The impacts of flow on chemical communication strategies and fight dynamics of crayfish

Signal transmission is influenced by the physics of an environment. Consequently, a physical effect on sensory signals can influence how animals send or sample sensory information. Habitat-specific physics may constrain or enhance signal transmission (e.g. sound transmission in a flowing river versus a still pond) and provide a mechanism for the evolution of sensory biases. This study investigated how the transmission of chemically mediated social signals in crayfish is influenced by two different aquatic environments. Agonistic bouts between crayfish were performed under lotic (flowing water) and lentic (nonflowing, still water) conditions. When crayfish (Orconectes rusticus) collected from a lotic system (river) interacted under lotic conditions, we noted that dominant O. rusticus spent more time upstream than subordinate O. rusticus. Orconectes rusticus positioned themselves randomly and spent equal amounts of time with respect to upstream and downstream in the nonflowing environment. We tested another species, Orconectes virilis, collected from a nonflowing environment (lake) and they showed no positional preference when tested in flow. Additionally, both O. rusticus and O. virilis took longer to reach high fight intensities under flow conditions. It was possible to visualize O. rusticus urine release, and they released urine more often when upstream of an opponent in a flow environment during these agonistic bouts. These results suggest that O. rusticus collected from lotic environments release urine to maximize the transmission of chemical cues to a fight opponent. It appears that crayfish may adapt their signalling processes based upon their long-term ambient environments.     

The mate pursuit-predation avoidance tradeoff in the virile crayfish, Orconectes virilis

To better understand the tradeoff between mate pursuit and predation risk avoidance, the responses of male virile crayfish (Orconectes virilis) to female sex pheromone and conspecific alarm cue, alone and in combination were tested. Male crayfish were more active and exhibited less antipredator behavior in the pheromone treatment than in either the pheromone + alarm or alarm treatment. The results suggest a tradeoff in favor of risk avoidance when pheromone and risk stimuli are encountered together.     

Multimodal individual recognition in the crayfish cherax destructor

There is some evidence that macrurans recognize each other as individuals. In freshwater crayfish there are conflicting reports and there is limited information about the sensory mechanisms involved. To determine the extent to which the crayfish Cherax destructor is capable of individual recognition, we performed experiments that familiarized animals with each other and then manipulated their recent success in dominance contests. Crayfish were more likely to win an encounter when paired against a familiar opponent than an unfamiliar one after the manipulation stage. In other experiments, animals were attracted to familiar conspecifics when only visual or chemical cues were present. This demonstrates that C. destructor is able to discriminate between a familiar and an unfamiliar opponent. The results highlight the complex nature of intraspecific communication in crayfish and suggest elements likely to be of importance in the social interactions of groups in the wild state.     

Laboratory conditioning to still or flowing water does not affect the responses to a food stimulus by red swamp crayfish (Procambarus clarkii) in flowing water habitats

We tested the role of hydrodynamics in the use of chemical signals by the red swamp crayfish (Procambarus clarkii). We conditioned the crayfish in either a still water or flowing water habitat for 2 weeks. We then observed the crayfish in control (no stimulus) and experimental (food stimulus) trials in one of two flowing water habitats-laminar or turbulent. Habitat use was significantly different between control and experimental observations, but there was no effect of conditioning habitat or experimental habitat on the responses to the food stimulus. This study adds to a growing body of literature consistent with the idea that gross responses to chemical stimuli in crayfish are not affected by the hydrodynamic context in which they are encountered.     

Circadian Locomotor Activity in Freshwater Decapods: An Ecological Approach

Circadian rhythms of locomotor activity shown by freshwater decapods display different patterns among crayfish, Procambarus, and crabs, when exposed to artificial light-dark cycles. Crayfish are mainly nocturnal while a crepuscular activity is observed in crabs of the genus Pseudothelphusa. In constant darkness, free running rhythms are displayed in unimodal or bimodal patterns by crayfish Procambarus; however, Pseudothelphusa continues to show bimodal rhythms. The many studies using locomotor activity indicate that the rhythm in freshwater crabs is circadian in nature, but that a multioscillatory system may be controlling the overt rhythm. In the present study, the implications of different locomotor activity patterns are analyzed in selected freshwater decapods with regard to the interactions between light and the organisms. Crabs and crayfish are commonly found in similar habitats, often sharing the same environment; however, different patterns of locomotor activity as well as different sensitivities of the bouts of activity with regard to entrainment by light, indicate that distinct temporal niches may exist that result in temporal exclusion or low competition.     

