[{"command":"openDialog","selector":"#drupal-modal","settings":null,"data":"\u003Cdiv id=\u0022republish_modal_form\u0022\u003E\u003Cform class=\u0022modal-form-example-modal-form ecl-form\u0022 data-drupal-selector=\u0022modal-form-example-modal-form\u0022 action=\u0022\/en\/article\/modal\/7204\u0022 method=\u0022post\u0022 id=\u0022modal-form-example-modal-form\u0022 accept-charset=\u0022UTF-8\u0022\u003E\u003Cp\u003EHorizon articles can be republished for free under the Creative Commons Attribution 4.0 International (CC BY 4.0) licence.\u003C\/p\u003E\n \u003Cp\u003EYou must give appropriate credit. We ask you to do this by:\u003Cbr \/\u003E\n 1) Using the original journalist\u0027s byline\u003Cbr \/\u003E\n 2) Linking back to our original story\u003Cbr \/\u003E\n 3) Using the following text in the footer: This article was originally published in \u003Ca href=\u0027#\u0027\u003EHorizon, the EU Research and Innovation magazine\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003ESee our full republication guidelines \u003Ca href=\u0027\/horizon-magazine\/republish-our-stories\u0027\u003Ehere\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003EHTML for this article, including the attribution and page view counter, is below:\u003C\/p\u003E\u003Cdiv class=\u0022js-form-item form-item js-form-type-textarea form-item-body-content js-form-item-body-content ecl-form-group ecl-form-group--text-area form-no-label ecl-u-mv-m\u0022\u003E\n \n\u003Cdiv\u003E\n \u003Ctextarea data-drupal-selector=\u0022edit-body-content\u0022 aria-describedby=\u0022edit-body-content--description\u0022 id=\u0022edit-body-content\u0022 name=\u0022body_content\u0022 rows=\u00225\u0022 cols=\u002260\u0022 class=\u0022form-textarea ecl-text-area\u0022\u003E\u003Ch2\u003EQ\u0026amp;A: The curious case of male pregnancy in seahorses and pipefishes\u003C\/h2\u003E\u003Cp\u003EShe is studying three of the different types of pregnancy in syngnathids, a fish family including seahorses, pipefish and seadragons as part of a project called \u003Ca href=\u0022https:\/\/cordis.europa.eu\/project\/id\/755659\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003EMALEPREG\u003C\/a\u003E. One type is when eggs are glued to the body of the male, who then carries them; the second is full male pregnancy, with transfer of nutrients and oxygen in a placenta-like system \u2013 including one in which a pouch closes with a skin fold upon egg deposition; and the third is similar to the second but with a closed pouch.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EBeyond the novelty value, what is so interesting about studying male pregnancy?\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u2018When it\u2019s a normal pregnancy system, egg production and pregnancy all intermingle with the mother, so it\u2019s very difficult to differentiate what happens during egg development and pregnancy.\u003C\/p\u003E\u003Cp\u003E\u2018(Another) reason is that when we want to understand the evolution of a trait, when we only have the absence or presence of this trait then it\u2019s very difficult to study how it has evolved. In syngnathids, what we have is that male pregnancy has evolved on a gradient \u2013 so we have closely related species that do display different forms.\u003C\/p\u003E\u003Cp\u003E\u2018If we compare those, then we can understand, \u201cOK, these genes have (provided) the function for this and this, and now this has happened\u201d.\u2019\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWhat exactly are you looking at?\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u2018One of the main issues we\u2019re studying is the problem of the immune system. If you accept a non-self embryo \u2013 because half is from the father and half from the mother \u2013 in your body, then your body would in principle (reject it). (So for pregnancy to evolve), somehow this rejection has to be circumvented.\u003C\/p\u003E\u003Cp\u003E\u2018In mammalians, (certain immune system) genes are downregulated (during pregnancy) \u2013 this is why we see that pregnant individuals are often sick. Then there are specific adaptations in the placenta that prevent the rejection of this non-self tissue. We are studying this in syngnathids.\u003C\/p\u003E\u003Cp\u003E\u2018We are doing a comparative genomics approach, so we have sequenced genomes of these different (syngnathid) forms. What we have found is that those genes are lost (in syngnathids with a part-closed pouch and changed in those with a closed one). So one arm of the immune system that\u2019s really important for vertebrates is (functionally) entirely lost.\u2019\u003C\/p\u003E\u003Cp\u003E\u003Cfigure role=\u0022group\u0022 class=\u0022@alignleft@\u0022\u003E\n\u003Cimg alt=\u0022While this male seahorse is not pregnant, when one is, it\u0027s hardly noticeable, according to Dr. Roth. Image credit - Sarah Kaehlert\u0022 height=\u00221296\u0022 src=\u0022\/research-and-innovation\/sites\/default\/files\/hm\/IMCEUpload\/male_seahorse.jpg\u0022 title=\u0022While this male seahorse is not pregnant, when one is, it\u0027s hardly noticeable, according to Dr. Roth. Image credit - Sarah Kaehlert\u0022 width=\u00221890\u0022\u003E\n\u003Cfigcaption class=\u0022tw-italic tw-mb-4\u0022\u003EWhile this male seahorse is not pregnant, when one is, it\u0027s hardly noticeable, according to Dr. Roth. Image credit - Sarah Kaehlert\u003C\/figcaption\u003E\n\u003C\/figure\u003E\n\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWhat are the implications of that finding?