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Hotzy, Cosima
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Publications (7 of 7) Show all publications
Hermans Née Hotzy, C. (2017). Selection in sperm and its consequences: Exploring haploid selection, ageing and epigenetic effects in sperm. (Doctoral dissertation). Uppsala: Acta Universitatis Upsaliensis
Open this publication in new window or tab >>Selection in sperm and its consequences: Exploring haploid selection, ageing and epigenetic effects in sperm
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Sexually reproducing eukaryotes are typically going through a biphasic life cycle with a diploid and a haploid phase. Unlike in plants where selection on haploid pollen genotypes is well established, the possibility of selection occurring in animal sperm is currently not known. One of the main reasons for this lack of knowledge is the general assumption that due to the shortness and the apparent absence of gene expression in haploid sperm, selection during that phase is unlikely to occur. The aim of this thesis was to fill this gap and address some of the main fundamental questions. I investigated the interaction between sperm phenotype and offspring phenotype with a focus on the trans-generational effects of (i) selection on the haploid sperm genotype, (ii) sperm ageing and (iii) sperm-mediated epigenetic effects. For one, we performed several experimental studies to investigate how selection on the sperm phenotype affects offspring performance in two externally fertilizing fishes, Atlantic salmon and zebrafish. We found that in Atlantic salmon, sperm of intermediate post-activation longevity sire offspring that hatch earlier. In zebrafish, longer living sperm sire more viable offspring with a higher fitness than their short-lived sibling sperm. We explored the mechanisms of these trans-generational effects and found that neither intrinsic post-ejaculation sperm ageing (Atlantic salmon and zebrafish) nor pre-ejaculation sperm ageing (zebrafish) affect offspring performance. However, we identified genetic differences between sperm pools that were obtained by selecting different phenotypes within ejaculates of zebrafish males. These results suggest a genetic basis for intra-ejaculate sperm phenotype variation and show that there is potential for haploid selection in sperm. In a separate experiment, we explored the role of sexual selection in shaping sperm-mediated epigenetic effects, and found that short-time changes in male-male competition affect offspring hatching time and survival. In conclusion, this thesis provides evidence that sperm phenotype affects offspring phenotype, and that sperm phenotype is affected by both epigenetic changes influenced by the male environment and differences in the haploid genome of sperm.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. p. 57
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1518
Keywords
sperm, evolution, selection, haploid selection, epigenetics, sperm-mediated effects, trans-generational effects, sperm ageing, sperm senescence
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-320437 (URN)978-91-554-9918-1 (ISBN)
Public defence
2017-06-09, Lindahlsalen, Evolutionary Biology Centre, EBC, Norbyvägen 14, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2017-05-18 Created: 2017-04-20 Last updated: 2017-06-07
Arnqvist, G., Sayadi, A., Immonen, E., Hotzy, C., Rankin, D., Tuda, M., . . . Johnston, J. S. (2015). Genome size correlates with reproductive fitness in seed beetles. Proceedings of the Royal Society of London. Biological Sciences, 282(1815), Article ID 20151421.
Open this publication in new window or tab >>Genome size correlates with reproductive fitness in seed beetles
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2015 (English)In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 282, no 1815, article id 20151421Article in journal (Refereed) Published
Abstract [en]

The ultimate cause of genome size (GS) evolution in eukaryotes remains a major and unresolved puzzle in evolutionary biology. Large-scale comparative studies have failed to find consistent correlations between GS and organismal properties, resulting in the 'C-value paradox'. Current hypotheses for the evolution of GS are based either on the balance between mutational events and drift or on natural selection acting upon standing genetic variation in GS. It is, however, currently very difficult to evaluate the role of selection because within-species studies that relate variation in life-history traits to variation in GS are very rare. Here, we report phylogenetic comparative analyses of GS evolution in seed beetles at two distinct taxonomic scales, which combines replicated estimation of GS with experimental assays of life-history traits and reproductive fitness. GS showed rapid and bidirectional evolution across species, but did not show correlated evolution with any of several indices of the relative importance of genetic drift. Within a single species, GS varied by 4-5% across populations and showed positive correlated evolution with independent estimates of male and female reproductive fitness. Collectively, the phylogenetic pattern of GS diversification across and within species in conjunction with the pattern of correlated evolution between GS and fitness provide novel support for the tenet that natural selection plays a key role in shaping GS evolution.

