Research Article |
Corresponding author: Martin Forman ( formivelkejpan@seznam.cz ) Academic editor: Marielle Schneider
© 2020 František Šťáhlavský, Martin Forman, Pavel Just, Filip Denič, Charles R. Haddad, Vera Opatova.
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:
Šťáhlavský F, Forman M, Just P, Denič F, Haddad CR, Opatova V (2020) Cytogenetics of entelegyne spiders (Arachnida, Araneae) from southern Africa. Comparative Cytogenetics 14(1): 107-138. https://doi.org/10.3897/CompCytogen.v14i1.48667
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Spiders represent one of the most studied arachnid orders. They are particularly intriguing from a cytogenetic point of view, due to their complex and dynamic sex chromosome determination systems. Despite intensive research on this group, cytogenetic data from African spiders are still mostly lacking. In this study, we describe the karyotypes of 38 species of spiders belonging to 16 entelegyne families from South Africa and Namibia. In the majority of analysed families, the observed chromosome numbers and morphology (mainly acrocentric) did not deviate from the family-level cytogenetic characteristics based on material from other continents: Tetragnathidae (2n♂ = 24), Ctenidae and Oxyopidae (2n♂ = 28), Sparassidae (2n♂ = 42), Gnaphosidae, Trachelidae and Trochanteriidae (2n♂ = 22), and Salticidae (2n♂ = 28). On the other hand, we identified interspecific variability within Hersiliidae (2n♂ = 33 and 35), Oecobiidae (2n♂ = 19 and 25), Selenopidae (2n♂ = 26 and 29) and Theridiidae (2n♂ = 21 and 22). We examined the karyotypes of Ammoxenidae and Gallieniellidae for the first time. Their diploid counts (2n♂ = 22) correspond to the superfamily Gnaphosoidea and support their placement in this lineage. On the other hand, the karyotypes of Prodidominae (2n♂ = 28 and 29) contrast with all other Gnaphosoidea. Similarly, the unusually high diploid number in Borboropactus sp. (2n♂ = 28) within the otherwise cytogenetically uniform family Thomisidae (mainly 2n♂ = 21–24) supports molecular data suggesting a basal position of the genus in the family. The implementation of FISH methods for visualisation of rDNA clusters facilitated the detection of complex dynamics of numbers of these loci. We identified up to five loci of the 18S rDNA clusters in our samples. Three different sex chromosome systems (X0, X1X20 and X1X2X30) were also detected among the studied taxa.
Karyotype, sex chromosomes, meiosis, rDNA FISH, NOR, acrocentric, Gnaphosoidea, Araneoidea, Oecobioidea, RTA clade
With nearly 50000 species, spiders represent the second largest order of arachnids (
Based on their cytogenetic characteristics, spiders can be assigned into several groups displaying different dynamics of karyotype evolution. Their assignment into these groups correlates with the parcelling of spider diversity into the main evolutionary lineages. The basal groups Mesothelae (2n♂ = 80 or 96) (
Compared to haplogyne and mygalomorph spiders, the karyotypes of entelegynes are considerably less diversified. Their respective interfamilial diploid number (2n) ranges are low (2n♂ = 10–52, average 27), and the majority of species possess exclusively acrocentric chromosomes (
A prominent feature of spider karyotypes is the presence of unusual sex chromosomes. The majority of species display the X1X20 system (male: X1X2, female: X1X1X2X2), which is considered to be an ancestral state in spiders (
Due to the conservative aspects of karyotype features in entelegynes, our knowledge of chromosomal evolution in this group could be broadened by the implementation of molecular cytogenetic approaches. Because of the limited number of banding techniques available for invertebrates, the fluorescence in situ hybridization (FISH) for visualisation of nucleolus organizer regions (NORs) is a convenient choice in terms of methodology. The NORs are composed of clusters of genes coding most of the rRNA, namely major rDNA loci (18S, 5.8S and 28S rRNA genes). The application of FISH in spider chromosome studies is scarce (
Southern Africa includes three of the 36 global biodiversity hotspots (
In this study, we analysed the karyotypes of 38 species representing 16 entelegyne families (Araneoidea, Oecobioidea and RTA clade groups) from South Africa and Namibia, to gain knowledge about entelegyne cytogenetics from this biogeographical region. Additionally, we analysed major rDNA clusters via FISH in 11 species. Our results also address the status of Prodidominae and the overall composition of Gnaphosoidea, which highlights the utilization of cytogenetic methods as an important tool to bring additional perspectives for the study of entelegyne taxonomy and systematics. We use the molecular phylogenetic framework and classification established in
Specimen and locality data of 55 entelegyne samples (38 species) analysed in this study are reported in Table
List of examined species, including summary of the cytogenetic data: 2n of male, chromosome morphology (A = completely acrocentric), sex chromosome system, length ratio of sex chromosomes (N = number of measured nuclei) and number of NOR loci. Locality data (EC – Eastern Cape; FS – Free State; MP – Mpumalanga; NAM – Namibia; NL – KwaZulu-Natal; NP – National Park; WC – Western Cape; ZA – South Africa) and sample size (m mature male, sm submature male). * = unidentifiable specimens.
