Meet your distant relative, Entelognathus primordialis, possibly the first earthling with a face. Or at least a familiar face.

Entelognathus primordialis (where Entelognathus means “complete jaw”) is described this week in Nature. Discovered in a quarry in China, the remarkably well-preserved fossil is somewhat 3D, displaying a modern type of jaw.

E. primordialis is a placoderm, an early class of fish that lived 430 to 360 million years ago. These fish were covered with an armor of bony plates and gave rise to two later groups—bony fish and cartilaginous fish.

The evolution of jaws is one of the key episodes in the evolution of vertebrates, but the gap between jawed and jawless vertebrates is so large that it has been hard to work out the individual evolutionary steps in the transition. Min Zhu and his colleagues hope to make the link with E. primordialis.

The 419 million-year-old fish fossil has jawbone features previously restricted to bony fishes, but has the full body armor seen in placoderms. It would have been around 20 centimeters (eight inches) long.

Prior to this recent find, most scientists agreed that placoderms had no jaw and were more similar to the cartilaginous fish, like modern day sharks, while the bony fishes are believed to be our ancestors. According to Nature News:

Such fishes went on to dominate the seas and ultimately gave rise to land vertebrates.

In addition to facing off with placoderms, the new study puts cartilaginous fishes into a whole new light—perhaps they are even more evolved than previously thought.

What’s going on with the oceans and what can we do?

As carbon dioxide (CO₂) rises in our atmosphere, the oceans absorb roughly a quarter of the amount. This lowers the pH level in the seawater, making the oceans more acidic. How this affects life in and out of the sea is continually studied.

This week, ocean acidification is the topic of several scientific papers. We thought we’d highlight a few of them here.

Nature Climate Change has two papers—one about the affect of acidification on several different species, and the other on how ocean acidification causes even more global warming.

For the first paper, German researchers surveyed previous studies that dealt with the consequences of ocean acidification for marine species from five animal taxa: corals, crustaceans, mollusks, fish, and echinoderms. By the end, they had compiled a total of 167 studies with the data from more than 150 different species.

Their findings? Different species are affected in different ways and to different extents, but all species are negatively affected by ocean acidification. “Our study showed that all animal groups we considered are affected negatively by higher carbon dioxide concentrations. Corals, echinoderms, and mollusks above all react very sensitively to a decline in the pH value,” says lead author Astrid Wittmann, of the Alfred Wegener Institute.

The second study demonstrates that the negative effects of ocean acidification aren’t just limited to marine life. The authors discovered that rising ocean acidity has the potential to amplify climate warming in general, through the decreased production of a biogenic sulfur compound.

Phytoplankton in the ocean produce dimethyl sulfid (DMS). As DMS is released into the air, it creates atmospheric sulfur—which increases the reflectivity of the atmosphere to incoming radiation, reducing surface temperatures. Warming acidic oceans means the phytoplankton produce less DMS, causing an even warmer planet.

In addition to the Nature papers, Philosophical Transactions of the Royal Society B has an ocean acidification-themed issue this week, with nine papers studying its effects. The papers describe three distinct effects on marine life due to ocean acidification: species interactions, decreased ecosystem functions, and adaptations. Andrew Revkin has a great summary of them on his Dot Earth blog in the New York Times.

“It’s great that some of these papers are looking at entire ecosystems,” says Aaron Pope, the Academy’s sustainability manager who works tirelessly to communicate ocean acidification issues. “There’s been lots of research in the past on individual species impacts, but data on entire natural systems was missing. Now we can start to talk about what will really happen in marine ecosystems as ocean acidification gets worse.”

One paper of the group (from local researchers at San Francisco State University) looks at tiny coccolithophores. These single-celled algae are able to sequester oceanic carbon by incorporating it into their shells, providing ballast to speed the sinking of carbon to the deep sea. The little organisms are central to the global carbon cycle, a role that could be disrupted if rising levels of atmospheric carbon dioxide and warming temperatures interfere with their ability to grow their calcified shells.

