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

Ever wonder what fish think about?

For the first time, a group of scientists from Japan’s National Institute of Genetics have captured video of thoughts moving through the brain of a zebrafish (Danio rerio).

Zebrafish often serve as animal models in research because of their transparent bodies. By inserting a gene into the larvae—and using a probe that detects florescence, the scientists captured the fish’s mental reaction to a swimming paramecium (think “dinner”) in real time.

The key element to the technology is a special indicator called GCaMP that reacts to the presence of calcium ions by increasing florescence. Since neuron activity in the brain involves rapid increases in concentrations of calcium ions, insertion of GCaMP causes the particular areas that are activated in a zebrafish brain to glow brightly. By using a jellyfish protein called GFP sensitive to florescence and neuroimaging techniques such as fMRI, the scientists monitored the locations of the fish’s brain activated at any given moment and thus, capture the fish’s thought as it “swam” around the brain.

The results show that when the paramecium moved from right to left, the zebrafish’s neuron activity moved from left to right, because in our brains the signals from our eyes cross over into the opposite half of the brain. If the paramecium stayed still next to the fish’s eye, its brain never fired.

This isn’t the first time that GCaMP gene has been inserted into a zebrafish for imaging purposes, but no real-time video images had been captured before. The achievement, published in Current Biology, could have future applications in humans. Scientists could quickly map the parts of the brain affected by a chemical under consideration for potential drug or treatment uses, thus shortening the development of new and more effective psychiatric medications.

The new tool now makes it possible to ask which brain circuits are involved in complex behaviors, from perception to movement to decision-making, the researchers say, noting that the basic design and function of a zebrafish brain resembles our own.

“In the future, we can interpret an animal’s behavior, including learning and memory, fear, joy, or anger, based on the activity of particular combinations of neurons,” study author Koichi Kawakami says.

Zuberoa Marcos is a former biologist and current science writer based in Barcelona. She writes articles regularly for Science Today.

Lo que piensan los peces

Por Zuberoa Marcos

Por primera vez, un grupo de científicos del Instituto Nacional de Genética en Japón ha capturado un vídeo de los pensamientos de un pez cebra (Danio rerio) moviéndose en el interior de su cerebro.

El pez cebra es un modelo animal muy utilizado en investigación porque su cuerpo es transparente. Insertando un gen en el pez cebra y utilizando una molécula que detecta la fluorescencia, los científicos fueron capaces de capturar, en tiempo real, la reacción mental del pez a un paramecio nadando en su entorno.

El elemento clave de la tecnología japonesa es un gen llamado GCaMP que reacciona ante la presencia de iones de calcio provocando un aumento en la fluorescencia. La actividad neuronal en el cerebro implica un rápido incremento en las concentraciones de iones de calcio, por lo que la inserción del gen hace que determinadas áreas del cerebro del pez cebra se activen y brillen. Utilizando una proteína de las medusas llamada GFP sensible a la fluorescencia y técnicas de neuroimagen como la FMRI, los investigadores fueron capaces de monitorizar las áreas del cerebro de los peces que se activaron en cada momento y, por lo tanto, capturar cómo se movía su pensamiento de unas regiones a otras.

En concreto, los investigadores analizaron qué sucede cuando un pez cebra ve un paramecio -un organismo unicelular que el pez considera una fuente de alimento- nadando ante si. Los resultados mostraron que cuando el paramecio se desplaza de derecha a izquierda, la actividad de la neuronas del pez lo hace de izquierda a derecha debido a que, en nuestro cerebr, las señales procedentes de los ojos se cruzan a la mitad opuesta del cerebro. Si el paramecio permanecía quieto, no había respuesta en el cerebro de animal.

Los científicos ya habían insertado con anterioridad el gen GCaMP en un pez cebra pero ésta es la primera vez que filman las imágenes de lo que sucede en el animal en tiempo real. El avance, publicado en la revista Current Biology, es impresionante en sí mismo pero, además, podría tener aplicaciones futuras en los seres humanos. Podría ayudar a identificar rápidamente las regiones del cerebro sobre las que actúa un potencial medicamento y hacer más breve el proceso de desarrollo de mejores fármacos para enfermedades psiquiátricas.

El trabajo también podría tener usos éticamente discutibles, como leer la mente. El equipo japonés está investigando cómo utilizar su proteína fluorescente en otras regiones del cerebro, para poder identificar los circuitos neuronales que intervienen en la toma de decisiones y en el forjado de distintos comportamientos. Creen que, con el tiempo, serán capaces de visualizar todo el cerebro a la vez incluso emociones como el miedo, la alegría o la ira en función de la actividad de combinaciones particulares de neuronas.

Zuberoa Marcos es bióloga retirada y actualmente trabaja como periodista científica desde Barcelona. Escribe de forma regular para Science Today.

Image: KAWAKAMI et al.

The past month has seen some positive news on this front (aside from our recent grouper story), but we’re not advocating going fish-crazy! In fact, the first article we’re pointing to shows a disturbing graphic of changes in fish biomass in the northern Atlantic from 1900 to 2000. But as NPR’s Robert Krulwich says, perhaps we’ve already adjusted to these changes:

Maybe, deep down, we sense that some foods are no longer plentiful so we make it the fashion to eat less of them? Do we reset our appetites from generation to generation?

He illustrates the behavior change with two very different menus.

Speaking of menus and NPR, we recently found this Dan Barber TED Talk through NPR’s TED Radio Hour. If you haven’t watched it, you’ll never believe how absolutely beautiful fish farming can be. The Spanish fish farm he describes also purifies water and provides a sanctuary for birds!

