PL-ISSN 0015-5497(print),ISSN1734-9168(online) Foliabiologica (Kraków), vol. 58 (2010), No 1-2 @ Institute of Systematics and Evolution of Animals, PAS, Kraków,2009 doi:10.3409/fb58_1-2.29-34 CytogeneticCharacterizationof Geophagusbrasiliensis andTwoSpeciesof Gymnogeophagus (Cichlidae:Geophaginae)fromGuaíbaLake,RS,Brazil LarissaBETTIN PIRES,LuciaGIULIANO-CAETANO,andAnaLúciaDIAS AcceptedSeptember15,2009 BETTIN PIRES L., GIULIANO-CAETANO L., DIAS A. L. 2010. Cytogenetic characterization of Geophagus brasiliensis and two species of Gymnogeophagus (Cichlidae: Geophaginae) from Guaíba Lake, RS, Brazil. Folia biol. (Kraków) 58: 29-34. The karyotypes of three species of fish of the Cichlidae family from the Forqueta river and several locations in Guaíba lake/RS (Brazil) were analyzed. All species presented 2n=48, while Gymnogeophagus gymnogenys showed two karyotypic formulae: 4m+44st-a with FN=52 and 6m+42st-a with FN=54. Gymnogeophagus labiatus presented 4m+4sm+40st-a andFN=56and Geophagus brasiliensis 4sm+44st-a and FN=52. Simple NORs were found in all species with the exception of a population of G. gymnogenys from Saco da Alemoa/Barra do Ribeiro. CMA3 staining revealed NOR sites, while DAPI staining was negative and heterochromatin was limited to pericentromeric regions andassociatedtoNORs,exceptin G. labiatus. The data show a conserved pattern in Geophagus brasiliensis and karyotype variation in the species of Gymnogeophagus. Key words: Chromosome banding, diploid number conservation, karyotype, Perciformes. Larissa BETTIN PIRES, Lucia GIULIANO-CAETANO, Ana Lúcia DIAS, Universidade Estadual de Londrina, CCB – Departamento de Biologia Geral, 86051-990, Londrina, PR, Brasil. E-mail: [email protected] Among the Perciformes, the Cichlidae is one of family concern only the description of the diploid the largest families of vertebrates with 1300 de- number, karyotype formula and the location of scribed species and up to an estimated 1870 species. NORs. Only the fish families Gobiidae and Cyprinidae, In this study we cytogenetically analyse three with 1875 and 2010 species, respectively, compete species from two geophaginae genera, Gymnogeo- for the position of the largest family (KULLANDER phagus and Geophagus, from Guaíba lake and 1998). Forqueta river, RS, Brazil, through different chro- The distribution of species of cichlid fishes is mosome banding techniques. wide and includes Africa, South America, Central AmericaandpartsofAsiaandNorthAmerica,ina diversity of habitats (MOYLE &JUNIOR CECH 2000). Material and Methods The South American cichlids comprise about 50 Were analysed three species of the subfamily genera and 450 species and were organized by Geophaginae: 15 specimens (8 males, 5 females KULLANDER (1998) into eight subfamilies: Et- and 2 individuals of undetermined sex) of Gymno- roplinae, Pseudocrenilabrinae, Retroculinae, Cichli- geophagus gymnogenys (HENSEL 1870), 13 speci- nae, Heterochromidinae, Astronotinae, Geophagi- mens (5 males, 5 females and 3 individuals of nae and Cichlasomatinae. undetermined sex) of G. labiatus (HENSEL 1870) ThesubfamilyGeophaginaeisrepresentedby18 and10individuals(5malesand5females)of Geo- genera, but little is known of the cytogenetics of phagus brasiliensis,collectedintheForquetariver this group. Information is available for only seven and three different localities in Guaíba lake, RS: genera: Acarichthys, Apistogramma, Dicrossus, Barra do Ribeiro, Gasômetro and Saco da Alemoa Geophagus, Guianacara, Gymnogeophagus and (TableI).Voucherspecimensarecataloguedinthe Satanoperca, in which Geophagus brasiliensis fish collection of Museu de Zoologia da Universi- (QUOY &GAIMARD 1824) is cytogenetically the dadeEstadualdeLondrinaundercatalognumbers: best known. Most of the data obtained for this sub- MZUEL 4050 – Gymnogeophagus gymnogenys; 30 L.BETTIN PIRES etal. Table 1 Summary of the results for Gymnogeophagus and Geophagus in this work (2n = diploid number,FN=fundamentalnumber,SC=secondaryconstriction,NORs=nucleolarorgan- izer regions, HC = heterochromatin and CMA3 = chromomycin A3) Karyotype CMA3 Species Locality 2n formula FN SC NORs HC Multiple: Pair 3 (i)* Saco da Alemoa and 48 4 m + 44 st-a 52 Pair 3 (i)* Pair 3 (i)* C Barra do Ribeiro (RS) Pair 9 (t) Gymnogeophagus Pair 9 (t) gymnogenys Simple: Gasômetro (RS) 48 6 m + 42 st-a 54 Pair 20 (t)* C Pair 20 (t)* Pair 20 (t)* Simple: Gymnogeophagus Saco da Alemoa and 48 4 m + 4 sm + 40 st-a 56 Pair 1 (i) C Pair 1 (i) labiatus Forqueta river (RS) Pair 1 (i) Simple: Geophagus Saco da Alemoa and 48 4 sm + 44 st-a 52 Pair 6 (t)* C Pair 6 (t)* brasiliensis Gasômetro (RS) Pair 6 (t)* Legend:t=terminal;i=intersticial;C=pericentromeric;*=heteromorphism MZUEL 4901 – Gymnogeophagus labiatus and A secondary constriction in G. gymnogenys is