Pregnant male seahorses support up to 1,000 growing babies by forming a placenta


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Jessica Suzanne Dudley, Macquarie University and Camilla Whittington, University of SydneySupplying oxygen to their growing offspring and removing carbon dioxide is a major challenge for every pregnant animal. Humans deal with this problem by developing a placenta, but in seahorses — where the male, not the female, gestates and gives birth to the young — exactly how it worked hasn’t always been so clear.

Male seahorses incubate their embryos inside a pouch, and until now it was unclear how the embryos “breathe” inside this closed structure. Our new study, published in the journal Placenta, examines how pregnant male seahorses (Hippocampus abdominalis) provide oxygen supply and carbon dioxide removal to their embryos.

We examined male seahorse pouches under the microscope at different stages of pregnancy, and found they develop complex placental structures over time — in similar ways to human pregnancy.

Male pot-bellied seahorses have large fleshy pouches where embryos develop during pregnancy.
by Aaron Gustafson



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A pregnant dad gestating up to 1,000 babies

Male pregnancy is rare, only occurring in a group of fish that includes seahorses, seadragons, pipehorses and pipefishes.

Pot-bellied seahorse males have a specialised enclosed structure on their tail. This organ is called the brood pouch, in which the embryos develop.

The female deposits eggs into the male’s pouch after a mating dance and pregnancy lasts about 30 days.

While inside the pouch, the male supplies nutrients to his developing embryos, before giving birth to up to 1,000 babies.

Male pot-bellied seahorse filling his pouch with water in a mating display.
by Kymberlie R. McGuire

Embryonic development requires oxygen, and the oxygen demand increases as the embryo grows. So too does the need to get rid of the resulting carbon dioxide efficiently. This presents a problem for the pregnant male seahorse.

Enter the placenta

In egg-laying animals — such as birds, monotremes, certain reptiles and fishes — the growing embryo accesses oxygen and gets rid of carbon dioxide through pores in the egg shell.

For animals that give birth to live young, a different solution is required. Pregnant humans develop a placenta, a complex organ connecting the mother to her developing baby, which allows an efficient exchange of oxygen and carbon dioxide (it also gets nutrients to the baby, and removes waste, via the bloodstream).

Placentae are filled with many small blood vessels and often there is a thinning of the tissue layers that separate the parent’s and baby’s blood circulations. This improves the efficiency of oxygen and nutrient delivery to the fetus.

Surprisingly, the placenta is not unique to mammals.

Some sharks, like the Australian sharpnose shark (Rhizoprionodon taylori) develop a placenta with an umbilical cord joining the mother to her babies during pregnancy. Many live-bearing lizards form a placenta (including very complex ones) to provide respiratory gases and some nutrients to their developing embryos.

Our previous research identified genes that allow the seahorse father to provide for the developing embryos while inside his pouch.

Our new study shows that during pregnancy the pouch undergoes many changes similar to those seen in mammalian pregnancy. We focused on examining the brood pouch of male seahorses during pregnancy to determine exactly how they provide oxygen to their developing embryos.

A Pot-belly seahorse (Hippocampus abdominalis) floats in water
By viewing the seahorse pouch under the microscope at various stages of pregnancy, we found that small blood vessels grow within the pouch.
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What we found

By viewing the seahorse pouch under the microscope at various stages of pregnancy, we found that small blood vessels grow within the pouch, particularly towards the end of pregnancy. This is when the baby seahorses (called fry) require the most oxygen.

The distance between the father’s blood supply and the embryos also decreases dramatically as the pregnancy goes on. These changes improve the efficiency of transport between the father and the embryos.

Interestingly, many of the changes that occur in the seahorse pouch during pregnancy are similar to those that occur in the uterus during mammalian pregnancy.

We have only scratched the surface of understanding the function of the seahorse placenta during pregnancy.

There is still much to learn about how these fathers protect and nourish their babies during pregnancy — but our work shows the morphological changes to seahorse brood pouches have a lot in common with the development of mammalian placentae.




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The Conversation


Jessica Suzanne Dudley, Postdoctoral Fellow, Macquarie University and Camilla Whittington, Senior lecturer, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Misogyny, male rage and the words men use to describe Greta Thunberg



Greta Thunberg departs after speaking at the youth climate strike in Battery Park, New York.
Peter Foley/EPA

Camilla Nelson, University of Notre Dame Australia and Meg Vertigan, University of Newcastle

Detractors have dismissed Swedish climate activist Greta Thunberg – a Nobel Prize nominee – as mentally ill, hysterical and a millennial weirdo after she pleaded with world officials last week to address the climate crisis.

Here, two researchers explain the stereotypical labels deployed by critics to undermine Thunberg’s call to action, which the activist herself has described as “too loud for people to handle”.

