Research Article |
Corresponding author: János Novák ( novakjanos01@gmail.com ) Academic editor: Pavel Stoev
© 2020 János Novák, Michelle Lorenz, Danilo Harms.
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Citation:
Novák J, Lorenz M, Harms D (2020) Feaella (Tetrafeaella) obscura sp. nov. – a new pseudoscorpion species from the Maldives (Arachnida, Pseudoscorpiones), and an updated identification key to the subgenus Feaella (Tetrafeaella). Zoosystematics and Evolution 96(2): 769-779. https://doi.org/10.3897/zse.96.56885
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The Feaellidae Ellingsen, 1906 is a small but ancient family of pseudoscorpions with 20 extant species across the Southern Hemisphere, and fossils from the Lower Cretaceous of Myanmar and the Eocoene of Europe. Here, we describe and illustrate Feaella (Tetrafeaella) obscura sp. nov. as a new species from the Maldives archipelago in the Indian Ocean. This is the first record of Feaella from a young oceanic island and may indicate a potential for long-distance dispersal in this lineage. We also elevate Feaella (T.) capensis nana Beier, 1966 to full species rank as F. (T.) nana Beier, 1966 and provide an identification key to the members of the subgenus Feaella (Tetrafeaella), thereby facilitating the identification of species.
biogeography, dispersal, endemism, false scorpion, taxonomy
Pseudoscorpions belonging to the family Feaellidae Ellingsen, 1906 are amongst the most unusual arachnids and have a spectacular morphology that includes a carapace with multiple frontal lobes, a dorsoventrally flattened and heavily sclerotised body, and pedipalps that are stout, heavily armed and without a venom gland in both fingers (
Their strange morphology aside, feaellids are also of fundamental importance in understanding the evolution of character systems in pseudoscorpions (
Feaellidae are grouped into two subfamilies, Feaellinae (Ellingsen, 1906) and Cybellinae Judson, 2017 (Judson, 2017). Feaellinae comprises two genera, Feaella Ellingsen, 1906 from Africa, India, Madagascar, the Seychelles, Sri Lanka and Australia (
In this paper, we are describing Feaella (Tetrafeaella) obscura sp. nov. from the Maldives, which are comprised predominantly of young reef-islands and atolls in the Indian Ocean (
The specimens were found during an inventory in the collections of the Hungarian Natural History Museum (HNHM) and stored in 70% ethanol. They were cleared in a 3:1 mixture of lactic acid and gelatine to be examined with a Zeiss Stemi 2000-c stereomicroscope and a Zeiss Axioskop 2 light compound microscope. Drawings and measurements were made with the aid of the Zeiss Axioskop 2 microscope. Measurements were taken using the Olympus Soft Imaging analySIS work 5.0 software. Digital images were taken with a custom-made BK Plus Lab System by Dun, Inc. with integrated Canon EOS 7D Mark II, microscopic lens (5× and 10× magnification) and the Zerene stacker version 1.04 software. Scanned electron images were taken from temporarily dried specimens mounted on copper wire, using a Hitachi TM4000 Plus scanning electron micrograph (SEM). Mensuration follows the reference points in
Cheliceral trichobothriotaxy: bs = basal seta; sbs = subbasal seta; is = interior seta; es = exerior seta; ls = laminal seta; gs = galeal seta. Chelal trichobothriotaxy: eb = externo-basal; esb = externo-subbasal; est = externo-subterminal; et = externo-terminal; ib = interno-basal; isb = interno-subbasal; ist = interno-subterminal; it = interno-terminal; t = terminal; st = subterminal; sb = subbasal; b = basal; dt = duplex trichobothrium.
Superfamily Feaelloidae Ellingsen, 1906
Family Feaellidae Ellingsen, 1906
Subfamily Feaellinae Ellingsen, 1906
Remarks. The genus Feaella is divided into three subgenera: Feaella (Feaella), Feaella (Difeaella), and Feaella (Tetrafeaella) based on the number of frontal lobes on the carapace (
Holotype female from the Maldives, Kabudu Island (might refer to Kaudu [0°17'N, 73°1'E] or Kandudu Islands [2°19'N, 72°55'E]), June 1984, leg: Győző Horváth. [On the label: Maldives, Kabudu sz., 1984.VII. leg.: Győző Horváth] (HNHM Pseud-2009). Paratypes: 1 male (HNHM Pseud-2010) and 1 female (ZMH-A0003101); all same data as holotype.
The name of the species refers to the obscure evolutionary and geographic origins of the species that is unlikely to have evolved on the young island that is the locus typicus.
Maldive Islands (Fig.
A typical Feaella (Tetrafeaella) habitus (Figs
(Holotype female, paratype male and female). Colour and cuticular surface (in alcohol): sclerotised parts reddish-brown, with reticulated cerotegument (Fig.