This paper might provide a bit of hope among the rest: “At least in this experiment with one coccolithophore strain, when we combined higher levels of CO₂ with higher temperatures, they actually did better in terms of calcification,” says co-author Jonathon Stillman, of SF State.

Here’s to hoping that all of these papers findings will create more awareness of ocean acidification that will lead to more solutions.

Coccolithophore image: Alison R. Taylor/PLoS Biology

Earlier this year, we produced a video documenting Academy researcher Luiz Rocha’s work in Belize studying invasive lionfish. These predators, originally from the Indo-Pacific, found their way to the northwest Atlantic in the 1990s—likely through an aquarium release—and have steadily moved south over the past fifteen years.

The lionfish are wreaking havoc in the area because they voraciously gobble up smaller, native fish—threatening everything from coral reef ecosystems to local economies based on fishing and tourism. In addition, eradication appears impossible and whatever is keeping them in check in their native Indo-Pacific habitats—researchers around the world are trying to find out what—appears to missing in the Atlantic.

“Prey in the Indo-Pacific could simply be more aware of the danger lionfish pose,” Rocha says. “There could also be parasites keeping the lionfish in check in their native habitats.”

Bad
A recent study in PLoS One determines that humans may be the only threat to lionfish in their new home. An international research team looked at whether native reef predators such as sharks and groupers could help control the population growth of lionfish in the Caribbean, either by eating them or out-competing them for prey.

The team surveyed 71 reefs over three years, in three different regions of the Caribbean. Their results indicate there is no relationship between the density of lionfish and that of native predators, suggesting that, “interactions with native predators do not influence” the number of lionfish in those areas.

The researchers did find that lionfish populations were smaller in protected reefs, but researchers attributed the lower numbers to targeted removal by reef managers, rather than consumption by large fishes in the protected areas. As Rocha mentioned in the video last spring, encouraging the hunting and human consumption of these spiny fish may be reefs’ only hope.

Ugly
Recent submersible dives deep off the coast of Fort Lauderdale, Florida reveal that these invasive lionfish populations aren’t just spreading southward—they’re also heading to great depths, out of the reach of their only predators, human hunters.

“We expected some populations of lionfish at that depth [300 feet], but their numbers and size were a surprise,” says Stephanie Green, of Oregon State University, who participated in the dives.

The lionfish are growing to an unusually large size—as much as 16 inches. “A lionfish will eat almost any fish smaller than it is,” Green says. “Regarding the large fish we observed in the submersible dives, a real concern is that they could migrate to shallower depths as well and eat many of the fish there. And the control measures we’re using at shallower depths—catch them and let people eat them—are not as practical at great depth.”

Rocha confirms this. “Even if control efforts are successful in shallow water, we can’t reach these deep fish.” And the lionfish at great depths can easily move to shallower areas. In addition, “these larger fish produce more eggs,” Rocha says, creating even larger populations.

(Rocha is hoping to join on subsequent dives. He was invited on this recent submersible dive, but was attending a conference on Indo-Pacific fish in Japan at the time. A video of the dives is available here.)

Good
We want to end on an upbeat note, and Rocha has a recent study in Marine Ecology Progress Series about the spread of lionfish down the coast of South America and into Brazil. The fish haven’t reached that far yet, but given their rapid spread, it seems to be only a matter of time.

Working with other Brazilian researchers, Rocha investigated movements of various fish species across the Amazon-Orinoco plume (AOP), where the Amazon and Orinoco rivers meet the Atlantic Ocean. The study describes the AOP as “a large freshwater and sediment runoff between the Caribbean and the Brazilian Provinces that represents a ‘porous’ barrier to dispersal for reef organisms.”

The scientists found that while a few “vagrant” species recently crossed the barrier heading north, “species headed south don’t spread as quickly,” according to Rocha. “The currents make it tricky to cross.”

This could be the first bit of good news in stopping the spread of lionfish. “This means we can keep an eye on it and control the lionfish as they cross, keeping their numbers down,” Rocha says.

