ABSTRACT
Hypsiboas punctatus (Schneider 1799) posee una amplia distribución en Sudamérica, a lo largo de un gradiente ambiental y latitudinal (tropical/templado), por lo que las condiciones que enfrentan sus poblaciones difieren significativamente. Hasta el momento, solamente se conocen los parámetros reproductivos de esta especie en regiones tropicales, por lo que en el presente trabajo se estudió una población de una región templada para evaluar si existen diferencias. Los individuos estudiados resultaron ser de menor tamaño que los de poblaciones tropicales. El tamaño y peso de los machos no se correlacionaron con el volumen testicular. En cambio, el tamaño y el peso de las hembras se correlacionaron positivamente con su fertilidad. No se encontraron cuerpos grasos desarrollados en las hembras pero sí en los machos. Los resultados obtenidos sugieren que existe una variabilidad en los parámetros reproductivos de H. punctatus que puede estar relacionada tanto a un fenómeno de plasticidad fenotípica como de diferenciación genética entre poblaciones distantes. Esto sería una de las claves que permitiría a esta especie prosperar en diferentes ecosistemas con distintas características y presiones ambientales.
Hypsiboas punctatus (Schneider 1799) has a wide distribution in South America, throughout a latitudinal and environmental gradient (tropical/temperate), thus, supporting significantly different pressures among populations. Until now, only tropical populations reproductive parameters have been recorded. Then, our goal was to study reproductive parameters on a population inhabiting a temperate climate region to evaluate differences with those inhabiting tropical regions. Studied frogs were smaller than those from tropical regions. There was no correlation between weight and size of males and their testicles volume. Conversely, females weight and size was positively correlated to their fertility. Fat bodies were developed in males but absent in females. When compared with other studies, our results showed the variability in reproductive parameters of H. punctatus between tropical and temperate regions. This variability could be the result of phenotypic plasticity and/or genetic differentiation between distant populations. This variability may be one of the keys that allow H. punctatus to thrive in diverse ecosystems with different characteristics and environmental pressures.
ABSTRACT
In environments with thermal and pluvial seasonality such as those of the Middle Paraná River floodplain (Province of Santa Fe, Argentina), most amphibian species reproduce during the warm season and drastically diminish their activity during winter. Even though, a few species remain active during the cold season, such as Hypsiboas pulchellus that has its reproductive peak during the autumn-winter period (and the consequent energy demand). The objective of this study was to analyze and compare the feeding and development of fat bodies during the low temperature season for H. pulchellus and Dendropsophus nanus. We analyzed entire gastrointestinal tract contents of both species (H. pulchellus=110 specimens; D. nanus=114 specimens) and applied an index (IRI%) that combines prey abundance, volume and frequency to describe frogs diets; we used fat bodies weights as indicators of stored energy reserves. We compared diet between species with a niche overlap index (Ojk: 0-1) and used null models to ascribe statistical significance to evaluate overlap; and we analyzed variation in empty guts proportions through months and between species. Also, using ANCOVAs we explored differences in fat bodies, number and volume of prey consumed along months, between species and sexes. The most important preys in H. pulchellus diet during the cold season were Araneae (IRI%=34.96), Chironomidae (IRI%=33.08), Tipulidae (IRI%=11.44) and Gryllidae (IRI%=7.31); while for D. nanus, Chironomidae (IRI%=48.14), Tipulidae (IRI%=18.41), Psychodidae (IRI%=7.44) and Araneae (IRI%=7.34). Diet overlap between species was elevated (Ojk=0.78) and higher than expected by chance (mean simulated indices: Ojk=0.04; p[observed≥expected]<0.01; p[observed≤expected]=1). In H. pulchellus there was a monthly variation in number of prey per gut, while in D. nanus there was a difference in fat bodies development between sexes. Fat bodies development, number of prey per gut and preys volume also varied between species. Despite diet similarity between H. pulchellus and D. nanus, each species showed a different strategy to accumulate energy and support their activity during the cold season. The low rate of gastrointestinal emptiness in H. pulchellus (<10% in any analyzed month) together with the poor development of their fat bodies, allows us to point out that, to sustain the breeding elevated energy demands, this species continues with a high feeding rate even at the low temperatures of cold season. On the other hand, the rate of gastrointestinal emptiness of D. nanus was higher than that of H. pulchellus (May=17.24%, July=22.22% and August=35.71%), while their fat bodies were well developed. Thus, D. nanus would depend more on their stored reserves to sustain the energy demands of being active during the low temperatures season and hence would reach the reproductive season in spring-summer in good body condition.
