Prey Detection and Prey Capture in Copepod Nauplii

Copepod nauplii are either ambush feeders that feed on motile prey or they produce a feeding current that entrains prey cells. It is unclear how ambush and feeding-current feeding nauplii perceive and capture prey. Attack jumps in ambush feeding nauplii should not be feasible at low Reynolds numbers due to the thick viscous boundary layer surrounding the attacking nauplius. We use high-speed video to describe the detection and capture of phytoplankton prey by the nauplii of two ambush feeding species (Acartia tonsa and Oithona davisae) and by the nauplii of one feeding-current feeding species (Temora longicornis). We demonstrate that the ambush feeders both detect motile prey remotely. Prey detection elicits an attack jump, but the jump is not directly towards the prey, such as has been described for adult copepods. Rather, the nauplius jumps past the prey and sets up an intermittent feeding current that pulls in the prey from behind towards the mouth. The feeding-current feeding nauplius detects prey arriving in the feeding current but only when the prey is intercepted by the setae on the feeding appendages. This elicits an altered motion pattern of the feeding appendages that draws in the prey.     

Adult Prey Neutralizes Predator Nonconsumptive Limitation of Prey Recruitment

Recent studies have shown that predator chemical cues can limit prey demographic rates such as recruitment. For instance, barnacle pelagic larvae reduce settlement where predatory dogwhelk cues are detected, thereby limiting benthic recruitment. However, adult barnacles attract conspecific larvae through chemical and visual cues, aiding larvae to find suitable habitat for development. Thus, we tested the hypothesis that the presence of adult barnacles (Semibalanus balanoides) can neutralize dogwhelk (Nucella lapillus) nonconsumptive effects on barnacle recruitment. We did a field experiment in Atlantic Canada during the 2012 and 2013 barnacle recruitment seasons (May–June). We manipulated the presence of dogwhelks (without allowing them to physically contact barnacles) and adult barnacles in cages established in rocky intertidal habitats. At the end of both recruitment seasons, we measured barnacle recruit density on tiles kept inside the cages. Without adult barnacles, the nearby presence of dogwhelks limited barnacle recruitment by 51%. However, the presence of adult barnacles increased barnacle recruitment by 44% and neutralized dogwhelk nonconsumptive effects on barnacle recruitment, as recruit density was unaffected by dogwhelk presence. For species from several invertebrate phyla, benthic adult organisms attract conspecific pelagic larvae. Thus, adult prey might commonly constitute a key factor preventing negative predator nonconsumptive effects on prey recruitment.     

Prey Selection by the Lady Beetle Harmonia axyridis: The Influence of Prey Mobility and Prey Species

The influence of prey mobility and species on prey selection by the coccinellid Harmonia axyridis Pallas was determined under laboratory conditions for two prey species, Hyaliodes vitripennis (Say) and Tetranychus urticae Koch. Prey selection was influenced by prey mobility. In the presence of active prey, the coccinellid selected T. urticae while in presence of immobilized prey, H. vitripennis was preferred. Harmonia axyridis searching time was longer in the presence of active H. vitripennis than in the presence of active T. urticae. Moreover, the coccinellid capture rate was lower for active H. vitripennis caused by effective defensive mechanisms. Prey suitability was affected by prey mobility and species. Immobilized H. vitripennis were the most profitable prey, i.e. induced a shorter developmental time and no mortality. However, active H. vitripennis were not a suitable food source for H. axyridis. Our results suggested that three factors are involved in prey selection by H. axyridis: (i) prey mobility; (ii) prey defensive mechanisms; and (iii) prey species.     

