CompCytogen 7(2): 171-190 (2013) COMPARATIVE A veerrerewet open-access over doi: 10.3897/CompCytogen.v7i2.5223 Kan Cyto genetics www.pensoft.net/journals/compcytogen rational Journal of Plant & Animal Cytogenetics, Karyosystematics, and Molecular Systematics Karyotypes of some medium-sized Dytiscidae (Agabinae and Colymbetinae) (Coleoptera) Robert B. Angus!?, Molly J. Clery', Jodie C. Carter', Daniel E. Wenczek' I School of Biological Sciences, Royal Holloway, University of London, Egham Hill, Egham, Surrey TW20 OEX, UK 2 Department of Life Sciences (Entomology), The Natural History Museum, Cromwell Road, London SW7 5BD, UK Corresponding author: Robert B. Angus (r.angus@rhul.ac.uk) Academic editor: Natalia Golub | Received 28 March 2013 | Accepted 29 May 2013 | Published 13 June 2013 Citation: Angus RB, Clery MJ, Carter JC, Wenczek DE (2013) Karyotypes of some medium-sized Dytiscidae (Agabinae and Colymbetinae) (Coleoptera). Comparative Cytogenetics 7(2): 171-190. doi: 10.3897/CompCytogen.v7i2.5223 Abstract An account is given of the karyotypes of 29 species of medium sized Dytiscidae (Coleoptera). Of the 20 species of Agabus Leach, 1817, 18 have karyotypes comprising 21 pairs of autosomes and sex chromosomes which are either X0(@) or XX (Q). These species are A. serricornis (Paykull, 1799), A. labiatus (Brahm, 1791), A. congener (Thunberg, 1794), A. lapponicus (Thomson, 1867), A. thomsoni (J. Sahlberg, 1871), A. confinis (Gyllenhal, 1808), A. sturmii (Gyllenhal, 1808), A. bipustulatus (Linnaeus, 1767), A. nevadensis Hakan Lindberg, 1939, A. wollastoni Sharp, 1882, A. melanarius Aubé, 1837, A. biguttatus (Olivier, 1795), A. binotatus Aubé, 1837, A, affinis (Paykull, 1798), A. unguicularis (Thomson, 1867), A. ramblae Millan & Ribera, 2001, A. conspersus (Marsham, 1802) and A. nebulosus (Forster, 1771). However two species, A. infuscatus Aubé, 1838 and A. adpressus Aubé, 1837, have developed a neo-XY system, with karyotypes comprising 21 pairs of autosomes and XY sex chromosomes (4). No chromosomal differences have been detected between typical A. bipustulatus and A, bipustulatus var. solieri Aubé, 1837, nor have any been found between the three species of the A. bipustulatus complex (A. bipustulatus, A. nevadensis and A. wollastoni). The four species of Colymbetes Clairville, 1806, C. Juscus (Linnaeus, 1758), C. paykulli Erichson, 1837, C. piceus Klug, 1834 and C. striatus (Linnaeus, 1758) have karyotypes comprising 20 pairs of autosomes and sex chromosomes which are XO (4), XX (Q). Two of the species of Rhantus Dejean, 1833, R. exsoletus (Forster, 1771) and R. suturellus (Harris, 1828) have karyotypes comprising 20 pairs of autosomes and X0/XX sex chromosomes, but the other three species, R. grapii (Gyllen- hal, 1808), R. frontalis (Marsham, 1802) and R. suturalis (Macleay, 1825) have 22 pairs of autosomes and X0/ XX sex chromosomes. Agabus congener and Rhantus suturellus may have one B-chromosome. Nine of the spe- cies have previously published karyotype data but for seven of these the data are wrong and are here corrected. Keywords Chromosomes, karyotypes, sex chromosome systems, Dytiscidae, Agabus, Colymbetes, Rhantus Copyright Robert B. Angus et al. This is an open access article distributed under the terms of the Creative Commons Attribution License 3.0 (CC-BY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. ee? Robert B. Angus et al. / Comparative Cytogenetics 7(2): 171-190 (2013) Introduction When Smith and Virkki (1976) compiled their list of beetles whose chromosome numbers were known, they gave data for 2120 species, including 138 named species belonging to the suborder Adephaga. Of these 110 were Carabidae, 21 Dytiscidae and 7 Gyrinidae. By 1984 the number of carabid species whose chromosome num- bers were known had increased to 426 (Serrano and Yadav 1984) and the number of Dytiscidae had reached 32, though five of these were unidentified (Yadav et al., 1984). Interestingly, the total number of world species of Carabidae is given as “more than 40,000” (Wikipedia) while the number for Dytiscidae is about 4080 (Nilsson- Ortmann and Nilsson, 2010), so at this stage the proportion of species for which chro- mosome numbers are listed in the two families is about the same. Data have continued to accumulate, so that Galian and Moore (1994) give the number of carabid species whose chromosome numbers are known as “more than 800”. Numbers for Dytiscidae