Existe escasa información sobre la alimentación de las especies de anfibios activas durante la estación fría o las estrategias de utilización de reservas lipídicas como fuente de energía durante el periodo de bajas temperaturas. Por lo tanto, se analizaron las estrategias de obtención y acumulación energética durante la estación de bajas temperaturas en un anfibio que se reproduce principalmente en otoño-invierno, Hypsiboas pulchellus (Hp), y uno que lo hace en primavera-verano, Dendropsophus nanus (Dn). Para ello se analizó la alimentación de ambas especies y se utilizó el peso de los cuerpos grasos (CG) como indicador del desarrollo de las reservas energéticas. Si bien se encontró una elevada similitud en la dieta entre las especies, esto no implicó la ausencia de diferencias en las estrategias de obtención energética entre ellas. El bajo índice de vacuidad gastrointestinal de Hp, acompañado de CG poco desarrollados, permite señalar que, para sostener la elevada demanda energética de la actividad reproductiva concentrada en el otoño-invierno, esta especie continúa alimentándose aún en temperaturas bajas. Por otro lado, el índice de vacuidad de Dn fue mayor al de Hp, mientras que sus CG se encontraron bien desarrollados, por lo que esta especie utilizaría en mayor medida sus reservas lipídicas como fuente de energía para transitar el período de bajas temperaturas y llegar en buenas condiciones a la temporada reproductiva en la próxima primavera-verano.
Subject(s)
Animals , Female , Male , Anura/physiology , Energy Metabolism/physiology , Feeding Behavior/physiology , Argentina , Anura/classification , Feeding Behavior/classification , SeasonsABSTRACT
The study of the feeding ecology of amphibians is an old issue in herpetology. Notwithstanding, the lack of food resources data in many studies of amphibians feeding has lead to partial understanding of frog feeding strategies. In this study we evaluate the trophic selectivity of a red spotted green frog (Hypsiboas punctatus) population from a Middle Paraná River floodplain pond in Argentina, and discuss the importance of prey availability data when interpreting results from diet analysis. We analyzed the gut contents of 47 H. punctatus adults and compared frogs diet with the environmental food resources. Prey availability was estimated by systematically seep-netting the microhabitat where anurans were localized foraging. We identified 33 taxonomic categories from gastrointestinal contents. Numerically, the most important prey categories were dipterans, followed by hemipterans, homopterans and coleopterans. The diet similarity between males and females was high and no statistical differences in diet composition were found. The most abundant food resources in the environment were dipterans, coleopterans, homopterans and collembolans. In order to assess whether frogs were selecting their preys, we calculated Piankas niche overlap index and Jacobs electivity index comparing gut contents to prey availability data. Trophic niche overlap was medium but significantly higher than expected by chance. The electivity index indicated that H. punctatus foraged dipterans slightly above their environmental abundance. Among the secondary preys, hemipterans were foraged selectively, homopterans were consumed in the same proportion to their occurrence in the environment, coleopterans were foraged quite under their availability and collembolans were practically ignored by frogs. Without food resources data, H. punctatus could be classified as a specialist feeder, but dipterans also were quite abundant in the environment. Our results show that H. punctatus fit better as a generalist feeder, foraging on their main food item and some secondary preys in similar proportion to their environmental availability; even though other secondary preys are being selectively preferred or ignored by frogs. Our data illustrate the importance of including the resource availability data on diet studies to improve the understanding of amphibian feeding ecology. Rev. Biol. Trop. 57 (3): 847-857. Epub 2009 September 30.
