Male Seahorses Act Like Pregnant Mammals Study Suggests

Pregnant male seahorses tend to develop embryos similarly to the way mammals do, new research shows.

In the new study, scientists found a suite of genes that are “turned on” in the pouches of seahorses to keep the baby healthy and growing. Similar gene activity has been found in the wombs of mammals and even reptiles.

As such, the finding could shed light on the evolution of live birth, called viviparity.

Seahorse broods

Seahorses are syngnathid fishes — the only animal family in which males, not females, carry their young. In seahorse sex, the female deposits her eggs into a “brood pouch” on the male’s stomach, where he fertilizes them. The expectant dad then carries the eggs in this pouch during the 24-day gestation period until he gives birth, using abdominal contractions to expel the live young, which are then on their own to survive. [The 10 Wildest Pregnancies in the Animal Kingdom]

Previously, researchers knew little about what took place in the brood pouch of the pot-bellied seahorse (Hippocampus abdominalis) during pregnancy. To find out, an international team of researchers looked at how genes were turned on and off during the course of the expecting dads’ pregnancies. They compared this activity with that found in the brood pouches of nonpregnant males. (Just as nonpregnant women have uteruses, nonpregnant male seahorses have brood pouches.)

They specifically looked at ribonucleic acid, or RNA in the seahorses’ brood pouches  (RNA is produced when a gene is turned on and tells the cell to build the protein that the gene encodes.) Then, they looked for similar gene sequences (and their functions) in publicly available databases.

Pouches and uteruses

Pregnancy led to an uptick in the expression of genes involved in nutrient transport within the brood pouch, the scientists found. “Things like fats, and also calcium, seem to be transported from the dad [to the developing fetus],” said study author Camilla M. Whittington, a postdoctoral researcher at the University of Sydney in Australia. “We also found a whole lot of other genes for things like immune function, so it looks like the seahorse dads can actually help prevent infection in the brood pouch.”

The researchers also found changes in the expression of genes involved in tissue remodeling. These genes may be involved in structural changes to the brood pouch, which thickens and develops more blood vessels when carrying the brood (of several hundred embryos), Whittington said. The team found gene-expression changes associated with immune-system activities (both protecting the embryos from infection and preventing the father’s immune system from rejecting the tissue of his offspring as foreign), gas exchange (so that the embryo can “breathe”), and waste removal.

The brood pouch is said to have the same function as the uterus of mammals and reptiles. Consistent with that idea, the researchers found many similarities between the genes expressed in the male seahorses’ brood pouches and similar genes (called homologues) expressed in the uteruses of female mammals — rats, in particular — and the womb equivalents of reptiles and fish that have live young. Those similarities could potentiality extend to humans, Whittington said. [Infographic: For How Long Are Animals Pregnant?]

“People have looked at gene expression in the rat uterus during pregnancy, whereas we don’t have a similar data set for humans,” Whittington said. “Obviously, it’s kind of difficult to get those kinds of tissue samples, and that’s probably why people haven’t done it. So we found mammalian homologues, and we presume some of them will be human homologues, too, but we don’t have the data to be able to tell.”

Bearing live young

Research of this sort may reveal details about how viviparity evolved, Whittington said. The trait is thought to have evolved independently 150 times in vertebrates, including 23 times in fishes, the authors wrote in the study.

Once animals “stop laying eggs and start having live babies instead, animals are faced with a common set of challenges,” Whittington said. “Somehow, wastes have to be removed from the embryo, somehow oxygen has to be delivered and somehow nutrients have to be delivered.

“There are perhaps a limited number of genetic ways that this could be done, and so this is why we’re seeing the same genes being recruited into pregnancy in these animals,” Whittington added.

This process of turning on certain genes during pregnancy could be an example of convergent evolution, in which evolutionarily separated species develop similar ways of doing things by evolving under similar environmental conditions.

“These animals have evolved pregnancy millions of years apart and also in completely different structures,” Whittington added. This supports the convergent evolution idea. “Mammals use a uterus, whereas the seahorses are using, essentially, modified abdominal skin,” Whittington said.

Alternatively, viviparous animals around today could have had a common ancestor in which these genes were already turned on in the tissues that later evolved to become the uterus and the brood pouch.

“I think our research shows that we are more like other animals than you might think,” Whittington added. “I think it really illustrates that there are commonalities in pregnancies across really diverse vertebrates, and I think that’s really exciting.”

California’s Killer Bees Are Spreading North

Bad news for apiphobes: “Killer” bees are on the move in the United States.

Scientists from the University of California, San Diego recently collected hundreds of bees around the Golden State to determine how far north hybrid honeybees, or Africanized bees, have spread since they first arrived in the state in 1994.

