Species Composition of Parasitic Mites of the Subfamily Picobiinae (Acariformes: Syringophilidae) Associated with African Barbets (Piciformes: Lybiidae)

Simple Summary This study investigated the picobiine mites parasitising African barbets. The results showed that this bird family is more widely infested by feather mites than previously thought, with three species of the genus Tanopicobia found on ten African barbet species. Birds belonging to the family Lybiidae have a unique parasite fauna consisting exclusively of mites from the genus Tanopicobia, which is restricted solely to African barbets. Based on the distribution of the genus Tanopicobia on the studied barbet hosts, our results also provide indirect cues that the host genus Trachyphonus, attributed to such different avian families, e.g., Capitonidae, Ramphastidae, is part of the family Lybiidae, whereas other/related bird families have their own distinct quill mite fauna. Abstract In this study, we conducted a parasitological investigation of the quill mite fauna of the subfamily Picobiinae (Acariformes: Prostigmata: Syringophilidae) associated with African barbets (Aves: Piciformes: Lybiidae). We examined twenty-seven host species, representing 57% of the forty-seven known host species in the family Lybiidae, belonging to seven genera (70% of the ten genera in the family). Our research revealed that ten host species were infested by three species of picobiine mites belonging to the genus Tanopicobia: (1) Tanopicobia hallae Sikora and Skoracki, sp. n., from three species of the genus Lybius and two species of the genus Tricholaema, (2) Tanopicobia stactolaema Sikora and Skoracki, sp. n., from two species of the genus Stactolaema, and (3) Tanopicobia trachyphoni Skoracki et al., 2020, collected from three host species of the genus Trachyphonus. Our findings demonstrate that birds belonging to the family Lybiidae have a specific parasite fauna consisting exclusively of mites of the genus Tanopicobia; this mite genus is apparently restricted to African barbets.


Introduction
Quill mites of the subfamily Picobiinae (Acariformes: Prostigmata: Syringophilidae) are permanent and host-specific ectoparasites of birds. Their whole life cycle takes place inside quills of the contour feathers where they live, feed, and reproduce [1][2][3][4]. The exception is an ambiguous species Calamincola lobatus Casto, which inhabits quills of secondaries [5]. Currently, the subfamily comprises c.a. 80 described species grouped in 12 genera and recorded from more than 200 host species belonging to neognathous birds (Aves: Neognathae) [4,6]. The quill mite fauna of picobiines, known from birds Animals 2023, 13,2007 2 of 11 of the order Piciformes, are still understudied. Although the first record of picobiine mites from Piciformes was presented more than a hundred years ago when Haller, in 1878, described the first species Picobia heeri [7], it is only relatively recently that intensive research on this group of hosts has begun. In several papers, the picobiine fauna have been presented for birds of the families Lybiidae [8], Picidae [1,3,4,[9][10][11][12][13][14], Semniornithidae [15], and Ramphastidae [16]. To this time, we have no data on the presence of picobiine mites from birds of the families Megalaimidae, Capitonidae, and Indicatoridae.
In this paper, we present the results of our study on quill mites of the subfamily Picobiinae parasitising African barbets (Lybiidae). This avian family comprises about 41 species grouped in seven genera distributed mainly in sub-Saharan Africa [17][18][19]. The African barbets are medium-sized birds, ranging from 15 to 30 cm in length and are found in a variety of habitats, including forests, woodlands, savannas, and gardens. Some species are more specialised, inhabiting specific habitats such as montane forests or riverine woodlands. Several species of African barbets are considered threatened or endangered due to habitat loss and fragmentation, particularly in West and Central Africa. Overall, the African barbets are a fascinating group of birds that play important ecological roles in African ecosystems [18][19][20]. The Lybiidae family consists of bird species with different social organizations: some species live in single pairs, while other species live in family groups and even small colonies and are considered as group breeding species [21]. It is thus an excellent family to study the evolution of the host-parasite speciation and transmission according to the degree of complexity of the social organization, as well as possible interspecies contamination. Moreover, African barbets are nesting in tree cavities, which also could modify the probability of infestation by ectoparasites, and even more interestingly, they are brood-parasitised by other piciform birds, e.g., Indicatoridae [19].
Because to date, only one species, Tanopicobia trachyphoni Skoracki et al., has been recorded from one host species, i.e., the red and yellow barbet, Trachyphonus erythrocephalus Cabanis [8], we conducted a parasitological investigation of the picobiine fauna associated with the birds of the family Lybiidae. Our research revealed that ten host species were infested by three species of picobiine mites, including two species described herein as new to science. Our findings demonstrate that birds belonging to the family Lybiidae have a unique parasite fauna consisting exclusively of mites from the genus Tanopicobia and that the distribution of this mite genus is restricted solely to African barbets.