La falta de datos sobre la disponibilidad de recursos alimenticios en muchos trabajos sobre ecología trófica de anfibios ha llevado a una comprensión parcial de las estrategias alimentarias de este grupo. Este estudio evalúa la selectividad trófica de una población de Hypsiboas punctatus en una laguna del valle aluvial del río Paraná Medio en Argentina, y discute la importancia de los datos de disponibilidad de presas para interpretar las estrategias de alimentación de las ranas. Se analizaron los contenidos gastrointestinales de 47 adultos, y se compararon con la disponibilidad ambiental de presas, estimada mediante muestreo sistemático del micro-hábitat de forrajeo de los anuros. Se identificaron 33 categorías de presas. Las más importantes fueron dípteros, hemípteros, homópteros y coleópteros. Se encontró una elevada similitud entre la dieta de machos y hembras, y no se hallaron diferencias significativas en su composición. Los recursos alimenticios más abundantes fueron los dípteros, coleópteros, homópteros y colémbolos. La superposición de nicho trófico fue media (índice de Pianka) pero significativamente más elevada que la esperada por azar. H. punctatus consumió dípteros en una proporción levemente superior a su disponibilidad ambiental (índice de selectividad de Jacobs). La estrategia de depredación de H. punctatus se ajusta mejor a una táctica generalista, ya que su principal ítem presa y algunos ítems secundarios fueron capturados en proporciones similares a su disponibilidad ambiental, y solo una porción reducida de su espectro de recursos tróficos fue consumida selectivamente. Estos resultados evidencian la importancia de incluir los datos de disponibilidad de recursos en los estudios de alimentación para lograr un mejor entendimiento de la ecología trófica de los anfibios.
Subject(s)
Animals , Female , Male , Anura/physiology , Feeding Behavior/physiology , Predatory Behavior/physiology , Argentina , Gastrointestinal ContentsABSTRACT
We performed a comparative analysis of the nucleolus organizer region (NOR) distribution in the karyotypes of hylid frogs from two different taxonomic groups, Hypsiboas faber and H. semilineatus. Silver nitrate staining of NORs (Ag-NORs) and fluorescence in situ hybridization (FISH) with a rDNA probe were used to investigate the chromosomal location of rDNA loci in two species. The karyotype of H. semilineatus and the Ag-NORs distribution of the four species are presented herein for the first time. After conventional staining, the four species presented very similar karyotypes with 2n = 24, but Ag-NORs analyses revealed species-specific characteristics. H. albomarginatus, H. faber and H. semilineatus had one pair of interstitial Ag-NORs in the short arm of pairs 2, 11, and in the long arm of pair 7, respectively. H. pardalis presented telomeric NORs in the long arm of pair 11. Ag-NORs were heteromorphic in three of the species (H.pardalis, H. semilineatus and H. albomarginatus) and FISH confirmed the differential activity of rDNA genes in H. semilineatus. In the present study, 2n = 24 karyotypes could be distinguished by their Ag-NORs distribution. Our results further the knowledge about the cytogenetics of hylids from Brazil.
Subject(s)
Animals , Anura/genetics , DNA, Ribosomal , Nucleolus Organizer Region , Anura/classification , Brazil , In Situ Hybridization, Fluorescence , KaryotypingABSTRACT
The larval morphology of Hypsiboas leptolineatus was studied. The tadpole has an ovoid body in lateral view, wider than deep; snout rounded with dorsal reniform nostrils; spiracle sinistral with lateral wall attached to body; anal tube dextral; tail fins convex with acuminate tip; oral disc ventral; labial tooth row formula is 2(2)/3(1); moderately developed beaks with serrated jaw sheaths. These external oral features are compared with those of the known tadpoles in the Hypsiboas polytaenius clade. The oral cavity was studied using an electron microscope. Life history aspects are commented.
A morfologia larval de Hypsiboas leptolineatus foi estudada. O girino possui corpo ovóide em vista lateral, mais largo que alto; focinho redondo com narinas dorsais; espiráculo esquerdo, com parede lateral junto ao corpo; tubo anal destro; nadadeiras convexas, com ponta acuminada; disco oral ventral; fórmula dentária 2(2)/3(1); bico córneo moderadamente desenvolvido serrilhado. Estas características externas são comparadas com as dos outros girinos conhecidos do clado Hypsiboas polytaenius. A cavidade oral foi estudada usando microscopia eletrônica. Aspectos de história natural são comentados.