Cytogenetics of chelicerates (Arthropoda: Chelicerata) Jiří Král Department of Genetics and Microbiology, Faculty of Science, Charles University, Prague 1. Pycnogonida 0 (10) 2. Merostomata 4 (0) 3. Scorpiones 258 (20) 9. Ricinulei 0 (3) 10. Acari 300 (5) 4. Palpigradi 2 (0) 11.Pseudoscorpiones 61 12. Solifugae 0 (20) 13. Opiliones 100 (20) 5. Uropygi 1(10) 6. Schizomida 2 (6) 7. Amblypygi 18 (20) 8. Araneae 835 (200) Chelicerata http://www.arthropodacytogenetics. bio.br/index.html https://www.genomesize.com Current state of chelicerate cytogenetics  karyotypes of chelicerates are not satisfactorily understood  more data on spiders, acariform and parasitiform mites, harvestmen, scorpions and pseudoscorpions; karyotypes of other orders are virtually or completely unknown (in total, karyotypes of nearly 1600 species is described)  Obtained data do not allow to reconstruct karyotype  evolution of chelicerates 97000 1100 0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 Počet druhů všech pavoukovců Počet karyotypovaných druhů Obtained data show considerable diversity of genome size, diploid numbers, karyotype structure, and number of nucleolus organizer regions  considerable diversity of genome sizes from 0.08 (Tetranychus urticae) to 49 pg (Caponia hastifera)  2n range from 4 (acariform mites) to 186 (scorpions). Frequent genome duplications  while some groups exhibit standard (monocentric) chromosomes, other lineages possess holocentric (holokinetic) chromosomes  enormous diversity of modes of sex chromosome determination ancestral arachnids probably without sex chromosomes (or sex chromosomes homomorphic)  considerable diversity of number of nucleolar organizer regions (NORs (1-10), ancestral arachnids probably with 1 NOR locus  insect motive of telomeric repeats except for spiders Metacentric Submetacentric Subtelocentric Akrocentric Monocentric Holocentric Pycnogonida more than 1300 species in 10 families We studied approx. 10 species belonging to several families at our laboratory; their karyotypes consist of many small chromosomes. No information on NORs. Data are not published yet. Ammothella biunguiculata (Ammotheidae) Merostomata 5 species, 1 family four species studied so far, 2n = 20 - 52 Three rounds of genome duplication in ancestors of Merostomata followed by a reduction of chromosome number. Monocentric chromosomes, usually predomination of biarmed chromosomes. No information on NORs. sex chromosomes not differentiated morphologically Solifugae 1100 species, 13 families unpublished data on seven families Ammotrechidae, Daesidae, Eremobatidae, Galeodidae, Gyllippidae, Rhagidiidae, Solpugidae in total 20 species conservative karyotypes low number of monoarmed chromosomes (8-24) Sex chromosomes not differentiated morphologically somatic association of homological chromosomes Ammotrechidae, Daesidae, Eremobatidae, Gyllippidae, Solpugidae acrocentric chromosomes Gluvia dorsalis, male ancestral karyotype 2n = 24 decrease of diploid number by tandem fusions Solpugista sp., male one terminal NOR Galeodidae and Rhagidiidae enormous blocks of heterochromatin predomination of biarmed pairs Paragaleodes sp., male many terminal NORs It is difficult to find these arachnids. A dense population of Eukoenenia spelaea from Ardovská cave (Slovak Carst) allowed to obtain first data on palpigrade chromosomes 1. karyotype consists of 18 tiny chromosomes of similar size, without visible primary constrictions 2. palpigrade chromosomes probably acrocentric 3. sex chromosomes not differentiated morphologically 4. single terminal NOR Palpigradi 80 species, 2 families Acariformes 32 000 species karyotypes described in approx. 