Banding patterns, multiple sex chromosome system and localization of telomeric (TTAGGG)(n) sequences by FISH on two species of Polychrus (Squamata, Polychrotidae)

Karyotypes of Polychrus acutirostris and P marmoratus after differential st aining are reported for the first time. P acutirostris presents 2n=20 (fema les) and 2n=19 (males). The differential diploid number is due to a multipl e sex chromosome determination X1X1X2X2:X1X2Y type with the presence of a t rivalent in male meiosis. A large subtelocentric chromosome is involved in the translocation with the Y chromosome. This chromosome exhibits a heteroc hromatic and conspicuous late replication region, which probably bears the Y chromosome, since it was only observed in males. P. marmoratus displays f emales 2n=30 and males 2n=29, presenting acrocentric chromosomes of decreas ing size and a large submetacentric Y chromosome in males due to a multiple sex chromosome mechanism X1X1X2X2:X1X2Y Ag-NORs are located in different c hromosomes: at the distal region of pair 2 in P. acutirostris and of pair 1 in P. marmoratus. Both species present small amount of constitutive hetero cromatin. Our findings and those already published for P. femoralis (2n=26) and P. peruvianus (males 2n=27 and females 2n=28) reveal that Polychrus ha s uncommon karyotypes when compared to other non-acrodont Iguania, and cons iderable variability at interspecific level. Interstitial telomeric sites ( ITSs) were detected in P. acutirostris using a (TTAGGG)(n) oligomer as a FI SH probe.