Beauty under the mud: Soil crypsis in new species of the Malagasy genus Ankaratrix (Opiliones: Triaenonychidae: Triaenobuninae)

Abstract

Camouflaging with crypsis is a known strategy in several invertebrates such as sea urchins, gastropods, crabs, and immature stage of insects. In harvestmen, soil crypsis are used as a defense strategy. The soil particles are attached to their bodies using secretions. Here we investigate this kind of camouflage in the Malagasy endemic genus Ankaratrix. Members of this genus produce a glue layer (= solidifying secretion) covering the cerotegument. This glue layer seems to play an important role in soil crypsis, together with the long tubercles or cuticular apophyses. These long tubercles could help to catch and retain the soil particles bringing stability to the camouflage layer. The specimens are covered by a very thick soil layer, determined by the tubercle sizes, mainly on the dorsal body surface. Only the body parts involved in feeding (chelicerae, pedipalps, feeding apparatus), reproduction (genital operculum), excretion (anal operculum) and sensory functions (leg tarsi) are clean of mud. Legs I exhibit a very long longitudinal row of spiniform apophyses that will be completely covered by soil, forming a kind of wall that protect the chelicerae and pedipalp of the dirt and could be adopted as camouflage strategy in thanatosis or resting periods. During our investigation, we discovered four new species, which are described herein: Ankaratrix maloto sp. nov., Ankaratrix makamba sp. nov., Ankaratrix fisheri sp. nov., Ankaratrix lawrencei sp. nov. Finally, we discuss the sexual dimorphism in pedipalps of the genus Ankaratrix.