Role of prey odor in food recognition by rock crabs,Cancer irroratus say

Rock crabs,Cancer irroratus, respond to food odors in low concentration as measured by changes in antennular flicking rate. The responses of rock crabs to prey odor were tested in the presence and absence of visual cues to determine the role of chemical cues in prey recognition. Crabs were attracted to the source of mussel odor introduced into one arm of a Y maze. Natural and artificial prey shells and resin boxes were presented to crabs with and without the presence of mussel extract. The crabs were able to see, handle, and manipulate these objects. Crabs opened and consumed contents that emitted chemosensory cues and ignored identical objects that did not. Rock crabs were attracted to food odors and are capable of utilizing chemical cues to detect, locate, and identify food items.     

Chemosensory stimuli for the walking legs of the crayfish Procambarus clarkii

Studies of chemoreception in crustaceans have shown that flesh-eating species can detect amino acids, nucleotides and derivatives, and amines, while most herbivorous and omnivorous species are additionally sensitive to carbohydrates. We used extracellular recording techniques to evaluate the effectiveness of a range of nitrogen-containing compounds (mostly amino acids), bile acids, and carbohydrates in stimulating chemoreceptor cells present in the second and third pereopods of the omnivorous crayfish Procambarus clarkii. When applied at a final concentration of 100 M, effective stimuli were trehalose, leucine, cellobiose, glycine, sucrose, maltose, and ammonium (from most to least effective). The other 17 compounds tested, many chosen because they are potent stimuli for other crustaceans, were ineffective stimuli for P. clarkii. Concentration–response functions were determined for three single cells that were sensitive to ammonium, for five multiunit fibers sensitive to glycine, and for six multiunit fibers sensitive to leucine. Thresholds ranged from 10 nM to 10 M, functions were generally linear when plotted against the log of the stimulus concentration, and there was little evidence of saturation. While P. clarkii is sensitive to only seven of 24 compounds tested, the compounds that proved stimulatory should serve as cues for location and identification of food items preferred by this omnivorous crustacean.     

Orientation of the fiddler crab,Uca cumulanta: responses to chemical and visual cues

Behavioral responses of the fiddler crab Uca cumulanta to flat geometric shapes mimicking natural objects were measured in a circular arena by using zonal recovery as a behavioral measurement. Crabs were tested either in presence or absence of odors from two common predator species, the blue crab Callinectes sapidus, and the pufferfish Sphoeroides testudineus. The study tested the hypothesis that U. cumulanta have different behavioral responses to visual cues in the presence of chemical cues associated with predators. Escape direction tests demonstrated that U. cumulanta is able to show zonal recovery behavior based upon astronomical references. When tested in water lacking predator odor, crabs failed to exhibit a consistent orientation if a single silhouette target was interposed in the landward direction. However, when animals were tested in different predator odor concentrations, an orientation response was obtained at 10 and 20 g/liter/hr blue crab odor and 10 g/liter/hr pufferfish odor, demonstrating U. cumulanta ability to detect the potential presence of its natural predators by this odor. Thus, the hypothesis was supported, and the results suggest that behavioral responses to chemical and visual cues are involved in predator avoidance.     

Determination of the Orientation of Crystallites in PET Fibres

Abstract

A method for the determination of the average angle of orientation of crystallites φ from the azimuthal record of the meridional reflection of the 1 05 diatropic plane for PET fibres is widely used. The 1 05 reflection is the closest to the meridian and the normal to this plane making an angle of approximately 10[ddot] with the c axis. The intensity distribution measured by this method reflects the distribution of the 1 05 plane normals and therefore it comprises: the distribution of the 1 05 plane normals relative to the c crystallographic axis, the distribution of the crystallites relative to the reference fibre axis and the tilted orientation; that is the molecular chain axis inclined by some degrees with respect to the fibre axis. By the studying of the diffraction intensity distribution from the 1 05 diatropic plane this particularly should be taken into account. The sub-meridional (1 05) reflection was scanned in two different geometries: omega and chi scan.

Supercritical CO₂ fluid as an alternative dyeing medium changes the fibre structure to a certain extent in dependence on the treatment temperature and pressure used. Therefore the changes of crystalline orientation in poly(etbylene terephthalate) (PET) fibres as brought about under the influence of supercritical CO₂ fluid were investigated.     

Orientation of boll weevil,Anthonomus grandis boh. (Coleoptera: Curculionidae), to pheromone and volatile host compound in the laboratory

Behavioral responses of male and female boll weevils to the aggregation pheromone, grandlure, and the major volatile of cotton, -bisabolol, were investigated using a new dual-choice olfactometer. Dosage-response experiments revealed both males and females to be attracted by the aggregation pheromone at the 1.0 g dosage. However, only males were attracted to -bisabolol (1.0 g). Both sexes were repelled by the highest dosage of-bisabolol tested (10 g). In preference experiment, males chose grandlure over -bisabolol, while both sexes chose the combination of grandlure + -bisabolol over -bisabolol alone. There was some evidence for synergism between pheromone and plant odor for the females. The results correlate well with previous electrophysiological and behavioral experiments.Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products or vendors that may also be suitable.