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.     

Effects of fluoxetine on growth and behavior in the crayfish Orconectes rusticus

This laboratory study examined the effects of the specific serotonin reuptake inhibitor fluoxetine on growth following molting and on a range of behaviors in the crayfish Orconectes rusticus. For growth experiments, male Form I and Form II crayfish were weighed and measured and placed individually in water containing 0–500 μg/L of fluoxetine. They were held in fluoxetine or control water until they molted and were reweighed two weeks post-molt. In behavior experiments, juvenile and adult animals were held individually in 0, 2, 200, or 500 μg/L of fluoxetine for 10 days and tested in an open field arena to assess locomotion, thigmotaxis, sheltering, and habituation to a novel environment. Under our laboratory conditions, crayfish exposed to fluoxetine at 500 μg/L showed significantly enhanced growth: post-molt Form I animals had greater body weight and post-molt Form II animals had greater carapace length, relative to controls. In open field tests, juvenile crayfish exposed to 2 and 500 μg/L fluoxetine displayed significantly reduced locomotion compared to controls. The results indicate that crayfish growth and locomotion can be manipulated by short-term exposure to ambient fluoxetine, suggesting that this means of exposure may offer a useful and noninvasive way to examine drug effects in freely moving animals. However, effects were only observed at concentrations well above fluoxetine levels currently reported in the environment. This suggests that O. rusticus may be relatively resistant to this form of pharmaceutical pollution but whether effects would occur following long-term exposure to lower concentrations is unknown.     

Field observations of intraspecific agonistic behavior of two crayfish species,Orconectes rusticus and Orconectes virilis,in different habitats

Agonistic behavior is a fundamental aspect of ecological theories on resource acquisition and sexual selection. Crustaceans are exemplary models for agonistic behavior within the laboratory, but agonistic behavior in natural habitats is often neglected. Laboratory studies do not achieve the same ecological realism as field studies. In an attempt to connect laboratory results to field data and investigate how habitat structure affects agonistic interactions, the nocturnal behavior of two crayfish species was observed by scuba diving and snorkeling in two northern Michigan lakes. Intraspecific agonistic interactions were analyzed in three habitats: two food resources-macrophytes and detritus-and one sheltered habitat. The overall observations reinforce the concept that resources influence agonistic bouts. Fights in the presence of shelters were longer and more intense, suggesting that shelters have a higher perceived value than food resources. Fights in the presence of detritus patches had higher average intensities and ended with more tailflips away from an opponent, suggesting that detritus was a more valuable food resource than macrophytes. In addition, observations of aggressive behavior within a natural setting can add validity to laboratory studies. When fights in nature are compared with laboratory fights, those in nature are shorter, less intense, and less likely to end with a tailflip, but do show the fundamental fight dynamics associated with laboratory studies. Extrinsic and intrinsic factors affect intraspecific aggression in many ways, and both should always be recognized as having the potential to alter agonistic behavior.     

Infection with a trematode parasite differentially alters competitive interactions and antipredator behaviour in native and invasive crayfish

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Phenotypic variability of rusty crayfish (Faxonius rusticus) at the leading edge of its riverine invasion

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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.     

Intraguild predation between spawning smallmouth bass (Micropterus dolomieu) and nest‐raiding crayfish (Orconectes rusticus): implications for bass nesting success

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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.     

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.     

Spatial structure of hierarchical groups: testing for processes of aggregation,clustering, and spatial centrality in crayfish (Orconectes rusticus)

Competing group members tend to arrange in a social order that governs who will likely submit to whom. In many species the spatial distribution of individuals often reflects social status: dominants tend to occupy central locations while subordinates are often found along the group's periphery. This article explores the emergence of spatial consequences as a result of social rank differentiation. Rather than orienting centripetally, the movements of crayfish (Orconectes rusticus) primarily indicated a tendency to remain close to arena walls. Spatial locations were affected by the location of group members; but, rather than actively aggregating or clustering, individuals maintained a minimum distance. Previously established social rank did not affect spatial distributions. High population densities in the field are likely attributed to habitat constraints, rather than any social or centripetal tendencies of individual crayfish.     

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.     

Over-invasion in a freshwater ecosystem: newly introduced virile crayfish (Orconectes virilis) outcompete established invasive signal crayfish (Pacifastacus leniusculus)

Biological invasions are a key threat to freshwater biodiversity, and identifying determinants of invasion success is a global conservation priority. The establishment of introduced species is predicted to be hindered by pre-existing, functionally similar invasive species. Over a five-year period we, however, find that in the River Lee (UK), recently introduced non-native virile crayfish (Orconectes virilis) increased in range and abundance, despite the presence of established alien signal crayfish (Pacifastacus leniusculus). In regions of sympatry, virile crayfish had a detrimental effect on signal crayfish abundance but not vice versa. Competition experiments revealed that virile crayfish were more aggressive than signal crayfish and outcompeted them for shelter. Together, these results provide early evidence for the potential over-invasion of signal crayfish by competitively dominant virile crayfish. Based on our results and the limited distribution of virile crayfish in Europe, we recommend that efforts to contain them within the Lee catchment be implemented immediately.     

