The Chemosensory Toolkit of a Cursorial Spider

Background Chemosensation is vital for organisms to detect food, avoid predators, and find mates. Spiders, like many arthropods, rely on chemosensory input, but the modes and structures for detecting chemicals are not well understood. Cursorial spiders use chemical information for orientation and mate-finding. Behavioral studies suggest gustation plays a major role in male spiders following silken draglines to locate females, but the role of olfaction and tools involved in chemosensing are not known, despite the important ecological role of spiders. Results High-resolution electron microscopy revealed two types of chemosensory sensilla in the cursorial spider Pisaura mirabilis . Tip-pore sensilla, on the walking legs and pedipalps of both sexes, support contact chemoreception. Wall-pore sensilla, only occurring on adult male walking legs, are associated with olfaction. Behavioral assays confirmed that males detect airborne chemical signals from females, supporting these sensilla's role in mate search. The distribution of both sensilla types on walking legs is nearly complementary, with tip-pore sensilla towards leg tips and wall-pore sensilla towards leg bases supporting their respective contact and olfactory functions. Conclusions This study links the morphology, location, and function of chemosensory organs in cursorial spiders, providing insights into their chemosensory world. The findings advance the understanding of chemical sensing evolution in spiders and have implications for broader arthropod research. The identification of specialized olfactory sensilla in male spiders highlights the significance of airborne chemical detection in mate-finding, while contact chemoreceptors in both sexes suggest a general role in environmental chemical sensing.