Thesis (Ph.D.)--Bowling Green State University, 2007. / Document formatted into pages; contains xi, 94 p. : ill. Includes bibliographical references.

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In many taxa, social structures are mediated by agonistic interactions and the formation of dominance hierarchies. In crayfish, dominance hierarchies may have evolved as a result sexual selection, allowing dominant males greater access to females, thereby increasing their reproductive success. This work tests the hypothesis that high male investment in dominance interactions may have evolved as a result of intra- and/or inter-sexual selection pressures by testing specific predictions in two parts: first, that reproductive males would invest more in agonistic interactions than reproductive females or non-reproductive members of both sexes; and second, that females would prefer odors of dominant males over subordinates, and that dominant males would be either more efficient at mating or be able to mate longer than subordinates. Investment in agonistic interactions was examined in intrasexual pairs of male and female crayfish in both the reproductive and non-reproductive season. As predicted, reproductive males invested more in agonistic interactions overall than reproductive females, while there was no significant difference in investment by non-reproductive males or females. However, no significant difference was found in agonistic investment between reproductive males and non-reproductive males. These data indicate that investment in agonism differs by sex and by reproductive status, and may indicate that dominance interactions are under sexual selection in males. Alternatively, this differential investment may be explained by seasonal changes in the individual costs and benefits of agonism, or by depressed investment by reproductive females. Female odor preference was tested using a y-maze containing control and male treated water. For tests of male mating, time spent in each of three stages of mating was recorded for male-female pairs. Of these tests, the only significant trend produced was that dominant males spent more time associated with the female during and after copulation than subordinates. This may indicate an advantage in fertilization success for males through decreased sperm competition. A pilot study was also conducted testing the predictions that females mated to dominant males invest more in offspring than those mated to subordinates and that such offspring have greater survivability, but no significant conclusions could be drawn from these data.

Bioturbation by invasive crayfish can significantly alter sediment properties and its transport in invaded water bodies; however, the indirect impacts of this on ecosystem functioning are poorly understood. In this thesis I present data from mesocosm and field manipulation experiments used to assess the effect of bioturbation by three widely distributed invasive crayfish species (Procambarus clarkii, Pacifastacus leniusculus and Astacus leptodactylus) on a variety of ecosystem properties across seasons. In the mesocosm experiments, P. clarkii caused significantly more bioturbation than the other species, although increased bioturbation by all species in the spring and/or summer was associated with: reduced dissolved oxygen concentrations in near-surface water, indicating a large increase in oxygen demand by the water column; increased methane oxidation potential within the water (MOPwat), indicating the re-suspension of methane oxidising bacteria (MOB) along with the sediment; and a shift in zooplankton community structure towards dominance by large cladoceran species. Stable isotope analysis of the zooplankton showed a strong relationship between δ13C and MOPwat, suggesting that bioturbation increases MOB consumption. Given the importance of zooplankton as a trophic link to the higher food web, crayfish bioturbation may increase the importance of methane derived (chemosynthetic) carbon in invaded ecosystems. Temperature was identified as the key driver of seasonal variations in crayfish bioturbation intensity through laboratory mesocosm experiments, enabling estimation of the full annual pattern of bioturbation intensity for each species. The optimal temperature for P. clarkii was much higher than for the other species meaning that its bioturbation impacts exhibited large seasonal fluctuations whilst P. leniusculus and A. leptodactylus maintained a lower but more consistent level. Field manipulation experiments of enclosed sections of Chalgrove Brook, Oxfordshire, found significant bioturbation activity by P. leniusculus in early autumn; however, the increase in turbidity was too small to detect other effects observed in the mesocosm experiments.

Thesis (Ph.D.)--Kent State University, 2009. / Title from PDF t.p. (viewed Nov. 16, 2009). Advisor: Mark Kershner. Keywords: crayfish; stream; predation; current velocity; water depth; grain size; resource competition. Includes bibliographical references.

Thesis (Ph. D.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains x, 144 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

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Thesis (Ph. D.)--Georgia State University, 2007. / Title from file title page. Donald H. Edwards, committee chair; Charles D. Derby, Paul S. Katz, Kathryn Betty Grant, committee members. Electronic text (226 p. : ill. (some col.)) : digital, PDF file. Description based on contents viewed Feb. 6, 2008. Includes bibliographical references (p. 208-221).