200 species, 2n = 4 až 28 holocentric chromosomes A considerable diversity of modes of sex determination sex chromosomes are usually not differentiated morphologically (except for Acarididae, Glyciphagidae - X0 a XY systems) haplodiploidy, parahaploidy (Phytoseiidae), thelytoky, ? deuterotoky in Listrophoridae Parasitiformes more than 12000 species approx. 100 druhů species karyotyped 2n = 6 - 36 monocentric chromosomes predomination of biarmed chromosomes: Argasidae predomination of monoarmed chromosomes: Ixodidae, Opilioacarida considerable diversity of sex determination frequently differentiated sex chromosomes XY (Argasidae, prostriate Ixodidae), X0 (metastriate Ixodidae) haplodiploidy + parahaploidy (Gamasida), thelytoky some thelytokous ixodids polyploid Ricinulei nearly 100 species extant genera Ricinoides, Pseudocellus, Cryptocellus 40-46 monoarmed chromosomes sex chromosomes not differentiated morphologically 1 terminal NOR slow evolution of karyotypes Ricinoides sp., male Cryptocellus narino, male Ricinoides sp.. mitotic metaphase Opiliones 100 karyotyped species, 2n = 10 - 109, ancestral 2n = 30 (Laniatores 25-109, Cyphopthalmi 24-52, Dyspnoi 10-28, Eupnoi 10-36). Laniatores polyploid? monocentric chromosomes, usually predomination of biarmed chromosomes considerable intraspecific and interspecific variability of karyotypes B chromosomes in some species (Psathyropus – up to 18 elements) Karyotype changes: fusions, fissions, pericentric inversions Number of NORs ranges from 1 to 7 Sex chromosomes are not differentiated morphologically or exhibit a low morphological differentiation Most species: XY system some Phalangiidae: probably ♂ZZ/♀ZW (Abraxas) sex chromosomes including NORs In some harvestmen found thelytoky. Thelytokous taxa frequently polyploid more than 6500 species Considerable diversity of number and morphology of chromosomes. Predominatly biarmed chromosomes (except for most Chthoniidae) Pseudoscorpiones Published data on 61 species. Male diploid number 2n♂ = 7 (Olpiidae) – 143 (Atemnidae). Monocentric chromosomes. 3000 species, 27 families Differentiated sex chromosomes: ancestral X0 system (X large metacentric chromosome), neo-sex chromosome systems XY (Neobisiidae, Larcidae) Olpium palipes 2n♀ = 8, XX Lasiochernes pilosus 2n♂ = 61, X0 Chthoniidae – achiasmatic meiosis in males Chthonius litoralis (2n♂ = 35, X0) pachytene postpachytene metaphase I metaphase II anaphase II 0,00 0,05 0,10 0,15 0,20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 X 0,00 0,05 0,10 0,15 0,20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 X 0,00 0,05 0,10 0,15 0,20 0,25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 X 0,00 0,05 0,10 0,15 0,20 0,25 1 2 3 4 5 6 7 8 9 10 X Chthonius (E.) fuscimanus Chthonius (E.) tetrachelatus Chthonius (E.) sp. 1 Chthonius (E.) sp. 2 ? ? Hypothesis on karyotype evolution of European chthoniids Neobisiidae: Roncus – centric fusions. Neobisium – multiple fusions (macrochromosomes) Atemnus politus (Atemnidae): 2n = 95, X0 Heterozygotes for reciprocal translocations prophase I - 42 bivalents, X chromosome 1 tetravalent, 1 hexavalent Neobisium sylvaticum Neobisium erythrodactylum Roncus transsilvanicus Species with XY system Scorpiones Buthidae: holocentric chromosomes (2n = 5 – 56) Other scorpions: monocentric chromosomes (2n = 28 – 186), usually predomination of biarmed chromosomes, more than 250 species from 11 families studied so far, 2n = 5 – 186, usually one terminal NOR. more than 2100 species up to 22 families Opisthacanthus asper (Liochelidae) Tityus magnimanus (Buthidae) Sex chromosomes not differentiated morphologically male meiosis achiasmatic, female meiosis ? postpachytene metaphase I metaphase/anaphase I metaphase II A considerable interspecific and intraspecific diversity o karyotypes, a frequent occurrence of multiple reciprocal translocations in populations Chaerilus celebensis metaphase I C. rectimanus metaphase I In heterozygotes, chromosomes involving translocations form chains or circles during meiotic division Pedipalpi: Amblypygi, Uropygi a Schizomida Amblypygi 220, Thelyphonida 124, Schizomida approx. 