Camilla Nelson, Associate Professor in Media, University of Notre Dame

Greta Thunberg obviously scares some men silly. The bullying of the teenager by conservative middle-aged men has taken on a grim, almost hysterical edge. And some of them are reaching deep into the misogynist’s playbook to divert focus from her message.

It is not a rhetorical accident that critics of Thunberg, nearly 17, almost always call her a “child”. This infantilisation is invariably accompanied by accusations of emotionality, hysteria, mental disturbance, and an inability to think for herself – stereotypically feminine labels which are traditionally used to silence women’s public speech, and undermine their authority.

In Australia, Herald Sun columnist Andrew Bolt has called Thunberg “freakishly influential … with many mental disorders”. Sky News commentator Chris Kenny described her as a “hysterical teenager” who needs to be cared for.

Overseas, male commentators have used similar pejorative terms – describing her as a “mentally-ill Swedish child”, unstable and a “millenarian weirdo”. One claimed Thunberg needed a “spanking”; another likened her activism to “medieval witchcraft”.

Obviously these men find Thunberg triggering. But why?

Thunberg attends a Senate climate change taskforce press conference in Washington.
Shawn Thew/EPA



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At a deep level, the language of climate denialism is tied up with a form of masculine identity predicated on modern industrial capitalism – specifically, the Promethean idea of the conquest of nature by man, in a world especially made for men.

By attacking industrial capitalism, and its ethos of politics as usual, Thunberg is not only attacking the core beliefs and world view of certain sorts of men, but also their sense of masculine self-worth. Male rage is their knee-jerk response.

Thunberg did not try to be “nice” when she confronted world leaders at the United Nations last week. She did not defer or smile. She did not attempt to make anybody feel comfortable.

US President Donald Trump tweeted: “She seems like a very happy young girl looking forward to a bright and wonderful future. So nice to see!” Happiness here aligns itself with conformity, and an unspoken idea that women and children are expected to be docile and complacent.

But in reality, Thunberg is cutting through – rather than displaying – emotionalism. What certain kinds of men do not wish to acknowledge is that asking for action on climate change is entirely rational.




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Meg Vertigan, lecturer in English and writing and academic advisor at the University of Newcastle

As Greta Thunberg’s speech to the UN climate summit last week reverberates across the world, claims by critics over her mental state are alarming. Thunberg has described herself as having “Asperger’s”, an autism spectrum disorder, and describes it as her “superpower”.

But politicians and broadcasters appear to have confused the disorder with mental illness – a label used throughout history to label and potentially stigmatise “difficult” women who are told they need bed rest, medication or incarceration. Even today, doctors are more likely to diagnose women than men with depression, even when they present with identical symptoms.

Advocates for people with autism have pointed out the disorder is not linked to mental illness.

Yet commentator Andrew Bolt wrote of Thunberg, “I have never seen a girl so young and with so many mental disorders treated by so many adults as a guru”.

“She seems chronically attracted to apocalyptic visions, to fear,” he wrote, describing her as “chronically anxious and disturbed”.

Thunberg is ‘not the messiah, she is an extremely anxious girl’, Bolt says.

Not-for-profit organisation Beyond Blue defines anxiety as stress or worry which occurs “without any particular reason or cause”. Therefore by diagnosing Thunberg with anxiety, men are pathologising Thunberg’s concern about the environment and dismissing her fears as baseless and the result of mental illness.

History is littered with examples of this. Former Coalition minister George Brandis in 2015 famously called Labor frontbencher Penny Wong “shrill” and “hysterical” after she interjected during his Senate address – implying her comments were due to feminine mental instability.

So too, Australian Prime Minister Scott Morrison suggested climate change fears were a type of pathology. Following Thunberg’s UN speech he declared that the climate debate subjected children to “needless anxiety” and suggested they needed more “context and perspective” on the issue. “We’ve got to let kids be kids,” he said.

Here, Morrison is implying that Thunberg’s anxiety is somehow contagious. This is offensive to people with anxiety disorders – and offensive to passionate and vocal women.The Conversation

Camilla Nelson, Associate Professor in Media, University of Notre Dame Australia and Meg Vertigan, Lecturer in English and Writing/ Academic Advisor, University of Newcastle

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How birds become male or female, and occasionally both


Jenny Graves, La Trobe University

The highly unusual “semi-identical” Australian twins reported last week are the result of a rare event. It’s thought the brother and sister (who have identical genes from their mother but not their father) developed from an egg fertilised by two different sperm at the same moment.

In humans, it’s the sperm that determines whether an embryo is pushed along a male or female development pathway. But in birds, it’s the other way around. Eggs are the deciding factor in bird sex.




