Effects of the trematode Microphallus turgidus on locomotion and prey capture in the grass shrimp Palaemonetes pugio

The grass shrimp, Palaemonetes pugio, is common in estuaries and marshes along the east coast of the USA and is frequently infected with metacercariae of the trematode, Microphallus turgidus. To test whether or not M. turgidus has an effect on intermediate host behaviour, the length of time spent swimming and walking over 1 min and 3 min intervals and prey (Artemia) capture rates of uninfected grass shrimp and those infected with 1-10, 11-20 or 21-30 metacercarial cysts were compared. Uninfected shrimps spent significantly more time swimming than infected shrimps during the first minute of observation. There were no differences between the control and infected groups in terms of swimming at 3 min, walking at 1 and 3 min, or in numbers of prey captured. These results indicate that M. turgidus may induce little or no change in grass shrimp locomotion nor in prey capture behaviour. This is in contrast to other parasites that modify intermediate host behaviour to enhance their transmission to definitive hosts. Furthermore, these data support earlier studies indicating that M. turgidus does not affect the growth and survival of P. pugio.     

Prevalence,geographic distribution,and fitness effects of Microphallus turgidus (trematoda: Microphallidae) in grass shrimp (Palaemonetes spp.) from coastal Georgia

Grass shrimp, Palaemonetes pugio Holthuis and P. vilgaris (Say), were collected at 11 localities along the coast of Georgia and surveyed for digenetic trematode metacercariae. The effect of trematode infection on grass shrimp fitness was also examined. Microphallus turgidas (Leigh) was the only trematode observed. The prevalence of metacercarial cysts of this parasite in P. pugio (75%) was higher than in P. vulgaris (24%), as were the mean intensity, abundance, and population density (no. cysts/cm host body length) of the parasite. Infected shrimp were found at every collection locality and parasite prevalence and density were greatest in P. pugio from higher salinity localities (> or = 20 parts per thousand [ppt]). There was no relation between host body size and parasite density in P. vulgaris, and parasite density increased with host body size in P. pugio, suggesting that the parasite does not affect host survival. There was no relation between parasite density and shrimp egg mass, but nonovigerous female P. pugio were more heavily infected than ovigerous ones. In addition, 1 metacercaria of M. turgidus in each of 2 specimens of P. vulgaris was parasitized by the haplosporidian Urosporidium crescens De Turk. This represents a new shrimp host record for this hyperparasite.     

Serological estimation of prey-protein gut-residence time and quantification of meal size for grass shrimp consuming meiofaunal copepods

A series of experiments using serological reagents was conducted to examine predation, ingestion and digestion in a model predator-prey system. The harpacticoid copepod Amphiascoides atopus, obtained from mass culture, was used as prey and the grass shrimp, Palaemonetes pugio, as predator. Bulk-gut passage time in P. pugio was measured by visualization of latex beads and ranged from 0.5 to 4 h in starved and continuously-fed grass shrimp. A polyclonal antibody was prepared from crude extracts of A. atopus; cross reactions with P. pugio and three other crustaceans were either negligible or not detected using slide agar-gel-double-immunodiffusion (AGID) and Western blot preparations. The presence of A. atopus antigens was detected with great sensitivity (e.g., seven copepods, 35 μg dry weight, gave positive results) in grass shrimp gut contents even when proteins of other crustacean prey were present. Prey-proteins could be detected for as long as 4 h with AGID and 8 h with Western blot techniques. Individual grass shrimp that were fed A. atopus and consumed from 0 to 98 copepods h(-1) were subjected to Western-blot preparation with chemiluminescence detection and densitometric evaluation. There was a significant curvilinear relationship between protein content and the number of copepod prey ingested. Results suggest that serological techniques can be modified to estimate the mass or abundance of standard-sized prey ingested by field-collected predators.     

