Publications by authors named "Zoltán Barta"

50 Publications

Automated procedure assessing the accuracy of HRCT-PET registration applied in functional virtual bronchoscopy.

EJNMMI Res 2021 Jul 26;11(1):69. Epub 2021 Jul 26.

Division of Nuclear Medicine and Translational Imaging, Department of Medical Imaging, Faculty of Medicine, University of Debrecen, Nagyerdei krt. 98., Debrecen, 4032, Hungary.

Background: Bronchoscopy serves as direct visualisation of the airway. Virtual bronchoscopy provides similar visual information using a non-invasive imaging procedure(s). Early and accurate image-guided diagnosis requires the possible highest performance, which might be approximated by combining anatomical and functional imaging. This communication describes an advanced functional virtual bronchoscopic (fVB) method based on the registration of PET images to high-resolution diagnostic CT images instead of low-dose CT images of lower resolution obtained from PET/CT scans. PET/CT and diagnostic CT data were collected from 22 oncological patients to develop a computer-aided high-precision fVB. Registration of segmented images was performed using elastix.

Results: For virtual bronchoscopy, we used an in-house developed segmentation method. The quality of low- and high-dose CT image registrations was characterised by expert's scoring the spatial distance of manually paired corresponding points and by eight voxel intensity-based (dis)similarity parameters. The distribution of (dis)similarity parameter correlating best with anatomic scoring was bootstrapped, and 95% confidence intervals were calculated separately for acceptable and insufficient registrations. We showed that mutual information (MI) of the eight investigated (dis)similarity parameters displayed the closest correlation with the anatomy-based distance metrics used to characterise the quality of image registrations. The 95% confidence intervals of the bootstrapped MI distribution were [0.15, 0.22] and [0.28, 0.37] for insufficient and acceptable registrations, respectively. In case of any new patient, a calculated MI value of registered low- and high-dose CT image pair within the [0.28, 0.37] or the [0.15, 0.22] interval would suggest acceptance or rejection, respectively, serving as an aid for the radiologist.

Conclusion: A computer-aided solution was proposed in order to reduce reliance on radiologist's contribution for the approval of acceptable image registrations.
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http://dx.doi.org/10.1186/s13550-021-00810-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8313651PMC
July 2021

Inotocin, a potential modulator of reproductive behaviours in a biparental beetle, Lethrus apterus.

J Insect Physiol 2021 Jul 20;132:104253. Epub 2021 May 20.

MTA-DE Behavioural Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, H-4032 Debrecen, Egyetem tér 1, Hungary; Department of Evolutionary Zoology and Human Biology, University of Debrecen, Debrecen H-4032, Egyetem tér 1, Hungary.

Several members of the highly conserved oxytocin/vasopressin neuropeptide family are involved in the regulation of reproductive and affiliative behaviours in numerous vertebrate and invertebrate species. Here we investigate gene expression patterns of inotocin, the insect ortholog of this peptide family, and its receptor to decipher their possible role in the control of reproductive behaviour in a beetle, Lethrus apterus, with biparental care. In an experiment performed on individuals of a wild population, we found that inotocin is not related to the control of water balance in this species because expression patterns did not change as a response to drought exposure. The expression levels of inotocin and its receptor, however, increased over the reproductive season i.e., when behaviour shifts from pair formation to parental care, suggesting that inotocin might be involved in the regulation of parental care in this insect. No difference was, however, found between sexes; a finding which might indicate that inotocin plays a similar role in both parents.
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http://dx.doi.org/10.1016/j.jinsphys.2021.104253DOI Listing
July 2021

Draft genome of a biparental beetle species, Lethrus apterus.

BMC Genomics 2021 Apr 26;22(1):301. Epub 2021 Apr 26.

MTA-DE Behavioural Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Egyetem tér 1, Debrecen, H-4032, Hungary.

Background: The lack of an understanding about the genomic architecture underpinning parental behaviour in subsocial insects displaying simple parental behaviours prevents the development of a full understanding about the evolutionary origin of sociality. Lethrus apterus is one of the few insect species that has biparental care. Division of labour can be observed between parents during the reproductive period in order to provide food and protection for their offspring.

Results: Here, we report the draft genome of L. apterus, the first genome in the family Geotrupidae. The final assembly consisted of 286.93 Mbp in 66,933 scaffolds. Completeness analysis found the assembly contained 93.5% of the Endopterygota core BUSCO gene set. Ab initio gene prediction resulted in 25,385 coding genes, whereas homology-based analyses predicted 22,551 protein coding genes. After merging, 20,734 were found during functional annotation. Compared to other publicly available beetle genomes, 23,528 genes among the predicted genes were assigned to orthogroups of which 1664 were in species-specific groups. Additionally, reproduction related genes were found among the predicted genes based on which a reduction in the number of odorant- and pheromone-binding proteins was detected.

Conclusions: These genes can be used in further comparative and functional genomic researches which can advance our understanding of the genetic basis and hence the evolution of parental behaviour.
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http://dx.doi.org/10.1186/s12864-021-07627-wDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8074431PMC
April 2021

Experimental manipulation of body size alters life history in hydra.

Ecol Lett 2021 Apr 19;24(4):728-738. Epub 2021 Feb 19.

MTA-DE Behavioral Ecology Research Group, Department of Evolutionary Zoology, Univ. of Debrecen, Debrecen, Hungary.

