Rigoberto Solís

Frog call intensities and sound propagation in the South American temperate forest region

Abstract Sound pressure levels and the spectral structure of the advertisement calls of five species of frogs from the South American temperate austral forest were analyzed. Males of Eupsophus emiliopugini, Batrachyla antartandica and B. leptopus call from the ground in bogs, while males of Hylorina sylvatica and Pleurodema thaul call from the water surface in marshes. Calling males of the species from bogs and marshes spaced at average distances that were shorter and longer than 2 m, respectively. The properties of these habitats for sound propagation were evaluated by broadcasting pure tones, broadband noise and tape-recorded advertisement calls of the three species from bogs and of H. sylvatica. Excess attenuation and spectral degradation were higher for calls broadcast in bogs than in the marsh. The calls of B.␣antartandica and B. leptopus, with dominant frequencies of about 2 kHz, were more affected than those of E.␣emiliopugini and H. sylvatica, with dominant frequencies below 1.5 kHz. These results show the lack of an optimal relationship between properties of habitats for sound transmission and the spectral structure of these anuran calls. Body size imposes an important constraint on call spectra and propagation, which frogs counteract by distribution patterns and auditory capabilities.

Presence of Batrachochytrium dendrobatidis in feral populations of Xenopus laevis in Chile

Batrachochytrium dendrobatidis (Bd) is a causal agent of disease and population decline of amphibian populations, and the extinction of several anuran species worldwide. Diverse hypotheses have been provided for the emergence of this fungus in different continents, ranging from global climate change to the vectoring of Bd via the international trade in amphibian species. In order to address these hypotheses, it is important to assess the current distribution of Bd in the context of introduced non-native amphibian species. We sampled several populations of the African clawed frog Xenopus laevis across its distribution in Chile in order to detect the presence of B. dendrobatidis and evaluate the role of this frog as a potential vector. In three of ten sites sampled, individuals harbored B. dendrobatidis infection, with an overall prevalence of infection across the studied populations of 24% (14 positive out of 58 analyzed specimens). The rapid spread exhibited by this frog within Chile suggests that transpecific transmission of the pathogen is possible, perhaps jeopardizing native species. This finding indicates the urgent need to establish long-term monitoring population programs in order to allow early detection disease-driven changes in the sizes of native populations, allowing the prompt application of conservation practices.

Testosterone Levels and Evoked Vocal Responses in a Natural Population of the FrogBatrachyla taeniata

Relationships between testosterone plasma levels and evoked vocal responses of males of the leptodactylid frog Batrachyla taeniata from southern Chile were studied. Evoked vocal responses were elicited in the field with playbacks of a synthetic imitation of the conspecific advertisement call and variants of this signal for which different temporal parameters were modified. Testosterone plasma levels were measured with radioimmunoassay in blood samples obtained from the experimental subjects immediately after the playback experiments and from nonstimulated males. Testosterone levels between groups did not differ significantly. A significant correlation between testosterone concentration and number of calls given in response to the synthetic advertisement call was found. Testosterone levels were also significantly correlated with the total number of calls given by the experimental subjects in response to the complete series of stimuli. Other measures of evoked vocal responses, i.e., number of pulses per call, call duration, pulse rate, and latency to first call, were not significantly correlated with testosterone levels. These results indicate a predominant effect of testosterone on the motivation of males of B. taeniata to call, rather than on the physical attributes of the vocalizations.

Comparison of some behavioral and physiological feeding parameters of Triatoma infestans klug, 1834 and Mepraia spinolai porter, 1934, vectors of chagas disease in Chile

There are two vectors of Chagas disease in Chile: Triatoma infestans and Mepraia spinolai. We studied the feeding behavior of these species, looking for differences which could possibly explain the low impact of the latter species on Chagas disease. Both species used thermal cues to locate their feeding source and consumed a similar volume of blood which was inversely related to the body weight before the meal and directly related to the time between meals. The average time between bites were 6.24 and 10.74 days. The average bite of M. spinolai lasted 9.68 min, significantly shorter than the 19.46 min for T. infestans. Furthermore, while T. infestans always defecated on the host, this behavior was observed in M. spinolai in only one case of 27 (3.7%). The delay between the bites and defecation was very long in M. spinolai and short in T. infestans. These differences may affect the reduced efficiency of transmission of Chagas infection by M. spinolai.

