Made available in DSpace on 2015-03-26T13:30:25Z (GMT). No. of bitstreams: 1 texto completo.pdf: 3602512 bytes, checksum: 1ab027615369085e321be8cda2af7474 (MD5) Previous issue date: 2009-06-26 / Paragryllini Desutter is a Neotropical tribe of crickets with species distributed from southern Mexico to Brazil. Currently are known 24 species assigned to six genera: Benoistella Uvarov, 1939; Mexiacla Gorochov, 2007; Oaxacla Gorochov, 2007; Paragryllus Guérin- Méneville, 1844; Rumea Desutter, 1988; and Silvastella Desutter- Grandcolas, 1992. In this paper new taxa from the Brazilian Central Amazonia are described. The genus Rumea is reported for the first time from this region, represented by three new species from the Central Amazonian: R. zebra sp. nov., R. manauensis sp. nov. and R. tigris sp. nov. Also two new genera are described: Marciela gen. nov., including M. longipes sp. nov. from Brazil and M. crybelos (Nischk & Otte, 2000) comb. nov. from Ecuador; and Sperberus gen. nov. including only S. arboricolus sp. nov. The morphology of the male genitalia of the Rumea species is discussed and a new interpretation is proposed. For the illustration of the genitalia of males and females a photographic technique was used: the structure was immersed in glycerin and photographs were taken on different levels of focous. For the construction of the final images the free software CombineZM was used. The biogeography of the Paragryllini is discussed based on the known distribution of the species. This study contributes to the knowledge of the group, increases its geographical distribution, and may serve as a starting point for future research on the Paragryllini in Brazil. / Paragryllini Desutter é uma tribo Neotropical com espécies distribuídas do sul do México até o Brasil. Atualmente são conhecidas 24 espécies subordinadas a 6 gêneros: Benoistella Uvarov, 1939; Mexiacla Gorochov, 2007; Oaxacla Gorochov, 2007; Paragryllus Guérin-Méneville, 1844; Rumea Desutter, 1988; e Silvastella Desutter-Grandcolas, 1992. Nesta dissertação são descritos novos táxons de Paragryllini da Amazônia Central brasileira. Faz-se o primeiro registro do gênero Rumea para esta área, com a descrição de três espécies novas: R. zebra sp. nov., R. manauensis sp. nov. e R. tigris sp. nov.. Também são descritos dois gêneros novos: Marciela gen. nov., que inclui Marciela longipes sp. Nov. do Brasil e Marciela crybelos (Nischk & Otte, 2000) comb. nov. do Equador; e Sperberus gen. nov. incluindo unicamente Sperberus arboricola sp. nov. Para as espécies do gênero Rumea, discutem-se as características morfológicas da genitália dos machos e se propõe uma nova interpretação da dessa estrutura. Para ilustrar a genitália tanto dos machos quanto das fêmeas, desenvolveu-se uma técnica de fotografia: a estrutura era inmersa em glicerina e eran tiradas fotografias em diferentes níveis de foco. Para a construção da fotografia final usou-se o software livre CombineZM. Discutem-se alguns aspectos biogeográficos baseados na distribuição conhecida das espécies de Paragryllini. Este estudo proporciona um aporte para o conhecimento do grupo, já que se amplia sua dibribuiçao geográfica, e puede servir como um punto de partida para futuras pesquiças sobre os Paragryllini no Brasil.

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No description available.