Body size has fundamental impacts on animal ecology and physiology but has been strongly influenced by recent climate change and human activities, such as size-selective harvesting. Understanding the ecological and life history consequences of body size has proved difficult due to the inseparability of direct effects of body size from processes connected to it (such as growth rate and individual condition). Here, we used the cnidarian Hydra oligactis to directly manipulate body size and understand its causal effects on reproduction and senescence. We found that experimentally reducing size delayed sexual development and lowered fecundity, while post-reproductive survival increased, implying that smaller individuals can physiologically detect their reduced size and adjust life history decisions to achieve higher survival. Our experiment suggests that ecological or human-induced changes in body size will have immediate effects on life history and population dynamics through a growth-independent link between body size, reproduction and senescence.
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http://dx.doi.org/10.1111/ele.13698DOI Listing
April 2021

Social groups with diverse personalities mitigate physiological stress in a songbird.

Proc Biol Sci 2021 01 27;288(1943):20203092. Epub 2021 Jan 27.

MTA-DE Behavioural Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Debrecen, Hungary.

Social groups often consist of diverse phenotypes, including personality types, and this diversity is known to affect the functioning of the group as a whole. Social selection theory proposes that group composition (i.e. social environment) also influences the performance of individual group members. However, the effect of group behavioural composition on group members remains largely unexplored, and it is still contentious whether individuals benefit more in a social environment with homogeneous or diverse behavioural composition. We experimentally formed groups of house sparrows with high and low diversity of personality (exploratory behaviour), and found that their physiological state (body condition, physiological stress and oxidative damage) improved with increasing group-level diversity of personality. These findings demonstrate that group personality composition affects the condition of group members and individuals benefit from social heterosis (i.e. associating with a diverse set of behavioural types). This aspect of the social life can play a key role in affiliation rules of social animals and might explain the evolutionary coexistence of different personalities in nature.
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http://dx.doi.org/10.1098/rspb.2020.3092DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7893263PMC
January 2021

Phenotypic plasticity rather than genotype drives reproductive choices in Hydra populations.

Mol Ecol 2021 03 2;30(5):1206-1222. Epub 2021 Feb 2.

MTA-DE Behavioral Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Debrecen, Hungary.

Facultative clonality is associated with complex life cycles where sexual and asexual forms can be exposed to contrasting selection pressures. Facultatively clonal animals often have distinct developmental capabilities that depend on reproductive mode (e.g., negligible senescence and exceptional regeneration ability in asexual individuals, which are lacking in sexual individuals). Understanding how these differences in life history strategies evolved is hampered by limited knowledge of the population structure underlying sexual and asexual forms in nature. Here we studied genetic differentiation of coexisting sexual and asexual Hydra oligactis polyps, a freshwater cnidarian where reproductive mode-dependent life history patterns are observed. We collected asexual and sexual polyps from 13 Central European water bodies and used restriction-site associated DNA sequencing to infer population structure. We detected high relatedness among populations and signs that hydras might spread with resting eggs through zoochory. We found no genetic structure with respect to mode of reproduction (asexual vs. sexual). On the other hand, clear evidence was found for phenotypic plasticity in mode of reproduction, as polyps inferred to be clones differed in reproductive mode. Moreover, we detected two cases of apparent sex change (males and females found within the same clonal lineages) in this species with supposedly stable sexes. Our study describes population genetic structure in Hydra for the first time, highlights the role of phenotypic plasticity in generating patterns of life history variation, and contributes to understanding the evolution of reproductive mode-dependent life history variation in coexisting asexual and sexual forms.
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http://dx.doi.org/10.1111/mec.15810DOI Listing
March 2021

Behavioural flexibility and reputation formation.

Proc Biol Sci 2020 11 18;287(1939):20201758. Epub 2020 Nov 18.

MTA-DE Behavioural Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Egyetem ter 1. Debrecen 4032, Hungary.

Limited flexibility in behaviour gives rise to behavioural consistency, so that past behaviour is partially predictive of current behaviour. The consequences of limits to flexibility are investigated in a population in which pairs of individuals play a game of trust. The game can either be observed by others or not. Reputation is based on trustworthiness when observed and acts as a signal of behaviour in future interactions with others. Individuals use the reputation of partner in deciding whether to trust them, both when observed by others and when not observed. We explore the effects of costs of exhibiting a difference in behaviour between when observed and when not observed (i.e. a cost of flexibility). When costs are low, individuals do not attempt to signal that they will later be trustworthy: their signal should not be believed since it will always pay them to be untrustworthy if trusted. When costs are high, their local optimal behaviour automatically acts as an honest signal. At intermediate costs, individuals are very trustworthy when observed in order to convince others of their trustworthiness when unobserved. It is hypothesized that this type of strong signalling might occur in other settings.
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http://dx.doi.org/10.1098/rspb.2020.1758DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7739495PMC
November 2020

Environmental variability, reliability of information and the timing of migration.

Proc Biol Sci 2020 05 6;287(1926):20200622. Epub 2020 May 6.

MTA-DE Behavioural Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Egyetem ter 1, 4032 Debrecen, Hungary.