Effects of Prey Movement and Prey Odor on Feeding in Garter Snakes

The role of prey movement in feeding behavior was investigated in 10 garter snakes (Thamnophis sirtalis) repeatedly presented with paired stationary and continuously rotating sections of earthworm (Lumbricus terrestris). Additionally, prey odor intensity and source were varied and the performance of a tongueless snake was compared to normal animals. Experiment 1 showed that garter snakes will selectively attack rotating over nonmoving sections of earthworm across a wide range of speeds (1–2048 rpm) with an optimum between 16 and 256 rpm. However, blocking the odor from the sections and presentation of speeds greater than 500 rpm decreased response to moving sections. Experiment 2 showed that at 22–32 rpm moving sections were selected over stationary sections when odor from both was blocked. Experiment 3 assessed the effects of varying ambient odor conditions upon selection of artificial moving and stationary prey. Ambient earthworm odor resulted in a sustained high rate of tongue-flicking while, with no odor present, snakes showed a gradually increasing rate of tongue-flicking that declined within a few minutes. Experiments 4 and 5 studied the effects of tongue removal upon the selection of moving and nonmoving prey. Gross changes in the feeding sequence were noted. A long-term tongue-less adult fed by opening her mouth and thrashing about her cage when presented with earthworm odor and only preferred moving prey at 32 rpm; a control showed the normal stalk-and-strike sequence. The tongueless snake was less attracted to the moving earthworm at a distance than were normal snakes and the use of vision seemed less integrated rather than compensably improved. The results are discussed in reference to the critical flicker-fusion frequency, klepto-parasitism, and escape tactics of prey.     

Testing Predictions of the Prey of Lion Derived From Modeled Prey Preferences

Abstract: Apex predators are often threatened with extinction, and reintroduction is one method conservation managers are using to secure their persistence. Yet the ability to predict what these predators will eat upon reintroduction is lacking. Here we test predictions of the diet of the lion (Panthera leo), derived from dietary electivity index and optimality theory, using independent data collected from reintroduced and resident populations. We solved the Jacobs’ index preference equation for each prey species of the lion using values calculated by Hayward and Kerley (2005) and prey abundance data from 4 reintroduction sites and one resident lion population over several years. We then compared these estimates with actual kill data gathered from each site and time period, using the log-likelihood ratio and linear regression. The model precisely predicted the observed number of kills in 9 of the 13 tests. There was a highly significant linear relationship between the number of lion kills predicted to occur at a site and the number observed for all but one site (x̄r² = 0.612; β = 1.03). Predicting predator diet will allow conservation managers to stop responding and start planning in advance for reintroductions and environmental variation. Furthermore, ensuring that sufficient food resources are available is likely to increase the success of reintroduction projects. In addition, managers responsible for threatened prey species will be able to predict the vulnerability of these species to predation in the event of predator reintroductions or changes in abundance. These methods are applicable to virtually all large predators that have been sufficiently studied.     

Oviposition preferences of aphidophagous hoverflies

1. Oviposition preferences of two predatory hoverflies, Episyrphus balteatus and Syrphus ribesii (Diptera, Syrphidae), were studied in the laboratory. 2. There was broad agreement between the two species: two of the top three preferred prey for oviposition in both hoverflies were pea and rose aphids; nettle aphids were consistently the least preferred. 3. Discrimination decreased with age.     

桉树枝瘿姬小蜂产卵行为研究

桉树枝瘿姬小蜂Leptocybe invasa Fisher&La Salle喜好在桉属(Eucalyptus)植物的新生部位产卵。本研究以尾赤桉为寄主研究其产卵模式发现,当天羽化且没有产卵经验的雌成虫在经过寄主识别(116.87 s)和寄主评估(208.27 s)后即进行产卵循环(平均5.87次),每个产卵循环产2粒卵,且搜索行为的发生一般伴随产卵位置的变换。在被观察的15头雌成虫中,平均每头产卵13.60粒,每次产卵持续17.31 s。在产卵过程中,其刺探行为所占总时间的比例和发生频次最大,而静息行为最小。在不同寄主植物间,桉树枝瘿姬小蜂喜好在尾赤桉的叶柄和叶脉处产卵,且2个部位间无显著性差异,而在尾叶桉、巨尾桉、隆缘桉和小果灰桉上,其喜好在叶柄处产卵且显著大于其它2个部位。     

Oviposition pheromones in insect vectors

Oviposition aggregation pheromones occur in a range of insect groups including Diptera, where they mediate oviposition in four different families of disease vectors. In this paper, Philip McCall and Mary Cameron discuss the selection pressures favouring oviposition pheromones and speculate on their potential applications in disease monitoring and control.     