Setae : most vestitural setae short, slightly curved, inconspicuous and acuminate.
Chelicera
(Fig.
Pedipalps
(Figs
Feaella (Tetrafeaella) obscura sp. nov, female holotype (HNHM Pseud-2009): SEM images. A. Body, dorsal view; B. Coxal region; C. Coxae I and II with medioposterior depression and coxal spines (primary coxal spines of coxae I highlighted in purple); D. Anal region; E. Carapace, dorsal view; F. Female genital region with pedal coxae IV; G. Right chelal tip, dorsal view; H. Specialised, lanceolate setae (marked with arrow) midway between t and finger tip.
Carapace
: anterior margin with four lobes, the anteromedian lobes are closer to each other than to the anterolateral ones; anterolateral pair approximately as broad as anteromedian pair, anteromedian lobes longer (Figs
Coxal region
(Figs
Legs
(Fig.
Abdomen
: longer than broad, somewhat ovoid; tergites II–IX and sternites IV–X with distinct median suture lines; tergite XI and sternite XI fused; tergite XII and sternite XII (anal sclerites) strongly sclerotised; most segments with numerous setae; tergite XII and sternite XII with two setae; anal region with raised circular rim (Fig.
Genital region
: Female (Figs
Measurements (in mm, ratios in parentheses): Male paratype. Body 1.83. Carapace 0.51/0.41 (1.24×). Chelicera 0.19/0.10 (1.9×), movable finger 0.085. Palpal femur 0.51/0.29 (1.76×), patella 0.41/0.14 (2.93×), chela (with pedicel) 0.53/0.13 (4.08×), chela (without pedicel) 0.50, hand (with pedicel) 0.15, hand (without pedicel) 0.12, movable finger 0.37. Leg I. trochanter 0.12/0.19 (0.62×), femur 0.21/0.06 (3.50×), patella 0.18/0.07 (2.57×), tibia 0.17/0.06 (2.83×), tarsus 0.23/0.05 (4.60×). Leg IV. trochanter 0.22/0.12 (1.83×), femur 0.16/0.08 (2.00×), patella 0.28/0.10 (2.80×), tibia 0.32/0.06 (5.33×), tarsus 0.32/0.05 (6.4×).
Feaella (Tetrafeaella) obscura sp. nov, female holotype (HNHM Pseud-2009): SEM images. A. Left chela, retrolateral view; B. Left chela, dorsomedial view; C. Left chela, ventral view. Male paratype (HNHM Pseud-2010): SEM images. D. Left chela, retrolateral view; E. Left chela, ventral view; F. Left chela, medial view.
Females (holotype, followed by paratype in parentheses and then the ratios also in parentheses). Body 2.16 (2.46). Carapace 0.61/0.48 (0.64/0.50) (1.27–1.28×). Chelicera 0.20/0.12 (0.21/0.12) (1.67–1.75×), movable finger 0.095 (0.10). Palpal femur 0.63/0.37 (0.69/0.40) (1.70–1.73×), patella 0.51/0.18 (0.54/0.19) (2.83–2.84×), chela (with pedicel) 0.60/0.16 (0.61/0.16) (3.75–3.81×), chela (without pedicel) 0.57 (0.57), hand (with pedicel) 0.16 (0.17), hand (without pedicel) 0.12 (0.10), movable finger 0.40 (0.41). Leg I. trochanter 0.15/0.11 (0.16/0.12) (1.33–1.36×), femur 0.24/0.07 (0.27/0.08) (3.38–3.43×), patella 0.22/0.08 (0.21/0.09) (2.33–2.75×), tibia 0.20/0.07 (0.22/0.07) (2.85–3.14×), tarsus 0.22/0.05 (0.22/0.05) (4.4×). Leg IV. trochanter 0.26/0.14 (0.27/14) (1.86–1.93×), femur 0.18/0.10 (0.19/10) (1.8–1.9×), patella 0.36/0.11 (0.37/0.12) (3.08–3.27×), tibia 0.42/0.06 (0.44/0.07) (6.29–7.00×), tarsus 0.36/0.05 (0.38/0.06) (6.33–7.20×).
Feaella (Tetrafeaella) obscura sp. nov. A. Right chelicera, dorsal view – female holotype (HNHM Pseud-2009); B. Right pedipalp, dorsal view – female holotype; C. Left chela, retrolateral view – female holotype; D. Leg I, lateral view – female paratype (ZMH-A0003101); E. Leg IV, lateral view – female paratype; F. Female genital region – female holotype; G. Male genital region – male paratype (HNHM Pseud-2010).
