Showing papers on "Uca pugilator published in 1990"

Vibrational communication in the fiddler crab, Uca pugilator: I. Signal transmission through the substratum

Abstract: 1. During courtship behavior, males of the fiddler crab, Uca pugilator, drum on the ground with their large chela. The types of waves this produces and some of their properties were investigated using a laser Doppler vibrometer and accelerometers under field and laboratory conditions. 2. Rhythmical impact onto the substratum by Uca produces 3 types of surface waves: Rayleigh waves and Love waves which contain most of the energy, and the weaker surface P-waves. 3. The group velocity of Love-waves is 50–60 m/s in wet sand. Rayleigh waves travel at 70–80 m/s in wet sand and obout 40 m/s in dry sand. The propagation velocity of surface P-waves is 150–160 m/s in compact wet sand and about 140 m/s in wet sand perforated by crab burrows. The group velocity of Rayleigh and Love waves is not influenced by the presence of crab burrows. 4. Fast Fourier transform (FFT) spectra of single beats reveal that the energy maxima of Rayleigh and Love waves lie in the frequency range of 340–370 Hz, i.e., at much higher frequencies than the beat rate of the fiddler crabs, which is usually below 40/s. The optimal frequency is independent of the distance from the signalling male. 5. In the optimal frequency range, the specific damping coefficient α10 for Rayleigh waves is very low and amounts to 0.13–0.16 dB/cm in wet sand and 0.23–0.49 dB/cm in dry sand. Substrate vibrations of higher frequencies are more strongly damped. 6. Considering the size of a fiddler crab, the physical properties of the Rayleigh and Love waves in the optimal frequency range provide a suitable signal for localizing mechanisms which rely on time or phase differences but not on intensity or spectral differences of propagating substrate vibrations.

Flexibility in timing of the metamorphic molt by fiddler crab megalopae Uca pugilator

Abstract: The larvae of many invertebrate taxa can delay metamorphosis for considerable periods of time in the absence of specific stimuli for settlement. This study tested the hypothesis that the duration of the megalopal stage of fiddler crabs can be adjusted by several days depending on the availability of some habitat components. The hypothesis that megalopae can delay the metamorphic molt was tested by comparing the proportion of individuals molting to the first crab instar in aquaria containing only filtered seawater to that in aquaria with mud, sand, and/or an adult crab, near the predicted time of molting. The hypothesis that molting can be advanced was tested by comparing the proportion of sibling larvae molting at intervals throughout the megalopal stage in aquaria containing only filtered seawater or seawater plus an adult crab, mud, and sand. Megalopae delayed molting unless 2 stimuli were present: an adult crab and sediment, either mud or sand. The metamorphic molt was advanced in the presence of both these cues, although contact with the sediment by the adult crab appears necessary for maximal effect. Flexibility in timing of molting and the requirement for more than one cue can increase the chance that megalopae settle and molt to the first crab instar in appropriate adult habitats.

In vitro excystment of the metacercariae of Gynaecotyla adunca and Probolocoryphe uca (Microphallidae) from the fiddler crab, Uca pugilator.

Abstract: A high rate and percentage of excystment of Probolocoryphe uca metacercariae occur at 40 °C in a low salt medium, in the absence of exogenous enzymes, indicating a largely active form of excystment. Exogenous trypsin is required for excystment of Gynaecotyla adunca metacercariae and it is presumed that excystment is largely a passive process. Saturated CO2 conditions promote excystment in this species, whereas high concentrations of pepsin, bile salts (especially deoxycholate), and extreme pH conditions have adverse effects on the process. Physicochemical factors operating in the in vitro excystment of the two microphallids are correlated with conditions presumed to prevail in the avian gut. Excysted metacercariae of both species begin egg production in vitro within several days. Such rapid development may be related to diverse definitive host capacities.

Comparative studies of tidal rhythms. ix. the modifying roles of deuterium oxide and azadirachtin on circalunidian rhythms

Abstract: The influence of deuterium oxide was tested on the persistent activity rhythm of the fiddler crab Uca pugilator. It caused reductions in the amount of activity expressed by 82% of the animals; and increased the period lengths of 73% of the crabs. U. pugnax individuals were subjected to azadirachtin injections. The substance caused the activity peaks of 40% of the crabs to split, produced period shortening in 13%, and period lengthening in 7%. Ten percent of the azadirachtin treated animals became arrhythmic. Ethanol (here used as a solvent for azadirachtin), known to modify circadian rhythms, had no effect on circalunidian rhythms, however, the crabs received only very small, one‐time injections. The results obtained are used as support for a working hypothesis stating that the same clock type may govern both circadian and circalundian rhythms.

Modeling of protease I collagenolytic enzyme from the fiddler crab Uca pugilator.

Abstract: Collagenolytic protease I from the fiddler crab Uca pugilator belongs to the serine proteases of the trypsin family. A graphic molecular model was built using information from sequences and X-ray structures of four homologous proteins which were superimposed to define structurally conserved regions. Protease I sequence was aligned, with sequences of the model proteins, without permitting any deletion or insertion in these regions. Elastase α-carbon chain was selected as a template molecule. For the structurally variable regions, fragments of the four homologous proteins which were ‘closest’ in sequence were selected. Intramolecular steric hindrance, that resulted from the substitution of the residues of the templates by protease I residues, was corrected by adjustment of the side-chain conformational angles. The model was then optimized by energy minimization. The primary specificity pocket in the model of collagenolytic protease I predicts a substrate preference for both P1 hydrophobic and positively charged residues which is in agreement with the biochemical observations. As soybean trypsin inhibitor (STI) is known to inhibit collagenolytic protease I, a tentative model of the complex was constructed and possibilities of interaction examined.