While a significant degree of salinity tolerance has been observed in the bivalve mollusk species Corbicula fluminea, the physiological and behavioral responses to changes in salinity by these organisms are not completely understood. It was hypothesized that Corbicula would initially avoid any salinity stress behaviorally through valve closure, but would eventually have to open to dispel anaerobic waste products and deal with the salinity. To explore this, Corbicula were collected and put through a series of experiments at salinity exposures of 0, 2.5, and 5.0ppt, with tissue water content and hemolymph osmolality being measured. After an initial 96-hour exposure period, it was observed that the tissue water content ratio of clams in 2.5ppt and 5.0ppt water dropped below that of the control groups in 0ppt. After a 24-hour time course experiment, it was observed that this change in tissue water largely occurred within the first eight hours of exposure for the 2.5ppt and 5.0ppt groups. It was also noted that the hemolymph osmolality of both the 2.5ppt and 5.0ppt groups rose to match the osmolality of the water in roughly the same time span. The osmolality of the control group did not match the osmolality of the 0ppt water, but was held at a constant level above it. In a later experiment measuring the same variables for clams in 10.0ppt, it was found that the tissue water and osmolality did not begin to change significantly until after 12 hours. The findings suggest that Corbicula osmoregulate at salinities lower than 2.5ppt, but osmoconform in salinities above that threshold. Furthermore, it seems that the clams are able and willing to tolerate conformation at 2.5ppt and 5.0ppt, but that they are reluctant to conform in 10.0ppt, behaviorally avoiding exposure for as long as possible.

Native bees are only recently gaining attention for the extent to which they aid in pollination and ecosystem services. These services are threatened by predictions of warming temperatures if bees are not able to respond. Voltinism - the number of generations produced annually- can strongly influence thermal conditions experienced by both developing and adult bees based on emergence strategies for each voltinism type. Differences in experienced thermal conditions brought on by climate change could therefore affect upper thermal limits (UTL) in bees. This study observes UTLs across a foraging season within and among native bee species vi to elucidate the potential response by bees to a warming climate. Bees were collected across the field season in Central Virginia and subjected to dynamic ramping trials to determine the fatal knockdown point (FKP). Results show in both univoltine and multivoltine bees an increase in upper thermal tolerance as the foraging season progresses (in quadratic and linear fashions respectively). Within multivoltine bees, FKP was related to nest type; with stem-nesting bees having the highest FKP. All average FKPs were higher than historic air temperatures of the study region, but within several degrees of the highest recorded maximum temperature. The diversity of responses in native bees provides evidence for both genetic and plastic responses to extreme temperature. While bees still face a potential myriad of other issues brought on by climate change, the observed increases in FKP across warming temperatures offer tentatively hopeful predictions for limited physiological responses in native bees to a warming climate

Wildlife in captivity has a long history of benefiting global conservation goals. Captive animals can raise awareness and appreciation for the conservation of endangered species. Additionally, captive animals can be used as source populations to reintroduce animals back to the wild or to supplement existing wild populations. The rapid increase in amphibian species threatened with imminent extinction has necessitated the creation of dozens of captive-breeding programs. The focus of this dissertation has integrated topics across the spectrum of animals in captivity and the wild, and the results provide useful recommendations for conservation action. First, I describe how market pressures over a 28-year period are causing meteoric increases in the prices of amphibians sold in the pet trade, indicating a high risk of overexploitation. Pet amphibians may facilitate greater understanding and appreciation of amphibians, but the pet trade must be sustainable. Improving amphibian husbandry will increase the number of captive-bred animals available in the pet trade, and it will allow greater production of threatened species for reintroductions. Secondly, by performing a systematic review of husbandry for 289 amphibian species native to the US, I identified a critical lack in taxon-specific husbandry and developed husbandry research prioritizations. Next, I used a combination of laboratory and field studies to examine domestication processes in amphibians by comparing defensive behaviors in two species of captive-bred and wild poison frog. Captive-bred amphibians had significantly reduced defensive behaviors compared to wild conspecifics, likely resulting from habitation processes related to their husbandry. Finally, I performed three reintroductions of the critically endangered Wyoming Toad (Anaxyrus baxteri) in Wyoming, US. I demonstrated how providing a transitionary period, called a soft-release, to captive-bred toads moving to a novel, wild environment can improve reintroduction success. My work illustrates how improving our understanding of the nexus between captivity and the wild can improve conservation action for endangered species.