Several animals, both vertebrate and invertebrate, communicate using sound and they do so in a non-ideal medium, the habitat in which they live. As acoustic signals pass through the habitat, they suffer loss of information due to signal degradation, which is often determined by the acoustic properties of the habitat. Understanding the influence of habitat-induced constraints on signaling is vital to the understanding of evolution of signal structure. Over time signals can evolve their temporal and/or spectral characteristics so as to resist or reduce degradation. Conversely, signalers may modify their behaviour so as to improve transmission for effective communication. The Acoustic Adaptation Hypothesis (AAH) predicts that given the properties of the habitat in which animals communicate, signals should evolve so as to maximize their broadcast range and the number of potential receivers. The prediction of the hypothesis is that signal transmission is best in the native habitat as compared to non-native habitats. Since its inception, the idea of acoustic adaptation has been tested in several vertebrate species including birds, mammals and frogs but rarely in invertebrates. Moreover, most of these studies have been carried out at the macrohabitat level, such as transmission in forests versus grasslands. For animals with limited mobility such as invertebrates, a finer level of investigation at the microhabitat level is more relevant. Only one study on cicadas has investigated the predictions of the AAH at the microhabitat level. Besides, investigations done at the community level are largely missing in the literature. The effect of height on signal transmission is well documented, however, only one study on birds has investigated the AAH with respect to vertical stratification of coexisting species. Among invertebrates, crickets are well known for their calling songs which males use to attract conspecific females over long distances. No study so far has tested the prediction of the AAH in these acoustically communicating invertebrates. The central focus of this study was to test the predictions of the AAH in a natural assemblage of ensiferan (cricket) species. I examined the prediction of the hypothesis at the microhabitat level with respect to the vertical stratification of co-existing ensiferan species. The study was carried out on an assemblage of crickets in the wet evergreen forests of Kudremukh National Park in the Western Ghats in Southern India. For this purpose, it was important to examine calling height and microhabitat selection in these animals because if the use of calling height and microhabitat was random, then there would not be any native height/microhabitat and the question of acoustic adaption would not arise. Therefore, I first standardized methods to characterize the habitat of the crickets. Using resource selection functions, I then quantified microhabitat selection in 13 ensiferan species. I also examined the calling heights of these species. My results suggest that these species are microhabitat specialists and also distribute vertically within the forest with respect to calling height. Based on the knowledge of the vertical distribution of these animals in the forest I then carried out playback experiments using natural calls of 12 species of Ensifera in their natural habitat. The transmission experiments were carried out at five heights in the forest, including the ground, different parts of the understorey as well as in the canopy. The study aimed to examine whether vertical stratification in the ensiferan species of Kudremukh is driven by selection for maximizing transmission range. I examined the effect of different heights on signal degradation. The investigation was carried out with respect to three different measures of signal degradation, namely, total attenuation, signal to noise ratio as well as envelope distortion. The results indicate a lack of overall support for the AAH with respect to vertical stratification of crickets in Kudremukh. However, a strong, independent effect of height of calling on signal degradation was found, with the ground being the worst layer for transmission and the mid-understorey (2 m) emerging to be good for all species with respect to all three measures of signal degradation. I then analysed the transmission data from a different point of view, exploring the possibility of evolution of signal structures that may confer some advantages in terms of signal transmission, given the habitat-induced constrains on signal propagation. The idea was to examine why certain species perform better than others in terms of signal transmission. This investigation was aimed at characterizing the effect of call features on signal attenuation. I found that temporal features of calls did not have a strong effect on height-specific signal attenuation. While call duration had no effect on signal attenuation, duty cycle did influence attenuation profiles of the calls, with high duty cycle calls performing better than low duty cycle calls. However, there was no interaction of height with the temporal features of calls, eliminating the possibility of these features being shaped by microhabitat or height dependent transmission characteristics. Spectral features of calls, on the other hand, affected signal attenuation very strongly. As expected, low frequency calls performed better than high frequency calls and pure tone calls fared much better than the broadband calls, especially on the ground and the canopy. To the best of my knowledge, this is the first study to carry out a rigorous quantification of microhabitat selection in Ensifera. This is also the first detailed examination of the Acoustic Adaptation Hypothesis at the microhabitat level, tested in a natural assemblage of coexisting invertebrate species.

Captive insectivores may consume invertebrates as all, or part of their overall diet. The challenge with feeding captive insectivores involves the limited number of invertebrate species that are commercially available, and the lack of key nutrients provided by these insects. Among these insects, a naturally occurring low concentration of calcium and an inverse calcium to phosphorus ratio may put insectivores at the risk of developing hypocalcemia. A strategy to correct this nutrient imbalance involves supplementing the insect diet with high concentrations of targeted nutrients – a term referred to as gut-loading. Current industry guidelines recommend feeding a supplemented diet for 48 to 72 h before offering the insect to an insectivore. In the present study, the mineral profile of adult crickets (Acheta domesticus) offered a maintenance diet (1.58% Ca, DMB) are compared to crickets offered a supplemented diet (11.32% Ca, DMB) over 120 h. The supplemented diet produced a cricket with significantly higher calcium concentration compared to the maintenance diet. The calcium concentration of crickets offered the supplemented diet was highest at 48 h (0.63%), but did not achieve a 1:1 Ca:P ratio nor meet the lowest reported nutrient requirements of carnivorous reptiles, omnivorous reptiles, or an insectivorous bird at various life stages. Although the supplemented diet improved the whole body calcium concentration in feeder crickets, the crickets do not provide adequate calcium, iron, or manganese to meet the requirement of insectivores. As evidenced by the current study, the supplemented crickets are not recommended to serve as the sole source of nutrition for an insectivore.

No description available.