have also continued to increase. Saleh Ahmed et al. (2000) gave data on 1 species of Hydrovatus Motschulsky, 1 Hydroporus Clairville and 3 Nebrioporus Régimbart (Hy- droporinae), 1 Agabus Leach (Agabinae), 1 Colymbetes Clairville (Colymbetinae) and 1 Eretes Laporte and 1 Hydaticus Leach (Dytiscinae). Aradottir and Angus (2004) gave information on 7 species of //ybius Erichson (Agabinae), Dutton and Angus (2007) described the karyotypes of 7 species of the “Stictotarsus griseostriatus (De Geer) group” (now in the genus Boreonectes Angus) (Hydroporinae), and Tatton and Angus (2011) reported on 30 species related to Deronectes Sharp (Hydroporinae), of which 27 had no previously published data, bringing to total number of dytiscid species with known chromosome numbers to about 82. This gives both the Carabidae and the Dytiscidae as having about 2% of their species with known chromosome numbers. The present paper reports on 20 Agabus species, of which only four had previously published chromosome data (wrong for three of the species), 4 Colymbetes, all of which have previously published data, though for three of the species these data were wrong, and 5 Rhantus of which one species had published data, again wrong. ‘This gives a net increase to over 100 in the number of dytiscid species for which information on chro- mosome numbers are available. The data have been gathered over more than 25 years, and include the results of research projects by three undergraduate students of Royal Holloway, University of London, supervised by R. B. Angus. D. E. Wenczek (1994) studied Rhantus Dejean, J. C. Carter (2001) Rhantus and Colymbetes, and M. J. Clery (2009) made a special study of the Agabus bipustulatus (Linnaeus) species group. Material and Methods The species studied, with their localities of origin, collectors and dates, as well as the number of specimens yielding successful preparations, is given in Table 1. Nomencla- ture and classification follow Nilsson and Hajek (2013, internet version). Where there is more than one locality for a given species the localities from which various prepara- Karyotypes of some medium-sized Dytiscidae (Agabinae and Colymbetinae) (Coleoptera) Table |. Material studied. Species Genus Agabus Leach, 1817 V73 Collector, date | Material Subgenus Agabus s. str. Lindberg, 1939 A, wollastoni Sharp, 1882 MADEIRA: Pico Ariefio A. serricornis (Paykull, 1799) | SWEDEN: VAsTERBOTTEN, Amsele. | A. N. Nilsson, 1990 1d Abies Brakes Et ee eo oe INARENSIS»~ | FRB Auous) 2008" | phesalO Subgenus Acatodes C. G. Thomson, 1859 SCOTLAND oARSTIRE G.N. Foster, 1986 | 204,19 Knockewart Moss A. congener (Thunberg, 1794) Rae a] pap sagt is A.N. Nilsson, 1986 | 2¢4, 19 Sirapsbaken A. lapponicus SWEDEN: VASTERBOTTEN, (Thomson, 1867) Skértraskberget A.N. Nilsson, 1986 | 35d, 19 A. thomsoni NORWAY: FINNMARK EAST, (J. Sahlberg, 1871) Buggynes Pei neueme OES 1d . SWEDEN: VASTERBOTTEN, P A. confinis (Gyllenhal, 1808) WVandlelns Seiveltsdle A.N. Nilsson, 1991 Bao A. sturmii (Gyllenhal, 1808) ENGLAND: Surrey, Chobham R. B. Angus, 1991 14,192 Common A. infuscatus Aubé, 1838 OE ate RUNS NGESSt, R. B. Angus, 2008 14 Bugoynes Subgenus Gaurodytes C. G. Thomson, 1859 ENGLAND: Surrey, Wisley R. B. Angus & M. J. aa3 Common Clery, 2008 HampsHireE, Woolmer Bog R. B. Angus, 2008 BO Gal 2 A. bipustulatus R. B. Angus & M. J. (Linnaeus, 1767) WORCESTERSHIRE, Wyre Forest Clery, 2008 33d FINLAND: EAPPONYS INARENSIS, R. B. Angus, 2008 ig Inari SWEDEN: Norsorten, near Umea} M. Drotz, 1996 1d SWITZERLAND, Vataits, small : ° R. B. Angus, 2008 | 343, 1 A. bipustulatus vax. solieri lake S of Illsee 3 . Aubé, 1837 Vauals, ditch near the Moiry glacier | R. B. Angus, 2008 233 FRANCE: Hautes-Avpes, Guillestre}) M. Drotz, 1998 253 Resta a ea SPAIN: Granapa, Sierra Nevada | M. Drotz, 1999 | 134,19 A. N. Nilsson, 1998 |2 3¢,1 9 ENGLAND: East Sussex, R. B. Angus & M. J. A. melanarius Aubé, 1837 Hindleap Warren Clery, 2008 1¢,19 EGYPT (Saleh Ahmed et al., 2000): | R. Saleh Ahmed & R. ig El Noqra B. Angus, 1994 A. biguttatus (Olivier, 1795) SARDINIA: MeEpio CampIDANO, RBA 1994 ig Giara di Gesturi ee A. binotatus Aubé, 1837 SORSISA ROE uu Corde R. B. Angus, 1993 1d Vizzavona. 