The resilience of coral reefs depends, among others, upon local physical and biological characteristics. This dissertation focused on how herbivory, structural complexity, and sedimentation can impact the structure, function, and, ultimately, resilience of Caribbean coral reefs. We filled an important knowledge gap related to trophic niche and ecological roles of surgeonfishes (A. coeruleus and A. tractus), two of the most important herbivorous fishes in the Caribbean. We showed that both species feed primarily on turf algae preventing further progression of algal succession while A. tractus may also help reduce macroalgal abundance by targeting common macroalgal species such as Dictyota spp. We used a factorial experiment to analyze the interactive effects of herbivory (exclosure vs. open plots) and reef structural complexity (vertical vs. horizontal substrate orientation), on the development of benthic communities. We found that vertical substrates were quickly dominated by crustose algae regardless of herbivory treatment while succession of horizontal substrates was determined by herbivory. Our results suggest that at small scale, reef complexity is a major factor determining algal community structure. We investigated why, despite high levels of herbivory, coral cover in South Florida has failed to recover. We surveyed benthic composition, grazing and abiotic characteristics along six spur and groove reefs in the Florida Keys. Using boosted regression tree analyses, we found that sediment abundance was the best predictor of both juvenile and adult corals, which could explain the failure of coral recovery. We studied spatial and temporal changes of reef communities of reefs in Havana, Cuba where global and local stressors have affected coral communities while overfishing and nutrient enrichment has led to low herbivory levels. Our surveys revealed a region-wide high abundance of algae (~60%) as a consequence of heavy overfishing with likely negative consequences on coral recovery. In summary, my dissertation showed context-depend effects of herbivory, structural complexity, and sediment on Caribbean coral reefs. While reduction of herbivory can often suppress coral recovery, on coral reefs with robust herbivore populations, physical factors such as structural complexity and sediment may still limit coral recovery and fundamentally impact reef resilience.

The social behavior of brown bears (Ursus arctos) was studied during the summers of 1972 and 1973 as bears fished for salmon at McNeil River, Alaska. Study objectives were to determine behavioral characteristics of bears in relation to sex and age, changes in social behavior over a 40-day long fishing season, social and environmental parameters correlated with the occurrence of behavior, and to test the hypothesis that brown bears modify social behavior in a feeding aggregation to exploit a resource limited in time and space. Over one-half of the agonistic interactions consisted of passive deferrals. Encounters that included elements of overt threat were jawing, sparring, charges, and fighting. Jawing was the most prevalent agonistic encounter and generally occurred between individuals of the same sex and age class. Sparring, charges and fights were generally initiated by larger bears against smaller individuals. Females with young were most intolerant. Adult males participated in few encounters that involved overt threat since most bears avoided them. Single adult and adolescent females were neither particularly aggressive nor especially tolerant. Adolescent males adjusted quickly to McNeil Falls and as a group were unaggressive. Subadults were wary and frequently were the objects of aggression of older bears. Social dominance relationships between bears of the same class were often ambiguous, the exception being adult males. Relationships between bears of different classes were mostly stable; adult males were dominant, followed in order by females with young, single adult females, adolescents, and subadults. However, apparent reversals also were common between single adult females and adolescent males. Nonagonistic encounters occurred only when salmon were exceptionally abundant and usually involved adolescent and subadult bears. Behavioral changes over time included a decline in the frequency of running deferrals, a decline in deferrals in total, and a decline in the frequency of charges. The occurrence of fighting and sparring encounters did not change, but the frequency of jawing increased within each fishing season. Various factors determined salmon caught by a bear per hour of fishing effort: salmon abundance, water levels, time of day, and fishing location. The time of day a bear could fish and its choice of location depended on its ability to gain and defend a profitable site. Fishing success was directly correlated with social status, but differences in success are probably unimportant in terms of individual fitness except when salmon are relatively scarce. Changes in encounter intensity over time had no detectable effect on fishing success. Salmon abundance, however, resulted in a further reduction of agonistic encounter intensity and an increase in nonagonistic encounters. Bear social relationships were governed largely by variations in resource abundance. Despite energetic and psychological costs imposed by the bear concentration on individual animals, salmon were evidently sufficiently numerous that these costs were outweighted by returns in protein. Dominance relationships at McNeil Falls did not correspond to predictions of classical dominance theory. This may have been partially attributable to the fact that bears in aggregations derive no benefits from tacit acceptance of subordinate roles; a bear's alternatives were to compete and gain access to food or, if unsuccessful, to try elsewhere. To pose the question if normally solitary bears can adapt behaviorally to efficiently exploit a localized source of food may have been inappropriate. Alternatively, bears can be viewed as occupying and defending areas akin to small territories, with their behavior explicable in terms of energetic costs and benefits based on variations in resource abundance.

