Dabert, M. | bioRxiv Science

bioRxiv2021

Species boundaries among extremely diverse and sexually dimorphic Arrenurus water mites (Acariformes: Hydrachnidiae: Arrenuridae)

Arrenurus (Arrenuridae) is the most species-rich genus of mites with about 950 named species that inhabit standing, and to a lesser extent, running water habitats around the world. To date, distinguishing species of Arrenurus has been based on male reproductive morphology. Here, we use morphological and molecular approaches to examine species boundaries among 42 named species of Arrenurus, including four named species that have colour variants (red and green A. americanus, and red and blue A. intermedius, A. manubriator and A. apetiolatus), and two unnamed morphospecies. In this study, we examine male genital structures with the use of SEM techniques, and apply mitochondrial (COI barcode region) and nuclear (28S rRNA) gene fragments to test whether male morphology reflects species boundaries in Arrenurus assessed by molecular analyses. Our results reveal that male reproductive morphology parallels species boundaries as judged by molecular data. We discuss the cases of genetically poorly diversified, yet morphologically clearly defined named species. Moreover, we show that based on the species we examined, colour morphs within otherwise morphologically similar specimens represent within-species variation and, in the absence of other diagnostic traits, colour itself can be misleading in distinguishing species. Our outcomes on molecular taxonomy of Arrenurus provide a background for testing hypotheses about speciation rate in water mites.

zoology↗

bioRxiv2018

Microbial composition of enigmatic bird parasites: Wolbachia and Spiroplasma are the most important bacterial associates of quill mites (Acari:Syringophilidae)

The microbiome is an integral component of many animal species, potentially affecting behaviour, physiology, and other biological properties. Despite this importance, bacterial communities remain vastly understudied in many groups of invertebrates, including mites. Quill mites (Acariformes: Syringophilidae) are a poorly known group of permanent bird ectoparasites that occupy quills of feathers and feed on bird subcutaneous tissue and fluids. Most species have strongly female biased sex ratios and it was hypothesized that this is caused by endosymbiotic bacteria. Their peculiar lifestyle further makes them potential vectors for bird diseases. Previously, Anaplasma phagocytophilum and a high diversity of Wolbachia strains were detected in quill mites via targeted PCR screens. Here, we use an unbiased 16S amplicon sequencing approach to determine other Bacteria that potentially impact quill mite biology.\n\nWe performed 16S V4 amplicon sequencing of 126 quill mite individuals from eleven species parasitizing twelve bird species (four families) of passeriform birds. In addition to Wolbachia, we found Spiroplasma as potential symbiont of quill mites. Interestingly, consistently high Spiroplasma titres were only found in individuals of two mite species associated with finches of the genus Cardfuelis, suggesting a history of horizontal transfers of Spiroplasma via the bird host. Furthermore, there was evidence for Spiroplasma negatively affecting Wolbachia titres. We found no evidence for the previously reported Anaplasma in quill mites, but detected the potential pathogens Brucella and Bartonella at low abundances. Other amplicon sequence variants (ASVs) could be assigned to a diverse number of bacterial taxa, including several that were previously isolated from bird skin. We observed a relatively uniform distribution of these ASVs across mite taxa and bird hosts, i.e, there was a lack of host-specificity for most detected ASVs. Further, many frequently found ASVs were assigned to taxa that show a very broad distribution with no strong prior evidence for symbiotic association with animals. We interpret these findings as evidence for a scarcity or lack of resident microbial associates (other than inherited symbionts) in quill mites, or for abundances of these taxa below our detection threshold.

evolutionary biology↗