Maternal Instincts

Hi ho everyone! I know it's been forever since I last posted, and you're probably missing your weekly-ish fix of fascinating marine science and news. I've been enjoying an incredible field course through my university that has been eating up all my time. I might do a post about it at some point because we've spent some time doing ocean education. Anyway Depth and Taxa is back just in time for mother's day, so this week we'll be looking at some of the best moms the ocean has to offer.

All moms are willing to give up everything for their kids, but our first ocean mother takes this to a bit of a literal extreme. We've talked about how giant Pacific octopus (Enteroctopus dolfleini) are the largest in the world before, but there's a lot more to these incredible creatures than their size. After mating with one or more partners, female giant Pacific octopus lope off to find themselves a den. Sturdy shelters are an important part of octopuses' entire lives since they have no shell to protect them like other mollusks, but this will be a special space. The den the mother to be is looking for will be her nursery. Once she's found the perfect spot, she'll start braiding together 80-100 thousand eggs with her bare suckers. 

  "Oh you knitted those socks yourself? That's cute."

Couretsy: Ratha Grimes via Flickr

The mother octopus sticks these ropes of eggs to the ceiling where they'll spend the next five to seven months developing. In all that time mom never leaves the den. She sits in her nest, brushing her arms over the eggs to keep them clean, and pushing water from her siphon over them to keep them oxygenated. From the day she lays to the day the babies hatch she never eats a thing. All that devotion and starvation takes a severe toll on mother octopuses' and usually their last act is to push their adorable octolings out into the world with a blast water. 

It's certainly a beautiful story of motherly commitment, but why does it have to be so sad? Why can't mom stick around and raise her young. Well no one knows for sure, but it might have something to do with the fact that adult octopus compete to the point of occasionally eating one another.

 "One look at you and I can't disguise. I've got hungry eyes."

Courtesy: John Turnbull via Flickr

To find an ocean mom that keeps mothering long after her kids are capable of surviving on their own; we need to return to the more familiar world of mammals. 

Orcas, also called killer whales (Orcinus orca), are found across more of the world than most other mammals. In order to become so successful they've had to come up with some incredible strategies for survival. One of those strategies is recognizing that "mother knows best". Orca groups, called pods, are led by matriarchs who care for their children their entire lives. These mother-leaders remember where the best hunting grounds are, what areas to avoid, and where to go when food is scarce. Keep in mind that orcas can live as long as humans. A whale named Granny from the Salish Sea in the Northeast Pacific, is estimated to be 103 years old, far, far beyond reproductive age. A theory called the "grandmother hypothesis" suggests that the life experience of these mature females is so important that, evolutionarily, they contribute to the reproductive success of their pod even after they go stop reproducing. Of all the animals in the world only humans, pilot whales, and orcas are known to go through menopause, and their wonderful mothering may be why.

Courtesy: Mike Charest via Flickr

So who else is left? What other mother can compete with these two incredible species? Well the answer is simple, mine. My mom has been a big part of my life for as long as I've had it, and I want to dedicate this post to her this mother's day. Mom has always respected my goals and encouraged me to pursue the sea since I first responded "oceanographer!" when I was asked what I wanted to be when I grew up. 

The only thing that's changed in 21 years is that my brother 

doesn't fit in a dolphin anymore.

Mom and I always have wonderfully deep conversations about education and science, and she's been the number one supporter for the blog. I know that, like a giant Pacific octopus, my mom would give up everything to give her family a head start on life. But she'll also be around for years to come, to give me and my brother guidance, just like an orca matriarch. So since I know she's reading this, I just want to say thank you, thank you for everything, and Happy Mother's Day.

References:

No author, "Orcas of the Salish Sea, Part 1 & 2", The Orca Network. 

Accessed via: http://www.orcanetwork.org/Main/index.php categories_file=Natural%20History%20of%20Orcas%20-%20Part%201

Weiler, Nicholas, "Menopausal Killer Whales are Family Leaders", Science News, March 5th 2015. 

Accessed via: http://news.sciencemag.org/biology/2015/03/menopausal-killer-whales-are-family-leaders

Anderson, Roland C., Mather, Jennifer A., & Wood, James B., "Octopus: The Ocean's Intelligent Invertebrate",  Timber Press, May 21st 2010.

