TY - JOUR

T1 - A rudimentary sheath for the smallest of “biting” chelicerae

T2 - the mouthparts of Cunliffea (Nematalycidae) and a new hypothesis on the origin of the stylet sheath of Eriophyoidea (Acariformes)

AU - Bolton, Samuel J.

AU - Bauchan, Gary R.

AU - Chetverikov, Philipp E.

AU - Ochoa, Ronald

AU - Klompen, Hans

N1 - Funding Information: This research was partly funded by the Smithsonian Institution (pre-doctoral fellowship). Thanks to Chris Pooley for editing and arranging the LT-SEM image plates. We thank the Florida Department of Agriculture and Consumer Services – Division of Plant Industry for their support on this contribution. Acknowledgements are also due to the US National Park Service for granting the first author permission to collect from the Indiana Dunes National Lakeshore, and to the helpful comments and criticisms of three anonymous reviewers. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA; USDA is an equal opportunity provider and employer. Figures 2–5 in this publication are sourced from the US Department of Agriculture, Agricultural Research Service, Electron and Confocal Microscopy Unit, Beltsville, Maryland, USA. These images are in the public domain. Funding Information: This research was partly funded by the Smithsonian Institution (pre-doctoral fellowship). Publisher Copyright: © 2018, © 2018 Informa UK Limited, trading as Taylor & Francis Group. Copyright: Copyright 2019 Elsevier B.V., All rights reserved.

PY - 2018/11/17

Y1 - 2018/11/17

N2 - The cheliceral digits of soil inhabiting Nematalycidae are among the shortest of any chelicerate (≈5 µm long). But Eriophyoidea, which may be nested within Nematalycidae, have relatively long (10–70 µm), styliform cheliceral digits that are enveloped within a subcapitular sheath. Scanning electron microscopy observations on the mouthparts of a nematalycid, Cunliffea cf. strenzkei (Cunliffe), show it has a rudimentary sheath for chelate (“biting”) chelicerae. This discovery–presented herein–is the basis for a new hypothesis, which 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 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.

AB - The cheliceral digits of soil inhabiting Nematalycidae are among the shortest of any chelicerate (≈5 µm long). But Eriophyoidea, which may be nested within Nematalycidae, have relatively long (10–70 µm), styliform cheliceral digits that are enveloped within a subcapitular sheath. Scanning electron microscopy observations on the mouthparts of a nematalycid, Cunliffea cf. strenzkei (Cunliffe), show it has a rudimentary sheath for chelate (“biting”) chelicerae. This discovery–presented herein–is the basis for a new hypothesis, which 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 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.

KW - chelate

KW - Chelicerae

KW - Cunliffea

KW - Eriophyoidea

KW - gnathosoma

KW - Nematalycidae

KW - sheath

KW - styliform

KW - Trombidiformes

UR - http://www.scopus.com/inward/record.url?scp=85050347442&partnerID=8YFLogxK

U2 - 10.1080/01647954.2018.1488274

DO - 10.1080/01647954.2018.1488274

M3 - Article

AN - SCOPUS:85050347442

VL - 44

SP - 374

EP - 381

JO - International Journal of Acarology

JF - International Journal of Acarology

SN - 0164-7954

IS - 8

ER -