Compartmental distribution of free amino acids and protein in developing yolk-sac larvae of Atlantic halibut (Hippoglossus hippoglossus)

Free amino acids (FAA) and protein have been measured in whole laboratory-readed halibut larvae and on dissected individuals separated into yolk and body compartments. At hatching both FAA and protein are mainly located in the yolk compartment. During the first 12 d of the yolk-sac stage more than 70% of the FAA pool disappeared from the yolk without any significant changes in the yolk protein pool. This suggests different uptake mechanisms for FAA and protein from the yolk, and a sequential utilisation of the endogeneous reservoirs of free and protein amino acids in Atlantic halibut larvae. The data suggest that in the early yolk-sac stage FAA enter the embryo from the yolk and are utilised both for energy and protein synthesis. Later on when the free pool cannot fulfil the nutritional requirements, additional amino acids are recruited from yolk protein. Of the total amino acids (free + protein amino acids) present at hatching ca. 60% will be used as precursors for body protein synthesis while the remaining 40% are used as fuel in the larval energy metabolism.     

“Sleeping with the enemy”—predator-induced diapause in a mite

Diapause in arthropods is a physiological state of dormancy that is generally thought to promote survival during harsh seasons and dispersal, but it may also serve to avoid predation in space and time. Here, we show that predation-related odours induce diapause in female adult spider mites. We argue that this response allows them to move into an area where they are free of enemies, yet forced to survive without food. Spider mites are specialised leaf feeders, but—in late summer—they experience severe predation on leaves. Hence, they face a dilemma: to stay on the leaf and risk being eaten or to move away from the leaf and risk death from starvation and thirst. Female two-spotted spider mites solve this dilemma by dramatically changing their physiology when exposed to predation-associated cues. This allows them to disperse away from leaves and to survive in winter refuges in the bark of trees or in the soil. We conclude that the mere presence of predation-associated cues causes some herbivorous mites to seek refuge, thereby retarding the growth rate of the population as a whole: a trait-mediated indirect effect that may have consequences for the stability of predator–prey systems and for ecosystem structure.     

Ultrasonic courtship song in the Asian corn borer moth, Ostrinia furnacalis

Although sex pheromone communication in the genus Ostrinia (Lepidoptera: Crambidae) has been studied intensively, acoustic communication in this genus has not been explored. In this study, we report that male-produced ultrasound serves as a courtship song in the Asian corn borer moth, O. furnacalis. Upon landing close to a pheromone-releasing female, a male showed a series of courtship behaviors involving emission of ultrasound. The sounds were produced when the wings were vibrated quickly in an upright position. The male song was composed of chirps, i.e., groups of pulses (duration of a chirp = 58.9 ms, 8.8 pulses/chirp), with a broadband frequency of 25–100 kHz. In flight tunnel experiments, deaf and hearing females showed a significant difference in the incidence of three behavioral responses to courting males, i.e., immediate acceptance, acceptance after walking, and rejection. Deaf females showed more ‘rejection’ and less ‘acceptance after walking’ than hearing females, indicating that the detection of male-produced ultrasound plays an important role in the acceptance of a male. The findings are discussed in the context of exploitation of receiver bias and mate choice.