Mastozoología Neotropical ISSN: 0327-9383 [email protected] Sociedad Argentina para el Estudio de los Mamíferos Argentina
Souza, Ana L. G.; Corrêa, Margaret M. O.; Pessôa, Leila M. The first description of the karyotype of Dasyprocta azarae Lichtenstein, 1823 (rodentia, Dasyproctidae) from Brazil Mastozoología Neotropical, vol. 14, núm. 2, julio-diciembre, 2007, pp. 227-233 Sociedad Argentina para el Estudio de los Mamíferos Tucumán, Argentina
Available in: http://www.redalyc.org/articulo.oa?id=45714206
How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Mastozoología Neotropical, 14(2):227-233, Mendoza, 2007 ISSN 0327-9383 ©SAREM, 2007 Versión on-line ISSN 1666-0536 www.sarem.org.ar THE FIRST DESCRIPTION OF THE KARYOTYPE OF Dasyprocta azarae LICHTENSTEIN, 1823 (RODENTIA, DASYPROCTIDAE) FROM BRAZIL
Ana L. G. Souza1, 2, Margaret M. O. Corrêa2 and Leila M. Pessôa2
1 Programa de Pós-graduação em Zoologia, Museu Nacional, Quinta da Boa Vista, São Cristóvão, CEP: 20940-040, Rio de Janeiro, Brasil
ABSTRACT: The karyotype of Dasyprocta azarae has not been described previously. In this article we describe the karyotype of D. azarae from Northern Pantanal, Mato Grosso, Central Brazil. D. azarae has a diploid number 2n=64 and a number of autosomal arms NA=122. The 2n and NA are the same as those reported for other Brazilian species of Dasyprocta, but differ in chromosome morphology. Differences in the sex chromosomes were also found. The Y chromosome is acrocentric whereas in other Dasyprocta species is metacentric or submetacentric. The C-banding pattern coincides with that described for other species, except for pair six, having two bands of heterochromatin. The NOR patterns revealed intraindividual variation, with 1 to 6 NOR chromosomes. In the other species of Dasyprocta the NOR is present in only 1 pair. Although few data about morphological variation is available and restricted to color pattern, the small chromosomal differences observed among species of Dasyprocta are however, capable to differentiate taxa of the genus.
RESUMEN: Primera descripción del cariotipo de Dasyprocta azarae Lichtenstein, 1823 (Rodentia, Dasyproctidae) de Brasil. En este artículo se describe por primera vez el cariotipo de D. azarae procedente del norte del Pantanal, Mato Grosso, Brasil. La especie posee un número diploide 2n=64 y un número de brazos autosómicos NA=122. Los resultados para 2n y NA son los mismos que los encontrados para otras especies brasileñas de Dasyprocta, pero difieren en la morfología cromosómica. También fueron identificadas diferencias en los cromosomas sexuales. El cromosoma Y es acrocéntrico en ésta, mientras que en otras especies del género es metacéntrico o submetacéntrico. El patrón de bandas C es igual al descrito para otras especies, con la excepción del par seis, que presenta dos bandas de heterocromatina. Los patrones NOR demuestran variación interespecífica, con uno a seis cromosomas marcados con NORs. En otras especies de Dasyprocta el NOR está presente en apenas un par. Aunque hay poca información disponible sobre variación morfológica, restringida al patrón de color, las pequeñas diferen- cias cromosómicas entre especies de Dasyprocta son, sin embargo, capaces de diferen- ciar taxas del género.
Key words. Caviomorpha. C-banding. Conventional staining. Dasyprocta azarae. NOR.
Palabras clave. Bandas C. Caviomorpha. Coloración convencional. Dasyprocta azarae. NOR.
