Recognition Of Parasitic Eggs Research Articles

Parasite egg recognition based on multicomponent cues by green-backed tits (Parus monticolus)

Egg recognition and rejection is a common and effective anti-parasitism adaptation in bird hosts. Hosts reject alien eggs using recognition signals such as egg ground color and maculation. Green-backed tits ( Parus monticolus) have a highly developed capability for recognizing parasite eggs, but the cues used for egg recognition are unclear. We combined avian visual perceptual modeling and field experiments to explore the effects of egg ground color and maculation on the recognition of parasite eggs. P. monticolus uses a multi-cue with possible hierarchical mechanism for egg recognition. The mechanism of egg recognition in P. monticolus appears to be a specific adaptation to the phenotypes of eggs laid by local brood parasites.

Egg Size as the Main Stimulus to Discriminatory Behavior of the Yellow-Browed Warbler (Phylloscopus inornatus, Phylloscopidae) under Brood Parasitism of the Oriental Cuckoo (Cuculus optatus, Cuculidae)

Experimental studies were carried out on the behavior of the host concerning egg discrimination in three geographic populations of the Yellow-browed Warbler with different levels of brood parasitism of the Oriental Cuckoo. The absence of a spotted pattern on the shell of foreign eggs was shown to fail to serve as a stimulus to recognition. The acceptance or rejection of a foreign egg is determined by the ratio of the parasite to the host egg breadth, the mean size of the eggs in the individual host clutch also being of importance. This suggests that the recognition of parasite eggs by the host is based on the tactile contact of the female with the uneven surface of the clutch. The mean breadth of the Oriental Cuckoo eggs introduced into Yellow-browed Warbler nests is significantly smaller than the value at which the probability of egg rejection is equal to the probability of acceptance. As it is also smaller than in other gentes, this shows the adaptation of the brood parasite to this particular host. The acceptance of a foreign egg, ejection of it from the nest, and clutch desertion represent three stages of the same reaction in response to variation in a quantitative stimulus.

Egg trait variation in a large hawk-cuckoo (Hierococcyx sparverioides) host population of Chinese babax (Babax lanceolatus).

Mutual interaction between brood parasites and their hosts is a well-known model system for studying host-parasite coevolution. Both parties have acted reciprocally, resembling an evolutionary arms race, in which adaptations and counter-adaptations have evolved as a result of host-parasite dynamics, such as the classical cuckoo-host system. Discrimination among parasite and cuckoo eggs and rejection of foreign eggs is regarded as an important anti-parasitism strategy. The Chinese babax (Babax lanceolatus) is a large hawk-cuckoo (Hierococcyx sparverioides) host distributed in southwest China. A previous study shows that the babax is an intermediate egg rejector, and most cuckoo eggs are accepted by the Chinese babax, although a small proportion of hosts reject cuckoo eggs. Interestingly, the large hawk-cuckoo lays non-mimetic eggs in contrast to the uniform blue eggs of babaxes. Because egg coloration is a critical cue used by host species in favor of the recognition of parasitic eggs by hosts, we used a spectrometer to quantify egg color variation to understand the differentiation in discrimination ability between the egg rejectors and acceptors. We found that the chroma of intra-clutch variation of babax eggs was more consistent in egg rejectors than in acceptors. However, no statistical significance was found in inter-clutch variation between these two types of hosts. Our results suggest that hosts lay eggs with a low level of intra-clutch variation without the necessity of a high level of inter-clutch variation simultaneously as predicted by the egg signature hypothesis. This study may further indicate that selection pressures from evolutionarily recent parasites can drive individual-based differences in an anti-parasitism strategy.

Does nest luminosity play a role in recognition of parasitic eggs in domed nests? A case study of the red bishop.

Certain light environments may hinder egg discrimination by hosts of foreign eggs, which could in some circumstances lead to the acceptance of non-mimetic eggs by hosts. We measured light parameters at red bishop (Euplectes orix) nests and used a model of avian visual processing to quantify the detectability of eggs in the light environment in which they are perceived. We found that the overall amount of light was very variable between red bishop nests and always sufficient for colour discrimination. A model of avian visual processing revealed that nest luminosity had no influence on host responses towards eggs which were painted dark brown. Dark eggs do not appear to be cryptic in red bishop nests and can be distinguished with ease, whereas natural red bishop eggs are usually accepted, despite the domed structure of the nest. We found little variation in both chromatic and achromatic contrasts between host and artificial eggs, indicating that there was very little variation in the light quality inside nests. We suggest that nest luminosity is likely to play a role in egg recognition in situations when light reaches threshold values for colour discrimination, i.e. in scotopic as opposed to photopic vision. Rejection rates for dark eggs were higher than for bright (conspecific) foreign eggs. More investigation of domed nest-building species is required, as this type of nest appears to have a highly variable light environment, dependent on both nest structure and habitat.