A Sea Lion Story

By now it's probably come across your computer screen at least once. The story may have even shown up in your physical paper. More than 1,800 California sea lion (Zalophus californianus) pups have shown up emaciated on the beaches of California since January. Unusual mortality events like this are most troubling to us because it's adorable baby animals that are suffering, so it's a good opportunity to draw awareness to ecosystem scale issues.

D'aww who's a good vector for a better understanding

 of ecology!? You are, yes you are!

Courtesy: Jaina via Flickr

So what do baby sea lions have to do with the ecosystem as a whole? Well ecosystems are all the living and non-living things in an area that interact with one another. This means that every piece in an ecosystem is significant to the others in some way. For example small fish are important to large predators, currents are important to plankton, and temperature is important to everyone. Each piece has direct effects on the others and those effects themselves interact.

On the surface (pun intended) starving sea lion pups seems to have a pretty straightforward cause. You would assume it's because there isn't enough of whatever it is sea lions eat. That's part of the story, but there's more to it. When baby seals and sea lions are first born they lack the thick blubber of their parents. Pups have to drink extremely rich milk to bulk up enough to survive on their own. California sea lion milk averages about 35% fat, that's about the same fat content as whipping cream, and about ten times the fat content of whole milk. Not only does the thick layer of blubber the pups develop help keep them warm it's important as an energy reserve when they first strike out on their own.

Despite what this sea lion seems to be telling you, Cronuts are not 

a viable source of energy reserves.

Courtesy: Makitani via Flickr

The most important prey for lactating mothers are anchovy, sardine, and hake. These fish live in large schools, so they're usually plentiful and they have extremely oily flesh; perfect producing rich milk. In the past there were very large fisheries for these species off of California. Think Cannery Row on Monterey Bay. However, we aren't taking too much of the sea lions' food away anymore because canned, oily fish have declined in popularity.

I can't imagine why...
Courtesy: dr.coop via Flickr

 What's happened is that for the last few years the waters around the Channel Islands, where the sea lions give birth, have been abnormally warm. Each of the fish the sea lions rely on are cold water species, in fact North Pacific anchovy won't go into water warmer than 62 degrees F. Since California's seas have been so warm the food fish have shifted themselves to colder waters. Sardines have been spawning farther offshore and other fish schools have moved north. These migrations have forced mother sea lions to hunt farther afield, and when their moms don't come back for extended periods of time, the pups set out on their own too early.

So where are the dad's in all this? Why don't we see adult males stranding in California? Well they're not there. Male and female sea lions both take on long migrations from British Columbia to California and back every year, but they have different schedules. Females head down to the breeding grounds first to give birth. Then males head down to meet up with the females once they're ready to mate again; about three weeks later. Being further north for longer has actually lead to boom times for male sea lions. At the mouth of the Columbia river between Washington State and Oregon more than ten times the usual number of males have been hanging out. They came in for this year's copious smelt run and are fattening up to make the trip south to the rookeries. Males need a lot of mass and energy reserves to defend territories on beaches which they won't leave and thus don't eat for several weeks.

   "I'll calm when I haven't gone twelve days without food!"
Courtesy: Bridget Samuels via Flickr

So that's the story. Warm water pooling at the surface has pushed forage fish away from the Channel Islands. This means that female California sea lions have to travel farther to find food that makes rich enough milk for their babies. These longer trips mean that many young are leaving the rookeries too early, and are washing up along the shore. All the while, farther north, males are enjoying a greater supply of food than ever. The biological needs of its inhabitants, and the physical characteristics of the ocean come together to tell the complex story of an ecosystem as long as a continent. We're able to discover the changes happening in the environment thanks to this single species.

Scientists aren't sure if the warming is caused by the changes happening to the global climate system, or if this is part of natural variations of the Pacific. Either way marine mammal stranding networks will need support in the near future. If you want to help one of the best things you can do is to remain informed about who's best prepared to help hungry or sick sea lion pups. There's a good list of organizations to contact and a lot of information here.