Implications of a fluctuating fish predator guild on behavior, distribution, and abundance of a shared prey species: the grass shrimp Palaemonetes pugio

In some systems, the identity of a prey species' dominant predator(s) may not be constant over time. In cases in which a prey species exhibits different responses to various predator species, such changes in predator identity may have population-wide consequences. Our goals were to determine (1) whether mortality of and refuge use by the grass shrimp, Palaemonetes pugio, were predator-specific, and (2) how effects of prey size and habitat interacted with predator type. Striped bass (Morone saxatilis) exerted twice as much predation pressure as mummichog (Fundulus heteroclitus), although not equally as great on large (female) and small (male) shrimp. Mummichog, which fed preferentially on large shrimp, forced a partitioning of habitat between the two shrimp size classes. In contrast, large and small shrimp occupied similar habitats when subjected to striped bass, which fed on both size classes equally. Refuge use of grass shrimp depended on predator type. In the presence of mummichog, which occupied shallower depths in the water column than striped bass, shrimp stayed deep and close to structural habitat. Striped bass, which were deeper, caused shrimp to move high in the water column away from structural habitat. When both predators were present, shrimp distribution was similar to that when only striped bass were present, striped bass predation rate was enhanced, and overall mortality was higher than with either predator alone. Results suggest that at times when mummichogs are the dominant predators, large (female) shrimp experience higher predation than small (male) shrimp and are physically separated from their potential mates. When striped bass are more abundant, male and female shrimp may share a similar, shallow, less structure-oriented distribution and be subjected to higher mortality. When both predators are present, mortality rates may be higher still. This predator-, size-, and habitat-specificity of grass shrimp behavior suggests significant population and distribution consequences of fluctuating predator guilds and fluctuating cover of structural habitats in the field.     

Optimization of culture conditions for in vitro fertilization and reproduction of Microphallus turgidus (Trematoda: Microphallidae)

Most attempts to culture adult digeneans in vitro are unsuccessful. Even progenetic digeneans typically fail to produce infective eggs in axenic culture. However, metacercariae of Microphallus turgidus grown in vitro mature into adults and release eggs infective to the hydrobiid snail Spurwinkia salsa. The objectives of the present study were to verify the reproducibility of the M. turgidus culture protocol, to define optimal culture conditions for M. turgidus further, and to investigate why the parasite can be grown successfully in the absence of the definitive host. In the original cultivation protocol, excysted M. turgidus metacercariae from grass shrimp (Palaemonetes pugio) were incubated overnight in a conical-bottom centrifuge tube containing Hank's balanced salt solution and then cultivated in flat-bottom culture plate wells containing RPMI-1640 plus 20% horse serum. The gas phase was air. Worms cultured under this protocol consistently deposited eggs infective to snails. Worms grown in anaerobic conditions deposited few eggs, and those cultured in a gas phase of 5% CO(2) survived longer and produced more eggs than those cultured in air. However, snails were less likely to become infected when fed eggs deposited by worms cultured in 5% CO(2). Additionally, worms incubated with conspecifics in conical-bottom tubes prior to cultivation were more likely to be inseminated than worms incubated in flat-bottom culture wells; the highest percentages of inseminated worms occurred when metacercariae were incubated 24 hr in conical-bottom tubes at a density of 50 worms/tube and at a temperature of 37 C. Worms incubated in the absence of conspecifics were not fertilized and failed to produce infective eggs.     

Effects of a muscle‐infecting parasitic nematode on the locomotor performance of their fish host

The southern flounder Paralichthys lethostigma, host to the nematode Philometroides paralichthydis that is embedded in place of the inclinator muscles of the dorsal and anal fin elements, is hypothesized to impair two aspects of locomotor performance (swimming and burying capacity). Peak swimming acceleration and both measures of burying performance did not differ between infected and uninfected fish, whereas swimming velocity of infected fish was significantly lower than that of uninfected fish. Smaller infected fish swam at significantly slower speeds than smaller uninfected fish, whereas there was no difference among larger fish. Neither the location nor the number of worms affected either swimming or burying performance. The decrease in swimming velocity observed in smaller infected fish may be sufficient in rendering them more vulnerable to predation and environmental stressors.     

An analysis of swimming performance in the Norway lobster, Nephrops norvegicus L. infected by a parasitic dinoflagellate of the genus Hematodinium

Various components of swimming performance were measured in uninfected Norway lobsters (Nephrops norvegicus) and compared to animals at different stages of infection by a parasitic dinoflagellate (Hematodinium sp.). Animals showed a progressive decline in overall swimming performance as infection severity increased, with reductions in the number of tail-flips performed, the number of swimming bouts and the total distance travelled by swimming. The velocity of the first (giant-fibre mediated) tail flip and average velocity over the swimming bout were also significantly reduced in infected lobsters. Possible reasons for this decreased swimming performance are suggested and the implications of this for predator avoidance of infected lobsters in the benthic habitat, and for capture of Nephrops by trawl rigs are discussed.     