The timing of migration and migratory steps is highly relevant for fitness. Because environmental conditions vary between years, the optimal time for migration varies accordingly. Therefore, migratory animals could clearly benefit from acquiring information as to when it is the best time to migrate in a specific year. Thus, environmental predictability and variability are fundamental characteristics of migration systems but their relationship and consequence for migratory progression has remained unexplored. We develop a simple dynamic model to identify the optimal migration behaviour in environments that differ in predictability, variability and the number of intermediate stop-over sites. Our results indicate that higher predictability along migration routes enables organisms to better time migration when phenology deviates from its long-term average and thus, increases fitness. Information is particularly valuable in highly variable environments and in the final migration-step, i.e. before the destination. Furthermore, we show that a general strategy for obtaining information in relatively uninformative but variable environments is using intermediate stop-over sites that enable migrants to better predict conditions ahead. Our study contributes to a better understanding of the relationship between animal movement and environmental predictability-an important, yet underappreciated factor that strongly influences migratory progression.
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http://dx.doi.org/10.1098/rspb.2020.0622DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7282917PMC
May 2020

Consequences of rapid development owing to cohort splitting: just how costly is it to hurry?

J Exp Biol 2020 03 20;223(Pt 6). Epub 2020 Mar 20.

MTA-DE Behavioural Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, H-4032 Debrecen, Hungary.

In cohort splitting, diverging sub-cohorts may show substantial differences in their growth and developmental rates. Although in the past, causes and adaptive value of cohort splitting were studied in detail, individual-level consequences of cohort splitting are still rather overlooked. Life history theory predicts that considerably increased growth and developmental rates should be traded off against other costly life history traits. However, it is not clear whether one should expect such associations in adaptive developmental plasticity scenarios, because natural selection might have promoted genotypes that mitigate those potential costs of rapid development. To address these contrasting propositions, we assessed life history traits in the wolf spider , both collected from natural habitat and reared in laboratory. We found that some traits are negatively associated with developmental rates in spiders collected from the wild, but these associations were relaxed to a considerable extent in laboratory-reared specimens. In general, we observed no consistent trend for the presence of developmental costs, although some results might suggest higher relative fecundity costs in rapidly developing females. Our study provides a detailed approach to the understanding of individual-level consequences of cohort splitting, and to the associations between key life history traits in adaptive developmental plasticity scenarios.
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http://dx.doi.org/10.1242/jeb.219659DOI Listing
March 2020

Seasonal changes in immune response and reproductive investment in a biparental beetle.

J Insect Physiol 2020 Feb - Mar;121:104000. Epub 2019 Dec 18.

MTA-DE Behavioural Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Debrecen, Hungary.

Immunity and reproduction are physiologically demanding processes, therefore trade-offs are expected between these life history traits. Furthermore, investments in these traits are also known to be affected by factors such as sex, body size, individual condition, seasonal changes and parasite infection. The relationship between immunity and reproduction and the effect of other factors on this relationship were investigated in many species, but there are a small number of studies on these patterns in biparental invertebrates. Lethrus apterus is an iteroparous biparental beetle with predominant female care in respect of collecting and processing food for larvae. Males guard the nest built underground and also their mate. Here we investigate how sex, body size, time within the reproductive season and parasite load may influence the relationship between immunocompetence and reproductive investment in this species. In beetles from a natural population we quantified immune response by measuring the encapsulation response, antimicrobial activity of hemolymph, the investment into reproductive tissues by measuring the size of testis follicles in males and total egg size in females, and parasite load by counting the number of mites on the beetles. We found that the encapsulation response is condition-dependent, as large individuals showed significantly higher encapsulation ability than small ones. Antimicrobial capacity was significantly higher in females than in males. In case of antimicrobial activity there was also a seasonal change in the relationship between immunity and reproductive investment, but only under heavy mite load. Reproductive investment was influenced by the interaction between body size and season (in females) and by body size and season (in males). Furthermore in females the interaction between antimicrobial activity and season indicated that reproductive investment increased with antimicrobial activity early in the reproductive season. By investigating the relationship between immunity and reproductive investment in a natural population of a biparental beetle species, we can conclude that investments into these important life history traits are governed by complex interactions between physiological and environmental factors. Our results are discussed in the context of life history evolution, highlighting the role of the assessed factors in shaping trade-offs themselves (in invertebrates).
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http://dx.doi.org/10.1016/j.jinsphys.2019.104000DOI Listing
December 2020

Antibacterial immune functions of subadults and adults in a semelparous spider.

PeerJ 2019 23;7:e7475. Epub 2019 Oct 23.

MTA-DE Behavioural Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Debrecen, Hungary.

Although capacity to mount an efficient immune response plays a critical role in individuals' survival, its dynamics across ontogenetic stages is still largely unexplored. Life stage-dependent variation in the encountered diversity and prevalence of parasites were proposed to contribute to stage-dependent changes in immunity, but differences in life history objectives between developmental stages may also lead to stage-specific changes in efficiency of given immune mechanisms. The reason for this is that juveniles and subadults are unable to reproduce, therefore they invest resources mainly into survival, while adults have to partition their resources between survival and reproduction. The general trade-off between somatic maintenance and reproductive effort is expected to impair immune function. Especially so in semelparous organisms that only reproduce once throughout their lifetime, hence they do not face the trade-off between current and future reproduction. We hypothesised that in a semelparous species individuals would be characterised by decreased investment into somatic maintenance after maturation, in order to maximise their reproductive output. Accordingly, we predicted that (1) elements of somatic maintenance, such as immunity, should be relatively weaker in adults in comparison to subadults, and (2) increased reproductive investment in adults should be associated with lower immune efficiency. We quantified two markers of immunity in subadult and adult individuals of the semelparous wolf spider (Westring, 1861), namely bacterial growth inhibition power and bacterial cell wall lytic activity. We found that subadults showed significantly higher cell wall lytic activity than adults, but the two life stages did not differ in their capacity to inhibit bacterial growth. Also, we found weaker immune measures in mated females compared to virgins. Furthermore, in mated females bacterial growth inhibition power was negatively associated with fecundity.
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http://dx.doi.org/10.7717/peerj.7475DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6815191PMC
October 2019

Longevity and life history coevolve with oxidative stress in birds.