174 Robert B. Angus et al. / Comparative Cytogenetics 7(2): 171-190 (2013) Species Locality Collector, date Material A. affinis (Paykull, 1798) rege ee ew R. B. Angus, 1987 1d A. unguicularis (Thomson, |ENGLAND: Norro ik, East Walton R.B. Angus, 1987 2a 1867) Common SPAIN: Hussca, Villanueva de Rayer! oe G3 A. ramblae Millan & Sigena, Barranco del Hospital can 199 5 a Ribera, 2001 a ae cy a Fl urcIA, Ram a e Majada en A. Millan, 1995 19 Pilén A. conspersus (Marsham, 1802) ENGLAND: Hampsuirg, Keyhaven| R. B. Angus, 1993 14 ENGLAND: East Sussex y R. B.A , 1993 1 A. nebulosus (Forster, 1771) Cuckmere Haven oe 3 CANARY ISLANDS: Tengrize | A. N. Nilsson, 1994 | 14,2 99 A. adpressus Aubé, 1837 Ee EA SIOEAS, R.B. Angus, 2008 1d Bugoynes Genus Colymbetes Clairville, 1806 | ENGLAND: Surrey, Wisley R. B. Angus, 2000 ig C. fuscus (Linnaeus, 1758) Common FRANCE: Inprg, Pinail R. B. Angus, 2000 14 SWEDEN: ANGERMANLAND, : C. paykulli Exichson, 1837 Hérngjé, lake Uthdrnsjin DoD Soe 00 || Mabe) ANGERMANLAND, Mullsj6 A. N. Nilsson, 2000 1d : EGYPT (Saleh Ahmed et al., 2000): | R. Saleh Ahmed & R. CPEB, 1084 El Noqra B. Angus, 1994 1d C. striatus (Linnaeus, 1758) Pues CEN ees A. N. Nilsson, 2000 14 Hérnsjé, lake Uthornsjon Genus Rhantus Dejean, 1833 Subgenus Nartus Zaitsev, 1907 Raps (Gyllentalniges). | PO eEeNP a ae Studland, | ieecanus i963" | Bae Subgenus Rhantus s. str. ENGLAND: Dorset, Studland i‘ R. B.A , 1993 1 R. exsoletus (Forster, 1771) Heath eee 3 Norroik, Gayton Thorpe Common| R. B. Angus, 1993 1d ENGLAND: Norro ik, Gayton R. B.A , 1993 1 R. frontalis (Marsham, 1802) Thorpe Common aoe ) Norro.k, Thompson Common R. B. Angus, 1993 Le ENGLAND: Dorset, Studland R.B. Angus, 2000 ig is ei Heath . suturalis (Macleay, 1825) MIpbDLESEX, Staines Moor R. B. Angus, 2000 1d KUWAIT: Ras Az Zawr R. B. Angus, 1996 1d R. suturellus (Harris, 1828) FRANCE: Inprg, Pinail R. B. Angus, 2000 1d ENGLAND: Dorset, Studland R. B. Angus, 1993, 18,299 Heath 2000 , Karyotypes of some medium-sized Dytiscidae (Agabinae and Colymbetinae) (Coleoptera) 175 tions came are given in the figure captions. Otherwise localities are not given apart from in the table. Preparations were made from adult beetles, using mid-gut, testis and ovary, fol- lowing the protocol given by Shaarawi and Angus (1991) and Dutton and Angus (2007). Treatment with colchicine and hypotonic KCl was for 12.5 min in each solu- tion. C-banding was obtained using saturated Ba(OH), at room temperature, followed by incubation in salt-sodium citrate (2 X SSC) at 60° C. Treatment times varied, and the technique evolved over the more than 25 years of the study. If a treatment has been insufficient to produce C-banding, it may be repeated. Initially Angus used to clear the stain with a short immersion in 2X SSC at 60° C, but later found this unnecessary. One set of early experiments with Agabus congener and A. lapponicus was particularly interesting: an initial treatment of 5 min in Ba(OH), proved inadequate. A repeat treatment with 5 min in Ba(OH), produced good centromeric C-bands, but if the second treatment was for 3 min the secondary constrictions were also stained (Fig 1 f, g, and k with the secondary constrictions, Fig. 1 j with just the centromeric C-bands). Chromosome measurements were made on screen and were used for calculating Relative Chromosome Length (RCL), the length of each chromosome expressed as a percentage of the total haploid autosome length in the nucleus. This compensates for differing degrees of chromosome contraction shown in different nuclei. For the Agabus bipustulatus group the RCL data were subjected to statistical analysis using Student’s t-test, but otherwise they are given as approximate values only, to indicate the size rela- tionships of the different pairs of autosomes. Centromere Indices (CI) are not given in detail, but are assigned to their conventional categories. Based on Sumner (2003) the categories are: metacentric-Cl 46-50; submetacentric-CI 26-45; subacrocentric—Cl 16—25; acrocentric—CI 3-15. Results Agabinae Thomson, 1867 Agabus Leach, 1817 Subgenus Agabus s. str. A. serricornis (Paykull, 1799). Fig. 1 a. Published information: none. 2n = 42 + X0 (@). The RCLs of the autosomes range from about 7.6—2.5, with sharp decreases between pairs 5 (RCL about 6.4) and 6 (RCL about 5), 15 (RCL about 4.5) and 16 (RCL about 3.4), and 20 (RCL about 3.1) and 21 (RCL about 2.5). The X chromosome (RCL about 6.4) is similar in size to pairs 4 and 5. Most of the chromosomes are metacentric to submetacentric, with pairs 8-11 subacrocentric and pairs 15 and 20 more or less acrocentric. Pair 12 has a distinct secondary constriction at the base of its short arm. The X chromosome is subacrocentric, with the centromere clearly nearer the end than in autosomes 4 and 5. No C-banded material is available. 