Aggregative feeding is widespread in Lepidopteran larvae suggesting that this behavior serves on adaptive function. Many studies of the potential benefits of aggregative feeding in Lepidopteran larvae have been conducted. However, no studies have directly examined the benefits of cryptic larvae being both chemically defended and gregarious. Group feeding occurs disproportionately more in chemically defended larvae than in larvae that have no chemical defense. Most of these larvae are cryptic when they are most highly aggregated and most vulnerable to predation. In this study, the benefits of group feeding in terms of decreased predation were explored in first instar larvae of pipevine swallowtail larvae, Battus philenor, a species that exhibits chemical sequestration. Contrary to our expectation, we found that groups of larvae fed a diet with high levels of the toxin aristolochic acid, which they sequester naturally and use as a defense against natural enemies, had significantly lower survivorship due to predation in both the field and in the laboratory experiments compared to groups of larvae fed a diet with low aristolochic acid content. We also found that aristolochic acid does not deter the generalist predator Hippodamia convergens, the ladybird beetle, suggesting that this compound is not a universal predator deterrent as previously assumed. Thus, instead of finding a benefit to group feeding and chemical defense in cryptic larvae, we have found a negative impact of group feeding in this population of B. philenor. Based on this evidence, we speculate that other benefits of group feeding might be outweighing the negative consequences of increased predation during the first instar. Future research on chemical defense, aposematism, and aggregative feeding should take into consideration that chemical defenses might not be universally effective against all natural enemies.

Webs are fundamental to the ecology of Nephila clavipes, the golden orb-weaver spider, because they serve as sites for prey capture, reproduction, competition, predation, and parasitism. In addition to the presence of the female N. clavipes, males and kleptoparasites reside on the web in varying numbers. Webs are also found in clusters with conspecific females. Web site selection and length of web tenure is a behavioral decision vital to the spider’s fitness and the ecology of her species. I conducted a field census to quantify these factors and analyze their influence on web tenure, compare web ecology between a forest and non-forest habitat, as well as explain the significance of N. clavipes’ web as central to many interactions. Web tenure, as well, was influenced differently by the factors between both environments. In the forest habitat, increase in prey capture rate decreased web tenure and inclusion in cluster increased web tenure. In the non-forest habitat, only increase in spider size was related to increased web tenure. There were significant differences between the two habitats in the sizes of the female spider and quantity of males and kleptoparasites. Results also showed that spider size influenced quantity of males and web diameter influenced quantity of kleptoparasites. Explanation of these results can be attributed to the complex relationships among the variables and the consequences of living in habitats impacted by human occupation.