Funct Ecol 2019 Jan 16;33(1):152-161. Epub 2018 Oct 16.

Hungarian Department of Biology and Ecology, Evolutionary Ecology Group, Babeş-Bolyai University, Cluj-Napoca, Romania.

1. The mechanisms that underpin the evolution of ageing and life histories remain elusive. Oxidative stress, which results in accumulated cellular damages, is one of the mechanisms suggested to play a role. 2. In this paper, we set out to test the "oxidative stress theory of ageing" and the "oxidative stress hypothesis of life histories" using a comprehensive phylogenetic comparison based on an unprecedented dataset of oxidative physiology in 88 free-living bird species. 3. We show for the first time that bird species with longer lifespan have higher non-enzymatic antioxidant capacity and suffer less oxidative damage to their lipids. We also found that bird species featuring a faster pace-of-life either have lower non-enzymatic antioxidant capacity or are exposed to higher levels of oxidative damage, while adult annual mortality does not relate to oxidative state. 4. These results reinforce the role of oxidative stress in the evolution of lifespan and also corroborate the role of oxidative state in the evolution of life histories among free-living birds.
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http://dx.doi.org/10.1111/1365-2435.13228DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8291348PMC
January 2019

Sex-dependent immune response in a semelparous spider.

Naturwissenschaften 2018 Jun 7;105(7-8):39. Epub 2018 Jun 7.

MTA-DE Behavioural Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Debrecen, Hungary.

Previous studies on arthropods showed that seasonality and parity in breeding considerably impact the direction of sex differences in immunocompetence, and it has been suggested that life span and the time window available for breeding play key roles in shaping sex-differences in immunity. One proposed mechanism behind this phenomenon is differential investment into life history traits in sexes. Here, we tested whether in a seasonally breeding semelparous arthropod sexes differ in their immunocompetence, predicting that females would show weaker immune response than males. We compared encapsulation efficiency (a well-established and widely used method for assessing immunocompetence) of freshly matured, virgin males and females of the lycosid spider Pardosa agrestis (Westring, 1861). On average, males mounted stronger immune response than females and the extent of encapsulation was positively associated with prosoma length in males, but not in females. Also, time until maturation was positively related to the extent of encapsulation in both sexes, but did not significantly affect adult prosoma length. We propose that sex-difference in encapsulation is likely shaped by combined effects of relatively higher costs of reproduction in females, narrow time window of reproductive activity, and the absence of trade-off between current and future reproduction.
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http://dx.doi.org/10.1007/s00114-018-1568-7DOI Listing
June 2018

Demographic causes of adult sex ratio variation and their consequences for parental cooperation.

Nat Commun 2018 04 25;9(1):1651. Epub 2018 Apr 25.

Department of Animal Behaviour, Bielefeld University, Morgenbreede 45, 33615, Bielefeld, Germany.

The adult sex ratio (ASR) is a fundamental concept in population biology, sexual selection, and social evolution. However, it remains unclear which demographic processes generate ASR variation and how biases in ASR in turn affect social behaviour. Here, we evaluate the demographic mechanisms shaping ASR and their potential consequences for parental cooperation using detailed survival, fecundity, and behavioural data on 6119 individuals from six wild shorebird populations exhibiting flexible parental strategies. We show that these closely related populations express strikingly different ASRs, despite having similar ecologies and life histories, and that ASR variation is largely driven by sex differences in the apparent survival of juveniles. Furthermore, families in populations with biased ASRs were predominantly tended by a single parent, suggesting that parental cooperation breaks down with unbalanced sex ratios. Taken together, our results indicate that sex biases emerging during early life have profound consequences for social behaviour.
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http://dx.doi.org/10.1038/s41467-018-03833-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5917032PMC
April 2018

Willingness to initiate a fight but not contest behaviour depends on intruder size in Lethrus apterus (Geotrupidae).

Behav Processes 2018 Apr 8;149:65-71. Epub 2018 Feb 8.

Department of Ecology, University of Veterinary Medicine Budapest, Budapest, Hungary.

In resident-intruder contests, residents are expected to win more often than intruders unless the intruder has significantly higher competitive ability that is often determined by its size. Therefore, small intruders are expected to be less motivated to engage in contests than large ones and intruder size is predicted to have a positive relationship with the duration and escalation of the encounters. In a field experiment we tested these hypotheses in Lethrus apterus, a biparental beetle breeding in underground tunnels, by placing either a small or a large male in front of a tunnel occupied by a resident male. In agreement with our predictions residents won most of the encounters. Small intruders were less willing to engage in a contest and were less successful in their takeover attempts than large intruders. Contrary to many studies however, the duration and escalation (measured by the occurrence and latency of the different contest stages) of the fight in front of the burrow did not differ between the two intruder size categories. These findings suggest that in this species, small and large intruders adjust their prior decisions to their competitive abilities but once a fight started, they behave similarly during the contest.
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http://dx.doi.org/10.1016/j.beproc.2018.02.004DOI Listing
April 2018

Evaluation of potential reference genes for real-time qPCR analysis in a biparental beetle, (Coleoptera: Geotrupidae).

