Researchers solve mystery of deep-sea fish with tubular eyes and transparent head

This article is about a year old but I thought it was worth sharing

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Researchers at the Monterey Bay Aquarium Research Institute recently solved the half-century-old mystery of a fish with tubular eyes and a transparent head. Ever since the "barreleye" fish Macropinna microstomawas first described in 1939, marine biologists have known that its tubular eyes are very good at collecting light. However, the eyes were believed to be fixed in place and seemed to provide only a "tunnel-vision" view of whatever was directly above the fish's head. A new paper by Bruce Robison and Kim Reisenbichler shows that these unusual eyes can rotate within a transparent shield that covers the fish's head. This allows the barreleye to peer up at potential prey or focus forward to see what it is eating.

Deep-sea fish have adapted to their pitch-black environment in a variety of amazing ways. Several species of deep-water fishes in the family Opisthoproctidae are called "barreleyes" because their eyes are tubular in shape. Barreleyes typically live near the depth where sunlight from the surface fades to complete blackness. They use their ultra-sensitive tubular eyes to search for the faint silhouettes of prey overhead. Although such tubular eyes are very good at collecting light, they have a very narrow field of view. Furthermore, until now, most marine biologists believed that barreleye's eyes were fixed in their heads, which would allow them to only look upward. This would make it impossible for the fishes to see what was directly in front of them, and very difficult for them to capture prey with their small, pointed mouths...

(Rest of the article here: http://www.mbari.org/news/news_releases/2009/barreleye/barreleye.html)

I will be in the Ichthyology lab this evening from 5-6pm to answer questions and help you prepare for the lab practical (tomorrow!!!). This is a valuable opportunity to test your ability to recognize anatomy and key fish! You can practice/study in the lab at other times as well; but this is the best time to come in if you feel like you need clarification in certain areas.

*****I will be most able to help you if you email me questions prior to 4:00pm today!

-Em :)

Ancient filter feeders found lurking in museums

18 February 2010 | Nature | doi:10.1038/news.2010.80

Fish fossils fill gaps in dinosaur-era ocean food chains.

Andrew Bennett Hellman

Artist's reconstruction of the 70-million-year old giant suspension-feeding bony fish Bonnerichthys.Robert Nicholls, www.paleocreations.com

The first large filter feeders swam in the oceans for much longer than previously thought.

In a study published today in Science, Matt Friedman, a palaeobiologist at the University of Oxford, UK, and his colleagues identify filter feeders in fossils spanning more than 100 million years and originating in Asia, Europe and North America. The discovery is a result of examining fossils from museums around the world that had either not been studied or had been misinterpreted.

"Given how widespread they were and how long they appear in the geological records, I think it's an important finding that's really going to force us to think about what role these bony fish had," said Nick Pyenson, a fossil marine vertebrate expert at the Smithsonian Institution's National Museum of Natural History in Washington DC.

Palaeobiologists had thought that large-bodied filter feeders only lived for about 20 million years of the Mesozoic era, but this study demonstrates that they existed from 170 million years ago to 65 million years ago. The newly classified fish plug a gap in the understanding of food webs in the Mesozoic era, which ran from 251 million years ago to 65 million years ago. The absence of those large feeders for most of the era, despite the presence of plankton, had perplexed scientists, in part because of the diversity of modern filter feeders, which include whales and sharks.

Big mouth strikes again

Friedman's study of ancient filter feeders began when he was asked to examine an odd fish fossil from the Rocky Mountain Dinosaur Resource Center in Colorado. It had fins similar to those of ancient predatory fishes but lacked the expected teeth. The fossil's thin skull and long, slender jaw bones reminded Friedman of filter feeders.

"All of a sudden the penny dropped and I realized that this animal was very similar to poorly known animals, ones that were considered unsuccessful from much earlier in the geological record. And here we had a very geologically young example of this group of animals, which dictated that they were around about five times longer than we thought they were before," said Friedman.

Armed with his new knowledge, Friedman searched for other filter feeders in fossils from other museums including the Sternberg Museum in Hays, Kansas and the University of Nebraska State Museum in Lincoln. He found new examples and even corrected some misclassified samples.

The enormous forefins of Bonnerichthys.M. Friedman, University of Oxford.

