Brazilian tegus (Tupinambis merianae) were instrumented with telemetry encoder implants that measured and broadcast heart rate (HR), breathing rate (fR), and deep body temperature (Tb) and were then allowed to freely roam in outdoor enclosures mimicking their natural environment for a full year (2004) in order to monitor the circadian and circannual patterns in behaviour and cardio-respiratory physiology. The year was divided up into 5 seasons based upon the physiology and behaviour of the tegus: early activity season (Sept.-Nov.), late activity season (Dec.-Feb.), entrance into hibernation (March-April), hibernation (May-July), and arousal from hibernation (August). The activity seasons were characterized by warm weather with frequent rainfall which slowly decreased in temperature and precipitation as tegus started entering hibernation so that the end of the dormant season was marked by dry, cold weather. Tegus in the early activity season demonstrated high activity associated with breeding demands, displayed elevated HR and fR, and were able to maintain a large temperature differential (4-7°C) between deep body temperature (Tb) and their respective burrow (Tburrow) during sleep. As the season progressed into late activity season, average Tb remained constant but average HR and fR progressively declined indicating nightly torpor. Periods of inactivity during the active seasons were rare and associated with inclement weather. Tegus entered hibernation through bouts of inactivity that progressively increased in frequency and duration. During this time, Tb was regulated but declined at different rates in regards to daytime and nighttime values. Heart rate through the entrance into hibernation and hibernation periods frequently demonstrated arrhythmias that increased in duration but decreased with frequency as hibernation progressed. Through hibernation, Tb continued to decline for the first month but HR and fR were constant, demonstrating a temperature independent suppression of metabolism. Through the hibernation season tegus sporadically aroused and emerged from their burrows to warm up and after a short basking period would return to the burrows and swiftly resume hibernation. While hibernating, heart rate was characteristically regular but breathing was sporadic orepisodic. Arousals became more frequent towards the end of hibernation so that when they entered arousal from hibernation season most tegus were emerging daily. At this time daily maximum deep body temperature (Tbmax) swiftly returned to active season values but nighttime daily minimum deep body temperature (Tbmirt) values only showed a gradual increase through August, indicating different body temperature set points (Tbset) for active and sleep states. Changes in heart rate and breathing rate during the year showed greatest correlation with changes in photoperiod, although throughout hibernation HR and fR also showed tight correlation with Tb.

Brazilian tegus (Tupinambis merianae) were instrumented with telemetry encoder implants that measured and broadcast heart rate (HR), breathing rate (fR), and deep body temperature (Tb) and were then allowed to freely roam in outdoor enclosures mimicking their natural environment for a full year (2004) in order to monitor the circadian and circannual patterns in behaviour and cardio-respiratory physiology. The year was divided up into 5 seasons based upon the physiology and behaviour of the tegus: early activity season (Sept.-Nov.), late activity season (Dec.-Feb.), entrance into hibernation (March-April), hibernation (May-July), and arousal from hibernation (August). The activity seasons were characterized by warm weather with frequent rainfall which slowly decreased in temperature and precipitation as tegus started entering hibernation so that the end of the dormant season was marked by dry, cold weather. Tegus in the early activity season demonstrated high activity associated with breeding demands, displayed elevated HR and fR, and were able to maintain a large temperature differential (4-7°C) between deep body temperature (Tb) and their respective burrow (Tburrow) during sleep. As the season progressed into late activity season, average Tb remained constant but average HR and fR progressively declined indicating nightly torpor. Periods of inactivity during the active seasons were rare and associated with inclement weather. Tegus entered hibernation through bouts of inactivity that progressively increased in frequency and duration. During this time, Tb was regulated but declined at different rates in regards to daytime and nighttime values. Heart rate through the entrance into hibernation and hibernation periods frequently demonstrated arrhythmias that increased in duration but decreased with frequency as hibernation