Aspects of the thermal ecology of the rusty crayfish Orconectes rusticus (Girard)

Summary Orconectes rusticus currently is undergoing an explosive range expansion in the midwestern U.S.A., but information on the potentially important effects of water temperature on the species' biology is lacking. The thermal ecology of O. rusticus in southwestern Ohio, U.S.A., was examined by determining 1) the effects of four water temperatures (16, 20, 25, and 29°C) on survival and growth of juveniles, 2) the responses of juveniles and adults to a thermal gradient (7–27° C), and 3) the thermal tolerances (critical thermal maximum, CTMax, and critical thermal minimum, CTMin) of free-living, field-acclimatized juveniles and adults on a biweekly basis throughout the summer. Month-long growth experiments predicted maximum growth rates of juveniles at water temperatures between 26 and 28°C, but greatest survival between 20 and 22° C. Laboratory-acclimated (22° C) adults and field-acclimatized (2.5° C) juveniles both had an acute preferred temperature of 22° C. CTMaxs and CTMins of juveniles were 0.5–2.6° C higher than those of adults throughout the summer, suggesting that juveniles were exposed to water temperatures 1.5–6.8° C warmer than those of adults. Juvenile and adult O. rusticus prefer habitats where water temperatures favor maximum survival, but they usually are not found together in the same habitat; adults apparently displace the juveniles into warmer habitats. Warmer temperatures can decrease survival of juveniles but improve their growth rates, leading to enhanced fecundity and competitive ability. The past and future success of O. rusticus in expanding its range may depend, in part, on the species ability to adjust to new thermal environments occupied by other species of crayfish.     

Preemptive legislation inhibits the anthropogenic spread of an aquatic invasive species, the rusty crayfish (Orconectes rusticus)

The enactment of legal policies is often recommended to prevent anthropogenic introductions of invasive species. In this paper, we evaluated the effectiveness of proactive state legislative policies in deterring colonization by rusty crayfish (Orconectes rusticus) and the expected spread into previously uninvaded states using network-based spatial analysis. We found that the presence of regulations was positively associated with the presence of rusty crayfish (p = 0.027), but often regulations were put into effect subsequent to the invasion. Regulations that did not explicitly prohibit transport, applied to specific drainages, or prohibited only rusty crayfish were not effective. However, preemptive legislation was effective in reducing the likelihood of invasion, if regulations prohibited the transport of all live crayfish species between water bodies, as only 1 state which passed such legislation prior to invasion by rusty crayfish was subsequently colonized (S = 12, p = 0.031). Five states are likely to be invaded by rusty crayfish via range expansion across interstate drainages, and dispersal rates suggest that all of these states could be colonized within 10 years. While it is unlikely that regulations will prevent dispersal-based invasion across state lines through shared drainages, preemptive legislation can significantly reduce anthropogenic spread of aquatic invasive species between drainages and effectively retard the expansion of rusty crayfish. Our results suggest that the most effective form of legislation is one that does not require individuals to identify species, thus we recommend states enact policies that explicitly prohibit the transport of all live crayfish between water bodies.     

Chronic alterations in serotonin function: dynamic neurochemical properties in agonistic behavior of the crayfish, Orconectes rusticus

The biogenic amine serotonin [5-hydroxytryptamine (5-HT)] has received considerable attention for its role in behavioral phenomena throughout a broad range of invertebrate and vertebrate taxa. Acute 5-HT infusion decreases the likelihood of crayfish to retreat from dominant opponents. The present study reports the biochemical and behavioral effects resulting from chronic treatment with 5-HT-modifying compounds delivered for up to 5 weeks via silastic tube implants. High performance liquid chromatography with electrochemical detection (HPLC-ED) confirmed that 5,7-dihydroxytryptamine (5,7-DHT) effectively reduced 5-HT in all central nervous system (CNS) areas, except brain, while a concurrent accumulation of the compound was observed in all tissues analyzed. Unexpectedly, two different rates of chronic 5-HT treatment did not increase levels of the amine in the CNS. Behaviorally, 5,7-DHT treated crayfish exhibited no significant differences in measures of aggression. Although treatment with 5-HT did not elevate 5-HT content in the CNS, infusion at a slow rate caused animals to escalate more quickly while 5-HT treatment at a faster rate resulted in slower escalation. 5,7-DHT is commonly used in behavioral pharmacology and the present findings suggest its biochemical properties should be more thoroughly examined. Moreover, the apparent presence of powerful compensatory mechanisms indicates our need to adopt an increasingly dynamic view of the serotonergic bases of behavior like crayfish aggression.     

