Rhinonyssus nenecoi Gastal & Mascarenhas & Bugoni 2023, sp. nov.

Rhinonyssus nenecoi sp. nov.

(Figs. 1–4)

Type material. Holotype (IBSP 18863) and paratypes (IBSP 18864–18868) (females) from Brazil: Praia do Cassino (Cassino Beach), Rio Grande municipality, Rio Grande do Sul State, 27 May 2020.

Diagnosis. Oval body shape with a strongly sclerotised podosomal shield covering more than half of the dorsal idiosoma; shield with four pairs of minute setae; podosomal shield with gradually tapering posteromedial projection forming a V-like shape; sternal shield sclerotised and irregular in shape; ventral opisthosoma with 7–8 setae.

Description

Female (holotype and five paratypes)

Measurements: Length of body including palps (LID) 710 (610−860); width of idiosoma (WID) 504 (460−600); length of podosomal shield 490 (460−530); width of podosomal shield 388 (370−400); length of gnathosoma 203 (188−233); width of gnathosoma 143 (130−153); length of palps 142 (130−150); length of chelicerae 122 (115−125); width of chelicerae 29 (28−33); length of chelicera mobile digit 25 (1 specimen measured); length of genital shield 161 (128−225); width of genital shield 165 (120−235); length of sternal shield 129 (120−148); width of sternal shield 119 (103−125); length of legs: leg I 532 (500−560); leg II 512 (500−530); leg III 512 (500−530); leg IV 508 (500−520).

Dorsal idiosoma: Idiosoma elliptical, podosomal shield reticulated, covering more than half of anterior idiosoma. Podosomal shield strongly sclerotised, with four pairs of minute setae, with prominent posteromedial projection tapering gradually forming a V-like shape. Mesosomal shieldlets absent. Dorsal idiosoma without setae. Stigmata without peritremes, located dorsolaterally at level of coxae IV (Figs. 2 and 4A). Anus situated dorsoterminally, flanked by a pair of para-anal setae (Fig. 4B).

Ventral idiosoma: Reticulate sternal shield sclerotised, irregular in shape and variable in size. Sternal setae strongly reduced and represented by alveoli, one pair of sternal setae on the shield, another pair of setae in soft cuticle posterior to sternal shield. Genital shield wider than long, rounded posteriorly, surface reticulate and devoid of setae. Ventral opisthosoma with 3–4 pairs of setae (Figs. 3 and 4C).

Gnathosoma (Fig. 4D): Gnathosoma ventral in position. Hypostomal setae and deutosternal teeth absent. Palps four-segmented, chaetotaxy of palps 0–2–1–7. Two apical pairs of setae noticeably longer than other setae of apical palpal segment. Chelicerae widest proximally, tapering distally.

Legs (Figs. 2 and 3): Chaetotaxy of legs I–IV: coxae 2–2–2–1; trochanters 3–5–4–4; femurs 7–8–6–6; genua 6–5–7–4; tibiae 6–5–5–5; tarsi 24–14–14–11. Leg segments with three types of setae: short and thickened; medium length and sharply tipped; and longer filamentous. Short and thickened and medium length and sharply tipped setae situated on trochanters, tibiae and tarsi. Longer filamentous setae situated on ventrolateral portion of coxae and in apical portion of the tarsi. Ambulacrum present in all tarsi, noticeably elongated on leg I. Claws of all legs simply curved, hook-like. Empodium covers bases of claws.

Male and immatures. Unknown.

Parasitological indices. One out of three D. capense (33.3%) was parasitised by R. nenecoi. Mean abundance was three and the mean intensity was nine mites/host.

Etymology. The specific name, nenecoi, is in honour of Rodolfo Pinho da Silva-Filho (Neneco) in recognition of years of work with wildlife rehabilitation including seabirds, and for encouragement with our studies on nasal mites.

Remarks. Rhinonyssus nenecoi is most similar to R. procellaricus Gastal, Mascarenhas & Bugoni, 2022, described from Manx Puffinus puffinus and great Ardenna gravis shearwaters (Procellariiformes: Procellariidae). The new species also resembles R. pluvialis Fain & Johnston, 1966 found in the golden plover Pluvialis dominica Statius Müller, 1776 (Charadriiformes: Charadriidae) (Fain & Johnston 1966), a common shorebird in southern Brazil. The three species are similar in terms of body shape, sternal shield, genital plate and dorsal podosomal plate size and shape.

Rhinonyssus nenecoi differs from the species mentioned above in the podosomal shield size, number of setae and the posteromedial projection shape. The new species is similar in size with R. procellaricus (LID: 650−975; WID: 450−625) (Gastal et al. 2022) and smaller than R. pluvialis (LID: 804–900; WID: 530–600) (Fain & Johnston 1966). Rhinonyssus nenecoi has four pairs of setae on the podosomal shield while R. procellaricus and R. pluvialis podosomal shields are devoid of setae. The posteromedial projection of the podosomal shield gradually tapered forming a “V” shape in R. nenecoi, while in R. procellaricus the posteromedial projection is relatively narrower and finger-like, and R. pluvialis has a dorsal shield similar to a lozenge (sensu Fain & Johnston 1966).

Rhinonyssus nenecoi and R. procellaricus have a trapezoidal sternal plate, however, in the later species it is smaller in size. The sternal shield in R. pluvialis is square. Rhinonyssus nenecoi and R. pluvialis have two pairs of sternal setae and R. procellaricus has three pairs. Rhinonyssus nenecoi has three or four pairs of ventral opisthosomal setae, while R. procellaricus and R. pluvialis have a single pair. Additionally, leg chaetotaxy also differs in the number of setae from the three similar species.