Presented as Thesis (Ph. D.)--University of Wisconsin--Madison, 1914. / Cover title. Reprinted from Journal of morphology, vol. 25, no. 4 (Dec. 1914). Includes bibliographical references (leaves 627-629).

Thesis (M.A.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 43-48). Also available on the Internet.

Thesis (M.A.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 43-48). Also available on the Internet.

An investigation of Cambarus dubius and Cambarus carolinus was made in Tennessee to evaluate morphological Variation found in populations of these species and to determine aspects of life history and ecology. Taxonomic position and history of C. carolinus and C. dubius was reviewed and discussed. Three clines or possible subspecies in C. dubius were indicated in Tennessee based on both qualitative and quantitative evidence including: width and length of areola, shape and size of chelae, rostrum, central projection, mesial process, and color. C. dubius populations from northern West Virginia and southern Pennsylvania were significantly different from populations to the south. C. carolinus could not be separated by quantitative measurements from C. dubius, but could be distinguished on the basis of the central projection and other qualitative characters. Color phases were discussed for both C. dubius and C. carolinus. The range for both species in Tennessee was discussed and the range limits for C. dubius delineated. Life history and ecological data were reported for C. dubius and indicated for C. carolinus.

An investigation of Cambarus dubius and Cambarus carolinus was made in Tennessee to evaluate morphological Variation found in populations of these species and to determine aspects of life history and ecology. Taxonomic position and history of C. carolinus and C. dubius was reviewed and discussed. Three clines or possible subspecies in C. dubius were indicated in Tennessee based on both qualitative and quantitative evidence including: width and length of areola, shape and size of chelae, rostrum, central projection, mesial process, and color. C. dubius populations from northern West Virginia and southern Pennsylvania were significantly different from populations to the south. C. carolinus could not be separated by quantitative measurements from C. dubius, but could be distinguished on the basis of the central projection and other qualitative characters. Color phases were discussed for both C. dubius and C. carolinus. The range for both species in Tennessee was discussed and the range limits for C. dubius delineated. Life history and ecological data were reported for C. dubius and indicated for C. carolinus.

Population biology and acid tolerance of the crayfish Cambarus bartonii bartonii (Fabricius) from southern Appalachian Mountain streams were investigated. Field studies were conducted primarily from May through October, 1985 at Coweeta Hydrologic Laboratory (U. S. Forest Service Southeastern Experimental Station) in Otto, North Carolina, to describe selected population parameters and life history events for this species in two first-order streams. Laboratory experiments were conducted using crayfish from Coweeta and from Craig Creek (Jefferson National Forest, Montgomery County, Virginia) to determine median lethal concentrations (LC₅₀) for sulfuric acid exposure, and to investigate physiological effects, influence of ambient water temperature, and effects of episodic acid events on molting. Population estimates of crayfish ranged from 210 to 683 crayfish in 20 to 25m study sections (≃9.2 to 29.8 per m²) of Ball Creek and Pinnacle Branch. Mean catch per baited funnel trap and mean catch per hour of hand collecting were determined in three study sections of each stream in May and September to obtain relative abundance estimates and compare capture methods. Each method selected for different segments (size classes) of the population. Sex ratios were balanced (1:1) over the whole sampling season, but differed significantly from 1:1 in some months, probably due to reproductive activity. Sexually mature males and females (form I males, females with full cement glands) were observed in all months sampled. Acute (96h) laboratory lethality tests yielded LC₅₀ values for pH's of 2.43, 2.56, 2.85 and 2.43 for Coweeta intermolt adults (25.3 to 43.2mm carapace length, CL), late juveniles (11.5 to 19.9mm CL), early juveniles (3.9 to 12.8mm CL) and Craig Creek intermolt adults (23.0 to 41.3mm CL), respectively. Decreased water temperature resulted in increased acid tolerance of intermolt adults (LC₅₀ = pH 2.33), and increased survival time during severe acid exposure. Acid exposure of intermolt adults in relatively soft water affected internal ion regulation, causing decreased hemolymph [Na⁺] and increased [Ca⁺⁺]; no Ca⁺⁺ mobilization (loss) from carapaces was observed. Preliminary work showed that extreme acidification had visible adverse effects on molting adults, causing failure of exoskeletons to become rigid. Episodic acid events at Coweeta do not appear to be a direct mortality problem to C. b. bartonii at this time. However, this does not preclude the possibility of future problems, particularly sublethal effects to reproductive activity or early life history stages, if increasing acidification and gradual loss of soil buffering capacity of watersheds persists. / M.S.