300 species Published data include 18 amblypygids,1 thelyphonid, and 2 schizomids. We dispose unpublished data on approx. other 40 species. Monocentric chromosomes. Amblypygi and Thelyphonida: considerable interspecific diversity of karyotypes (Amblypygi 2n = 22-86, Uropygi 28-78), in most species 2n > 50. Low number of terminal NORs (1-3) Amblypygids and uropygids with a high diploid numbers: Predomination of monoarmed chromosomes Charon grayi, ♂ (Charontidae, Amblypygi) 2n = 70 metaphase II Decrease of diploid number in many lineages Accompanied by increase of number of biarmed pairs: centric fusions Total number of chromosome arms changed during decrease of 2n: involvement of pericentric inversions Phrynichus deflersi arabicus (Phrynichidae, Amblypygi), ♂, 2n = 30, metaphase II sex chromosome detection Comparative genomic hybridization ♂ ♀ sex chromosome system ♂XY/♀XX Paraphrynus mexicanus Thelyphonus cf. linganus male metaphase I note hetetomorphic bivalent XY Damon medius, male Senegal: 2n = 70 Togo: 2n = 72 Schizomida Stenochrus sp., male Clavizomus sp., male very low chromosome numbers (2n = 16 – 22) usually predomination of acrocentric chromosomes diffuse stage diplotene Mesothelae (0,2% of spiders) Mygalomorphae (6% of spiders) Haplogynae (10% of spiders) Entelegynae (83% of spiders) Araneomorphae Araneae Pedipalpi 130 families nearly 50 000 species 2n♂= 10 - 49 acrocentric chromosomes 2n♂ = 5 - 128 high diploid numbers predomination of monoarmed chromosomes 2n♂= 14 - 132 usually predomination of biarmed chromosomes 2n♂= 5 - 152 predomination of biarmed chromosomes except for Dysderoidea (holocentric chromosomes) Opisthothelae Paracoelotes birulai (Agelenidae): 2n♂ = 42 (metaphase II) Ancestral karyotype of entelegyne spiders Decrease of diploid numbers by cycles of centric fusions and pericentric inversions or tandem fusions these rearrangements do not change acrocentric morphology • centric fragments – remnants of tandem fusions Stegodyphus africanus (Eresidae) Tegenaria fuesslini (Agelenidae), 2n♂ = 22 (metaphase II) Karyotype saturated by biarmed chromosomes pericentric inversions or centric fusions  usually high diploid numbers (14-132)  predomination of biarmed chromosomes  considerable interspecific diversity of karyotypes Grammostola rosea (Theraphosidae) 2n♂ = 72, mephase II Mygalomorphs A high proportion of acrocentric autosomal pairs in mygalomorphs with highest diploid numbers Poecilotheria formosa (Theraphosidae) 2n♂ = 110 metaphase II Probably reflect frequent centric fissions of biarmed chromosomes Entelegyne spiders Systems ♂X1X2/♀X1X1X2X2 (X1X20), ♂X1X2X3/♀X1X1X2X2X3X3 (X1X2X30), ♂X1X2X3X4/♀X1X1X2X2X3X3X4X4 (X1X2X3X40) most frequent X1X20 system specific behaviour during male meiosis Most spiders exhibit multiple X chromosome systems inactivation, pairing in parallel, without recombinations segregation to the same pole association of sister chromatids pachytene anaphase I junction lamina Avicularia minatrix (Theraphosidae) Ischnocolus jickelii (Theraphosidae) 2n♂ = 85, X1X2X30 metaphase II 2n♂ = 78, X1X2X3X40 metaphase II metaphase I X1 X2 X3 metaphase I Macrothele calpeiana, male 118 +X1X2X3X4X5X6X7X8X9X10X11X12X13X140 Macrothele (Macrothelidae) Macrothele gigas X1X2X3X4X5X6X7X8X9X10X11X12X130 System X0  found at all major spider clades  arose independently many times by centric or tandem fusions between X chromosomes X Oecobius navus metaphase I Poecilomigas sp., male karyotype (32 + X) 2n♂ = 18 + X Nondisjunctional hypothesis White 1940, Postiglioni and Brum-Zorrilla 