Keywords
selfish DNA, Callosobruchus maculatus, population size, sexual dimorphism, sex chromosomes, sperm competition
National Category
Genetics Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-267333 (URN)10.1098/rspb.2015.1421 (DOI)000363357100013 ()
Funder
EU, European Research Council, AdG-294333Swedish Research Council, 621-2010-5266
Available from: 2015-11-24 Created: 2015-11-20 Last updated: 2018-08-10Bibliographically approved
Zajitschek, S., Hotzy, C., Zajitschek, F. & Immler, S. (2014). Short-term variation in sperm competition causes sperm-mediated epigenetic effects on early offspring performance in the zebrafish. Proceedings of the Royal Society of London. Biological Sciences, 281(1785), 20140422
Open this publication in new window or tab >>Short-term variation in sperm competition causes sperm-mediated epigenetic effects on early offspring performance in the zebrafish
2014 (English)In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 281, no 1785, p. 20140422-Article in journal (Refereed) Published
Abstract [en]

The inheritance of non-genetic factors is increasingly seen to play a major role in ecology and evolution. While the causes and consequences of epigenetic effects transmitted from the mother to the offspring have received ample attention, much less is known about how variation in the condition of the father affects the offspring. Here, we manipulated the intensity of sperm competition experienced by male zebrafish Danio rerio to investigate the potential for sperm-mediated epigenetic effects over a relatively short period of time. We found that the rapid responses of males to varying intensity of sperm competition not only affected sperm traits as shown previously, but also the performance of the resulting offspring. We observed that males exposed to high intensity of sperm competition produced faster swimming and more motile sperm, and sired offspring that hatched over a narrower time frame but exhibited a lower survival rate than males exposed to low intensity of sperm competition. Our results provide striking evidence for short-term paternal effects and the possible fitness consequences of such sperm-mediated non-genetic factors not only for the resulting offspring but also for the female.

Keywords
paternal effects, epigenetic inheritance, social environment, offspring survival, larval hatching, Danio rerio
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-227694 (URN)10.1098/rspb.2014.0422 (DOI)000335812100023 ()
Available from: 2014-07-01 Created: 2014-06-30 Last updated: 2017-12-05Bibliographically approved
Immler, S., Hotzy, C., Alavioon, G., Petersson, E. & Arnqvist, G. (2014). Sperm variation within a single ejaculate affects offspring development in Atlantic salmon. Biology Letters, 10(2), 20131040
Open this publication in new window or tab >>Sperm variation within a single ejaculate affects offspring development in Atlantic salmon
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2014 (English)In: Biology Letters, ISSN 1744-9561, E-ISSN 1744-957X, Vol. 10, no 2, p. 20131040-Article in journal (Refereed) Published
Abstract [en]

It is generally believed that variation in sperm phenotype within a single ejaculate has no consequences for offspring performance, because sperm phenotypes are thought not to reflect sperm genotypes. We show that variation in individual sperm function within an ejaculate affects the performance of the resulting offspring in the Atlantic salmon Salmo salar. We experimentally manipulated the time between sperm activation and fertilization in order to select for sperm cohorts differing in longevity within single ejaculates of wild caught male salmon. We found that within-ejaculate variation in sperm longevity significantly affected offspring development and hence time until hatching. Whether these effects have a genetic or epigenetic basis needs to be further evaluated. However, our results provide experimental evidence for transgenerational effects of individual sperm function.

Keywords
gamete selection, epigenetics, haploid selection, sperm competition, fish
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-222203 (URN)10.1098/rsbl.2013.1040 (DOI)000332378300009 ()
Available from: 2014-04-09 Created: 2014-04-08 Last updated: 2017-12-05Bibliographically approved
Ronn, J. L. & Hotzy, C. (2012). Do longer genital spines in male seed beetles function as better anchors during mating?. Animal Behaviour, 83(1), 75-79
Open this publication in new window or tab >>Do longer genital spines in male seed beetles function as better anchors during mating?
2012 (English)In: Animal Behaviour, ISSN 0003-3472, E-ISSN 1095-8282, Vol. 83, no 1, p. 75-79Article in journal (Refereed) Published
Abstract [en]