Next
Rocha and colleagues here at the Academy and in Europe are beginning a population genomic study of the invasive lionfish. This study will look at fine-scale genetic diversity of lionfish among the different Caribbean islands. Rocha will start collecting samples in two weeks in Curaçao. The samples will then be analyzed by Academy researchers—including Rocha’s wife, Claudia—here at the Center for Comparative Genomics.

“We want to see if there is gene exchange between different island populations,” Rocha explains. “This will help us determine how successful local efforts to control lionfish can be if larvae are coming from other locations. This study can help inform how resources are used to control different populations.”

The fight against invasive lionfish continues…

Image: Alexander Vasenin/Wikipedia

When Academy curators Terry Gosliner and Luiz Rocha traveled to Saudi Arabia this spring to study marine life in the Red Sea and the Gulf of Aden, the contrast awaiting them couldn’t have been starker. Beyond the enclosed campus of King Abdullah University of Science and Technology (KAUST), about an hour north of Jeddah, stretched a parched terrestrial landscape with daytime temperatures hovering near 105 degrees. But once the researchers boarded the 80-foot-long catamaran, they soon ventured into a rich underwater landscape teeming with life.

For the two-part, KAUST-sponsored expedition, Gosliner, Rocha, and a team of 15 international scientists spent two weeks documenting fish diversity in the Red Sea. On the second two-week portion, Rocha and five other researchers continued to explore tropical reefs within the Gulf of Aden, in the territorial waters offshore from Oman. The invitation to collaborate on this general, comprehensive survey arose from Rocha’s participation at a 2012 KAUST conference organized by Michael Berumen that produced a research paper coauthored by Rocha, Berumen,  Brian Bowen, an associate researcher at the University of Hawaii, Joseph DiBattista, a post-doctoral fellow at KAUST, and Michelle Gaither, a post-doctoral fellow at the Academy.

“The sand dunes and rugged mountains along the Saudi coastline reminded me of Baja, California,” says Gosliner. “And the Red Sea’s narrow body of water, caused by tectonic activity and fault lines, is not unlike the Sea of Cortez,” he adds. “That said, the Red Sea has unique features that make it very interesting from a scientific perspective.”

The Arabian Peninsula, wedged between Northeastern Africa and Asia, is bordered by oceans and seas on three sides. The Red Sea, along its western coastline, has a very small, shallow connection with the Indian Ocean. “Because of this geographic separation, it has a lot of unique species,” says Rocha. “There is a lot of endemism in the Red Sea.”

Coastal Oman, at the southeastern end of the peninsula, is open to the Indian Ocean. “It also has many unique species,” says Rocha, “but for a different reason.” The sea is more affected by upwelling that does not impact marine habitats in the rest of the Indian Ocean. Upwelling, caused by wind blowing from coast to ocean, pushes away warm waters on the ocean’s surface. Cold water rises from below to fill the gap.

“You won’t find coral reefs in these conditions—they can’t thrive in cold temperatures,” says Rocha. “Not only is this fauna unique, but the tropical reefs in the Western Indian Ocean are the least known in the world.”

The researchers brought back 350 specimens of nudibranchs and fish for morphological and genetic analysis. The new specimens fill a surprising gap in the Academy’s renowned fish collection.

“We have 250,000 jars of fish at the Academy, about 3 million specimens and 11,000 species,” says Rocha. “Almost everything we brought back is new to the collection. We had very few fish from Oman.”

Another surprise was Gosliner’s assessment of the leading environmental threat to sustaining the region’s biodiversity. “This is an active zone of human activity,” he explains. “To the north, it’s a major shipping corridor through the Suez Canal into the Mediterranean. In the south, you have the Somali pirates.”

And the source of the most severe harm to the ocean biome?

“Overfishing,” says Gosliner. “That has greater impact than all the other activities put together.”

Last but not least: How did the Red Sea get its unusual name? According to Gosliner, a leading theory is that periodic outbreaks of algal blooms caused by dinoflagellates temporarily changed the water’s color.

“When early explorers toured the area,” he says, “they may have seen that phenomenon we now call a ‘red tide.’ But the waters are a sparkling turquoise blue most of the time. So the Red Sea is truly a misnomer.”