Recibido 12 abril 2006. Aceptación final 12 abril 2007. 228 Mastozoología Neotropical, 14(2):227-233, Mendoza, 2007 ALG Souza et al. www.sarem.org.ar
INTRODUCTION tional Giemsa staining. The chromosomes were measured and classified according to Levan et al. The family Dasyproctidae Bonaparte, 1838, (1964) as follows: metacentric (M), submetacen- belongs to the suborder Hystricognathi and tric (SM) and subtelocentric (ST) chromosomes were considered biarmed and acrocentric chromo- contains two genera: Dasyprocta Illiger, 1811, somes uniarmed. Silver nitrate staining, following with 11 species, and Myoprocta Thomas, 1903, the procedures of Howell and Black (1980), was with two species (Woods, 1993). The species- used to detect the nucleolus organizer regions level recognition within Dasyprocta is prob- (NORs). C-bands were revealed by Sumner’s lematic because of morphologically interme- (1972) techniques. diate forms and high intra-specific variation (Matson and Shump, 1980; Lima and RESULTS Langguth, 1998; Ximenes, 1999). The genus is distributed from southern The three specimens of D. azarae had a dip- Mexico to northern Argentina. In Brazil, there loid number 2n=64 and number of autosomal are five species (Woods, 1993): D. azarae arms NA=122. The chromosome complement Lichtenstein, 1823; D. fuliginosa Wagler, (Fig. 1) consisted of 30 pairs of biarmed chro- 1832; D. leporina (Linnaeus, 1758); D. mosomes and one pair of uniarmed chromo- prymnolopha Wagler, 1831 and D. punctata somes. Pairs 1 to 15 and 19 to 29 were meta- Gray, 1842. The karyotypes of all Brazilian centric chromosomes, pairs 16, 17 and 18 were species, with exception of D. azarae, are submetacentric, pair 30 was subtelocentric, and known and their diploid and autosomal num- pair 31 was acrocentric. The X chromosome bers have been described (George and Weir, was a medium-sized metacentric similar in size 1974; Kasahara and Yonenaga-Yassuda, 1984; to pair 6. The Y chromosome was a small Lima and Langguth, 1998; Ramos et al., 2003). acrocentric, the smallest chromosome of the Literature on D. azarae includes only the dip- complement. loid number (Lima and Langguth, 1998), nei- C-bands of varying sizes were observed in ther autosomal number nor a complete descrip- the pericentric region of all autosomes (Fig. tion of the karyotype has been published. 2). Heterochromatin was also observed in the Here, we provide the first complete descrip- pericentric region of the X chromosome. No tion of the karyotype, the C-banding and NOR heterochromatin was observed in the Y chro- chromosomes of D. azarae and compare them mosome. Pair 6 showed two bands of consti- with data on other Brazilian species within the tutive heterochromatin in the pericentromeric genus. region and in the interstitial region of the long arm. MATERIALS AND METHODS NORs were always observed in the telomeric Specimens were collected with Tomahawk field region of the autosomes. There was traps in a private reserve (Reserva Particular do intraindividual variation in the number of Patrimônio Natural SESC-Pantanal) in Barão de NOR-bearing chromosomes in all specimens Melgaço, Mato Grosso State, Central Brazil (16o analyzed (Fig. 3). We found from one to six 28’ 24.9” S and 16o 48’ 43.6” S; 56o 01’ 37.6” W NORs, with a modal number of three. and 56o 28’ 49.4” W). Fur color was used to iden- tify specimens according to Ximenes (1999). DISCUSSION Voucher specimens (two males and one female) were deposited in the mammal collection of the Museu Nacional, Rio de Janeiro, Brazil: MN64090, The diploid number (2n=64) and the number MN64487, and MN64616. of autosomal arms (NA=122) found for D. Mitotic chromosomes were obtained by the azarae coincided with that of the other four method of Ford and Hamerton (1956). In the labo- Brazilian species within the genus (George and ratory, 287 metaphases of the three specimens were Weir, 1974; Kasahara and Yonenaga-Yassuda, analyzed under a light microscope using conven- 1984; Lima and Langguth, 1998). In a recent THE KARYOTYPE OF Dasyprocta azarae 229
Fig. 1. Conventionally stained male karyotype of D. azarae (2n=64, NA=122) (M - metacentric; SM - submetacen- tric; ST - subtelocentric; A - acrocentric).
