Showing papers on "Uca pugilator published in 1978"

Adaptive Significance of Reproductive Cycles in the Fiddler Crab Uca pugilator: A Hypothesis

Abstract: Semimonthly peaks in courtship behavior of male crabs coincide with peaks in the temporal distribution of receptive females. Females mate once each month, 4 to 5 days before one of the semimonthly spring tides. The relation of the time of reproduction to tide cycles may be an adaptation to increase to a maximum the probability that the final stage of the planktonic larvae will be transported by tidal currents to substrates suitable for adults.

Combat in the Fiddler Crabs Uca Pugilator and U. Pugnax: a Quantitative Analysis

Abstract: The aggressive behavior of two temperate species of fiddler crabs (Uca pugilator and U. pugnax) was studied in the field. Most of the fights wer between Residents (crabs owning burrows) and Wanderers seeking to displace them, though less commonly, fighting occurred between Residents occupying adjacent burrows. Over 400 fights were observed in each species. The two species showed differences in the sequences of acts performed during fights. Uca pugnax also performed two acts never observed in U. pugilator. Wanderers were rarely successful in displacing Residents of the same size or larger, but they won a small percentage of fights when they were larger than the Resident. Uca pugilator Wanderers select Residents that are slightly smaller, but we found no evidence for size selection in U. pugnax. Strongly motivated Wanderers repeatedly performed a key act (Downpush), which was also strongly correlated with successfully displacing Residents. Combat duration and number of acts were not related to temperature, the time of day, or the time in relation to low tide. However, the incidence of fighting increases in the early afternoon. Most of the fights occur within 1-3 hours after low tide. Differences between the species in the tempo and length of fights were observed. An hypothesis, based upon habitat differences and the value of burrows as a resource, is presented to account for these differences. We compared our data to CRANE'S (1967) for U. rapax, a tropical species. There are some important differences between her findings and ours, even though U. pugnax is closely related to U. rapax. We suggest that at least one of her opinions on the significance of aggression in tropical fiddlers is in conflict with evolutionary theory. Some of her other ideas do not apply to temperate species, where climatic factors may be responsible for behavioral convergence. Our data also indicate that the differences and similarities between species are sufficiently provocative to warrant further comparative studies.

Display Specificity and Reproductive Isolation in the Fiddler Crabs, Uca panacea and U. pugilator

Abstract: The factors responsible for reproductive isolation between two sibling species of fiddler crabs (Uca pugilator and U. panacea) were studied under both laboratory and field conditions. ♂♂ showed species differences in their visual and acoustical displays. These differences were exaggerated in the overlap zone, where U. pugilator showed character displacement of its acoustic signals. ♀♀ of U. pugilator confined with ♂♂ of U. panacea produced fewer clutches of young. Occasionally, forced matings took place in the laboratory, resulting in hybrids suffering greater mortality through development. The data indicate that both premating (behavioral) as well as postmating (higher larval mortality) barriers act to prevent interbreeding.

Fiddler Crab Behavioral Ecology: Burrow Density in Uca Pugnax (Smith) and Uca Pugilator (Bosc) (Decapoda Brachyura)

Abstract: Of three species oi fiddler crabs found in the salt marshes on Sapelo Island, Georgia, U.S.A., Teal (1958) has shown that Uca pugnax is the most widespread in distribution, and when paired with U. pugilator causes a reduction in the number of burrows dug. This field study examined burrow density in order to understand why burrow reduction occurs when U. pugnax is the interfering species. Populations of U. pugnax are seven times more dense than populations of U. pugilator, which appear to migrate periodically. In mixed populations of U. pugnax and U. pugilator the number of burrows dug by both species together is less than would be predicted by either alone. These data suggest that U. pugnax has a higher tolerance to crowding, and coupled with its widespread distribution and agonistic behavior, is better adapted to live under conditions unfavorable for other Uca species. U. pugilator exhibits greater behavioral variability which would have survival advantage since this species appears to migrate periodically to different environments once certain density levels are reached.

The influence of constant and cyclic acclimation temperatures on the metabolic rates of panopeus herbstii and uca pugilator

Abstract: The comparative influence of acclimation to constant and cyclic temperatures on the metabolic rates of the mud crab, Panopeus herbstii, and the fiddler crab, Uca pugilator, was observed. Although interspecific differences were observed, cyclic acclimation temperatures significantly depressed oxygen consumption in the 15°- 25° C temperature range in both species when compared to rates of animals subjected to constant acclimation rates. Since this depression of metabolic rates occurs over that portion of the yearly temperature range within which the animals are most active, it is suggested that these organisms utilize energy more efficiently when subjected to natural cyclic temperature conditions than when subjected to constant temperature environments. This difference in metabolic data would be significant in analyzing the role of the yearly energy budgets of crabs in ecosystem energetics.