progressed. Through hibernation, Tb continued to decline for the first month but HR and fR were constant, demonstrating a temperature independent suppression of metabolism. Through the hibernation season tegus sporadically aroused and emerged from their burrows to warm up and after a short basking period would return to the burrows and swiftly resume hibernation. While hibernating, heart rate was characteristically regular but breathing was sporadic orepisodic. Arousals became more frequent towards the end of hibernation so that when they entered arousal from hibernation season most tegus were emerging daily. At this time daily maximum deep body temperature (Tbmax) swiftly returned to active season values but nighttime daily minimum deep body temperature (Tbmirt) values only showed a gradual increase through August, indicating different body temperature set points (Tbset) for active and sleep states. Changes in heart rate and breathing rate during the year showed greatest correlation with changes in photoperiod, although throughout hibernation HR and fR also showed tight correlation with Tb. / Science, Faculty of / Zoology, Department of / Graduate

Faculty of Science School of Animal,Plant and Enviromental Studies 0204322k thibbitts@tamu.edu / I investigated three mechanisms (endurance rivalry, contest competition, and mate choice) of sexual selection and the influence of multiple signals on intrasexual and intersexual encounters in the common barking gecko (Ptenopus garrulus). Aspects of the ecology of barking geckos were also studied to facilitate the investigation of sexual selection. Barking geckos exhibited sexual size dimorphism in relation to head size, with males having wider heads. No differences in diet or size of prey ingested were observed between the sexes, indicating that niche divergence was not occurring. Therefore, the difference in head width was best explained by sexual selection (male contest competition). Barking gecko diet was dominated by termites by number and volume. The peak reproductive season was in October for both sexes. I used activity patterns to determine if males emerged before females from winter dormancy, a key assumption of the protandry-based mating system model. Activity patterns were significantly different between males and females. Males were active in higher numbers early in the breeding season. Male and female activity patterns along with evidence that male territories were established before female emergence, testicular recrudescence likely coincides with male emergence, and larger males have larger territories and better reproductive success, suggest that barking geckos have a protandry-based polygynous mating system. I also tested for clustering of geckos on the landscape to determine if barking geckos lek. Clustering was found to occur in some instances, but barking geckos did not iii meet the criteria for a ‘classical’ lek species because males use calling sites containing resources (a burrow) that are also used by females. Lizards frequently rely on chemical cues to detect the presence of a conspecific. Male lizards in particular, may chemically sample potential refuges to avoid rivals. Barking geckos were equally likely to use an artificial refuge scented by another male compared to a control, indicating that males do not use scent when selecting refuges. I assessed the role of two signals, one acoustic (dominant call frequency) and one visual (yellow throat patch), in advertising residency and aggressive behavior in barking geckos. Larger males defended the largest home ranges and home ranges were maintained through calling, which is negatively correlated with body size. Body size also predicted some behavioural responses to field-playback trials. Small males retreated from the playback and large males were found to be aggressive towards the playback. Small relative throat patch size was also correlated with aggression and charging the playback. Finally, call frequency was correlated with the behaviour of charging the playback. I suggest that the frequencies of barking gecko calls constitute a long-range signal of body size, used by males for remote rival assessment and to advertise home range boundaries. I also assessed the role of multiple signals (acoustic and visual) in reproductive success and I studied the effect of one mechanism of sexual selection, endurance iv rivalry, on reproductive success. Activity levels were similar for males which bred compared to those that did not breed, suggesting that endurance rivalry is not a significant mechanism of sexual selection in this population. Body size was the best predictor of reproductive success, suggesting that call frequency functions as a long range signal of body size used by females to assess potential mates.