Movement and dispersal of the invasive signal crayfish Pacifastacus leniusculus in upland rivers

1. The American signal crayfish Pacifastacus leniusculus, an invasive species widely introduced throughout Europe, is a major threat to native European crayfish species and is causing increasing concern because of its wide impact on aquatic ecosystems. 2. Whilst various control and management methods have been proposed, very little is known about the factors influencing dispersal and movements of signal crayfish. 3. Sixty‐four adult signal crayfish (carapace length 31.9–63.8 mm) were radiotagged in upland rivers in northern England, during four periods. Tracking was carried out at two sites, a low‐density establishing population and a high‐density established population. Tracking was carried out at both sites concurrently during midsummer (June to August 2002), during late summer (August to September 2001) at the low‐density population site and during autumn to winter (October to February 2000/01) at the high‐density population site. 4. Maximum movement occurred during midsummer. Temperature appeared to be a major factor influencing the timing and extent of movements between tracking periods. 5. The frequency distribution of the maximum distance moved upstream and downstream by radiotagged crayfish showed an inverse power relationship. The median maximal upstream and downstream distances moved were 13.5 m (range 0–283 m) and 15 m (range 0–417 m), respectively. There was a significant difference between the distributions of upstream and downstream ranges, with greater distances moved downstream. 6. All downstream movements made by crayfish appeared to be active movements and not the result of passive movement during periods of high discharge. There was no apparent influence of size, sex or density on the amount of movement recorded. 7. The study provides important information on the spatial and temporal behaviour of introduced crayfish in upland lotic systems. In contrast to lowland rivers, our results suggest that flow or gradient may influence the invasive potential of signal crayfish in an upstream direction in upland rivers.     

Detailed analysis of fighting in polecats (Mustelidae) using ciné film

The phenomenon of fighting was investigated under laboratory conditions using polecats ( Mustela putorius, M. furo and interspecific hybrids). Diadic interactions between male polecats were recorded on 16 mm cine film in an unfamiliar area of 16 m², one individual having been introduced ten minutes before its opponent.
The behaviour patterns involved in fighting are described and their frequencies of occurrence, duration and average bout lengths specified. Biting, which occupied 41% of the animal's time in fighting, and attacking, which made up 27% of the bouts of behaviour, were the most important actions involved in fighting. Polecats most commonly bite their opponent's neck and bites in this region were the longest in duration. Success in gaining a bite was influenced by the opponent's behaviour at the time of the attack.
Polecats fight when one individual bites its opponent and the opponent retaliates by biting; bite was shown to be the commonest response to being bitten. The length of a fight appears to be determined by the levels of motivation to bite of the two opponents, while biting and being bitten operate as a positive feed back mechanism. The fight terminates when the more aggressive opponent ceases to make spontaneous attacks. The reasons why one individual wins a fight are that it consistently spends more time than its opponent in biting, it persists for longer in making spontaneous attacks and its method of attacking is more efficient.     

Biocontrol of broomrape (Orobanche crenata Forsk. and Orobanche foetida Poir. ) by Pseudomonas fluorescens isolate Bf7-9 from the faba bean rhizosphere

Bacteria of the faba bean (Vicia faba L.)/Orobanche spp. root environment were evaluated for their potential use as biocontrol agents for the parasitic weed. Bacteria were isolated mainly from the rhizosphere of faba bean as well as from diseased Orobanche underground structures and an Orobanche-suppressive soil from three districts of northern Tunisia. Out of 351 bacterial isolates, 337 were tested for pathogenicity in an inverted pyramidal-shape screening programme including a Lactuca sativa L. seedlings bioassay, root-chamber and pot experiments. In pre-selection screening on L. sativa seedlings, 37 isolates (11%) showed a strong growth inhibitory effect, of which 70 and 84% also had a significant suppressive activity on the pre-emergence structures of O. foetida and O. crenata, respectively, in root-chamber experiments. Among five bacterial isolates selected for pot trials, strain Bf7-9 of Pseudomonas fluorescens showed high biocontrol activity against both species of Orobanche and positively influenced faba bean growth. The bacterium reduced shoot emergence of O. crenata and O. foetida by 64 and 76% and their dry weight by 39 and 63%, respectively, compared with non-inoculated controls. Pseudomonas marginalis strain Nc1-2 exhibited also a tendency to reduce incidence of O. crenata and to improve faba bean performance. Results of the present study suggest that application of naturally occurring rhizosphere bacteria offers an additional approach for biocontrol of Orobanche spp. that can supplement current methods of control in an integrated weed management strategy.     

