Recognition of Dominance Status By Chemoreception in the Red Swamp Crayfish, Procambarus clarkii

We tested the hypothesis that chemical signals play a role in the recognition of dominance status in the red swamp crayfish, Procambarus clarkii. Dominance was judged on the outcome of dyadic interactions in all male or female groups of three individuals. This resulted in a dominant, intermediate, and subordinate individual within each population. A choice paradigm in a flow-through Y maze was used to judge whether crayfish were able to recognize dominance through chemical cues alone. Both individuals that interacted with the animal producing the odor and naive individuals were tested. Irrespective of sex and previous experience, individuals increased their rates of locomotion in the presence of conspecific odor. Naive males investigated the dominant arm first, spent more time at the dominant nozzle, and responded more aggressively (as measured by meral spread) to dominant male odor and subordinate female odor. Intermediate males spent more time at the dominant male nozzle and responded more aggressively to dominant male odor. Naive females spent more time at the dominant nozzle. These results show that males recognize dominant animals. Since both naive and experienced males respond to water from dominant animals, we concluded that this is recognition of dominance and not just individual recognition. This signal may be important for the formation or reinforcement of dominance relationships. Based on the change in behavior between odors, we suggest that crayfish can use chemical cues to recognize the dominance status of conspecifics.     

Disturbance and reattachment behavior of sea anemonesCalliactis tricolor (Le Sueur): Temporal,textural and chemical mediation

Two hermit crabs,Dardanus venosus (Milne-Edwards) andPagurus pollicaris Say, have evolved mutualistic symbiotic relationships with sea anemones,Calliactis tricolor (Le Sueur). Anemones live on gastropod shells occupied by the crabs. Both partners are thought to participate in the transfer of the anemone to the crab's shell. However, neither species invariably exhibits transfer behavior when in contact with the other symbiont. Factors influencing transfer activity ofC. tricolor were studied. Anemone attachment is stimulated by disturbance and is time dependent. Anemones attached to shells more frequently immediately after the anemone was disturbed. Assays testing surface texture and surface composition showed that attachment activity of the sea anemone is dependent upon the organic matrix of the shell and is enhanced by texture. Attachment by anemones to shells with organic matrix removed is reduced, but is stimulated by adsorption of complex odor mixtures. Anemones respond to odor mixtures that signal food to crabs and to odor mixtures that stimulate shell investigation and shell switching in crabs. Thus,C. tricolor participates in shell transfer activity after disturbance. Behavior of the anemone is cued by texture and chemicals, including chemical mixtures that cause hermit crabs to change shells.     

Individual Discrimination by Odors in Sibling Prairie Voles (<Emphasis Type="Italic">Microtus ochrogaster</Emphasis>)

The habituation–discrimination paradigm has been used widely to demonstrate that animals can detect individually distinctive odors of unfamiliar conspecifics. By using a modification of the habituation–discrimination technique, Todrank et al. (Anim Behav 55:377–386, 1998) found that golden hamsters discriminate between the individual odors of their own familiar brothers but cannot discriminate between the odors of two siblings that are unrelated and unfamiliar to the subject. This suggested that previous evidence showing that animals could discriminate between the odors of individuals actually may have demonstrated the ability to discriminate between genetically unrelated conspecifics (i.e., members of different families). To test this possibility, we conducted habituation–discrimination experiments with prairie voles, Microtus ochrogaster. Voles were tested under three conditions: subject and both targets were unrelated and unfamiliar; subject and both targets were brothers and familiar; subject was unrelated and unfamiliar to targets, but targets were brothers. In all cases, voles discriminated between the two individual odors. Thus, prairie voles can discriminate individual differences between the odors of brothers and they do not have to have previous experience with the conspecifics in order for discrimination to occur. The theoretical importance of these results is discussed.     