Host-parasite relationships are one of the most common symbiotic relationships present in a diverse array of ecosystems. There are numerous factors that impact the dynamics of these relationships. Major factors that can influence the degree of parasitism include host sex, hormonal state, reproductive condition, and behavior. It has been observed in several vertebrate taxa that males have higher ectoparasite intensities than females and males with increased testosterone have increased ectoparasite intensities. One potential reason for these observations is that testosterone concentrations are elevated in males, particularly during the breeding season, and when circulating concentrations increase males become more vulnerable to ectoparasitism. Here I first tested the hypothesis that higher circulating testosterone concentrations in male western fence lizards (Sceloporus occidentalis) induce higher tick intensities. To examine this hypothesis I implanted male lizards with either testosterone or blank implants in the field. The testosterone-implanted males had significantly higher tick intensities compared to the control males. However, in contrast, control males had significantly higher mite intensities compared to testosterone-implanted males. These results are consistent with other studies suggesting that testosterone impacts certain aspects of host-parasite relationships. However, the exact mechanism for how testosterone influences parasite intensities remains unclear. There are two major current hypotheses for how testosterone influences ectoparasite intensities on males, the first involving immunosuppression and the second involving behavioral patterns and movement. However, another potential reason for why male lizards, particularly those with high circulating testosterone, have higher ectoparasite intensities than female and low testosterone male lizards is that the parasites preferentially choose their host. Furthermore, it has been demonstrated that vitellogenic female lizards have diminished immune function and this could potentially lead to increased ectoparasitism in much the same way that testosterone does in male lizards. Therefore, it is possible that a host preference is also present with vitellogenic versus non-vitellogenic female lizards. Although there have been a few interspecific studies done on this topic there have been no such studies on parasite host preference in reptiles to date. Here I tested three hypotheses: 1. Ticks prefer male lizards to female lizards. 2. Ticks prefer male lizards with high testosterone concentrations to male lizards with normal testosterone concentrations. 3. Ticks prefer vitellogenic female lizards to non-vitellogenic female lizards. All three experiments demonstrated no preference of host by ticks, which suggests they will attach to any suitable host they come across. However, during the male versus female host choice experiment ticks fed faster on vitellogenic female lizards than male lizards and non-vitellogenic female lizards. These results, taken together with previous studies showing higher tick intensities on male lizards, lizards with experimentally elevated testosterone, and reproductive female lizards, provide evidence that ticks do not preferentially choose their host, but instead are found in higher numbers on certain hosts due to some other reason. Other potential explanations include differences in immune function, microhabitat use, and behavioral patterns. One of the major hypotheses as to why male lizards, particularly those with high testosterone concentrations, have higher ectoparasite intensities than female lizards and male lizards with low testosterone concentrations is that these lizards perform more territorial behaviors, have increased movements, and larger home range sizes, thus exposing them to more parasites. Several studies have shown testosterone to increase the frequency of behaviors, movement, and home range size in lizards, but few, if any, have related it to ectoparasite intensities. Here I tested two hypotheses: 1. High testosterone male lizards have larger home ranges than male lizards with lower testosterone concentrations and female lizards. 2. High testosterone male lizards perform a higher frequency of territorial behaviors than male lizards with lower testosterone concentrations and female lizards. To test these hypotheses I implanted male lizards with either testosterone or blank-control implants, left female lizards unaltered, and performed behavioral observations in the field for 25 days. At the end of this time period, home range sizes were calculated as minimum convex polygons and ectoparasite intensities were quantified. Results of this study revealed no significant difference in ectoparasite intensities between high and low testosterone male lizards, but male lizards did have significantly higher ectoparasite intensities than female lizards. Furthermore, home range size and frequencies of territorial behaviors were not significantly different between high and low testosterone male lizards. However, male lizards did have larger home ranges and performed more territorial behaviors and movements than female lizards. These results suggest that home range, movement, and territorial behavior frequency contribute to higher ectoparasite intensities on male lizards, particularly those on males with high circulating testosterone. However, future studies need to address the behavioral and physiological mechanisms responsible for the observed effects of testosterone on parasitism, including parasite intensity, immunosuppression, and parasitic effects on host fitness.

