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CONSTANCY OF STYLOSTOME FORM IN TWO WATER MITE SPECIES

Published online by Cambridge University Press:  31 May 2012

Carmine A. Lanciani
Affiliation:
Department of Zoology, University of Florida, Gainesville, Florida, USA 3261 1 and Department of Biology, University of New Brunswick, Fredericton, New Brunswick, Canada E3B 6E1
Bruce P. Smith
Affiliation:
Department of Zoology, University of Florida, Gainesville, Florida, USA 3261 1 and Department of Biology, University of New Brunswick, Fredericton, New Brunswick, Canada E3B 6E1

Abstract

Recent studies have suggested that the stylostome of parasitic larval water mites of the genus Arrenurus Dugès is a product of the mite, not the host. We tested this hypothesis by comparing stylostomes of the similar species Arrenurus novimarshallae Wilson and Arrenurus pseudotenuicollis Wilson formed in each of two mosquito species, Anopheles crucians Wiedemann and Anopheles quadrimaculatus Say: if the stylostome is produced by the mite, not the host, then stylostome form is likely to be constant in different host species parasitized by the mite.

The stylostome of A. pseudotenuicollis is a short, broad, convoluted sac, and stylostomes within the two host species did not differ significantly. The stylostome of A. novimarshallae is a long, thin, convoluted tube, and although it was significantly smaller in A. quadrimaculatus than in A. crucians, its form remained constant. Dark pigment deposits around the stylostome’s attachment point and along the tube may represent host defense that reduces stylostome growth in A. quadrimaculatus. Laboratory-reared A. novimarshallae often die after a brief engorgement period on A. quadrimaculatus but not on A. crucians.

Thus, the stylostome of these two mite species has a consistent form in each of two host species, an observation compatible with the hypothesis that the stylostome is a product of the mite. In addition, the ease of distinguishing these two mite species on the basis of stylostome morphology attests to the potential value of the stylostome as a taxonomic character.

Résumé

Des études récentes ont permis de suggérer que la stylostome des larves de mites d’eau parasitiques du genre Arrenurus Dugès est un produit de l’acarien plutôt que de l’hôte. Nous avons testé cette hypothèse en comparant les stylostomes des espèces similaires Arrenurus novimarshallae Wilson et Arrenurus pseudotenuicollis Wilson, formés dans deux espèces de moustiques, Anopheles crucians Wiedemann et Anopheles quadrimaculatus Say : si le stylostome est produit par l’acarien, la forme du stylostome devrait être constante dans différentes espèces d’hôtes parasitées par la même espèce de mite.

Le stylostome de A. pseudotenuicollis est un sac court, large, convoluté; les stylostomes formés chez les deux espèces d’hôtes étaient sans différence significative. Le stylostome de A. novimarshallae est un tube long, mince, convoluté, et quoique significativement plus petit chez A. quadrimaculatus que chez A. crucians, sa forme est la même. Des dépôts pigmentaires noirs autour du pont d’attache du stylostome et le long du tube pourraient indiquer une réaction de défense de l’hôte réduisant la croissance du stylostome chez A. quadrimaculatus. Les A. novimarshallae élevés au laboratoire meurent souvent après un bref engorgement chez A. quadrimaculatus mais pas chez A. crucians.

Ainsi, le stylostome de ces deux espèces de mite a une forme semblable chez deux espèces de moustiques, observation qui est compatible avec l’hypothèse voulant que le stylostome est produit par l’acarien. De plus, la facilité de distinction entre les deux espèces d’acariens d’après la morphologie du stylostome atteste de la valeur taxonomique de ce trait.

Type
Articles
Copyright
Copyright © Entomological Society of Canada 1989

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