DNA Fish Tales

A recent study in Current Biology used DNA to explore the effectiveness of marine reserves at protecting and sustaining fish. New Scientist has the details:

…with the use of new DNA profiling techniques, scientists have shown that by devoting less than a third of an area to a marine reserve network, you can double the number of juvenile fish that settle in the rest of the area.

These protected areas are actually replenishing other areas for commercial fishing. Do you think this study will affect policy to create more reserves?

Another recent study, this time in Nature Communications, describes using genetic markers to track down illegal catches in Europe. This technique can pinpoint the origin of fish so authorities know if similar-appearing fish are legal or illegal. ScienceNOW reports:

A €4 million pan-European project, launched in 2008 and called FishPopTrace, has devised a much-anticipated way to differentiate marine populations of the same species with up to 100% accuracy.

More Good News

The National Oceanic and Atmospheric Administration (NOAA) issued a report two weeks ago on the improvements of US fisheries. The news is mostly good: 86% of fishing stocks are not overfished. According to Discover’s 80beats blog, this is due to the Magnuson-Stevens Reauthorization Act of 2006:

The act states that each year NOAA must give status updates on all fish populations within 200 miles of the US Coast. If the fisheries are hurting, fishermen must stop catching those fish until their numbers recover.

Weird Fish Tale

Did you hear the one about the bottlenose dolphins that have helped Brazilian fishermen for over a hundred years? Weird, but true! They work together to gain a bigger catch! The research is published in Biology Letters; you can read more here or here.

Okay, with all of this research, we’ve finally made our seafood decision, but how shall we cook it? Luckily, the Pew Environment Group recently posted some “Recipes for Success” that share famous chefs’ takes on sustainable seafood. Num!

Do you have a fish tale? A good recipe? Please share it with us below!

Image: NOAA

What the…?

Remember this video we produced a while ago about the super cool mimic octopus? It compresses and conforms itself to look like a sea snake, flatfish, or lionfish—adjusting its look for different situations. Thanks to these brazen habits, it can swim in the open with relatively little fear of predators.

Well, it now appears the mimic octopus has a companion mimic. Last summer, Godehard Kopp of the University of Gottingen, Germany took this video while diving in Indonesia. A black-marble jawfish is seen closely following a mimic octopus as it moves across the sandy bottom. The jawfish has brown-and-white markings similar to the octopus and is difficult to spot among the many arms. The octopus, for its part, doesn’t seem to notice or care.

Kopp sent the video to Rich Ross and Luiz Rocha here at the Academy, who identified the jawfish species. Since this association had not been recorded before, they published their observations last month in the scientific journal Coral Reefs. The authors surmise that the jawfish hitches a ride with the octopus for protection, allowing it to venture away from its burrow to look for food—a case of “opportunistic mimicry.”

“This is a unique case in the reefs not only because the model for the jawfish is a mimic itself, but also because this is the first case of a jawfish involved in mimicry,” says Rocha, assistant curator of ichthyology. “Unfortunately, reefs in the Coral Triangle area of southeast Asia are rapidly declining mostly due to harmful human activities, and we may lose species involved in unique interactions like this even before we get to know them.”

Luiz Rocha and his colleagues set about finding out how coral reef fish make long distance journeys across the Atlantic (about 3500km/2200 miles near the equator) or the freshwater and sediment discharges of the Amazon and Orinoco rivers in South America (about 2300 km/1500 miles).

Coral reef fish don’t move a lot as adults, so the long held belief was that the fish dispersed in their larval stage. The larval stage can last 10 days for some species and 100 days for others and it may take 50 days to cross the Atlantic. Looking at the variables and the distribution for 985 species, the researchers found that the larval stage actually had little to do with which fish crossed the large distances and barriers—or how they managed to do it.

Dispersal seems to factor on other specifics—the size of the adult fish, whether the fish could use flotsam, or sargassum mats, as habitats across the barriers and if the fish were generalists—able to adapt to new habitats and food. Luiz and his collaborators published their findings last week in the Proceedings of the Royal Society: B. From the abstract:

Successful establishment after crossing both barriers may be facilitated by broad environmental tolerance associated with large body size and wide latitudinal-range. These results highlight the need to look beyond larval-dispersal potential and assess adult-biology traits when assessing determinants of successful movements across marine barriers.

Luiz gave us some examples:

The Brown Chromis (Chromis multilineata) is a great example of a fish that has a short larval stage but crosses barriers using floating substrate.

Many species of parrotfishes in the Caribbean have long larval stages but are restricted to the Caribbean, and found neither in Brazil nor in the other side of the Atlantic.

Some species of wrasses of the genus Halichoeres cross the Amazon barrier but don’t survive on the other side because they can’t find their preferred habitat. In this genus, the specialists tend to have smaller geographical ranges than the generalists. One of the examples is Halichoeres poeyi, a wrasse that lives not only in coral reefs, but also rocky reefs and seagrass. This wrasse is continuously distributed from South Brazil to Florida, and all of the other (more specialized) species in this genus are different in either side of the Amazon barrier.

The study built upon a paper the team published in 2008—a culmination of five years of work, creating a database of 1,300 Atlantic species of coral reef fish. The database includes many variables for each species—biogeographic data, reproductive mode (which is a proxy for length of the larval stage), spawning information, size as an adult, habitat needs, and more.

Luiz Rocha joined the Academy less than a month ago, as a curator of ichthyology, specializing in coral reef fish. Originally from Brazil, he fell in love with these fish at an early age—snorkeling since the age of five! He comes to the Academy from the University of Texas. Stay tuned for more of his research.

Image by John E. Randall, WorldFish Center – FishBase, EOL