176 Robert B. Angus et al. | Comparative Cytogenetics 7(2): 171-190 (2013) 10 11 12 #13 #14 #15 #16 #17 «18 «19 «20 21 XX B {uo uc year r MA ADATL ARAN pg C4 oc BB BK ne O ' DDEICES ECAR ACE HE te cha ae ak ae or ae te asf DDDEVC HL GONE AC ak DEER EE Re has BF Eb 2G 60 rene te | Pi i ii Ter aL LELECRIe Ete e eee ee if wei Ter aL Aagaaa TPIALICeL SO STARA CE Dé 88 cane ACURAGDE DE EG Ab OC 08 Ab Da Fe ab OF ee ts et ne ae oe oe) AP Ln : HAL ELELLL PT CU CCAR PERG AL RP PD be Rae a ae ad ne "1¢) VOM AE SCHUM BAC ga aC RC nu 90 WO ne at at ate ae a8 HM TERELS LALO LOLS ALO LOL eR ee 0} OO TT REAGAN GG BOE Fe dae be 6598 te a8 be ca tees wef DESPARDERR OD MEDD AEE Sb or 8039 te se oe as 2 os or DAYPRPD EDL OLELSD EEE: CE GE PCEE Te aC deat Shae we AC UE DG 6 296 CC ge Be an 58 oe ad ae HO Ge an oo on ae oe D oie § BE OR RGU RA AS Be AN AR BR me Be or me we ns we oe oe ii Miete lets MIS RR REA NR AB RE RE SE RE REA KR al nS BE xe of Pelee PLO ee 1 tate Figure |. Agabus s. str. (a-e) and A. (Acatodes) (f-q), mitotic chromosomes arranged as karyotypes. a A. serricornis, 3, mid-gut, plain b, ¢ A. labiatus, 3, mid-gut b plain c C-banded d, e A. dabiatus, 2, mid-gut d plain, e C-banded f, g A. congener, 4, Scotland, testis, C-banded h A. congener, 2, Sweden, mid-gut, C-banded, with 1 B-chromosome i-k A. lapponicus, , Sweden, testis i plain j, k C-banded l,m A. thomsoni, 4, mid-gut I plain m the same nucleus C-banded n, 0 A. confinis, 2, mid-gut, plain n lacking one X chromosome 0 lacking one replicate each of autosomes | and 2 p A. sturmii, 6, mid-gut, plain q A. infuscatus, 4, mid-gut, plain. Bar = 5um. A. labiatus (Brahm, 1791). Fig. 1 b, c (4), Fig. 1 d, e (2). Published information: none. 2 n = 42 + X0 (3), 42 + XX (9). The autosomes, all either metacentric or submeta- centric, have RCLs ranging from about 7.8—2.7, with a fairly gradual decrease along the Karyotypes of some medium-sized Dytiscidae (Agabinae and Colymbetinae) (Coleoptera) 177 karyotype, though this is slightly sharper between pairs 5 (RCL about 7.1) and 6 (RCL about 5.9) and 11 (RCL about 4.3) and 12 (RCL about 3.8). The X chromosome is submetacentric and the largest in the nucleus (RCL about 9). Pair 5 have secondary con- strictions on the long arm and pair 13 on the short arm. C-banding (Fig. 1 c, e) shows a limited development of centromeric C-bands. These are present on autosomes 1, 3-6, 12, 14 and 17-20. The remaining autosomes, and the X chromosome, lack C-bands. Many of the C-bands are very weak, with the strongest bands present on autosomes 5 and 12. Subgenus Acatodes C. G. Thomson, 1859 A. congener (Thunberg, 1794). Fig. 1 f, g (@), Fig. 1 h (Q). Published information: none. 2 n = 42 + XO (@), 42 + XX (9), 1 B-chromosome. The autosomes, all more or less metacentric, have RCLs ranging from about 7—4, with an even size decrease along the karyotype. The submetacentric X chromosome, RCL about 9, is clearly the longest in the nucleus. All the chromosomes have distinct centromeric C-bands, with some variation in strength between pairs, and autosomes | and 8 have secondary constric- tions which may C-band, especially that on autosome 1. The C-banding reaction of the secondary constriction of autosome 8 is less pronounced, and the constriction may be apparent in only one of the replicates. The Swedish female (Fig. 1 h) has one B-chro- mosome, about as long as autosome | and appearing uniformly partly heterochromatic. A. lapponicus (Thomson, 1867). Fig. 1 i-k (<). Published information: none. 2n = 42 + X0 (4). The karyotype of this species appears indistinguishable from that of A. congener. A. thomsoni (J. Sahlberg, 1871). Fig. 11, m (4). Published information: none. 2n = 42 + X0 (3). The karyotype of this species is very similar to those of A. congener and A. lap- ponicus, but the longest autosome with a secondary constriction is placed as no. 2 as in this material it appears distinctly shorter than the longest autosome (pair 1). It is possible that additional material would show this not to be the case. As in the preceding two species, the secondary constriction on autosome 8 is more conspicuous in one of the replicates. A. confinis (Gyllenhal, 1808). Fig. 1 n, o (Q). Published information: 2n = 40 + “XY” (sex chromosomes not identified) (Smith, 1953). 