Low Mate Encounter Rate Increases Male Risk Taking in a Sexually Cannibalistic Praying Mantis

Male praying mantises are forced into the ultimate trade-off of mating versus complete loss of future reproduction if they fall prey to a female. The balance of this trade-off will depend both on (1) the level of predatory risk imposed by females and (2) the frequency of mating opportunities for males. We report the results of a set of experiments that examine the effects of these two variables on male risk-taking behavior and the frequency of sexual cannibalism in the praying mantis Tenodera sinensis. We experimentally altered the rate at which males encountered females and measured male approach and courtship behavior under conditions of high and low risk of being attacked by females. We show that male risk taking depends on prior access to females. Males with restricted access to females showed greater risk-taking behavior. When males were given daily female encounters, they responded to greater female-imposed risk by slowing their rate of approach and remained a greater distance from a potential mate. In contrast, males without recent access to mates were greater risk-takers; they approached females more rapidly and to closer proximity, regardless of risk. In a second experiment, we altered male encounter rate with females and measured rates of sexual cannibalism when paired with hungry or well-fed females. Greater risk-taking behavior by males with low mate encounter rates resulted in high rates of sexual cannibalism when these males were paired with hungry females

Eyespots deflect predator attack increasing fitness and promoting the evolution of phenotypic plasticity

Some eyespots are thought to deflect attack away from the vulnerable body, yet there is limited empirical evidence for this function and its adaptive advantage. Here, we demonstrate the conspicuous ventral hindwing eyespots found on Bicyclus anynana butterflies protect against invertebrate predators, specifically praying mantids. Wet season (WS) butterflies with larger, brighter eyespots were easier for mantids to detect, but more difficult to capture compared to dry season (DS) butterflies with small, dull eyespots. Mantids attacked the wing eyespots of WS butterflies more frequently resulting in greater butterfly survival and reproductive success. With a reciprocal eyespot transplant, we demonstrated the fitness benefits of eyespots were independent of butterfly behaviour. Regardless of whether the butterfly was WS or DS, large marginal eyespots pasted on the hindwings increased butterfly survival and successful oviposition during predation encounters. In previous studies, DS B. anynana experienced delayed detection by vertebrate predators, but both forms suffered low survival once detected. Our results suggest predator abundance, identity and phenology may all be important selective forces for B. anynana. Thus, reciprocal selection between invertebrate and vertebrate predators across seasons may contribute to the evolution of the B. anynana polyphenism

Радиационная стойкость нитевидных кристаллов SiGe, используемых для сенсоров физических величин

Приведены результаты исследования влияния облучения γ-квантами дозами до 1·10¹⁸ см⁻² и магнитного поля с индукцией до 14 Тл на электропроводность нитевидных кристаллов Si1-xGex в интервале температуры 4,2-300 К.Вивчено вплив опромінення γ-квантами (випромінювання Co⁶⁰) з дозами до 1·10¹⁸ см⁻² та магнітного поля з індукцією до 14 Тл на електропровідність ниткоподібних кристалів Si1-xGex (х = 0,03) з питомим опором 0,08,0,025 Ом·см в інтервалі температур 4,2 .300 К. Встановлено, що опір кристалів слабо змінюється в процесі опромінення дозами до 2·10¹⁷ см⁻², в той же час спостерігаються істотні зміни магнітоопору. На основі проведених досліджень запропоновано умови створення радіаційно стійких сенсорів деформації, дієздатних в умовах сильних магнітних полів.An influence of γ-irradiation (Co⁶⁰) with doze up to 1·10¹⁸ cm⁻² and magnetic field with induction up to 14 T on conduction of Si1-xGex (x = 0,03) whisker crystals with resistivity of 0,08-0,025 Ohm·cm in temperature range 4,2-300 K have been studied. It is shown that whisker crystals resistance faintly varies under irradiation with doze 2·10¹⁷ cm⁻², while their magnetoresistance substantially changes. The strain sensors stable to irradiation action operating in high magnetic fields on the base of the whiskers have been designed