Responses of Cambarid Crayfish to Predator Odor

The responses of individuals of four sympatric species of cambarid crayfish to the introduction of the odor of a common predator, the snapping turtle Chelydra serpentina, were recorded in the laboratory. Adult Orconectes virilis spent significantly more time in a lowered posture and reduced the frequency of nonlocomotory movements following introduction of snapping turtle odor but showed no change in behavior upon introduction of the odor of painted turtle (Chrysemys picta). Recently released young O. virilis did not respond to snapping turtle odor initially but did so after turtle odor and conspecific alarm odor had been paired. Individuals of O. propinquus did not respond to snapping turtle odor. Initial tests with O. rusticus did not yield any response to snapping turtle odor but after experience with paired turtle and alarm odor, individuals showed a decrease in nonlocomotory movements when just snapping turtle odor was introduced. Individuals of Cambarus robustus spent less time in the lowered posture, less time in their burrow, and more frequently executed nonlocomotory movements, in response to snapping turtle odor. The differences in responses to the odor of a common predator are correlated with ecological differences among the crayfish species.     

Specificity of hermit crab attraction to gastropod predation sites

Chemical cues are important to hermit crabs in location of shells. The type of gastropod flesh at a predation site (area where a gastropod is being consumed) influences species of crabs attracted to the site. Additionally, amount of flesh at a site is an important factor influencing relative size of the site attendants. Chemical information broadcast from natural predation sites appears highly specific and may serve to separate shell searching of various sizes and species of hermit crabs in time and space.     

Responses of Mud Snails and Periwinkles to Environmental Odors and Disaccharide Mimics of Fish Odor

Estuarine snails, periwinkles (Littoraria irorata), and mud snails (Ilyanassa obsoleta) were tested for behavioral responses to aqueous extracts of tissue macerates, odors of living intact organisms, and to disaccharides derived from heparin. Extracts included salt-marsh cordgrass (Spartina alterniflora), pink shrimp (Penaeus duorarum), crushed periwinkles, and crushed mud snails. Odors included live periwinkles, mud snails, stone crab (Menippe mercenaria), striped hermit crab (Clibanarius vittatus), tulip snail (Fasciolaria hunteria), and mummichog (Fundulus heteroclitus). Responses were determined upon contact by snails of a ring of solution in the bottom of an otherwise dry bowl and by presenting snails in seawater with 25 l of solution on a cotton swab. In each test, the response of 30 individuals was determined. Behaviors were recorded as fed, alarm, and no response. The strongest alarm response (>80% of all snails tested) in both snails was elicited by crushed mud snails. The strongest feeding response was to shrimp and periwinkle extract for mud snails (>70%), and salt-marsh cordgrass extract attracted periwinkles. High percentages of mud snails and periwinkles fled in response to the odors of intact snail predators, stone crabs, tulip snails, and mummichogs. Mud snails and periwinkles did not flee in response to nonpredator odors, including each other's odor, as well as that of hermit crabs, shrimp, and marsh cordgrass. Heparin disaccharides were tested because other studies reported that biological activity of predatory fish odor is due to similar disaccharides originating from fish mucus. Mud snail responses to disaccharides indicate that they respond to the same kinds of molecules as crustacean larvae and that the modified amine on the disaccharide is essential for activity. The Q-tip assay is appropriate for bioassay-directed purification of alarm signals originating in fish body odor.     

Chemical attraction of hermit crabs and other attendants to simulated gastropod predation sites

Simulated gastropod predation sites were observed in the gulf intertidal near the Edward Ball Marine Laboratory, Sopchoppy, Florida,Fundulus similis, Callinectes sapidus, Melongena corona, Clibanarius vittatus, andPagurus longicarpus were attracted to the sites by small molecules released passively from the flesh of wounded or dead animals. Flesh consumers (F. similis, C. sapidus, andM. corona) were attracted to molecules released from the flesh of bivalves, gastropods, and crabs. Shell users (C. vittatus andP. longicarpus) were attracted only to small molecules from gastropod flesh, withP. longicarpus attendingP. duplicatas sites whileC. vittatus preferentially attendedM. corona, Busycon contrarium, andBusycon spiratum sites. Flesh consumers and shell users may be attracted to the sites by different sets of small molecules. The addition of proteolytic enzymes to the flesh increased the attendants at a site, indicating that the attractant molecules might be amino acids or small peptides. Flesh consumers were attracted to the sites primarily in the first 12 hr while the shell users were attracted from 2 hr to several days postinitiation. New shells were attractive to hermit crabs up to 12 hr after entry by a hermit crab. The shell species of the attendantC. vittatus were in different proportions than the generalC. vittatus population, and the shell fit of theP. longicarpus attendants was not as good as the general population ofP. longicarpus. Significantly moreC. vittatus attended than P. longicarpus, and it was speculated that there were moreC. vittatus in the area with a poor shell fit thanP. longicarpus.     

