Morphological structures and vertical distribution in the soil indicate facultative plastron respiration in Cryptocellus adisi (Arachnida, Ricinulei) from Central Amazonia

Abstract

In primary and secondary upland forests of Central Amazonia, Cryptocellus becki inhabits predominantly the organic layer of latosols (top 3.5 cm) whereas immatures of the smaller C. adisi live in the mineral subsoil as well (below 3.5 cm). C. adisi has hydrophobic navicular and calyx-like setae on its body and legs as well as alveolate, microtrichia-covered depressions on the cuticular surface. These plastron retaining structures, lacking in C. becki, apparently prevent C. adisi from getting wet during heavy rainfall and allow (facultative) plastron respiration if the mineral subsoil is temporarily inundated. Bristle-shaped microtrichia cover the elevated atrium wall of the spiracles in both species and these structures are shown for the first time by scanning electron micrographs.