@article {1123808, title = {Putative thermo-/hygroreceptive tarsal sensilla on the sensory legs of an armored harvestman (Arachnida, Opiliones).}, journal = { Zoologischer Anzeiger }, volume = {270}, year = {2017}, pages = {81-97.}, abstract = {Most harvestman species are dependent on high humidity levels and amenable temperatures for homeostasis. While they are known to actively choose environments with these conditions, no thermo-/hygroreceptor has yet been identified in harvestmen. Using electron microscopy, we investigated the ultrastructure of two types of hair sensilla of the armored harvestman Heteromitobates discolor (Laniatores, Gonyleptidae): namely the sensillum basiconicum and the hooded sensillum. Both structures occur in small numbers (sensilla basiconica: 28 units; hooded sensilla: 4 units) and are distributed on the distal parts of the legs. On the distalmost tarsomeres I and II, the receptor cells of paired sensilla basiconica and single hooded sensillum form a common axon bundle proceeding towards the tarsal nerve. The sensillum basiconicum is innervated by 3-4 dendrites and has a longitudinal slit giving the impression of a shaft with two flaps, resembling a beak. The slit probably allows for evaporation of sensillum lymph. The hooded sensillum is innervated by two bundles of three dendrites each, has two pore-like structures on its tip and displays an unusual reticulate cuticle of the shaft. Details of shaft cuticle, the evidence of evaporation of sensillum lymph, and specific innervation patterns support our hypothesis that sensilla basiconica are thermo- and/or hygroreceptors. Even though the definite function of hooded sensilla remains unclear, its putative receptor modalities are assessed by means of specific ultrastructures. Moreover, we discuss with regard to functional ultrastructures as to whether the evaporation system of sensilla basiconica fits mechanisms of hygroreception as known from current literature. Finally, we discuss potentials and purpose given by spatial coherence of both types of sensilla at the tip of the sensory appendages.
Putative thermo-/hygroreceptive tarsal... (PDF Download Available). Available from: https://www.researchgate.net/publication/320319517_Putative_thermo-hygroreceptive_tarsal_sensilla_on_the_sensory_legs_of_an_armored_harvestman_Arachnida_Opiliones [accessed Apr 24 2018].}, author = {Gainett, G. and Michalik, P. and M{\"u}ller, C. H. G. and Giribet, G. and Talarico, G and Willemart, R. H.} }