Materials and Methods
The mite material used in this study was collected from dry bird skins housed in the ornithological collection of the Bavarian State Collection of Zoology (Munich, Germany) (by M.S and M.U.), according to the technique described by Skoracki [3] ( Figure 1A-D). Additional mite material was collected from the yellow-breasted barbet Trachyphonus margaritatus (Cretzschmar) captured during a field expedition in Djibouti (by B.S. and M.M-I) (permit no. 438/DEDD/2020 to M.M-I) ( Figure 1E).
We examined the quills of approximately ten contour feathers in the proximity of the cloaca region for each bird. Before mounting, mites were treated in Nesbitt's solution at room temperature for three days, following the procedure outlined by Walter and Krantz [22] and Skoracki [3] to soften and clear them. Subsequently, the mites were mounted on slides in Hoyer's medium and examined under a light microscope (ZEISS Axioscope, Oberkochen, Germany) with differential interference contrast (DIC) illumination. To illustrate the findings, we created drawings using a camera lucida drawing attachment. Finally, drawings were made using a camera lucida drawing attachment.

Differential Diagnosis
Tanopicobia stactolaema sp. n. is morphologically similar to the above-described species, T. hallae sp. n., by the presence of the well-visible hysteronotal shields and is distinguishable by the following features: in females of T. stactolaema, the propodonotal, hysteronotal, and pygidial shields are apunctate; the posterior margins of the hysteronotal shields reach bases of setae e2; the lengths of propodonotal setae ve and si are 60-70 and 80-90, respectively; the lengths of hysteronotal setae d1 and d2 are 70-80 and 80-95, respectively; setae f2 are slightly (1.3 times) longer than f1; coxal fields III and IV are apunctate, and setae 4c are 45-55 long. In females of T. hallae, the propodonotal, hysteronotal, and pygidial shields are punctate; the posterior margins of the hysteronotal shields not reach bases of setae e2; the lengths of propodonotal setae ve and si are 45 and 50-70, respectively; the lengths of hysteronotal setae d1 and d2 are 105-115 and 110-115, respectively; setae f2 are 3.5-4 times longer than f1; coxal fields III and IV are punctate, and setae 4c are 75-80 long.

Etymology
The specific name "stactolaema" is taken from the generic name of the host.
Tanopicobia trachyphoni Skoracki, Sikora, Jerzak and Hromada, 2020 ( Figure 5) This species was recently described from the red-and-yellow barbet Trachyphonus erythrocephalus Cabanis in Tanzania [8], and there have been no other records since the first description. Herein, we report two new hosts species for this quill mite: the yellowbreasted barbet, Trachyphonus margaritatus (Cretzschmar), from Djibouti and Eritrea and the d'Arnaud's barbet Trachyphonus darnaudii (Prévost and des Murs), from Tanzania. Because this species was described based only on the holotype and two female paratypes, herein, we give additional data for its description based on the material collected from the type of host species, T. erythrocephalus, from Tanzania.
Tanopicobia trachyphoni Skoracki, Sikora, Jerzak and Hromada, 2020 ( Figure 5) This species was recently described from the red-and-yellow barbet Trachyphonus erythrocephalus Cabanis in Tanzania [8], and there have been no other records since the first description. Herein, we report two new hosts species for this quill mite: the yellowbreasted barbet, Trachyphonus margaritatus (Cretzschmar), from Djibouti and Eritrea and the d'Arnaud's barbet Trachyphonus darnaudii (Prévost and des Murs), from Tanzania. Because this species was described based only on the holotype and two female paratypes, herein, we give additional data for its description based on the material collected from the type of host species, T. erythrocephalus, from Tanzania.