Extent and variation of sound enhancement inside burrows of the frog Eupsophus emiliopugini (Leptodactylidae)

Abstract Variation of the amplification effect of burrows of the leptodactylid frog Eupsophus emiliopugini on conspecific calls generated externally was investigated. Advertisement calls broadcast through a loudspeaker placed in the vicinity of a burrow were monitored with small microphones positioned inside and outside the cavity. For 150 presentations of calls of 15 individuals in 12 burrows, 134 were amplified and 16 were attenuated (range –6–13 dB). The fundamental resonant frequency of burrows, measured with broadcast noise and pure tones, averaged 814 Hz (range 302–1361 Hz) and covaried with burrow length. The dominant frequency of the calls of burrow occupants (average 1062 Hz, range 636–1459 Hz) was not correlated with the fundamental resonant frequency of these cavities. In burrows with low resonant frequencies, externally broadcast calls with high dominant frequencies were attenuated, or amplified to a lower extent than calls with lower dominant frequencies. The dominant frequencies of the calls experienced shifts towards the burrows’ fundamental resonant frequencies. The amplification of calls inside burrows of E. emiliopugini exhibits manifest variability, with considerable potential for facilitating acoustic interactions in this species.

BIOLOGIA COMPARADA DE Mepraia spinolai EN CONDICIONES DE LABORATORIO Y TERRENO:: CINCO AÑOS DE ESTUDIO

En Chile se han descrito dos especies de Triatominos: Triatoma infestans y Mepraia spinolai. De estas, la primera es la mas estudiada por su importancia en el ciclo domestico de la enfermedad de Chagas en Chile y America. De la segunda en cambio, se conoce poco de su biologia e importancia epidemiologica. En este articulo, resumimos los aspectos mas relevantes de cinco anos de estudio en laboratorio y terreno de los triatominos chilenos, con enfasis en aspectos ecologicos, conductuales y epidemiologicos de M. spinolai. En nuestra experiencia ambas especies demuestran similitudes en sus dinamicas poblacionales, distribucion geografica y preferencias de temperatura en laboratorio. Las principales diferencias son de preferencia alimentaria y de tipo conductual, especialmente en el tiempo de picada que es mas corto en M. spinolai y la latencia de evacuacion que es muy larga en esta especie, lo cual explica en parte su bajo impacto epidemiologico

Adaptation of the spiders to the environment: the case of some Chilean species.

Spiders are small arthropods that have colonized terrestrial environments. These impose three main problems: (i) terrestrial habitats have large fluctuations in temperature and humidity; (ii) the internal concentration of water is higher than the external environment in spiders, which exposes them continually to water loss; and (iii) their small body size determines a large surface/volume ratio, affecting energy exchange and influencing the life strategy. In this review we focus on body design, energetic, thermal selection, and water balance characteristics of some spider species present in Chile and correlate our results with ecological and behavioral information. Preferred temperatures and critical temperatures of Chilean spiders vary among species and individuals and may be adjusted by phenotypic plasticity. For example in the mygalomorph high-altitude spider Paraphysa parvula the preferred temperature is similar to that of the lowland spider Grammostola rosea; but while P. parvula shows phenotypic plasticity, G. rosea does not. The araneomorph spiders Loxosceles laeta and Scytodes globula have greater daily variations in preferred temperatures at twilight and during the night, which are set to the nocturnal activity rhythms of these species. They also present acclimation of the minimum critical temperatures. Dysdera crocata has a low preferred temperature adjusted to its favorite prey, the woodlouse. Spider metabolic rate is low compared to other arthropods, which may be associated with its sit and wait predatory strategy particularly in primitive hunter and weavers. In mygalomorph spiders the respiratory system is highly optimized with high oxygen conductance, for example G. rosea needs only a difference of 0.12–0.16 kPa in the oxygen partial pressure across the air-hemolymph barrier to satisfy its resting oxygen consumption demands. Water loss is a significant stress for spiders. Paraphysa parvula shows an evaporative water loss 10 times more than usual when the temperature approaches 40°C and the participation of book lungs in this loss is about 60%. This species and others show seasonal changes in water loss accounted for by changes in cuticle permeability. The case of Chilean spiders shows how the ecophysiology in spiders is associated to their design and body size and how is affected by fluctuating Mediterranean environments, suggesting that the adaptive process can be seen as a route of optimizing the use of energy to cope with environmental restrictions imposed by the interaction with the terrestrial environment and lifestyle.