Family/species | 2n | Chromosome morphology | Sex chromosome system | X ratio (N) | Number of 18S rDNA loci | Locality | GPS (S/E) | Sample size |
---|---|---|---|---|---|---|---|---|
I. Araneoidea | ||||||||
Tetragnathidae | ||||||||
Pachygnatha sp. | 24 | A | X1X20 | 1:0.96 (8) | – | ZA-MP: God‘s Window | 24.8747, 30.8910 | 1m |
Theridiidae | ||||||||
Argyrodes cf. convivans Lawrence, 1937 | 21 | A | X0 | – | 4 | NL: Tembe | 27.0276, 32.4083 | 1m |
Argyrodes sp. | 21 | A | X0 | – | – | NL: Ndumo | 26.8749, 32.2109 | 2m |
Theridion cf. purcelli O. P.-Cambridge, 1904 | 22 | A | X1X20 | 1:0.80 (6) | – | NL: Pongola Reserve | 27.3601, 31.9848 | 1m |
II. Oecobioidea | ||||||||
Hersiliidae | ||||||||
Hersilia sericea Pocock, 1898 | 35 | A | X1X2X30 | 1:0.92:0.71 (9) | – | NL: Vernon Crookes | 30.2749, 30.6092 | 1m |
Neotama corticola (Lawrence, 1937) | 33 | A | X1X2X30 | 1:0.89:0.76 (10) | – | ZA-EC: Port St. Johns | 31.5977, 29.5346 | 1m |
Oecobiidae | ||||||||
Oecobius navus Blackwall, 1859 | 19 | A | X0 | – | – | ZA-EC: Hogsback | 32.5914, 26.9303 | 2m |
Oecobius putus O. P.-Cambridge, 1876 | 25 | A | X1X2X30 | – | – | ZA-FS: Bloemfontein | 29.0949, 26.1621 | 2m |
III. RTA - non-Dionycha | ||||||||
Ctenidae | ||||||||
Ctenus cf. pulchriventris (Simon, 1896) | 28 | A | X1X20 | 1:0.86 (14) | – | ZA-MP: Sudwala Caves | 25.3713, 30.6965 | 2m |
Oxyopidae | ||||||||
Peucetia striata Karsch, 1878 | 28 | A | X1X20 | 1:0.84 (4) | – | ZA-FS: Bloemfontein | 29.0488, 26.2152 | 1m |
Sparassidae | ||||||||
Olios sp. | 42 | A | X1X20 | 1:0.93 (20) | 1 | NL: Ndumo | 26.8749, 32.2109 | 1sm |
Sparassinae sp. cf. Olios | 42 | A | X1X20 | 1:0.93 (20) | 4 | NAM: south of Etosha | 19.6208, 15.8858 | 1sm |
Thomisidae | ||||||||
Borboropactus sp. | 28 | A | X1X20 | 1:0.76 (5) | – | NL: Pietermaritzburg | 29.6050, 30.3462 | 1sm |
Xysticus sp. | 23 | A | X0 | – | – | NL: Ndumo | 26.8749, 32.2109 | 2sm |
IVa. RTA clade Dionycha - “Prodidomidae Simon, 1884, Prodidominae (sensu |
||||||||
Prodidomus simoni Dalmas, 1919 | 29 | A | X1X2X30 | 1:0.94:0.91 (7) | – | NL: Ndumo | 26.8855, 32.3124 | 4m |
Theuma sp. | 28 | A | X1X20 | 1:0.68 (12) | – | ZA-FS: Bloemfontein | 29.04876, 6.2152 | 1sm |
IVb. RTA - Dionycha Part A - (Gnaphosoidea sensu lato, ( |
||||||||
Ammoxenidae | ||||||||
Ammoxenus amphalodes Dippenaar & Meyer, 1980 | 22 | A | X1X20 | ? | – | ZA-FS: Bloemfontein | 29.0986, 26.1550 | 1m |
Ammoxenus psammodromus Simon, 1910 | 22 | A | X1X20 | 1:0.86 (4) | – | ZA-FS: Bloemfontein | 29.0986, 26.1550 | 1m |
Gallieniellidae | ||||||||
Austrachelas natalensis Lawrence, 1942 | 22 | A? | X1X20 | 1:0.80 (8) | – | NL: Ithala Reserve | 27.5426, 31.2824 | 1m |
