Natures wonders: plant poison helps a larva (Introduction)

by David Turell , Friday, August 26, 2016, 18:22 (3009 days ago) @ David Turell

Plants put out chemicals to deter herbivores from eating them. This larva uses the chemical to protect itself from infections:-http://phys.org/news/2016-08-moth-advantage-defensive-compounds-physalis.html-"The larva of the specialist moth Heliothis subflexa climbs the calyx of a Physalis, which is also called ground cherry. The fruit, which is inside the calyx, provides the caterpillar with a perfect shelter from enemies, once it has entered the calyx. Moreover, the fruit contains withanolides, which have antibacterial properties and boost the larva's immune system.-"The researchers measured and compared the effects of withanolides on relative weight gains, survival rates and the immune status in two moth species: the specialist Heliothis subflexa and the generalist Heliothis virescens. They knew from earlier studies that the specialist moth possesses a weaker immune response compared to the closely related generalist. "We were surprised to find that only Heliothis subflexa benefits from withanolides by increasing larval growth and immune system activity, but not its close relative, Heliothis virescens," ...-***-"The medicinal importance of Physalis plants is mainly due to the presence of steroidal lactones, the withanolides. Withanolides exhibit potential anti-cancer, anti-inflammatory and apoptotic activities. However, the actual role of withanolides in Physalis plants is defence against herbivores. Withanolides have been shown to be potent anti-feeding deterrents as well as immunosuppressants in insects. These effects can be attributed to possible interactions of withanolides with signal transduction pathways in the cells. For instance, previous studies have shown that withanolides may cause moulting disorders in insects, suggesting that the anti-feeding and immunosuppressive effects arise from the disruptive effect of withanolides on the development of non-adapted insects. These toxic effects of withanolides on herbivorous insects suggest an adaptive benefit, since few insect species are known to feed on Physalis plants with impunity.-***-"Heliothis subflexa larvae feed exclusively on Physalis fruits, and it is the only Heliothis species to do so. Physalis fruits are enclosed by a thin-walled, inflated calyx called a "lantern". The lantern provides a so-called enemy-free space for fruit-feeding larvae of Heliothis subflexa, which could be demonstrated in earlier studies. However, the impact of withanolides on specialized Heliothis subflexa had not been evaluated prior to this study. With the known immunosuppressive properties of withanolides in mind, the researchers aimed to examine the specialization of Heliothis subflexa on Physalis in the context of ecological immunology. "Ecological immunology combines classical studies of the immune system with an ecological perspective to evaluate the costs and benefits of defence against pathogens in the natural environment, and the manner in which natural selection shapes the immune system," explains Andrea Barthel, the first author of the publication."-Comment: Since a related species cannot eat this plant, one must wonder how this larva developed a method to circumvent the chemical deterrent and enjoy the meals. It is an interesting arrangement. The plant doesn't benefit, only the larva.