Social dominance: a behavioral mechanism for resource allocation in crayfish

Social dominance is often equated with priority of access to resources and higher relative fitness. But the consequences of dominance are not always readily advantageous for an individual and therefore, testing of such assumptions is needed in order to appropriately characterize mechanisms of resource competition in animal systems. This dissertation examined the ecological consequences of dominance in crayfish. Specifically, the following questions were addressed: is resource allocation determined by dominance and how does the structure of resources in an environment affect dominance relationships? By examining the mechanism of how dominance may allocate resources in groups of crayfish, we can begin to answer questions concerning what environmental selective pressures are shaping social behavior in this system. Shelter acquisition and use was examined in a combination of natural, semi-natural, and laboratory studies in order to observe dominance relationships under ecologically relevant conditions. The work presented here shows that: (1) social status has persisting behavioral consequences with regard to shelter use, which are modulated by social context; (2) dominance relationships influence the spatial distribution of crayfish in natural environments such that dominant individuals possess access to more space; (3) resource use strategies differ depending on social history and these strategies may influence larger scale segregation across habitats; and finally, (4) shelter distribution modulates the extent to which social history and shelter ownership influence the formation of subsequent dominance relationships. Taken together, these results demonstrate that dominance has significant consequences for crayfish resource acquisition and holding. However, a complex picture has been revealed as to the nature of dominance establishment and the potential resource benefits associated with dominance. Dominant crayfish posses control over shelter and space but the likelihood of becoming dominant and the subsequent resource use consequences are largely dependent on social and environmental context

Social dominance: a behavioral mechanism for resource allocation in crayfish

Social dominance is often equated with priority of access to resources and higher relative fitness. But the consequences of dominance are not always readily advantageous for an individual and therefore, testing of such assumptions is needed in order to appropriately characterize mechanisms of resource competition in animal systems. This dissertation examined the ecological consequences of dominance in crayfish. Specifically, the following questions were addressed: is resource allocation determined by dominance and how does the structure of resources in an environment affect dominance relationships? By examining the mechanism of how dominance may allocate resources in groups of crayfish, we can begin to answer questions concerning what environmental selective pressures are shaping social behavior in this system. Shelter acquisition and use was examined in a combination of natural, semi-natural, and laboratory studies in order to observe dominance relationships under ecologically relevant conditions. The work presented here shows that: (1) social status has persisting behavioral consequences with regard to shelter use, which are modulated by social context; (2) dominance relationships influence the spatial distribution of crayfish in natural environments such that dominant individuals possess access to more space; (3) resource use strategies differ depending on social history and these strategies may influence larger scale segregation across habitats; and finally, (4) shelter distribution modulates the extent to which social history and shelter ownership influence the formation of subsequent dominance relationships. Taken together, these results demonstrate that dominance has significant consequences for crayfish resource acquisition and holding. However, a complex picture has been revealed as to the nature of dominance establishment and the potential resource benefits associated with dominance. Dominant crayfish posses control over shelter and space but the likelihood of becoming dominant and the subsequent resource use consequences are largely dependent on social and environmental context

Impaired embryonic motility in dusp27 mutants reveals a developmental defect in myofibril structure

An essential step in muscle fiber maturation is the assembly of highly ordered myofibrils that are required for contraction. Much remains unknown about the molecular mechanisms governing the formation of the contractile apparatus. We identified an early embryonic motility mutant in zebrafish caused by integration of a transgene into the pseudophosphatase dual specificity phosphatase 27 (dusp27) gene. dusp27 mutants exhibit near complete paralysis at embryonic and larval stages, producing extremely low levels of spontaneous coiling movements and a greatly diminished touch response. Loss of dusp27 does not prevent somitogenesis but results in severe disorganization of the contractile apparatus in muscle fibers. Sarcomeric structures in mutants are almost entirely absent and only rare triads are observed. These findings are the first to implicate a functional role of dusp27 as a gene required for myofiber maturation and provide an animal model for analyzing the mechanisms governing myofibril assembly