Research Article |
Corresponding author: Rodrigo L. Ferreira ( drops@ufla.br ) Academic editor: Rajko Dimitrijević
© 2022 Guilherme C. Prado, Gerhard C. Du Preez, Rodrigo L. Ferreira.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Prado GC, Du Preez GC, Ferreira RL (2022) Selachochthonius naledi sp. nov. (Pseudoscorpiones, Pseudotyrannochthoniidae), a new troglobitic species from South Africa. Subterranean Biology 42: 125-138. https://doi.org/10.3897/subtbiol.42.79190
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A new pseudoscorpion species, Selachochthonius naledi sp. nov., is herein described. It can be distinguished from the other species of the genus mainly by the absence of eyes, number and morphology of chelal teeth and coxae setae and by the appendices proportions. This new species represents the fourth record for the genus in South Africa. We also provide some ecological remarks of the new species and recommendations for future research.
Cave-dwelling, pseudoscorpion, taxonomy
Pseudoscorpions (Arachnida: Pseudoscorpiones) are small sized predatory arthropods distributed throughout terrestrial habitats commonly found across six continents (except for Antarctica). They occur in a diversity of habitats including leaf litter, beneath bark or stones, as well as bird nests or animal burrows. Several species are also recorded from caves and may exhibit subterranean-adapted traits (
The family Pseudotyrannochthoniidae comprises 69 species distributed in five genera: Allochthonius Chamberlin, 1929 with 28 species, Afrochthonius Beier, 1930 with seven species, Centrochthonius Beier, 1931 with three species, Pseudotyrannochthonius Beier, 1930 with 28 species and Selachochthonius Chamberlin, 1929 with three species (
This family is diagnosed by the presence of ib and isb trichobothria located at the base of the fixed finger and coxal spines present only in coxae I (
During an expedition to caves in South Africa (carried out 5–17 October 2019), two specimens of Pseudotyrannochthoniidae pseudoscorpions were found, belonging to a new species herein described. We also provide some notes on its habitat and potential threats, conservation issues, a brief discussion on its association with the cave environment and a comparison of morphological features with all Selachochthonius species, presenting their distribution in South Africa.
The study areas included two cave systems, namely Villa Louisa (26°01'25.5"S, 27°42'43.0"E) and Yom Tov (26°01'14.92"S, 27°42'53.46"E) caves (Fig.
Distribution map of Selachochthonius species in South Africa A Africa continent, detail on South Africa country B South Africa, exhibiting distribution of Selachochthonius species with detail on S. naledi sp. nov. type localities C Selachochthonius naledi sp. nov. distribution area, exhibiting Yom Tov, Villa Louise and Rising Star Caves (Homo naledi type locality), detail on quarry activity occurring nearby.
Fieldwork was conducted in October 2019. This trip was part of a worldwide scale project (with samplings in all continents, except Antarctica) aiming to evaluate how habitat traits influences invertebrate communities (manuscript in prep.). In South Africa, seven caves were sampled. Untimed direct intuitive searches (sensu
To properly examine taxonomic characters, specimens were photographed, dissected and mounted on temporary cavity slides with glycerine. Photographs and measurements were taken using a Zeiss Axio Zoom V16 stereomicroscope and ZEN 2.3 software package. Appendices and structures were mounted on Kaiser’s glycerol gelatine for drawings, due to its stabilisation and low temperature solidification. Drawings were prepared with a drawing tube on an Olympus BX40 optical microscope equipped with phase contrast. Following, illustrations were vectorized using Inkscape 1.1 software package (
Terminology follows
Family Pseudotyrannochthoniidae Beier, 1932
Holotype female (NCA 2021/1351), preserved in ethanol: South Africa, Cradle of Humankind (UNESCO WHS), Maquassi Hills Municipality, Villa Louisa cave (26°01'25.5"S, 27°42'43.0"E), 09 October 2019, leg. R.L Ferreira. Paratype male (NCA 2021/1352), Cradle of Humankind, Maquassi Hills Municipality, Yom Tov Cave (26°01'14.92"S, 27°42'53.46"E), 17 October 2019, leg. R.L Ferreira.
The epithet naledi refers to Homo naledi, an extinct hominid species discovered within the Dinaledi chamber. This chamber is located in the Rising Star Cave (Fig.
Selachochthonius naledi sp. nov. differs from other members of the genus by the following combination of characters: absence of eyes or eyespots (S. heterodentatus Beier, 1995 with four well-developed eyes and S. serratidentatus Ellingsen, 1912 bearing four small eyes) (
(Fig.
Carapace. (Fig.
Selachochthonius naledi sp. nov. A left chelicera of female holotype, antiaxial view B female holotype carapace, showing chaetotaxy of carapace C detailed anterior margin of female paratype carapace D detailed anterior margin of male paratype carapace E leg IV of female holotype, showing tubercle location. Scale bars: 0.25 mm (A, C–D); 0.5 mm (B, E).
Chelicera. (Fig.
Tergites . Not divided; surface smooth; chaetotaxy uniseriate, I–XI 2: 2: 4: 4: 4–6: 6–8: 6: 4–6: 4: 4: 4. Anal operculum with two dorsal setae. Pleural membrane smooth.