Recording Behavioral Responses to Reflection in Crayfish

Social behavior depends on sensory input from the visual, mechanical and olfactory systems. One important issue concerns the relative roles of each sensory modality in guiding behavior. The role of visual inputs has been examined by isolating visual stimuli from mechanical and chemosensory stimuli. In some studies (Bruski & Dunham, 1987: Delgado-Morales et al., 2004) visual inputs have been removed with blindfolds or low light intensity, and effects of remaining sensory modalities have been elucidated. An alternative approach is to study the effects of visual inputs in the absence of any appropriate mechanical and chemosensory cues. This approach aims to identify the exclusive role of visual inputs. We have used two methods to provide visual stimuli to crayfish without providing chemical and mechanical cues. In one method, crayfish are videotaped in an aquarium where half of the walls are covered in mirrors to provide a reflective environment, and the other half are covered in a non-reflective (matte finish) plastic. This gives the crayfish a choice between reflective and non-reflective environments. The reflective environment provides visual cues in the form of reflected images of the crayfish as it moves throughout half of the tank; these visual cues are missing from the non-reflective half of the tank. An alternative method is to videotape the behavior of crayfish in an aquarium separated by a smaller chamber at each end, with a crayfish in one small chamber providing visual cues and an inert object in the opposite small chamber providing visual input from a non-moving, non-crayfish source. Our published results indicate that responses of crayfish to the reflective environment depend on socialization and dominance rank. Socialized crayfish spent more time in the reflective environment and exhibited certain behaviors more frequently there than in the non-reflective environment; isolated crayfish showed no such differences. Crayfish that were housed in same-sex pairs developed a social rank of either dominant or subordinate. Responses to reflection differed between dominant and subordinate crayfish (May & Mercier, 2006; May & Mercier, 2007). Dominant crayfish spent more time on the reflective side, entered reflective corners more frequently and spent more time in reflective corners compared to the non-reflective side. Subordinate crayfish walked in reverse more often on the reflective side than on the non-reflective side. Preliminary data suggest similar effects from visual cues provided by a crayfish in a small adjoining chamber (May et al., 2008).Download video file.^{(129M, mp4)}     

Habitat use by a Midwestern U.S.A. riverine fish assemblage: effects of season, water temperature and river discharge

The hypothesis that temperate stream fishes alter habitat use in response to changing water temperature and stream discharge was evaluated over a 1 year period in the Neosho River, Kansas, U.S.A. at two spatial scales. Winter patterns differed from those of all other seasons, with shallower water used less frequently, and low‐flow habitat more frequently, than at other times. Non‐random habitat use was more frequent at the point scale (4·5 m²) than at the larger reach scale (20–40 m), although patterns at both scales were similar. Relative to available habitats, assemblages used shallower, swifter‐flowing water as temperature increased, and shallower, slower‐flowing water as river discharge increased. River discharge had a stronger effect on assemblage habitat use than water temperature. Proportion of juveniles in the assemblage did not have a significant effect. This study suggests that many riverine fishes shift habitats in response to changing environmental conditions, and supports, at the assemblage level, the paradigm of lotic fishes switching from shallower, high‐velocity habitats in summer to deeper, low‐velocity habitats in winter, and of using shallower, low‐velocity habitats during periods of high discharge. Results also indicate that different species within temperate river fish assemblages show similar habitat use patterns at multiple scales in response to environmental gradients, but that non‐random use of available habitats is more frequent at small scales.     

