Attachment and Feeding Devices of Water‐Mite Larvae [Arrenurus spp.) Parasitic on Damselflies (Odonata, Zygoptera)

Abstract

Water‐mite larvae of the subgenus Arrenurus (Acari, Hydrachnellae) act as habitual ectoparasites on zygopteran imagines, mostly attached to the soft membranous cuticle. The powerful larval pedipalp claws grasp the cuticle and the distal sabre‐like cheliceral segments tear it, thus obtaining the host's tissue fluids. The chelicerae and palps co‐operate to anchor the larva. The attached larva soon produces—in the host's subcuticular epidermis layer, and separated from the haemocoele by the thin sheet of subepidermal connective tissue—an elongated pouch, the stylostome, consisting of an acellular gelatinous substance, apparently secreted by the larva. Presumably, interaction with components in the host's tissue fluids solidifies the stylostome, which becomes firmly fixed to the host's body wall. The stylostome is thought to lengthen by repeated alternation between the suction of tissue fluids from the host and secretion of fresh soft substance forming additional stylostome segments. The resilient stylostome develops in a cleft between the host's cuticle and the subepidermal connective tissue in connection with partial decomposition of the host's epidermis, probably caused by cytotoxins leaking from the stylostome. In attempts to wall off the wound and thus to avoid influx of foreign substances, the host lays down a melanin sleeve around the stylostome at the perforation site. Lodgement of the functional stylostome separated from the haemocoele within the host's tissues might explain why the newly‐formed stylostome seems immune from cellular host reactions. However, cellular encapsulation and melanization appear to happen to outworn, non‐active stylostomes.

Comparative morphology and ultrastructure of the mouthparts in unfed larvae of Platytrombidium fasciatum and Camerotrombidium pexatum (Acariformes: Microtrombidiidae)

“…In trombiculid larvae, on the contrary, the apical parts of the hypostome show only temporary structures resembling a sucker that is apparently formed during feeding owing to a turning back of the apical portions of the lateral lips (Shatrov 2000). A somewhat intermediate position may be seen in larvae of some water mite groups (Davids 1973;Å bro 1979). In adults of Parasitengona, the formation of sucker-like structures is highly characteristic of many groups of water mites (Böttger 1969;Zhavoronkova 1990Zhavoronkova , 1992Alberti and Coons 1999) as well as of erythraeids (Witte 1978(Witte , 1991.…”

<p class="Body">Erythraeid larvae parasitizing dragonflies in Zambia—description of Leptus (Leptus) chingombensis sp. nov. with data on biology and ecology of host-parasite interactions

“…Water mite larvae enter the parasitic phase on newly emerged dragonlflies (e.g. Åbro 1979;Rolff 2000), which is obviously facilitated by cohesion of microhabitats occupied by these mites and serving also for dragonfly emergence.…”

Parasites Mediate Condition-Dependent Sexual Selection for Local Adaptation in a Natural Insect Population

“…The generation time of I. elegans is one year in the northern part of its range in Europe, with adults emerging between late May and early August, while the larvae overwinter in an aquatic stage [39]. During the aquatic stage, water mites of the genus Arrenurus attach to the larvae and remain in a phoretic stage until adults emerge, when they attach to the cuticle on the ventral side and pierce it to feed on the host body fluids [43][44][45]. Water mites are easily detected visually, and have been reported to affect agility and flight performance in other species of Coenagrion and Enallagma damselflies [44].…”

“…Mating success is therefore highly likely to be condition-dependent, given intense male-male scramble competition in damselflies [41,42]. Natural populations of pond damselflies are often infected by ectoparasitic water mites of the genus Arrenurus [43][44][45]. High parasite load can affect agility and flight performance, which is necessary for mate search and competition for mates [44].…”