PeerJ 2017 28;5:e4047. Epub 2017 Nov 28.

Department of Evolutionary Zoology, University of Debrecen, Debrecen, Hungary.

Hormones play an important role in the regulation of physiological, developmental and behavioural processes. Many of these mechanisms in insects, however, are still not well understood. One way to investigate hormonal regulation is to analyse gene expression patterns of hormones and their receptors by real-time quantitative polymerase chain reaction (RT-qPCR). This method, however, requires stably expressed reference genes for normalisation. In the present study, we evaluated 11 candidate housekeeping genes as reference genes in samples of , an earth-boring beetle with biparental care, collected from a natural population. For identifying the most stable genes we used the following computational methods: geNorm, NormFinder, BestKeeper, comparative delta Ct method and RefFinder. Based on our results, the two body regions sampled (head and thorax) differ in which genes are most stably expressed. We identified two candidate reference genes for each region investigated: ribosomal protein L7A and RP18 in samples extracted from the head, and ribosomal protein L7A and RP4 extracted from the muscles of the thorax. Additionally, L7A and RP18 appear to be the best reference genes for normalisation in all samples irrespective of body region. These reference genes can be used to study the hormonal regulation of reproduction and parental care in in the future.
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http://dx.doi.org/10.7717/peerj.4047DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5710163PMC
November 2017

Candida albicans isolates from a single hospital show low phenotypical specialization.

J Basic Microbiol 2017 Nov 11;57(11):910-921. Epub 2017 Sep 11.

Faculty of Science and Technology, Department of Biotechnology and Microbiology, University of Debrecen, Debrecen, Hungary.

Candida albicans is the best-studied opportunistic human pathogenic yeast species, and its virulence factors, susceptibility to antimycotics, the diversity of its physiological properties and the determinative factors of these traits are interesting from a clinical as well as from an evolutionary perspective. By applying statistical modeling for the phenotypical differences observed among a collection of 63 C. albicans isolates originating from different clinical care units, from a diverse group of patients with or without mycosis, collected in a Hungarian clinic, we found that (i) host-related aspects like anatomical source, care unit of isolation, patients' age, sex, and disease severity, or ABC genotypes of the isolates had less effect on the phenotypic features of this opportunistic pathogen than host-independent aspects, for example, year or month of isolation; (ii) different phenotypic traits did not show any significant correlations with each other; and (iii) different genotypes displayed no anatomical specialization and rarely showed any significant correlation with parameters of isolation either. These results shed light on the dynamic nature and low specialization of the C. albicans populations observable in a narrow geographic range, namely in the patients hospitalized in the different care units of the clinic.
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http://dx.doi.org/10.1002/jobm.201700037DOI Listing
November 2017

Insulin/IGF Signaling and Life History Traits in Response to Food Availability and Perceived Density in the Cnidarian Hydra vulgaris.

Zoolog Sci 2017 Aug;34(4):318-325

1 MTA-DE "Lendület" Behavioral Ecology Research Group, Dept. of Evolutionary Zoology, University of Debrecen, 4032 Debrecen, Egyetem tér 1., Hungary.

Insulin/insulin-like growth factor signaling (IIS) is thought to be a central mediator of life history traits, but the generality of its role is not clear. Here, we investigated mRNA expression levels of three insulin-like peptide genes, the insulin-like receptor htk7, as well as several antioxidant genes, and the heat-shock protein hsp70 in the freshwater cnidarian Hydra vulgaris. Hydra polyps were exposed to a combination of different levels of food and perceived population density to manipulate life history traits (asexual reproduction and oxidative stress tolerance). We found that stress tolerance and the rate of asexual reproduction increased with food, and that these two effects were in significant interaction. Exposing animals to high perceived density resulted in increased stress tolerance or reduced reproduction only on lower food levels, but not on high food. The insulin-like receptor htk7 and the antioxidant gene catalase were significantly upregulated in the high density treatments. However, the expression level of insulin-like peptide genes, most antioxidant genes, and hsp70 were not affected by the experimental treatments. The higher expression level of htk7 may suggest that animals maintain a higher level of preparedness for insulin-like ligands at high population densities. However, the lack of difference between food levels suggests that IIS is not involved in regulating asexual reproduction and stress tolerance in hydra, or that its role is more subtle than a simple model of life history regulation would suggest.
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http://dx.doi.org/10.2108/zs160171DOI Listing
August 2017

Resource allocation and post-reproductive degeneration in the freshwater cnidarian Hydra oligactis (Pallas, 1766).

Zoology (Jena) 2017 02 23;120:110-116. Epub 2016 Jun 23.

MTA-DE "Lendület" Behavioral Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Egyetem tér 1, 4032 Debrecen, Hungary.