The sporadic occurrence of a group I intron-like element in the mtDNA rnl gene of Ophiostoma novo-ulmi subsp. americana

The presence of group I intron-like elements within the U7 region of the mtDNA large ribosomal subunit RNA gene (rnl) was investigated in strains of Ophiostoma novo-ulmi subsp. americana from Canada, Europe and Eurasia, and in selected strains of O. ips, O. minus, O. piceae, O. ulmi, and O. himal-ulmi. This insertion is of interest as it has been linked previously to the generation of plasmid-like mtDNA elements in diseased strains of O. novo-ulmi. Among 197 O. novo-ulmi subsp. americana strains tested, 61 contained a 1.6 kb insertion within the rnl-U7 region and DNA sequence analysis suggests the presence of a group I intron (IA1 type) that encodes a potential double motif LAGLIDADG homing endonuclease-like gene (HEG). Phylogenetic analysis of rnl-U7 intron encoded HEG-like elements supports the view that double motif HEGs originated from a duplication event of a single-motif HEG followed by a fusion event that combined the two copies into one open reading frame (ORF). The data also show that rnl-U7 intron encoded ORFs belong to a clade that includes ORFs inserted into different types of group I introns, e.g. IB, ID, IC3, IA1, present within a variety of different mtDNA genes, such as the small ribosomal subunit RNA gene (rns), apo-cytochrome b gene (cob), NADH dehydrogenase subunit 5 (nad5), cytochrome oxidase subunit 1 gene (coxI), and ATPase subunit 9 gene (atp9).

We also compared the occurrence of the rnl-U7 intron in our collection of 227 strains with the presence of the rnl-U11 group I intron and concluded that the U7 intron appears to be an optional element and the U11 intron is probably essential among the strains tested.     

Genetic diversity and phylogenetic relationships of bacteria belonging to the Ochrobactrum-Brucella group by recA and 16S rRNA gene-based comparative sequence analysis

The genetic diversity and phylogenetic interrelationships among 106 Ochrobactrum strains (O. anthropi: 72, O. intermedium: 22, O. tritici: 5, O. oryzae: 2, O. grignonense: 2, O. gallinifaecis: 1, O. lupini: 2), the type strains of the eight Brucella species and other closely related taxa were studied by recA and rrs gene (16S rRNA) comparative sequence analysis. Both markers correctly delineated the various Ochrobactrum species; however, resolution at the subspecies level was considerably higher in the recA gene-based approach. Phylogenetic analyses using neighbor-joining, parsimony, and maximum likelihood algorithms generated trees with similar topologies but the overall branching order, and also the order of the subclades, were not stable in either assay, which could be explained by generally high recA and rrs sequence similarities. Ochrobactrum and Pseudochrobactrum formed separate clades distinct from other Alphaproteobacteria with Bartonella, Agrobacterium, and Rhizobium as the closest relatives. O. gallinifaecis was the most distinct member, when compared to the type species O. anthropi, with rrs and recA similarities of 96.2% and 81.4%. Brucella species were indistinguishable, exhibiting high rrs and recA gene similarities of 98.6% and 85.5% compared with Ochrobactrum intermedium. At the protein level, all RecA sequences among the various Ochrobactrum species and between Ochrobactrum and Brucella were highly similar with only a few amino acid substitutions. O. anthropi and O. tritici were indistinguishable by means of their RecA proteins. A set of initially biochemically classified strains did not cluster within their assigned species and they either grouped within other known species or grouped as potential novel Ochrobactrum species. In further investigations, these strains were reclassified and described as novel species. In summary, Ochrobactrum is a highly diverse genus comprising several novel species. We recommend recA- in addition to rrs gene-analysis for correct species allocation and subtyping of novel Ochrobactrum isolates.     

Critical thermal maximum and body water loss in first instar larvae of three Cetoniidae species (Coleoptera)

Critical thermal maximum (CT_max) and body water losses were measured in first instar larvae of Gnorimus nobilis, Osmoderma eremita (Trichiinae) and Cetonischema aeruginosa (Cetoniinae) when air temperature was increased gradually (0.5 °C/min) from 20 °C to the critical thermal maximum (CT_max), in dry air (near 0% R.H.).

The CT_max was significantly lower in O. eremita (45.6±0.7 °C) than in G. nobilis (48.5±0.6) and C. aeruginosa (51.4±0.9 °C).