2n = 44 (Q), probably 42 + XX. The material available for study was three females, and although no intact chro- mosomal complement was obtained, the 43 chromosomes shown in Fig. 1 n exceed the number given by Smith. The suggestion that the X chromosome is the largest in the nucleus is based on comparison with the karyotypes of the three preceding species, all, like A. confinis, members of the A. congener group. In the interpretation given here, Fig. 1 n lacks one X chromosome while Fig. 1 0, from a different specimen, has both X chromosomes but lacks one replicate each of autosomes | and 2. A. sturmii (Gyllenhal, 1808). Fig. 1 p (@). Published information: 2n = 40 + Xy, (Suortti, 1971). 2n = 42 + XO (4), 42 + XX (Q). The autosomes, all either metacentric or submetacentric, have RCLs ranging from about 6.8—2.7. ‘There is a fairly even decrease in length to pair 16 (RCL about 4.8), then a more abrupt decrease to pairs 17—20 (RCL about 3.4) anda further drop to pair 21 (RCL about 2.7). The X metacentric chromosome, 178 Robert B. Angus et al. / Comparative Cytogenetics 7(2): 171-190 (2013) » ‘ w Sa _ + » wo © yo —— 3 ow Figure 2. a, b A. infuscatus testis, first metaphase of meiosis. Bar = 5 um. RCL about 11.5, is by far the longest in the nucleus, almost twice as long as autosome 1. Suortti’s (1971) material consists of first meiotic metaphases obtained by either sectioning or squashing, and is not clear enough to give an accurate assessment of the karyotype. A. infuscatus Aubé, 1838. Figs lq, 2 (4). Published information: none. 2n = 42 + neo XY. The autosomes are nearly all either metacentric or submetacen- tric, but pairs 3 and 17 are subacrocentric. The RCLs of the autosomes range from about 7.9—2.9, and there is a fairly even size decrease along the karyotype, though with slightly sharper decreases between pairs 1 (RCL about 7.9) and 2 (RCL about 6.9), 11 (RCL about 4.3) and 12 (RCL about 3.6), and pairs 18 (RCL about 3.6) and 19 (RCL about 2.9). The subacrocentric X-chromosome (RCL about 7.2) has a distinct gap in its long arm and the Y chromosome, also subacrocentric, is smaller, RCL about 4.6, and matches the X chromosome minus the terminal section of its long arm. ‘This is typical of a neo-XY system where the X chromosome fuses with an autosome to give neo-X, and the same autosome without the X fused to it becomes the neo-Y chromosome. First metaphase of meiosis (Fig. 2) shows 22 bivalents with no suggestion of a B-chromo- some behaving differently from the others. Although it is not possible to identify the neo-XY the behaviour of the chromosomes is entirely consistent with a neo-XY system. Subgenus Gaurodytes C. G. Thomson, 1859 The A. bipustulatus group RCL data for this group are given in Table 2. A. bipustulatus (Linnaeus, 1767). Fig. 3 a-f. Published information: 2n = 40 + Xy (Suortti, 1971). (See comment on Suortti’s work under A. sturmii.) 2n = 42 + X0 (3), Karyotypes of some medium-sized Dytiscidae (Agabinae and Colymbetinae) (Coleoptera) 179 1 2 3 4 5 6 ri 8 9 10 #11 12 13 aim G aim a. elem ee ae » Ht DE di ic ie cee ee ee >) ie eed DY D> dE Eb Ee DP ED G4 Fe 9d ve pe 02 08 24 HD #0 ve te Os Ri@ Rimi e Oe Oe Oe eee ee AQT AL RE HE DB ce tC ot Se ne ae 2 cd be at be pe AG 90 3 18 32 28 as 69 C8 Be ue ee BR ae Be as os es ae xx A@ 80 ES fa D0 Oe os 62 OS Be se ue on ee o8 Be 42 88 08.83 38 25 GS BE Ob sa ce ce 2a BF ae oe os os ee os cz | 00 08 20 28 BE O86 68 we OF TR Oe ee oe oe ee oe oe ee oe on i GP aC PC A) TRUE EC FC me CODE St bb tn tt Oh ce te oe os | ' UKUnM KM Rn ee oo 4) fh ad Al Ab OU DG DD GE OP fe oe nt oe on ae eb ae te te > wv - &=& Ss = as om Mn ee Be Me Ww x - -_— (aan | Oe | | | | Mee ae | im , Ti ee Me ce RAK MER KR OVR ATA wwe F 3 fe | Hf 40 VA dea) de 46 oO) 84d ak G8 08 68 ga Be Oe oe i] 5 um Figure 3. Agabus (Gaurodytes) part 1, the A. bipustulatus group, mitotic chromosomes arranged as karyotypes. a-f A. bipustulatus: a-d 4, Inari, testis a plain b the same nucleus C-banded € plain d the same nucleus C-banded e, f 4, Woolmer, mid-gut e plain f the same nucleus C-banded g—k A. bipustulatus var. solieri: g, hh 3, Moiry, testis g plain h the same nucleus C-banded i-j, k Illsee, @, testis i plain j the same nucleus C-banded K a different nucleus C-banded I, m A. nevadensis, Sierra Nevada, mid-gut, plain, 13,m 9 n, 0A. wollastoni, 3, Madeira, testis, plain; p-s A. melanarius: p, q G, testis p plain