Philopterus coriaceus, Gustafsson & Najer & Zou & Bush, 2022

Gustafsson, Daniel R., Najer, Tomas, Zou, Fasheng & Bush, Sarah E., 2022, New species of Philopterus Nitzsch, 1818 (Ischnocera: Philopteridae), with notes on Cypseloecus Conci, 1941, European Journal of Taxonomy 790 (1), pp. 1-52 : 33-38

Philopterus coriaceus sp. nov.

urn:lsid:zoobank.org:act:8D76847E-153C-4061-B476-420FEED3C483

Figs 37–42 ; Tables 2–4 , 6

Diagnosis

Finding the closest known relative of Philopterus coriaceus sp. nov. is difficult. This species is set apart from almost all other known Philopterus complex species by the presence of a pair of setae on the anterior margin of female tergopleurite IX+X. To our knowledge, this seta is only present in some species of Mayriphilopterus Mey, 2004. All of the species in this genus are Neotropical, but none of them occur on passeriforms.

However, P. coriaceus sp. nov. does not key to Mayriphilopterus in the key of Mey (2004), and can be separated from this genus by the following characters: coni present in P. coriaceus sp. nov. ( Fig. 39 ), but absent (possibly highly reduced) in Mayriphilopterus; hyaline margin with thickened setae in Mayriphilopterus, but without such setae in P. coriaceus sp. nov. ( Fig. 39 ); area between subgenital plate and vulval margin with a large number of small setae in Mayriphilopterus, but without such setae in P. coriaceus sp. nov. ( Fig. 42 ). It thus seems unlikely that P. coriaceus sp. nov. is closely related to Mayriphilopterus.

Only two species of Philopterus are previously known from icterid hosts: Philopterus quiscali Osborn, 1896 (ex Quiscalus quiscula (Linnaeus, 1758)) and Philopterus agelaii Osborn, 1896 (ex Agelaius phoeniceus (Linnaeus, 1766)). No detailed descriptions or illustrations of either of these species have been published, and both species are in need of redescription.

From Osborn’s descriptions of both species, and the illustration of P. quiscali ( P. agelaii not illustrated in Osborn 1896, but said to be similar to P. quiscali ), these two species can be separated from P. coriaceus sp. nov. by the following characters: preantennal head proportionately wider in P. quiscali than in P. coriaceus sp. nov. ( Fig. 39 ); dorsal anterior plate with broad posterior extension in P. quiscali , but with slender posterior extension in P. coriaceus sp. nov. ( Fig. 39 ); tergopleurites of P. quiscali extending only about halfway to midline of abdomen on each side, whereas those of P. coriaceus sp. nov. are much longer in both sexes, almost reaching midline in more posterior segments in male. Chaetotaxy is not given for either P. quiscali or P. agelaii , but Osborn’s illustration of P. quiscali has only apertures for 6 setae illustrated on each of the tergopleurites of segment II. In P. coriaceus sp. nov. there are 8 setae placed on each of the tergopleurites of this segment in both sexes ( Figs 37–38 ); however, the number of setae situated median to the tergopleurites in P. quiscali is unknown. In specimens of P. agelaii deposited at the NHMUK, there are 7–8 setae on each side in females and 8–9 setae on each side in males, which overlap with the number of setae in P. coriaceus sp. nov.; one seta on each side is situated median to the tergopleurites in both sexes of the NHMUK specimens of P. agelaii . In addition, Osborn (1896: 220) mentioned “brown spots on each segment back to the eighth [= IX+X]; those on the sixth segment [= VII] form the outer portion of the genital patch.” Osborn (1896) further stated that the “lateral spots” of P. agelaii are “small, rather elongated, oblique”; it is not clear whether he was describing the male or the female, but his illustration is of a male. We interpret these spots as the overlap of the median section of the tergopleurites with either the lateral accessory sternal plates (in segments II–VI) or the subgenital plate (segments VII–XI+X). This overlap often shows as darker brown spots than the rest of the tergopleurite. This suggests that the central sternal plates are absent on segments II–VI in P. quiscali and P. agelaii , whereas these are present on male segments V–VII in P. coriaceus sp. nov. ( Fig. 37 ).

Etymology

The specific name is derived from Latin ‘ coriaceo ’ for ‘leather-like’, referring to the colour and texture of the abdominal plates.

Material examined

Holotype PERU • ♂ (marked with black dot on slide); Hacienda Amazonia, near Atalaya, Department of Madre de Dios; 4 Nov. 1985; S.M. Lanyon leg.; ex Molothrus oryzivorus oryzivorus (as Scaphidura oryzivora); “ 1032 ”; NHMUK.