Intraspecific Chemical Recognition in the Lizard Liolaemus tenuis

Experimental tests were conducted to determine whether females and males of the tree-dwelling lizard Liolaemus tenuis (Tropiduridae) show intraspecific chemical recognition during breeding and postreproductive seasons. Animals were individually maintained in plastic enclosures for one week. Thereafter, the number of tongue-flicks that a lizard performed in the enclosure of a male, a female, its own home enclosure, and a control (unused) enclosure were recorded. In both seasons, males and females made fewer tongue-flicks in their home enclosures than in any other one, indicating a recognition of a familiar place, probably a chemical self-recognition. Conspecific chemical recognition was season dependent. During the post-reproductive season, lizards tongue-flicked at similar rates in conspecific and control enclosures, while during the breeding season enclosures of females elicited more tongue-flicks by both sexes, and the overall tongue-flick rates were higher than in the postreproductive season. Results are discussed within the context of the social system of the species.     

Formation of Colony Odor in Ponerine Ant Pachycondyla apicalis

The mechanisms operating in the formation and maintenance of colony odor in the ponerine ant Pachycondyla apicalis were studied using radioactive tracers. Using [l-¹⁴C]acetate as a precursor, the de novo biosynthesis and distribution of pentane-extractable lipids within the ant's body were followed. Twenty-four hours after injection, newly synthesized alkanes, alkenes, as well as more polar lipids were found in the postpharyngeal gland, the epicuticle, and internally. Ants that had their mouths blocked with beeswax possessed significantly less radiolabeled lipids (all classes measured) in the postpharyngeal gland but had augmented levels in the internal pool and the epicuticle. Both hydrocarbons and more polar lipids were exchanged between the respective postpharyngeal glands and the epicuticle. The transfer to postpharyngeal glands was highest when both ants had an open mouth or when the recipient ant had an open mouth but the donor's mouth was blocked. This suggests that the transfer to the postpharyngeal gland in this species is by allogrooming and not by trophallaxis. Transfer to the cuticle was low and comparable in all treatments. Behavioral observations during the first 6 hr of the dyadic encounters and in intact colonies confirmed that the ants did not engage in trophallaxis. The level of transfer to the postpharyngeal gland in P. apicalis was significantly lower than in representatives of other Formicidae subfamilies studied so far. We attribute this difference to the evolution of trophallaxis in the higher Formicidae.     

Chemicals Used for Host Recognition by the Granary Weevil Parasitoid Lariophagus distinguendus

In order to develop methods for mass rearing of the parasitic wasp Lariophagus distinguendus, we characterized and identified chemicals used by this parasitoid to recognize wheat grains infested by its host, larvae of the granary weevil, Sitophilus granarius, a major pest of stored grain worldwide. Bioassays revealed that drumming and drilling behavior of the parasitoids on grain models of filter paper treated with host feces was as intense as on host-infested grains. Thus, chemicals from feces are highly important to recognize infested grains. Extracts of the feces with hexane or dichloromethane applied on grain models were able to provoke drumming and drilling activity. Hexane extract of feces was as active as infested grain itself. Subsequent fractionation of the hexane extract by adsorption chromatography revealed that highest activity was recovered in the dichloromethane fraction. This fraction was characterized by the presence of -tocopherol, -tocopherol, -tocotrienol, cholesterol, ergostenol, and -sitosterol. Synthetic chemicals in proportions found in the active dichloromethane fraction stimulated drumming behavior in bioassays. The significance of these results with respect to the mass propagation of L. distinguendus as natural enemies for the control of the granary weevil is discussed.     