q the same nucleus C-banded r, $s &, ovary, r plain, s the same nucleus C-banded. Bar = 5 um. 42 + XX (Q). The X chromosome is the longest in the nucleus, though its RCL value can overlap that of autosome | (Table 2). Autosome 1 is characterised by a secondary constriction in its long arm, frequently picked out by C-banding (Fig. 3 b, d, f). The 180 Robert B. Angus et al. / Comparative Cytogenetics 7(2): 171-190 (2013) Table 2. A. dipustulatus group species, Relative Chromosome Length. Mean, 95% confidence intervals, number of chromosomes measured. Chromosome | A. bipustulatus A. wollastoni | A. melanarius 9.11 8.86 8.25 8.56 9.90 8.07-10.14 | 6.69-11.03 | 6.41-10.09 | 6.66-10.46 | 8.05-10.95 N=14 N=14 N = 10 9.07 8.11 7.20 7.81 8.75 2 8.15—9.99 6.93-9.28 | 6.32-8.08 | 5.61-10.01 | 7.23-10.27 N=14 N=14 N = 10 N=4 8.75 3 POZO N=4 Fie? 4 7.11-8.64 N=4 7.93 7.00 5.75 6.56 7.50 5 7.20-8.65 5.83-8.17 | 4.89-6.61 4.88-8.24 6.58-8.42 N=14 N=14 N = 10 N=4 6.50 6 558-742 N=4 7.25 7 6.22-8.28 N=4 6.50 8 5.58-7.42 N=4 6.25 5.68 4.70 5.44 6.88 9 5.66-6.84 4.64-6.71 | 3.94-5.46 3.87-7.01 6.48-7.27 N=14 N=14 N = 10 N=4 4.94 6.63 10 3,506.38 5.86-7.39 N=8 N=4 4.63 6.63 11 3.35-5.90 5.86-7.39 N=4 5.75 5.29 3.85 4.69 6.38 12 5.23-6.27 4.39-6.18 | 3.26-4.44 3.51-5.87 51 827.57 N=14 N=14 N = 10 N=4 3.95 6.00 13 3.64-4.26 eat 4.16-7.84 6.38 3.75 14 5.37-7.38 3.36-4.14 eae 3.45 6.00 15 2.96-3.94 5.74-6.26 N = 10 N=4 5.04 4.54 3.55 3,44 5.63 16 4345.73 3.66-5.41 | 3.09-4.01 2.59-4.29 4.86-6.39 N=14 N=14 N = 10 N=4 Karyotypes of some medium-sized Dytiscidae (Agabinae and Colymbetinae) (Coleoptera) 181 Chromosome | A. bipustulatus A, wollastoni | A. melanarius 4.79 4.29 3.05 3.25 5.00 4,22-5.35 3.46-5.11 3.00-3.67 ROSA DD 4,745.26 N=14 N=14 495 4.04 3.05 3.13 5.50 18 3.77-4.73 3.21-4.86 2.62-3.48 2.11-4.14 4,586.42 N=14 N=14 N = 10 N=8 N=4 2.70 4.88 19 2.19-3.21 Moto 4.48-5.27 2.50 4.13 20 2.16-2.84 3.72-4.52 N = 10 N=8 N=4 3.25 2.54 2.05 1.87 an75 21 277-373 2.04-3.04 1.62-2.48 [2dr 54 1.95-3.55 N= 14 N= 14 N= 10 =4 11.43 8.86 7.83 8.25 8.33 8.95-13.91 5.69-12.02 6.40-9.27 5.75—-10.75 3.16-13.50 expansion or contraction of this constriction can drastically alter the apparent size of the chromosome (Fig. 3 a, b). The longer chromosomes (pairs 1-10) are submetacen- tric, while the smaller ones are more or less metacentric. The X chromosome is sub- metacentric to subacrocentric. ‘The variation in the apparent size of this chromosome in different nuclei can be striking—it is about twice as long as autosome | in Fig. 3 a, b, but only slightly longer that autosome 1 in Fig. 3 c, d. Since these nuclei are from the same beetle the difference must be the result of different degrees of condensation of the chromosome. A. bipustulatus var. solieri Aubé, 1837. Fig. 3 g—k. Published information: none. 2n = 42 + X0 (4), 42 + XX (Q). All the preparations illustrated are from the Swiss Alps, and are chosen because good plain and C-banded preparations were obtained from the same nuclei. The nuclei shown in Fig. 3 g—j are more condensed than the typical A. b7- pustulatus shown, but the one in Fig. 3 k shows a comparable degree of condensation. These karyotypes show no obvious difference from those of typical A. bipustulatus. The dark area at the end of the X chromosome in Fig. 3 k is where it overlapped one of the autosomes in the preparation. The extreme size difference between the two replicates of autosome | in Fig. 3 g, h is very striking, but C-banding (Fig. 3 h) shows that this size difference is entirely due to the degree of expansion of the secondary constriction. A, nevadensis Hakan Lindberg, 1939. Fig. 3 1, m. Published information: none. 2n = 42 + X0 (4), 42 + XX (Q) The preparations are from old material in R. B. Angus’ archive, and no C-banding is available. The heavy short arm of one replicate of auto- some | in Fig. 3 m is the result of its lying on top of dark material. The sizes and shapes of these chromosomes show no detectable differences from those of A. bipustulatus and A. bipustulatus var. solieri. 