How to Spot a Stranger's Egg? A Mimicry‐Specific Discordancy Effect in the Recognition of Parasitic Eggs

AbstractEgg discrimination by hosts is an antiparasitic defence to reject foreign eggs from the nest. Even when mimetic, the presence of brood parasitic egg(s) typically alters the overall similarity of all eggs in a clutch, producing a discordant clutch compared to more homogenous clutches of composed only of hosts’ own eggs. In multiple parasitism, the more foreign eggs are laid in the nest, the more heterogeneous the overall clutch appears. Perceptual filters and recognition templates cannot explain the known pattern of lower rejection rates of foreign eggs in multiple vs. single parasitism. We therefore assessed the role of clutch homogeneity and manipulated the colour of one or more eggs in the clutches of great reed warbler (Acrocephalus arundinaceus) hosts of common cuckoos (Cuculus canorus). Varying the colours of both the majority and the minority eggs caused predictable shifts in the rejection of the focal egg(s), and ejection rates of the minority egg colour consistently increased but only when it belonged to a more mimetic egg colour, relative to the less mimetic colour of majority eggs. The results imply that in addition to sensory filters, and template‐based cognitive decision rules, discordancy‐based rejection is affected by the overall clutch appearance and interacts with specific colours varying in the extent of mimicry, to contribute to the recognition decisions of hosts to reject parasitic eggs.

Egg size matching by an intraspecific brood parasite

Avian brood parasitism provides an ideal system with which to understand animal recognition and its affect on fitness. This phenomenon of laying eggs in the nests of other individuals has classically been framed from the perspective of interspecific brood parasitism and host recognition of parasitic eggs. Few examples exist of strategies adopted by intraspecific brood parasites to maximize success of parasitic eggs. Intraspecific brood parasitism within precocial birds can be a risky strategy in that hatch synchrony is essential to reproductive success. Given that egg size is positively correlated with incubation time, parasitic birds would benefit by recognizing and selecting hosts with a similar egg size. Intraspecific brood parasitism is an alternative reproductive strategy in black brant (Branta bernicla nigricans), a colonial nesting goose with precocial young. Based on a randomization test, parasitic eggs in this study differed less in size from eggs in their host's nests than did random eggs placed in random nests. Parasitic eggs were remarkably similar in size to hosts’ eggs, differing by <2% of volume on average from host eggs, whereas randomly paired eggs in random nests differed by nearly 8%. The precision with which parasitic brant match the egg size of hosts in our study supports our hypothesis that brant match egg size of hosts, thereby maximizing hatching success of their parasitic eggs.

Experimental reduction of ultraviolet wavelengths reflected from parasitic eggs affects rejection behaviour in the blackcapSylvia atricapilla

Hosts of brood parasites use a variety of cues relating to eggshell appearance of parasitic eggs, which facilitate their recognition and rejection. It has been documented that host visual perception of different colours including UV wavelengths plays an important role in this respect. In the study reported here, we aimed to test whether artificial reduction of the UV wavelengths reflected from parasitic eggshell affects rejection behaviour in the blackcap Sylvia atricapilla. To achieve this goal, we experimentally manipulated, with UV, part of spectra reflected from conspecific eggs and reduced it into the range of 320-350 nm. We used an ultraviolet light blocker, which did not influence the reflectance shape of other spectrum parts. We also used a group of experimental eggs coated in Vaseline, which had no effect on the spectral shape in the UV or visible ranges of the light spectrum. Additionally, we used a third experimental group of unmanipulated eggs as a control. The experimental eggs coated in the UV blocker were rejected at a higher rate than those coated in the Vaseline. Moreover, a binary logistic regression revealed that an artificial reduction of the UV wavelengths reflected from the parasitic egg significantly affected the probability of being rejected by the hosts. To our knowledge, this is the first experimental study to reveal that manipulation with UV wavelengths affects the recognition of parasitic eggs, indicating that the UV part of the spectrum has an important role in host recognition behaviour.