Fig. 2. C-banding karyotype of a male specimen of D. azarae. 230 Mastozoología Neotropical, 14(2):227-233, Mendoza, 2007 ALG Souza et al. www.sarem.org.ar
chromosome is a medium metacentric, as in D. aguti, but the other species presents a large metacentric or submetacentric X chromosome. The Y chromosome is a small acrocentric chromosome, but the Y chromosome of the other species is always metacentric or sub- metacentric. Summary karyotype data for the species of Dasyprocta are shown in Table 1. The C-bands in D. azarae are the same as in other species (Table 1). Nevertheless, the other species of Dasyprocta presents hetero- chromatin in the Y chromosome whereas in D. azarae it is absent (Lima and Langguth, 1998; Ramos et al., 2003). Pair 6 in D. prymnolopha, D. leporina and Dasyprocta sp. has only one block with an increased amount of heterochromatin (Lima and Langguth, 1998; Ramos et al., 2003). This result on pair 6 in- dicates that a pericentric inversion has prob- ably occurred in this region in D. azarae. According to Ramos et al. (2003), the basic pattern for the distribution of constitutive het- erochromatin in the genus includes a small block in pair six, as occurs in the karyotype of D. fuliginosa from Brazilian Amazon. Nucleolus organizer regions (NORs), were observed in the telomeric region of chromo- somes in D. azarae, as in the other species of Fig. 3. Metaphase cells of D. azarae with Ag-NOR Dasyprocta. However, we observed a) with one NOR-bearing chromosome; b) with two NOR-bearing chromosome; c) with three intraindividual variation from one to six NOR- NOR-bearing chromosome; d) with four NOR- bearing chromosomes in all specimens here bearing chromosome; e) with five NOR-bear- analyzed (Fig. 3). This variation included the ing chromosome; f) with six NOR-bearing acrocentric pair, the only pair marked for chromosome. Scale bars = 10µm. NORs in the other species of the genus so far (Ramos et al., 2003) (Table 1). The acrocen- tric pair was the pair most frequently marked study, including four species from the Brazil- with silver nitrate in this study. ian Amazon, Ramos et al. (2003) found nu- These techniques stain only NORs activated merical variation from 2n=64 to 65 due to the during the previous interphase, so that the presence of one supernumerary chromosome. differences in the number of stained NORs The chromosome composition in D. azarae per cell may reflect differences in the number was different from that of the other species: of active NORs (Thiriot-Quiévreux and Insua, the latter have a larger number of submeta- 1992; Galleti et al., 1995). Although this poly- centrics (five to nine pairs) and subtelocentrics morphism in the number of active NOR sites (three to four pairs) (George and Weir, 1974; per cell commonly occurs in other groups of Lima and Langguth, 1998; Ramos et al., 2003), rodents (Yonenaga-Yassuda et al., 1992; whereas D. azarae has a higher number of Svartman and Almeida, 1993; Lima et al., metacentric chromosomes (26 pairs). The sex 2003), in the suborder Hystricognathi the pat- chromosomes also differ in D. azarae. The X tern has until now been constant (Yonenaga- THE KARYOTYPE OF Dasyprocta azarae 231
Table 1 Summary of karyotype data of the genus Dasyprocta. Acronyms read as follows: M: metacentric; SM: submetacentric; A: acrocentric; * no information; · variable number depending on supernumerary chromo- somes; Pc: Pericentromeric; T: terminal; NOR: nucleolar organizer regions; Ref.: References, as follows: 1. Kasahara and Yonenaga-Yassuda (1984); 2. Lima and Langguth (1998); 3. Ramos et al. (2003); 4. Present study.