An increase of 10 °C (30–40 °C) induced a 2-fold increase of the water loss in C. aeruginosa and O. eremita (Q₁₀=2.10±0.12 and 2.13±0.20, respectively). In the range from 40 to 45 °C to CT_max a strong increase of the water loss was observed in O. eremita and C. aeruginosa, respectively. Body water losses were significantly lower in C. aeruginosa than in O. eremita and G. nobilis over the range 20 °C—CT_max; no significant difference occurred between G. nobilis and O. eremita.     

Is sunflower (Helianthus annuus) at risk to damage from Ophraella communa,a natural enemy of common ragweed (Ambrosia artemisiifolia)?

Ophraella communa is being studied for augmentative releases in eastern Canada for Ambrosia artemisiifolia (common ragweed) control. Host specificity studies with cohorts of insects and a life table approach with individual insects were utilized to evaluate the risk of damage to sunflower. Predicting relative non-target attack and when and where this may occur is based on relative acceptability, suitability, and availability of host and non-host plants. We conclude the risk of O. communa adult-stage beetles attacking sunflower plants is negligible. In 20% open cages, over 98% of the adult O. communa left sunflower plants with few or no eggs laid. When the preferred host plants (A. artemisiifolia) are completely defoliated, the first instar larvae move to nearby sunflower plants in the immediate vicinity (up to 20-30 cm) and begin foraging. O. communa larvae can significantly damage sunflower, but 50% of the first instar larvae will die feeding on sunflower plants. The effect of low oviposition and high mortality will result in no increase in the O. communa population. Within 30 days, the O. communa population increased 208 times when feeding on ragweed and decreased 4.2 times when feeding on sunflower. Newly emerged adults leave the sunflower plants in search of ragweed. Damage to sunflower could occur during augmentative releases of O. communa, but this would only occur when a significantly large, advancing insect population has completely defoliated A. artemisiifolia within or adjacent to a sunflower field.     

Environmental DNA detects a rare large river crayfish but with little relation to local abundance

相似文献   

Flash flooding resistance of rice genotypes of Oryza sativa L., O. glaberrima Steud., and Interspecific hybridization progeny

In the costal area and inland valleys of Guinea, flash floods occur frequently following heavy rain during the rainy season. Young rice seedlings are particularly vulnerable to submergence stress due to insufficient height and carbohydrate reserves. In an attempt to characterize the physiological responses of young seedlings to flash flood, a wide genetic base including O. sativa, O. glaberrima, and interspecific hybridization progenies (IHP) was used.

Twelve day-old seedlings were submerged for 7 days, and plant height, dry matter accumulation (DMA), and lodging were measured. Upland rice (O. sativa) showed greater shoot elongation, larger reduction in DMA during submergence, and higher lodging, which lead to low flash flooding resistance (FFR). The physiological traits of most O. glaberrima and upland rice (O. sativa) to flash flood were opposite to those of submergence tolerant cultivars, as evidenced from the results of a principal component analysis. The physiological response of Saligbeli was different to other O. glaberrima genotypes in terms of FFR. Saligbeli exhibited enhanced shoot elongation with the increase in DMA during submergence. These features seemed to be a unique way to cope with submergence. Some IHP adapted to lowland cultivation showed traits similar to Saligbeli. The vigorous growth of Saligbeli and IHP underwater should be further investigated for improving FFR in rice.     

Interim Responses of Benthic and Snag‐Dwelling Macroinvertebrates to Reestablished Flow and Habitat Structure in the Kissimmee River,Florida, U.S.A.

A critical component in the effort to restore the Kissimmee River ecosystem is the reestablishment of an aquatic invertebrate community typical of free‐flowing rivers of the southeastern United States. This article evaluates early responses of benthic and snag‐dwelling macroinvertebrates to restoration of flow and habitat structure following Phase I construction (interim period) of the Kissimmee River Restoration Project. Replicate benthic and snag samples were collected from remnant river channels in Pool A (Control site), and Pool C, the site of the first phase of restoration (Impact site). Samples were collected quarterly for 2 years prior to construction (baseline) and monthly or quarterly for 3 years following Phase I construction and restoration of flow. Baseline benthic data indicate a community dominated by taxa tolerant of organic pollution and low levels of dissolved oxygen, including the dipterans Chaoborus americanus (Chaoboridae) and the Chironomus/Goeldichironomus group (Chironomidae). Baseline snag data indicate a community dominated by gathering‐collectors, shredders, and scrapers. Passive filtering‐collector invertebrates were rare. Following restoration of flow, benthic invertebrate communities are numerically dominated by lotic taxa, including bivalves and sand‐dwelling chironomids (e.g. Polypedilum spp., Cryptochironomus spp., and Tanytarsini). Snags within the Phase I area support an invertebrate community dominated by passive filtering‐collectors including Rheotanytarsus spp. (Chironomidae) and Cheumatopsyche spp. (Hydropsychidae). Results indicate that restoration of flow has resulted in ecologically significant changes to the river habitat template not observed in Pool A. Observed shifts in benthic and snag macroinvertebrate community structure support previously developed hypotheses for macroinvertebrate responses to hydrologic restoration.     