In a wide variety of taxa, males are equipped with harmful structures on their genitalia such as hooks, barbs or spines. The proximate function of these structures and the evolutionary forces behind their evolution have been discussed and investigated during the last few decades. One model system in which these structures have attracted particular attention is the Callosobruchus seed beetle group. The main suggestion for the occurrence of genital spines in this group of species has been that their primary function is to act as an anchor during mating, to aid the male in staying attached to the female. This would prevent females terminating copulation prematurely, or would hinder take-overs by rival males. We used five populations of Callosobruchus seed beetles, with differing lengths of the male genital spines, to test whether longer spines provide males with an enhanced attachment during mating. This was tested both with and without male competition in the form of rival males present or not during focal copulations. We found that males from populations with longer spines did not stay in copula for longer than males from populations with shorter spines. In addition, females mating with males with longer genital spines suffered a fitness cost in terms of lower lifetime offspring production. In conclusion, we did not find any support for the hypothesis that the primary function of genital spines in seed beetles is to serve as an anchor. (C) 2011 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Keywords
adaptive harm hypothesis, Callosobruchus, fitness, genital spine, male-male competition, mating duration, pleiotropic harm hypothesis, postmating sexual selection, sexual conflict
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-168596 (URN)10.1016/j.anbehav.2011.10.007 (DOI)000298149900012 ()
Available from: 2012-02-14 Created: 2012-02-13 Last updated: 2017-12-07Bibliographically approved
Hotzy, C., Polak, M., Rönn, J. L. & Arnqvist, G. (2012). Phenotypic Engineering Unveils the Function of Genital Morphology. Current Biology, 22(23), 2258-2261
Open this publication in new window or tab >>Phenotypic Engineering Unveils the Function of Genital Morphology
2012 (English)In: Current Biology, ISSN 0960-9822, E-ISSN 1879-0445, Vol. 22, no 23, p. 2258-2261Article in journal (Refereed) Published
Abstract [en]

The rapidly evolving and often extraordinarily complex appearance of male genital morphology of internally fertilizing animals has been recognized for centuries [1]. Postcopulatory sexual selection is regarded as the likely evolutionary engine of this diversity [2], but direct support for this hypothesis is limited. We used two complementary approaches, evolution through artificial selection and microscale laser surgery, to experimentally manipulate genital morphology in an insect model system. We then assessed the competitive fertilization success of these phenotypically manipulated males and studied the fate of their ejaculate in females using high-resolution radioisotopic labeling of ejaculates. Males with longer genital spines were more successful in gaining fertilizations, providing experimental evidence that male genital morphology influences success in postcopulatory reproductive competition. Furthermore, a larger proportion of the ejaculate moved from the reproductive tract into the female body following mating with males with longer spines, suggesting that genital spines increase the rate at which seminal fluid passes into the female hemolymph. Our results show that genital morphology affects male competitive fertilization success and imply that sexual selection on genital morphology may be mediated in part through seminal fluid [3].

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-191771 (URN)10.1016/j.cub.2012.10.009 (DOI)000312115300024 ()
Available from: 2013-01-15 Created: 2013-01-14 Last updated: 2017-12-06Bibliographically approved
Hotzy, C. & Arnqvist, G. (2009). Sperm Competition Favors Harmful Males in Seed Beetles. Current Biology, 19(5), 404-407
Open this publication in new window or tab >>Sperm Competition Favors Harmful Males in Seed Beetles
2009 (English)In: Current Biology, ISSN 0960-9822, E-ISSN 1879-0445, Vol. 19, no 5, p. 404-407Article in journal (Refereed) Published
Abstract [en]

One of the most enigmatic observations in evolutionary biology is the evolution of morphological or physiological traits in one sex that physically injure members of the other sex [1-3]. Such traits occur in a wide range of taxa [3] and range from toxic ejaculate substances [4-6] to genital or external spines that wound females during copulation [7-11]. Current hypotheses for the adaptive evolution of such injurious traits rest entirely on the assumption that they are beneficial to their bearer by aiding in reproductive competition [1, 3]. Here, we assess this key assumption in seed beetles where genital spines in males physically injure females. We demonstrate that male spine length is positively correlated with harm to females during mating but also that males with longer spines are more successful in sperm competition. This is the first complete support for the proposal that sexual selection by sperm competition can favor morphological traits in males that inflict injury upon females. However, our results suggest that harm to females is a pleiotropic by-product, such that genital spines in males elevate success in sperm competition by means other than by causing harm.

National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-129927 (URN)10.1016/j.cub.2009.01.045 (DOI)000264171100029 ()
Available from: 2010-08-26 Created: 2010-08-26 Last updated: 2017-12-12Bibliographically approved
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