Supernu- Tnaxa 2ANXY CR-Bands NsO Lfocalitie Re merary
D. azarae 6***4 a*bsen t *S1ão Paul o
Pc: all chromosomes Paraíba X: pericentromeric and Rio D. aguti 624 1MM2 absen t * 2 Y: totally Grande do heterochromatic Norte
D. fuliginosa 624 1M2 S*a*bsen t *R2ondôni a
Rio D. prymnolopha 624 1M*2 a*bsen t * Grande do 2 Norte
Pc: all chromosomes Short X: pericentromeric Brazilian D. prymnolopha 64/65 · SMM SM1 arm; pair 3 Y: pericentromeric Amazon 31 region
Pc: all chromosomes Short Brazilian D. fuliginosa 64/65 · S*M 1S MX: pericentromeric arm; pair 3 Amazon Y: * 31
Pc: all chromosomes Short X: pericentromeric Brazilian D. leporina 64/65 · SMM SM1 arm; pair 3 Y: almost totally Amazon 31 heterochromatic
Pc: all chromosomes Short X: pericentromeric Brazilian Dasyprocta s5p 64/6 · SMM SM1 arm; pair 3 Y: almost totally Amazon 31 heterochromatic
Pc: all chromosomes, Short pair 6 Pc and T arm; 1 to Mato D. azarae 624 1MA2 absen tX: pericentromeric 6 4 Grosso Y: without chromo- heterochromatin somes 232 Mastozoología Neotropical, 14(2):227-233, Mendoza, 2007 ALG Souza et al. www.sarem.org.ar
Yassuda et al., 1985; Leal-Mesquita et al., LITERATURE CITED 1992; Pessôa et al., 2004). The diploid number (2n=64) and the num- FORD CE and JL HAMERTON. 1956. A colchicine ber of autosomal arms (NA=122) of hypotonic citrate squash sequence for mammalian chromosomes. Stain Technology 31:247-251. Dasyprocta are considered high for the subor- GALLETI PM, CA MESTRINER, PJ MONACO, and der Hystricognathi (George and Weir, 1974). EM RASCH. 1995. Post-zygotic modifications and Dasyproctidae and Caviidae are the most ho- intra and inter-individual nucleolar organizing re- mogeneous groups of the suborder gion variations in fish: report of a case involving Leporinus friderici. Chromosome Research 3:285- Hystricognathi, with a high number of meta- 290. centric chromosomes (George and Weir, 1974). GEORGE W and J WEIR. 1974. Hystricomorph chro- The difference in the number of metacentric mosomes. Symposium of the Zoological Society of chromosomes in D. azarae is probably due to London 34:79-108. HOWELL WM and DA BLACK. 1980. Controlled sil- a rearrangement, with deletion or duplication ver-staining of nucleolus organizer regions with a of genetic material. The same has probably protective colloidal developer: a 1-step method. occurred to the X chromosome. However, in Experientia 36:1014-1015. the Y-chromosome, besides deletion or dupli- KASAHARA S and Y YONENAGA-YASSUDA. 1984. A progress report of cytogenetic data on Brazilian cation, pericentric inversions are also involved. rodents. Revista Brasileira de Genética 7(3):509-533. These questions might be resolved if new LEAL-MESQUITA ER, Y YONENEGA-YASSUDA, TH samples were available for G-band analysis. CHU, and PLB ROCHA. 1992. Chromosomal char- Despite the differences observed in chro- acterization and comparative cytogenetic analysis of two species of Proechimys (Echimyidae, Rodentia) mosome composition between D. azarae and from the caatinga domain of the State of Bahia, the other Brazilian species, the general pattern Brazil. Caryologia 45(2):197-212. found for 2n and NA is the same. The fact LEVAN A, K FREDGA, and AA SANDBERG. 1964. that they share the same diploid number and Nomenclature for centromeric position on chromo- somes. Hereditas 52:201-220. autosomal number corroborates the hypothesis LIMA FS and A LANGGUTH. 