Leptotrombidium myotis (Ewing, 1929)

Myotis View in CoL davidii

In this host species, larvae fed on the outer surface of the ear ( Figure 1, B), not far from the ear base. In this region, the epidermis is thicker than inside the ear and normally consists of

3-5 or more cell layers. Parasitism of larvae on this host species, however, causes a strong inflammatory reaction with abundant cellular and fluid exudate and complete destruction of the epidermis. Erythrocytes leaving the dilated peripheral blood vessels and the infiltrate cells

– leukocytes and lymphocytes – fuse together into the various necrotic masses, which cover the skin ( Figure 5, A-B) displacing the epidermis. Larvae at the final feeding stages tightly immerse into these masses in several rows ( Figure 5, B). As a result, the larvae, in order to reach the dermis, secrete a stylostome, which is slightly longer, up to 200 µm, than that evolving during feeding on P. ognevi inside the ear ( Figure 6, A-B). Nevertheless, there are no significant differences in the stylostome organization between these two host species.

The dark-red eosinophilic cone, poorly expressed, represents the proximal portion of the stylostome ( Figure 6, A). A white to pale-pink substance forms the widest and largest portion of the stylostome ( Figures 5, A, 6, A-B). The distal, narrower portion of the stylostome is dark-blue ( Figure 6, A-B, D). The axial stylostome canal is confined by a narrow rim, which is either completely uncolored or shows a reddish or bluish staining ( Figures 5, A, 6, B, D). The axial canal is around 10 µm in diameter, similarly to the case of P. ognevi , it opens freely into the subjacent tissues ( Figure 6, C-D) and may contain various cellular debris ( Figure 6, B). As in the case of P. ognevi , the stylostomes penetrate into the skin at different angles that makes it impossible to observe the entire stylostome at once. Nevertheless, it may be assumed that the total length of the stylostome may reach 200 µm or more, whereas its maximum width is around 50-70 µm.

The outer borders of the stylostome are quite distinct and do not show an apparent transitional zone between the stylostome substance and the surrounding necrotic cell masses

( Figure 6, A-B). Sometimes, however, a pink rim of a supposedly denser substance may be observed at the stylostome periphery ( Figure 6, C-D). The evident tissue sinus underneath the stylostome is not observed due to a strong cellular infiltration of the inflammation area (see below).

Feeding of L. myotis larvae on the bat M. davidii induces a strong inflammation with predominance of neutrophil leucocytes and mononuclear lymphocytes (macrophages) in the focus of the lesion ( Figure 7, A-C). The inflammatory response is additionally characterized by a dilation of the peripheral capillaries ( Figure 7, A) and strong hemorrhages spreading over a large area in the dermal connective tissue ( Figure 7, B-C). Upon the release of both the necrotic cell masses and the liquid exudate onto the skin surface, they transform into a hardened, scab-like, coagulated mass composed of either tightly packed necrotic cells (Figure

7, B) or only blood plasma ( Figures 5, B, 6, A). In contrast with P. ognevi , skin inflammation of M. davidii does not show the presence of numerous mast cells in the inflammation focus an

50 µm; B ⚶Distal narrower portions of two stylostomes situated at different angles to each other. Scale bar⚶50 µm; C ⚶Nearly perpendicular section of the stylostome in its middle portion surrounded by a thin layer of necrotic tissue. DIC. Scale ⚶ bar 50 µm; D ⚶Situation in the host dermis adjacent to the inflammatory focus indicating the presence of numerous must cells. Scale bar ⚶50 µm. cap ⚶capillary; car ⚶ear cartilage; der⚶dermis; ep⚶epidermis; hl⚶horn layer; mc ⚶mast cell; mac ⚶macrophage; nc ⚶necrotic cells; nl ⚶neutrophil leucocyte; pl ⚶papillary layer;

sin ⚶tissue sinus; st ⚶stylostome; stc ⚶stylostome canal.

ear of the bat Myotis davidii . AzurII-eosin-stained sections. A⚶Strong ulceration of the skin with total degradation of the epidermis in mass feeding of larvae. Note a scab-like substance on the skin surface composed of both destroyed inflammatory cells and erythrocytes. Scale⚶bar 100 µm; B ⚶Ulceration of the skin in mass feeding of larvae. Note enormous masses on the skin surface composed of either fused destroyed inflammatory cells forming a scab-like substance or blood plasma, in which larvae are immersed. Scale bar ⚶100 µm. bp⚶blood plasma; car⚶ ear cartilage; der⚶dermis; ep⚶epidermis; hem⚶hemorrhage; hl ⚶horn layer; nc ⚶necrotic cells; sc ⚶scab-like substance; sin⚶tissue sinus; st ⚶ stylostome.

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Scale bar⚶50 µm. bp⚶blood plasma; car⚶ear cartilage; chb⚶cheliceral blade; der⚶dermis; ec⚶eosinophilic cone; mp ⚶larval mouthparts; nc ⚶necrotic cells; st ⚶stylostome; stc ⚶stylostome canal.

the outer ear surface of the bat Myotis davidii . AzurII-eosin-stained sections. A⚶Dilated capillaries in the dermis surrounded by numerous inflammatory cells adjacent to the damaging focus. Scale bar ⚶50 µm; B ⚶A strong hemorrhage impregnated by leucocytes underneath the hyperplastic epidermis covered by a scab-like substance. Scale bar ⚶50 µm; C ⚶Different inflammatory cells with predominance of neutrophil leucocytes and the hemorrhage in the dermis adjacent to the damaging focus. Scale bar ⚶10 µm; D ⚶Numerous inflammatory cells in the affected area of dermis with single mast cells. Scale bar⚶10 µm. cap ⚶capillaries; car ⚶ear cartilage; der⚶dermis; ep⚶epidermis; fb⚶fibroblast; hem⚶ hemorrhage; ic ⚶inflammatory cells; lym ⚶lymphocyte; mac ⚶macrophage; mc ⚶mast cell; nl ⚶neutrophil leucocytes; sc ⚶scab-like association

of necrotic cells.

( Figure 7, D). Eosinophil and basophil leukocytes were not observed with certainty in either host species.