References:

"California Sea Lion (Zalophus Californianus)", NOAA Fisheries: Office of Protected Resources. Accessed via: http://www.nmfs.noaa.gov/pr/species/mammals/pinnipeds/californiasealion.htm

Bernton, Hal, "Boom Times on the Columbia for California Sea Lions", The Seattle Times, March 27th, 2015, Accessed via: http://www.seattletimes.com/seattle-news/boom-times-on-the-columbia-for-california-sea-lions/

"2013-2015 California Sea Lion Unusual Mortality Event in California", National Marine Fisheries Service Health and Stranding Reports,
Accessed via: http://www.nmfs.noaa.gov/pr/health/mmume/californiasealions2013.htm

Redman, Marianne, "The Pinnipeds: Seals, Sea Lions, and Walruses", pg 282, University of California Press, 1990.

Orr et al., 2011, "Intraspecific Comparison of Diet of California Sea Lions (Zalophus californianus) Assessed Using Fecal and Stable Isotope Analyses", Canadian Journal of Zoology, 89:109-122. 

Party Animals

Starting around this time every year, thousands flock to Florida's beaches with only one thing on their minds. They come from all along the Atlantic and the Gulf in droves to spend a few days getting wild with others they've barely met. That's right it's time for Spring B....eginning of loggerhead sea turtle nesting season.

What did you think I was talking about?

Courtesy: Daytona Spring Break via Flickr

Well actually spring break and loggerhead (Caretta caretta) nesting season don't match up perfectly. Thank god, can you imagine what kind of stuff a bunch of drunk bros would get up to with hundreds of sea turtles? Only the very first nesters come in during April, and the breeding season continues through the summer. Around the world's sub-tropical regions loggerheads return to the beaches they were born at to pass on their genes. The Southeast coast of the US hosts more loggerhead sea turtles than most other breeding regions around the world. Florida is especially important to these turtles. Ninety percent of all loggerheads born in the US nest in Florida.

Spring breakers and sea turtles have other things in common besides an intense urge to mate. They both have many stepped journeys that take them to the beaches of the southeast. After birth, young turtles head out to the open ocean and usually spend their first 5-7 years out at sea. It may seem a little odd for baby turtles to head out to the open ocean since there aren't a lot of places to hide, but there are far fewer predators out there. Plus the Atlantic has a unique region called the Sargasso sea which is named for its abundant floating fields of Sargassum (pronounced: sarj-ass-um) algae. Sargassum is perfect for little turtles because it's about the same color as they are and has a lot of spatial complexity for them to hide in. In these floating prairies, young loggerheads can grow fat on a diet of just about anything. Unlike other toddlers they aren't particularly picky and chow down on jellies, squid, shrimp, crabs, clams (even Tridacna), and fish. As they grow loggerheads rely on increasingly hearty prey so, like a college student raiding your fridge when he/she comes home for the summer, the turtles return to more abundant coastal waters to feed.

"Mom! Mom! You need to run to Costco again!"
Courtesy: rosepetal236 via Flickr


But how do the turtles find their way? Human college students have the benefit of Google maps and Expedia, but loggerheads' flippers make it hard to type. Instead sea turtles use the magnetic field of the earth to navigate. To understand how this works we need to know a little bit about the magnetic field itself.

Beneath the planet's mantle, but above the very center is a region called the outer core. The outer core is made of liquid iron mixtures and it moves around in loops thanks to the heat put out by the inner core. The conductive nature of the iron ensures that as the mixture moves around it generates electrical current, which in turn creates a magnetic field. The planet's magnetic field varies in several ways across the surface of the earth. It has an angle relative to the center of the planet that becomes steeper the closer you get to the poles. The magnetic field also varies in its strength changing along seemingly more random lines (It's weakest around South America and strongest around Siberia and the ocean south of Australia). If you can somehow detect these different lines of magnetism (called isolines) you can use them to figure out where you are on the planet, just like you would use lines of latitude and longitude.

"Stop asking me to pull over, I know exactly where we are."
Courtesy: Wendell Reed via Flickr

Amazingly scientists have enough behavioral evidence to confidently say that turtles navigate by detecting the earth's magnetic field, but don't have enough evidence to figure out exactly how they do it. The problem is it's easy to do experiments and scan data to see where turtles are going, but it's really hard to find possibly microscopic structures that sense magnetism. Perhaps the most compelling way animals might detect isolines is by having evenly spaced crystals of magnetite in their bodies. Magnetite is an iron mineral that has magnetic north and south poles, just like man made magnets. If a series of magnetite crystals is laid out in a line then they'll push away from each other when they're turned perpendicular to a magnetic field, but pull towards one another if they're lined up with it. Magnetite has been found in salmon, several species of birds, and sea turtles, all of which are highly migratory. Scientists think these animals might be able to gauge how much the crystals are pulling or pushing on one another to figure out how isolines are oriented.