Coxae. (Fig.
Selachochthonius naledi sp. nov. A female holotype palp and pedal coxae B detail of female holotype coxa I C detail of female holotype coxal spines D leg I of female holotype E male paratype genitalia, showing arrangement of setae F right pedipalp of female holotype, dorsal view. Scale bars: 0.3 mm (A); 0.1 mm (B–C); 0.5 mm (D); 0.05 mm (E); 1.0 mm (F).
Genital operculum of female: setae distributed in three horizontal rows: 2: 2: 3, genital opening not bifurcated (horizontally contiguous).
Genital operculum of male (Fig.
Sternites. chaetotaxy IV‒XI: 10–12: 12–14: 6–12: 6–8: 6: 6: 6: 4. Anal operculum with two ventral setae.
Palp
(Fig.
Selachochthonius naledi sp. nov., female holotype A right pedipalp chela, showing lyrifissures and trichobothrial pattern, dorsal view B right pedipalp chela, showing lyrifissures arrangement, ventral view C left pedipalp chela, showing teeth morphology, trichobothrial pattern and tubercle location, antiaxial view D right pedipalp chela, antiaxial view. See Material and methods for abbreviations. Scale bar: 1.0 mm.
Leg.
IV (Fig.
Measurements. (length/width or depth in mm; ratios in parenthesis calculated by using three significant digits): Female holotype and male paratype range. Body length 2.33 [1.86]. Carapace 0.55–0.70/0.52–0.70 (1.0). Palps: trochanter 0.21–0.35/0.15–0.20 (1.4–1.8), femur 0.93–1.22/0.14–0.20 (6.2–6.6), patella 0.38–0.51/0.16–0.21 (2.3–2.4), chela 1.39–1.8/0.30–0.23 (6.1–6.2), movable finger length 0.92–1.14. Leg I: trochanter 0.13–0.23/0.10–0.18 (1.3), femur 0.44–0.67/0.08–0.10 (5.9–6.8), patella 0.29–0.38/0.07–0.09 (4.1–4.4), femur/patella 1.5–1.8, tibia 0.23–0.35/0.05–0.07 (4.3–5.1), tarsus 0.54–0.65/0.05–0.06 (10.7–11.3). Leg IV: Trochanter: 0.24–0.27/0.13–0.17 (1.6–1.8), femur + patella 0.77–1.30/0.19–0.27 (4.1–4.8), tibia 0.50–0.68/0.10–0.12 (5.2–5.4), basitarsus 0.25–0.30/0.07–0.09 (3.4–3.6), telotarsus 0.55–0.73/0.05–0.06 (10.9–12.1).
Despite extensive efforts in search of invertebrates in the caves, only two specimens of Selachochthonius naledi sp. nov. were found, thus indicating their low population density. In both Vila Louise and Yom Tov caves, the specimens were found in the deeper, moist and aphotic areas. The two individuals were collected from under block rocks in the cave floor. Neither specimens exhibited any phototactic behaviour. An interesting behaviour was observed for the individual from Vila Louise cave (female holotype): when gently touched by the brush bristles, the individual responded aggressively, repeatedly grasping the bristles. Even though one of the authors (RLF) has been collecting cave pseudoscorpions for the last 30 years (especially Chthonioidea), this “aggressive” behaviour has never been recorded by him before. Potential prey in both caves include springtails, juvenile crickets and isopods (Styloniscidae).
Species of Selachochthonius have been reported from four areas in South Africa (Fig.
Overall, the taxonomy of Selachochthonius has some shortcomings due to lack of detailed morphology on the characters used to differentiate pseudotyrannochthoniid species. The diagnosis of the genus is largely based on the type species S. serratidentatus, originally attributed to Chthonius by
The absence of eyes or eyespots –– a feature frequently attributed to subterranean-adapted species –– is observed in the new species and in S. cavernicola (
Currently, S. serratidentatus and S. heterodentatus are only found in epigean environments, thus not presenting any subterranean-adapted traits (
The external area surrounding the caves in the Cradle of Humankind is highly altered, especially by deforestation. The caves’ entrances are usually associated with small bush patches surrounded by grass (Fig.
The caves in the surrounding region are also heavily impacted. For example, the calcite deposits in many of the caves were previously mined. Vila Louise Cave is highly altered due to past removal of calcite. As a result, the cave’s conduits and floor were severely changed in part by walls that were built inside the cave (Fig.
A major concern related to this species’ conservation is the risk of contaminants originating from the farms and small factories in the surrounding area entering the cave systems. Furthermore, it is important to visit other caves in the area to search for additional specimens and determine, with accuracy, the actual distribution of this species.
We are thankful to Dr. Marconi Souza Silva (Lavras) for all the help during the field samplings and for the photograph of the live specimen in Vila Louisa Cave. We thank the institutions that supported the study with funding for scholarships and infrastructure (FAPEMIG and VALE). RLF is grateful to the CNPq (National Council for Scientific and Technological Development) for the grant provided (CNPq n. 308334/2018-3). We are also grateful to the reviewers, Dr. Mark Harvey, Dr. Jana Christophoryová and the editor Dr. Rajko Dimitrijević, whose suggestions and comments improved the quality of this paper.