Barbara Tannenbaum is a science writer working with the Academy’s Digital Engagement Studio. Her work has appeared in the New York Times, San Francisco Magazine and many other publications.

Image: Terry Gosliner

At over three feet, you’d think the solo coral grouper would be threatening enough. Threatening sure, but a successful lone hunter? Well, not so much, according to National Geographic News Watch:

When hunting alone, groupers only catch their prey about 1 out of every 20 attempts.

So the grouper teams up with the even fiercer moray eel, or the very large Napolean wrasse, to go hunting. The fish are looking for smaller coral reef fishes that hide from their predators under rocks and coral. When the grouper detects the hiding prey, it signals its hunting friend and together they both flush the prey out of hiding.

The cooperation, however, ends there. Whoever gets the prey, eats it whole. There’s no sharing of the spoils. Still, for the grouper, it’s worth the shared hunting, says National Geographic News Watch:

When they have help, the ratio is significantly better—about one out of seven.

What’s most significant about this shared hunting are the signals the grouper makes to its partner during the hunt, say scientists. Researchers studying the fish observed dozens of events where groupers performed upside-down headstands with concurrent head shakes to indicate the presence and location of particular prey to cooperative partners. Their study, published last week in Nature Communications, call the groupers’ signals “referential gestures”. From the abstract:

In humans, referential gestures intentionally draw the attention of a partner to an object of mutual interest, and are considered a key element in language development. Outside humans, referential gestures have only been attributed to great apes and, most recently, ravens.

It’s likely that these gestures have been understudied in non-primate species, say Academy researchers, who point to hunting dogs and even bee dances as potential consideration for referential gestures.

The researchers of the study say that the mental processes underlying these gestures in fish, apes and ravens are unclear and may well vary among these taxa. Their findings point to the fish having developed cognitive skills according to their particular ecological needs.

Whatever the cause, these hunting tactics are pretty extraordinary. Videos of the behaviors can be found here. For more information on the study, visit the University of Cambridge website.

Image: jon hanson/Wikipedia

Now, an international team of researchers has sequenced the genome of one of the two living species of coelacanths. The results are published in this week’s Nature.

The endangered African coelacanth (Latimeria chalumnae) has more up its sleeve than just the living fossil thing. Scientists have long thought that this group of fishes gave rise to the first four-legged amphibious creatures to climb out of the water and up on land. Lobe-finned fishes (with fins like limbs) are genealogically placed in-between the ray-finned fishes, such as goldfish and guppies, and the tetrapods—the first four-limbed vertebrates and their descendants, including living and extinct amphibians, reptiles, birds, and mammals.

Results from the genomic study place the coelacanths behind lungfish, another lobe-finned living fossil, as the closest fishy relative to tetrapods. But other data from the study still make coelacanths incredibly interesting.

These prehistoric-looking fish are evolving at a very leisurely pace. “We found that the genes overall are evolving significantly slower than in every other fish and land vertebrate that we looked at,” says co-author Jessica Alföldi, of the Broad Institute of MIT and Harvard.

“We often talk about how species have changed over time,” says Kerstin Lindblad-Toh, another co-author from the Broad Institute. “But there are still a few places on Earth where organisms don’t have to change, and this is one of them. Coelacanths are likely very specialized to such a specific, non-changing, extreme environment—it is ideally suited to the deep sea just the way it is.”

Researchers also found several key genetic regions that may have been “evolutionarily recruited” to form tetrapod innovations such as limbs, fingers, and toes, and the mammalian placenta. One of these regions, known as HoxD, harbors a particular sequence that is shared across coelacanths and tetrapods. Tetrapods likely co-opted this sequence from the coelacanth to help form hands and feet.

“This is just the beginning of many analyses on what the coelacanth can teach us about the emergence of land vertebrates, including humans, and, combined with modern empirical approaches, can lend insights into the mechanisms that have contributed to major evolutionary innovations,” says the paper’s lead author, Chris Amemiya of the Benaroya Research Institute.

Image: Ballista/Wikipedia