Colour characteristics of the blunt egg pole: cues for recognition of parasitic eggs as revealed by reflectance spectrophotometry

Variation in appearance of parasitic and host eggs is an essential trait in the coevolutionary struggle between a brood parasite and its host. Here we examined the role of colour characteristics in the egg recognition in blackcaps, Sylvia atricapilla, assessed by (1) human vision and (2) spectrophotometry, including UV wavelengths. Since colour and spotting pattern within eggs are often highly variable, we also assessed three different parts of blackcap eggshell separately. We investigated the possibility that a lower intraclutch variation in the parasitized clutch would positively affect egg recognition. In addition, we predicted that egg rejection would depend on contrast between host and parasitic eggs. However, we found that neither intraclutch variation nor mimicry if assessed by humans had significant effect on host rejection. Multivariate analyses of spectrophotometric data revealed, however, that the likelihood of egg rejection significantly increased with decreasing intraclutch variation in blue chroma. Furthermore, probability of egg rejection significantly increased with decreasing contrast between parasitic and host eggs in UV wavelengths and with decreasing brightness of host eggs at the blunt egg pole. Accepted foreign eggs were significantly darker at the blunt pole than acceptors' own eggs. The paradox that rejected eggs had lower contrast could be explained by the fact that the contrast in UV spectra is associated with brightness of the blunt egg part. Our data suggest that colour characteristics of the blunt egg part may play a major role in the recognition of parasitic eggs in the blackcaps.

Using active learning to annotate microscope images of parasite eggs

Microscopic analysis forms an integral part of many scientific studies. It is a task which requires great expertise and care. However, it can often be an extremely repetitive and labourious task. In some cases many hundreds of slides may need to be analysed, a process that will require each slide to be meticulously examined. Machine vision tools could be used to help assist in just such repetitive and tedious tasks. However, many machine vision solutions involve a lengthy data acquisition phase and in many cases result in systems that are highly specialised and not easily adaptable. In this paper, we describe a framework that applies flexible machine vision techniques to microscope analysis and utilises active learning to help overcome the data acquisition and adaptability problems. In particular we investigate the potential of various aspects of our proposed framework on a particular real world microscopic task, the recognition of parasite eggs.

Experimental Manipulation of Intraclutch Variation in the Great Reed Warbler Shows No Effect on Rejection of Parasitic Eggs

AbstractIn the continuing arms race between hosts and brood parasites, hosts are expected to reduce variation in the appearance of their own eggs within clutches, as it facilitates recognition of parasitic eggs. At the same time, by increasing interclutch variation, hosts should make it more difficult for parasites to evolve perfectly mimetic eggs. In this study, we experimentally manipulated intraclutch variation in the great reed warbler, Acrocephalus arundinaceus, in Hungary, where this species is heavily (c. 64%) parasitized by the common cuckoo, Cuculus canorus. We placed artificial cuckoo eggs, which appeared moderately mimetic to humans, in two groups of nests; in one group we increased variability of egg appearance within clutches by exchanging host eggs among nests. These clutches showed a significantly higher intraclutch variability than natural clutches, which we used as a control group. Our results indicate that it has no effect on rejection behaviour in this species, neither when variation was increased experimentally, nor within the natural range of variation displayed by our population. We suggest that when parasitism is high, selection for reduced intraclutch variation may be less important than frequency‐dependent selection for increased variation between individuals within a host population.

No evidence for variable duration of sympatry between the great spotted cuckoo and its magpie host

BROOD parasites and their hosts are thought to engage in a revolutionary arms race in which parasitism selects for adaptive defences by the host (such as egg rejection), which in turn select for counter-adaptations by the parasite (such as egg mimicry)1,2. Soler and Mo11er have tested whether the duration of coevolution (measured by the duration of sympatry at three different geo-graphic areas) in a host–cuckoo system affected egg-rejection behaviour by hosts3. They found that the extent of both rejection and recognition of parasitic eggs covaried positively with the duration of sympatry. Here we show that, in the absence of strong historical evidence, field data do not support the existence of variations in the duration of sympatry at the two areas where the distributional ranges of the cuckoo and its hosts overlap. The reported differences in egg rejection by hosts might alternatively reflect flexible behavioural responses to the presence of the adult parasite near the nest.