Eduardo F. Schaefer

Growth-Mark Formation and Chronology of Two Neotropical Anuran Species

Abstract In amphibians from tropical or subtropical regions well-expressed growth marks in bone could be expected because of the existence of strong dry/wet seasons, but little evidence is available. Additionally, temporal patterns of growth-mark formation may be a function of genetic and environmental factors. We used skeletochronology and a laboratory experiment to tease apart both causal sources, establishing direct correspondence between an observed pattern of bone growth and the actual age of Ceratophrys cranwelli and Dermatonotus muelleri from the subtropical Argentinean Chaco. Also, we describe the growth by application of the von Bertalanffy model. Growth rates decreased in both species, tending to reach asymptotic values at age 8–10 months after metamorphosis. Both species clearly exhibited haematoxylinophilic lines of arrested growth (LAG) after one year growing in captivity. These results reinforce the hypothesis that in subtropical climates the LAG formation is ultimately caused by a general intrinsic (genetic) control.

The Tadpole of Physalaemus albonotatus (Anura: Leptodactylidae)

Abstract We describe the tadpole of Physalaemus albonotatus (Anura, Leptodactylidae), from specimens collected from northeastern Argentina. The distinguishing characteristics (Stage 36) are (1) labial tooth row formula: 2(2)/3(1); (2) rostral gap about 2.5 times greater than mental gap; (3) body length of 10.00 mm and total length of 24.20 mm; and (4) body dark brown to dark green dorsally with scattered dark spots. Morphological features were compared with other tadpoles belonging to the Physalaemus cuvieri species group from Argentina.

Reproductive biology of Argenteohyla siemersi pederseni Williams and Bosso, 1994 (Anura: Hylidae) in northeastern Argentina

The present study describes the reproductive biology of Argenteohyla siemersi pederseni in a modified “quebracho” forest of Schinopsis balansae in northeastern Argentina. Observations were made between January 2007 and March 2009 at El Perichón, Corrientes Province, Argentina. Argenteohyla s. pederseni bred once per year over a 3-day period in a semi-permanent pond during the first spring rains in mid-September. Males called while floating on the water surface. The advertisement call was short and repeated at regular intervals in relatively fast succession, forming groups of multiple calls. Aggressive calls were evoked in two different agonistic interactions. Eggs were black, laid in three-dimensional arrangements interspersed within the submerged vegetation. Egg number per clutch ranged from 2638 to 8987. Tadpole redescription shows many differences and similarities with previous descriptions. The reproductive biology of A. s. pederseni has several similarities with another pond-dwelling casque-headed frog species.

Acoustic Repertoire of Melanophryniscus cupreuscapularis (Céspedez and Álvarez 2000) (Anura: Bufonidae): Advertisement, Encounter, and Release Calls

Abstract We describe the vocal repertoire of Melanophryniscus cupreuscapularis, a bufonid toad of the Melanophryniscus stelzneri species group, which has been recently listed as “Vulnerable” by the Asociación Herpetológica Argentina. Recordings were obtained in “Paraje El Perichón,” a relict of Schinopsis balansae “quebracho” forest near Corrientes City, Argentina, in September 2007. We provide data on the structure and frequency of three kinds of vocalization: the advertisement, the encounter, and the release calls. We found that the advertisement call is formed by two distinct sections: a first segment consisting of short emissions, usually grouped, and a fast trill. We found that the encounter call is also composed of two segments but that the number of simple emissions in the first segment is greater and more variable (6–60) than in the advertisement call, and the emissions are ungrouped. Although the dominant frequency was similar to the advertisement call, the encounter call frequency was 2,184 Hz (range: 1,832–2,482). The release call is composed of isolated emissions emitted at a lower frequency (1,798 Hz, range: 1,712–1,926) than are the other calls. The structure of the advertisement call was similar to that of other species of the stelzneri group. Resumen Se describe el repertorio vocal de Melanophryniscus cupreuscapularis, un bufónido que pertenece al grupo stelzneri recientemente categorizada como “vulnerable” por especialistas de la Asociación Herpetológica Argentina (AHA). Las grabaciones fueron obtenidas en septiembre de 2007 en el Paraje “El Perichón,” un relicto de bosque de quebracho colorado, Schinopsis balansae, cercano a la ciudad de Corrientes, Argentina. Proveemos información sobre el análisis estructural y de frecuencia de tres tipos de vocalizaciones: canto de advertencia, de encuentro y de rechazo. M. cupreuscapularis emite un canto de advertencia formado por dos secciones diferentes: un primer segmento compuesto de emisiones aisladas, generalmente agrupadas, seguidas por un rápido vibrato. El canto de encuentro está compuesto también por dos segmentos, pero en este caso el número de emisiones simples del primer segmento es mayor y más variable (6–60) que en el canto de advertencia y se presentan desagrupadas. Si bien la frecuencia dominante es similar a la del canto de advertencia, en el canto de encuentro estas ocurren aproximadamente a 2,184 Hz (1,832–2,482). Finalmente, el canto de rechazo es una vocalización conformada por emisiones aisladas emitidas a menor frecuencia (1,798 Hz, range: 1,712–1,926) que en los otros dos casos. Nosotros encontramos similitudes entre la estructura del canto de esta especie con la de otros miembros del grupo stelzneri.

TROPHIC AND MICROHABITAT NICHE OVERLAP IN TWO SYMPATRIC DENDROBATIDS FROM LA SELVA, COSTA RICA

A B S T R A C T. — We studied the trophic ecology of Dendrobates auratus and Oophaga pumilio in La Selva Biological Station, Costa Rica. At this site, both dendrobatids are sympatric due to the introduction and naturalization of D. auratus in the last 24 years. Diets of both dendrobatids were recorded by the analysed stomach flushing technique. Microhabitats uses were defined as the site where each individual was captured. The influence of microhabitat on diets was evaluated by the dietary (prey proportions and volume) and microhabitat overlaps using Pianka’s (Ojk) overlap index calculated with EcoSim software. Diets of both dendrobatids were principally characterized by the preference of hymenopterans (ants), acarines and collembolans, resulted in a high overlapping in prey proportions and prey volume. However, diets overlaps were not significant, suggesting the absence of negative feeding interactions. Microhabitat use was low overlapped and also not significant, suggesting a differentiation on the use of spatial resource. The absence of negative feeding interactions between Dendrobates auratus and Oophaga pumilio could be due to segregation in microhabitat use and possible by the abundance of trophic resource in the area. The great large volumes of formicids and acarines in the diet of this dendrobatids are in agreement with the hypothesis of these arthropods as a dietary source of alkaloids.

A new flesh fly species (Diptera: Sarcophagidae) parasitic on leptodactylid frogs

Here we describe a new species of sarcophagid fly reared from larvae found feeding on three species of leptodactylid frogs collected in subtropical Corrientes Province in northeastern Argentina. Our species description is based on adult male and female external morphology and genitalia. Adult males and females of the new species were associated with certainty because all specimens studied were reared from single clutches of larvae on each of three infested frogs. Thus, adult males and females reared from each clutch were siblings that emerged almost simultaneously. The paper provides line drawings, high-resolution photographs, and SEM images to aid in identifying Lepidodexia (Notochaeta) adelinasp. nov. and to distinguish the new species from its closely related congeners. We include brief notes on the host species and on larval feeding behavior of L. (N.) adelina. This is the first and only species in the genus Lepidodexia reported to parasitize leptodactylid frogs. Further, our observations reported here are the first to fully document a completed life cycle by sarcophagid fly larvae on three different species of leptodactylid frogs and the only well-documented case of myiasis of an amphibian in Argentina.