182 Robert B. Angus et al. / Comparative Cytogenetics 7(2): 171-190 (2013) A, wollastoni Sharp, 1882. Fig. 1 n, o. Published information: none. 2n = 42 + X0 (4). As with A. nevadensis, this is archive material and no C-banding is available. Only two karyotypes could be obtained, both from rather condensed nuclei, but the general arrangement of the chromosomes is very similar to, if not identical with, those of the species already discussed. A, melanarius Aubé, 1837. Fig. 3 p—s. Published information: none. 2n = 42 + X0 (4), 42 + XX (Q). The general layout of the karyotype is very similar to those of the A. bipustulatus complex described above, but there appear to be more secondary constric- tions. Thus in the female (Fig. 3 s), where the C-banding is better displayed, secondary C-bands are clear in autosomes 1, 3, 6, 7 and 14, and even in the male (Fig. 3 q) the secondary C-bands are clear in autosomes 1, 6 and 14. Other Gaurodytes species A. biguttatus (Olivier, 1795). Fig. 4 a, b. Published information: 2n = 42 + X0 (3), 22 + XX (Q) (Saleh Ahmed et al., 2000). The present material, from both Egypt and Sardinia, confirms the data of Saleh Ahmed et al. We have altered the position of the long chromosome with the secondary constriction from pair No. 3 to pair No. 1 as this matches the Sardinian specimen better, and there is sufficient variation in the RCL of this chromosome, due to opening of the secondary constriction to justify this move. The autosomes are all either metacentric or submetacentric with an even size decrease along the karyotype from RCL about 6 to about 3. The X chromosome has RCL about 6 and is more distinctly submetacentric than the larger autosomes, except of autosome 1 which has the secondary constriction. No C-banded preparation is available. A. binotatus Aubé, 1837. Fig. 4 c. Published information: none. 2n = 42 + X0 (¢). The karyotype of this species appears very similar to that of A. biguttatus, with a similar spread of RCLs. However, autosomes 14—21 are clearly less metacentric than in A. biguttatus, in some cases approaching subacrocentric. The X chromosome, RCL about 8.5, is clearly the largest in the nucleus, thus distinctly larger than in A. biguttatus. A, affinis (Paykull, 1798). Fig. 4 d. Published information: none. 2n = 42 + X0 (4). The RCLs of the autosomes range from about 8—2.7, with an abrupt size decrease between pair 4 (RCL about 7.4) and pair 5 (RCL about 5.4), but otherwise with a gradual decrease. Most to the autosomes are either metacentric or submetacentric, but autosomes 12, 17, 20 and 21 are subacrocentric. The X chromosome is submetacen- tric, RCL about 6. No C-banded material is available. A, unguicularis (Thomson, 1867). Fig. 4 e. Published information: none. 2n = 42 + XO (4). The RCLs of the autosomes range from about 10—2.4. There is an abrupt size decrease between pairs 2 and 3 (RCLs about 9.4 and 7.6) and pairs 3 and 4 (RCL of pair 4 about 6.5), but apart from that the size decrease is fairly even. Most of the autosomes are metacentric or almost so, but a few are clearly submetacentric. The X chromosome, RCL about 6.5, is similar in size to autosome pair 4, but much more clearly submetacentric. No C-banded material is available. Karyotypes of some medium-sized Dytiscidae (Agabinae and Colymbetinae) (Coleoptera) 183 1 2 3 4 5 6 7 8 9 10 11 12 13 14 (eee whee arg 18 19 20 21 x MiG Mis MiBisiBiai Bis BSI eee eee ie me) me eeiae) ee coTt BE S888 BE RE OS SS AB Ry SA ea ke uw Rx ce Bk aR aa an 2s P| BE GG OE Be 26 RE 08 bk ou Be ce me ce ae ae oe oA 88 we ue Rif + bo PR AG CA OO OE ta BK ae UE te ba TE ae ae So bn 8H ue § = es ge PURE ES T0256 82 ag FE U8 Da Gb oe 92 ke ae Bk OS Sa Br ke He } olf ba ff ¥4 2 9T RE OTE FE NZ VE RR UT OS AR be We 4A pa Be 42 Y OG ae 1 GE SR BE US RK as BR BRRS oa ae Aas Be HE SH Hew: Hv [A 38 THO LSiP eC RIE SRE E TS BE eee, kat 37 5% Ne RE £Z OE AR AP AR BE WR AE Tt BA Re Oe A 7 <. se 7? &* DA —) od) Bd ee ee ee ee) ee ee) ee) ee ee | |- Figure 4. Agabus (Gaurodytes) part 2, mitotic chromosomes arranged as karyotypes. a, b A. biguttatus, 3, mid-gut, plain: a El Noqra b Giara di Gesturi; ¢ A. binotatus, 3, mid-gut, plain d A. affinis, 3, mid-gut, plain e A. unguicularis, 3, mid-gut, plain f A. ramblae, 3, Murcia, testis, plain g A. conspersus, 3, mid- gut, plain h, i A. nebulosus, 3, mid-gut, plain h Cuckmere i Tenerife j-l_A. adpressus, 3, mid-gut j plain k, I the same nucleus k plain I C-banded. Bar = 5 um. A. ramblae Millan et Ribera, 2001. Fig. 4 f. Published information: none. 2n = 42 + X0 (4), 42 + XX (2). The RCLs of the autosomes range from about 7—2.9, with a fairly even decrease in length along the karyotype. The autosomes are a mixture of metacentrics and submetacentrics (some at the extreme end of the range), with autosomes 10-12, 15, 16 and 20 subacrocentric. The X chromosome is about the same size as autosome 1, but more clearly submetacentric. No C-banded material is available. A. conspersus (Marsham, 1802). Fig. 4 g. Published information: 2n = 38 + XY (Ya- dav et al., 1984). 