Abstract
The captive environment of invertebrates in zoological collections is such that it may promote unusually heavy ectoparasitic mite burdens. The impact of mites on their hosts is poorly understood. Androlaleaps shaeferi, a mite found on Madagascar hissing roaches (Gromphadorhina portentosa) feeds on saliva and food debris and maybe other secretions.4,5,6 Available data suggest this mite does not impact the health of the roaches, but studies correlating mite burden and roach health or performance have not been conducted. African giant millipedes (Archistreptospirus gigas) often harbor mites in the genus Julolaelaps.3 The exact relationship between mites and millipedes has not been studied scientifically yet empirically these mites are labeled as commensals, or even beneficial to the host. This assumption has seldom been challenged. Julolaelaps mites are conspicuous, fast moving, and their presence is often objectionable to owners or caretakers. About half the giant millipedes collected from the wild were free of mites, indicating they are at least not essential to the host.3 Mites were collected from African giant millipedes at the Bronx Zoo and identified as two different species of Julolaelaps. Using magnification, some mites were seen with their chelicerae seemingly inserted at the seam between tergites, raising questions as to their feeding habits. Histologically, millipede mites are sometimes found embedded deep beneath the cuticle, again suggesting mites may cause some morbidity. Riccardoella mites spend their whole life on slugs or snails, feed on hemolymph, and are transmitted by direct contact between snails, but they can also travel along slime trails to find a new host.2 Snails are often raised in densities that optimize parasite transmission, exacerbate mite burdens, and make treatment difficult. Malayan giant black stag beetles (Dorcus titanus) at the Bronx zoo were partly white from dense aggregations of Canestrinia sp. mites. These mites are not known to feed on hemolymph, but often multiply to become a nuisance to the beetle.1 Affected beetles buried themselves in dirt, maybe in an attempt to escape the mites. Mites that occur on beetles and other insects, on spiders, scorpions, and on centipedes are usually believed to be detrimental to the host, and treatment is seemingly recommended again based on anecdotal information. Phoretic mites are sometimes seen, mostly on wild-caught arthropods, but are unlikely to become a problem if the vivarium is regularly cleaned, and the substrate periodically changed. There is a need for a better understanding of the relationships between invertebrates and the mites they harbor, and on the impact of captivity upon that relationship. This requires that we be more proactive in getting mites identified and spend more time observing affected arthropods. Until such information is gathered, the presence of mites on invertebrates in zoological collections should be examined objectively by the clinician, and a decision to treat or not be made based on each individual case. The use of predatory mites, now commercially available, has shown promise and is a significant improvement over alcohol swabs, flour “shake and bake” and other labor-intensive, potentially harmful treatment options. As the use of those predatory mites becomes more widespread, an efficacious protocol for mite treatment in invertebrates is likely to emerge.
Literature Cited
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