Discussion
To date, only one species, Tanopicobia trachyphoni Skoracki et al., has been recorded from one host species, the red and yellow barbet, Trachyphonus erythrocephalus Cabanis [8]. Herein, we conducted a parasitological investigation of the picobiine quill mite fauna associated with birds of the family Lybiidae. Above, we have demonstrated that this bird family is much more widely infested by quill mites than previously thought [8]. Our research has identified the presence of three species of picobiine mites of the genus Tanopicobia on ten African barbets belonging to the four genera, i.e., Trachyphonus (three species), Tricholaema (two species), Lybius (three species), and Stactolaema (two species). Our findings presented in this study, demonstrate that birds belonging to the family Lybiidae have a unique parasite fauna consisting exclusively of mites from the genus Tanopicobia (lack members of the other picobiine genera) and that the distribution of this mite genus is restricted solely to the African barbets. Unfortunately, the small sample size of individuals examined from the genera Gymnobucco, Pogoniulus, and Buccanodon has not allowed us to confirm the presence of mites on these birds, but we are rather confident that future studies will demonstrate the occurrence of mites on these bird genera. Additionally, given that all examined bird genera of the African barbets were infested by members of the genus Tanopicobia, it is expected that species (supposedly new to science) of this genus will also be present on these birds.
Systematic position of Trachyphonus birds vs. quill mites. The genus Trachyphonus Ranzani, comprises five species distributed exclusively in sub-Saharan Africa [17,20]. Although Trachyphonus is currently classified in the family Lybiidae, the relationship of this genus seems to be one of the most intricate problems in the barbet phylogeny. Swierczewski and Raikow [26], using variations in the hind limb muscle, and Bellman [27], analysing fossil records, proposed that Trachyphonus is the sister group to the rest of the species in the family Capitonidae. Later, Prum [28] used a cladistic analysis of morphological characters and placed the representatives of Trachyphonus in the newly erected subfamily Trachymphoninae in the family Ramphastidae. In 2000, Barker and Lanyon used mitochondrial DNA sequence data [29] and placed it as the sister taxon to the Neotropical radiation. In contrast, in 2004, Moyle, based on the combined gene analyses, placed Trachyphonus as the basal taxon of the African radiation and indicated that African barbets (Lybiidae) are monophyletic [30]. Moreover, Trachyphonus is considered to be an old and early diverging lineage [26,28,[30][31][32], which may not even be closely related to other African barbets [30]. Our parasitological investigation of the picobiine mites associated with African barbets provides indirect but rather supportive evidence that birds of the genus Trachyphonus are indeed part of the family Lybiidae, as they host the same quill mites of the genus Tanopicobia as other members of this bird family. In contrast, the other families of the order Piciformes have their own distinct quill mite fauna, e.g., mites of the genera Picobia and Neopicobia infest birds in the family Picidae, Pseudopicobia infests birds in the family Bucconidae, and Rafapicobia infests birds in the families Semniornithidae and Ramphastidae [1,3,4,[8][9][10][11][12][13][14][15][16].

Conclusions
This study investigated the quill mites on birds of the family Lybiidae (African barbets). The results showed that this bird family is more widely infested by feather mites than previously thought, with three Tanopicobia species found on ten African barbet species. Birds belonging to the family Lybiidae have a unique parasite fauna consisting exclusively of mites from the genus Tanopicobia, which is restricted solely to African barbets. The study also provides indirect evidence that birds of the genus Trachyphonus are indeed part of the family Lybiidae based on their hosting of Tanopicobia quill mites, while other bird families have their own distinct quill mite fauna.