Chemical cues from predators and damaged conspecifics affect byssus production in the green-lipped mussel perna viridis

Juveniles of the green-lipped mussel Perna viridis (Bivalvia: Mytilidae) were exposed to either chemical cues of damaged conspecifics or predator, including the swimming crab Thalamita danae and the muricid gastropod Thais clavigera. Byssus production was monitored for 48?h but the highest production rate occurred in the first 6?h. Longer and thicker byssal threads with a larger total volume were produced by P. viridis exposed to damaged conspecifics and predators as compared with the control. Numbers of individuals which shed stalks during the experiment varied significantly from 0 to 50%, and with a significantly higher value obtained for the control. Results indicated that byssus production is a plastic response which could be induced by exposure to chemical signals from predators and damaged conspecifics, the latter producing the largest response. Firmer byssal attachment not only reduces predation risk but also non-predation mortality by securing an animal more effectively to its habitat.     

Marine mussels Brachidontes variabilis selected smaller places of refuge and enhanced byssus production upon exposure to conspecific and heterospecific cues

Refuge selection and byssus production as anti-predator responses were examined in mussels Brachidontes variabilis exposed to cues either released from damaged or intact conspecifics, from damaged or intact heterospecific mussels Perna viridis sympatric with B. variabilis or from shrimp meat as novel cues. Most of the mussels from all treatment groups would seek and stay in a refuge for the first few hours, with a significantly higher number of mussels from the damaged conspecific group seeking refuge. More mussels preferred a smaller refuge when they were exposed to conspecific or heterospecific cues; mussels from other treatments did not select particular sizes of refuge. Damaged conspecific and heterospecific cues elicited the greatest responses in byssus production with more byssal threads being produced, which were also longer and thicker. Novel cues elicited medium levels of response, suggesting that some common cues from injured or dead individuals from different taxa were released, which induced anti-predator responses in B. variabilis.     

Responses of Littoraria irrorata say (Mollusca: Gastropoda) to water-borne chemicals: a comparison of chemical sources and orientation mechanisms

The salt marsh periwinkle, Littoraria irrorata, exhibits orientation behaviors in response to a number of chemical stimuli. In this study, we quantified the response of L. irrorata to chemical stimuli derived from three sources: Spartina alterniflora (a food source), the blue crab Callinectes sapidus (a predator), and crushed conspecifics. Animals consistently moved toward sources of S. alterniflora extract and crushed conspecifics relative to controls, but did not approach or avoid extracts from C. sapidus relative to controls. Animals had lower response rates to stimuli from S. alterniflora than to controls, but not to putatively aversive chemical stimuli (C. sapidus or crushed conspecifics). However, periwinkles that moved in experimental groups and control groups did not differ in how far they crawled. In addition, we measured turning angles of pathways of periwinkles to determine the orientation mechanism used. Littoraria irrorata displayed a taxis in response to crushed conspecifics, but a kinesis in response to C. sapidus and S. alterniflora. Our results suggest that the ecological context of chemical cues influence the evolution of orientation mechanisms. Cues that require immediate response (crushed conspecifics) elicit directed movement using taxis, whereas those that represent less alarming stimuli (a blue crab in the vicinity) or that represent a ubiquitous resource (Spartina) elicit movement by kinesis.     

Responses of larval dragonflies to conspecific and heterospecific predator cues

Abstract.  1. In cannibalistic populations, smaller individuals are subject to predation by larger conspecifics, and small individuals commonly alter their behaviour in response to cannibals. Little is known, however, about the underlying cues that trigger such responses and how the behavioural responses to conspecific cannibals differ from heterospecific predators.
2. This study tests which cues are used for the detection of conspecific predators in the larva of the dragonfly Plathemis lydia and how the behavioural response to cannibals differed from the response to heterospecific predators.
3. Individuals were exposed to chemical cues, visual cues, and a combination of both cues from conspecifics as well as no predator and heterospecific predator controls during which their activity and feeding rates were observed.
4. Individuals increased their activity, spatial movement and feeding behaviour in response to either visual or chemical cues from conspecific predators, which was opposite to responses displayed with cues from heterospecific predators. Interestingly, the responses to visual and chemical cues from conspecifics combined were weaker than to either cue in isolation and similar to the no cue control.
5. The results clearly indicate that individuals are able to use chemical and visual cues to detect even very subtle differences in phenotype of conspecific predators.
6. The opposite response in behaviour when exposed to conspecific cannibals vs. heterospecific predators suggests that the presence of cannibals will increase the mortality risk of small individuals due to heterospecific predation. This risk-enhancement is likely to have important consequences for the dynamics of predator–prey interactions.     