Invasion of an occupied niche by the crayfish Orconectes rusticus: potential importance of growth and mortality

We are exploring mechanisms of an invasion that contradicts the oft-cited generalization that species invade vacant niches. In northern Wisconsin lakes, the introduced crayfish Orconectes rusticus is replacing two ecologically similar resident congeners, O. virilis and O. propinquus. In laboratory experiments, we compared growth and mortality of individually maintained crayfish offered one of five ad libitum diets: invertebrates, macrophytes, dentritus, periphyton or all items combined. Mortality was highest for O. virilis and lowest for O. rusticus. Macrophyte diets yielded the highest mortality. All three species grew best on invertebrate and combination diets but grew little or not at all on diets of periphyton, detritus or macrophytes. O. rusticus and O. virilis grew more than O. propinquus. O. rusticus grew more quickly and/or was better able to survive overall than its congeners. Therefore, O. rusticus would probably have advantages over O. virilis and O. propinquus in competitive interactions, reproductive success and avoiding size-selective fish predation. Subtle interspecific differences may interact strongly with other ecological factors and contribute to the displacement of resident species from a well-occupied niche.     

Bilateral and unilateral antennal lesions alter orientation abilities of the crayfish, Orconectes rusticus.

Numerous animals use chemical cues within their environments to execute various behaviors. One of these behaviors is orientation to an odor source. Crayfish, in particular, can orient to food sources under a number of different conditions. It has not been determined, however, what kind of search strategy these animals employ to successfully locate a food source. To determine the role of antennae and antennules in this behavior and to investigate different modes of orientation behavior, the orientation patterns of crayfish with complete and partial antennal lesions were examined. Detailed analysis of orientation paths confirmed that crayfish could not locate odor sources with either bilateral or unilateral lesions. This suggests that crayfish are using the spatial information obtained from these appendages to successfully orient. Animals using information from the bilaterally paired appendages in the control group exhibited increased walking speed, increased speed to source and decreased heading angles towards the source compared to these measurements taken from lesioned groups. There was no significant difference in any parameters between animals with unilateral or bilateral lesions. This strongly suggests that these animals are reliant on the spatial comparison of differences between bilaterally paired olfactory appendages for successful orientation.     

Behavioral effects of serotonin and serotonin agonists in two crayfish species, Procambarus clarkii and Orconectes rusticus

Exogenous serotonin elicits several behaviors in Procambarus clarkii, including a flexed, elevated posture, reduced locomotion, and changes in aggressive behavior. We conducted experiments to determine if several serotonin agonists mimicked the behavioral effects of serotonin in two crayfish species, P. clarkii and Orconectes rusticus. Drugs tested were 1-(3-Chlorophenyl)-piperazine dihydrochloride (mCPP), Oxymetazoline, 2,5-dimethoxy-4-iodoamphetamine (DOI), CGS-12066A, and (+/-)-8-hydroxy-2-(di-n-dipropylamino) tetralin (8-OH-DPAT). In P. clarkii, mCPP most closely mimicked the effects of serotonin, significantly increasing the performance of the flexed, elevated posture and reducing locomotion; 8-OH-DPAT significantly reduced locomotion as well. Both of these drugs produced significant increases in elevated posture and decreases in locomotion in O. rusticus, and in this species, the drugs at test concentrations were more effective in eliciting these effects than serotonin. The effects of the drugs on behaviors performed during fighting bouts were variable. In both species, only 8-OH-DPAT significantly reduced several agonistic behaviors, and no agonist or 5-HT itself produced significant increases in agonistic behavior.     