\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u2018Our hypothesis is that this has permitted the evolution of male pregnancy.\u003C\/p\u003E\u003Cp\u003E\u2018When we look at fishes, in general, the parental investment strategies are completely different from humans \u2013 males have a more important role. For the syngnathids, the problem is that they don\u2019t have a stomach, so they have to feed more or less permanently. They are always hunting food. So probably that\u2019s why they started to carry (their eggs) with them.\u003C\/p\u003E\u003Cp\u003E\u2018When we look at those species that are only carrying these embryos with them on the belly, those still have a (fully) functional immune system. Only with the evolution of this placenta-like structure \u2013 full male pregnancy \u2013 is this part of the immune system lost. Potentially, this (loss) has permitted this extreme evolution.\u003C\/p\u003E\u003Cp\u003E\u2018(Also), we have (here) a system that basically is immunologically deficient. (This) can ultimately help human medicine, because there are so many immunodeficiency diseases (such as HIV) and we are not able to cope with them. (It suggests that there\u2019s) a lot more flexibility in the adaptive immune system or in the evolution of adaptive immunity than we thought earlier.\u2019\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWhat else have you found so far?\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u2018We did transplant experiments to understand better this self\/non-self recognition. We transplanted fins (tissue) of the syngnathids to the belly of (themselves and others) to see if they rejected it or not and what we have found there is that those that have lost parts of their immune system are a lot better-accepting of non-self tissues.\u003C\/p\u003E\u003Cp\u003E\u2018We compared (syngnathid pregnancy) genes to the mammalian pregnancy genes, and we actually do find that these are genes from the very same pathways: similar genes have been co-opted in their function towards pregnancy.\u003C\/p\u003E\u003Cp\u003E\u2018(This) suggests that there are not probably so many options in what things have to be changed in their functions (to allow pregnancy). It doesn\u2019t really give us an idea of why (pregnancy) has evolved, but more that convergent evolution can come with a similar mechanistic basic.\u2019\u003C\/p\u003E\u003Cp\u003E\u003Cblockquote class=\u0022tw-text-center tw-text-blue tw-font-bold tw-text-2xl lg:tw-w-1\/2 tw-border-2 tw-border-blue tw-p-12 tw-my-8 lg:tw-m-12 lg:tw--ml-16 tw-float-left\u0022\u003E\n \u003Cspan class=\u0022tw-text-5xl tw-rotate-180\u0022\u003E\u201c\u003C\/span\u003E\n \u003Cp class=\u0022tw-font-serif tw-italic\u0022\u003E\u2018In syngnathids ... male pregnancy has evolved on a gradient.\u2019\u003C\/p\u003E\n \u003Cfooter\u003E\n \u003Ccite class=\u0022tw-not-italic tw-font-normal tw-text-sm tw-text-black\u0022\u003EDr Olivia Roth, GEOMAR, Germany\u003C\/cite\u003E\n \u003C\/footer\u003E\n\u003C\/blockquote\u003E\n\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWhat are you looking at next?\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u2018Now we know which genes might be involved (in the evolution of male pregnancy), but we don\u2019t know their function yet. The next step will be to (definitively) identify these.\u003C\/p\u003E\u003Cp\u003E\u2018Then we can study how (these genes) have evolved across the phylogeny (family tree of organisms) and see, for example, where there are mutations involved. We know that in (male) pregnancy they seem to have a role, but not if this is the same function as they have in female pregnancy.\u003C\/p\u003E\u003Cp\u003E\u2018We\u2019re (also) working on all the microbiota involved (in syngnathids\u2019 brood pouches). We\u2019ve cultivated these microbes and now we\u2019re going to deplete all the microbes on the male side and then add them again to see what their function is, to really understand this co-evolution of pregnancy with the immune system, but also with these microbes.\u003C\/p\u003E\u003Cp\u003E\u2018(With parts of the immune system lost, we\u2019re studying in addition) how is it possible that these fishes can survive and fight against diseases? And what kinds of compensatory mechanisms might they have?\u2019\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWhat wider lessons can we draw from studying male pregnancy in syngnathids?\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u2018In reproduction, I think we still (often) have the understanding that males are the ones giving the sperm and they don\u2019t then have a big function in parental investment. But we know now in terms of epigenetics (gene expression) that fathers are providing a lot more than just the sperm.\u003C\/p\u003E\u003Cp\u003E\u2018In the syngnathids, we really have the chance to see, \u201cOK, the males have this and this function\u201d. There are so many classical perceptions about how males have to behave and how females have to behave, (but it may not always be the case). We should really go beyond model systems. When we are driven to go and look at these weird creatures, we can (better) understand nature.\u2019\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThe research in this article was funded by the European Research Council. 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