Parasite-induced alteration of odour responses in an amphipod–acanthocephalan system

Odour-related behaviours in aquatic invertebrates are important and effective anti-predator behaviours. Parasites often alter invertebrate host behaviours to increase transmission to hosts. This study investigated the responses of the amphipod Hyalella azteca when presented with two predator chemical cues: (i) alarm pheromones produced by conspecifics and (ii) kairomones produced by a predatory Green Sunfish (Lepomis cyanellus). We compared the responses of amphipods uninfected and infected with the acanthocepalan parasite Leptorhynchiodes thecatus. Uninfected amphipods reduced activity and increased refuge use after detecting both the alarm pheromones and predator kairomones. Infected amphipods spent significantly more time being active and less time on the refuge than uninfected amphipods, and behaved as if they had not detected the chemical stimulus. Therefore, L. thecatus infections disrupt the amphipods’ anti-predator behaviours and likely make their hosts more susceptible to predation.     

Increased susceptibility to predation and altered anti-predator behaviour in an acanthocephalan-infected amphipod

According to the 'parasitic manipulation hypothesis', phenotypic changes induced by parasites in their intermediate hosts are effective means of increasing trophic transmission to final hosts. One obvious prediction, although seldom tested, is that increased vulnerability of infected prey to an appropriate predator should be achieved by the parasite altering the anti-predator behaviour of its intermediate host. In this study, we tested this prediction using the fish acanthocephalan Pomphorhynchus tereticollis and the freshwater amphipod Gammarus pulex. Firstly, we estimated the relative vulnerability of infected and uninfected gammarids to predation by the bullhead Cottus gobio in the field. Second, we investigated under experimental conditions how two common anti-predator behaviours of aquatic invertebrates, refuge use and short-distance reaction to predator chemical cues, were affected by infection status. We found that the prevalence of infection in the field was 10 times higher among gammarids collected from the stomach contents of bullheads compared with free-ranging individuals collected in the same river. In a microcosm uninfected gammarids, but not infected ones, increased the use of refuge in the presence of a bullhead. Finally, a behavioural experiment using an Y-maze olfactometer showed opposite reactions to predator odour. Whereas uninfected gammarids were significantly repulsed by the chemical cues originating from bullheads, infected ones were significantly attracted to the odour of the predator. Taken together, our results suggest that the alteration of anti-predator behaviour in infected G. pulex might enhance predation by bullheads in the field. Reversing anti-predator behaviour might thus be an efficient device by which parasites with complex life-cycles increase their trophic transmission to final hosts. Further studies should pay more attention to both the increased vulnerability of infected prey to an appropriate predator in the field and the influence of parasitic infection on the anti-predator behaviour of intermediate hosts.     

捕食驯化对胭脂鱼和中华倒刺鲃游泳行为、应激和免疫功能的影响

鱼类对环境的行为和生理适应能力与其在自然界的资源变动状况密切相关, 研究选取胭脂鱼(Myxocyprinus asiaticus)和中华倒刺鲃(Spinibarbus sinensis)幼鱼为研究对象, 考察1周捕食者(乌鳢, Channa argus)驯化对2种鱼类的运动能力(最大匀加速速度)、特异(血浆IgM水平)和非特异免疫(血浆溶菌酶含量)指标和抗氧化能力(血浆超氧化物歧化酶活性)的影响, 及在有无捕食者急性暴露两种条件下的驯化和非驯化鱼群自发游泳行为(游泳速度、运动时间比和个体间距离)和应激反应(血浆皮质醇水平)。研究发现: (1)总体上中华倒刺鲃比胭脂鱼有更快的游泳速度、更为活跃的自发游泳行为、更高的血浆皮质醇和IgM水平; (2)1周捕食驯化导致两种鱼类血浆皮质醇水平、特异免疫和非特异免疫水平的上升, 并且中华倒刺鲃比起胭脂鱼表现的更加明显; (3)急性捕食者暴露导致血浆皮质醇水平上升, 个体间距离下降, 但后者仅在非驯化组有所体现。研究表明: (1)捕食驯化鱼类通过皮质醇动员特异和非特异免疫应对应激, 这些生理和行为的改变可能有利于鱼类增强避敌能力或加快非致死捕食损伤的快速恢复。这表明捕食驯化可作为潜在的增殖放流前的生态锻炼; (2)2种鱼类的行为、免疫等生理基础状态及其对外界刺激的响应程度不尽相同, 未来相似的环境变化可能对两种鱼类的资源产生不同影响。     

