Background Larvae are usually the only water mite life stage to have parasitic relationships with other organisms. Upon location of a host, larvae pierce host
integument with their chelicerae and feed on
hemolymph until fully engorged or brushed off. It was originally believed that water mite larvae located hosts by accidental contact, but recent studies have found they likely utilize a combination of visual, tactile, and chemical cues. The abundance of water mites in a region, as well as prevalence and intensity of host infection, are impacted by a multitude of environmental and biological factors, and have shown great geographic variation. In some cases, high infection intensities have significantly increased chances of host mortality and reduced
fecundity. Water mite larvae have been considered as a potential
biological control agents, although low natural infection intensities warrant supplementation with other control strategies in order to be effective. Some water mites continue to be parasites in their post-larval stages. These are mainly associated with molluscs, such as
mussels (
Najadicola ingens and many species of
Unionicola) and
snails (two species of
Dockovdia). That said, not all associations with other animals are parasitic; some
Unionicola species merely use other animals as safe, well-oxygenated places to lay eggs and to pass their resting stages (protonymph, deutonymph). The biology and ecology of these specific host-mite interactions have been well studied, likely due to the significant relevance of mosquitoes to human health.
Parathyas barbigera are among the most common mite species found parasitizing mosquitoes, especially those of the genera
Aedes and
Ochlerotatus. Their host range is likely much wider, as studies have detected
P. barbigera parasitizing other dipteran families, such as
Tipulidae (crane flies),
Ptychopteridae (phantom crane flies),
Chloropidae (grass flies), and
Empididae (dagger flies). Once an immature host is located,
Arrenurus larvae loosely bind to their integument, and monitor them until the adult emerges. Host muscle contractions just prior to emergence stimulate mite larvae to move towards the ecdysial opening and attach to the host along intersegmental sutures on their thorax and abdomen. Differences in preferred attachment site between mite species appear to be related to differences in host emergence behavior. Full larval engorgement takes approximately three days, during which they have the potential to significantly impact the health of their host. In laboratory settings, the survival of
Anopheles crucians mosquitoes parasitized by
Arrenurus (Meg.) pseudotenuicollis was found to decrease from 23.32 to 6.25 days between those harboring the least and greatest numbers of attached mites respectively. Under similar conditions, infection intensities equalling 17-32 mites decreased the number of eggs laid by gravid
An. crucians by nearly 100%. High mite loads also significantly decreased the fecundity of field-collected
An. crucians, but to a lesser extent than those infected in the lab. Similar consequences of high
Arrenurus mite infection intensities were observed in other host-mite relationships. For example, Smith and McIver (1984) found that
Arrenurus danbyensis loads of greater than 5 mites decreased the fecundity of
Coquillettidia perturbans females by approximately 3.5 eggs per additional mite. Even though
Arrenurus mite larvae have been considered as potential biocontrol agents, unrealistic numbers would need to be released in order to prove effective on their own. File:Gnat with hydrachnidia - front (aka).jpg|
Gnat infested with freshwater mites File:Cq. perturbans parasitized by A. danbyensis.jpg|
Coquillettidia perturbans parasitized by
Arrenurus danbyensis larvae File:Sympetrum meridionale (1).jpg|
Sympetrum meridionale with water mites parasiting its wings '' damselfly infested with Hydracarina mites == Predation ==