Paratypes PERU • 1 ♂, 2 ♀♀; same collection data as for holotype; NHMUK .

Type host

Molothrus oryzivorus oryzivorus (Gmelin, 1788) – giant cowbird (Icteridae).

Description

Head shape and chaetotaxy as in Fig. 39 , preantennal area broad. Hyaline margin broad, shallowly concave medianly, extending laterally slightly beyond marginal carina. Dorsal preantennal plate narrowing gently posteriorly, ads situated in transparent section. Ventral anterior plate roughly trapezoidal, anterior margin concave. Coni long, broad, pointed posteriorly. Gular plate large, irregular. Thoracic and abdominal segments as in Figs 37–38 . Measurements as in Table 6 .

Male

Thoracic and abdominal chaetotaxy as in Fig. 37 and Tables 2–4 . Tergopleurite VIII interrupted medianly. Central sternal plates absent from segments II–IV, present but fragmented on segment V, and present on segment VI. Lateral accessory plates present on segments II–IV, present and fused to central sternal plates on segments V–VI. Subgenital plate large, lateral incisions shallow or absent, lateral accessory plate of segment IX+X fused to subgenital plate. Basal apodeme long, rectangular ( Figs 40–41 ). Mesosomal thickening about as broad as long, laterally pointed on dorsal side, with roughly crescentshaped sclerotization in anterior end and triangular sclerotization centrally; 3 microsetae on each side of mesosome. Gonopore bilobed anteriorly, distal part as in Fig. 41 . Parameres short, stocky ( Figs 40–41 ); pst1–2 as in Figs 40–41 .

Female

Thoracic and abdominal chaetotaxy as in Fig. 38 and Tables 2–4 . Tergopleurites VI–IX+X with slight to extensive reticulation median to spiracle openings. Central sternal plates absent on segments II–VI. Lateral accessory plates present on segments II–VI. Subgenital plate as in Fig. 42 , reticulation prominent. Lateral sclerotizations of vulval area extended to vulval margin, chaetotaxy as in Fig. 42 and Table 3 ; short vulval setae thorn-like. Subvulval plates broad, roughly triangular, each with small postero-median projection.

Remarks

Philopterus coriaceus sp. nov. is only the third species of Philopterus described from icterid hosts. This is surprising, as hosts in this family have been examined extensively, and many other species of ischnoceran lice are known from icterid hosts (e.g., Cicchino 1990, 2004; Cicchino & Castro 1996; Valim & Palma 2012). However, two previous studies have found comparatively low infestation rates of Philopterus on icterid hosts: 11.5% of examined red-winged blackbirds, Agelaius phoeniceus (Linnaeus, 1766) (Spory 1965) and 4.1% of brown-headed cowbirds, Molothrus ater (Boddaert, 1783) ( Hahn et al. 2000).

The lack of records of Philopterus complex lice on icterid hosts may be related to the presence of lice of the genus Bizarrifrons Eichler, 1938 on some icterid hosts. This genus belongs to the Brueelia complex ( Valim & Palma 2012; Gustafsson & Bush 2017) and is also considered to belong to the ‘head louse ecomorph’. Competition may influence the distribution of these lice, but more ecological information is needed to assess any potential interactions between these species.

Both P. agelaii and P. quiscali are in need of redescription before an adequate comparison between these species and P. coriaceus sp. nov. can be made. It is not clear what gender of P. quiscali was described by Osborn (1896); however, Emerson (1960) noted that only one female and a nymph are present in Osborn’s collection at Ohio State University, Columbus, Ohio. Emerson (1960) designated the female as the lectotype, stating that a female was illustrated. This seems incorrect, as the illustrated specimen has a rounded terminal abdomen and no medianly continuous tergopleurite, suggesting that it is a male. If so, the illustrated male is likely lost.

Figures

Fig. 37. Philopterus coriaceus sp. nov. ex Molothrus oryzivorus oryzivorus (Gmelin, 1788), male habitus, dorsal and ventral views.

Fig. 38. Philopterus coriaceus sp. nov. ex Molothrus oryzivorus oryzivorus (Gmelin, 1788), female habitus, dorsal and ventral views.

Figs 39–42. Philopterus coriaceus sp. nov. ex Molothrus oryzivorus oryzivorus (Gmelin, 1788). 39. Male head, dorsal and ventral views. 40. Male genitalia, dorsal view. 41. Male genitalia, ventral view. 42. Female subgenital plate, vulval margin, and subvulval plates, ventral view.