Geometría de los sistemas vivos y su importancia en Medicina

We analyze the most relevant concepts about complexity ofsciences, showing examples and consequences in medical sciences. In the first section weintroduce some basic concepts about fractals and its relationship with the geometry of natureand chaos dynamics. We also introduce notions of critic systems, the role of energy in them andwe propose a conceptual model for living systems. In this model we identify the non-lineardynamics as the dynamics of the living forms and fractals as the form resulting from thatdynamics. In the second section we review medical and biological examples: infectious diseases,cardiovascular and behavior dynamics, from which useful concepts and medical hypothesesemerge. One of the most important concepts, is the proposition that homeostasis would have anirregular dynamic. Then, we could expect that healthy individuals should be characterized byirregular dynamics, but old or sick individuals would change, probably decreasing thecomplexity of its dynamics. Therefore, we ask ourselves if the use of therapies to obtain aconstant internal medium can be a mistake (Rev Med Chile 2005; 133: 1097-107).(

Midbrain auditory sensitivity in toads of the genus Bufo (Amphibia - Bufonidae) with different vocal repertoires

SummarySouth American male toads Bufo chilensis emit a release call in contact with other individuals and a soft amplectic call, B. spinulosus males emit a release call while isolated in breeding areas, and B. arenarum produces a release call plus an intense mating call. Release calls of the 3 species measure 72–86 dB SPL RMS at 20 cm in front of the animal and the mating call of B. arenarum is 84–87 dB SPL at 4 m.Audiograms obtained with multiunit recordings in the torus semicircularis (TS) show a low frequency region (LFR), centered at 352, 356 and 491 Hz, and a high frequency region (HFR), centered at 1199, 1161 and 1423 Hz, in B. chilensis, B. spinulosus and B. arenarum, respectively. Center frequencies (CFs) in the HFR are in gross correspondence with average dominant frequencies (DFs) of the vocalizations of these species. Best thresholds (BTs) in the HFR are similar between B. chilensis and B. arenarum while in B. spinulosus average BTs are 10.8 and 13.5 dB higher, respectively. The similar auditory thresholds between B. chilensis and B. arenarum denote a conservative nature of auditory sensitivity among these anura.

Hissing Sounds by the Lizard Pristidactylus volcanensis

Abstract Lizards from different families use acoustic signals in different communicative contexts. This study characterizes the hissing sounds emitted by individuals of Pristidactylus volcanensis (Polychrotidae) of both sexes, when confronted with a threatening stimulus. These hissing sounds have broadband spectra centered at 2.4–3.6 kHz throughout most of the emission. In some cases the hisses end with a downward frequency modulation component within the frequency range of the ongoing signal. The structure of these sounds resembles the alarm signals produced by other vertebrates in response to extremely stressful situations, such as an imminent predator attack. The occurrence of sound production in other Polychrotidae suggests that these displays have an ancestral origin in the family; however, the scattered occurrence of acoustic signals in lizards, points to an independent evolution of sound production in different families of these reptiles.