Orienting themselves by magnetic fields is so important to loggerheads that they familiarize themselves with the unique magnetic coordinates of their home beach as they hatch. Then as the turtles return, if the isolines have shifted which they often do, the turtles will dig nests away from their birth place.

Despite their incredible abilities loggerheads are an endangered species. Their biggest threat is coastal development and negative interactions with humans since they prefer the same beaches we do. So for anyone out there planning a trip to Florida this spring break; remember that loggerhead turtles are there to have a good time too. If we treat each other with respect then humans and turtles can all have as much fun as this kid:

References:

Brothers, J. Roger, & Lohmann, Kenneth J., "Evidence for Geomagnetic Imprinting and Magnetic Navigation in the Natal Homing of Sea Turtles", Current Biology, Vol 25 Issue 3, 2015, DOI 10.1016/j.cub.2014.12.035. Accessed via:

http://www.cell.com/current-biology/fulltext/S0960-9822(14)01638-8

Lohmann, Kenneth J. & Johnson, Sonke, "The Neurobiology of Magnetoreception in Vertebrate Animals", Trends in Neuroscience, No. 23, 2000. Accessed via:

http://www.unc.edu/depts/geomag/PDFGeomag/TINSreview.pdf

The Earth's Magnetic Field, University of North Carolina's Oceanweb. Accessed via: http://www.unc.edu/depts/oceanweb/turtles/juvenilemap/EarthMF.html

"Caretta caretta, Loggerhead Sea Turtle"
The Encyclopedia of Life
Accessed via: http://eol.org/pages/1056566/details

A Clam for Ken Kesey

"That's a CLAM!?" This reaction to a particular animal is almost guaranteed when people look at them for the first time. Check it out.

Oh man, who just leaves a tie-dye shirt laying around on a coral reef?
Courtesy: Nick Hobgood via Flickr

Okay first off, that looks nothing like what belongs in my chowder. Second, this animal just goes to prove that the 60's got to everyone. So where does counter-culture clam come from and why's it so psychedelic? Editor's Note: This post is greatly improved when accompanied by Strawberry Alarm Clock's: Incense and Peppermints, or your own favorite psychedelic rock song.

Well what you're looking at is a Tridacna (pronounced: Tri-dack-na) clam. They're more commonly called giant clams, but I don't really like that name because not all of them are giant. In fact one species, Tridacna maxima, has the common name "small giant clam"; that's just silly so were gonna stick with their scientific name for this post. Anyway Tridacna don't look much like their relatives, but all the pieces are still there. They have heavy rippled shells like their cousins the cockles, and the part that you see sticking out is their mantle (the body of a mollusk) and their siphons (The channels clams use to feed and breathe). These combined anatomical parts are what make up the "meat" of the clam that we eat.

Plankton filled water flows into the hole on the right, and strained 
water flows out of the tube on the left.
Courtesy edgeplot via Flickr

Tridacna clams live on coral reefs in the tropical Western Pacific. Once they settle out from the plankton they spend their entire lives in that single spot. They don't dig into the ground, but instead let it all hang out. Truly these bivalves (animals with two shells) have gotten the hippy lifestyle down pat.

In fact it turns out that Tridacna's trippy colors and patterns are essential to its survival. The reason Tridacna don't dig into the sand is that they're part of a self sustaining commune. Just like the stony corals around them; these mollusks host symbiotic algae under their skin. In order for the algae to photosynthesize they need to be exposed to the sun. The hinge of the clam's shell is heavier than the opening, so it can tilt face up and spend the daylight hours with its skin spread out in the light. The algae get protection from consumers, and the clam gets nutrients without having to feed. Having a backup way to get your food is especially helpful on coral reefs because the water around them is usually lacking in plankton. Completely clear water is great for snorklers' ability to see, but not so great for filter feeders' ability to eat.

