A transitional fossil mite (Astigmata: Levantoglyphidae fam. n.) from the early Cretaceous suggests gradual evolution of phoresy-related metamorphosis.

Metamorphosis is a key innovation allowing the same species to inhabit different environments and accomplish different functions, leading to evolutionary success in many animal groups. Astigmata is a megadiverse lineage of mites that expanded into a great number of habitats via associations with invertebrate and vertebrate hosts (human associates include stored food mites, house dust mites, and scabies). The evolutionary success of Astigmata is linked to phoresy-related metamorphosis, namely the origin of the heteromorphic deutonymph, which is highly specialized for phoresy (dispersal on hosts). The origin of this instar is enigmatic since it is morphologically divergent and no intermediate forms are known. Here we describe the heteromorphic deutonymph of Levantoglyphus sidorchukae n. gen. and sp. (Levantoglyphidae fam. n.) from early Cretaceous amber of Lebanon (129 Ma), which displays a transitional morphology. It is similar to extant phoretic deutonymphs in its modifications for phoresy but has the masticatory system and other parts of the gnathosoma well-developed. These aspects point to a gradual evolution of the astigmatid heteromorphic morphology and metamorphosis. The presence of well-developed presumably host-seeking sensory elements on the gnathosoma suggests that the deutonymph was not feeding either during phoretic or pre- or postphoretic periods.

Review of the genera Berlesia Canestrini, 1884, and Katydiseius Fain amp; Lukoschus, 1983, the subfamily Katydiseiinae Fain amp; Lukoschus, 1983, and their family group relationships (Acari: Mesostigmata: Gamasina), with description of three new species parasitic on gryllacridid crickets (Orthoptera).

The gamasine genus Berlesia Canestrini, 1884, is revived and further diagnosed, based on descriptions of adult females, males and nymphs of three new species (B. hospitabilis sp. nov., B. multisetosa sp. nov., B. vorontsovi sp. nov.) ectoparasitic on raspy crickets of three genera of Gryllacrididae (Ensifera) from Australia and the Philippines. A tight sister relationship of Berlesia with the monobasic genus Katydiseius Fain Lukoschus, 1983, known only from a pseudophylline katydid in Malaysia, is proposed. The subfamily Katydiseiinae Fain Lukoschus, 1983 (previously included in the family Otopheidomenidae in the superfamily Phytoseioidea) is redefined to include only those two genera, and moved to the dermanyssoid family Laelapidae, while its previously other monobasic genus, Eickwortius Zhang, 1995, is retained tentatively in the family Otopheidomenidae. Among other taxa relevant to Katydiseiinae reviewed here, Berlesia cultrigera Berlese, 1910a is transferred to the genus Orthopteroseius Mo, 1996, at present Otopheidomenidae, as Orthopteroseius cultrigerum (Berlese) comb. nov., and Berlesia nuda Berlese, 1910b is transferred to the genus Prasadiseius Wainstein, 1972, at present Otopheidomenidae, as Prasadiseius nudum (Berlese) comb. nov. A key to the two genera and five species recognized as belonging in Katydiseiinae is presented. Notable morphological traits of Berlesia, including only deutonymphs equipped with well-developed claws and males with dimorphically more elongated salivary stylets, are discussed. The one known life cycle of a species of Berlesia, B. hospitabilis sp. nov., includes protonymphipary, followed by a fully functioning deutonymph, and male copulation with pharate females-traits, rarely or not known among gamasine mite associates of invertebrates. The possible significance of elongate spermatodactyls and male reduced feeding are explored.

Active postlarval forms of plume-footed Eatoniana (Trombidiformes: Parasitengona, Erythraeidae) in the Eocene Baltic amber.

The discovery of active postlarval forms (deutonymph and adult) of erythraeid Eatoniana in Eocene Baltic amber is associated with the first description of named fossil species assigned to that genus. Species of Eatoniana, having the plume-like setae on terminal segments of leg IV, reveal the high consistency of characters, confirmed both for extinct and extant members of the genus. The main difference between Eatoniana crinita sp. nov. and other "plume-footed" congeners is the shape of modified setae arising at genu and tibia IV.

A new species of Podapolipus (Acari: Heterostigmata: Podapolipidae) from an Australian gryllacridid cricket (Orthoptera), with keys to orthopteran-associated species of the genus.

A new species of the ectoparasitic mite genus Podapolipus Rovelli Grassi, 1888 from a recently described species of the raspy cricket genus Chauliogryllacris Rentz, in Rentz and John,1990 (Orthoptera: Gryllacrididae) is described. The main distinctions of Podapolipus gryllacridi n. sp. from its described congeners from orthopterans are the larval female and adult male having all dorsal and ventral idiosomatic setae, except the greatly elongated pair of scapular setae (and the caudal setae of the larval female), reduced to the size of microsetae; the larval female having separate tergites C and D; the male having an entire prodorsal shield, with apex of the aedeagus between bases of setae v1; and the adult female having smooth dorsal shields. Novel biological features of this parasite include its adult females' dwelling in the hollow sternal apodemes of their host, and its larval females using their host's other parasite, a gamasine mite, as phoretic and facultative hyperparasitic hosts. Keys are presented for the larval females and adult males of Podapolipus species associated with orthopterans. Problems with the generic concept of Podapolipus and closely related genera are reviewed. This is the first record of a podapolipid associated with orthopterans of the family Gryllacrididae.

A Carboniferous Mite on an Insect Reveals the Antiquity of an Inconspicuous Interaction.

Symbiosis [1], understood as prolonged interspecific association, is as ancient as the eukaryotic cell [2, 3]. A variety of such associations have been reported in the continental fossil record, albeit sporadically. As for mites, which as a group have been present since the Devonian (ca. 390 mya) [4, 5] and are involved in a tremendous variety of modern-day symbioses, reported associations are limited to a few amber-preserved cases [6-11], with the earliest instance in the Cretaceous (ca. 85 mya) [11]. As a consequence, the antiquity and origin of associations involving small-sized mites and larger animals are poorly understood. Here we report, recovered from the Carboniferous Xiaheyan locality (ca. 320 mya), an oribatid mite located on the thorax of an extinct relative of grasshoppers, crickets, and katydids [12]. The mite was investigated using several methods, including phase-contrast tomography. The detailed morphological data allowed the placement of the mite in a new family within Mixonomata, whose fossil record is thus extended by ca. 250 Ma. Specimen and abundance distribution data derived from the fossil insect sample indicate that specimens from the corresponding excavation site were buried rapidly and were sub-autochthonous, indicating a syn vivo association. Moreover, the mite is located in a sequestered position on the insect. The observed interaction best fits the definition for phoresy, in which the benefit is transport and protection for the mite. This discovery demonstrates that this association, a trait shared by representatives of the most speciose mite taxa, arose very early during mite evolution.