An acanthocephalan parasite boosts the escape performance of its intermediate host facing non-host predators

Among the potential effects of parasitism on host condition, the 'increased host abilities' hypothesis is a counterintuitive pattern which might be predicted in complex-life-cycle parasites. In the case of trophic transmission, a parasite increasing its intermediate host's performance facing non-host predators improves its probability of transmission to an adequate, definitive host. In the present study, we investigated the cost of infection with the acanthocephalan Polymorphus minutus on the locomotor/escape performance of its intermediate host, the crustacean Gammarus roeseli. This parasite alters the behaviour of its intermediate host making it more vulnerable to predation by avian definitive hosts. We assessed the swimming speeds of gammarids using a stressful treatment and their escape abilities under predation pressure. Despite the encystment of P. minutus in the abdomen of its intermediate host, infected amphipods had significantly higher swimming speeds than uninfected ones (increases of up to 35%). Furthermore, when interacting with the non-host crustacean predator Dikerogammarus villosus, the highest escape speeds and greatest distances covered by invertebrates were observed for parasitized animals. The altered behaviour observed among the manipulated invertebrates supported the 'increased host abilities' hypothesis, which has until now remained untested experimentally. The tactic of increasing the ability of infected intermediate hosts to evade potential predation attempts by non-host species is discussed.     

Altered predator/prey behavior in polluted environments: implications for fish conservation

Predator/prey behavior has important consequences for individual survival and recruitment into fish populations, both of which can be affected by stressors such as environmental contaminants. The degree to which prey capture or predator avoidance abilities of a predator or prey species are affected will determine the direction in which the balance will be shifted. In a contaminated estuary we have studied, prey capure and predator avoidance of resident mummichogs, Fundulus heteroclitus, are impaired, which may account for individuals in that estuary having reduced growth and longevity compared with those from uncontaminated sites. Exposure to sediments, water, and grass shrimp from the contaminated site can impair the predatory abilities of mummichogs from a clean site. An important prey species, the grass shrimp, Palaemonetes pugio, has a greater population density and a greater proportion of large individuals at the polluted site, apparently because of reduced predation pressure. Mummichog larvae at the polluted site are initially more active and better at prey capture and predator avoidance than larvae from clean sites, but later they become poorer at both. Differences in predator vulnerability among larvae appear to be due to population differences in behavior, which may be due in part to both genetic and environmentally-caused factors. Conservation of fish populations should consider fish behavior and its interaction with contaminants.     

Swim or hide: predator cues cause species specific reactions in young fish larvae

The anti‐predator behaviour of first‐feeding (9 mm total length) hatchery‐reared pike Esox lucius larvae and wild‐caught three‐spined stickleback Gasterosteus aculeatus larvae was studied in the presence of chemical and visual signals from a fish predator. The results clearly showed that both fish species detected the predator by chemical signals alone but the combined chemical and visual signals caused stronger and more diverse reactions. Subsequent to predator detection, their swimming activity decreased, they attacked zooplankton less frequently and spent more time in the vegetation. Fishes differed in their anti‐predator responses. Pike reacted more clearly to chemical signals alone while three‐spined stickleback needed both chemical and visual cues to assess the predation risk. The strongest reaction was the reduction in swimming activity in the three‐spined stickleback (38% decrease) and a decrease in attack rate of the pike (39% decrease), but only when a refuge was available. Pike were more dependent on the vegetation cover showing almost no anti‐predator responses in the absence of a refuge. In addition, there was a difference in the refuge use of three‐spined stickleback between different macrophytes, indicating a complex or dense structure, which was difficult to penetrate or chemical excretion in one of them.     