Species- and clone-specific responses to environmental stimuli in the cladocerans Bosmina cornuta and B. pellucida - a comparison with Daphnia

We studied the variation of small-scale swimming behaviour in eight Bosmina cornuta and ten B. pellucida clones in response to key environmental factors to test whether swimming behaviour and genotypes are linked in non-Daphnia cladocerans. We quantified (1) the short-term responses to changes in temperature, light intensity and pH, (2) the response to long-term temperature acclimation, and (3) the pH-related survival rates. Vertical swimming activity S was quantified in cuvette experiments as crossings of a line at 2 cm height per individual an hour. S differed significantly among species and conspecific clones. At any temperature, light intensity and pH tested, B. cornuta (clone variation: 40-58 crossings/ind.× h) showed a higher vertical swimming activity than B. pellucida (clone variation: 25-48 crossings/ind.× h). A short-term change of water temperature (range tested: 10-25°C) only affected S of B. cornuta, whereas that of B. pellucida remained unaltered. In contrast, S increased with rising temperature following long-term temperature acclimation (range tested: 10-20°C) in both species. Swimming activity was inversely related to the light intensity (range tested: 60-60,000 lux), but decrease of activity was stronger in B. pellucida (44 → 12 crossings/ind × h) than in B. cornuta (50 → 40 crossings/ind.× h). Short-term changes of pH (range tested: 4-6) did not influence swimming activity in any species, although a prolonged exposure (24 h) to pH 4 was lethal. Thus, Bosmina showed behavioural responses which permit to distinguish between the species and which are related to their seasonal succession and distribution pattern.     

The effect of light on oxygen consumption in two amphipod crustaceans-the hypogean Niphargus stygius and the epigean Gammarus fossarum

The effects of light on the metabolic rates of the hypogean amphipod Niphargus stygius and the epigean amphipod Gammarus fossarum were compared by measuring oxygen consumption and respiratory electron transport system (ETS) activity. They were exposed to light intensities of 720 and 4700 lx at 10°C. Oxygen consumption increased significantly in N. stygius exposed to both low and high intensities of light, but no significant increase was observed in G. fossarum at either intensity. The increase of oxygen consumption in N. stygius was significantly greater at the higher light intensity. This indicates a stress response in which exploitation of half the metabolic potential for energy production in N. stygius during exposure to high light intensity constitutes an adverse effect on its metabolism, since this species usually uses less than 25% of its total metabolic potential for standard metabolic demands.     

Direct and indirect cues of predation risk influence behavior and reproduction of prey: a case for acarine interactions

Little is known about the flow of chemical information fromhigher to lower levels within the animal food chain. However,this information may determine the behavior and distributionof many animals (e.g., that of potential prey) when exposedto direct and indirect cues of predation risk. We used herbivorousspider mites, Tetranychus urticae Koch (Tetranychidae) as amodel to examine the foraging and oviposition decisions thatprey make when exposed to these cues. We conducted laboratorytests to determine if the previous presence of predators (directcues) on leaf discs or the presence of injured conspecifics(indirect cues) alters the distribution of adults and eggs ofT. urticae. When given a choice, after 24 h, fewer adults and eggswere found on leaf discs that had previously contained specialistspider mite predators, Phytoseiulus persimilis Athias-Henriot (Phytoseiidae),than on discs unexposed to predators. Also, more T. urticaeemigrated from predator-exposed discs than from unexposed discs orfrom those that had previously contained nonpredatory mites(Tyrophagus putrescentiae, Acaridae). Finally, fewer T. urticaeforaged and laid eggs on predator-exposed discs or on thosewith artificially damaged conspecifics (eggs or dead adults)than on discs with intact conspecifics. Tetranychus urticaeprobably recognizes infochemicals (kairomones) from its predatorsor cues from injured spider mites and consequently avoids feedingor ovipositing in areas exposed to these cues. Recognition and avoidanceof kairomones from specialist predators by this prey are likelyto be hereditary, but avoidance of injured conspecifics maybe an adaptation to avoid predators that are not inherentlyrecognized. We discuss the behavioral and ecological implicationsof our findings.     