韦氏缩腹榕小蜂的产卵行为

通过对聚果榕上一种非传粉榕小蜂———韦氏缩腹小蜂ApocryptawestwoodiGrandi的产卵行为的详细观察 ,发现该小蜂的产卵行为与具有可伸缩的腹节这种奇特的腹部结构高度相关。该小蜂的产卵过程主要分为 3个阶段 :( 1 )寻找产卵位置 ,小蜂在果面快速搜索 ,以触角或口器触须感受产卵位点 ;( 2 )刺壁 ,小蜂将产卵针垂直于果面 ,刺入果壁 ,进入果腔 ;( 3 )产卵与拉出产卵针。通过与Ansari对于韦氏缩腹小蜂的产卵行为的描述进行比较 ,发现有如下不同之处 :( 1 )在产卵针刚刺入果面时 ,伸长的腹部末端超过头 ,整个伸长的腹部几乎与果面平行 ;( 2 )后足具有下拉产卵鞘的行为 ,并且后足除下拉产卵鞘时与果面分离外 ,均抓住果面 ;( 3 )产卵针不需要产卵鞘支撑时 ,产卵鞘与产卵针分离。     

Physiological Responses of Mesodinium major to Irradiance,Prey Concentration and Prey Starvation

Ciliates within the Mesodinium rubrum/Mesodinium major species complex harbor chloroplasts and other cell organelles from specific cryptophyte species. Mesodinium major was recently described, and new studies indicate that blooms of M. major are just as common as blooms of M. rubrum. Despite this, the physiology of M. major has never been studied and compared to M. rubrum. In this study, growth, food uptake, chlorophyll a and photosynthesis were measured at six different irradiances, when fed the cryptophyte, Teleaulax amphioxeia. The results show that the light compensation point for growth of M. major was significantly higher than for M. rubrum. Inorganic carbon uptake via photosynthesis contributed by far most of total carbon uptake at most irradiances, similar to M. rubrum. Mesodinium major cells contain ~four times as many chloroplast as M. rubrum leading to up to ~four times higher rates of photosynthesis. The responses of M. major to prey starvation and refeeding were also studied. Mesodinium major was well adapted to prey starvation, and 51 d without prey did not lead to mortality. Mesodinium major quickly recovered from prey starvation when refed, due to high ingestion rates of > 150 prey/predator/d.     

Prey location by Oechalia schellembergii

A total of 548 spiders (Gnaphosidae, Clubionidae, Thomisidae, Philodromidae, Salticidae, Lycosidae, Pisauridae, Linyphiidae) from three sand dune grassland sites were tested serologically for feeding on the grasshoppers, Chorthippus brunneus (Thunberg) and Myrmeleotettix maculatus (Thunberg). Lycosidae were the most commonly tested species and gave the greatest proportion of positive tests. Laboratory observations suggest that predation in the field was predominantly on first instar grasshoppers.

---

Résumé Afin d'améliorer la connaissance de l'importance des prédateurs dans la biologie des populations de criquets (Orthoptères; Acrididae), les araignées de trois pelouses sur dunes de sable ont été examinées sérologiquement pour estimer leur consommation des populations sympatriques de Chorthippus brunneus Thunberg et Myrmeleotettix maculatus Thunberg. Au total, 548 araignées (Gnaphosidae, Clubionidae, Thomisidae, Philodromidae, Salticidae, Lycosidae, Pisauridae, Linyphiidae) ont été récoltées à la main ou par piège pendant la période d'éclosion des ufs de criquets. Les Lycosidae ont été le plus fréquemment observées (90,5% de toutes les récoltes) et ont donné la plus forte proportion d'individus positifs (jusqu'à 32,3%). Les expériences d'alimentation en laboratoire suggèrent que, dans la nature, les Lycosidae sont les plus actives contre les criquets du premier stade.

     

Oviposition site selection of Episyrphus balteatus

The oviposition behaviour of Episyrphus balteatus DeGeer (Diptera: Syrphidae) was investigated in four-choice experiments in screen cages and in experiments with direct behavioural observations. Females laid hardly any eggs in the absence of aphids and preferred larger aphid colonies to small ones. Honeydew attracted the females via olfaction and elicited oviposition. Females were able to perceive the presence of conspecific eggs and oviposited less often in aphid colonies in which eggs were present. The oviposition deterring stimulus was also active when the eggs were removed, hence, the deterrent did not act visually, but probably olfactorily.     