Comparative study of hermit crab responses to shell-related chemical cues

The responses of Australian hermit crabs to two types of shell-related odor cues were compared. Introduction of gastropod snail odor elicited an increase in grasping of shells in all four species tested (Clibanarius infraspinatus, C. taeniatus, C. virescens, andDiogenes avarus). However, the magnitude of response in the case ofC. virescens was significantly lower than the responses of individuals of the other species. Individuals ofC. infraspinatus responded to introduction of conspecific hemolymph with an increase in both locomotion and the frequency of grasping of shells.C. infraspinatus also responded to the hemolymph of the other three species, and there were no differences in the magnitude of the responses depending upon the source of the hemolymph. When individuals ofC. infraspinatus were exposed to snail odor and conspecific hemolymph at the same time, the responses were indistinguishable from those shown to hemolymph alone.     

Chemical mediation of behavior in hermit crabs: Alarm and aggregation cues

Field studies with three common local species of hermit crabs,Clibanarius vittatus, Pagurus longicarpus, andPagurus pollicaris, showed that these crabs responded behaviorally to chemicals originating from crushed conspecifics. Hermit crabs are attracted specifically and in a manner similar to previously reported crab responses to odors from dead gastropods. Responses byC. vittatus to both kinds of odor are of three types: (1) aggregation/shell investigation responses (previously reported for odors from dead gastropods), characterized by increased locomotor activity, investigation of shells in the vicinity, and switching into empty shells; (2) alarm responses, in which crabs flee the area; and (3) withdrawal responses, in which crabs pull into their shells and do not come out. Studies withC. vittatus showed that the stimulatory chemicals originate from hemolymph, are less than 500 D, adsorb to octadecyl silica, and are recovered by elution with 20% methanol. Responses ofC. vittatus are dependent upon crab size, type of shell occupied, and shell fit. Chemicals originating from dead conspecifics provide a forum for shell acquisition by crabs in relatively small shells and alarm by crabs in relatively large shells.     

Odors as cues for orientation to mothers by weanling Virginia opossums

Three experiments were conducted to investigate whether wholebody and pouch odors facilitate social cohesion between young Virginia opossums and their mothers just prior to weaning. In experiment 1, young oriented toward plastic buckets containing their mothers, directing significantly higher levels of investigative behavior and more distress vocalizations toward them than toward buckets containing unrelated lactating females. In experiment 2, young oriented toward and investigated empty buckets containing whole-body odors of their mothers more than empty buckets containing odors of other females. Similarly, more investigative behavior was directed toward plastic bucket lids containing pouch odors from subjects' mothers than toward pouch odors from unrelated females in experiment 3. These results suggest that social odors help young didelphid marsupials maintain contact with their mothers, as in other mammals, and that whole-body and pouch gland odors are important chemical signals in this nongregarious species.     

Harvester Ants Utilize Cuticular Hydrocarbons in Nestmate Recognition

Cuticular hydrocarbons appear to play a role in ant nestmate recognition, but few studies have tested this hypothesis experimentally with purified hydrocarbon extracts. We exposed captive colonies of the harvester ant Pogonomyrmex barbatus to small glass blocks coated with whole cuticular lipid extracts and the purified hydrocarbon portion of extracts from nestmate and nonnestmate workers. As an estimate of agonistic behavior, we measured the proportion of ants in contact with blocks that flared their mandibles. Blocks coated with cuticular extracts from nonnestmates were contacted by more workers in one of two experiments and elicited higher levels of aggression in both experiments than blocks bearing extracts from nestmates. The cuticular hydrocarbon fraction of extracts alone was sufficient to elicit agonistic behavior toward nonnestmates. The results demonstrate that harvester ants can perceive differences in cuticular hydrocarbon composition, and can use those differences in nestmate recognition.     