Le climat affecte entre autre la phénologie, l’aire de distribution, le comportement et la physiologie des espèces. Le changement climatique a donc des répercussions sur chacun de ces facteurs. L’augmentation globale des températures prévue d’ici 2100 pourrait profondément modifier la biodiversité de l’échelle des espèces jusqu’à celle des écosystèmes. Les ectothermes, et en particulier les reptiles ovipares à détermination du sexe sensible à la température, font partie des organismes susceptibles d’être les plus vulnérables au réchauffement du climat puisque quasiment tous leurs traits d’histoire de vie dépendent de la température. L’origine et le maintien de ce mécanisme de détermination du sexe, pouvant conduire à un sex ratio fortement biaisé à l’échelle d’une population, reste une énigme pour les écologues. Parmi les nombreuses questions soulevées par la présence de ce mécanisme de détermination du sexe, la signification adaptative, s’il y en a une, de ce mécanisme est cruciale.Ce mécanisme de détermination du sexe rend-il les espèces plus vulnérables dans le contexte actuel du changement du climat ? Plusieurs hypothèses évolutives ont été proposées et des modèles de dynamique des populations sont disponibles pour répondre à ces questions. Cependant, prédire le sex ratio primaire en conditions naturelles, c’est-à-dire le sex ratio des nouveaux nés, reste un défi majeur à l’heure actuel. Ce manuscrit vise à apporter de nouveaux outils méthodologiques afin de correctement prédire le sex ratio d’une ponte en fonction de la température ressentie par les embryons au cours de l’incubation. Les tortues marines,quasiment toutes menacées, sont des espèces migratrices présentant toute ce mécanisme de détermination du sexe.Chez ces espèces, la phénologie des pontes est aussi sensible à la température du milieu. Ce type de plasticité phénotypique est probablement la stratégie la plus efficace pour pallier à un changement rapide du climat. Ce manuscrit apporte quelques éléments de réponse quant au potentiel adaptatif des tortues marines face au réchauffement climatique avec l’exemple de plusieurs populations de tortues Caouanne (Caretta caretta). / Climate affects, among other things, species’phenology, distribution range, behavior and physiology.Climate change thus impacts each of these factors. Global warming expected by 2100 might profoundly modify biodiversity from species to ecosystems. Ectotherms, and in particular oviparous reptiles with temperature dependent sex determination, are thought to be among the most vulnerable in the face of global warming because virtually all their life history traits depend on temperature.The origin and the persistence of temperature-dependent sex determination, which could lead to heavily biased population sex ratios, is still an enigma for ecologists. Among numerous issues related to this sex determining mechanism, understanding its adaptive significance, if there is one, is crucial. At another level, does this sex determining mechanism make species more vulnerable in the context of contemporary climate change ? Several evolutionary hypotheses have been proposed and population dynamic models are available to address these issues. However, predicting primary sex ratio, i.e., the sex ratio of hatchlings, in natural conditions currently remainsa challenge. This manuscript aims to bring new methodological tools to properly predict sex ratio of aclutch depending on temperature experienced by embryosthroughout incubation. Marine turtles, almost all being threatened, are migratory species that all exhibit this sex determining mechanism. For those species, nesting phenology is also sensitive to environmental temperature.This type of phenotypic plasticity is probably the most efficient strategy to keep up with rapid climate change.This manuscript provides some elements for understanding the adaptive potential of sea turtles in the face of global warming with the example of several).

Please read the abstract in the section, 00front, of this document / Dissertation (MSc)--University of Pretoria, 2008. / Zoology and Entomology / unrestricted

