González-Tokman Daniel, Ruch Jasmin, Pulpitel Tamara, Ponton Fleur
Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México, México D. F., México.
Biocenter Grindel & Zoological Museum, University of Hamburg, Hamburg, Germany; Department of Biological Sciences, Macquarie University, Sydney, Australia.
PLoS One. 2014 Mar 17;9(3):e91785. doi: 10.1371/journal.pone.0091785. eCollection 2014.
Animals living in groups face a high risk of disease contagion. In many arthropod species, cuticular antimicrobials constitute the first protective barrier that prevents infections. Here we report that group-living spiders produce cuticular chemicals which inhibit fungal growth. Given that cuticular antifungals may be costly to produce, we explored whether they can be modulated according to the risk of contagion (i.e. under high densities). For this purpose, we quantified cuticular antifungal activity in the subsocial crab spider Diaea ergandros in both natural nests and experimentally manipulated nests of varying density. We quantified the body-condition of spiders to test whether antifungal activity is condition dependent, as well as the effect of spider density on body-condition. We predicted cuticular antifungal activity to increase and body-condition to decrease with high spider densities, and that antifungal activity would be inversely related to body-condition. Contrary to our predictions, antifungal activity was neither density- nor condition-dependent. However, body-condition decreased with density in natural nests, but increased in experimental nests. We suggest that pathogen pressure is so important in nature that it maintains high levels of cuticular antifungal activity in spiders, impacting negatively on individual energetic condition. Future studies should identify the chemical structure of the isolated antifungal compounds in order to understand the physiological basis of a trade-off between disease prevention and energetic condition caused by group living, and its consequences in the evolution of sociality in spiders.
群居动物面临着疾病传播的高风险。在许多节肢动物物种中，表皮抗菌物质构成了防止感染的第一道保护屏障。在此我们报告，群居蜘蛛会产生抑制真菌生长的表皮化学物质。鉴于表皮抗真菌物质的产生可能成本高昂，我们探究了它们是否能根据传播风险（即在高密度情况下）进行调节。为此，我们在自然巢穴以及实验操控的不同密度巢穴中，对亚社会性蟹蛛Diaea ergandros的表皮抗真菌活性进行了量化。我们对蜘蛛的身体状况进行了量化，以测试抗真菌活性是否依赖于身体状况，以及蜘蛛密度对身体状况的影响。我们预测，随着蜘蛛密度的增加，表皮抗真菌活性会增强，而身体状况会下降，并且抗真菌活性与身体状况呈负相关。与我们的预测相反，抗真菌活性既不依赖于密度也不依赖于身体状况。然而，在自然巢穴中，身体状况随密度下降，但在实验巢穴中却上升。我们认为，病原体压力在自然界中非常重要，以至于它维持了蜘蛛表皮的高抗真菌活性水平，对个体能量状况产生了负面影响。未来的研究应该确定分离出的抗真菌化合物的化学结构，以便了解群居生活导致的疾病预防与能量状况之间权衡的生理基础，以及它在蜘蛛社会性进化中的后果。
