A rudimentary sheath for the smallest of ‘biting’ chelicerae; A precursor to the stylet sheath of Eriophyoidea (Acariformes)

Authors: BOLTON, S. - The Ohio State University; Bauchan, Gary; CHETVERIKOV, P. - Russian Academy Of Sciences; Ochoa, Ronald - Ron; KLOMPEN, HANS - The Ohio State University

Submitted to: International Journal of Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/27/2018
Publication Date: 12/1/2018
Citation: Bolton, S.J., Bauchan, G.R., Chetverikov, P.E., Ochoa, R., Klompen, H. 2018. A rudimentary sheath for the smallest of ‘biting’ chelicerae; A precursor to the stylet sheath of Eriophyoidea (Acariformes). International Journal of Acarology. 44(8):374-381.

Interpretive Summary: Morphological studies on the mouth parts of primitive mites were studied to understand the evolutionary pathways for the development of plant feeding mites. Modern microscopy technologies of fluorescent confocal laser scanning microscopy and low temperature scanning electron microscopy were utilized to image a mite that has some unusual mouthparts that function in a similar way to those of the four legged plant-parasitic mites. This is a large and important linage to plant-parasitic mites. These mouthparts appear to explain how the mouthparts of plant feeding mites may have originated. This new hypothesis, if correct, would advance our understanding of the one of the most complex mouthpart morphologies among all mites. This information is important to researchers, biocontrol and quarantine programs, integrated pest management specialists, entomologists, phytopathologist, ecologists, and especially persons involved in mite studies.

Technical Abstract: The cheliceral digits of soil inhabiting Nematalycidae are among the shortest of any chelicerate. But Eriophyoidea, which may be nested within Nematalycidae, have long, styliform cheliceral digits that are enveloped within a subcapitular sheath. SEM observations on the mouthparts of a nematalycid, Cunliffea cf. strenzkei (Cunliffe), show it has a rudimentary sheath for chelate (‘biting’) chelicerae. A new hypothesis, based on this discovery, proposes that the stylet sheath of Eriophyoidea could have originated when the chelicerae were still chelate. Accordingly, the sheath would have originally covered the space between the fixed and movable digits, extending the preoral cavity (a hermetically sealed channel) anteriorly. As the digits became increasingly styliform, the sheath would have expanded around them, otherwise the hermetic seal of the preoral cavity would have been compromised. The sheath would have expanded for this reason until it reached its extant form, which completely envelops the digits.