Behavioural and growth differences between experienced and naïve populations of a native crayfish in the presence of invasive rusty crayfish

1. Species invasions are a leading threat to native species and ecosystems. How populations of native species respond to the presence of invasive species will ultimately determine their long-term persistence.
2. In this study, we capitalise on a unique opportunity to compare the behaviour and growth of naïve and experienced virile crayfish ( Orconectes virilis Hagen) populations in the presence of invasive rusty crayfish ( O. rusticus Girard ) . In behavioural trials, experienced O. virilis (coexisted with O. rusticus for >30 years) showed more aggressive behaviour than their naïve counterparts. Naïve O . virilis retreated from aggressive interactions with O. rusticus 38% more often than experienced O . virilis. Experienced O. virilis spent 39% more time occupying shelter than naïve O. virilis.
3. There were also differences in O. rusticus behaviour: O. rusticus spent 24% more time occupying shelter with naïve O. virilis relative to experienced O. virilis .
4. In field mesocosm experiments with O. rusticus , naïve O . virilis declined in body mass by 1% while experienced O. virilis' body mass increased by 6%, thus highlighting the potential population-level implications of the previously observed behavioural effects.
5. Our work demonstrates significant behaviour and growth differences between naïve and experienced O. virilis in the presence of invasive O. rusticus. Whether this difference is the result of phenotypic plasticity or evolution by natural selection remains to be determined. Either way, this area of inquiry has implications for managing native populations and species in an increasingly invaded world.     

Exploration of potential microbial control agents for the invasive crayfish,Orconectes virilis

The introduced crayfish, Orconectes virilis (Cambarinae; Hagen 1870), has become a serious invasive species in Arizona (USA), altering stream ecosystems and contributing to the decline of native species. But because it is native to the eastern US, and related crayfish including endangered species inhabit nearby states, introduction of a biological control agent presents a unique challenge. This represents a feasibility study, in which we explored bacteria, nematodes, and a virus as potential biological control agents for O. virilis while avoiding harm to native species. White Spot Syndrome Virus (WSSV) from shrimp was found to be highly pathogenic and readily passed by cannibalistic behavior but not by water transmission. Potential activity of WSSV against representative non-target arthropods that may be found in the same ecosystems was also explored.     

Cross-species amplification of microsatellite markers in the invasive spiny-cheek crayfish (Orconectes limosus): Assessment and application

The North American spiny-cheek crayfish,Orconectes limosus (Cambaridae), endangered in its native range, is a widespread invasive species in European waters and conservationally important carrier of crayfish plague. However, its population structure is poorly known, and no informative genetic markers for the species are available. We tested cross-species transfer of microsatellite loci to spiny-cheek crayfish from 5 other crayfish species. Variability of 10 successfully amplifying loci derived from 4 species was then tested in 60 individuals ofO. limosus originating from 3 natural populations: the river Danube at Bogyiszló in Hungary, a pond in Stary Klíčov, and the brook Černovicky, both in the Czech Republic. The allele number within the populations ranged from 4 to 10 alleles per locus, while heterozygosity levels varied from 0.650 to 0.900 forHo and from 0.660 to 0.890 forHe. No linkage disequilibrium and no null alleles were detected. The selected markers are useful for assessing population structure, intraspecific variation, and paternity studies in spiny-cheek crayfish.     

