Showing papers on "Uca pugilator published in 1995"

Inhibition of acetylcholinesterase activity in the central nervous system of the red swamp crayfish, Procambarus clarkii, by mercury, cadmium, and lead.

Abstract: The toxicological, physiological and biochemical responses of aquatic crustaceans to heavy metals have been reported by several investigators. Levels of glucose, lactic acid, sodium, potassium, aspartate aminotransferase and alanine aminotransferase in the blood of the crab Scylla serrata increased, while glycogen levels in hepatopancreas and muscle decreased after a four-week exposure to mercuric chloride. In fiddler crab, Uca pugilator, enzyme activity was observed to decrease in the hepatopancreas but increased in abdominal muscle after 48 hr cadmium exposure. In the red swamp crayfish, Procambarus clarkii, exposed for 96 hr to cadmium, glutahione (GSH) level and GSH S-transferase activity deceased in the midgut. In crayfish Astacus astacus exposed to sublethal concentrations of lead and cadmium, oxidative enzyme (succine dehydrogenase and NADPH-cytochrome P450 reductase) activities in gills and hepatopancrease decreased. Acetylcholinesterase (AChE) inhibition by organophosphates and organocarbamates in various crustaceans has bee reported. In vivo cadmium exposure caused increases in esterase activities, but mercury exposure decreases these activities in the hepatopancreas of the shrimp Callianassa tyrrhena. The freshwater crab, Barytelphusa guerini, exposed to 0.6 ppm cadmium showed reduced oxygen consumption throughout the experiment whereas AChE activity increased after 4 days but decreased after 15 days. The authors wanted to determine the effectsmore » of cadmium, lead and mercury on AChE activity in central nervous tissue of Procambarus clarkii. This enzyme has the potential for serving both as a biochemical indicator of toxic stress and a sensitive parameter for testing water for the presence of toxicants. These three biologically silent metals have, according to Schweinsberg and Karsa great toxicological significance to humans because their use is widespread. 14 refs., 4 figs.« less

The visual control of behaviour in fiddler crabs

Abstract: The distribution of resolution around the eye of the fiddler crab Uca pugilator was measured using the pseudopupil, and the results were compared with various behavioural thresholds. As noted previously (Zeil et al. 1986) the eye has a band of greatly increased vertical resolution around the middle with inter-ommatidial angles as small as 1° (Figs. 1–3). In life this band images the horizon. The horizontal resolution is nearly constant throughout the eye. Males notice females when they subtend 2 to 3 inter-ommatidial angles, and distinguish males from females when they subtend 6 to 7 ommatidia (Fig. 6). Potential predators are detected when they subtend only one inter-ommatidial angle, and move through a similar angle. Using models, it was found that males respond to moving objects of the right size as though they were conspecifics, although they do not resemble crabs in shape. It is concluded that only one feature distinguishes other crabs from predators: whether they appear below or above the crab's horizon.

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.

Regulation of sex-specific feeding behavior in fiddler crabs: physiological properties of chemoreceptor neurons in claws and legs of males and females

Abstract: This study examined properties of chemoreceptor neurons in the claws and legs of the fiddler crabs Uca pugilator and U. pugnax. The primary goal was to establish the neural basis of previously observed greater female sensitivity to feeding stimulants, and secondarily to compare physiological properties of chemoreceptor neurons in these semi-terrestrial crustaceans with those of fully aquatic forms. Sensitivity of chemoreceptor neurons in claws and legs is sex-specific; individual neurons of females respond to lower stimulus concentrations than male chemoreceptor neurons, and equivalent concentrations elicit greater spiking in female vs male chemoreceptor neurons. Thus, the population of chemoreceptor neurons in females expresses lower thresholds and greater average sensitivity than in males. Greater sensitivity of claw neurons explains observations indicating that females continue to feed at food levels too low to stimulate males. Sensitivity differences in leg neurons of males vs females have no clear behavioral correlate, but suggest that females can orient to more dilute stimuli than males. Chemoreceptor neurons of fiddler crabs have low sensitivities and slow rates of adaptation compared to other crustaceans. Also, neurons in claws adapt less slowly than neurons in legs, which may reflect subtle differences in the chemical stimulus environment experienced by claws vs legs.