Volatile shell-investigation cues of land hermit crabs: Effect of shell fit,detection of cues from other hermit crab species,and cue isolation

Land hermit crab responses to volatile shell-investigation cues from land hermit crabs and from marine hermit crabs are analogous to the responses of marine hermit crabs to shell-investigation cues from marine crabs and from snails. Land hermit crabs attracted to shell cues are in worse-fitting shells and are more likely to investigate conspecifics' shells than are crabs attracted to feeding cues. Moving land hermit crabs from worse shells to better shells decreases the number of crabs investigating shells, while moving crabs from better shells to worse shells increases the number of crabs investigating shells. Gravid females have better-fitting shells than nongravid females or males. Crabs from two different populations in Panama have different shell fits and show different levels of responses to shell-investigation cues. Land hermit crabs respond to volatile shell-investigation cues from both land and marine hermit crabs, but marine hermit crabs do not respond to cues from land hermit crabs. A cue detection system for volatile cues most likely evolved in land hermit crabs during their transition from a marine to a terrestrial existence. Thus, the cues found in land hermit crabs and marine hermit crabs may be chemically similar. Volatile compounds collected from hermit crabs onto Tenax columns can be eluted with ethanol and act as shell-investigation cues in field assays.     

Odor learning and foraging success in the parasitoid,Leptopilina heterotoma

A brief 2-hr experience with hostDrosophila larvae in artificial apple-yeast or mushroom microhabitats had three effects on the foraging behavior of femaleLeptopilina heterotoma (Hymenoptera: Eucoilidae) parasitoids under field conditions. First, experienced females released at the center of circular arrays of apple-yeast and mushroom baits were more likely to find a microhabitat over the course of a daily census than naive ones. Second, for those females that found a microhabitat, experienced ones found it faster than naive ones (i.e., experience reduced travel times). Third, females experienced with a particular microhabitat were more likely to find that micro-habitat than an alternative one. Learned preferences were retained for at least one day and possibly as many as seven. Results generally did not depend on the host species (D. melanogaster orD. simulans) with which females were given experience. Females tended to arrive at baits upwind of the point of release, suggesting that odor is involved in finding host microhabitats and, in particular, in learning to find them more effectively. The implications of these results for the application of semiochemicals in biological control are discussed briefly.     

Odor of the muskox

The behavior of captive male muskoxen was observed closely during their characteristic superiority display, the anatomy of the preputial region was studied in two adults and three calves, and preputial washings and preorbital gland secretion were subjected to gas chromatography and mass spectroscopy. During the superiority display, the prepuce was everted to form a pendulous tube tipped with a fringe of matted hair. Owing to the movement of the animal, the urine that dribbled from the preputial opening was liberally applied to the long guard hairs of the belly. The superiority display was almost exclusively confined to dominant males and apparently accounted for their odor. In the quiescent state, the hair seen around the preputial opening was drawn inside and formed an 8 cm-wide band on the lining of the prepuce. The preputial washings contained large amounts of benzoic acid andp-cresol. The infraorbital gland secretion contained cholesterol, benzaldehyde, and a homologous series of saturated -lactones ranging from 8 to 12 carbons. The latter compounds and the natural secretion smell similar to the human nose.     