Temporal shifts in physical habitat of the crayfish,Orconectes neglectus (Faxon)

A total of 300 samples was collected from February 1985 to August 1986 in a medium order Ozark Mountain stream. Physical habitat measurements of temperature, mean water column velocity, depth, and substrate character were recorded for each of the 25 monthly samples along with length and sex of all individuals of Orconectes neglectus (Faxon). Analysis of habitat utilization and suitability (or preference) was conducted using exponential polynomial models of hydraulic stress models. There appeared to be equal preference for depth over the range measured. Both substrate and velocity preference curves were bimodal with each mode designating certain crayfish size classes. Young-of-the-year were found primarily in cobbled, high velocity areas while adults were found in low velocity, macrophyte beds. Utilization curves for laminar sublayer thichness also reflected size-dependent phenomena where young-of-the-year were found in thin sublayer areas and adults were found primarily in thick sublayers. When separated by time and size, adults were found to occupy higher velocity, cobbled habitats during at least two months. This time period corresponded with the time of egg-bearing and further analysis yielded a time-dependent habitat suitability surface which accounted for this movement pattern. We suggest that the application of these suitability surfaces, which reflect habitat changes during the annual life cycle, will produce more accurate predictions of density and will allow better habitat management decisions under various regulated flow scenarios.     

The effect of aquatic plant chemistry and morphology on feeding selectivity by the crayfish, Orconectes virilis

SUMMARY. 1. Feeding preference trials conducted with male and female crayfish ( Orconectes virilis ) showed that out of ten submersed aquatic plant species, Chara sp. and Lemna trisulca were the preferred food sources, followed by Myriophyllum exalbescens or Utricularia vulgaris .
2. Analysis of plant fibre, alkaloid, total phosphorus, total and available nitrogen, and organic content showed that crayfish feeding preferences were not related ( P >0.5) to plant fibre or alkaloid content but were negatively correlated ( P <0.05) with plant nutrient content such that species of low nutritional value ( Chara and Lemna ) were consistently preferred.
3. Despite this preference for low nutrient food, daily intake rates by crayfish for phosphorus, nitrogen and organic matter were greatest when feeding on Lemna or Chara due to the large quantity consumed.
4. We suggest that feeding preferences of O. virilis are not determined by plant chemistry but, rather, relate to ease of handling small, short, bottom-dwelling plants such as Chara and Lemna as compared with large erect, roseate or floating-leaved forms. Because crayfish are selective herbivores, their introduction into waters where they do not naturally occur could have a dramatic effect on both the species composition and biomass of submersed plants.     

Fighting Strategies in Crayfish Orconectes rusticus (Decapoda, Cambaridae) Differ with Hunger State and the Presence of Food Cues

Crayfish, bearing dangerous weapons in the form of chelae, resolve intraspecific conflicts using stereotyped behaviors and structured, escalated encounters. According to predictions of game theory models, any decision to resort to unrestrained combat without prior careful behavioral assessment of the opponent's fighting abilities carries great risks. The present study examines the significance of internal hunger states and the presence of chemical food cues in this decision process using a 2 × 2 factorial design. Hungry crayfish escalated more rapidly, and thus took greater risks, during agonistic encounters, while the presence of a food source reduced the rate at which fights increased in intensity. However, there were no significant differences in fighting behavior as a result of the interaction between these two variables. We then address the complex trade-offs that individuals face in fighting with respect to increased risks of injury, appetitive states, and opportunities for resource access.     

Differences in growth and foraging behavior of native and introduced populations of an invasive crayfish

The competitive displacement of native by introduced species has often been attributed to differences in growth and behavior of the invader with its competitors. However, is the contribution of these traits to invasion success due to different competitor species between the native and introduced ranges or to differences among populations of the invader? Here we compared the growth and foraging behavior of the rusty crayfish (Orconectes rusticus) from its native and introduced ranges when competing with congeners from both ranges (O. cristavarius and O. propinquus, respectively). Our results indicated that O. rusticus from the introduced range grew significantly more than native O. rusticus and that there was no effect of competitor species on the growth of O. rusticus. Thus, the contribution of higher growth rates to the invasion success of O. rusticus was a result of population differences of O. rusticus in contrast to differences between congeners across both ranges. Foraging activity and recruitment to bait were higher in introduced versus native populations of O. rusticus when competing with O. cristavarius, but, not when competing with O. propinquus. Rather, O. propinquus significantly recruited to bait first when competing with either population of O. rusticus. However, 57% of the time that O. propinquus was first to find the bait, introduced O. rusticus aggressively pirated the bait from O. propinquus. In contrast, native O. rusticus were never observed pirating bait from O. propinquus. We suggest that this behavior may, in part, explain the higher growth observed in introduced populations of O. rusticus. The differences in behavior between O. rusticus populations depending on the competitor species may be due to behavioral flexibility that may drive higher growth rates in introduced populations of this species.     