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.     

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.     

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.     

Effects of acclimation temperature,season, and time of day on the critical thermal maxima and minima of the crayfish Orconectes rusticus

• 1.1. The critical thermal minima (CTMin) and maxima (CTMax) were determined for field-acclimatized and laboratory-acclimated crayfish (Orconectes rusticus) throughout 1984.
• 2.2. The CTMin and CTMax of field-acclimatized crayfish were seasonally adjusted by 9.7 C and 14.7 C respectively.
• 3.3. Seasonal variation in both tolerance regimes persisted in crayfish acclimated in the laboratory at 5 and 25°C for one week; however, no diel variation existed in either the CTMin or CTMax of laboratory-acclimated crayfish.
• 4.4. Integration of thermal acclimation of the CTMin and CTMax with seasonal conditioning may influence the functional capacities of this species when considered in relation to the seasonal ranges in stream temperature.

     

Comparative Ecology of the Crayfishes Orconectes rusticus rusticus and Cambarus tenebrosus in Doe Run,Meade County,Kentucky

The ecology and life histories of Orconectes rusticus rusticus (GIRARD) and Cambarus tenebrosus HAY were investigated in a spring stream, Doe Run, Meade County, Kentucky, from September 1962 through September 1964. Differences in ecology of these species were most clearly seen in their habitat preferences and distributions in the stream, their feeding habits, responses to temperature, and infestations by an harpacticoid copepod Attheyella carolinensis CHAPPUIS, and in other life history phenomena, particularly with regard to reproduction and growth. Cambarus tenebrosus was most abundant in the constant temperature areas of the headwaters of Doe Run. Orconectes r. rusticus was found only in the lower three-fourths of the stream. Water temperatures in the headwater area may have been too low (12 — 14 C) for optimal growth of the crayfish had it existed there. Adults of C. tenebrosus were primarily hypogean, but young and subadults frequented the open stream environment. Orconectes r. rusticus was primarily an open stream inhabitant, and was sympatric with C. tenebrosus subadults and young in the downstream areas. When C. tenebrosus occurred in the open environment, it was most abundant in association with vegetation, and hence, was more heavily infested with A. carolinensis than O. r. rusticus. Detritus, mainly from fallen leaves and marl grazings, apparently formed the most important component of the diet of O. r. rusticus. Vascular plants, mainly fallen leaves from the riparian vegetation, constituted the main portion of the diet of C. tenebrosus; filamentous algae were widely used where and when they were present. Orconectes r. rusticus eggs hatch in May. These hatchlings become mature in 15 months and females oviposit after 22 – 24 months from March —May. Sexual maturity is attained at a carapace length of about 18 mm; maximum size is 45 mm. Most animals die after about 2.5 years; however, some live for three years. Molting activity ceases in winter. Cambarus tenebrosus young hatch in July and August. Most hatchlings remain in the burrows until October and November at which time they emerge in response to dominance behavior. Growth occurs throughout the winter months, and sexual maturity is attained in 20 – 22 months when the crayfish are about 40 mm in carapace length. Mature females oviposit during June and July after about 22–23 months, and probably again after 34–35 months. Mating occurs during the winter and spring. In Doe Run, maximum size attained is 65 mm carapace length. Cambarus tenebrosus probably lives for 36 – 38 months.     

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.     

Predation on invasive zebra mussel, Dreissena polymorpha, by pumpkinseed sunfish, rusty crayfish, and round goby

The enemy release hypothesis states that invasive species are successful in their new environment because native species are not adapted to utilize the invasive. If true for predators, native predators should have lower feeding rates on the invasive species than a predator from the native range of the invasive species. We tested this hypothesis for zebra mussel (Dreissena polymorpha) by comparing handling time and predation rate on zebra mussels in the laboratory by two North American species (pumpkinseed, Lepomis gibbosus, and rusty crayfish, Orconectes rusticus) and one predator with a long evolutionary history with zebra mussels (round goby, Neogobius melanostomus). Handling time per mussel (7 mm shell length) ranged from 25 to >70 s for the three predator species. Feeding rates on attached zebra mussels were higher for round goby than the two native predators. Medium and large gobies consumed 50–67 zebra mussels attached to stones in 24 h, whereas pumpkinseed and rusty crayfish consumed <11. This supports the hypothesis that the rapid spread of zebra mussels in North America was facilitated by low predation rates from the existing native predators. At these predation rates and realistic goby abundance estimates, round goby could affect zebra mussel abundance in some lakes.