Palaeontologists frequently have to classify fossil remains based on partial skeletons. Fish fossils often consist mostly of fins and few or no skull bones, and without a head, it is not easy to tell whether the fins belong to a fish that filter feeds or to a fish that hunts. So nineteenth-century scientists often used similarities between fins to group fossils, and some filter feeder bones were classified as the poorly understood kin of toothy predators.

Friedman and his colleagues found other fossils with telltale traits of sieve-faced feeders: long, slender, toothless jaws, a large gill skeleton, and gill rakers, which are elaborate structures that direct water into the gullet. They then created a family tree and found that the newly identified animals were relatively close kin.

"I'm sure that a lot of the collections around the world contain strange bones and nobody knows what they are, and actually they belong to this group," says Lionel Cavin, curator of the geology and palaeontology department at the Natural History Museum of Geneva in Switzerland.

So although the new evidence expands the range of planktivorous vertebrates, it seems as if the hunt for more of them has just begun.

original article: http://www.nature.com/news/2010/100218/full/news.2010.80.html

lab practical help session

Hey Ich students,

I am willing to host a help session for next week's lab practical exam. I will be in the Ich lab on Tuesday night, from 5-6, if I get interest from anybody in the class. This would be a great opportunity to get some more practice identifying pieces of anatomy, and keying/recognizing fish. Let me know by Monday next week and I will send out an announcement to everyone as to whether or not the session will take place! If this time doesn't work, email me and we'll figure something out.

Enjoy the weekend!
Emily Nebergall

MENHADEN!!!

A Fish Oil Story

By Paul Greenberg

“WHAT’S the deal with fish oil?”

If you are someone who catches and eats a lot of fish, as I am, you get adept at answering questions about which fish are safe, which are sustainable and which should be avoided altogether. But when this fish oil question arrived in my inbox recently, I was stumped. I knew that concerns about overfishing had prompted many consumers to choose supplements as a guilt-free way of getting their omega-3 fatty acids, which studies show lower triglycerides and the risk of heart attack. But I had never looked into the fish behind the oil and whether it was fit, morally or environmentally speaking, to be consumed.

The deal with fish oil, I found out, is that a considerable portion of it comes from a creature upon which the entire Atlantic coastal ecosystem relies, a big-headed, smelly, foot-long member of the herring family called menhaden, which a recent book identifies in its title as “The Most Important Fish in the Sea.”

The book’s author, H. Bruce Franklin, compares menhaden to the passenger pigeon and related to me recently how his research uncovered that populations were once so large that “the vanguard of the fish’s annual migration would reach Cape Cod while the rearguard was still in Maine.” Menhaden filter-feed nearly exclusively on algae, the most abundant forage in the world, and are prolifically good at converting that algae into omega-3 fatty acids and other important proteins and oils. They also form the basis of the Atlantic Coast’s marine food chain.

Nearly every fish a fish eater likes to eat eats menhaden. Bluefin tuna, striped bass, redfish and bluefish are just a few of the diners at the menhaden buffet. All of these fish are high in omega-3 fatty acids but are unable themselves to synthesize them. The omega-3s they have come from menhaden.

But menhaden are entering the final losing phases of a century-and-a-half fight for survival that began when humans started turning huge schools into fertilizer and lamp oil. Once petroleum-based oils replaced menhaden oil in lamps, trillions of menhaden were ground into feed for hogs, chickens and pets. Today, hundreds of millions of pounds of them are converted into lipstick, salmon feed, paint, “buttery spread,” salad dressing and, yes, some of those omega-3 supplements you have been forcing on your children. All of these products can be made with more environmentally benign substitutes, but menhaden are still used in great (though declining) numbers because they can be caught and processed cheaply.

For the last decade, one company, Omega Protein of Houston, has been catching 90 percent of the nation’s menhaden. The perniciousness of menhaden removals has been widely enough recognized that 13 of the 15 Atlantic states have banned Omega Protein’s boats from their waters. But the company’s toehold in North Carolina and Virginia (where it has its largest processing plant), and its continued right to fish in federal waters, means a half-billion menhaden are still taken from the ecosystem every year.

For fish guys like me, this egregious privatization of what is essentially a public resource is shocking. But even if you are not interested in fish, there is an important reason for concern about menhaden’s decline.

Quite simply, menhaden keep the water clean. The muddy brown color of the Long Island Sound and the growing dead zones in the Chesapeake Bay are the direct result of inadequate water filtration — a job that was once carried out by menhaden. An adult menhaden can rid four to six gallons of water of algae in a minute. Imagine then the water-cleaning capacity of the half-billion menhaden we “reduce” into oil every year.