Gnaphosidae | ||||||||
Camillina maun Platnick & Murphy, 1987 | 22 | A | X1X20 | 1:0.90 (4) | – | NL: Cornationweg | 27.6946, 31.0609 | 1m |
Camillina maun Platnick & Murphy, 1987 | 22 | A | X1X20 | 1:0.92 (11) | NL: Manzengenya | 27.2361, 32.7076 | 2m | |
Zelotes fuligineus (Purcell, 1907) | 22 | – | X1X20 | 1:0.94 (7) | – | NL: Cornationweg | 27.6946, 31.0609 | 1m |
Zelotes sclateri Tucker, 1923 | 22 | A | X1X20 | 1:0.82 (10) | 2 | NL: Ithala Reserve | 27.5426, 31.2824 | 2m |
Zelotes sclateri Tucker, 1923 | 22 | A | X1X20 | 1:0.88 (10) | – | NL: Ndumo | 26.8855, 32.3124 | 1m |
Zelotes sp. | 22 | A | X1X20 | 1:0.85 (8) | – | NL: Ndumo | 26.8854, 32.3124 | 1sm |
Trachelidae | ||||||||
Afroceto plana Lyle & Haddad, 2010 | 22 | A | X1X20 | 1:0.85 (23) | 1 | NL: Ndumo | 26.8855, 32.3124 | 2m |
Trochanteriidae | ||||||||
Platyoides walteri (Karsch, 1887) | 22 | A | X1X20 | 1:0.93 (10) | 3 | NL: Royal Natal NP | 28.7101, 28.9336 | 1m, 1sm |
IVc. RTA clade - Dionycha Part B | ||||||||
Cheiracanthiidae | ||||||||
Cheiramiona kirkspriggsi Lotz, 2015 | 24 | A | X1X20 | 1:0.77 (6) | 1 | NL: Ithala Reserve | 27.5426, 31.2824 | 1m |
Salticidae | ||||||||
Baryphas ahenus Simon, 1902 | 28 | A | X1X20 | 1:0.98 (7) | – | NL: Tembe | 27.0276, 32.4083 | 1sm |
Cyrba lineata Wanless, 1984 | 28 | A | X1X20 | 1:0.95 (16) | – | NL: Ndumo | 26.8749, 32.2109 | 2m |
Holcolaetis zuluensis Lawrence, 1937 | 28 | – | X1X20 | 1:0.76 (4) | – | NL: Ndumo | 26.8855, 32.3124 | 1m |
Myrmarachne laurentina Bacelar, 1953 | 28 | – | X1X20 | 1:0.84 (6) | – | NL: Ndumo | 26.8855, 32.3124 | 1m |
Menemerus minshullae Wesołowska, 1999 | 28 | A | X1X20 | 1:53 (7) | – | NL: Ndumo | 26.8749, 32.2109 | 1m |
Nigorella hirsuta Wesołowska, 2009 | 28 | A | X1X20 | 1:0.92 (7) | – | ZA-FS: Bloemfontein | 29.0483, 26.2112 | 1m |
Thyene ogdeni Peckham & Peckham, 1903 | 28 | A | X1X20 | 1:0.89 (10) | – | NL: Tembe | 27.0276, 32.4083 | 1m |
Thyenula haddadi Wesołowska, Azarkina & Russell-Smith, 2014 | 28 | A | X1X20 | 1:0.90 (16) | 2 | NL: Royal Natal NP | 28.6909, 28.9415 | 1m |
Thyenula leighi (Peckham & Peckham, 1903) | 28 | A | X1X20 | 1:0.84 (10) | – | NL: Ophathe | 28.3742, 31.3898 | 1m |
Selenopidae | ||||||||
Anyphops sp.* | 26 | A | X1X20 | 1:0.77 (8) | – | ZA-WC: Mossel Bay | 34.1634, 22.1065 | 1m |
Anyphops sp.* | 26 | A | X1X20 | 1:0.75 (9) | 4 | NL: Ndumo | 26.8749, 32.2109 | 1sm |
Selenops sp. 1* | 26 | A | X1X20 | 1:0.78 (19) | 4 | NL: Pongola Reserve | 27.3602, 31.9848 | 1sm |
Selenops sp. 1* | 26 | A | X1X20 | 1:0.76 (34) | – | NL: Ophathe | 28.3937, 31.3942 | 1sm |
