella

The excuse principle can maintain cooperation through forgivable defection in the Prisoner's Dilemma game

Reciprocal altruism describes a situation in which an organism acts in a manner that temporarily reduces its fitness while increasing another organism's fitness, but there is an ultimate fitness benefit based on an expectation that the other organism wil

Nocturnal loss of body reserves reveals high survival risk for subordinate great tits wintering at extremely low ambient temperatures

Winter acclimatization in birds is a complex of several strategies based on metabolic adjustment accompanied by long-term management of resources such as fattening. However, wintering birds often maintain fat reserves below their physiological capacity, suggesting a cost involved with excessive levels of reserves. We studied body reserves of roosting great tits in relation to their dominance status under two contrasting temperature regimes to see whether individuals are capable of optimizing their survival strategies under extreme environmental conditions. We predicted less pronounced loss of body mass and body condition and lower rates of overnight mortality in dominant great tits at both mild and extremely low ambient temperatures, when ambient temperature dropped down to −43 °C. The results showed that dominant great tits consistently maintained lower reserve levels than subordinates regardless of ambient temperature. However, dominants responded to the rising risk of starvation under low temperatures by increasing their body reserves, whereas subdominant birds decreased reserve levels in harsh conditions. Yet, their losses of body mass and body reserves were always lower than in subordinate birds. None of the dominant great tits were found dead, while five young females and one adult female were found dead in nest boxes during cold spells when ambient temperatures dropped down to −43 °C. The dead great tits lost up to 23.83 % of their evening body mass during cold nights while surviving individuals lost on average 12.78 % of their evening body mass. Our results show that fattening strategies of great tits reflect an adaptive role of winter fattening which is sensitive to changes in ambient temperatures and differs among individuals of different social ranks

Investment in a sexual signal results in reduced survival under extreme conditions in the male great tit (<i>Parus major)</i>

Here, we tested for an ecologically valid cost to secondary sexual trait expression in the male great tit (Parus major). We compared the breast stripe area of a sample of males who survived extremely low night time temperatures with a sample who did not survive. Breast stripe area was significantly smaller in surviving males, suggesting a real cost of signalling in terms of survival. The relationship between breast stripe area and survival was moderated by the effects of body condition: Males with larger breast stripes were in poorer condition and hence suffered increased mortality. Finally, we tested for relationships between breast stripe area and body condition, and tarsus asymmetry and immunological parameters (Brucella abortus antibody count, heterophil to lymphocyte ratio, eosinophil count, monocyte count) in surviving males. Only eosinophil count was related to breast stripe area. Our results suggest a survival cost to investment in sexual signals, such that males who invest somatic resources in social signalling risk increased mortality under extreme environmental conditions