Showing papers on "Uca pugilator published in 1972"

Effect of mercury on survival, metabolism and behaviour of larval Uca pugilator (Brachyura)

Abstract: A battery of tests was used to determine the effects of three dilute mercuric chloride solutions on larval stages (Zoea I, III, V) of the fiddler crab Uca pugilator (Bosc). The influence of both acute and chronic exposures on viability, oxygen consumption, and swimming activity was measured. No stage V and only a few stage I or III larvae were able to survive a concentration of 9 * 10-7 M HgCl2 (0.18 ppm Hg) longer than 24 hr; an exposure as short as 6 hr resulted in reduced metabolism and swimming rate of all stages. Although concentrations of 9 * 10-9 M HgCl2 (0.0018 ppm) and 9 10-11 M HgCl2 (0.000018 ppm) were sublethal, 24-hr exposures did affect metabolism and swimming. Some larvae reared in the more dilute mercury solutions developed to the megalopa stage, but survival was reduced in relation to the mercury concentration. The data from all tests suggest that toxicity of mercury increases with larval age.

The synergistic effects of temperature, salinity, and mercury on survival and metabolism of the adult fiddler crab, uca pugilator'

Abstract: Gill tissues of fiddler crab, Ucapugilator, were the major site of mercury concentration; lesser amounts accumulated in the hepatopancreas and green gland. Very small amounts were found in the carapace and muscle tissue. No significant differences in the amount of mercury in tissues of males and females were found. A concentration of mercury sublethal to fiddler crabs under optimum conditions of temperature and salinity greatly reduced survival times when crabs were placed under conditions of temperature and salinity stress. Males were more susceptible to the synergistic effects of mercury in combination with environmental stress than were females. Metabolic rates of male and female fiddler crabs were affected by prolonged exposure to mercury both under optimum environmental conditions and under temperature and salinity stress. Metabolic rates of males were more adversely affected than those of females. Estuaries are an extremely important part of ~he marine environment. Yet often an estuary ~comes so grossly polluted that much of the bIota is destroyed before it is recognized that the quatlity of water affects the biology of such an area. Part of the problem is the subtleness of ~he effects of sublethal concentrations of man­ Introduced pollutants. In low concentration the P?llutant may have no observable effect on a gWen population of animals if environmental Conditions remain at an optimum. However, when another environmental parameter becomes stressful, it may synergistically interact with the sUblethal concentration of pollutant and the or­ g.anism dies. Many estuaries are polluted, and ~Ince one of the chief characteristics of estuaries Is the rather extreme environmental fluctuations that occur throughout the year, knowledge of ~Ynergistic interaction on estuarine animals is ImPortant in the preservation of estuarine eco­ sYstems.

Temperature–Salinity Stress and Mercury Uptake in the Fiddler Crab, Uca pugilator

Abstract: Uptake of 203Hg was determined in gill and hepatopancreas tissue from fiddler crabs (Uca pugilator) maintained under six temperature–salinity regimes. Although the total mercury was relatively cons...

Comparison of the abilities of α-ecdysone and 20-hydroxyecdysone to induce precocious proecdysis and ecdysis in the fiddler crab, Uca pugilator

Abstract: 1 The effects of single, double or multiple injections of α-ecdysone and 20-hydroxyecdysone on molting and limb regeneration in the fiddler crab, Uca pugilator, were determined 2 A single injection of 12 μg of 20-hydroxyecdysone failed to initiate proecdysis in crabs weighing 12 to 16 g Administration of 12, 5, and 5 μg of 20-hydroxyecdysone on Days 0, 3, and 6 respectively induced precocious initiation of proecdysis but not precocious ecdysis However, when two large dosages (20 or 25 μg) of 20-hydroxyecdysone were injected within a period of one or two days all the crabs completed proecdysis and initiated ecdysis precociously but failed to complete the ecdysis and died 3 Administration of 25 μg of α-ecdysone as a single injection failed to initiate precocious proecdysis However, when two injections of 25 μg each were given 36% of the crabs completed proecdysis and successfully molted precociously Injection of larger dosages (80 μg α-ecdysone either as four 20 μg injections or two 40 μg injections) induced precocious proecdysis and ecdysis in 75–86% of the crabs In contrast to the crabs which died during ecdysis after receiving high dosages of 20-hydroxyecdysone, the recipients of α-ecdysone underwent successful ecdysis and their postecdysial survival was normal 4 The response of the regenerating limb buds depended on the dosage of the ecdysones administered Dosages of 20-hydroxyecdysone which failed to initiate proecdysis promoted basal limb growth Stronger dosages of 20-hydroxyecdysone and α-ecdysone which induced precocious proecdysis and ecdysis accelerated limb growth and caused proecdysial limb growth The slope of the growth curve obtained for the crabs injected with high dosages of ecdysones was much steeper than that for eyestalkless crabs 5 The interrelationship between regenerative limb growth and proecdysis and the possible role of ecdysones in the control of proecdysial events in crustaceans are discussed

Capture-recapture methods with uca

Abstract: 1. Estimates of the size of a population of sand fiddler crabs, Uca pugilator (Bosc), were made with the Lincoln Index and Jackson's "positive" and "negative" models in the mobile phase of the activity cycle, and by stratified sampling of the immobile phase.2. Restricted random sampling was employed because of extremely contagious distribution of the crabs during the mobile phase and of desire to achieve better coverage of the burrowing area than unrestricted random sampling might have yielded during the immobile phase.3. During the mobile phase, the overall population was divided into four mobs, one separated from the rest by a physical, and the others from each other by a behavioral barrier. Only three out of 8967 marked individuals were recaptured outside their home territories. Some evidence suggesting that the mobs are derived from subpopulations occupying circumscribable burrowing areas was obtained.4. Appropriateness of the Lincoln Index was supported by immediate random dispersal of marked crabs a...