Observations were made on the reproductive biology of Physalaemus cuvieri from open area habitat in São Luis, MA, Brazil, from August 1988 to August 1989. The reproductive tactics are compared to those of the same species in southeastern Brazil. Vocalization and reproductive activity were restricted the rainy season (January to June), with peaks of activity during late March and early April. Nocturnal calling activity turn was prolonged, with little variation in the number of individual calling during the night. The presence of communal foam nests suggests non-territorial behaviour in this species. However, males called from the same sites all night long. They showed differentiated vocalizations or antiphony, and aggressive physical interactions, which suggests that there may be some territorial behaviours in males. The remainder of the territorial behaviour is related to persistence of the invading male. Satellite behaviour, females mate choice, and a stereotyped behaviour (e.g. quick circular movement of both male and female) prior to amplexus, were also associated with territoriality.
Detailed characterizations of the karyotypes of the Brazilian leptodactylid frogs Pleurodema diplolistris, the only species of Pleurodema not studied cytogenetically so far, and Physalaemus nattereri, a species in the Ph. biligonigerus group, are presented. Both karyotypes had 2n = 22 and their chromosomes had a very similar morphology, except for pair 11, which was metacentric in Pl. diplolistris and telocentric in Ph. nattereri. The localization of nucleolar organizer regions (NORs) and heterochromatic bands allowed the differentiation of chromosomes that were morphologically indistinguishable between these species, such as pairs 1, 3 and 10, which showed interstitial C-bands in Ph. nattereri, and pair 8, that had an NOR and an adjacent C-band in Pl. diplolistris. Pair 8 also has NOR-bearing chromosomes in many other Pleurodema species. However, in these species, the NOR is located proximal to the centromere on the short arm, while in Pl. diplolistris it occurred distally on the long arm, a condition that may be considered a derived state. In Ph. nattereri, the NOR occurred on chromosome 11 and differed from the other species of the Ph. biligonigerus group. In contrast, C-banding revealed a heterochromatic block near the centromere on the short arm of pair 3, a characteristic common to all members of this group of Physalaemus.