Colchicine and cytochalasin b: a further characterization of their actions on crustacean chromatophores using the ionophore a23187 and thiol reagents

Abstract: 1. Using the prawn, Palaemonetes pugio, and the fiddler crab, Uca pugilator, the modes of action of cytochalasin B and colchicine in inhibiting pigment granule movement were further characterized.2. Colchicine was unable to inhibit, in ovarian erythrophores of Palaemonetes pugio, pigment concentration caused by the ionophore A23187. It did, however, inhibit somewhat the pigment dispersion that normally occurs upon placing A23187-treated erythrophores in Ca++-free, EGTA-containing saline.3. Inhibition by colchicine of pigment concentration in melanophores of Uca pugilator was not prevented by high concentrations of glutathione or cysteine hydrochloride. Pigment concentration was inhibited by mersalyl acid, and this was prevented by glutathione.4. Cytochalasin B inhibited ionophore A23187-induced pigment concentration in ovarian erythrophores of Palaemonetes pugio.5. Electron microscopy revealed a filamentous matrix interconnecting the pigment granules of Uca pugilator.6. Speculation is presented as to the ...

Interactions of Methylmercury, Cadmium, and Salinity on Regeneration in the Fiddler Crabs Uca pugilator, U. pugnax and U. minax

Abstract: After multiple autotomy in the fiddler crabs Uca pugilator, U. pugnax and U. minax, both methylmercury and cadmium retard limb regeneration and ecdysis. When crabs in sea water are exposed to a mixture of both metals, the effect is increased, indicating that the two are interacting in an additive way. In 50% sea water (=15% S), the effects of cadmium are greatly intensified so that growth of limb buds is extremely slow, if it occurs at all. When methylmercury is present in the water at the same time, the severe effects of cadmium are somewhat ameliorated, indicating an antogonistic interaction of the two metals under these conditions. Adding additional calcium to the 50% sea water also decreased the severity of the cadmium effect, thus supporting the idea of a calcium-cadmium competition.

Effects of ecdysterone, inokosterone and eyestalk ablation on limb regeneration in the fiddler crab, Uca pugilator

Abstract: Bilateral ablation of eyestalks or injection of either ecdysterone or inokosterone (two 25-μg doses or five 10-μg doses into crabs weighing on an average 1.5 g) caused precocious proecdysis and ecdysis in the fiddler crab, Uca pugilator. On a weight basis ecdysterone was more effective than inokosterone in exerting the effects. Whether the accelerated proecdysis was accompanied by regenerative limb growth depended on the degree of limb bud development at the time of treatment with ecdysones. Ecdysterone and inokosterone blocked the initiation of basal limb growth when administered as two 25-μg doses into crabs exhibiting scar tissue without any visible limb bud. When injected into crabs with limb buds in various stages of basal limb growth exogenous ecdysones accelerated basal limb growth and led to proecdysial limb growth. The degree of acceleration of limb bud growth noticed within three to six days after injection of ecdysones into crabs with limb buds in early stages of basal limb growth was greater than that resulting from eyestalk ablation. In crabs with limb buds in later stages of basal growth, the degree of acceleration of limb bud growth evoked by exogenous ecdysones was similar to that resulting from eyestalk ablation. The final sizes of the limb buds preceding ecdysis in eyestalkless crabs and crabs injected with ecdysones depended on the proecdysial duration available for regeneration. The rate of proecdysial limb growth has been known to vary with the speed at which the crabs complete the proecdysial stages of the molt cycle. This study shows that the time required for the initiation and completion of the basal limb growth also varies depending on how soon the intact and eyestalkless crabs approach proecdysis and ecdysis.

Underwater orientation in the sand fiddler crab, uca pugilator

Abstract: The semi-terrestrial sand fiddler crab, Uca pugilator, occasionally is forced by avian and mammalian predators to go into the water where it becomes vulnerable to aquatic predators. Therefore, it would be adaptive for Uca to possess some means of detecting the direction of the shore and its burrow while submerged. Using crabs from Florida and Long Island, New York, the identity of the cues used in underwater orientation and the possible hierarchial arrangement of these cues were ascertained.Under various cue regimes, the crabs were individually observed in a long narrow tank that allowed the crabs to proceed either toward shore or away from it. The potential cues for shoreward orientation which were available to the submerged crab were celestial cues, landmarks, and gradient cues (hydrostatic pressure, light wavelength, light intensity and substrate slope). Each cue was isolated and then tested for its effectiveness in orientation. It was next presented to the crabs in a conflicting configuration with oth...

