Plecotus ognevi, Kishida, 1927

Plecotus ognevi View in CoL

In the case of P. ognevi , larvae feed inside the ear ( Figure 1, C). Normally, the epidermis in this location is thin, containing 2-3 cell layers and covered by a relatively thin horn layer (stratum corneum) ( Figure 3, A). In the place where the larvae attach, the epidermis undergoes hyperplasia and becomes much thicker, up to 100-150 µm or more ( Figure 3, B-C). Nevertheless,

the developing stylostomes easily penetrate the epidermis opening by their distal ends to the connective tissue layer of dermis ( Figures 3, B-C, 4, A, C). The developed stylostomes lie at different angles to the epidermal surface, which makes it impossible to observe the entire stylostome, even in sections perpendicular to the surface of the epidermis ( Figures 3, A-C, 4, A-C). In any case, an eosinophilic zone with dark-red coloration, into which the cheliceral movable digits are immersed, represents the proximal and initial portion of the stylostome ( Figure 3, B-C). This stylostome portion apparently corresponds to the eosinophilic cone – the proximal part of any stylostome studied so far (e.g. Shatrov 2009). Typically, the lateral sides of the eosinophilic cone penetrate under the upper squamae of the stratum corneum. Below the eosinophilic cone, the stylostome slightly widens and loses coloration ( Figures 3, B-C, 4, A, C).

In its distal portion, the stylostome become again narrower and acquires a dark-blue staining ( Figures 3, B, 4, A-B). The stylostome canal is regularly round in near-transverse sections, may.

Note that the stylostome of the still-attached, nearly fully-fed larva shows only its proximal portion restricted within the epidermis. Scale bar ⚶50 µm; C ⚶Nearly transverse section of a developed stylostome at the level of its middle portion and a possibly young stylostome with moderately developed eosinophilic cone, into which the cheliceral movable digits are cemented. Note the empty axial canal of the developed stylostome. Scale bar⚶50 µm. cap ⚶capillary; car ⚶ear cartilage; chb⚶cheliceral blades; der⚶dermis; ec⚶eosinophil cone; ep ⚶epidermis; hl⚶ horn layer; lar ⚶larva; mp ⚶mouthparts of larva; st ⚶stylostome; stc ⚶stylostome canal.

a contain cell debris of the host and opens freely into the subjacent host tissues ( Figures 3, B-C,

4, A-B). Erythrocytes were not observed in the stylostome canal. Externally, a thin layer of necrotic host cells surrounds the stylostome ( Figures 3, C, 4, A, C).

Examination of sections using differential-interference contrast (DIC) shows that the hyaline-like substance of the stylostome exhibits a gel-like consistency due to crumpled traces of sections ( Figure 4, C). In response to the parasite feeding, the host develops a moderate inflammatory reaction with edema of the connective tissue layer, where neutrophil leucocytes, macrophages and mast cells are present ( Figure 4, D). Other lymphocyte types are poorly distinguished. The peripheral blood vessels are dilated ( Figure 4, D). Beneath the developed stylostome, a particular tissue sinus may be observed, in which the connective tissue fibers are mostly dissolved and a certain number of destroyed and intact infiltrating cells may be present ( Figure 4, A-C). However, this tissue sinus is much lesser expressed than in infestations with many other trombiculid larvae (e.g. Shatrov 2009).