Oviposition induced volatiles in tomato plants

In response to attack by herbivorous insect, plants produce semiochemicals which act to attract their natural enemies. Recent work on plant volatile compounds has shown that they may play multiple roles as communication signals and defense agents. Here we measured the volatile profile of tomato plants with and without oviposition by the herbivore moth, Tuta absoluta. We used solid phase micro extraction (SPME) sample pre-concentration techniques combined with gas chromatography-mass spectrometry. We have found that different volatile profiles emitted from tomato plants with oviposition by T. absoluta compared to control plants. Hexanal, (Z)-3-hexen-1-ol and an unidentified compound were isolated only from tomato plants with T. absoluta eggs. (Z)-3-hexen-1-ol was identified only from tomato plants with T. absoluta eggs that were laid three days earlier. The percentage of sesquiterpenes (e.g. δ-elemene) has been found to increase in the headspace of tomato plants with oviposition. These results in respect to indirect defense of tomato plants to T. absoluta are discussed.     

Ecological Consequences of Animal Migration: Prey Partial Migration Affects Predator Ecology and Prey Communities

Ecosystems - Patterns of animal migration and the ecological forces that shape them have been studied for centuries. Yet ecological impacts caused by the migration, such as altered...     

Prey dispersal and predator persistence

To understand how patchiness influences population dynamics of a tri-trophic interaction, a tractable model is formulated in terms of differential equations. Motivated by the structure of systems such as plants, phytophagous mites and predatory mites, the model takes dispersal into account at the middle trophic level. The effect of dispersal for the middle level in a tri-trophic system could be either stabilising or destabilising since the middle level acts both as prey and as predator. First a simple model with logistic growth for the lowest level is formulated. A model with logistic growth for the lowest level and instantaneous dispersal has a globally stable three-species equilibrium, if this equilibrium exists. Addition of a middle level dispersal phase of non-negligible duration influences equilibrium stability. In the absence of the top trophic level a limit cycle can occur, caused by the delay that exists in the reaction of the middle level to the changes in the lowest level. With low predator efficiency, it is also possible to have an unstable three-species equilibrium. So addition of a middle level dispersal phase of non-negligible duration can work destabilising. Next the persistence of the third trophic level is studied. Even when the three-species equilibrium exists, the third trophic level need not be persistent. A two-species limit cycle can keep its stability when a three-species equilibrium exists; the system is then bistable. It is argued that such a bistability can offer an alternative explanation for pesticide-induced outbreaks of spider mites and failure of predator introduction.     

Prey detection mechanism of elasmobranchs

Elasmobranchs can detect a little amount of electric fields and they have characteristic approach strategies to find an electric dipole source generated by prey or conspecifics. They appear to align the body at a constant angle with the current flow line of the electric field while swimming towards prey. However, it has not been studied how they process the perception of electric fields for the approach behaviour or what kind of neural mechanism is used. We use a model of electrosensory perception with electrodynamics and explore a possible approach mechanism based on the sensory landscape distributed on electroreceptors. This paper presents that elasmobranchs can estimate the direction of the electric field by swaying their head, which will be a basis information for their particular approach behaviour. A velocity profile of voltage gradients and intensity difference among the ampullary clusters can be another cues to detect a prey source.     

油松球果小卷蛾成虫的产卵选择

油松球果小卷蛾Gravitarmata margarotana(Heinemann)是广泛分布的一种松属球果和枝梢害虫,在我国北方油松良种基地主要危害油松球果。用油松和华山松球果做产卵选择试验,以及2树种球果浸提液对产卵影响的结果表明,油松球果对产卵雌虫具有更强的引诱作用;不同油松球果类型的着卵量结果表明,红色球果类型的着卵量显著高于绿色球果类型,并且同一颜色球果,有刺类型的着卵量多于无刺类型。球果挥发成分结果表明,油松球果挥发成分有6个组分,而华山松球果挥发成分只有5个组分,与油松球果相比,无β-非兰烯组分;油松不同株系类型球果挥发成分只表现出含量上的差异。     

