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1 April 2018 Putative adhesive setae on the walking legs of the Paleotropical harvestman Metibalonius sp. (Arachnida: Opiliones: Podoctidae)
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We provide a first scanning electron microscopy examination of the Paleotropical harvestman family Podoctidae (Opiliones: Laniatores), focusing on the distitarsus of the legs of Metibalonius sp. Distitarsi I and II are mostly equipped with olfactory sensilla chaetica with wall pores, while those of legs III and IV have gustatory sensilla chaetica with a tip pore, ventral trichomes with ovate tips (non-sensory) and a type of spatulate seta. Spatulate setae are present in adults of both sexes, with no apparent sexual dimorphism, but they are absent in the nymph. Seven of these setae are inserted on the frontal surface of the last tarsomere of legs III and IV, with the tips oriented ventrally. Each seta has an s-shaped socketed shaft, which terminates distally in a spatula-shaped structure. The distribution of spatulate setae, restricted to legs III and IV (walking legs), the position on the distitarsi, and the typical spatulate shape suggest an adhesive function for these structures. Morphology and position suggest that the socketed spatulate setae of Metibalonius sp. and the previously reported scopular spatulate setae of other harvestmen constitute two distinct types of adhesive structures, highlighting the diversity of adhesive structures in Laniatores. Future investigations about the natural history of this species and internal morphology of spatulate setae are necessary to test further functional hypotheses and to determine their behavioral role.

Guilherme Gainett, Prashant P. Sharma, Gonzalo Giribet, and Rodrigo H. Willemart "Putative adhesive setae on the walking legs of the Paleotropical harvestman Metibalonius sp. (Arachnida: Opiliones: Podoctidae)," The Journal of Arachnology 46(1), 62-68, (1 April 2018).
Received: 4 July 2017; Published: 1 April 2018

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