Aggression among sea urchins on Caribbean coral reefs

The existence and nature of intra- and interspecific aggression were examined for five species of sea urchins inhabiting Caribbean coral reefs. The studies took place in the San Blas Islands of Panama and involved the following species: Echinometra lucunter (Linnaeus), E. viridis Agassiz, Diadema antillarum Phillipi, Lytechinus williamsi Chesher, and Eucidaris tribuloides (Lamarck). An intruder was placed next to an undisturbed resident and the behaviors and responses of both individuals were followed. All pairwise combinations of resident species and intruder species were tested except for combinations involving D. antillarum as intruder.

For E. viridis and E. lucunter, agonistic interactions occurred commonly (46–79% of trials) between conspecifics and congeners. Almost all of the agonistic encounters involved pushing. Additionally, biting occurred in 8–25 % of the trials. Residents were most often the aggressors and usually succeeded in retaining their location. Intruders only succeeded in forcing residents out of their positions if the intruder was equal to or larger in size than the resident. Surveys of an undisturbed population of E. viridis during the daytime indicated that 16% of the individuals were engaged in intraspecific agonistic interactions at any one time.

D. antillarum exhibited biting behavior against both species of Echinometra in 23–24% of the trials. Biting attacks against L. williamsi and E. tribuloides occurred rarely. L. williamsi only once demonstrated pushing behavior and never was observed biting another sea urchin. E. tribuloides occasionally exhibited pushing and biting behaviors, both as residents and as intruders, and was twice observed biting Echinometra.

These studies suggest that two kinds of agonistic interactions may commonly occur among Caribbean reef-dwelling sea urchins: (1) intraspecific and interspecific aggression among Echinometra, and (2) predatory/aggressive attacks against Echinometra by D. antillarum. The former may result in greater dispersion of Echinometra relative to food and shelter resources and control the spatial distribution and concentration of Echinometra grazing pressure within an area. The attacks by D. antillarum may result in the restriction to, or higher densities of, Echinometra in crevices and rugose microhabitats that provide shelter from the larger-bodied D. antillarum.     

Social Context Influences the Antipredator Behaviour of Fathead Minnows to Chemical Alarm Cues

Prey fishes, like many organisms under fluctuating predation threat, rely on multiple sources of information to accurately gauge current risk. This includes the use of chemical cues such as alarm cues from damaged conspecifics or familiar heterospecifics, as well as the odour of known predators. While each fish is well equipped with its own array of sensory abilities, they should also be alert to the behaviours of nearby neighbours who may have information they lack. In the present study, we tested the ability of fathead minnows to use social cues in combination with the odour of damaged conspecifics and heterospecifics to mediate the assessment of predation risk. Specifically, we tested whether the presence of a shoal of conspecifics or familiar heterospecifics would significantly change a minnow's antipredator behaviour when exposed to the odour of a damage‐release cue from a conspecific or ecologically similar heterospecific. The results of our study showed a significant interaction between the damage‐release cues to which the minnows were exposed and the presence/absence of shoalmates. These findings have important implications for the design of future investigations of antipredator responses because most studies of group‐living prey have been conducted on solitary subjects.     

Reduced byssal thread production and movement by the intertidal mussel<Emphasis Type="Italic"> Hormomya mutabilis</Emphasis> in response to effluent from predators

Laboratory experiments were carried out to investigate byssal thread production by the intertidal mytilid mussel Hormomya mutabilis in response to effluent from the predatory crab Eriphia smithii and the starfish Coscinasterias acutispina. During the early period of the experiment, large H. mutabilis exposed to crab effluent produced a significantly smaller number of functional byssal threads than mussels in crab-free water. No significant difference in the diameter of threads produced in the two treatments was detected. The number of functional byssal threads produced by small H. mutabilis exposed to crab effluent did not differ significantly from that of mussels in crab-free water. However, small H. mutabilis exposed to crab effluent tended to discard fewer byssal bundles, that is, they shifted their attaching sites less frequently than similar mussels in crab-free water. In the presence of waterborne cues from the crab, H. mutabilis tended to reduce both the secretion of byssal threads and movement across the substratum. No significant differences in behaviour were observed between large mussels exposed to effluent from the starfish and those unexposed. The adaptive significance of the responses shown by H. mutabilis is discussed in terms of protection against predators differing in foraging behaviour. Electronic Publication     

