CONSTELLATION ARRAY: A NEW SENSORY STRUCTURE IN SCORPIONS (ARACHNIDA: SCORPIONES)

“…Striking modifications of the cuticle have turned much of its surface into an information-gathering device.” (Shear, 1999, p. 5) Abstract: A peculiar constellation-shaped microscopic array of several chemosensory sensilla is described for the first time in scorpions. This sensillar array is located on the external aspect of the distal portion of the fixed finger of pedipalp. We present data on the constellation array across four parvorders, six superfamilies, 12 families, 23 genera, and 28 species of extant (or-thostern) scorpions. The constellation array was observed in all scorpion taxa. Observed number of sensilla in the constellation array varied from one (Vejovoidus) to 15 (Calchas), on average 6 ± 3; the size of the sensillum is 5-10 µm, their shape varying from conical to hair-like. The sensilla are socketed, and appearance of their “button-like ” socket areola differs from other mech-anosensory and chemosensory setae common on the scorpion’s body and appendages. As observed in Calchas nordmanni (Iuridae) and Euscorpius tergestinus (Euscorpiidae), there was no difference in number of sensilla between juveniles and adults. The constellation array size (maximal distance between two sensilla) usually varied between 100 to 300 µm, with Buthi-dae arrays markedly smaller in size. There was no apparent correlation between the size of a species and constellation array size. This ultrastructural character can be potentially of diagnostic use in scorpion systematics at family and genus levels. W