Oriental Chaco, part of the Great American Chaco, embraces a plain area with soft slopes towards the west-east region.

<p>Los anuros poseen una gran plasticidad fenotípica y constituyen un grupo de referencia para estudios de desarrollo ontogenético, así como aspectos morfo-fisiológicos, ecológicos, filogenéticos y evolutivos. Existe abundante información sobre la morfología larval de numerosas especies de anuros, sin embargo, el desarrollo embrionario y larval ha sido escasamente explorado en Leptodactylidae. En el presente trabajo se describen y caracterizan los principales cambios en la morfología externa de varios órganos así como también del sistema digestivo durante los estadios embrionarios, larvales y metamórficos de <em>Physalaemus albonotatus. </em>Para ello se coleccionaron embriones y larvas en ambientes naturales, los cuales fueron criados en condiciones de laboratorio y fijados periódicamente en formol 10%. Las observaciones se realizaron bajo lupa estereoscópica y microscopio electrónico de barrido. El desarrollo embrionario y larval siguió el patrón característico de los anuros con fase larval acuática obligada. La organización de los principales órganos ocurrió durante los estadios embrionarios y primeros larvales, abarcando el periodo comprendido entre los estadios 17 y 25. Algunos órganos transitorios como las branquias externas y las papilas adhesivas desaparecen tempranamente durante el desarrollo, mientras que otras estructuras como la cámara opercular, el espiráculo, el disco oral, el tubo proctodeal, la cola y las aletas caudales se conservan hasta el final del periodo larval, y se pierden recién durante la metamorfosis. En esta última etapa se evidencian cambios bruscos en la anatomía de la mayoría de los sistemas de órganos y se configura el diseño corporal propio del individuo juvenil. Las caracterizaciones morfológicas de estructuras embrionarias y larvales de <em>P. albonotatus </em>contribuirán con información de referencia aplicable a otros miembros de la familia Leptodactylidae.</p>

Vitreorana uranoscopa inhabits small or medium-sized streams with rocky bottoms of the Interior Atlantic Forest of eastern Brazil, northeastern Argentina, and likely southeastern Paraguay. Most of the available information originates from Brazilian populations. Only a few populations from Argentina have been reported and information about their natural history is almost unknown. This work re-describes the advertisement call of V. uranoscopa from a new population discovered in the province of Misiones, Argentina, and includes further data about its reproduction, population density and habitat conservation status. On the basis of 11 recorded males, two call types were recorded. Results showed that the typical advertisement call is formed by pulsed notes released singly, in groups, or in combinations of both at an average rate of 13.86 notes/min. Notes lasted 0.013-0.085 s and had 1-5 well-defined pulses lasting 0.003-0.015 s; the pulse repetition rate was 90.9-166.66 pulses/s. The peak of dominant frequency was 4312.5-4875.0 Hz with a slight, ascending frequency modulation. These data agree with those reported in previous studies, although some differences in the note duration, intercall interval, number of pulses and harmonics were identified. These differences might be due to either the technological limitations at the time of those studies or interpopulation variation. The second call type (reported for the first time in V. uranoscopa) is formed by 1-2 additional pulses at the beginning of some notes and has lower amplitude than typical calls, but the social context of its emission is still unknown. The calling males perched on the leaves of the marginal vegetation, either alone or occasionally in groups of 2-3 individuals, with a average of 5.5 individuals per 100 m transect. Clutches containing up to 36 eggs or embryos were found on the upper surface of fern fronds. In Argentina, V. uranoscopa occurs only in Araucaria forests of the Interior Atlantic Forest. Thus, the protection of streams with abundant marginal vegetation seems to be essential for the conservation of this species.

Previously described calls of Trachycephalus typhonius (Linnaeus, 1758) correspond to several populations from Central and South America, but in general, these descriptions were brief and often based on a single recorded individual. Here, based on an expressive sample, we re-describe the advertisement calls of T. typhonius using recordings from populations in Brazil and Argentina. Additionally, we discuss geographical variation of calls, comment on their frequency band structure and compare calls with those described for other species of Trachycephalus. Calls of 32 males were recorded and temporal and spectral features of 269 calls were measured. To search for discrimination among three populations sampled we used the Random Forest (RF) model, Multidimensional Scaling Analysis (MDS) and Wilcoxon-Mann-Whitney Rank Sum Test. The advertisement calls of T. typhonius consist of a multipulsed note of 343–540 ms of duration, emitted at regular intervals, with up to three emphasized frequency bands. Dominant frequency ranged between 1705–2750 Hz. Calls from Rondônia (Brazil) were significantly different from those recorded in Argentina and Minas Gerais (Brazil) in relation to pulse rate and dominant frequency. Populations from Minas Gerais and Argentina differed in dominant frequency of calls. Such population differences can be partly attributed to differences in prevalence of calling sites (immersed in water vs. perches on vegetation), but can also hint at the existence of cryptic species diversity under this taxon.

In this work we analyzed the karyotype of five populations of Adenomera diptyx from Argentina after conventional staining, Ag-NOR and C-banding. All specimens presented 2n = 26 and FN = 34. The karyotype was formed by three submetacentric, one metacentric and nine telocentric pairs. Silver staining revealed that the NOR was located on a secondary constriction in pair 7. C- banding evidenced constitutive heterochromatin at the pericentromeric region of all chromosomes. The karyotype of A. diptyx was similar to that of A. hylaedactyla (2n = 26, FN = 34) and different from that of A. andreae (2n = 26, FN = 40) in the fundamental number and secondary constriction position. It also differed from the karyotypes of A. marmorata (2n = 24, FN = 34 and 36) and of A. aff. bokermanni (2n = 23, FN = 34) in diploid number. Until a comprehensive cytogenetic analysis of all the species of the genus is performed, their chromosome evolution will remain poorly understood.