Improved enzymatic two-phase biotransformation for (R)-phenylacetylcarbinol: Effect of dipropylene glycol and modes of pH control

An octanol/aqueous two-phase process for the enzymatic production of (R)-phenylacetylcarbinol (PAC) has been investigated further with regard to optimal pH control and replacement of 2.5 M MOPS buffer by a low cost solute. The specific rate of PAC production in the 2.5 M MOPS system controlled at pH 7 was 0.60 mg U^-1 h^-1 (reaction completed at 34 h), a 1.6 times improvement over the same 2.5 M MOPS system without pH control (0.39 mg U^-1 h^-1 at 49 h). An improved stability of PDC was evident at the end of biotransformation for the pH-controlled system with 84% residual carboligase activity, while 23% of enzyme activity remained in the absence of pH control. Lowering the MOPS concentration to 20 mM resulted in a lower benzaldehyde concentration in the aqueous phase with a major increase in the formation of by-product acetoin and three times decreased PAC production (0.21 mg U^-1 h^-1). Biotransformation with 20 mM MOPS and 2.5 M DPG as inexpensive replacement of high MOPS concentrations provided similar aqueous phase benzaldehyde concentrations compared to 2.5 M MOPS and resulted in a comparable PAC concentration (92.1 g L^-1 in the total reaction volume in 47 h) with modest formation of acetoin.     

Cue reliability, risk sensitivity and inducible morphological defense in a marine snail

Reliable cues that communicate current or future environmental conditions are a requirement for the evolution of adaptive phenotypic plasticity, yet we often do not know which cues are responsible for the induction of particular plastic phenotypes. I examined the single and combined effects of cues from damaged prey and predator cues on the induction of plastic shell defenses and somatic growth in the marine snail Nucella lamellosa. Snails were exposed to chemical risk cues from a factorial combination of damaged prey presented in isolation or consumed by predatory crabs (Cancer productus). Water-borne cues from damaged conspecific and heterospecific snails did not affect plastic shell defenses (shell mass, shell thickness and apertural teeth) or somatic growth in N. lamellosa. Cues released by feeding crabs, independent of prey cue, had significant effects on shell mass and somatic growth, but only crabs consuming conspecific snails induced the full suite of plastic shell defenses in N. lamellosa and induced the greatest response in all shell traits and somatic growth. Thus the relationship between risk cue and inducible morphological defense is dependent on which cues and which morphological traits are examined. Results indicate that cues from damaged conspecifics alone do not trigger a response, but, in combination with predator cues, act to signal predation risk and trigger inducible defenses in this species. This ability to “label” predators as dangerous may decrease predator avoidance costs and highlights the importance of the feeding habits of predators on the expression of inducible defenses.     

Over-expression of highly conserved mitochondrial 70-kDa heat-shock protein in the sea anemone Anemonia viridis

Organisms react to cellular stress by inducing the synthesis of heat-shock proteins (Hsp). One such protein is the mitochondrial 70-kDa Hsp (mHsp70). The expression of mHsp70 in organisms that undergo stress in their natural habitat is unknown. We used a biochemical approach enabling to identify an mHsp70 from the sea anemone Anemonia viridis, which is abundant in highly fluctuating marine habitats. Antibodies raised specifically against yeast mHsp70 recognized a 70-kDa protein from A. viridis. We found that A. viridis mHsp70 is constitutively expressed at 22–23 °C, but over-expressed upon exposure to heat shock (31 °C) or to temperature fluctuations, suggesting that mHsp70 plays a significant role in adaptation of sessile marine invertebrates to highly fluctuating environmental conditions. Using an affinity column we were able to obtain a partially purified fraction of this protein. Partial amino acid sequences proved that the purified Hsp70 functions in the mitochondria.     