Freshwater hydra are among the few animal groups that show negligible senescence and can maintain high survival and reproduction rates when kept under stable conditions in the laboratory. Yet, one species of Hydra (H. oligactis) undergoes a senescence-like process in which polyps degenerate and die after sexual reproduction. The ultimate factors responsible for this phenomenon are unclear. High mortality in reproducing animals could be the consequence of increased allocation of resources to reproduction at the expense of somatic maintenance. This hypothesis predicts that patterns of reproduction and survival are influenced by resource availability. To test this prediction we investigated survival and reproduction at different levels of food availability in 10 lineages of H. oligactis derived from a single Hungarian population. Sexual reproduction was accompanied by reduced survival, but a substantial proportion of animals regenerated after sexual reproduction and continued reproducing asexually. Polyps belonging to different lineages showed differences in their propensity to initiate sexual reproduction, gonad number and survival rate. Food availability significantly affected fecundity (number of eggs or testes produced), with the largest number of gonads being produced by animals kept on a high food regime. On the other hand, survival rate was not affected by the amount of food. These results show that survival is conserved at the expense of reproduction in this population when food is low. It remains a question still to be answered why survival is prioritized over reproduction in this population.
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http://dx.doi.org/10.1016/j.zool.2016.06.009DOI Listing
February 2017

Individual variation behind the evolution of cooperation.

Authors:
Zoltán Barta

Philos Trans R Soc Lond B Biol Sci 2016 Feb;371(1687):20150087

MTA-DE 'Lendület' Behavioural Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Egyetem tér 1., Debrecen 4032, Hungary

Life on Earth has two remarkable properties. The first is variation: even apart from the vast number of extant species, there are considerable differences between individuals within a single species. The second property is cooperation. It is surprising that until recently the interactions between these two properties have rarely been addressed from an evolutionary point of view. Here, I concentrate on how inter-individual differences influence the evolution of cooperation. First, I deal with cases where individuality is maintained by random processes like mutation or phenotypic noise. Second, I examine when differences in state cause differences in behaviour. Finally, I investigate the effects of individual role specialization. Variation can be important in several ways. Increased random variation can change the expectation about cooperativeness of future partners, altering behaviour in a current relationship. Differences in state may serve as a book-keeping mechanism that is necessary for the evolution of reciprocity. If the cost of cooperation can depend on state then strategic regulation of state makes it possible to coerce partners to cooperate. If conditions force individuals to specialize, cooperation becomes more valuable. My review of theoretical models suggests that variation plays an important role in the evolution of cooperation.
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http://dx.doi.org/10.1098/rstb.2015.0087DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4760189PMC
February 2016

Personality and ectoparasitic mites (Hemipteroseius adleri) in firebugs (Pyrrhocoris apterus).

Behav Processes 2016 Jan 10;122:67-74. Epub 2015 Nov 10.

MTA-DE "Lendület" Behavioural Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Egyetem tér 1, 4010 Debrecen, Hungary.

Individuals of the same species often consistently differ in their behaviour across time and context. These stable differences are usually termed 'animal personality'. Parasitism is known to significantly influence the evolution of animal personality at least in part because more explorative individuals may meet parasites more frequently than less explorative ones. Previously, we have demonstrated that consistent individual differences (i.e. boldness, activity, exploration) can be measured in firebugs. As continuation, we examined here the relationship between firebug personality traits and their ectoparasitic mite loads in a wild population. We showed that bugs that behaved in a more explorative way have more mites and we also found a marginally significant interaction between sex, boldness and activity: bolder and more active female firebugs were more infected. In addition, we experimentally tested whether an artificial infection causes any alteration in the bug's behaviour and whether there is any relationship between firebug personality and immune response. This treatment did not induce any alteration in bugs' personality. We found that bugs become more explorative but less active when repeating the experiment, but at the same time all personality traits (boldness, activity and exploration) were repeatable. Furthermore, firebugs with a stronger immune response behaved more boldly but also less actively.
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http://dx.doi.org/10.1016/j.beproc.2015.11.011DOI Listing
January 2016

Predation on rose galls: parasitoids and predators determine gall size through directional selection.

PLoS One 2014 11;9(6):e99806. Epub 2014 Jun 11.

MTA-DE Biodiversity and Ecosystem Services Research Group, University of Debrecen, Debrecen, Hungary.

Both predators and parasitoids can have significant effects on species' life history traits, such as longevity or clutch size. In the case of gall inducers, sporadically there is evidence to suggest that both vertebrate predation and insect parasitoid attack may shape the optimal gall size. While the effects of parasitoids have been studied in detail, the influence of vertebrate predation is less well-investigated. To better understand this aspect of gall size evolution, we studied vertebrate predation on galls of Diplolepis rosae on rose (Rosa canina) shrubs. We measured predation frequency, predation incidence, and predation rate in a large-scale observational field study, as well as an experimental field study. Our combined results suggest that, similarly to parasitoids, vertebrate predation makes a considerable contribution to mortality of gall inducer larvae. On the other hand, its influence on gall size is in direct contrast to the effect of parasitoids, as frequency of vertebrate predation increases with gall size. This suggests that the balance between predation and parasitoid attack shapes the optimal size of D. rosae galls.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0099806PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4053394PMC
September 2015

Social role specialization promotes cooperation between parents.

Am Nat 2014 Jun 23;183(6):747-61. Epub 2014 Apr 23.

MTA-DE (Hungarian Academy of Sciences-University of Debrecen) "Lendület" Behavioural Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Egyetem tér 1, 4032 Debrecen, Hungary.

