The fauna of whip spiders (Amblypygi) in Western Africa is poorly known but probably diverse. Here, I describe the new species Charinus kakum sp. n. based on female morphology, and accompanied by DNA sequence data. The species is small and differs from other African species of Charinus in the low number of pseudosegments on leg IV, female genital features, spination patterns of the pedipalp, and small body size. It was collected from wet tropical rainforest in Kakum National Park, Ghana and is only the fourth species of Charinus to be recorded from the highly diverse Western African biodiversity hotspot. With a total body length of not even 6 mm it is also one of the smallest whip spiders in the world.

Amblypygid, Arachnida , Kakum National Park, new species, taxonomy

The mesic forests of Western Africa are a biodiversity hotspot and notable for their iconic fauna which includes more than 320 mammals and almost 800 bird species (Mittermeier et al. 2004). This fauna is threatened by rapid habitat loss caused predominantly by logging, plantation agriculture and mining. The invertebrate fauna of Western Africa is still largely unexplored, even compared with other hotspots, and very little is still known about the arachnid fauna. This is particularly the case for whip spiders (Amblypygi), a small order of arachnids with more than 200 species that occur in tropical and subtropical regions all over the world (Harvey 2013; Miranda et al. 2016a). Whip spiders are easily recognized by their flattened body, the robust pedipalp with strong spines that function as a trapping basket for prey, and the first legs that are strongly elongated and have sensory function (Weygoldt 1996, 2000a; Garwood et al. 2017). All whip spiders are nocturnal hunters and usually found on bark, in caves or under rocks. The Western African fauna currently comprises eight species in the genera Charinus (3 species), Damon (4 species) and Phrynichus (1 species). As such, whip spiders are poorly known here by comparison with other regions in Africa, say Tanzania, where 10 species have been described (Harvey 2013). The primary reason for this low number is probably sampling effort and the scarcity of comprehensive invertebrate surveys in Western Africa, but also the lack of taxonomists studying the invertebrate fauna of this region.

Here, a new species of whip spider is described that was collected during recent fieldwork in Kakum National Park, Ghana. This species is small and belongs to the circumtropical genus Charinus which occurs in Western Africa with three described species: Charinus fagei Weygoldt, 1972 and Charinus milloti Fage, 1939 from caves in Guinea, and Charinus africanus Hansen, 1921 from Equatorial Guinea and the islands of São Tomé and Príncipe. All species of Charinus are small by comparison with Damon and Phrynichus (usually < 1.5 cm in body length) and collected infrequently because of their cryptic nature. Charinus kakum sp. n. is only the second species of whip spider to be described from Ghana, apart from the much larger Damon medius (Herbst, 1797) (Harvey 2013).

This paper aims to describe the first species of Charinus from Ghana based on female morphology, but also provides a DNA barcode that will help to delineate this species from others. In documenting this species, I hope to raise further awareness of the potentially diverse but clearly understudied arachnid fauna of Western Africa, which remains to be documented and studied on detail to assist conservation efforts.

Morphology. The holotype of Charinus kakum was stored in 100 % ethanol but transferred to 75 % ethanol for morphological examination. A fragment of leg IV was removed prior to the examination for molecular analyses. Imaging of key-taxonomic characters was achieved using a custom-built BK Plus Lab System by Dun, Inc with integrated Canon EOS camera, macrolenses (65 mm and 100 mm) and the stacking software Zerene Stacker. The images were edited and formatted in Adobe Photoshop CS6. Measurements were taken using a micrometric ruler fitted on the eyepiece of a Leica M125 stereomicroscope and are expressed in millimeters (mm). Abbreviations: Bt = Basitarsus; Dt = Distitarsus; Fe = Femur; Ti = Tibia; Tr = Trochanter; LE = lateral eyes; ME = median eyes. The terminology of body parts follows Weygoldt (2000a) and spine counts were made from proximal to distal.

Molecular study. A 632 bp fragment of the mitochondrial CO1 gene was amplified using the protocol described in a previous study (Harms and Framenau 2013), except that the Chelex protocol (Walsh et al. 1991) was used for DNA extraction.