Acoustic communication in orthopterans and anurans provides a suitable model system for studying the evolutionary mechanisms of sexual selection mainly because males use acoustic signals to attract females over long distances for pair formation. Females use these signals not only to localize conspecific males but also to discriminate between potential mates. Investigations on the effect of sexual selection on acoustic signals requires an understanding of how female preferences for different features of the acoustic signal affect male mating success under ecological constraints in wild populations. The effect of female preferences on male mating success depends on the mate sampling strategy that females employ to search for potential mates. Despite its relevance, female mate sampling strategies based on male acoustic signals have rarely investigated in orthopterans and anurans, especially in the field. Considering the elaborate knowledge of the role of sensory physiology in female phonotaxis behaviour and characterization of the male acoustic signal, I used the field cricket species Plebeiogryllus guttiventris as a model system in this study. In this thesis, I first investigated the ecology of callers in wild populations. I then investigated female mate sampling strategies by incorporating relevant information on the ecology of signalers and the sensory physiology of receivers. Amount of calling activity is a strong determinant of male mating success in acoustically communicating species such as orthopterans and anurans. While many studies in crickets have investigated the determinants of calling effort, patterns of variability in male calling effort in natural choruses remain largely unexplored. I therefore investigated the spatio-temporal dynamics of acoustic chorusing behaviour in a wild population. I first studied the consistency of calling activity by quantifying variation in male calling effort across multiple nights of calling using repeatability analysis. Callers were inconsistent in their calling effort across nights and did not optimize nightly calling effort to increase their total number of nights spent calling. Next, I investigated calling site fidelity of males across multiple nights by quantifying movement of callers. Callers frequently changed their calling site across calling nights with substantial displacement but without any significant directionality. Finally, I investigated trade-offs between within-night calling effort and energetically expensive calling song features such as call intensity and chirp rate. Calling effort was not correlated with any of the calling song features, suggesting that energetically expensive song features do not constrain male calling effort. The two key features of signaling behaviour, calling effort and call intensity, which determine the duration and spatial coverage of the sexual signal, are uncorrelated and function independently Acoustic signal variation and female preference for different signal components constitute the prerequisite framework to study the mechanisms of sexual selection that shape acoustic communication. Despite several studies of acoustic communication in crickets, information on both male calling song variation in the field and female preference in the same system is lacking for most species. First, I quantified variation in the spectral, temporal and amplitudinal characteristics of the male calling song in a wild population, at two temporal scales, within and across nights, using repeatability analysis. Carrier frequency (CF) was the most repeatable call trait across nights, whereas chirp period (CP) had low repeatability. I further investigated female preferences based on song features with high and low repeatability (CF and CP respectively). Females showed no consistent preferences for CF but were more attracted towards calls with higher rates (shorter CP). I also examined the effect of signal intensity, which is known to play a critical role in female phonotaxis behaviour, on female preferences for faster calls. Females preferred louder calls over faster ones, implying a dominant role for signal intensity in female evaluation of potential mates based on acoustic signals. Call intensity was also the only signal feature that was positively correlated with male size. In the final chapter, I investigated female mate sampling strategies based on acoustic signals using both theoretical and empirical approaches. Analytical models of mate sampling have demonstrated significant differences in individual fitness returns for different sampling strategies. However these models have rarely incorporated relevant information on the ecology of signalers and the sensory physiology of receivers. I used simulation models to compare the costs and benefits of different mate sampling strategies by incorporating information on relative spacing of callers in natural choruses and the effect of signal intensity on female phonotaxis behaviour. The strategy of mating with males that were louder at the female position emerged as the optimal sampling rule in the simulations. When tested empirically in the field using callers in natural choruses, females seemed to follow the optimal strategy of mating with males that were perceived as louder at their position.

This thesis represents a comprehensive examination of the phonotactic behaviour (i.e. attraction to sound) of the female Gryllus bimaculatus under laboratory conditions. Chapter 2 is the first study to analyze the effect of substrate texture on walking performance in crickets. Substrate texture is found to play an essential role in the phonotactic responses of G. bimaculatus. Smooth substrate texture has a detrimental effect due to slipping, whereas a rough texture results in optimal walking performance due to the friction with the walking legs. Chapter 3 represents the first detailed lifetime study analysing phonotaxis in crickets. My results demonstrate that the optimal age to test phonotaxis in G. bimaculatus females is from day 7 to 24 after the final moult. I also found that selectiveness was persistent with age. These findings contradict the female choosiness hypothesis. This study is also the first to describe the effect of senescence on phonotaxis in insects, as responsiveness decreases with age. Chapter 4 compares the phonotactic behaviour of female crickets from different laboratory-bred colonies. From six tested cricket lab colonies, I found three groups statistically different from each other. Females raised under laboratory conditions at the University of Cambridge and Anglia Ruskin University were most reponsive at a frequency of 4.5 kHz, whereas females bred in Tokushima University in Japan were tuned towards a higher frequency of 5 kHz. These results suggest a degree of artificial allopatric speciation. Comparisons with crickets bred under low-quality conditions in a local pet shop demonstrate a loss of responsiveness, indicating that breeding conditions have a direct effect on phonotactic responsivity. Chapter 5 is the first study to report the presence of phonotaxis in males of G. bimaculatus. Previously it was unknown if G. bimaculatus males were able to perform phonotaxis, given that they were only recognised as endurance signal producers. In the present study, only 20% of the studied males (N=70) performed a weak phonotactic response. This finding has potential ecological implications in terms of male cricket territory establishment, and male-male interactions in the wild, which are discussed. Chapter 6 explores the song pattern recognition of the female G. bimaculatus by changing the duration of either the first, second or third pulse of the chirps. A long first pulse decreased the phonotactic response whereas phonotaxis remained strong when the third pulse was long. Chirps with three pulses of increasing duration of 5, 20 and 50 ms elicited phonotaxis, but the chirps were not attractive when played in reverse order. The data are in agreement with a mechanism in which processing of a sound pulse has an effect on the processing of the subsequent pulse, as outlined in the flow of activity in a delay-line and coincidence-detector circuit.