Biparental care of offspring is a widespread social behavior, and various ecological, life-history, and demographic factors have been proposed to explain its evolution and maintenance. Raising offspring generally requires several types of care (e.g., feeding, brooding, and defense), and males and females often specialize in providing different types of care. However, theoretical models of care often assume that care is a single variable and hence that a unit of care by the mother is interchangeable with a unit of care by the father. We hypothesize that the ability of one parent to provide all types of care may be limited by nonadditive costs or by sex-based asymmetries in the costs of particular care types. Using an individual-based simulation, we show that synergistic costs of investing in two tasks or negligible sex-based cost asymmetries select for task specialization and biparental care. Biparental care persists despite intense sexual selection and sex-biased mortality, suggesting that previous models make overly restrictive predictions of the conditions under which cooperation can be maintained. Our model provides a mechanistic underpinning for published models that show that the synergistic benefits of individuals cooperating can stabilize cooperation, both in the context of parental care and in other social scenarios.
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http://dx.doi.org/10.1086/676014DOI Listing
June 2014

Ventriculosubgaleal shunt in the treatment of posthemorrhagic and postinfectious hydrocephalus of premature infants.

Childs Nerv Syst 2013 Mar 4;29(3):413-8. Epub 2012 Dec 4.

Institute of Pediatrics, University of Debrecen Medical and Health Sciences Centre, Debrecen, Hungary.

Purpose: The aim of the study was to compare the characteristics of ventriculosubgaleal shunts during the clinical course of posthemorrhagic and postinfectious hydrocephalus in the neonatal period.

Patients And Methods: The study comprised 102 premature babies in whom subgaleal shunt was consecutively inserted between 2006 and 2011. Seventy-two patients had posthemorrhagic hydrocephalus (mean gestational age 27.3 ± 2.1 weeks, mean birth weight 1,036.9 ± 327.7 g, mean age at insertion 51.4 ± 56.2 days) and 30 patients were operated postinfectiously (27.5 ± 2.2 weeks, 1,064.7 g ± 310.7 g, 115.9 ± 47.8 days).

Results: The mean survival of subgaleal shunts was 87.9 days for the posthemorrhagic group and 75.6 days for the postinfectious group. Only six infants (8.3 %) did not need ventriculoperitoneal shunts later, all posthemorrhagic. There were meaningful differences between two groups with regard to ventriculosubgaleal shunt-related infections (8.3 % in posthemorrhagic versus 20.0 % in postinfectious) and shunt revision rate (6.9 % in posthemorrhagic versus 13.3 % in postinfectious), but these were not statistically significant. The need of ventriculoscopic procedures was notably more frequent in postinfectious group (1.4 versus 23.3 %).

Conclusion: In premature infants with ventriculomegaly, the subgaleal shunt is an effective temporary diversion tool. The complications were less with posthemorrhagic than with postinfectious hydrocephalus. With previous severe infections of prematures, the risk for complications regarding infection and obstruction will be 2.75 and 2.06 (odds ratios) times higher and more frequent need of ventriculoscopic procedures should be considered (odds ratio 21.6).
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http://dx.doi.org/10.1007/s00381-012-1968-5DOI Listing
March 2013

Haste makes waste but condition matters: molt rate-feather quality trade-off in a sedentary songbird.

PLoS One 2012 12;7(7):e40651. Epub 2012 Jul 12.

Department of Evolutionary Zoology, University of Debrecen, Debrecen, Hungary.

Background: The trade-off between current and residual reproductive values is central to life history theory, although the possible mechanisms underlying this trade-off are largely unknown. The 'molt constraint' hypothesis suggests that molt and plumage functionality are compromised by the preceding breeding event, yet this candidate mechanism remains insufficiently explored.

Methodology/principal Findings: The seasonal change in photoperiod was manipulated to accelerate the molt rate. This treatment simulates the case of naturally late-breeding birds. House sparrows Passer domesticus experiencing accelerated molt developed shorter flight feathers with more fault bars and body feathers with supposedly lower insulation capacity (i.e. shorter, smaller, with a higher barbule density and fewer plumulaceous barbs). However, the wing, tail and primary feather lengths were shorter in fast-molting birds if they had an inferior body condition, which has been largely overlooked in previous studies. The rachis width of flight feathers was not affected by the treatment, but it was still condition-dependent.

Conclusions/significance: This study shows that sedentary birds might face evolutionary costs because of the molt rate-feather quality conflict. This is the first study to experimentally demonstrate that (1) molt rate affects several aspects of body feathers as well as flight feathers and (2) the costly effects of rapid molt are condition-specific. We conclude that molt rate and its association with feather quality might be a major mediator of life history trade-offs. Our findings also suggest a novel advantage of early breeding, i.e. the facilitation of slower molt and the condition-dependent regulation of feather growth.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0040651PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3395693PMC
January 2013

Cues and the optimal timing of activities under environmental changes.

Ecol Lett 2011 Dec 20;14(12):1183-90. Epub 2011 Oct 20.

School of Mathematics, University of Bristol, UK.

Organisms time activities by using environmental cues to forecast the future availability of important resources. Presently, there is limited understanding of the relationships between cues and optimal timing, and especially about how this relationship will be affected by environmental changes. We develop a general model to explore the relation between a cue and the optimal timing of an important life history activity. The model quantifies the fitness loss for organisms failing to time behaviours optimally. We decompose the immediate change in fitness resulting from environmental changes into a component that is due to changes in the predictive power of the cue and a component that derives from the mismatch of the old response to the cue to the new environmental conditions. Our results show that consequences may range from negative, neutral to positive and are highly dependent on how cue and optimal timing and their relation are specifically affected by environmental changes.
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http://dx.doi.org/10.1111/j.1461-0248.2011.01686.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3258420PMC
December 2011

Consistent avoidance of human disturbance over large geographical distances by a migratory bird.