Predator avoidance in mummichog larvae from a polluted habitat

Previous work has shown that adult mummichogs ( Fundulus heteroclitus ) from a polluted site (Piles Creek, PC, New Jersey) were more vulnerable to predation by blue crabs than fish from a more pristine site (Tuckerton, TK, New Jersey). The present study was conducted to compare the spontaneous activity, swimming performance and predator avoidance of fish of the two populations at early life stages. When raised in synthetic salt water, both newly hatched and 1–month-old mummichog larvae from TK had greater spontaneous activity, swimming performance, and stamina than those from PC. In comparison to TK, PC larvae were less vulnerable to predation by yearling mummichogs at 1 week old, but were more vulnerable at 1 month old. Variation in behaviour and swimming ability of TK and PC larvae accounted for the differences in vulnerability to predation. TK larvae employed greater swimming and irregular movement, which was more successful for survival of older larger larvae. In contrast, PC larvae hid, often remaining motionless, which was advantageous for survival of young smaller larvae. Contaminants had been assumed responsible for the behavioural differences in the PC population. However, since differences were seen in larvae raised in synthetic salt water, it is possible that maternally transferred neurotoxicants (possibly delayed effects) and/or inherent factors also play a role.     

Intraguild predation of the aphid pathogenic fungus Pandora neoaphidis by the invasive coccinellid Harmonia axyridis

Abstract.  1. The ladybird Harmonia axyridis is an invasive alien species in many countries and is predicted to have a negative impact on native biodiversity. However, little is known on the status of this aphidophage as an intraguild predator of natural enemies of aphids such as insect-pathogenic fungi.
2. The study assessed the predation of the aphid-specific pathogenic fungus Pandora neoaphidis by adult and larval H. axyridis collected from the U.K. (an invasive population) and Japan (a native population) relative to that of the ladybird Coccinella septempunctata (native to the U.K.) and the non-U.K. C. septempunctata subspecies brucki that were either starved or unstarved.
3. Overall, predation of uninfected aphids was greater than infected aphids and, when given a choice, a preference for aphids was shown. However, the extent of this preference was dependent on the species and origin of the coccinellid. Harmonia axyridis (U.K.) consumed the greatest quantity of fungal cadavers and showed little preference for uninfected aphids over infected aphids. In contrast, C. septempunctata rarely consumed infected aphids. Life stage had no direct effects on predation but starved coccinellids consumed more uninfected aphids than infected aphids.
4.  Harmonia axyridis (U.K.) is a stronger intraguild predator of P. neoaphidis cadavers than the native species C. septempunctata and, therefore, may have an impact on the occurrence and persistence of P. neoaphidis . The differences in intraguild predation by H. axyridis collected in the U.K. and those from Japan suggests that individuals that invaded the U.K. could have a different genetic profile to those in its native range.     

A parasite's modification of host behavior reduces predation on its host

Parasite modification of host behavior is common, and the literature is dominated by demonstrations of enhanced predation on parasitized prey resulting in transmission of parasites to their next host. We present a case in which predation on parasitized prey is reduced. Despite theoretical modeling suggesting that this phenomenon should be common, it has been reported in only a few host–parasite–predator systems. Using a system of gregarine endosymbionts in host mosquitoes, we designed experiments to compare the vulnerability of parasitized and unparasitized mosquito larvae to predation by obligate predatory mosquito larvae and then compared behavioral features known to change in the presence of predatory cues. We exposed Aedes triseriatus larvae to the parasite Ascogregarina barretti and the predator Toxohrynchites rutilus and assessed larval mortality rate under each treatment condition. Further, we assessed behavioral differences in larvae due to infection and predation stimuli by recording larvae and scoring behaviors and positions within microcosms. Infection with gregarines reduced cohort mortality in the presence of the predator, but the parasite did not affect mortality alone. Further, infection by parasites altered behavior such that infected hosts thrashed less frequently than uninfected hosts and were found more frequently on or in a refuge within the microcosm. By reducing predation on their host, gregarines may be acting as mutualists in the presence of predation on their hosts. These results illustrate a higher‐order interaction, in which a relationship between a species pair (host–endosymbiont or predator–prey) is altered by the presence of a third species.     

