The labidostommatid palpus: a morphological enigma (Acariformes: Prostigmata)
Citation
Lindquist, E.E. & Sidorchuk, E.A. 2015. The labidostommatid palpus: a morphological enigma (Acariformes: Prostigmata). Acarologia 55(3): 337–350.
Plain language summary
The morphology of the palps of a group of mites (family: Labidostommatidae) is studied from an evolutionary perspective. The palps are appendages of mites and of related invertebrates that are typically used for sensing, whether it’s a prey (food), predator, or members of their own species. Labidostommatid mites are predators of small invertebrates, and abundant in Canadian soil ecosystems.
Abstract
Hypotheses are reviewed concerning which segments of the primitively five-segmented palpus are coalesced to form the simple, linear, four-segmented form characteristic of labidostommatid mites. Among alternatives, those of either a femurogenu or a tibiotarsus are not based on convincing evidence. Instead, based on ontogeny of the peculiar palpal structure and chaetome of labidostommatids, a case is made that the proximal segment, which bears a single, ventral, postlarval seta, is a basifemur, with the trochanter autapomorphically either coalesced with it or subsumed into the base. Consequently, the second segment is a telofemur, articulating with the third article, which is an unusual, coalescent genuotibia. The phylogenetic significance of various interpretations of segmental coalescence are considered. Ontogenetic studies of palpal musculature and gene expression are needed to provide more substantive evidence.