Biol Lett 2011 Dec 6;7(6):814-7. Epub 2011 May 6.

Department of Conservation Zoology, University of Debrecen, Debrecen, Hungary.

Recent work on animal personalities has demonstrated that individuals may show consistent behaviour across situations and contexts. These studies were often carried out in one location and/or during short time intervals. Many animals, however, migrate and spend their life in several geographically distinct locations, and they may either adopt behaviours specific to the local environment or keep consistent behaviours over ecologically distinct locations. Long-distance migratory species offer excellent opportunities to test whether the animals maintain their personalities over large geographical scale, although the practical difficulties associated with these studies have hampered such tests. Here, we demonstrate for the first time consistency in disturbance tolerance behaviour in a long-distance migratory bird, using the common crane Grus grus as an ecological model species. Cranes that hatched in undisturbed habitats in Finland choose undisturbed migratory stop-over sites in Hungary, 1300-2000 km away from their breeding ground. This is remarkable, because these sites are not only separated by large distances, they also differ ecologically: the breeding sites are wooded bogs and subarctic tundra, whereas the migratory stop-over sites are temperate zone alkaline grasslands. The significance of our study goes beyond evolutionary biology and behavioural ecology: local effects on behaviour may carry over large distances, and this hitherto hidden implication of habitat selection needs to be incorporated into conservation planning.
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http://dx.doi.org/10.1098/rsbl.2011.0295DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3210648PMC
December 2011

Haste makes waste: accelerated molt adversely affects the expression of melanin-based and depigmented plumage ornaments in house sparrows.

PLoS One 2010 Dec 3;5(12):e14215. Epub 2010 Dec 3.

Behavioural Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Debrecen, Hungary.

Background: Many animals display colorful signals in their integument which convey information about the quality of their bearer. Theoretically, these ornaments incur differential production and/or maintenance costs that enforce their honesty. However, the proximate mechanisms of production costs are poorly understood and contentious in cases of non-carotenoid-based plumage ornaments like the melanin-based badge and depigmented white wing-bar in house sparrows Passer domesticus. Costly life-history events are adaptively separated in time, thus, when reproduction is extended, the time available for molt is curtailed and, in turn, molt rate is accelerated.

Methodology/principal Findings: We experimentally accelerated the molt rate by shortening the photoperiod in order to test whether this environmental constraint is mirrored in the expression of plumage ornaments. Sparrows which had undergone an accelerated molt developed smaller badges and less bright wing-bars compared to conspecifics that molted at a natural rate being held at natural-like photoperiod. There was no difference in the brightness of the badge or the size of the wing-bar.

Conclusions/significance: These results indicate that the time available for molt and thus the rate at which molt occurs may constrain the expression of melanin-based and depigmented plumage advertisements. This mechanism may lead to the evolution of honest signaling if the onset of molt is condition-dependent through the timing of and/or trade-off between breeding and molt.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0014215PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2997061PMC
December 2010

Cooperation among non-relatives evolves by state-dependent generalized reciprocity.

Proc Biol Sci 2011 Mar 22;278(1707):843-8. Epub 2010 Sep 22.

Department of Evolutionary Zoology, University of Debrecen, Debrecen, Hungary.

For decades, attempts to understand cooperation between non-kin have generated substantial theoretical and empirical interest in the evolutionary mechanisms of reciprocal altruism. There is growing evidence that the cognitive limitations of animals can hinder direct and indirect reciprocity because the necessary mental capacity is costly. Here, we show that cooperation can evolve by generalized reciprocity (help anyone, if helped by someone) even in large groups, if individuals base their decision to cooperate on a state variable updated by the outcome of the last interaction with an anonymous partner. We demonstrate that this alternative mechanism emerges through small evolutionary steps under a wide range of conditions. Since this state-based generalized reciprocity works without advanced cognitive abilities it may help to understand the evolution of complex social behaviour in a wide range of organisms.
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http://dx.doi.org/10.1098/rspb.2010.1634DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3049049PMC
March 2011

Individual behaviour in firebugs (Pyrrhocoris apterus).

Proc Biol Sci 2011 Feb 8;278(1705):628-33. Epub 2010 Sep 8.

Behavioural Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Debrecen 4010, Hungary.

The concept of animal personalities has recently become of major interest as researchers began to wonder why animals within a given population show consistent behaviour across situations and contexts, what led to the evolution of such behavioural inflexibility and what mechanisms might underlie the phenomenon. A recent model explains individual differences in a population as the result of trade-off between present and future reproduction. We tested this model on the two wing morphs, i.e. short-winged (brachypterous) and long-winged (macropterous) specimens of the firebug (Pyrrhocoris apterus). Since it has been already demonstrated that the two wing morphs differ in their life-history strategies, this species is an ideal subject to test whether the specimens with different life-history strategies have different personalities as well. The results show that individuals behave consistently over time and across contexts, meaning observed bugs do have personalities. We also have found that in females, the two wing morphs have different personalities supporting the theoretical predictions, i.e. winged ones, which are supposed to have lower future reproductive value, are braver and more exploratory. We found no difference between the morphs in males. Differences in reproductive investment might explain this discrepancy between the sexes.
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http://dx.doi.org/10.1098/rspb.2010.1326DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3025677PMC
February 2011
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