MZUEL 4842 – Geophagus brasiliensis. locatedinaninterstitialpositiononthelongarmof pair 3 (st-a) for the population from Saco da Mitotic chromosomes were obtained from kid- Alemoa/Barra do Ribeiro, and in the terminal re- ney according to the conventional technique of gion on the short arm of pair 20 (st-a) for Gasôme- BERTOLLO et al. (1978). Chromosome morphol- tro, showing size heteromorphism among the ogy was determined on the basis of arm ratio in homologues (Fig. 1a & 1b, respectively). In metacentric (m), submetacentric (sm) and subtelo- G. labiatus the secondary constriction is located centric-acrocentric (st-a) chromosomes, accord- interstitially on the short arm of the largest pair of ing to LEVAN et al. (1964), with modifications. the complement (Fig. 2a) and in Geophagus bra- Chromosomes classified as metacentric and sub- siliensis in the terminal position of pair 6 (st-a), metacentric were considered as biarmed, and visible in some analyzed samples, showing hetero- subtelocentric-acrocentric as uniarmed, to deter- morphism between homologous chromosomes mine the fundamental number (FN). Nucleolar or- (Fig. 3a). ganizer regions (NORs) were identified by silver nitrate staining according to HOWELL and BLACK Silver nitrate staining of the chromosomes (1980). Heterochromatin was located by the C- showed simple NORs in Gymnogeophagus labia- banding technique using barium hydroxide ac- tus, G. gymnogenys (Gasômetro population) and cording to SUMNER (1972). Fluorochrome stain- Geophagus brasiliensis. One pair of metacentric ing with the GC- specific chromomycin-A3 (CMA3) chromosomes with interstitial AgNORs on their and AT-specific diamidino-2-phenylindole (DAPI) short arms was observed in the first species (Fig. 2b), was carried out according to SCHWEIZER (1980). and terminal AgNORs on the short arms of one subtelo-acrocentric pair, with size heteromor- phism, were observed in the last two species, all coincident with secondary constrictions (Fig. 1d & Results 3b, respectively). In the samples of G. gymnogenys from Saco da The results for the three species revealed a diploid Alemoa/Barra do Ribeiro, silver nitrate staining number (2n) equal to 48 chromosomes; however, revealed multiple NORs, with 2 to 4 nucleolar differences in karyotype formula were observed. chromosomes and markings in the terminal region Gymnogeophagus gymnogenys presented 4m + of the short arm in a pair of subtelo-acrocentric 44st-a and a fundamental number (FN) equal to 52 chromosomes (pair 9) and in the interstitial region for the population of Barra do Ribeiro and Saco da of the long arm of pair 3 (st-a). The latter pair was Alemoa(Fig.1a),and6m+42st-aandFN=54for coincident to secondary constriction which the population of Gasômetro (Fig. 1b); Gymno- showed size heteromorphism between the homo- geophagus labiatus presented 4m + 4sm + 40st-a logues of the region (Fig. 1c, Table I). andFN=56(Fig.2a)and Geophagus brasiliensis Staining with the fluorochrome chromomycin 4sm + 44st-a and FN = 52 (Fig. 3a) (Table 1). A3 revealed fluorescent sites corresponding to the Cytogeneticsof Geophagus andGymnogeophagus 31 Fig. 1. Karyotypes of Gymnogeophagus gymnogenys, of the Saco da Alemoa/Barra do Ribeiro (a) and Gasômetro (b), with AgNORs(candd,respectively)andCMA3 pairs(eandf,respectively). Bar=10 Fm. Fig.2. KaryotypeandAgNORs/CMA3 pairsof Gymnogeophaguslabiatus (a,bandc,respectively). Bar=10 Fm. Fig.3. KaryotypeandAgNORs/CMA3 pairsof Geophagusbrasiliensis (a,bandc,respectively). Bar=10 Fm. 32 L.BETTIN PIRES etal. Fig. 4. Somatic metaphases with C banding: G. gymnogenys from Saco da Alemoa/Barra do Ribeiro (a) and Gasômetro (b), G. labiatus (c) and Geophagus brasiliensis (d). The arrows indicate the chromosome with the secondary constrictions. Bar=10 Fm. AgNORs in all species. A fluorescent signal was tion in Neotropical cichlids, since it is found in not observed for DAPI, whereas the secondary most species, and is composed usually of the st-a constriction was less evident in some species (Fig. 1e chromosome type, resulting in a small fundamen- and f, Fig. 2c, Fig. 3c). tal number. C banding revealed heterochromatin distributed Although the diploid number is conservative in mainly in the pericentromeric regions of several the different species of Gymnogeophagus and chromosomes and heterochromatin blocks associ- Geophagus brasiliensis studied so far, changes in atedwithNORs,exceptin G. labiatus (Fig.4).The karyotype formula were found between species same size heteromorphism observed for Giemsa and within the same species (FELDBERG et al. and silver staining in G. gymnogenys and G. bra- 2003), as observed here in G. gymnogenys and siliensis was also found for C banding. G. labiatus. PEIXOTO &ERDTMANN (personal communica- tion) have studied the same