The Behavioural Response of Mayfly Nymphs (Stenonema sp.) to Chemical Cues from Crayfish (Orconectes rusticus)

Artificial reef systems play an important role in the increase of natural production of biological marine resources and they have been deployed worldwide. In Portugal, seven artificial systems have been deployed along the southern coast of the Algarve. Research to date has focussed mainly on fish populations, particularly those of economical importance. The present work aims to study the macrobenthic communities of the artificial reef structures, as these will enhance the food resources and shelter, making the reefs more attractive to fish. In particular, we experimentally analysed the sequence of colonisation of macrobenthic communities of the Ancão artificial reef system, which was deployed in the summer of 2002. The study of the colonisation of benthic communities was done using samples of concrete cubic units (15 × 15 cm) that were suspended at the reef modules at a depth of 20 m, at the time of the reef immersion. Four replicate samples were collected by SCUBA diving from two groups of the Ancão reef every three months from the starting date. Sampling was done using essentially non-destructive methods to assess the percentage cover of macrobenthic organisms in both vertical and horizontal surfaces. The percentage cover of the taxonomic groups was compared within the different surfaces of the samples and between the two reef groups. The bottom surface of cubic samples had a significantly higher colonisation related to the dominance of barnacle cover, probably due to lower sedimentation levels. Samples from both reef groups showed a similar pattern of colonisation. Barnacles, bryozoans and serpulids dominated the samples three months immediately after the beginning of the experiment. Other invertebrates groups, such as Porifera, Hydrozoa, Anthozoa, other sessile Polychaeta, Decapoda, Gastropoda and Bivalvia, were more abundant after six months of colonisation.     

Divergent temperature-specific metabolic and feeding rates of native and invasive crayfish

Biological Invasions - Temperature is one of the most important factors governing the activity of ectothermic species, and it plays an important but less studied role in the manifestation of...     

The Influence of Dominance on Shelter Preference and Eviction Rates in the Crayfish, Orconectes rusticus

The establishment and reinforcement of dominance status is thought to provide an individual with increased access to preferred resources, such as food, mates, and shelter. Resources within an environment vary based on their availability, abundance, and specific characteristics of the resource. Animals can exhibit preferences for resources by increasing the intensity of competition for access to the resource. We investigated the role that dominance has in acquiring and controlling resources within crayfish populations. Populations of 5 size‐matched crayfish were allowed to establish a social hierarchy in the presence of shelters of differing structure in 10 different trials. Crayfish agonistic interactions and the use and control of shelters were quantified from 96 h continuous video recordings. Shelter preference was defined by crayfish use of specific shelter types that were occupied for longer durations. Analysis of the social hierarchy demonstrated that crayfish have a linearity hierarchy in this context. In addition, it is clear that dominance rank had a significant impact on shelter use, shelter acquisition, and shelter eviction. Crayfish with lower average dominance ranks selected specific shelter types (smaller and fewer openings). Dominant crayfish used big shelters and were less likely to be evicted from shelters. These results demonstrate that dominance in crayfish serves a role in the acquisition of resources and is also important for the control of those resources.     