2n = 42 + XO (4). The RCLs of the autosomes range from about 6.1— 3.6, with an even decrease in chromosome size along the karyotype. The autosomes are all either metacentric or submetacentric, and autosome 3 has a prominent secondary constriction in its long arm and autosome 15 has what appears to be a terminal NOR at the end of its short arm. The X chromosome, RCL about 5.6, is submetacentric and similar in size to auttosomes 4—6. No C-banded material is available. This karyotype is clearly very different from that reported by Yadav et al. (1984). They report a number of nuclei supporting their conclusions, so the most likely explanation is that they were working with a different species. It may be noted that Marsham (1802) described A. 184 Robert B. Angus et al. / Comparative Cytogenetics 7(2): 171-190 (2013) conspersus from England so the material here may be regarded as true A. conspersus. Yadav et al. worked with Indian material. A, nebulosus (Forster, 1771). Fig. 4 h, i. Published information: none. 2n = 42 + X0 (4), 42 + XX (Q). The general layout of the karyotype in terms of RCLs of the autosomes is very similar to that of A. conspersus. Autosome 3 has a similar secondary constriction in its long arm, but the small chromosome with the terminal apparent NOR is relatively larger than in A. conspersus, and is placed as pair 12 as against 15. The X chromosome, RCL about 7.3, appears relatively larger than that of A. conspersus, and is metacentric. The Tenerife specimen whose chromosomes are shown in Fig. 4 i is of a form whose dark pronotal spots are absent or scarcely apparent, but the chromosomes clearly associate it with the British well-spotted A. nebulosus rather than A. conspersus which lacks the pronotal spots. A. adpressus Aubé, 1837. Fig. 4 j—l. Published information: none. 2n = 42 + XY (4). The autosomes are all either metacentric or submetacentric, with RCLs ranging from about 7.2—3.1 and with an even decrease in size along the karyotype. Autosome 2 has a secondary constriction in its long arm and autosome 8 has one in its short arm. The X chromosome is submetacentric (almost metacentric), about as long as autosome 1. The Y chromosome, RCL about 5, looks like the X chromosome with most of one arm missing. C-banding (Fig. 4 |) shows considerable variation in the centromeric C- bands of the autosomes. Autosome 1 lacks any C-band, 2 and 3 have strong C-bands and 4 has a weak one. Autosome 5 lacks a C-band and that on autosome 6G is very weak. Autosomes 7—9 have strong centromeric C-bands and 10-13 have weaker ones. Pair 14 has very weak bands. Pairs 15—21 have strong C-bands. ‘The secondary constriction of autosome 2 shows as a C-band, but that of autosome 8 appears to be merged with the strong centromeric C-band. The sex chromosomes both have very large strong cen- tromeric C-bands, which is a powerful piece of evidence that this is a neo-XY system rather than an XO system and a B-chromosome. Unfortunately no meiotic preparation is available. Colymbetinae Erichson, 1837 Colymbetes Clairville, 1806 C. fuscus (Linnaeus, 1758). Fig. 5 a, b. Published information: 2n = 35-37 (9) (Giinthert, 1910). 2n = 40 + XO (@). The RCLs of the autosomes range from about 7.8—2.1, with an even decrease in chromosome size along the karyotype. Autosomes 2, 9, 11, 12, 14 and 15 are subacrocentric, while the remainder are more or less metacen- tric. Ihe X chromosome, RCL about 5.7, is metacentric, similar in size to autosome 8. All the chromosomes have distinct centromeric C-bands and autosome 4 has a fainter band, possibly a secondary constriction, in its short arm. C. paykulli Erichson, 1837. Fig. 5 c, d. Published information: 18 pairs includ- ing Xy,? (Suortti, 1971). 2n = 40 + XO (4). The RCLs of the autosomes range from Karyotypes of some medium-sized Dytiscidae (Agabinae and Colymbetinae) (Coleoptera) 185 POMBE A BB PB NS AO UL ofits 1B. THe SPE ASAT a AB'G 18> 20 21 ARK |B me ie Oe ee ee ee ee : ROORCSR PS OS Pee Seis ei eee eee eee a) i L182) 6 ee ee ’ ¢ 1S) miei ee ee ( PIS Pi MOR Ue ee ; Pm) | OR WA G8 O8 UR Ge UR Ak G6 Bk Of We on ae ee oe ne ee ome t USI ee joni DU RRS BS Be an Se 28 8d OK Gt es ae ge ae am as BK as