So what is the seeker of omega-3 supplements to do? Bruce Franklin points out that there are 75 commercial products — including fish-oil pills made from fish discards — that don’t contribute directly to the depletion of a fishery. Flax oil also fits the bill and uses no fish at all.

But I’ve come to realize that, as with many issues surrounding fish, more powerful fulcrums than consumer choice need to be put in motion to fix things. President Obama and the Congressional leadership have repeatedly stressed their commitment to wresting the wealth of the nation from the hands of a few. A demonstration of this commitment would be to ban the fishing of menhaden in federal waters. The Virginia Legislature could enact a similar moratorium in the Chesapeake Bay (the largest menhaden nursery in the world).

The menhaden is a small fish that in its multitudes plays such a big role in our economy and environment that its fate shouldn’t be effectively controlled by a single company and its bottles of fish oil supplements. If our government is serious about standing up for the little guy, it should start by giving a little, but crucial, fish a fair deal.

Paul Greenberg is the author of the forthcoming “Four Fish: The Future of the Last Wild Food.”

This article has been revised to reflect the following correction:

Correction: December 18, 2009
An Op-Ed article on Wednesday, about fish oil supplements, misstated the amount of menhaden converted into capsules and other products. It is hundreds of millions of pounds a year, not hundreds of billions.

Feds pass on surest solution to Asian carp advance

By JOHN FLESHER, AP Environmental Writer John Flesher, Ap Environmental Writer


TRAVERSE CITY, Mich. – The surest way to keep rampaging Asian carp from gaining a foothold in the Great Lakes is to sever the link between Lake Michigan and the Mississippi River basin, created by engineers in Chicago more than a century ago.
That would thrill environmentalists and those who make their living in the $7 billion Great Lakes fishing industry, which could be devastated by a carp invasion. Not so the barge operators who move millions of tons of commodities on the Chicago-area waterways each year.
And so, pulled in different directions by both, as well as politicians in the Great Lakes states, the Obama administration this week proposed a $78.5 million plan that appears to make no one happy.
"It appears to be politically negotiated rather than scientifically based ... sort of like trying to cut the baby in half," said Thom Cmar, an attorney with the Natural Resources Defense Council. "It offers a lot of middle-ground alternatives with no discussion of why any of them would actually work."
Shippers worry about a promised study that would examine closing more often a pair of navigational locks at Chicago, and the prospect that a long-term study could recommend severing the connection between the river and the lakes for good.
Environmentalists, meanwhile, fear the plan's reliance on strengthening an electric barrier designed to block the carp's advance — and other measures, such as stepping up efforts to find and kill fish that may have slipped through — is an expensive gamble that might not be enough to ward off an infestation.
"We're spending close to $80 million just for a short-term deterrent," said Joel Brammeier, president of the Alliance for the Great Lakes, an environmental group. "We need to stop pushing money toward temporary solutions and get everyone on track toward investing in one that works for good — and that means absolute physical separation."
Bighead and silver carp — both native to Asia — have been migrating toward the lakes since escaping from Deep South fish ponds and sewage treatment plants in the 1970s. The biggest can reach 100 pounds and 4 feet long, consuming up to 40 percent of their body weight daily in plankton, the base of the aquatic food chain. Once established in the lakes, the carp could starve out the prey fish on which popular species such as salmon and whitefish depend.
The carp have already infested parts of the Mississippi and Illinois rivers, driving away many native fish. Silver carp are known to hurtle from the water at the sound of passing motors and slam into boaters with bone-breaking force.
While scientists differ on whether the carp would thrive in the Great Lakes, which are colder, deeper and ecologically different than rivers, many say the risk is too great to take any chances.
"None of us know for certain what their impact would be," University of Notre Dame biologist David Lodge told a House subcommittee this week. "There's only one way to find out, and I don't think any of us want that."
To be fair, the solution environmentalists prefer — cutting ties between the lakes and the Mississippi — would mean reconfiguring some 70 miles of canals and rivers. That's a massive undertaking that could not happen quickly. "We cannot fight biology with engineering alone," Cameron Davis, the Environmental Protection Agency's spokesman on the issue, told the congressional panel.
Yet the federal plan is heavy on technological innovations. Among them: barriers using sound, strobe lights and bubble curtains to repel carp and biological controls to prevent them from reproducing. They're promising measures, but still on the drawing board.
Environmentalists and Great Lakes governors outside of Illinois who want to close the Chicago locks claim it's the best short-term option. But it isn't a foolproof solution, as young carp might still be able to slip through the leaky structures. The Chicago waterways also have other access points to Lake Michigan.
Army Corps of Engineers officials are putting their faith in the two-tiered electric barrier in the Chicago Sanitary and Ship Canal about 25 miles from Lake Michigan, to which they will add a third section this year. It emits pulses to scare off the carp or knock them unconscious if they don't turn back. No carp have been found above the barrier, although biologists have detected their DNA in numerous spots past it and even within the lake itself.
"While we're all talking," Lodge said, "the fish are swimming."
That almost certainly means at least some carp have eluded the device and reached the lake. The government's plan aims to keep their number low enough to prevent them from breeding. The problem is that no one knows how many carp need to make it into the lake to establish a foothold that can't be turned back.
"This is a lot of money to pile into stopgap measures," said Phil Moy, a University of Wisconsin Sea Grant researcher. "It may do some good in the short term, but in the long term it's not going to solve the problem of invasive species on both sides of the divide. Ecological separation has to happen for this to be successful."