1981 mitosis second meiotic division Origin of multiple X chromosomes in spiders unique behaviour of multiple X chromosomes in female germline standard segregation nondisjunctions X1X1 X2X2 X1X1 X2X2 X1X1 X2X2 X1X1 X2X2 XY leptotene pachytene  probably ancestral for araneomorph spiders  found in seven families of haplogyne spiders  specific chromosome structure and meiotic pairing  ancestral X1X2Y system formed by two large metacentric X chromosomes and metacentric Y microchromosome  specific end-to-end pairing during male meiosis Y X1X2Y system diplotene interphase Loxosceles spinulosa Holocnemus caudatus XY X0 X1X20 Smeringopus ndumo metaphase I X Wugigarra sp. metaphase I Kambiwa neotropica metaphase I X1X2X3X4Y metaphase I X1 X2 X2 X1 C proto-X proto-Y sex chromosome pair pair of homomorphic sex chromosomes associated with multiple X chromosomes or X1X2Y system spermatogonial metaphase Holothele cf. longipes, male female premeiotic interphase X1X1X2X2X3X3X4X4 Poecilotheria formosa Porrhothele sp., male, mitotic metaphase Sex chromosomes of avicularioid mygalomorphs spermatogonial prophase Nops, metaphase I C. natalensis, metaphase I C. hastifera, metaphase I C. natalensis C. hastifera ancestral sex chromosome system X1X2Y genome duplication in caponiids including sex chromosomes Nops C. natalensis C. hastifera sex chromosome pairing 2n = 152 2n = 128 Atypus affinis male karyotype: 14 + XY original X X Y neo X neo Y autosome pair Spider systems including Y chromosome: fusion of X chromosome and an autosome found at all primary spider clades Leptoneta infuscata male karyotype: 12 + XY heterobivalent Delena cancerides (Sparassidae) X1X2X3X4X5Y1Y2Y3Y4 system An odd metacentric chromosome at mitotic metaphases of male indicates a complex sex chromosome system including Y Chromosome. Karyotype analysis revealed X1X2X3X4X5Y system. 1. Male karyotype consists of 39 acrocentric and one large metacentric chromosome, female karyotype comprises 44 acrocentrics Analysis of neo-sex chromosome system in Tegenaria ferruginea (Agelenidae) 2. Analysis of the metaphase I: chromosomes X1, X2 a X3 are original multiple X chromosomes. Their meiotic behaviour is the same as behaviour of multiple X chromosomes in closely related species. 3. Analysis of anaphase I: segregation of 22 acrocentrics (including chromosomes X1,X2 and X3) to one pole and 17acrocentrics and metacentric chromosome to another pole. Transmission electron microscopy Evolution of nucleolar organizing regions  ancestral pattern 1 terminal NOR locus  NORs usually terminal, placed on autosomes  in haplogynes frequently on sex chromosomes (involvement into sex chromosome pairing)  enormous NORs of mygalomorphs in spiders discovered first in Dysdera crocata (Dysderidae) (Díaz and Sáez 1966) synapomorphy of the haplogyne superfamily Dysderoidea Ancestral male karyotype of Dysderoidea: 2n♂ = 7, X0 Holokinetic chromosomes  autosomes: frequent fusions and fissions of chromosomes  in some species number of autosomes doubled in comparison with closely related species  comparison of genome size: concerted fission of all chromosomes (agmatoploidy) Dysdera spinicrus 2n♂ = 23, X0 Dysdera westringi 2n♂ = 45, X0 Sex chromosome fissions frequent event in spiders with holokinetic chromosomes 2n♂ = 32 + X1X2X3X4X5X6X7 D. simoni D. aff. crocata 2n♂ = 20 + X1X2X3X4X5 Some clades of Dysderoidea exhibit a considerable karyotype diversity. Closely related species shows frequently very different karyotypes Enormous diversity in Dysdera (2n♂ = 7 – 42): detection of cryptic species, suitable model to study role of chromosome changes in speciation Dysdera catalonica 2n♂ = 9, X0 D. undecima 2n♂ = 11, X0 D. quindecima 2n♂ = 15, X0 Silhouettella loricatula (Oonopidae) D. dubrovninnii metaphase II metaphase II