The effect of Echinorhynchus borealis (Acanthocephala) infection on the anti-predator behavior of a benthic amphipod

In benthic habitats, predators can generally not be detected visually, so olfaction may be particularly important for inducing anti-predation behaviors in prey organisms. Manipulative parasites infecting benthic hosts could suppress these responses so as to increase the probability of predation and thus trophic transmission. We studied how infection with the acanthocephalan Echinorhynchus borealis affects the response of the benthic amphipod Pallasea quadrispinosa to water conditioned by burbot (Lota lota), the parasite's definitive host. In normal lake water, refuge use by infected and uninfected amphipods was similar, but when exposed to burbot-conditioned water, uninfected amphipods spent much more time hiding than infected amphipods. Thus, rather than affecting ambient hiding behavior, E. borealis infection seems to alter host response to a predator. A group of amphipods sampled from a postglacial spring that is devoid of fish predators exhibited only a weak response to burbot-conditioned water, perhaps suggesting these anti-predator behaviors are costly to maintain. The hiding behavior of spring and infected amphipods was very similar. If the reduced refuge use by the spring amphipods reflects adaptation to a predator-free environment, this indicates that E. borealis severely weakens its host's anti-predator behavior. Presumably this increases the likelihood of parasite transmission.     

Impact of olfactory non-host predator cues on aggregation behaviour and activity in <Emphasis Type="Italic">Polymorphus minutus</Emphasis> infected <Emphasis Type="Italic">Gammarus pulex</Emphasis>

Parasites with a complex life cycle are supposed to influence the behaviour of their intermediate host in such a way that the transmission to the final host is enhanced, but reduced to non-hosts. Here, we examined whether the trophically transmitted bird parasite Polymorphus minutus increases the antipredator response of its intermediate host, the freshwater amphipod Gammarus pulex to fish cues, i.e. non-host cues (‘increased host abilities hypothesis’). Aggregation behaviour and reduced activity are assumed to decrease the predation risk of gammarids by fishes. Uninfected G. pulex are known to aggregate in the presence of a fish predator. In the present study, gammarids were allowed to choose either to join a group of conspecifics or to stay solitary (experiment 1) or between two groups differing in infection status (experiment 2), both in the presence or absence of fish odour. The perception of the groups was limited to mainly olfactory cues. Contrary to the ‘increased host abilities hypothesis’, in infected gammarids of experiment 1, fish cues induced similar aggregation behaviour as in their uninfected conspecifics. In experiment 2, uninfected as well as infected gammarids did not significantly discriminate between infected and uninfected groups. Although only uninfected gammarids reduced their activity in the presence of predator cues, infected G. pulex were generally less active than uninfected conspecifics. This might suggest that P. minutus manipulates rather the general anti-predator behaviour than the plastic response to predation risk.     

Effects of an infectious fungus, Batrachochytrium dendrobatidis, on amphibian predator-prey interactions

The effects of parasites and pathogens on host behaviors may be particularly important in predator-prey contexts, since few animal behaviors are more crucial for ensuring immediate survival than the avoidance of lethal predators in nature. We examined the effects of an emerging fungal pathogen of amphibians, Batrachochytrium dendrobatidis, on anti-predator behaviors of tadpoles of four frog species. We also investigated whether amphibian predators consumed infected prey, and whether B. dendrobatidis caused differences in predation rates among prey in laboratory feeding trials. We found differences in anti-predator behaviors among larvae of four amphibian species, and show that infected tadpoles of one species (Anaxyrus boreas) were more active and sought refuge more frequently when exposed to predator chemical cues. Salamander predators consumed infected and uninfected tadpoles of three other prey species at similar rates in feeding trials, and predation risk among prey was unaffected by B. dendrobatidis. Collectively, our results show that even sub-lethal exposure to B. dendrobatidis can alter fundamental anti-predator behaviors in some amphibian prey species, and suggest the unexplored possibility that indiscriminate predation between infected and uninfected prey (i.e., non-selective predation) could increase the prevalence of this widely distributed pathogen in amphibian populations. Because one of the most prominent types of predators in many amphibian systems is salamanders, and because salamanders are susceptible to B. dendrobatidis, our work suggests the importance of considering host susceptibility and behavioral changes that could arise from infection in both predators and prey.     

Consequences of temperature and temperature variability on swimming activity,group structure,and predation of endangered delta smelt

相似文献