Uca pugilator

About: Uca pugilator is a research topic. Over the lifetime, 376 publications have been published within this topic receiving 12303 citations.

Effects of all-trans retinoic acid on regenerating limbs of the fiddler crab, Uca pugilator

Abstract: Regeneration of walking legs in the fiddler crab Uca pugilator represents true epimorphic growth since it involves organization of an undifferentiated blastema prior to regrowth of a new limb. Normal regeneration in Uca consists of two major stages—basal growth and proecdysial growth. One of the earliest events in the basal growth stage of regeneration is the secretion of cuticle by epidermal cells that migrate under the scab at the site of limb loss. When crabs are maintained in a 0.05 mM emulsion of retinoic acid (RA) in sea water during the first 2 weeks following autotomy, the pattern of cuticle secretion is disrupted in many limb buds. Limb buds on RA-treated crabs grow more slowly and are frequently malformed. © 1995 Wiley-Liss, Inc.

Control of Egg-Hatching Time in Crabs from Different Tidal Heights

Abstract: Control of egg-hatching time was investigated in the crabs Neopanope sayi, Uca pugilator, and Sesarma cinereum, which occupy a gradient in adult habitats from sublittoral to supralittoral zones, respectively. Hatching time was monitored in the laboratory for eggs attached to females and for eggs removed several hours prior to eclosion. Embryos of all species hatched into larvae swimming independently of the female; however, those of U. pugilator and S. cinereum hatched several hours later and with lower viability than attached eggs. Mean hatching times of attached and detached eggs were correlated for N. sayi, but not for U. pugilator or S. cinereum. These results strongly imply that the embryos are the principal controllers of hatching time in N. sayi but not in U. pugilator or S. cinereum. For all species, removed eggs hatched over a longer time interval than attached eggs, indicating that the female is responsible for the synchrony of release. Increases in the readiness of attached eggs to hatch prior to actual time of larval release were relatively moderate in N. sayi, but more rapid and dramatic for U. pugilator and S. cinereum. These changes are likely the result of enzymatic degradation of the egg membranes. We postulate that, for N. sayi, enzyme release is controlled by rhythms in the embryos, but, for U. pugilator and S. cinereum, females signal the embryos to release enzymes, resulting in rapid degradation of the membranes. Selection for control of larval release time by the female may be especially important in terrestrial and semiterrestrial crabs. Brachyurans carry their fertilized eggs attached to abdominal appendages for various lengths of time depending upon species and environmental conditions. Release of larvae by many crabs occurs rhythmically with respect to exogenous cycles such as phase of the moon, tide, and time of day (for reviews see DeCoursey, 1983; Forward, 1987). For warm temperate and tropical brachyurans, egg hatching is a short duration event, with all eggs present on a female usually hatching within 15-30 min (DeCoursey, 1979; Forward et al., 1982). Exceptions occur especially among the Xanthidae which occasionally release a group of larvae each night for two or three consecutive nights (Forward et al., 1982; Christy, 1986; De Vries and Forward, 1989). Synchronous hatching of an egg mass is the result of synchronous development of the embryos and factors which control the precise time of hatching. Synchronous development of the embryos within a mass is due to an unexplored interaction between the female and the embryos (Forward and Lohmann, 1983; De Vries, unpublished data). Previous work on control of the precise time of hatching in lobsters produced a confusing picture. For Homarus gammarus, Pandian (1970) and Ennis (1973) asserted that the controlling mechanism is in the embryos, while Branford (1978) contended that it is in the female. To date, control of hatching time in decapods has been well-studied only in the subtidal xanthid crab Rhithropanopeus harrisii (see Forward and Lohmann, 1983). Forward and Lohmann (1983) concluded that the clock that sets the precise time of hatching in this species is located in the embryos. In their model, a chemical cue is released upon the hatching of several eggs. This substance induces abdominal pumping by the female, which then causes the remaining larvae to be liberated. Presumably, changes in the integrity of the egg membranes occur sometime prior to egg hatching, since abdominal pumping at other times does not result in hatching (Forward and Lohmann, 1983). These changes may be attributable to eggmembrane degradation by proteolytic enzymes secreted by the crab embryos near the time of egg hatching (De Vries and Forward, in preparation). For terrestrial and semiterrestrial crabs, water into which larvae must be released may not be immediately accessible. It would, therefore, seem maladaptive for embryos to determine the time of egg hatching, since they cannot directly assess proximity of, or

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.

Mechanisms of crustacean egg hatching: Evidence for enzyme release by crab embryos

Abstract: During the summer of 1989, we examined mechanisms of egg hatching in three species of brachyurans that occupy different habitats as adults near Beaufort, North Carolina, USA:Neopanope sayi (Smith) (subtidal),Uca pugilator (Bosc) (intertidal) andSesarma cinereum (Bosc) (supratidal). Results of casein assays indicated that embryos of all species release proteolytic enzymes near the time of egg hatching. Species differences in specific enzyme activity were suggested, with increased activity in the more terrestrial crabs. Embryos ofN. sayi released enzymes several hours before larval release by the female, whileU. pugilator andS. cinereum released enzymes closer to the time of larval release; enzyme release coincided roughly with time of egg-membrane breakage in all species. Direct observations of hatching showed a sequence of outer-membrane breakage apparently followed by inner-membrane breakage and emergence of the larva. Egg volumes increased most during early and/or mid-stages of development, with a marked slowing of the increase during the several days before hatching. Thus, a gradual osmotically-driven increase in water content may also be involved in egg hatching.

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.