Oviposition behavior of grape berry moth

Studies of the oviposition and host-finding behavior of grape berry moth (GBM) (Endopiza viteana Clemens) (Lepidoptera: Tortricidae) were prompted by reports of oviposition exclusively on grape (Vitis spp.) clusters. Eggs were deposited only on grape clusters under field conditions, but under controlled laboratory conditions in paired comparisons, eggs were also deposited on leaves. Oviposition within different areas of grapevines was proportional to the available substrate in those areas. Under natural light conditions, eggs were deposited during the 4 h period from 1900 to 2300 h. Most oviposition occurred during the low light conditions characteristic of dusk, but absence of light resulted in greatly reduced egg deposition. None of the artifical oviposition substrates that were evaluated elicited oviposition at rates comparable to those on unaltered grapes. Though paraffin and ceresin wax coatings made natural grapes unacceptable for oviposition by GBM, covering natural grapes with parafilm^® resulted in oviposition equal to that on unaltered grapes. Comparisons of Parafilm covered wooden models and Parafilm covered natural grapes illustrate that some stimuli from the natural grape are perceived through the Parafilm covering. Whole and crushed Emperor grapes and a mixture of apple esters gave strong antennal responses relative to grape volatiles extracted with hexane and Freon^TM 113 from an air filtration column.

---

Zusammenfassung Bericht über die spezifische Natur der nordamerikanischen Traubenmotte bei der Wirtswahl haben eine Studie über die Wirtsuche und Eiablage dieser Reben-schädling veranlasst. Im Freien wurden Eier nur auf Trauben gefunden, aber im Labor unter kontrollierten Bedingungen und mit gepaarten Vergleichen wurden Eier auch auf Blättern gelegt. Die Eiablagen innerhalb verschiedener Höhenstrata der Rebe waren proportional zum verfügbaren Substrat. Bei natürlicher Beleuchtung fand die Eiablage innerhalb einer 4 h Periode zwischen 1900 und 2300 h statt. Die meisten Eier wurden im abendlichen Zwielicht abgelegt, aber in absoluter Dunkelheit wurde die Eiablage stark reduziert. Keine der künstlichen Ovipositionsubstrate die geprüft wurden, hatte einen vergleichbaren Effekt auf die Eiablage, wie die auf natürlichen Trauben. Natürliche Trauben die mit Parafilm überzogen waren, sowie Trauben ohne Parafilm wurden zur Eiablage akzeptiert. Trauben die mit paraffin oder ceresin Wachs überzogen waren wurden hingegen abgelehnt. Vergleiche von hölzernen Parafilm überzogenen Trauben-modellen mit natürlichen Trauben zeigten, dass irgendwelche Stimuli der Traube durch die Parafilm-schicht wahrgenommen wurden. Intakte und gequetschte Emperor Trauben sowie eine synthetische Mischung Apfelestern verursachten relativ starke Elektroantennogramm Reaktionen. In Vergleich dazu waren Traubenduftstoffe von einer Duftstoff-Falle, die mit Hexan und Freon 113 extrahiert wurden, wenig aktiv. Die Ergebnisse könnten für den Einsatz von bestimmten Lockstimuli in Kombination mit Fallen oder künstlichen Ovipositionsubstraten angewendet werden.

     

Prey Preference of Aphidoletes Aphidimyza on Acyrthosiphon Pisum: Effect of Prey Color and Size

Color polymorphism in insects as well as factors contributing to its occurrence and maintenance have been of a great interest. Pea aphid (A. pisum) exhibits a noteworthy color polymorphism which occurs as red and green. The preference of the predatory gall midge Aphidoletes aphidimyza (Rondani) for the two color morphs of pea aphid at two life stages (adult and second instar) was investigated. Red adults, red nymphs, green adults, and green nymphs were offered to the larvae of the predator in different sets. The larvae attacked red aphids more than green ones of a same size. But whenever adults were offered along with nymphs, the nymphs experienced significantly more attacks. Although visual cues could result in more predation on red aphids, our findings showed that the size of aphids was the more important factor. The results showed that previous findings, suggesting more predation on the red morph, are valid when the same size of aphids is used. The ovipositing females exhibited no differences in oviposition choice between stalks infested with either of two colors.