Showing papers on "Uca pugilator published in 2014"

Sexual selection and the physiological consequences of habitat choice by a fiddler crab

Abstract: In mid-Atlantic salt marshes, reproductively active male sand fiddler crabs, Uca pugilator, use a single greatly enlarged major claw as both a weapon to defend specialized breeding burrows from other males and an ornament to attract females for mating. During the summer breeding season, females strongly prefer to mate with males controlling burrows in open areas high on the shore. Food availability decreases while temperature and desiccation stress increase with increasing shore height, suggesting that the timing and location of fiddler crab mating activity may result in a potential trade-off between reproductive success and physiological condition for male crabs. We compared thermal preferences in laboratory choice experiments to body temperatures of models and living crabs in the field and found that from the perspective of a fiddler crab, the thermal environment of the mating area is quite harsh relative to other marsh microhabitats. High temperatures significantly constrained fiddler crab activity on the marsh surface, a disadvantage heightened by strongly reduced food availability in the breeding area. Nevertheless, when the chance of successfully acquiring a mate was high, males accepted a higher body temperature (and concomitantly higher metabolic and water loss rates) than when the chances of mating were low. Likewise, experimentally lowering costs by adding food and reducing thermal stress in situ increased fiddler crab waving display levels significantly. Our data suggest that fiddler crabs can mitigate potential life history trade-offs by tuning their behavior in response to the magnitude of both energetic and non-energetic costs and benefits.

Locomotor hindrance of carrying an enlarged sexually selected structure on inclines for male fiddler crabs

Abstract: Sexual selection often results in males exhibiting exaggerated traits (e.g. bright colors, elaborate appendages) to attract potential mates and in some cases to also use as a weapon. These traits, however, can impose costs, such as an increase in energy expenditure and a decrease in locomotor performance, which could decrease foraging efficiency and increase an individual's vulnerability to predators. We examined the effect of the enlarged claw in male fiddler crabs Uca pugilator on ecologically relevant performance measures. We measured locomotor performance and kinematics during horizontal, uphill and downhill movements. Speed and stride mechanics were measured for clawed males, males after the claw was removed, and females while running on level (0°), uphill (15 and 30°) and downhill (−15 and −30°) slopes. Endurance capacities were measured on all crabs on horizontal and uphill inclines. Though claw removal had no significant effect on horizontal speeds, removal of the major claw significantly increased uphill speeds of male fiddler crabs at 15 and 30° inclines. Generally, as incline increased, the difference in performance between males with the enlarged claw and those with the claw removed increased. We also found that clawed males exhibit slower downhill speeds compared to clawless males and that claw removal significantly enhanced endurance on all inclines. This study indicates that an assessment of movement on level surfaces alone may not be entirely ecologically relevant when determining the actual costs of sexually selected ornaments.

Independent and interactive effects of two facilitators on their habitat-providing host plant, Spartina alterniflora

Abstract: The role of habitat-providing species in facilitating associated species abundance and diversity is recognized as a key structuring force in many ecosystems. Reciprocal facilitation by associates, often involving multiple species, can be important for the maintenance of the host species. As with other multi-species interactions (e.g. multiple predator effects), non-additive relationships may be common among these associates, yet relatively few studies have examined potential interactions among multiple facilitator species. We combined field surveys and a mesocosm experiment to examine the independent and interactive effects of two co-occurring facilitator species, ribbed mussels Geukensia demissa and fiddler crabs Uca pugilator, on their host salt marsh plant species, cordgrass Spartina alterniflora. We also experimentally examined how these relationships varied across different host plant genotypes. Overall, facilitator effects increased with increasing facilitator density. There was a significant interaction between mussel and fiddler crab presence, indicating that the effects of each species on cordgrass were dependent on the presence of the other facilitator species. In addition, there were strong interactions among mussels, fiddler crabs, and plant genotype, with greater variation in the performance of individual genotypes when fiddler crabs were absent. Our work reinforces the importance of considering multiple responses when assessing the functional redundancy of co-occurring facilitators, as species are seldom completely redundant across the range of services they provide. It also highlights that the strength and direction of species interactions can vary due to genetic variation within the interacting species.

Hemigrapsus sanguineus in Long Island salt marshes: experimental evaluation of the interactions between an invasive crab and resident ecosystem engineers

Abstract: The invasive Asian shore crab, Hemigrapsus sanguineus, has recently been observed occupying salt marshes, a novel environment for this crab species. As it invades this new habitat, it is likely to interact with a number of important salt marsh species. To understand the potential effects of H. sanguineus on this ecosystem, interactions between this invasive crab and important salt marsh ecosystem engineers were examined. Laboratory experiments demonstrated competition for burrows between H. sanguineus and the native fiddler crab, Uca pugilator. Results indicate that H. sanguineus is able to displace an established fiddler crab from its burrow. Feeding experiments revealed that the presence of H. sanguineus has a significantly negative impact on the number as well as the biomass of ribbed mussels (Geukensia demissa) consumed by the green crab, Carcinus maenas, although this only occurred at high predator densities. In addition, when both crabs foraged together, there was a significant shift in the size of mussels consumed. These interactions suggests that H. sanguineus may have long-term impacts and wide-ranging negative effects on the saltmarsh ecosystem.

Molecular characteristic and expression analysis of collagenolytic serine protease from the Chinese mitten crab Eriocheir sinensis with defense response to Vibrio anguillarum challenge

Abstract: A novel collagenolytic serine protease (CLSP) was cloned from the hemocytes of the Chinese mitten crab Eriocheir sinensis (Es-CLSP). The full-length cDNA of Es-CLSP contains 990 nucleotides. It encodes a 270-amino acid-long peptide with the mature peptide containing 221 amino acids. It contains the conserved catalytic triad (H, D, and S). Similarity analysis shows that Es-CLSP shares high identity with CLSPs from the fiddler crab Uca pugilator. Es-CLSP mRNA expression in E. sinensis is a) tissue-related with the highest expression in hemocytes and widely distributed, b) highly responsive to Vibrio anguillarum challenge in hemocytes, and c) a different response to the intruding pathogens. The results of this study demonstrate the successful isolation of Es-CLSP and indicate that Es-CLSP is an immune-related gene, and show the possible role of CLSP in the invertebrate innate immune system.

Density, Shell Use and Species Composition of Juvenile Fiddler Crabs (Uca spp.) at Low and High Anthropogenic Impact Salt Marsh Sites

Abstract: Coastal wetlands worldwide have been negatively impacted by humans, causing decreases in the vegetation used as a refuge from predation by juveniles of many species. This study examined juvenile fiddler crab densities and species composition (Uca pugnax, Uca pugilator, and Uca minax), and their use of gastropod shells (Littorina littoraria), at three low and three high impact sites on barrier islands in southeast Georgia. On six dates in June–August 2010, samples were taken from 10 quadrats (1 m2) at each site to determine juvenile fiddler crab densities and species composition, as well as gastropod shell densities and percent shell use. Multiplex PCR was used to identify juvenile fiddler crabs to species. Juvenile fiddler crab densities were lower at high impact sites, while gastropod shell densities and shell use were similar at both low and high impact sites. Species compositions differed between low and high impact sites on the substrate and in shells, with more U. pugilator and U. minax at high impact sites. A change in fiddler crab densities and species composition could cause a substantial change in southeastern salt marshes.