Antipredator Behavior in Desmognathus ochrophaeus: Threat‐Specific Responses to Chemical Stimuli in a Foraging Context

Prey species may reduce the likelihood of injury or death by engaging in defensive behavior but often incur costs related to decreased foraging success or efficiency. To lessen these costs, prey may adjust the intensity or type of antipredator behavior according to the nature of the perceived threat. We evaluated the potential for threat‐sensitive responses by Allegheny Mountain dusky salamanders (Desmognathus ochrophaeus) exposed to chemical stimuli associated with predation by asking three questions: (1) Do individual D. ochrophaeus respond to chemical cues in a threat‐sensitive manner? (2) Do salamanders exhibit the same pattern of behavioral response while foraging? and (3) Is foraging efficiency reduced when focal individuals are exposed to stimuli from predators or predation events? In our first experiment, we evaluated salamander chemosensory movements (nose‐taps), locomotor activity (steps), and edge behavior in response to chemical stimuli from disturbed and injured conspecifics as well as predatory Gyrinophilus porphyriticus and found that individual D. ochrophaeus show a significant graded increase in nose‐taps when exposed to cues from conspecifics and a reduction in activity when exposed to the predator. In our second experiment, we again observed salamander responses to the same chemical stimuli but in this instance added five Drosophila prey to the test dishes. We found that salamanders exhibited a similar pattern of response to the chemical stimuli in the presence of prey, showing a graded increase in nose‐taps to cues from conspecifics and a reduction in activity when exposed to the predator. However, foraging efficiency (i.e. the proportion of successful strikes) did not vary significantly among treatments. Our data show that individual D. ochrophaeus detect and differentially respond to chemical stimuli associated with predation, but do not significantly reduce foraging efficiency. Overall, the type and relative intensity of these responses is largely unaffected by the presence of potential prey.     

Endogenous rhythm in activity of an estuarine amphipod, Talorchestia longicornis

The biological rhythm in activity of the supratidal amphipod Talorchestia longicornis Say was determined under constant conditions. Surface activity was monitored with a time-lapse video system under red light and assessed as the number of animals emerging from their burrows and active on a sand substrate at 0.5 h intervals. The amphipods had a circadian rhythm in which they were active at the time of night at the collection site. The rhythm could be entrained by a light : dark cycle and had an average free-running period of 23.7 h. Activity also appeared to be related to tidal times at the collection site because, under constant conditions, surface activity was suppressed at the time of nocturnal high tide and increased at the time of nocturnal low tide. The rhythm is functionally significant for foraging at night to avoid visual predators, desiccation and high temperatures.     

Algal colonization in urchin barrens: defense by association during recruitment of the brown alga Agarum cribrosum

We investigated the process whereby juveniles of the kelp Agarum cribrosum escape grazing by the green sea urchin, Strongylocentrotus droebachiensis, on urchin barrens in the rocky subtidal zone in the Mingan Islands, northern Gulf of St. Lawrence. The highest recruitment of juvenile A. cribrosum occurred under the canopy of the large filamentous phaeophyte Desmarestia viridis, where urchin densities were markedly reduced, compared to the surrounding area. This pattern of distribution appeared to be related to the wave-induced sweeping motion of D. viridis, although currents may modify the back and forth motion of the alga by pushing the canopy towards a specific direction, thereby allowing urchins to invade the non-swept areas. The density of juveniles under D. viridis plants increased with plant size and increasing proximity to the holdfast. Living under D. viridis slightly reduced the growth rate of the A. cribrosum juveniles, but this loss in growth was clearly outweighed by the gain in protection from sea urchin grazing. The time scale over which D. viridis provides protection is in the order of months, as D. viridis is an annual alga that disappears in early autumn. This defensive association of juvenile A. cribrosum with D. viridis is possibly a successional step leading to the formation of mature stands of A. cribrosum.     