Loss of hair cells due to acoustic trauma results in the loss of hearing. In humans, unlike other vertebrates, the mechanism of hair cell regeneration is not possible. The molecular mechanisms that underlie this regeneration in nonmammalian vertebrates remain elusive. To understand the gene regulation during hair cell regeneration, our previous microarray study on zebrafish inner ears found that growth hormone (GH) was significantly upregulated after noise exposure. In this current study, we utilized Next Generation Sequencing (NGS) to examine the genes and pathways that are significantly regulated in the zebrafish inner ear following sound exposure and GH injection. Four groups of 20 zebrafish each were exposed to a 150 Hz tone at 179 dB re 1μPa RMS for 40 h. Zebrafish were injected with either salmon GH, phosphate buffer or zebrafish GH antagonist following acoustic exposure, and one baseline group received no acoustic stimulus or injection. RNA was extracted from ear tissues at 1 and 2 days post-trauma, and cDNA was synthesized for NGS. The reads from Illumina Pipeline version SCS 2.8.0 were aligned using TopHat and annotated using Cufflinks. The statistically significant differentially expressed transcripts were identified using Cuffdiff for six different pairwise comparisons and were analyzed using Ingenuity Pathway Analysis. I found significant regulation of growth factors such as GH, prolactin and fibroblast growth factor receptor 2, different families of solute carrier molecules, cell adhesion molecules such as CDH17 and CDH23, and other transcription factors such as Fos, FosB, Jun that regulate apoptosis. Analysis of the cell proliferation network in the GH-injected condition compared to buffer-injected day 1 showed significant up-regulation of GH while downregulation of apoptotic transcription factors was found. In contrast, the antagonist-injected condition compared to the GH-injected condition showed an opposite pattern in which up-regulation of apoptotic transcription factors were found while GH was down-regulated. A number of other transcripts (e.g., POMC, SLC6A12, TMEM27, HNF4A, CDH17 and FGFR2) that showed up-regulation in GH-injected condition showed down-regulation in antagonist-injected condition. These results strongly suggest that injection of exogenous GH potentially has a protective role in the zebrafish inner ear following acoustic trauma.

Loricariidae is a very diverse family of catfishes found primarily in the Amazon River basin. These catfishes have a unique characteristic feature of having fenestrae (holes) in the skull region (compound pterotic bone) adjacent to their bi-lobed swim bladder. Since the swim bladders and the compound pterotic may act as an external ear for hearing in this taxon, I hypothesized that these swim bladders structures have an acoustical functional in the loricariid Otocinclus affinis. In order to understand the development of these structures in O. affinis, I first monitored the ontogeny of the compound pterotic bone by clearing and staining of fish ranging total length from 0.75 to 3.5 cm. the swim bladders and fenestrated compound pterotic bone were developed at early larval stages (by 5.25 mm TL). Second I examined the role of swim bladders in hearing in adult O. affinis, by testing the hearing sensitivity before and after swim bladder deflation. Hearing thresholds were determined electrophysiologically by recording auditory evoked potentials (AEP). Swim bladder deflation increased hearing thresholds by 19 – 23 decibels (dB). I then tested the role of the compound pterotic bone fenestrae in hearing by covering them with a tissue adhesive (n-butyl cyanoacrylate) and recording the hearing thresholds. Covering fenestrae increased hearing thresholds by 4 – 11 dB. Future experiments are required to more precisely determine the acoustical role of these peripheral auditory structures in O. affinis.

Webs are fundamental to the ecology of Nephila clavipes, the golden orb-weaver spider, because they serve as sites for prey capture, reproduction, competition, predation, and parasitism. In addition to the presence of the female N. clavipes, males and kleptoparasites reside on the web in varying numbers. Webs are also found in clusters with conspecific females. Web site selection and length of web tenure is a behavioral decision vital to the spider’s fitness and the ecology of her species. I conducted a field census to quantify these factors and analyze their influence on web tenure, compare web ecology between a forest and non-forest habitat, as well as explain the significance of N. clavipes’ web as central to many interactions. Web tenure, as well, was influenced differently by the factors between both environments. In the forest habitat, increase in prey capture rate decreased web tenure and inclusion in cluster increased web tenure. In the non-forest habitat, only increase in spider size was related to increased web tenure. There were significant differences between the two habitats in the sizes of the female spider and quantity of males and kleptoparasites. Results also showed that spider size influenced quantity of males and web diameter influenced quantity of kleptoparasites. Explanation of these results can be attributed to the complex relationships among the variables and the consequences of living in habitats impacted by human occupation.