Chitinisation of Parasites in Mosquitos

Abstract

Various instances of the formation of a chitinous capsule around parasites in mosquitos have been described in literature. Worms as well as Protozoa, Hyphomycetes and bacilli have been seen encapsuled in this way.

Stylostome formation in trombiculid mites (Acariformes: Trombiculidae)

“…Larvae of other groups of Parasitengona that parasitize insects, such as water mites (phalanx Hydrachnidia) and trombidiids (superfamily Trombidioidea), also form a type of stylostome (Flögel 1876;Blunck 1923;Marshall and Staley 1929;Brug 1932;Steffan 1967;Å bro 1979, 1984Redmond and Hochberg 1981;Smith 2003;Mohamed and Hogg 2004), which is typically up to 1 mm long (Marshall and Staley 1929) and may be branched (Flögel 1876;Steffan 1967;Å bro 1979, 1984Smith 2003;Mohamed and Hogg 2004). However, in contrast to trombiculids, stylostomes of water-and trombidiid mite larvae are considered to be mostly formed of chitin (Flögel 1876;Blunck 1923;Marshall and Staley 1929;Brug 1932) that is thought to manifest the defense reaction of the insect host to minimize the harmful action of the damage agent and isolate the toxic and foreign substances (Brug 1932).…”

“…However, in contrast to trombiculids, stylostomes of water-and trombidiid mite larvae are considered to be mostly formed of chitin (Flögel 1876;Blunck 1923;Marshall and Staley 1929;Brug 1932) that is thought to manifest the defense reaction of the insect host to minimize the harmful action of the damage agent and isolate the toxic and foreign substances (Brug 1932). At the same time, the mechanism of the attachment of water mite's larvae to their hosts is nearly identical to that of trombiculid larvae (Steffan 1967;Å bro 1979).…”

“…At the same time, the mechanism of the attachment of water mite's larvae to their hosts is nearly identical to that of trombiculid larvae (Steffan 1967;Å bro 1979). The mode of the stylostome formation at the ends of its branches due to the action of small drops (Flögel 1876) leaves the question about the origin of stylostome evolved in the insect hosts, i.e., whether it is from the host reaction or from the parasite saliva secretion,-to be still mostly open even if the stylostome is predominantly composed of chitin (Blunck 1923;Marshall and Staley 1929;Brug 1932). It was also shown that in Arrenurus larvae, the stylostome is a blindly ended tube with a bulbous termination at the distal end situated freely in the haemocoel of the host (dragonflies) and bearing no any pores on its sculptured surface through the length of stylostome (based on SEM, Redmond and Hochberg 1981).…”

Biology of Dirofilaria immitis (Leidy, 1850) (Nematoda: Onchocercidae) and Aedes trivittatus (Coquillett, 1902) (Diptera: Culicidae) in Central Iowa

“…Encapsulation was first thought to occur only around dead para sites (Brug 1932;Hu 1939a). Later work by Hu (1939b), Highby (1943), and Kartman (1953a), however, demonstrated encapsulation of living juveniles in several mosquito species.…”

“…Although numerous reports of encapsulation or "chitinisation" of filarial juveniles by mosquito hosts have been published (Sambon 1902;Brug 1932, Yen 1938Hu 1939a,b;Highby 1943;Newton et al 1945;Kartman 1953a,b;Lavoipierre 1958;Esslinger 1962;Intermill 1973), such studies have not determined what effect, if any, this reaction has on the capability of a mosquito to function as a vector.…”