1998. The karyotypes of that the species of Dasyprocta have a conser- three Brazilian species of the genus Dasyprocta vative karyotype. (Rodentia, Dasyproctidae). Iheringia Serie Zoologia Although few data about morphological 85:141-145. LIMA FS, CR BONVICINO, and S KASAHARA. 2003. variation is available and restricted to color A new karyotype of Oligoryzomys (Sigmodontinae, pattern, the small chromosomal differences Rodentia) from Central Brazil. Hereditas 139:1-6. observed among species of Dasyprocta (C- MATSON JO and KA SHUMP. 1980. Intrapopulation banding, NOR, and the Y chromosome) are variation in cranial morphology in the agouti, Dasyprocta punctata (Dasyproctidae). Mammalia however, capable to differentiate taxa of the 44(4):559-570 genus. PESSÔA LM, MMO CORRÊA, JA OLIVEIRA, and MOG LOPES. 2004. Karyological and morphomet- ACKNOWLEDGMENTS ric variation in the genus Thrichomys (Rodentia: Echimyidae). Zeitschrift für Säugetierkunde 69(4):258-269. The authors would like to thank L. Brandão, and staff of RAMOS RSL, WG VALE, and FL ASSIS. 2003. Karyo- R.P.P.N. SESC Pantanal. This work has been funded by typic analysis in species of the genus Dasyprocta grants from SESC (Serviço Social do Comércio), (Rodentia: Dasyproctidae) found in Brazilian Ama- Universidade Federal do Rio de Janeiro. L. M. Pessôa zon. Annals of the Brazilian Academy of Sciences has been partially supported by a fellowship from 75(1):55-69. Conselho Nacional de Desenvolvimento Científico e SUMNER AT. 1972. A simple technique for demon- Tecnológico (CNPq- 301386-927). We thank Dr. strating centromeric heterochromatin. Experimental Guilherme Muricy for a critical review of a preliminary Cell Research 75:304-306. version of the manuscript; Dr. C. J. Tribe from Cam- SVARTMAN M and EJC ALMEIDA. 1993. Pericentric bridge University, for reviewing the English of the manu- inversion and X chromosome polymorphism in script; Dr. João Alves de Oliveira and Dr. Luiz Flamarion Rhipidomys sp. (Cricetidae, Rodentia) from Brazil. B. Oliveira and Stella Franco (Museu Nacional) helped Caryologia 46(2-3):219-225. with specimens in the collection. A collecting permit THIRIOT-QUIÉVREUX C and A INSUA. 1992. Nucle- was provided by the Instituto Brasileiro do Meio olar organizer region variation in chromosomes of Ambiente e dos Recursos Naturais Renováveis (IBAMA). THE KARYOTYPE OF Dasyprocta azarae 233
three oyster species. Journal of Experimental Ma- YONENAGA-YASSUDA Y, MJ SOUZA, S rine Biology and Ecology 157:33-40. KASAHARA, M L’ABBATE, and HT CHU. 1985. WOODS CA. 1993. Suborder Hystricognathi. Pp:771- Supernumerary system in Proechimys iheringi 806, in: Mammal species of the World: A taxo- iheringi (Rodentia, Echimyidae) from the State of nomic and geographic reference (DE Wilson and São Paulo, Brazil. Caryologia 38:179-194. DM Reeder, eds.). Smithsonian Institution Press, YONENAGA-YASSUDA Y, MFL ASSIS, and S Washington. KASAHARA. 1992. Variability of the nucleolus or- XIMENES GEI. 1999. Sistemática da família ganizer regions and the presence of the rDNA genes Dasyproctidae Bonaparte, 1838 (Rodentia, in the supernumerary chromosome of Akodon aff. Hystricognathi) no Brasil. Msc Thesis, Universidade arvicoloides (Cricetidae, Rodentia). Caryologia de São Paulo, SP, Brasil. 45(2):163-174.