A jararaca-ilhoa (Bothrops insularis) é uma serpente endêmica e criticamente ameaçada de extinção que atualmente possui uma população estimada de 2.100 indivíduos restritos a uma única ilha no Estado de São Paulo, a Ilha da Queimada Grande. Esta vulnerabilidade levou à criação de um programa de reprodução em cativeiro para a espécie que, entre outras ações, propõe o desenvolvimento e aplicação de biotécnicas reprodutivas, tais como avaliação e preservação seminal e inseminação artificial. Este trabalho teve como objetivos: (1) avaliar três diluidores (HAM F-10, ACP-120® e BWW) em três diluições diferentes (1:100, 1:200 e 1:500 µL) e determinar qual o melhor protocolo de incubação para o sêmen de B. insularis; (2) avaliar um protocolo de inseminação artificial na espécie e (3) avaliar três diferentes sistemas de refrigeração (geladeira, banho-maria em geladeira e isopor tipo BotuFLEX® )a fim de determinar qual deles é capaz de preservar melhor a motilidade do sêmen da jararaca-ilhoa por um período de até 48 h. Verificamos que as amostras de sêmen diluídas com o meio HAM F-10 na diluição 1:100 µL apresentaram os melhores resultados para motilidade e motilidade progressiva e, desta forma, foi o protocolo de diluição seminal eleito para a inseminação artificial realizada. O protocolo de inseminação artificial foi realizando de maneira segura e minimamente invasiva nos animais, no entanto, até o momento não houve detecção de prenhez nas fêmeas inseminadas. A refrigeração se mostrou um método eficiente para a manutenção da motilidade e motilidade progressiva do sêmen de B. insularis por até 48 h pois, no período de duração do experimento, não foi verificada queda significativa nos parâmetros avaliados em nenhum dos sistemas de refrigeração. Foi observada, ao longo deste trabalho, uma alta incidência de decapitações nos espermatozoides de boa parte dos machos, o que pode comprometer seriamente a fertilidade do plantel estudado. Acreditamos, com os resultados deste projeto, ter elucidado questões fundamentais acerca do melhor diluidor e diluição a ser utilizada na manipulação do sêmen de B. insularis, assim como ter demonstrado que protocolos de refrigeração seguros e versáteis são capazes de manter a motilidade seminal por até 48 h, permitindo a troca de material genético entre diferentes plantéis no Brasil ou até mesmo com a população nativa da Ilha da Queimada Grande. O conhecimento gerado a partir deste estudo também servirá como base para estudos que visem o estabelecimento e aprimoramento de outras biotécnicas reprodutivas e a criação, em um futuro breve, de um banco de germoplasma da espécie. / The golden lancehead (Bothrops insularis) is a venomous pitviper endemic from Ilha da Queimada Grande, a small island located 40 miles off the coast of southeastern Brazil. Due to its small population (about 2000 individuals), highly restricted range, continuous decrease in habitat quality and illegal trading, B. insularis is currently listed as critically endangered in the IUCN Red List. As a consequence, efforts have been directed towards the development of a captive breeding program that involves both natural and assisted reproduction. Nonetheless, successful application of assisted reproductive technologies such as artificial insemination and semen cryopreservation in B. insularis requires a clear understanding of the reproductive physiology of this species, particularly aspects of sperm quality and production, and conservation. Thus, this study aims on: (1) determining which extenders (ACP-120, BWW and HAM-F10) and dilutions are better suited for maintenance of sperm motility; (2) testing an artificial insemination protocol in B. insularis maintained in captivity; (3) evaluating three different cooling systems (refrigerator, water bath on refrigerator and BotuFLEX®) to determine which one is able to preserve the semen motility of the golden lancehead for a period up to 48 hours. We found that semen samples diluted with HAM F-10 medium at a 1: 100µL dilution had the best motility and progressive motility results. To date, no pregnancies have been detected in inseminated females. Therefore, further studies and the improvement of this protocol for the species are required. We observed that all three cooling methods work successfully, maintaining the motility and progressive semen motility without significant changes for 48h, which demonstrates versatility in the preservation and transportation of this material, including from field work. With our results, we have elucidated fundamental questions about both the best diluent and dilution to be used, as well as refrigeration systems that ensure the maintenance of semen motility up to 48 hours. This is crucial for allowing the exchange of genetic material between different Brazilian Institutions and the income of material from Ilha da Queimada Grande, what may minimize problems due to consanguinity, besides serving as a basis for future studies on seminal cryopreservation protocols and the creation of germplasm banks.

