This comprehensive review of host-parasite associations between larval Trombidioidea and its arthropod hosts includes 676 pair-wise (species-species) associations and is based mainly on published records, supplemented with new findings. For 27% of all nominal species assigned to the superfamily (excl. Trombiculidae and Walchiidae), and for 66% of species known from larvae at least one host record has been hitherto provided. Hosts remain unknown for Allotanaupodidae and Yurebillidae. Both generalist and specialist parasites have been recognized within Trombidioidea. However, for the vast majority of species, the fragmentary data on host-parasite associations do not allow differentiation between common and exceptional hosts, apart from general preferences towards the host group. Hitherto recorded arthropod hosts, exploited by trombidioid larvae, are listed. Ecological data relating to measures of host-parasite interactions are summarized. Names of mites and their hosts are verified and updated and the recent affiliation to higher taxa is followed.
New data are provided on larvae of terrestrial Parasitengona mites parasitizing spiders. Larvae of Erythraeidae and Trombidiidae are recorded as parasites of spiders representing five families. Members of Philodromidae and Tetragnathidae (Pachygnatha clercki Sundevall 1823) are reported as hosts of Trombidioidea for the first time. The available information indicates that some Trombidiidae have a narrow host range with affinity to spiders, whereas the Erythraeidae are more opportunistic parasites.
A survey of odonate fauna in Zambia (Central Province, Luano District) resulted in discovery of ectoparasitic larvae of Leptus (L.) chingombensis sp. nov. (Trombidiformes: Parasitengona, Erythraeidae) on four species of dragonflies (Odonata) representing four different families assigned to Zygoptera and Anisoptera. The morphological characteristics of the new species is supported with DNA barcode sequence. Despite some intra-group variation related to relatively large sample, the morphological and genetic consistence confirm the common specific identity of the material. A brief comparison of Leptus spp. hitherto known from the Afrotropic as larvae is given. Supplementary data to the descriptions of Leptus (L.) bicristatus Fain et Elsen, 1987, Leptus (L.) aldonae Haitlinger, 1987 and Leptus (L.) soddagus Haitlinger, 1990, based on examination of type material, are provided. In the case of L. (L.) chingombensis sp. nov., the parasite load reached high, previously not recorded for Odonata–terrestrial Parasitengona association values, attaining at 44 and 49 larvae. Clear topic preferences towards the ventral side of the host’s body were recorded, with an additional tendency to distal parts of synthorax and the ventral depression of the abdomen. We hypothesize that the infestation did not take place synchronously at dragonflies emergence, but consisted in repeated infestation events during the recurrent appearance of dragonflies in the contact microhabitat occupied by Leptus. The very local character of the finding along with the regular appearance of larvae parasitizing dragonflies, obviously favoured by specific habitat conditions, no doubts confirms the non-accidental nature of the phenomenon.
Stylostomes (feeding tubes) of Hirsutiella zachvatkini (Schluger) (Trombiculidae), feeding on bank voles [Myodes glareolus (Schreber)], and of Trombidium holosericeum (L.) (Trombidiidae), feeding on larvae of Stenodemini sp. (Heteroptera, Miridae), were studied by TEM methods and on semi-thin sections. The stylostome of H. zachvatkini is a homogeneous structure of low electron density and without strict margins. It extends within the concave host epidermis, undergoing hyperplasia and hyperkeratosis. TEM does not reveal any obvious stratification in the stylostome walls. The cheliceral movable digits are moved apart by 5-6 µm and tightly applied/adhered to the stylostome substance. A local area beneath the open end of the stylostome canal is not empty but contains a nearly homogeneous substrate, which can pass into the central stylostome canal. The latter is mostly free of contents. In contrast to H. zachvatkini, larvae of T. holosericeum form a root-like stylostome chaotically branching within the clear space underneath the host cuticle free of tissue elements. Tubules of the distal stylostome branches become progressively thinner and disappear blindly. As in H. zachvatkini, the stylostome walls of T. holosericeum are devoid of stratification but show moderate to high electron density. The cheliceral movable digits are moved apart by the same distance, as in H. zachvatkini, and tightly applied to the stylostome substance. The lumen of the central canal is either electron lucent, in the distal portions, or filled with a fine granular or homogeneous substrate of low electron density in the proximal portions forming a type of ampoule. This study shows that Trombiculidae and Trombidiidae share similar initial stages of stylostome formation but the resultant stylostome of each family is distinctly different.
A new genus and species of microtrombidiid mite, Araneothrombium dimalogunovi n. gen. et n. sp. is described based on larvae collected from a juvenile araneid spider in Costa Rica. The genus, tentatively placed in Eutrombidiinae, displays affinity to Verdunella Southcott, 1993 and Spinnitrombium Fain and Jocqué, 1996. This is the first record of Trombidioidea (excl. Trombiculidae s.l.) in Costa Rica.
Cases of co-invasion of various chigger species parasitizing murids and cricetids in various habitats were analysed using morphological and molecular approaches. Here we provide evidence for 25 new cases of co-parasitism of chigger mites on rodent hosts (Myodes glareolus, Apodemus flavicollis, Apodemus agrarius) accounting for 8.6% of all host-parasite associations observed in this study. The results confirm higher incidence of co-parasitism in vertebrate-associated Parasitengona mites compared to arthropod-associated ones. Among factors influencing the occurrence of co-parasitism in Trombiculidae the body constitution and year-round availability of hosts associated with lower host specificity of larvae should be considered.
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