Goniodes, Nitzsch, 1818

Gustafsson, Daniel R., Grossi, Alexandra A., Ren, Mengjiao & Zou, Fasheng, 2023, The Goniodidae (Phthiraptera: Ischnocera) of peafowl (Aves: Galliformes: Pavo), with description of a new genus, Journal of Natural History 57 (17 - 20), pp. 996-1048 : 1040

Goniodes s. lat

We here retain Goniodes as a broad, morphologically heterogeneous genus, as only a few species have been examined. However, few characters seen in the type species are consistent throughout Goniodes as currently defined, and some characters – such as the structure of the male genitalia – are not found in any other groups within Goniodes . Significant variation exists between different groups of Goniodes in characters such as: the structure, chaetotaxy, presence and extent of squamous areas, and sexual dimorphism of antennae; the shape and chaetotaxy of the temples; the head, thoracic and abdominal chaetotaxy; the fusion and structure of male abdominal tergopleurites IX–XI; the sclerites, fleshy lobes, and chaetotaxy of the female genital region; the structure, shape, symmetry, and chaetotaxy of the male genitalia.

Among the species we have examined, most of the groups within Goniodes circumscribed by one of these sets of characters are also circumscribed by other sets of characters. This indicates that in most cases, a wide range of morphological characters separate each group from the others. Clay (1940) separated many of these groups as species groups, and von Kéler (1940) separated them as genera. The revival of some of these genera by Mey (2009) appears to be well supported both morphologically and genetically ( Johnson et al. 2011), but a more thorough revision is needed to establish generic limits in this group.

Even the two species of Goniodes treated here are significantly different in, for example, the male and female genitalia. This, in combination with differences in non-genitalic characters, suggests that G. pavonis and G. meinertzhageni may not be closely related. These two species were placed in different species groups by Clay (1940: species groups A and B), although these were stated to have ̍affinities̾, primarily in the male scape and the thoracic chaetotaxy. Notably, the species placed in group B by Clay (1940) are also not morphologically homogeneous, and may represent multiple genera; this will be discussed in a separate publication.

Neither of the two species of Goniodes treated here appears to be closely related to other goniodid lice on related hosts (eg the genera Afropavo , Argusianus , and Rheinardia Maingonnat, 1882 ; Wang et al. 2014; Chen et al. 2021; Kimball et al. 2021). Goniodes wilsoni Clay, 1936 from Afropavo congensis has sexually monomorphic antennae, simple solenoid male genitalia, and head and thoracic chaetotaxy that may be unique within the Goniodidae . Goniodes curvicornis Nitzsch [in Giebel], 1866 from Argusianus argus ( Linnaeus, 1766) may be reminiscent of G. pavonis in the general structure of the male antennae and genitalia, but differs significantly in, for example, head shape, chaetotaxy, and most details of the male genitalia. Host associations are thus unlikely to give any clues as to the generic limits of Goniodes s. str.

The morphological distinctness of Goniodes pavonis suggests that this species may be evolutionarily isolated. Based on specimens of Goniodes spp. we have examined, a thorough revision of the genus may leave G. pavonis as the only remaining species of the genus, changing Goniodes from being a relatively large group of lice to being monotypic. The taxonomic changes may thus be profound, but inevitable due to the original choice of type species. However, no such sweeping changes are proposed here.