Despite long-term study, the mechanism explaining the parapatric distribution of two Australian reptile ticks species, Bothriocroton hydrosauri and Amblyomma limbatum, is not understood. This project aimed to use molecular genetic data to investigate aspects of the population biology of these two tick species, such as population structure and dispersal, to gain further insights into the cause and maintenance of this parapatric boundary. I developed and subsequently tested for Mendelian inheritance a suite of B. hydrosauri and A. limbatum species-specific microsatellites markers. Pedigree analysis showed one B. hydrosauri locus and all of the A. limbatum loci to be inherited in a non-Mendelian manner. Thus I could not investigate A. limbatum population structure and focused solely on B. hydrosauri. The first part of this study tested predictions of a model formulated to explain B. hydrosauri transmission dynamics. The “ripple” model, based on detailed ecological and behavioural data on B. hydrosauri and Tiliqua rugosa, B. hydrosauri’s most common host, predicts higher relatedness among larvae than among nymphs or adults on a host, and significant spatial autocorrelation in larvae extending further than for the later life stages. The model also predicts that adult ticks are likely to encounter related partners and that this will generate inbreeding within the population. I tested those predictions using nine microsatellite loci on a sample of 848 ticks (464 larvae, 140 nymphs and 244 adults) collected from 98 T. rugosa hosts at the northern edge of B. hydrosauri’s distribution range. My data did support all of the predictions of the “ripple” model and indicated that the dynamics of transmission among hosts play an important role in parasite population structure. The second part of this project focused on investigating the population genetic structure of B. hydrosauri at the edge of its geographic range and testing the predictions of a population model derived to explain B. hydrosauri’s parapatric boundary with A. limbatum. The “ridge and trough” model suggested the tick population was organised spatially into a series of “ridges” where tick density was high and “troughs” where it was low. Genetically, the expectation was to find clusters of more closely related individuals associated with the ridges. Cluster analysis of microsatellite allele frequencies and analysis of molecular variance of mitochondrial haplotype frequencies revealed the presence of four genetic clusters within a sample of 244 B. hydrosauri adults. As the highly genetically divergent clusters had overlapping distributions, and in some cases were syntopic, the genetic population structure predicted for these ticks by the “ridge and trough” model was not observed. Several explanations were considered for the observed B. hydrosauri genetic population structure, but syntopy of the clusters suggested that assortative mating is the most likely. I speculated that the clusters have formed in allopatry, when the environment was extremely heterogeneous, such that the ticks (and their hosts) were confined to isolated patches of high-quality habitat. Given sufficient time, this could have resulted in reproductive incompatibility between ticks occupying different patches. The population structure I uncovered indicates subsequent secondary recontact of divergent groups. Although my study allowed for a better understanding of B. hydrosauri biology and population structure, the reasons for the parapatric distributions of B. hydrosauri and A. limbatum are still unclear. Further research should focus on investigating the population genetic structure of A. limbatum at the edge of its range, as well as on performing a larger-scale study of B. hydrosauri population genetic structure and a more detailed investigation of the applicability of the “ridge and trough” model to this tick species. Moreover, it will be useful to inspect the population structure of both these species within the centers of their ranges and compare these findings with population structure found at the edge of the range.

The leopard gecko (Eublepharis macularius) is a reptile species in which embryonic temperature contributes both to sex determination and within- sex polymorphisms. Its life history makes the leopard gecko a model system for seeking ontogenic and proximate explanations for within-sex variation in sexually dimorphic behavior and neurophysiology, necessary attributes for reproductive success. For my dissertation I have incorporated the role of androgens that potentially modulate incubation temperature effects on behavioral and brain variation, which I approached using embryo and adult leopard geckos. First, I found that that the bias of same-sex clutch siblings is primarily incubation temperature- dependent and any maternal or genetic effects on same-sex clutch siblings are secondary. Second, I found that testosterone concentrations in the yolk-albumen were higher in eggs of late development than early development at 26 °C, a female-producing incubation temperature, but did not differ from eggs incubated at another female-biased temperature. This increase in testosterone concentrations during the temperature sensitive period in putative females is a finding opposite of reported trends in most other reptiles studied to date. Further, I found that the embryonic environment influences male sociosexual investigation in the absence of gonadal hormones. Lastly, in adult males of 32.5 °C, a male-biased incubation temperature, I found that the phosphoprotein DARPP-32 that is activated by the D1 dopamine receptor in limbic brain regions is correlated to this sociosexual investigatory behavior. Neurons immunopositive for phosphorylated DARPP-32 were not only less dense in the nucleus accumbens of males who spent more time with other males, but also more dense in the preoptic area of males who spent more time with females. The use of phosphorylated DARPP-32 as marker for sociosexual exposure is novel in a lizard species. Taken together, in support of previous studies, these results show that differences in embryonic environment stem primarily from incubation temperature, can explain behavioral differences in adulthood in the absence of hormones, and, in concert with hormonal manipulation, can influence neuronal marker sensitivity to sociosexual exposure. / text

No description available.