Whip spiders have rarely been recorded in Western Africa but this probably indicates the poor state of collecting compared to other regions of the continent, in particular eastern and southern Africa. The current knowledge on African whip spiders was summarized by Weygoldt (1998b; 1999, 2000a) who recognized seven species of Charinus in Africa: C. abbatei Delle Cave, 1986 from Somalia, C. africanus from islands in the Gulf of Guinea, C. diblemma Simon, 1936 from Zanzibar, C. fagei Weygoldt, 1972 and C. milloti Fage, 1939 from Guinea, C. jeanneli Simon, 1936 in Tanzania, and C. madagascariensis Fage, 1954 from Madagascar; but note that there is uncertainty about the status of C. diblemma and C. jeanneli which are currently considered nomen dubia (Harvey 2013).

Aside from the little-known small species of Charinus, more data are currently available on the large species belonging to Damon and Phrynichus, which are collected and studied more frequently at the systematic level (e.g. Weygoldt 1999b, Prendini et al. 2005) but also in terms of behavior and mating biology (e.g. Weygoldt 1998a, 1999a). Most of the large species are currently understood to be widespread and have linear ranges of 500 km or more, as evidenced by morphological and molecular data (Weygoldt 2000b; Prendini et al. 2005). Very little is known about the diversity and distribution of the much smaller and cryptic species of Charinus, which are collected infrequently but are also less common in museum collections. No molecular phylogenetic or phylogeographic studies are currently available for this fauna, but it is notable that records of the described Charinus species are often from the locus typicus or smaller areas, such as a couple of islands in the case of C. africanus (Harvey 2013). Nothing is known about the dispersal capacities of these whip spiders but it could be that the ranges of some species are quite restricted and dispersal capacities are often low. This claim may be supported by the large number of cave-dwelling species that are endemic to a specific karst system. Conversely, other species, such as Charinus ioanniticus (Kritscher, 1959) from the eastern Mediterranean, have been collected from rocky crevices, caves and cellars in Greece Turkey, Israel and Egypt (Blick and Seiter 2016; Miranda et al. 2016b) and seem to be widespread, although the latter claim is based on an interpretation of morphological characters and needs to be retested using genetic data. Detailed molecular phylogeographic studies on single species and the genus as a whole are clearly needed to infer range sizes and distributions but this can only be achieved through field work and more comprehensive surveys, which in the case of Western Africa have yet to be undertaken. The lack of any reference sequences for Charinus from Africa on Genbank and BOLD also illustrates the poor state of knowledge at the molecular level and more data are also needed here.

It should also be noted that Charinus is probably polyphyletic and in urgent need of revision (Weygoldt 2000a, b). The type species of Charinus is from Samoa in the Pacific (C. australianus (L. Koch, 1867)) and it is quite possible that the African species will form a distinct genus following detailed analysis. Miranda et al. (2016b) recently defined species-groups within Charinus based on female genital morphology that show some geographical clustering (e.g. bengalensis-group for eight species from Africa, Arabia and central Asia) but again, molecular phylogenetic studies are needed to settle genus limits and distributions, and it is unclear whether this group is monophyletic. A PhD thesis on the systematics of Charinidae remains to be published (Miranda 2017) but this important work will hopefully clarify the status of the African species. Detailed re-illustration of the type material of the West African species C. africanus (probably Natural History Museum of Denmark), and C. millotei and C. fagei (Muséum national d’histoire naturelle Paris) may also help in this context.

Finally, this new species of Charinus is yet another example of how critically the Western African biota are undersampled for arachnids. Very little is still known about the invertebrate fauna of this biodiversity hotspot and many more species of Amblypygi will surely occur in Western Africa. Weygoldt (2000b) noted that “a close look in humid caves and in rain forests will reveal the existence of more species of the Charinidae in Africa. All species are small and hard to find”. Indeed, a recent study of karst invertebrates has documented whip spiders in at least three caves in different regions (Philips et al. 2016) and given the amount of range restriction in cave invertebrates, it is possible that these represent additional species of Charinus. Considering also that the main threat to invertebrate diversity in Western Africa is habitat loss through logging and agriculture, time is running thin to document this diversity and generate baseline data for nature conservation.

Thanks go to Nadine Dupérré (CeNak Hamburg) for preparing the drawings and images, Joseph Oppong from Forestry Commission, Wildlife Division in Accra, Ghana for assistance and issuing collecting permits (No. 0170180), Enoch Ashie (Ghana Heritage Conservation Trust) for facilitating field work in Kakum National Park, and Brian K. Williams (Hamburg) for assistance with fieldwork. Kerstin Dreczko (CeNak Hamburg) and Marcelo Christian (University of Hamburg) are acknowledged for sequencing the holotype. The baselayer map was downloaded from GeoCurrents. Two anonymous reviewers provided constructive comments on an earlier draft of this paper.