Multisensory stimuli provide organisms with information to assess the threat present in the surroundings. Olfactory cues show dominance over other sensory modalities in the aquatic environment. The impact of chemical predator cues combined with experiences gained (learning) in species without previous contact is not fully understood. We investigated the foraging and shelter-seeking behaviour of naïve and experienced marbled crayfish Procambarus virginalis juveniles in response to the chemical signals of pumpkinseed Lepomis gibbosus alone and in combination with alarm chemicals produced by preyed-upon conspecifics. Naïve and experienced (previously exposed to pumpkinseed predation) juveniles were stocked in an arena with shelter and feed and exposed (1) to water from a tank containing a predator actively feeding on conspecifics, (2) water from a tank with predator only and (3) water only as control. Crayfish exposed to the combined stimuli avoided the inlet zone and gravitated to shelter zone of the arena to a greater extent than did those exposed to predator-only cues and the control. Regardless of the treatment, experienced crayfish showed significantly reduced interest in feeding. Our findings imply that crayfish response to threat-associated odours with the greatest potency when visual or tactile cues are present, while previous encounters with predators may make them more cautious.

• Keywords
• alarm cues, crayfish, fish, infochemicals, kairomones, predation,
• Publication type
• Journal Article MeSH

Spore awakening is a series of actions that starts with purely physical processes and continues via the launching of gene expression and metabolic activities, eventually achieving a vegetative phase of growth. In spore-forming microorganisms, the germination process is controlled by intra- and inter-species communication. However, in the Streptomyces clade, which is capable of developing a plethora of valuable compounds, the chemical signals produced during germination have not been systematically studied before. Our previously published data revealed that several secondary metabolite biosynthetic genes are expressed during germination. Therefore, we focus here on the secondary metabolite production during this developmental stage. Using high-performance liquid chromatography-mass spectrometry, we found that the sesquiterpenoid antibiotic albaflavenone, the polyketide germicidin A, and chalcone are produced during germination of the model streptomycete, S. coelicolor. Interestingly, the last two compounds revealed an inhibitory effect on the germination process. The secondary metabolites originating from the early stage of microbial growth may coordinate the development of the producer (quorum sensing) and/or play a role in competitive microflora repression (quorum quenching) in their nature environments.

• Keywords
• Streptomyces, albaflavenone, cell signaling, chalcone, germicidin, secondary metabolism, spore germination,
• Publication type
• Journal Article MeSH