Individual variation in the pheromone of the turnip moth,Agrotis segetum

Female turnip moths (Agrotis segetum) from a laboratory culture inbred for more than 30 generations, and the offspring (first and third generation) from field-collected insects were analyzed individually for acetates and alcohols in the pheromone gland. Quantitative analysis of individual components was performed at the subnanogram level by gas chromatographymass spectrometry (selected ion monitoring). The titer of the pheromone, i.e., the sum of the homologous acetates (Z)-5-decenyl acetate, (Z)-7-dodecenyl acetate, and (Z)-9-tetradecenyl acetate was 2.0 ± 0.3 ng in the laboratory culture and 3.2 ± 0.6 ng in the wild strain. There was no correlation between pheromone titer and female weight. The relative proportion of the pheromone components varied substantially between individuals, but there was no statistically significant difference between the two populations. The percentages of the respective compounds (¯X ± coefficient of variation) were 14.8 ± 127% for Z5-10:OAc, 55.6 ± 32% for Z7-12:OAc, and 29.6 ± 59% forZ9-14:OAc. The pheromone composition varied more in the wild strain than in the laboratory culture. The significance of the pheromone variation to the attraction of males was tested in a field experiment. The ratio of males trapped by the most attractive blend versus the least attractive one was 2.2.Schiff., Lepidoptera: Noctuidae.This study was made within the Swedish project Odour Signals for Control of Pest Insects.     

Identification of Floral Volatiles Involved in Recognition of Oilseed Rape Flowers, Brassica napus by Honeybees, Apis mellifera

Volatiles from oilseed rape, Brassica napus, flowers were sampled by air entrainment and their relevance to the natural odor profile of the flowers was confirmed by conditioned proboscis extension (CPE) assays with honeybee, Apis mellifera L., foragers. Coupled gas chromatography (GC)-CPE analysis of the air entrainment samples was used to locate key compounds involved in the recognition of B. napus flowers, and the compounds were then identified using coupled gas chromatography-mass spectrometry and comparison with authentic samples. Six regions of the gas chromatograms elicited CPE responses from bees previously conditioned to the total extract, and from these areas 16 compounds were identified that elicited CPE activity from conditioned bees when tested with synthetic samples. Eight of the 16, -pinene, phenylacetaldehyde, p-cymene, -terpinene, linalool, 2-phenyl-ethanol, (E,E)--farnesene, and 3-carene, gave the highest responses. When the bees were conditioned to the total extract of flower volatiles, a mixture of the eight components elicited responses from 83% of the individuals, suggesting that the eight-component mixture accounted for a major part of the CPE activity of the total extract. In addition, a mixture of the three most active compounds, phenylacetaldehyde, linalool, and (E,E,)--farnesene, evoked responses from 85% of the bees after the latter had been conditioned to the eight-component mixture. Thus, these three compounds appear to play a key role in the recognition of the eight component mixture and, by inference, of oilseed rape flowers.     

Odor Perception in the Bark Beetle Parasitoid Roptrocerus xylophagorum Exposed to Host Associated Volatiles

Y-tube olfactometer bioassays and combined gas chromatography–electroantennographic detector (GC-EAD) analyses were performed to investigate the specific odors utilized as host location cues by the bark beetle parasitoid, Roptrocerus xylophagorum, originating from the southeastern United States. R. xylophagorum parasitizes several economically important holarctic bark beetle species and females oviposit preferentially on late larval stages. Both female and male parasitoids were tested with volatiles derived from host infestations of either Dendroctonus frontalis, the southern pine beetle, or Ips grandicollis, the southern pine engraver. Tested volatiles were steam distillates from the bark of loblolly pine, Pinus taeda, infested with larvae of the respective bark beetle species. Combined gas chromatography–mass spectrometry (GC-MS) was employed for identification and quantification of the compounds in the steam distillates. To confirm the EAD activity of identified compounds, GC-EAD analyses were repeated with a synthetic blend composed predominantly of compounds in the crude extracts that had revealed apparent electrophysiological activity. In Y-olfactometer bioassays, female parasitoids were attracted to both of the above-mentioned distillates. Male parasitoids were tested with one of the distillates but failed to respond. In GC-EAD analyses, the sexes displayed similar relative sensitivities to the components of the blends. Males exhibited generally higher amplitudes of response to the tested compounds than females. Monoterpene hydrocarbons associated with the constitutive resin of the host tree did not elicit significant EAD responses. Compounds known to be associated specifically with the host–tree complex, such as certain oxygenated monoterpenes, generated the greatest EAD responses. Female parasitoids were attracted by a synthetic blend composed of several of the EAD active oxygenated monoterpenes.