A gallery of the key characters to ease identification of Dermanyssus gallinae (Acari: Gamasida: Dermanyssidae) and allow differentiation from Ornithonyssus sylviarum (Acari: Gamasida: Macronyssidae)

Abstract

Background: Dermanyssus gallinae (poultry red mite) is a major threat for the poultry industry and is of significant interest for public health. Identification of D. gallinae can be difficult for scientists not familiar with mite morphology and terminology especially when trying to use identification keys. Moreover, this species may easily be confused with another dermanyssoid mite, Ornithonyssus sylviarum (northern fowl mite), which often shares the same hosts and environment.

Methods: Specimens of D. gallinae were collected at poultry farms in the Puglia and performed for light and scanning electron microscopy observations, identification and micrographs. Moreover specimens of O. sylviarum were collected separately macerated and mounted on slides for light microscopy observations, identification and pictures.

Results: The micrographs used in this study, based on LM and SEM observations, highlight the following important identifying characters of D. gallinae: the prominent shoulders of the dorsal shield and the jagged edges of the shield reticulations, the position of setae j1, s1 and the epigynal pores, and the presence on tibia IV pl of one seta. Additional micrographs highlighting the shape of the dorsal (abruptly narrowed posteriorly) and epigynal (narrowly rounded posteriorly) shields and the chelicera (elongate, with distinct digits) of O. sylviarum enable its differentiation from D.gallinae.

Conclusion: The photographic support provided here (both LM and SEM pictures) can be considered a practical tool for scientists who are not well acquainted with the morphology of D.gallinae, and who are involved with classical and molecular systematics, veterinary and human health aspects of poultry red mites.

Figure 1

Dermanyssus gallinaefemales.(A) SEM image: dorsal overview showing the idiosoma broadly rounded posteriorly, the single dorsal shield with prominent shoulder (arrows) and the truncate posterior margin (arrowhead). (B) LM image of the dorsal shield (outline traced), chaetotaxy according to Moss [24]. (C) LM picture of the anterior region of the body with the evident and elongate second cheliceral articles, far exceeding the basal segment in length (arrowheads). Abbr: bs, basal segment of chelicerae; DS, dorsal shield; LI-LIV, leg I, II, III, IV; Pa, pedipalp. Scale bar: 100 μm A, C; 50 μm B.

Figure 2

Dermanyssus gallinaefemales.(A) SEM image: detail of the stylet-like second cheliceral article (arrow). (B) LM: detail of the wider than long sternal shield, bearing 2 pairs of sternal setae (arrows). (C) LM: detail of the genitoventral shield with 1 pair of setae (arrows) and 1 pair of epigynal pores (arrowheads). ((D) LM: overview of the ventral side. Note the genitoventral (epigynal) shield broadly rounded posteriorly. (E) LM: detail of the anal shield with three anal setae (arrows). Abbr: ao, anal opening; as, anal shield; CxII, coxa II; gs, genitoventral shield; LI-IV, leg I-IV; Pa, pedipalp. Scale bar: 10 μm A; 50 μm B, C, E; 100 μm D.

Figure 3

Dermanyssus gallinaefemales: dorsal view showing the dorsal shield chaetotaxy used in identification of the species.(A) LM (B), (C) SEM pictures. According to the key, seta j3 on the dorsal shield is missing (arrow point to the approximate position where this seta should be present) while j1 and s1 are located on the dorsal shield. Dorsal chaetotaxy according to Moss [24]. Scale bar: 50 μm A; 100 μm B; 10 μm C.

Figure 4

Dermanyssus gallinaefemales: leg chaetotaxy LM.(A) tibia I with 2 anterodorsal and 2 posterodorsal setae. (B), enlargement of (A). (C) tibia II with 1 anterolateral seta. (D) tibia III and tibia IV with 1 anterolateral seta. (E) genu IV with 2 anterodorsal setae and tibia IV with 2 posterodorsal. Abbr.: ad, anterodorsal; al, anterolateral; Cx, coxa; Fe, femur; Ge, genu; LI-IV, leg I-IV; Pa, pedipalp; pd, posterodorsal; Ta, tarsus; Ti, tibia; Tr, trochanter. Scale bar: 50 μm A, B, C, E; 100 μm D.

Figure 5

Dermanyssus gallinaefemales. Leg IV chaetotaxy. (A), (B), LM, overview of the leg IV (A) and detail of the tibia with 1 posterolateral seta (B). (C) SEM picture showing the location of the setae on genu and tibia IV. Abbr: ad, anterodorsal; Cx, coxa; Fe, femur; Ge, genu; LIII-IV, leg III-IV; pd, posterodorsal; pl, posterolateral seta; Ta, tarsus; Ti, tibia; Tr, trochanter. Scale bar. 50 μm A, B; 40 μm C.

Figure 6

Dermanyssus gallinaefemales: detail of the dorsal shield reticulation with evident jagged edges.(A) LM, (B) SEM pictures. Scale bar: 50 μm A; 10 μm B.

Figure 7

Ornithonyssus silviarum female: LM. (A) dorsal view with a single dorsal shield narrowing posteriorly. (B) ventral view with the genitoventral (epigynal) shield attenuate or narrowly rounded posteriorly. (C) detail of the elongated chelicerae with well developed and distinct fixed and movable digit. Abbr: as, anal shield; Ch, chelicera, DS, dorsal shield, fd, fixed digit; gs, genitoventral shield; LI, leg I; md, movable digit; Pa, pedipalp; st, sternal shield. Scale bar: 50 μm.

Figure 8

Dermanyssus gallinae: overview of the different stages.(A) SEM, larva ventral view: it is evident that there are only three pairs of legs with little sclerotization and without indication of external genitalia; (B), (C) SEM: ventral view of proto and deutonymph respectively: epigynal shield reduced compared to the female; (D) SEM ventral view of female with the genitoventral (epigynal) shield completely developed; (E) SEM, (F) LM, ventral view of the male showing the holoventral shield and a small genital opening set in a presternal position (F and inset). Abbr.: ao, anal opening; as, anal shield; es, epigynal shield; gs, genitoventral shield; go, genital opening; hs, holoventral shield; LI-IV, leg I-IV; Tr, tritosternum. Scale bar: 100 μm A-D, F and inset; 20 μm E.