Order Trombidiformes Reuter, 1909. In: Zhang, Z.-Q. (Ed.) Animal biodiversity: An outline of higher-level classification and survey of taxonomic richness

Abstract

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A new fossil mite from French Cretaceous amber (Acari: Heterostigmata: Nasutiacaroidea superfam. nov.), testing evolutionary concepts within the Eleutherengona (Acariformes)

“…The constitution of Eleutherengona, as presented by Lindquist et al (2009) and repeated by Zhang et al (2011), rests on mostly reductive, somewhat tenuous morphological distinctions. In contrast with members of the supercohorts (or infraorders) Eupodides and Labidostomatides, basal eleutherengones have the distinctive thumb-claw process thought to be a basally derivative attribute of the supercohort Anystides and retained in the Parasitengona and Eleutherengona.…”

“…In contrast, other than not retaining a palptibial claw, Nasutiacarus perplexus retains a clearly more plesiomorphic palpal construction, with trochanter, femur, genu, and at most partially consolidated tibia and tarsus. On the other hand, the most early derived extant taxa (Tarsocheylidae, Heterocheylidae, Dolichocybidae) retain rudiments of a palpal 'thumb-claw process', shared with members of the sister cohort (hyporder) Raphignathina as a more basal heritage of the supercohorts (infraorders) Eleutherengona and Anystina (sensu Walter et al 2009;Zhang et al 2011). In most of these mites, an enlarged dorsal spine-or claw-like seta of a relatively large tibia is situated above the elements (including a solenidion) of a smaller, tarsal segment or thumb, displaced somewhat ventrodistally, such that the claw is usually terminal on the palp (Alberti & Coons 1999;Walter et al 2009).…”

“…Legs: v, tarsal Diagnosis. Adult male with character states of the group Heterostigmata as described by Lindquist (1976) (subsequently ranked as cohort by Walter et al 2009, and as hyporder by Zhang et al 2011), and to some extent of the unranked subgroup Tarsonemina sensu Lindquist (1976), but restricted and augmented as follows: Well-sclerotized, fusiform, with prominent, conical but dorsoventrally flattened, prognathous gnathosoma. Gnathosoma with incompletely formed cheliceral stylophore adherent to, but not fully consolidated with, infracapitulum to form a capsule; cheliceral bases separate ventrally, fixed digit remnants fused; strongly narrowed gnathosomatic apex with a small hyaline flange or adhesive structure, with two pairs of minute setae, dorsal and ventral, proximal to flange; one pair of infracapitular setae present posterior to level of palp trochanters; movable cheliceral digits styliform, deeply retractable, attached to wellformed levers operating in dorsoventral plane; pharynx entire, not subdivided into separate muscular packets; palpi well developed, linear, five-segmented, freely projecting beyond gnathosomatic apex; all palptibial phaneres setiform.…”

“…There are four published records of fossil Heterostigmata: Protophenax kotejii Magowski, 1994 (Acarophenacidae) from the Late Cretaceous (Santonian) resin of Taimyr Peninsula (Russia), Protoresinacarus brevipedis Khaustov & Poinar, 2010 (Resinacaridae) from mid Cretaceous (Early Cenomanian) Burmese amber, Pyemotes primus Khaustov & Perkovsky, 2010 (Pyemotidae) from Eocene Rovno (Ukraine) amber, and an unassigned member of Pygmephoroidea from Eocene Baltic amber (Magowski 1995). Curiously, the three families listed first are members of a single superfamily, Pyemotoidea (Lindquist 1986;Walter et al 2009;Zhang et al 2011), to which the other superfamily is rather closely related (see Lindquist 1986). Furthermore, all Pyemotoidea and many Pygmephoroidea are insect associates (parasites, parasitoids or otherwise symbionts), members of an arguably derived clade within Tarsonemina, which in itself is a major assemblage of heterostigmatic mites with multiple apomorphic features, therefore regarded as giving rise to the most highly derived groups of Heterostigmata (Lindquist 1986).…”

Water boatman survival and fecundity are related to ectoparasitism and salinity stress

“…One interesting model system for studying interactions between environmental stress and parasitism is water mites infecting aquatic insects. Water mites or Hydrachnidia are the most diversified group of the Acari in freshwater ecosystems, with more than 300 genera and 6000 species [11, 12]. They occur in almost all fresh and brackish aquatic environments around the world where they can reach densities exceeding 2000 specimens per square meter [13].…”