Aside from Feaella (T.) obscura there are twelve species of Feaella (Tetrafeaella): F. (T.) affinis Hirst, 1911 (Seychelles); F. (T.) capensis Beier, 1955, F. (T.) mucronata Tullgren, 1907 and F. (T.) parva Beier, 1947 (all South Africa), F. (T.) indica Chamberlin, 1931 (India and Sri Lanka), F. (T.) leleupi Beier, 1959 (Congo), F. (T.) nana Beier, 1966 comb. nov. (previously treated as a subspecies of capensis but see below), F. (T.) perreti Mahnert, 1982 (Kenya) and the western Australian species F. (T.) anderseni Harvey, 1989, F. (T.) callani Harvey et al., 2016, F. (T.) linetteae Harvey et al., 2016 and F. (T.) tealei Harvey et al., 2016.
Feaella (T.) obscura is most similar in general habitus of carapace and pedipalps and in most characters (see in the key below) to the following species from Africa, India and the Seychelles.
It differs from F. (T.) capensis in having a pronounced and triangular dorsomedial process on the prolateral corner of palpal femur near its base (absent in F. (T.) capensis), conical shape of the frontal carapace lobes (long and triangular), pleural membrane with a dorsal row of 15 and ventral row of 14 platelets (15 and 15 in F. (T.) capensis) (
Feaella (T.) obscura differs from F. (T.) nana in having a pronounced and triangular dorsomedial process on the prolateral corner of the palpal femur near its base (absent in F. (T.) nana). Furthermore, in having pleural membrane with a dorsal row of 15 and a ventral row of 14 sclerotised pleural platelets (in F. (T.) nana the number of these are 14 and 14). In Feaella (T.) obscura on fixed chelal finger isb much closer to ib than to ist and these three trichobothria do not form a straight row, and trichobothrium eb situated clearly closer to the fingertip than to ist (in F. (T.) nana isb, ib and ist are equally placed and form a straight row, and eb is situated midway between ist and the finger tip) (
The new species differs from F. (T.) indica in having a pronounced and triangular dorsomedial process on the prolateral corner of palpal femur near its base (in F. (T.) indica this process is absent). The chelae of F. (T.) obscura are approximately as long as the palpal femora (in F. (T.) indica these are distinctly shorter than the palpal femora). Furthermore, the palpal femur length/width ratio of F. (T.) obscura is 1.70–1.76× (this value is 1.90× in F. (T.) indica) (
In the case of F. (T.) affinis Hirst, 1911 trichobotria sb and st of movable chelal finger are closer to b than t (in the new species sb and st are situated midway between b and t). Furthermore, in F. (T.) affinis trichobothrium ist of fixed chelal finger is at the level of esb and est is placed distal to them (in F. (T.) obscura, ist is equidistant from est and esb) (
The specimens were found in soil samples of the Hungarian Natural History Museum and collected by Mr. Győző Horváth who was a friend of Dr. Sándor Mahunka (former director of HNHM, Department of Zoology) and occasionally collected soil samples for the museum. The collecting label clearly points to the Maldives, however, the island name Kabudu is suspected to be a misspelled form of Kaudu [0°17'N, 73°1'E] or Kandudu islands [2°19'N, 72°55'E]. Mr. Horváth passed away some years ago and no further data are available.
The present-day distribution of Feaellidae has been interpreted as a prime example of continental vicariance (
The present finding is the first record of the Feaellidae from an oceanic island other than the Seychelles which, in contrast to the Maldives, are geologically old and known to support ancient Gondwanan fauna (
While our focus is the description of a new species, the study of relevant literature also reveals inconsistencies in the description of F. (T.) capensis from South Africa. The species was originally described from Cape Point in the Western Cape but
Since Chamberlin’s first key to the family (
1 | All four anterior lobes of carapace with approximately equal width, and placed equidistantly from each other. Presence of a pair of enlarged, thick-walled bursa in male genitalia (Australia) | 2 [F. (T.) anderseni species-group] |
– | Clear differences in length and/or in width of anteromedian and anterolateral lobes of the carapace, and/or in the distance between them | 5 |
2 | Cheliceral rallum present. Pedipalpal femur 1.78–1.91× longer than broad (female); chela with pedicel 0.510–0.580 mm (female) and palpal femur 0.600–0.640 mm (female) | F. (T.) anderseni |
– | Cheliceral rallum absent | 3 |
3 | Trichobothrium t situated distal to sb on movable chelal finger. Pedipalpal femur 1.73× (male) and 1.75–1.79× (female) longer than broad; chela with pedicel 0.555 (male) and 0.645 mm (female) and palpal femur 0.665 (male) and 0.710 mm (female) | F. (T.) tealei |
