ESTUDOS COMPARATIVOS ENTRE POPULAÇÕES DE Loricariichthys rostratus (SILURIFORMES, LORICARIIDAE, LORICARIINAE) COLETADAS À MONTANTE E À JUSANTE DAS CATARATAS DO IGUAÇU: ASPECTOS CITOGENÉTICOS, GENÉTICO-MOLECULARES E REPRODUTIVOS.

Abstract

Loricariichthys rostratus Reis & Pereira, 2000 is a catfish species taxonomically described from Middle-Lower Parana River Basin, although recently individuals were captured both upstream (Lower Iguassu River) and downstream (Middle-Lower Parana River) from Iguassu Falls. Herein, conventional and molecular cytogenetics techniques were used to characterize and to compare both populations of L. rostratus, besides electron microscopy analysis in order to verify adhesive structures on the eggs. Cytogenetics data showed the same results for both populations, with diploid number equal to 54 chromosomes (10m + 16sm + 2st + 26a, FN=82). Heterochromatins were observed in centromeric region of most chromosomes. The nuclear organizing regions (AgNORs and 18S rDNA-FISH) were detected in interstitial-proximal region on the long arm of the acrocentric chromosome pair 19. The 5S rDNA cistrons were detected in interstitial-distal region on long arm of the acrocentric chromosome pair 15. The presence of adhesive structures on the eggs that are responsible to attach them to surfaces and themselves, which facilitate parental car, was verified through scanning electron microscopy. Basic and molecular cytogenetics analysis showed no chromosomal difference between populations, even being isolated by the Iguassu Falls. It indicates that probably Iguassu Falls did not separate completely the Parana River Basin from the Iguassu River Basin and, in flood periods, allows animals to acquire and colonize upstream of Iguassu Falls.