Light shed on fish gill mystery

By Victoria Gill
Science reporter, BBC News


Biologists have cast doubt on the long-held theory that fish gills evolved primarily for the purpose of breathing.

The researchers studied the development of gills in rainbow trout larvae. Their experiment suggests that it is likely that fish evolved gills for the primary purpose of regulating the chemicals in their bodies. The team reports in the Royal Society journal Proceedings B that this developmental study gives an insight into the evolution of fish gills. Clarice Fu, a zoologist from the University of British Columbia in Canada, led the study. She and her colleagues found, as the larvae matured, their gills developed the ability to regulate the chemicals in their blood earlier than they began to take up oxygen. To discover this, the team measured the uptake of ions, which are charged chemical particles, such as sodium. These ions are necessary for the body's cells to function, but they become toxic if their levels in the blood become too high. Ms Fu explained that fish take up these ions from the surrounding water, to "maintain this delicate ion balance in their blood". "In freshwater fish, like rainbow trout, they tend to lose ions from their blood to the water, because the ion concentration in blood is greater than that of freshwater," she said. The team took measurements from the gills of young, developing rainbow trout to find out what functions they were performing.

"When the gills are still immature, a significant portion of ion uptake occurs at the skin. As the fish get older and the gills mature, [this] can gradually shift to... the gills," said Ms Fu.

"We found that ion uptake shifted from the skin to the gills earlier than oxygen uptake. This led us to propose that the gills are needed for ion regulation earlier than they are needed for oxygen uptake."

Watching evolution

Ms Fu told BBC News that the "pressures" on developing larvae are similar to evolutionary pressures.

"Some of these pressures include an increasingly active lifestyle, greater body size, increasingly thicker skin," she said. Scientists often study larval development to investigate evolution. Ms Fu explained that, as the larvae developed, the pressures drove ion exchange to the gills before the animals started to breathe through their gills, so the same thing may have happened as the fish evolved. Professor Rick Gonzalez, from the University of San Diego in the US, studies the physiology of aquatic animals. He described the study as a "very interesting first step", but said it wasn't clear if it answered the question of why fish evolved gills.

"Gills combine some of the functions of the lungs and kidneys in mammals, which leads to interesting interactions of function," he told BBC News.

"The physical and chemical nature of the water can play an important role in their function. So how these all work together to get the various jobs done is very interesting and offers insight into how natural selection works."

Freshwater Fishing @ Matoka Spillway

It's been so cold and snowy lately that it's hard to believe that just about two weeks ago (Jan 28) us local-freshwater folk were experiencing perfect fish-catching weather. Dr. Haines, Matt, Stephen, Audry, and I (Courtney) went down the the Matoka Spillway mid-afternoon and managed to catch a total of 4 fish (including 3 different species - we think - bluegill, darter, and white crappie!).

Actually catching the fish was surprisingly not that difficult. Matt and Audry pulled on those always trendy waders and splashed around in the stream while Stephen and I set the seine net across the width of the stream, trying to have the weights alonf the base of the net rest along the bottom of the stream. Then Matt and Audry would stomp and poke their nets around while they walked towards the net - the idea being that they might scare the fish downstream into the seine. we repeated this procedure about 5 times, each repetition a little further downstream than the last, until we had captured 4 fish! After returning borrowed equipment (waders, pole-nets and seine net) to the Keck lab we went back to Millington 13. There we had to acclimate the fish to the new tank temperature before adding them to the tank and trying to key them.