Crayfish throughout North America, Europe, and Asia host assemblages of obligate ectosymbiotic annelid worms called branchiobdellidans. The work presented here is a detailed experimental and observational study of the ecological interactions between crayfish and their worms. In a comprehensive literature review, I show that branchiobdellidans have complex and context-dependent effects on their hosts, serving as both beneficial cleaners and tissue-consuming parasites. Using a field survey and laboratory experiments, I provide novel evidence for age-specific resistance as an adaptation to maximize life-long benefits of a mutualism. Specifically, I show that Cambarus crayfish display a consistent ontogenetic shift in resistance to the colonization of branchiobdellidans and this shift likely reflects underlying changes in the costs and benefits of symbiosis. I then show that this change in host resistance creates predictable patterns of symbiont diversity and composition throughout host ontogeny. Host resistance limits within-host symbiont communities to a few weakly interacting species, whereas relaxed resistance leads to more diverse symbiont communities that have strong interactions among symbiont taxa. Thus, host resistance has direct effects on within-host symbiont community structure by selectively filtering colonizing species, and indirect effects by moderating the strength of interactions among symbionts. Lastly, in a detailed study of the worm Cambarincola ingens, I depict a symbiont dispersal strategy that yields highly predictable transmission dynamics during pairwise host-host encounters and shows that variation in transmission dynamics can be explained by the fitness outcomes for dispersing symbionts. Field observations revealed that worm reproduction is contingent on host size and intraspecific competition for preferred microhabitats. Using a predictive model that assumes transmission of symbionts only when current conditions yield fitness below a minimum threshold, I was able to predict individual transmission events much more accurately than a comparable null model that assumed a fixed probability of transmission. My work provides empirical support for the emerging trend among researchers that advocates the adaptation of general ecological frameworks to understand symbiont population structure and diversity, but my work also emphasizes the value of detailed natural history studies to uncover system-specific ecological and co-evolutionary processes such as partner control mechanisms, symbiont microhabitat selections, and symbiont dispersal strategies. / Ph. D.

This dissertation focuses on increasing the understanding of the evolution processes that have contributed to the diversification of freshwater crayfish. Chapter one estimates the divergence time of the three crayfish families and tests the hypothesis that diversification is tied to the break-up of Pangaea, Gondwanna, and Laurasia. I find that the families of crayfish diverged prior to or in association with the break-up of the three super continents. Chapter two addresses the evolutionary history of the genus Cambarus, using molecular data to test hypotheses of relationships based on chela and carapace morphology. The results provide evidence that the morphology used to determine Cambarus relationships do not reflect evolutionary history and that convergent evolution of morphological traits is common in crayfish. Chapter three addresses evolution at the population level and tests for differences in the genetic population structure of two crayfish with different physiological needs. I find that physiological requirements of these crayfish have influenced their population genetic structure. The last chapter addresses a molecular based hypothesis that rates of mitochondrial evolution are reduced in cave crayfish that have increased longevity, reduced metabolism, and restricted diets compared to surface crayfish. I find that cave crayfish rates of mitochondrial evolution do not significantly differ from surface crayfish. Therefore, increased longevity, reduced metabolism, and restricted diets do not slow the rate of mitochondrial evolution as predicted in this group of cave crayfish.

The focus of this research was the spontaneous magnetic alignment responses of animals. We show that snapping turtles (Chelydra serpentina) and crayfish (Cambarus sciotensis) spontaneously align their body axes relative to the magnetic field. In snapping turtles, this response is sensitive to low-level radio frequency fields, consistent with a mechanism involving a light-dependent radical pair mechanism. Findings from the turtle experiments also suggest that the Earth's magnetic field plays an important role in encoding spatial information in novel surroundings, and may help to organize multiple locales into a 'mental map' of familiar space. Given the importance of magnetic input in many aspects of spatial behavior, another important finding was that magnetic alignment of yearling turtles was disrupted by high levels of maternally transferred mercury, an industrial waste product found at high levels in some fresh water ecosystems. In crayfish, we investigated the effects of ectosymbionts (Annelida: Branchiobdellida) on magnetic alignment responses. Interestingly, the response of crayfish to magnetic cues parallels the complex symbiotic interaction between crayfish and their ectosymbiotic worms, which changes from mutualistic to parasitic with increasing worm density. Our working hypothesis was that these changes in spatial behavior may increase or decrease contact to other crayfish, and therefore increase or decrease transmission rates. Next, to address the ontogeny of the SMA, we attempted to replicate an earlier study showing a possible magnetic alignment response in chicken embryos. Although chicken embryos did show non-random alignment, we were not able to find a magnetic effect. Alignment is also an important feature of animal constructions and is very likely to have fitness consequences, which we explored in woodpecker cavity alignments in a meta-analysis of available global data. The latitudinal and continental pattern in 23 species of woodpeckers suggests that an alignment response can have the proximate function to regulate microclimate in the cavity and therefore, presumably, optimize incubation temperatures and increase hatching success. Overall, the presented findings show how experimental and observational studies of spontaneous alignment behavior can provide insight into the ecology and sensory biology of a wide range of animals. / Ph. D.