Selenops sp. 2* | 29 | A | X1X2X30 | 1:0.94:0.87 (15) | 1 | NAM: Omuthiya | 18.3770, 16.6005 | 1 m |
Chromosomes were documented with an ORCA-AG monochromatic camera (Hamamatsu) on an Olympus IX81 microscope operated by Cell^R. Standard karyotype characteristics, such as number, relative size, and morphology of the chromosomes, were analysed from photographs using the LEVAN plugin (
Major rDNA clusters were detected by FISH, with the 18S rDNA probe, as described in
We obtained cytogenetic data for 38 species of entelegyne spiders belonging to 16 families (Table
The superfamily Araneoidea comprises more than 15 families of ecribellate orb-weavers (
Tetragnathidae Menge, 1866
Tetragnathidae is a species-rich family with a cosmopolitan distribution, with 25 species represented in South Africa (
Chromosomes of Tetragnathidae (A–D) and Theridiidae (E–L). Pachygnatha sp. (2n♂ = 24, X1X20) A mitotic metaphase B late pachytene with positively heteropycnotic sex chromosomes C diakinesis D half of metaphase II, with slightly less condensed X chromosomes. Argyrodes cf. convivans (2n♂ = 21, X0) E mitotic metaphase F diakinesis with isopycnotic X univalent G half of metaphase II with despiralised acrocentric X chromosome. Argyrodes sp. (2n♂ = 21, X0) H mitotic metaphase I diakinesis with isopycnotic X chromosome. Theridion cf. purcelli (2n♂ = 22, X1X20) J diplotene, X1X2 associate on the periphery of the plate K metaphase II L anaphase II. Arrowheads indicate sex chromosomes. Scale bars: 5 μm.
Theridiidae Sundevall, 1833
This cosmopolitan and diverse family includes about 57 South African species (
Alongside the families Uloboridae and Deinopidae, the superfamily Oecobioidea (comprising families Hersiliidae and Oecobiidae) forms the so-called “UDOH grade” (
Hersiliidae Thorell, 1870
Hersiliids are a small family distributed in the tropics and subtropics. Twelve species have been reported from South Africa (
Chromosomes of Hersiliidae (A–F) and Oecobiidae (G–L). Hersilia sericea (2n♂ = 35, X1X2X30) A mitotic metaphase B early metaphase I, X1X2X3 shows slightly positive heteropycnosis C metaphase II, note positively heteropycnotic X1X2X3. Neotama corticola (2n♂ = 33, X1X2X30) D early diakinesis, sex chromosomes E half of anaphase I with despiralised sex chromosomes F quarter of anaphase II with despiralised sex chromosomes. Oecobius putus (2n♂ = 25, X1X2X30) G mitotic metaphase H half of anaphase I with positively heteropycnotic sex chromosomes. O. navus (2n♂ = 19, X0) I mitotic metaphase J pachytene with compact X K diakinesis X univalent shows positive heteropycnosis L metaphase I with already isopycnotic X. Arrowheads indicate sex chromosomes. Scale bars: 5 μm.