Influence of the polychlorinated biphenyl preparation Aroclor 1242® on color changes of the fiddler crab Uca pugilator

Abstract: The melanin in the melanophores of specimens of the fiddler crab, Uca pugilator, exposed to 2, 4, and 8 ppm solutions of the polychlorinated biphenyl (PCB) preparation, Aroclor 1242®, became less dispersed than in untreated specimens This effect was dose-dependent It was probably due to the PCB itself and not to polychlorinated dibenzofurans which are contaminants of commercial PCBs The decreased melanin dispersion appeared to be related to a decrease in the rate of release of melanin-dispersing hormone from eyestalk neuroendocrine cells into the hemolymph Eyestalks of crabs kept for 4 days in Aroclor 1242 contained 4 times as much melanin-dispersing hormone as did control crabs When injected into isolated legs, did hemolymph from control crabs Aroclor 1242 did not appear to have a direct effect on the pigment-dispersing mechanism of the melanophores

Metabolic response to thermal changes of the adult fiddler crab Uca pugilator and the effect of PCBs

Abstract: Although polychlorinated biphenyls (PCBs) are widespread in the environment, their influence on functional characteristics of marine animals is poorly known. This paper presents data on the relative effects of a sublethal concentration (50 ppb) of Aroclors® 1016 and 1254 on the respiratory metabolism of the fiddler crab Uca pugilator (Bosc.), an intertidal, estuarine inhabitant. At 25°C, the respiration rate of both males and females increased initially after exposure to these Aroclors. After the crabs were returned to uncontaminated seawater, their respiratory rates were similar to initial pre-exposure values. At 15°C, Aroclors 1016 and 1254 had no apparent effect on the respiration of males but depressed that of females. Upon exposure to PCB-free seawater, the metabolic rate of both male and female crabs was similar to initial pre-exposure rates. At 35°C, a trend existed for both of these PCBs to inhibit respiration. In a series of experiments on cold- and warm-acclimated individuals, PCBs did not consistently influence metabolic response over the thermal range of 10° to 30°C.

Under\vater orientation in the sand fiddler crab,

Abstract: The sand fiddler crab (Uca pugilator) inhabits the intertidal and supratidal zones of sheltered sandy coastlines from Cape Cod to Texas (Crane, 1943). As with other ocypodids, its semi-terrestrial designation stems from its physiological dependence upon periodic submersion and from its behavioral activity on aeriallyexposed substrates. Burrows dug in the sand serve as shelter during predatory attacks and high tides, as immediate sources of water, and as focal points of social activity. Occasionally, a crab is forced to seek refuge in the water when access to the burrows is blocked by pursuing predators such as plovers, willets, raccoons, clapper rails, etc. (Herrnkind, 1972; Teal, 1958; and personal observation). It then becomes vulnerable to attack by such aquatic predators as fish and the portunid crabs, Callinectes sapidus and Carcinus maenas. Hence, it would be of selective advantage for Uca pugilator to possess some means of detecting the direction of the shore and a suitable burrow while submerged. Indeed, field releases of free-ranging U. pugilator in shallow offshore waters result in marked orientational movements toward shore (L. M. Lutton and D. Y. Young, unpublished data; W. F. Hernkind, unpublished data). Terrestrial orientation in the genus Uca has been investigated only in recent years (Altevogt, 1965; Altevogt and von Hagen, 1964; Herrnkind, 1966, 1967, 1968, 1972). A thorough review of orientation in shore-inhabiting arthropods, with specific reference to Uca pugilator, is given by Herrnkind (1972). On aerially exposed beaches U. pugilator utilizes a time-compensated sun compass, supplemented by telotactic responses to landmarks for directed movements of distances greater than one meter ("far orientation"). Kinesthesia of substrate features is not known to influence orientation over these distances. Instead, kinesthetic cues are said to be limited to above water movements of less than one meter ("near orientation") (Herrnkind, 1972). Orientation cues available to the crab underwater potentially differ from those on land due to differences in the physical characteristics (e.g., refractive index, specific gravity, transparency, etc.) between sea water and air. Visual cues, such as those emanating from celestial and landmark sources, may be available to submerged crabs as well as to those situated on the exposed portions of the beach. Celestial cues involve the sun's position and/or polarized light. Landmarks could be detected as differential light intensities created by beach grasses, trees, and mangroves set against a sky or sand background. In both cases, the apparent