Characterization of a molt-inhibiting hormone (MIH) of the crayfish, Orconectes limosus, by cDNA cloning and mass spectrometric analysis

The structure of the precursor of a molt-inhibiting hormone (MIH) of the American crayfish, Orconectes limosus was determined by cloning of a cDNA based on RNA from the neurosecretory perikarya of the X-organ in the eyestalk ganglia. The open reading frame includes the complete precursor sequence, consisting of a signal peptide of 29, and the MIH sequence of 77 amino acids. In addition, the mature peptide was isolated by HPLC from the neurohemal sinus gland and analyzed by ESI-MS and MALDI-TOF-MS peptide mapping. This showed that the mature peptide (Mass 8664.29 Da) consists of only 75 amino acids, having Ala75-NH2 as C-terminus. Thus, C-terminal Arg77 of the precursor is removed during processing, and Gly76 serves as an amide donor. Sequence comparison confirms this peptide as a novel member of the large family, which includes crustacean hyperglycaemic hormone (CHH), MIH and gonad (vitellogenesis)-inhibiting hormone (GIH/VIH). The lack of a CPRP (CHH-precursor related peptide) in the hormone precursor, the size and specific sequence characteristics show that Orl MIH belongs to the MIH/GIH(VIH) subgroup of this larger family. Comparison with the MIH of Procambarus clarkii, the only other MIH that has thus far been identified in freshwater crayfish, shows extremely high sequence conservation. Both MIHs differ in only one amino acid residue ( approximately 99% identity), whereas the sequence identity to several other known MIHs is between 40 and 46%.     

Proteinases from invasive larvae of the trematode parasite Schistosoma mansoni degrade connective-tissue and basement-membrane macromolecules.

Larvae of the human parasite Schistosoma mansoni, which invade the vascular system through the skin, secrete proteinases that degrade radioactively labeled extracellular matrices produced by smooth-muscle cells, dermal fibroblasts and endothelial cells. The proteinase purified from one larval form, the cercaria, degrades fibronectin and laminin and is a type-specific collagenase with activity against basement-membrane collagens IV and VIII, but not interstitial collagens I, III and V. The substrate specificity of this enzyme resembles that of the proteolytic enzymes which facilitate tissue invasion by inflammatory cells and tumour cells.     

Mortality curves of blind cave crayfish (Orconectes australis australis) exposed to chlorinated stream water

Chlorinated stream water toxicity was tested on the blind cave crayfish Orconectes australis australis from Merrybranch Cave, White County, Tennessee. An undisturbed natural cavern, Merry-branch was formed between two strata of sandstone having a mean elevation of 354 meters (MSL). Test water was collected from a subterranian stream in the cave supporting the hypogean crayfish population, and transported to the laboratory. No chlorinity was detected in the underground stream water.In the laboratory, cave water was chlorinated with sodium hypechlorus solution at various concentrations of total residual chlorine, combined residual, and free chlorine content as measured by Standard Methods titration procedure. Thirty-six crayfish, six crayfish per test solution, were subjected to a three day acclimation period at chlorine concentrations ranging from 0.21–1.50 mg./l. total residual chlorine, 0.20–0.30 mg./l. combined residual chlorine, and 0.01–1.20 mg./l. free chlorine; and then subjected t0 a 24 hour time-to-death (hourly) bioassay at the following chlorine water dilutions (mg./l.): (1) 7.45 total residual, 0.45 combined residual, and 7.00 free, (2) 3.39 total residual, 0.39 combined residual, and 3.00 free, (3) 2.85 total residual, 0.35 combined residual, and 2.50 free, (4) 2.30 total residual, 0.30 combined residual, and 2.00 free, (5) t.96 total residual, 0.21 combined residual, and 1.75 free, and (6) control. Fluctuations within these concentrations ranged from ± 0.20 free chlorine. All test solutions and a control were delivered by an Esvelt serial diluter. In addition, a 24 hour time-to-death (hourly) bioassay was conducted at the same dilutions 0n crayfish not acclimated to chlorine.These test demonstrated that crayfish mortalities generally increased with increasing concentrations of chlorine in both bio-assays, while acclimated crayfish tended to be more tolerant than non-acclimated ones.Funds for this research were provided by the Aquatic Ecology Fund, Biology Dept., Tennessee Technological University