Oecobiidae Blackwall, 1862
The cosmopolitan family Oecobiidae consists of about a hundred species, of which five can be found in South Africa (
RTA clade
The RTA clade comprises lineages united by the presence of the retrolateral tibial apophysis on the male palps (
Here we studied four non-Dionycha lineages, namely three families belonging to the Oval calamistrum clade (Ctenidae, Oxyopidae and Thomisidae) and the family Sparassidae.
Ctenidae Keyserling, 1877
Wandering spiders are distributed worldwide, except for New Zealand (
Chromosomes of Ctenidae (A–B), Oxyopidae (C–E), Sparassidae (F–J) and Thomisidae (K–P). Ctenus cf. pulchriventris (2n♂ = 28, X1X20) A pachytene, X1X2 associate on the periphery of plate B diakinesis. Peucetia striata (2n♂ = 28, X1X20) C mitotic metaphase D metaphase I E metaphase II, sex chromosomes isopycnotic. Olios sp. (2n♂ = 42, X1X20) F mitotic metaphase G pachytene H late diakinesis I metaphase II J Diakinesis of Sparassinae sp. cf. Olios (2n♂ = 42, X1X20). Borboropactus sp. (2n♂ = 28, X1X20) K mitotic metaphase L metaphase I M half of metaphase II without sex chromosomes. Xysticus sp. (2n♂ = 23, X0) N mitotic metaphase O metaphase I, note early segregation of one bivalent P prometaphase II. Arrowheads indicate sex chromosomes. Scale bars: 5 μm.
Oxyopidae Thorell, 1870
Lynx spiders comprise more than 450 species distributed all over the world, of which 41 species have been recorded from South Africa (
Currently, 26 species belonging to five genera have been analysed cytogenetically (
Sparassidae Bertkau, 1872
Huntsman spiders, represented by 56 species in South Africa (
Thomisidae Sundevall, 1833
Crab spiders represent a diverse cosmopolitan family, with more than 130 species known from South Africa (
Dionycha, the two-clawed spiders, are a diverse group comprising about 17 families, representing a third of known spider species diversity. The group received moderate support in
Albeit with limited sampling, the phylogenomic analyses recovered the group as monophyletic, with its subdivision into two main clades concordant with the “Dionycha part A” and “Dionycha part B” (
The position of prodidomines remains uncertain. In molecular analyses, they were placed as a sister lineage to all remaining Dionycha (
We analysed two species, Theuma sp. and Prodidomus simoni Dalmas, 1919, representing two formerly recognized prodidomid subfamilies, Theuminae and Prodidominae, respectively (
Chromosomes of Prodidominae (Dionycha). Theuma sp. (2n♂ = 28, X1X20) A mitotic metaphase B early pachytene with positively heteropycnotic X1X2 C diakinesis, note a difference in size of sex chromosomes D half of late metaphase II with sex chromosomes. Prodidomus simoni (2n♂ = 29, X1X2X30) E mitotic metaphase F pachytene note positively heteropycnotic X1X2X3 G metaphase I H early metaphase II, note positively heteropycnotic sex chromosomes. Arrowheads indicate sex chromosomes. Scale bars: 5 μm.
Altogether, we analysed nine species from five families belonging to this clade, and provide the first insights into the karyotypes of Ammoxenidae and Gallieniellidae. Several of the families analysed here, namely Ammoxenidae, Gallieniellidae and Trochanteriidae, were not recovered as monophyletic in previous molecular and morphological phylogenetic analyses, and formed a grade of lineages within the Gnaphosoidea (
Ammoxenidae Simon, 1893
Ammoxenidae is a small family of termitophagous spiders, currently comprising four genera and 18 species distributed across southern Africa and Australia (
Chromosomes of Ammoxenidae (A–E) and Gallieniellidae (F–H). Ammoxenus psammodromus (2n♂ = 22, X1X20) A mitotic prometaphase B pachytene C metaphase I with slightly negatively heteropycnotic X1X2 D half of anaphase II including sex chromosomes. A. amphalodes (2n♂ = 22, X1X20) E metaphase I. Austrachelas natalensis (2n♂ = 22, X1X20) F mitotic anaphase, orientation of chromatids suggests acrocentric morphology of chromosomes G pachytene X1X2 shows strong positive heteropycnosis H early metaphase I with already isopycnotic sex chromosomes. Arrowheads indicate sex chromosomes. Scale bars: 5 μm.
