Chemical composition of anal droplets of the eusocial gall-inducing thrips Kladothrips intermedius

Kocuria flava, a Bacterial Endophyte of the Marine Macroalga Bryopsis plumosa, Emits 8-Nonenoic Acid Which Inhibits the Aquaculture Pathogen Saprolegnia parasitica

Secondary metabolites-organic compounds that are often bioactive-produced by endophytes, among others, provide a selective advantage by increasing the organism's survivability. Secondary metabolites mediate the symbiotic relationship between endophytes and their host, potentially providing the host with tolerance to, and protection against biotic and abiotic stressors. Secondary metabolites can be secreted as a dissolved substance or emitted as a volatile. In a previous study, we isolated bioactive endophytes from several macroalgae and tested them in vitro for their ability to inhibit major disease-causing pathogens of aquatic animals in the aquaculture industry. One endophyte (isolate Abp5, K. flava) inhibited and killed, in vitro, the pathogen Saprolegnia parasitica, an oomycete that causes saprolegniasis-a disease affecting a wide range of aquatic animals. Here, using analytical chemistry tools, we found that Abp5 produces the volatile organic compound (VOC) 8-nonenoic acid. Once we confirmed the production of this compound by the endophyte, we tested the compound's ability to treat S. parasitica in in vitro and in vivo bioassays. In the latter, we found that 5 mg/L of the compound improves the survival of larvae challenged with S. parasitica by 54.5%. Our isolation and characterization of the VOC emitted by the endophytic K. flava establish the groundwork for future studies of endophytic biocontrol agents from macroalgae. Use of this compound could enable managing oomycete agricultural pathogens in general, and S. parasitica in particular, a major causal agent in aquaculture diseases.

Ultrastructure and distribution of antennal sensilla of the chilli thrips Scirtothrips dorsalis hood (Thysanoptera: Thripidae)

The chilli thrips, Scirtothrips dorsalis Hood, is a serious pest of numerous important vegetable and ornamental crops. Various signals, especially phytochemical cues, determine the behavior of the phytophagous thrips at host selection. The sensory abilities of S. dorsalis are poorly understood although the antennae of adult are known to possess important sensory structures in orther insects. In this study, the morphology, distribution, and ultrastructure of the antennal sensilla of the S. dorsalis were examined by using scanning and transmission electron microscopy. Microscopy observations revealed that adult male and female S. dorsalis possess filiform antennae. Each antenna comprises a scape, a pedicel, and a flagellum composed of six segments without clear sexual dimorphism in the number and distribution of antennal sensilla. The scape and pedicel exhibit Böhm's bristles, sensilla chaetica, and sensilla campaniform. The external structures of these organs reveal their mechanosensory function. In the flagellum, the most represented sensilla are the multiporous sensilla basiconica, which can be divided into three types of single-walled olfactory sensilla; three types of sensilla chaetica with mechanosensory and gustatory functions; sensilla coeloconica, which possess hollow cuticular spoke channels and represent double-walled olfactory sensilla; sensilla capitula and sensilla cavity with thermo-hygrosensory functions; and aporous sensilla trichodea with smooth cuticula and mechanosensory function. The putative function of described sensilla is discussed in ralation to host plant selection behavior of S. dorsalis.