三叶鬼针草与不同本地植物竞争对土壤 微生物和土壤养分的影响

入侵植物三叶鬼针草(Bidens pilosa)对我国农牧业生产造成了重大的损失。本文主要研究三叶鬼针草入侵与不同本地植物竞争对土壤微生物群落结构和土壤养分的影响。利用磷脂脂肪酸方法(phospholipid fatty acids, PLFAs)测定土壤微生物群落组成, 同时测定土壤养分和酶活性, 并利用Canoco4.5软件分析了土壤微生物、土壤养分和土壤酶活性的相关性。结果表明: (1)三叶鬼针草对革兰氏阳性菌、革兰氏阴性菌、丛枝菌根真菌等土壤微生物具有较强的聚集能力, 且其根际土壤聚集的微生物类群与本地植物种类密切相关。(2)三叶鬼针草入侵显著增加了入侵地土壤的有机碳含量, 降低了铵态氮的含量; 土壤中的速效钾、速效磷和硝态氮的含量则与本地植物种类密切相关。(3)相关性分析表明, 16:00和16:1 ω5c对铵态氮的含量影响较大, 而三叶鬼针草入侵地16:00和16:1 ω5c的含量显著高于裸土对照, 进而推测这一状况导致了铵态氮含量的降低。(4) 15:1 anteiso A和18:1 ω5c与速效钾的含量呈显著正相关, 而其含量在狗尾草(Setaria viridis)中显著高于其他处理, 三叶鬼针草与狗尾草混种处理中土壤中速效钾的含量高于其他处理。以上结果说明, 三叶鬼针草通过改变土壤微生物群落结构影响了土壤酶活性和土壤养分, 且这种改变与入侵地本地植物种类有关。     

邻苯二甲酸二甲酯(DMP)对海洋微藻的生态毒理研究

通过96h的急性毒性实验,研究了邻苯二甲酸二甲酯(DMP)对杜氏盐藻(Dunaliella salina)、绿色巴夫藻(Pavlova viridis)和三角褐指藻(Phaeodactylum tricornutum)三种海洋微藻的致毒效应,探讨了三种海洋微藻对DMP的耐受性及两者之间的相互作用。结果显示DMP对三种微藻的生长均有抑制作用,在DMP的处理浓度分别为0.1、10、40、80和200mg·L^-1时,与对照组相比,DMP生长抑制百分率分别为22.9～93.1%、42.1～82.2%和61.9～92.2%。DMP对对杜氏盐藻、绿色巴夫藻和三角褐指藻的EC₅₀值分别为103.3、43.9和0.12mg·L^-1。     

Individual discrimination in the big-clawed snapping shrimp, Alpheus heterochelis

Rahman et al. (Rahman, N., Dunham, D.W. and Govind, C.K. (2001). Mate recognition and pairing in the big-clawed snapping shrimp, Alpheus herterochelis. Mar. Fresh. Behav. Physiol., 34, 213-226.) demonstrated discrimination by snapping shrimp between former mates and unfamiliar conspecifics, but did not test individual discrimination. In the present study, snapping shrimp showed discrimination between familiar and unfamiliar same-sex conspecifics by preferentially entering that arm of a Y-maze leading to familiar individuals. Furthermore, after being exposed to water from the home tanks of unknown individuals, they later showed an elevated response to this water, if the direction from which the water came into their tank was changed to be novel. This indicates that test subjects associated a familiar chemical stimulus with its location in the environment. This discrimination could only have been made if that chemical signature were recognised as different from that of another chemically familiar individual. This result also demonstrates that the water surrounding an individual contains sufficient (chemical) information to allow discrimination of one individual from another.     

Side-effects of pesticides on the predatory bug Orius laevigatus (Heteroptera: Anthocoridae) in the laboratory

Laboratory trials were carried out in order to test the effects of 29 pesticides on the predatory bug, Orius laevigatus. To evaluate residual contact activity, newly moulted fourth instar nymphs of O. laevigatus were placed on treated Petri dishes and their mortality was checked after 7 days. The fecundity of surviving females was tested for 14 days. Young O. laevigatus adults were fed with eggs of Ephestia kuehniella, treated with the (above-mentioned) pesticides, to assess the effect of pesticides by ingestion. Adult mortality, female fecundity and egg hatching were recorded. Azadirachtin, granulosis virus products, mineral oil, pirimicarb, tebufenozide, clofentezine, hexythiazox and copper oxychloride had no significant effect on the survival and fecundity of O. laevigatus when predators were exposed to pesticide residues by contact or by ingestion. Triflumuron and diflubenzuron appeared to be harmless by contact, but diflubenzuron was slightly toxic when ingested. Buprofezin and teflubenzuron were slightly to moderately toxic, while hexaflumuron, flufenoxuron, and lufenuron showed a marked toxicity by contact as well as by ingestion. A number of organophosphates, endosulfan and deltamethrin were detrimental especially by contact. Imidacloprid was very toxic by contact but only slightly toxic when ingested. Indoxacarb and methoxyfenozide were less toxic than imidacloprid. These findings should be considered when releases of O. laevigatus are used in greenhouses or on outdoor crops.