Gallieniellidae Millot, 1947
Recent molecular analyses cast doubts on the monophyly of this family, splitting the group into two lineages with uncertain placement within “Dionycha part A” clade (
Gnaphosidae Pocock, 1898
Gnaphosidae is a diverse family with a cosmopolitan distribution. We analysed four species belonging to the genera Camillina Berland, 1919 and Zelotes Gistel, 1848, both belonging to the subfamily Zelotinae. The males of all species displayed a diploid number of 22 chromosomes and X1X20 sex chromosome system (Fig.
Chromosomes of Gnaphosidae (A–H), Trachelidae (I–L) and Trochanteriidae (M–P) A diakinesis of Camillina maun (2n♂ = 22, X1X20). Zelotes fuligineus (2n♂ = 22, X1X20) B late mitotic metaphase C diakinesis, X1X2 show positive heteropycnosis. Z. sclateri (2n♂ = 22, X1X20) D mitotic metaphase E pachytene, sex chromosomes pair in parallel on the periphery of nucleus F diakinesis G metaphase II, sex chromosomes are nearly isopycnotic H mitotic metaphase of Zelotes sp. (2n♂ = 22, X1X20). Afroceto plana (2n♂ = 22, X1X20) I mitotic metaphase J pachytene, X1X2 show parallel association K diakinesis L half of metaphase II with sex chromosomes. Platyoides walteri (2n♂ = 22, X1X20) M mitotic metaphase N pachytene, sex chromosome associate by their centromeric regions O diakinesis, with positively heteropycnotic sex chromosomes P half of prometaphase II with sex chromosomes. Arrowheads indicate sex chromosomes. Scale bars: 5 μm.
Trachelidae Simon, 1897
Trachelids, recently elevated to family level (
Trochanteriidae Karsch, 1879
Trochanteriidae is another gnaphosoid family with a mainly Gondwanan distribution, but also extending to East Asia. In South Africa, the family is represented by nine species of the genus Platyoides O. Pickard-Cambridge, 1891 (
Following the results of
Cheiracanthiidae Wagner, 1887
The family, restored by
Chromosomes of Cheiracanthiidae (A–D) and Salticidae (E–P). Cheiramiona kirkspriggsi (2n♂ = 24, X1X20) A mitotic metaphase B pachytene, sex chromosomes associate on the periphery of nucleus C diakinesis with positively heteropycnotic X1X2 D metaphase II E Baryphas ahenus, (2n♂ = 28, X1X20) prometaphase II. Cyrba lineata (2n♂ = 28, X1X20) F diakinesis G metaphase II. Holcolaetis zuluensis (2n♂ = 28, X1X20) H mitotic metaphase I diakinesis, with positively heteropycnotic X1X2. Myrmarachne laurentina (2n♂ = 28, X1X20) J mitotic metaphase K early metaphase I, note one bivalent with early segregation (arrows) L Menemerus minshullae (2n♂ = 28, X1X20) diakinesis, note one bivalent with early segregation (arrows) M Diakinesis of Nigorella hirsuta (2n♂ = 28, X1X20) N Metaphase II of Thyene ogdeni (2n♂ = 28, X1X20) X1X2 are positively heteropycnotic O Thyenula haddadi (2n♂ = 28, X1X20) diakinesis P Thyenula leighi (2n♂ = 28, X1X20) diakinesis. Arrowheads indicate sex chromosomes. Scale bars: 5 μm (A–D), 10 μm (E–P).