– | Trichobothria sb and t on movable chelal finger approximately at the same level (same distance from the finger basis) | 4 |
4 | Trichobothrium sb is situated basally to t on movable chelal finger, on fixed finger isb much closer to ib than to ist. Pedipalpal femur 1.77× longer than broad (male). Smaller species, chela with pedicel 0.560 mm (male) and palpal femur 0.575 mm (male) | F. (T.) callani |
– | Trichobothrium sb is situated opposite to t on movable chelal finger, on fixed finger isb equally distant from ib and ist. Pedipalpal femur 2.06× (male) longer than broad. Larger species, chela with pedicel 0.635 mm (male) and palpal femur 0.660 mm (male) | F. (T.) linetteae |
5 | All four anterior lobes of carapace with the same width | 6 |
– | Anterior lobes of carapace with unequal width | 10 |
6 | Anterior lobes of carapace have approximately equal length. Anteromedian lobes much closer to anterolateral ones than to each other. Pedipalpal femur 1.78× longer than broad (South Africa, Swaziland) | F. (T.) mucronata |
– | Anteromedian lobes clearly longer than the anterolateral ones | 7 |
7 | On fixed chelal finger isb, ib and ist are equally placed and form a straight row. Trichobothrium eb is situated midway between ist and the fingertip | 8 |
– | On fixed chelal finger isb much closer to ib than to ist and these three trichobothria do not form a straight row. Trichobothrium eb situated closer to the finger tip than to ist | 9 |
8 | All four anterior lobes of the carapace rather conical, the anteromedian lobes somewhat longer than the anterolaterals. Pedipalpal femur robust, 1.77× (female). Pleural membrane with a dorsal and a ventral row of 14–14 sclerotised pleural platelets. (South Africa) | F. (T.) nana comb. nov. |
– | Anterior lobes of carapace clearly more robust, the anteromedian ones rather triangular, the anterolateral ones conical. The two anteromedian lobes much longer than the anterolateral ones. Pedipalpal femur unusually attenuated, 2.06× (male) longer than broad. Pleural membrane with a dorsal row of 10 and a ventral row of 11 sclerotised pleural platelets. (South Africa) | F. (T.) parva |
9 | Pronounced and triangular dorsomedial process on prolateral corner of palpal femur near its base is absent. All four anterior lobes of the carapace long and triangular, the anteromedian ones somewhat longer than the anterolaterals. Pedipalpal femur 1.66× (female) longer than broad. Pleural membrane with a dorsal and a ventral row of 15–15 sclerotised pleural platelets. (South Africa) | F. (T.) capensis |
– | A pronounced and triangular dorsomedial process on the prolateral corner of palpal femur near its base is present. All four anterior lobes of the carapace robust and rather conical, the anteromedian ones somewhat longer than the anterolaterals. Palpal femur length/width ratio is 1.70–1.73× (female) and 1.76× (male). Pleural membrane with a dorsal row of 15 and a ventral row of 14 sclerotised pleural platelets. (Maldives) | F. (T.) obscura sp. nov. |
10 | Anteromedian lobes are approximately two times wider than the anterolateral ones. Dorsal line of chela concave, approximately at the middle of fixed finger a strong protuberance is present. Pedipalpal femur 1.77–1.86× (female) and 1.80–1.89× (male) longer than broad. (Kenya) | F. (T.) perreti |
– | Anterolateral lobes are clearly wider than the anteromedian ones | 11 |
11 | Anterolateral lobes at least two times broader than anteromedian ones and are flattened at their apical part. Pedipalpal femur 1.80× (female) and 1.61× (male) longer than broad (Democratic Republic of Congo) | F. (T.) leleupi |
– | Anterolateral lobes less than two times broader than anteromedian ones and are triangular or at least rounded at their apical part | 12 |
12 | All four anterior lobes of carapace are placed equidistant from each other. Chelae are approximately as long as the palpal femora. Pedipalpal femur 1.72–1.90× longer than broad. Trichobothrium sb is closer to st than to b on movable chelal finger (Seychelles) | F. (T.) affinis |
– | Anteromedian lobes are closer to each other than to the anterolateral ones. Chelae are distinctly shorter than palpal femora. Palpal femur length/width ratio is 1.90× (female). Trichobothrium sb is situated equidistantly between st and b on movable chelal finger (Bangladesh, India, Sri Lanka) | F. (T.) indica |
The authors thank Dr László Dányi for facilitating access to the HNHM material, and Edit Horváth (HNHM) for assistance in locating the collection data, as well as the collector Mr Győző Horváth. We are grateful for Dr Mark S. Harvey for comparing our specimens against other undescribed species from his collections, and to Mag. Christoph Hörweg for sending critical literature. We are grateful to the reviewers, Dr Mark S. Harvey and Edwin Bedoya-Roqueme, for their valuable comments on the manuscript.