They found that Africanized bees — which possess genes from both European and African honeybees — now live as far north as California’s delta region (about 25 miles, or 40 kilometers, south of Sacramento). And in the southern part of the state, so-called “killer” bees run the show. About 65 percent of the honeybeesthat buzz around San Diego County have a mix of European and African genes, the researchers found. [No Creepy Crawlies Here: Gallery of the Cutest Bugs]

“The pattern of Africanization we documented in San Diego County and elsewhere in California appears consistent with patterns previously documented in Texas, where Africanized honey bees first appeared in the United States,” Joshua Kohn, a professor of biology at UC San Diego and co-author of the new study, said in a statement.

While Africanized bees have taken up residence throughout the American South, Southwest, Southeast and Western coastal regions, their ability to set up permanent colonies in the northern parts of the country seems to be limited by cold temperatures during the winter months, Kohn said. However, higher temperatures caused by global warming could mean that killer bees may continue to push north in the coming years, he added.

There are a few reasons why the range of Africanized bees in California and other states is important, Kohn told Live Science. For one, these bees are highly aggressive, he said. People in California, Arizona and Texas (as well as several other states) have been seriously injured or killedafter enduring thousands of stings from Africanized bees, which are quick to defend their hives. Knowing where those hives might be is a good starting point for preventing future attacks, Kohn said.

But scientists don’t just want to track the migration of Africanized bees because of their killer instincts. Kohn and Yoshiaki Kono, a graduate student in UC San Diego’s Department of Biological Sciences and lead author of the new bee study, are also curious about the spread of the Africanized bees’ more desirable qualities, such as their resistance to some of the diseases and mites that are killing off honey bees in other parts of the country, Kohn said.

The flight of the honeybee

The story of killer bees started in the 1950s. In an effort to breed honeybees better suited to South America’s tropical climate, a biologist in Brazil imported a subspecies of bee (Apis mellifera scutellata) from southern Africa to interbreed with bees from Europe. But winged insects are hard to contain, and several swarms of African bees escaped into the wild.

The runaway bees bred with local populations of European honeybees, and their hybrid descendants spread, mating with other European bees along the way. This intermingling of the African and European honeybees’ gene pools is known as Africanization because it’s the African genes that generally prevail, according to Kohn. The typical Africanized bee in California has a genome made up of 70 to 80 percent African genes and only 20 to 30 percent European genes, he added. [On the Hunt: Honeybee Scouts Find Food]

African genes, and the qualities they are associated with, are dominant because they are favored by natural selection, Kohn said. An Africanized bee’s slightly larger size and high reproduction rate give it certain advantages over non-Africanized bees, for example.

Africanized bees also appear to be more resistant to certain diseases and parasites compared to European bees, Kohn said. In fact, there are many studies that back up this claim. One study, published in 2010 in the journal Experimental and Applied Acarology, found that Africanized bees may be more resistant to the parasitic mite Varroa destructor (an insidious foe inside bee colonies) because of the bees’ grooming behaviors and the lowered fertility of the mites inside the brood, or honeycomb of the Africanized hive.

Right now, most of California’s Africanized bees are feral — the study found that only 13 percent of managed hives in San Diego County carried the African mitotype (mitochondrial DNA), as opposed to 70 percent of feral hives in the county. Most beekeepers prefer European honeybees because Africanized bees are so much more difficult to manage, Kohn said.

But, there may be a way for beekeepers to get the disease resistance they’re looking for in European bees while minimizing the risk that Africanized bees pose.

“By dissecting the genomes of Africanized honey bees to find regions responsible for advantageous traits, we may be able to combat recent declines in managed honey bee populations that are so critical for food production,” Kohn said.

Disease-resistant bees that aren’t likely to kill anyone could be a win-win for everyone.

How Armored Dinosaur Got Its Bone-Bashing Tail

Armored, squat, and built like a tank, ankylosaurs were a type of dinosaur known for their bony, protective exterior and distinct, sledgehammer-shaped tails. Now, scientists have pieced together how the animals’ rear-end weapons evolved, finding that the hammer’s “handle” came first.

Ankylosaurs were a group of bulky, tanklike dinosaurs with bony plates covering much of their bodies. Some of these animals — a subgroup known as ankylosaurids — also came equipped with a weaponized tail club as well.

“Ankylosaur tail clubs are made of two parts of the body,” said study lead author Victoria Arbour, a postdoctoral researcher in the Department of Biological Sciences at North Carolina State University and the North Carolina Museum of Natural Sciences. “They’re made of the bones of the tail — the vertebrae — that change so that they’re stiff and lock together in a really characteristic way. We call that the handle, like the handle of an ax. And the other part of the tail is the knob.” [Paleo-Art: Dinos Come to Life in Stunning Illustrations]