The genus Cheiracanthium Koch, 1839, closely related to Cheiramiona Lotz & Dippenaar-Schoeman, 1999 (
Salticidae Blackwall, 1841
Jumping spiders are the most diverse spider family, with about more than 6100 species globally and 350 species distributed in South Africa (
We analysed nine species of South African salticids. Consistent with the majority of published data, we found a 2n♂ = 28, X1X20 system in all of the species analysed in this study, namely Baryphas ahenus Simon, 1902 (Fig.
Selenopidae Simon, 1897
Selenopids can be considered a smaller family, distributed in the tropics and subtropics (
Chromosomes of Selenopidae. Anyphops sp. (Mossel Bay) (2n♂ = 26, X1X20) A mitotic metaphase B pachytene, note close association of sex chromosomes C diakinesis D metaphase II, note positive heteropycnosis of X chromosomes. Selenops sp. 1 (Ophathe) (2n♂ = 26, X1X20) E mitotic metaphase F pachytene, note close association of X1X2 G diakinesis H metaphase II. Selenops sp. 2 (Namibia) (2n♂ = 29, X1X2X30) I mitotic metaphase J pachytene, note close association of X1X2X3 K metaphase I L half of metaphase II with sex chromosomes. Arrowheads indicate sex chromosomes. Scale bars: 5 μm.
Chromosomes of Ctenidae (A), Ammoxenidae (B), Gnaphosidae (C, D), and Salticidae (E–I). Ctenus cf. pulchriventris (2n♂ = 28, X1X20) A prometaphase II. Ammoxenus amphalodes (2n♂ = 22, X1X20) B two metaphases II. Camillina maun (2n♂ = 22, X1X20) C metaphase II. Zelotes sp. (2n♂ = 22, X1X20) D metaphase II. Menemerus minshullae (2n♂ = 28, X1X20) E metaphase I F metaphase II. Nigorella hirsuta (2n♂ = 28, X1X20) G metaphase II. Thyenula haddadi (2n♂ = 28, X1X20) H metaphase II, one sister cell with sex chromosomes. Thyenula leighi (2n♂ = 28, X1X20) I diakinesis. Arrowheads indicate sex chromosomes. Scale bars: 10 μm.
Interestingly, only the data obtained from the Namibian specimen, namely the 2n and the sex chromosome system, were comparable to karyotypes described in three other karyotyped selenopids (
We applied 18S rDNA FISH on 11 species from eight different families, including: i) one araneoid (Fig.
Chromosomes of entelegyne spiders from South Africa after FISH with 18S rDNA probe (red signal). Arrows point on bivalents with signals (A, E, G, H, J), certain chromosomes with signals (B, C, F, I, K, L), or certain signals (D) A Argyrodes cf. convivans (Theridiidae), diplotene B Argyrodes cf. convivans, half of metaphase II (without sex chromosomes), note distal (opposite centromere) positions of loci C Olios sp. from South Africa (Sparassidae), metaphase II, one sister cell without sex chromosomes, note distal position of locus D Olios sp. from Namibia (Sparassidae), metaphase II, signals at distal parts of acrocentric chromosomes E Afroceto plana (Trachelidae), diplotene F Zelotes sclateri (Gnaphosidae), mitotic metaphase G Platyoides walteri (Trochanteriidae), diplotene H Cheiramiona kirkspriggsi (Cheiracanthiidae), pachytene, with distal signal on one bivalent I Thyenula haddadi (Salticidae), metaphase II, distal signals on two chromosome pairs J Anyphops sp. (Mossel Bay) (Selenopidae), diplotene K Selenops sp. 1 (Pongola Reserve) (2n♂ = 26) (Selenopidae), metaphase II, two sister cells L Selenops sp. 2 (Selenopidae), half of metaphase II. Arrowheads indicate sex chromosomes, where distinguished. Scale bars: 5 μm.
In some cases, we found a different number of loci in members of the same family. Namely, two South African representatives of Selenopidae (Selenops sp. 1 Ophathe/Pongola and Anyphops sp. Ndumo/Mossel Bay) displayed four distal loci (Fig.
