For the pipefish (and their relatives, seahorses and sea dragons), it’s the males who get pregnant. After a male fertilises the female’s eggs, he takes them up into a special brood pouch and shelters them until the babies hatch from his pot-bellied stomach several weeks later. He may seem like a shoe-in for the Dad-of-the-year award but this fatherly commitment has a sinister side to it. Not all of the babies he cares for make it out of his stomach alive.
Gry Sagebakken from the University of Gothenburg has proved that pregnant male pipefishes absorb some of the eggs and embryos within their pouches. By secretly cannibalising a proportion of his brood, he gets an extra boost of nutrients. The young he carries around aren’t just his next of kin, they’re also ready-made snacks.
Previously, Ingrid Ahnesjo showed that male pipefish ‘give birth’ to fewer youngsters than expected. During his pregnancy, some embryos were clearly lost. To track the fate of these lost eggs, Ahnesjo and Sagebakken injected females with a mixture of mildly radioactive amino acids. These were incorporated into newly created proteins, including those within the female’s eggs. Males were allowed to mate with both normal and irradiated females, so that half of the eggs in their bellies were radioactive and half were not.
They found that some of the radioactivity ended up in the male’s own tissues, including his liver and his muscles. This was the answer to the mystery of the missing embryos – daddy absorbs them into their own flesh. The fact that his brood pouch is lined with tangled networks of blood vessels makes it easier to do this.
Others have suggested that the lost embryos are actually “nurse eggs”, laid specifically to feed their siblings and act as their first meal. But not according to Sagebakken’s experiments, which show no traces of radioactivite amino acids in the eggs that didn’t contain them in the first place. The babies weren’t absorbing their potential siblings.
Either way, this is a prime example of the sorts of conflicts that can arise between animal parents and their offspring. Humans may romanticise the role of fathers and mothers, but studies like this show that for many animals, their interests of parents and children are often not aligned.
Should a parent ensure their offspring’s survival at the cost of their own health, or their chance to raise another generation? Should a youngster make demands on its parents for its short-term gain at the expense of a lower quality of care in the future? It’s a fine balancing act, and one that leads many animal parents to thin the size of their broods, killing or even eating them.
These trade-offs depend on many things like the size of each generation, the quality of one’s partners, the number of babies, the health of the parents, and so on. Sagebakken’s next step is to see if the males cannibalise more of their brood if they’re hungrier, and if the survivors actually benefit from their siblings’ demise. She also wants to understand if the male pipefish actually kills some of his offspring or just recycles the nutrients from embryos that are already dead or dying.
Reference: Proceedings of the Royal Society B doi:10.1098/rspb.2009.1767
Image: from Wikipedia by Tewy
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Pregnant women are generally advised to avoid drinking alcohol and for good reason – exposing an unborn baby to alcohol can lead to a range of physical and mental problems from hyperactivity and learning problems to stunted growth, abnormal development of the head, and mental retardation.
But alcohol also has much subtler effects on a foetus. Some scientists have suggested that people who get their first taste of alcohol through their mother’s placenta are more likely to develop a taste for it in later life. This sleeper effect is a long-lasting one – exposure to alcohol in the womb has been linked to a higher risk of alcohol abuse at the much later age of 21. In this way, mums could be inadvertently passing down a liking for booze to their children as a pre-birthday present.
Now, Steven Youngentob from SUNY Upstate Medical University and Jon Glendinning from Columbia University have found out why this happens. By looking at boozing rats, they have found that those first foetal sips of alcohol make the demon drink both taste and smell better.
The duo raised several pregnant rats on diets of either chow, liquids or liquids that had been spiked with alcohol. The third group eventually had a blood alcohol concentration of about 0.15%, a level that would cause a typical human to slur, stagger or become moody.
When the females eventually gave birth, month-old pups born to boozy mothers were more likely to lick an alcohol-coated feeding tube than those whose mothers were tee-total. These rats had been born with more of a taste for booze.
Our health isn’t just affected by the things we do after we’re born – the conditions we face inside our mother’s womb can have a lasting impact on our wellbeing, much later in life. This message comes from a growing number of studies that compare a mother’s behaviour during pregnancy to the subsequent health of her child.
But all of these studies have a problem. Mothers also pass on half of their genes to their children, and it’s very difficult to say which aspects of the child’s health are affected by conditions in the womb, and which are influenced by mum’s genetic legacy.
Take the case of smoking. Doing it while pregnant is bad news for the foetus, and studies have suggested that children whose mothers smoke during pregnancy are more likely to be born prematurely, be born lighter, have poorer lung function, and be more likely to die suddenly before their first birthday. More controversially, they may even show higher levels of behavioural problems including autistic disorders and antisocial tendencies.
Biologically, these results make sense, but many of these risks can be inherited too. For example, genetic factors can strongly influence both a person’s susceptibility to nicotine addiction and their propensity for violent behaviour. A mother’s genes could also affect the birth weight of her child.
To untangle these influences, the ideal experiment would involve randomly implanting foetuses either in the wombs of their own mothers, or those of unrelated women. That’s possible in animals but deliberately doing so in humans would be both unethical and impractical. Nonetheless, Frances Rice from Cardiff University realised that this experiment was actually well underway.
Since the advent of in vitro fertilisation (IVF) technology in the late 1970s, many mothers have nourished babies in their womb, who weren’t genetically related to them. Here was an ideal chance to study the effects of conditions in the womb, without any confusion caused by shared genes.