We have yet to name our new fish, and we haven't had them for very long - so, I'm not going to talk about them too much, but I want to say that the darter is especially cool looking because it has a double dorsal fin. Anyway, fishing was fun and I'm looking forward to adding more fish to the aquarium. I don't know about the rest of the local freshwater group, but I'd really like to get a catfish in before the end of the semester. Anyway, good-job team! Have a good Sunday and see y'all on Tuesday.

Freshwater Fish At The Top Of The Food Chain Evolve More Slowly

ScienceDaily (Aug. 18, 2009) — For avid fishermen and anglers, the largemouth bass is a favorite freshwater fish with an appetite for minnows. A new study finds that once they evolved to eat other fish, largemouth bass and fellow fish-feeders have remained relatively unchanged compared with their insect- and snail-eating cousins. As these fishes became top predators in aquatic ecosystems, natural selection put the breaks on evolution, say researchers.

A highly sought-after game fish, the largemouth bass belongs to a group of roughly 30 freshwater fishes known as centrarchids. Centrarchids are native to North America but have since been introduced into lakes, rivers and streams worldwide. This group of fishes eats a wide range of aquatic animals, says first author David Collar. "There's a good deal of diet diversity in the group," says Collar, a postdoctoral researcher at Harvard University. "Some species feed on insects, snails, or small crustaceans, and others feed primarily on fish."

In terms of nutritional value, fish are loaded with fats and proteins needed for growth, explain the researchers. "Fish make great fish food," says co-author Brian O'Meara of the National Evolutionary Synthesis Center. "But they're hard to catch," says O'Meara.

Biologists have long known that certain head and body shapes make some centrarchids better at catching fish than others. To catch, kill, and swallow fish prey, it helps to have a supersized mouth. "There are a lot of different sizes and shapes that will be fairly good at feeding on insects," Collar explains. "But there's really only one way to be good at feeding on fish – you need a large mouth that can engulf the prey." The largemouth bass is a prime example: "There's no fish out there that's a better fish-feeder," says co-author Peter Wainwright of the University of California at Davis.

One key to feeding on fish is to have a large mouth, but the other part of the equation is speed, the researchers explain. "A largemouth bass mostly relies on swimming to overtake its prey, and at the last moment will pop open its mouth — kind of like popping open an umbrella — and inhale the prey item," says Wainwright. "They're able to strike very quickly and inhale a huge volume of water, which allows them to catch these big elusive prey."

For largemouth bass and other species that feed primarily on fish, the researchers wanted to know how this feeding strategy affected the pace and shape of evolution. "The question we wanted to ask was: What is the interplay between the evolution of diet and the evolution of form?" says Collar.

To find out, the researchers examined museum specimens representing 29 species of centrarchid fishes. Using a chemical process to stain and visualize the bones, muscles, and connective tissue, they measured the fine parts of the head and mouth. "A fish mouth is much more complicated than our own mouth," says Wainwright. "Whereas we have one bone that moves — our jaw — fish actually have two dozen separately moving bones, and lots of muscles that move those bones in a coordinated fashion."

By mapping these measurements onto the centrarchid family tree — together with data on what each fish eats — the researchers were able to reconstruct how diet and head shape have changed over time. "It looks as if the variety of head shapes and sizes in centrarchids is strongly influenced by what they eat — primarily whether they eat other fish or not," says Collar.

More importantly, when they compared fish-feeders with species that eat other types of prey, the researchers found that bass and other centrarchids that feed primarily on fish have remained relatively unchanged over time. Once they evolved the optimal size and shape for catching fish — roughly 20 million years ago — natural selection seems to have kept them in an evolutionary holding pattern, the researchers say.

"At some point in the history of this group, some of them started feeding on fish," says Wainwright. "And once they achieved a morphology that was good at feeding on fish, they tended not to evolve away from that," he adds. "They were already good at catching the best thing out there. Why should they diversify any more? Life was good."

The National Evolutionary Synthesis Center (NESCent) is an NSF-funded collaborative research center operated by Duke University, the University of North Carolina at Chapel Hill, and North Carolina State University.