The presence of the potentially toxic genera Ostreopsis and Coolia (Dinophyceae) in the North Aegean Sea, Greece

The examination of macrophyte, water and sediment samples, collected at depths less than 1.5 m from 50 different sites along the North Aegean coasts, has revealed, for the first time in Greek coastal waters, the presence of two Ostreopsis species (O. ovata and O. cf. siamensis) and Coolia monotis in the majority of the sampling sites (94% and 100%, respectively). Other epiphytic dinoflagellates of the genera Prorocentrum and Amphidinium and diatoms were accompanying species in this epiphytic community. Morphometric features, plate formula and thecal ornamentation were used for species identification. O. ovata cells were smaller in dorsoventral (DV) diameter and width (W) (26.18–61.88 μm and 13.09–47.60 μm, respectively) in comparison with O. cf. siamensis (35.70–65.45 μm and 23.80–49.98 μm, respectively). In contrast, the anterioposterior (AP) diameter of O. cf. siamensis was smaller (14.28–26.18 μm) resulting in DV/AP ≈ 3, whereas the above ratio for O. ovata was less than 2 (AP ranging between 14.28–35.70 μm). Moreover, the theca of O. ovata cells was ornamented with scattered pores, which fluctuated in a wider range (0.07–0.32 μm) than those of O. cf. siamensis (0.23–0.29 μm). Coolia monotis cells were almost round with average DV diameter 26.88 μm, AP 25.66 μm and width 26.76 μm. Small and large cells were recorded in both field and culture populations of Ostreopsis spp. and C. monotis, while hyaline cysts were observed for O. ovata. The presence of O. ovata and O. cf. siamensis exhibited a clear seasonal pattern dominating (maximum abundance up to 4.05 × 10⁵ cells gr⁻¹ fwm) the period from midsummer to late autumn in years 2003 and 2004, while C. monotis was found also in winter and spring months.     

Morphology and wall ultrastructure of the spores of the Lower Devonian plant Oocampsa catheta Andrews et al., 1975

The enigmatic Lower Devonian plant Oocampsa catheta Andrews et al. (Can. J. Bot. 53 (1975) 1719) is considered intermediate between the trimerophytes and progymnosperms. In order to shed light on its evolutionary relationships, the morphology and ultrastructure of its sporangium and spores were analysed using light, scanning electron and transmission electron microscopy. In addition, dispersed spores (Grandispora douglastownense McGregor (Palaeontographica B 142 (1973) 1) and Grandispora ?macrotuberculata (Trudy VNIGNI 37 (1963) 18) McGregor (Palaeontographica B 142 (1973) 1), considered to possibly represent forms derived from O. catheta, were also examined. It is concluded that G. douglastownense and G. ?macrotuberculata are probably end members of the same spore complex and most likely are dispersed spores produced by O. catheta. Oocampsa catheta spores are bilayered. An inner body has an innermost part consisting of continuous, parallel-stacked, laminae and an outermost part consisting of more erratic, anastomosing, laminae. The inner body is surrounded by an homogeneous outer layer that is extended at the equator forming a pseudozona, and is folded on the proximal surface forming the trilete mark and on the distal surface forming spinose ornament. The spores are partially camerate. On the inside of the sporangium wall there is a layer probably representing the residue left following degeneration of a (probably secretory) tapetum. Spore morphology, gross structure and wall ultrastructure are compared to that of extant and fossil plant groups, and it is concluded that the spores of O. catheta are highly distinctive and do not conform closely to any plant group, although they show most in common with the spores of the progymnosperms.