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There are other fascinating aspects of bird sex that are not shared with humans. Female birds seem to have some capacity to control the sex of their chicks. And occasionally a bird that is female on one side and male on the other is produced – as in recent reports of this cardinal in the United States.

A half-male, half-female cardinal was recently spotted in Pennsylvania.

X and Y, Z and W chromosomes

So what is it about bird chromosomes that makes bird sex so different from human sex?

In humans, cells in females have two copies of a large, gene-rich chromosome called X. Male cells have one X, and a tiny Y chromosome.




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Birds also have sex chromosomes, but they act in completely the opposite way. Male birds have two copies of a large, gene-rich chromosome called Z, and females have a single Z and a W chromosome. The tiny W chromosome is all that is left of an original Z, which degenerated over time, much like the human Y.

When cells in the bird ovary undergo the special kind of division (called “meiosis”) that produces eggs with just one set of chromosomes, each egg cell receives either a Z or a W.

Fertilisation with a sperm (all of which bear a Z) produces ZZ male or ZW female chicks.

Birds can control the sex of their chicks

We would expect that, during meiosis, random separation of Z and W should result in half the chicks being male and half female, but birds are tricky. Somehow the female is able to manipulate whether the Z or W chromosome gets into an egg.

Most bird species produce more males than females on average. Some birds, such as kestrels, produce different sex ratios at different times of the year and others respond to environmental conditions or the female’s body condition. For example, when times are tough for zebra finches, more females are produced. Some birds, such as the kookaburra, contrive usually to hatch a male chick first, then a female one.




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Why would a bird manipulate the sex of her chicks? We think she is optimising the likelihood of her offspring mating and rearing young (so ensuring the continuation of her genes into future generations).

It makes sense for females in poor condition to hatch more female chicks, because weak male chicks are unlikely to surmount the rigours of courtship and reproduction.

How does the female do it? There is some evidence she can bias the sex ratio by controlling hormones, particularly progesterone.

How male and female birds develop

In humans, we know it’s a gene on the Y chromosome called SRY that kickstarts the development of a testis in the embryo. The embryonic testis makes testosterone, and testosterone pushes the development of male characteristics like genitals, hair and voice.

But in birds a completely different gene (called DMRT1) on the Z but not the W seems to determine sex of an embryo.

In a ZZ embryo, the two copies of DMRT1 induce a ridge of cells (the gonad precursor) to develop into a testis, which produces testosterone; a male bird develops. In a ZW female embryo, the single copy of DMRT1 permits the gonad to develop into an ovary, which makes estrogen and other related hormones; a female bird results.

This kind of sex determination is known as “gene dosage”.

It’s the difference in the number of sex genes that determines sex. Surprisingly, this mechanism is more common in vertebrates than the familiar mammalian system (in which the presence or absence of a Y chromosome bearing the SRY gene determines sex).

Unlike mammals, we never see birds with differences in Z and W chromosome number; there seems to be no bird equivalent to XO women with just a single X chromosome, and men with XXY chromosomes. It may be that such changes are lethal in birds.

Birds that are half-male, half-female

Very occasionally a bird is found with one side male, the other female. The recently sighted cardinal has red male plumage on the right, and beige (female) feathers on the left.

One famous chicken is male on the right and female on the left, with spectacular differences in plumage, comb and fatness.

The most likely origin of such rare mixed animals (called “chimaeras”) is from fusion of separate ZZ and ZW embryos, or from double fertilisation of an abnormal ZW egg.

But why is there such clear 50:50 physical demarcation in half-and-half birds? The protein produced by the sex determining gene DMRT1, as well as sex hormones, travels around the body in the blood so should affect both sides.




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There must be another biological pathway, something else on sex chromosomes that fixes sex in the two sides of the body and interprets the same genetic and hormone signals differently.

What genes specify sex differences birds?

Birds may show spectacular sex differences in appearance (such as size, plumage, colour) and behaviour (such as singing). Think of the peacock’s splendid tail, much admired by drab peahens.

You might think the Z chromosome would be a good place for exorbitant male colour genes, and that the W would be a handy place for egg genes. But the W chromosome seems to have no specifically female genes.

Studies of the whole peacock genome show that the genes responsible for the spectacular tail feathers are scattered all over the genome. So they are probably regulated by male and female hormones, and only indirectly the result of sex chromosomes.The Conversation

Jenny Graves, Distinguished Professor of Genetics, La Trobe University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

CROCODILE ATTACK: HUMAN REMAINS FOUND IN CROCODILE


A 4.3m long crocodile has been caught and tested following the disappearance of Arthur Booker in the Endeavour River near Cooktown (Queensland, Australia) two weeks ago. Male human remains have been found within the crocodile and police have been notified of the find. DNA tests are now to be carried out to confirm the identity of the human remains, though it is more than likely to be those of Arthur Booker.