The position of major rDNA loci has previously been examined in a limited number of entelegynes, namely in one lycosid species (
Our cytogenetic results from southern African entelegynes fit with our knowledge of the general trends in karyotype diversification of the group. Compared to other major clades of spiders (
In case of Araneoidea, our results from Pachygnatha and Theridion showed the typical karyotype conservatism in both Tetragnathidae and Theridiidae. On the other hand, Argyrodes (Theridiidae) displayed chromosomal rearrangements unusual for entelegynes.
In comparison to other Entelegynae families, Oecobioidea karyotypes represented a dynamic system. Hersiliidae, despite limited data availability for only four species (
Despite the rare utilization of cytogenetic markers in Entelegynae phylogenetics, the results presented in this paper could have an implication for the group’s systematics. The RTA clade represents the most diversified group of entelegynes. The non-dionychan members of the RTA clade analysed in this paper showed a broad range of diploid numbers in entelegynes with acrocentric chromosomes. The 2n of examined sparassids ranked among the highest in entelegynes, neighbouring the proposed ancestral state for the group (2n♂ = 42,
All representatives of the superfamily Gnaphosoidea analysed in this paper displayed the same karyotype of 22 acrocentric chromosomes and X1X20, which confirmed that such a constitution is widespread not only within Gnaphosidae, but also among the other Gnaphosoidea families. Despite the limited data, higher 2n has not been found in any species of Gnaphosidae, Ammoxenidae, Gallieniellidae and Trochanteriidae (see
Our results of the Dionycha part B clade taxa confirm the 2n conservatism within the families Salticidae and Cheiracanthiidae. On the other hand, a substantial variability was observed in Selenopidae. Both Selenops and Anyphops individuals from South Africa share karyotype features, namely: 2n♂ = 26, X1X20 and four 18S rDNA loci, while Selenops sp. 2 from Namibia possesses 2n♂ = 29, X1X2X30 and a single 18S rDNA locus.
This study improves our knowledge about entelegyne karyotypes and brings new information about taxa from an understudied biogeographical region. The data proceeding from South Africa and Namibia are consistent with the information available for entelegyne karyotypes from other continents. Here, we confirmed the stability of the karyotype characteristics, namely acrocentric morphology, the prevalence of X1X20, and relatively small ranges of 2n in most families. On the other hand, we found variability of 2n within the families Hersiliidae, Oecobiidae, Gnaphosidae, Selenopidae and Thomisidae. Our cytogenetic data challenge the current placement of Prodidomidae as an internal group of Gnaphosidae, although admittedly further taxa should be analysed to resolve this conundrum, and thus highlight the utility of cytogenetics for taxonomy and systematics. Our study expands our knowledge about major rDNA loci distribution in the Entelegynae, and reveals surprising variability in the number of loci among certain taxa.
We are grateful to Jan-Andries Neethling for technical support during the field trips. We also thank to an anonymous reviewer and Douglas Araujo for valuable comments and suggestions that improved this paper. The present study was supported by Czech Republic Ministry of Education, Youth and Sports grant SVV 260 434 / 2019 to P.J. and SVV-260 314 to M.F. and F.D., Grant Agency of the Charles University 92218 to M.F., Czech Science Foundation 16-10298S to M.F. and F.D., Charles University Research Centre program No. 204069 to V.O., and grants from the National Research Foundation of South Africa in the Knowledge Interchange and Collaboration programme (#97495 and #105318) and Competitive Funding for Rated Researchers programme (#95569) to C.R.H. Microscopy was performed in the Laboratory of Confocal and Fluorescence Microscopy, co-financed by the European Regional Development Fund and the state budget of the Czech Republic, project no. CZ.1.05/4.1.00/16.0347 and CZ.2.16/3.1.00/21515. South African specimens were collected under the following collecting permits: OP 4072/2016 from Ezemvelo KZN Wildlife (KwaZulu-Natal Province), MPB. 5582 from the Mpumalanga Park Board (Mpumalanga Province), NC.614/2017 from the Free State Department of Economic, Small Business Development, Tourism and Environmental Affairs (Free State Province), AAA007-00174-0056 from CapeNature (Western Cape Province), and CRO 4/15CR and CRO 5/15CR from the Eastern Cape Department of Economic Development and Environmental Affairs (Eastern Cape Province). Namibian species were sampled under permit 1400/2009.