"Come on baby light my zooxanthellae" -Jim Molluskson
Courtesy: Eric Johnson via the NOAA Photo Library

Now as anyone who's forgotten sun screen on a tropical vacation can attest, the sun at the equator is incredibly strong. Solar radiation in the middle of the day is so intense that photosynthesis can actually decrease as the clam's symbiotic algae try to protect themselves from sun burn. But this is a collective man, and the clam does its part to help the algae function efficiently.

The algal cells under the clam's skin are arranged in stacked towers, which is confusing because that means the cells on top shade out those below them. To counter this Tridacna have their own cool cells called iridiocytes (pronounced: ear-id-ee-oh-sites) which bend light in different directions. The iridiocytes reflect yellow and green light (which aren't used by the algae) away from the stacks, and reflect blue and red light (which are useful) towards them. Essentially the iridiocytes screen out the best light for the algae, soften its intensity, and evenly distribute it across the stacks of cells.

The combination of colorful algae and reflected light come together to create the mind expanding visual experience of looking at a Tridacna's skin. Cameras can't really capture how magnificently colored these animals are, so I really encourage you all to take a trip to your local aquarium and see them for yourselves. But here's another picture to tide you over 'til then.

  Couretsy: Nick Hobgood via Flickr

References:

Holt et al., "Photsymbiotic giant clams are transformers of solar flux", Journal of the Royal Society Interface, Oct. 2014, DOI 10.1098/rsif.2014.0678 Accessed via:

http://rsif.royalsocietypublishing.org/content/11/101/20140678 

Soo, Pamela & Todd, Peter A., "The behaviour of giant clams (Bivalvia: Cardiidae: Tridacninae)", Marine Biology, 2014, DOI 10.1007/s00227-014-2545-0 Accessed via:

http://link.springer.com/article/10.1007/s00227-014-2545-0/fulltext.html

Over the Moon...fish

If you're at all curious about the ocean, and let's face it you're reading this blog so you probably are, you're most like likely aware of the mola mola. Molas are also called sunfish thanks to their penchant for lounging at the surface like beach goers looking for a tan. 

That's fair, this is about what my thighs look like the first 

time I go out in shorts every year.

Courtesy: Sandip Bhattacharya via Flickr

So if there are sunfish out there, are there moonfish? That may sound like the kind of lame joke your uncle might make at a family dinner, but it's actually a valid question. And yes there are a couple of species commonly called moonfish. My favorite of these, and an animal I only discovered recently, is the opah (Lampris spp.). Opah look a little like mola, but they're completely unrelated.

Oooo, shouldn't have gone with the spray-on tan.

This fish is incredible. Believe it or not they're related to oarfish. If you've never seen them before, oarfish are anything but round and squat. In fact the giant oarfish (Regalecus glesne) is the longest of any bony fish, usually growing to 8 meters. It's believed that giant oarfish originated the legends of giant sea serpents. While they're generally pretty different; if you look at opah and the oarfish (dibs on the band name) side by side you can see a bit of a resemblance.

Talk about awkward family photos.

From Field Book of Giant Fishes 1949 courtesy: Biodiversity Heritage Library 

Both fish have those large dorsal (on their back) fins with a large crest in the front. They've also got long pelvic fins extending down from their bodies. It's going to sound incredibly unscientific to describe it this way but they're also both very shiny. The scales of these fishes are so reflective that their group name (Lampriformes) means the shapes of light. That reflectivity is really useful in both fishes' habitat, the open ocean.

Okay, so why are we not talking the sea serpent one? The opah just looks like someone took a belt sander to the edges of a tuna. Its tail is so small compared to the rest of its body it doesn't even look like it would help the opah swim. Ah, you're right imaginary snarky reader! Opah don't use their tail fin to propel themselves through the water. Instead they use their pectoral fins, flapping them up and down like a penguin! They're also massive, the biggest opah ever caught weighed over 300lbs. Yet despite their size and stubby looking fins opah have been recorded speeding away from predators at four meters per second. That's about twice as fast as most people jog.

In order to move all that mass around opah have powerful muscles behind their pectoral fins. The muscles are so burly that they look, and apparently taste, more like beef than fish; even though the rest of the opah's muscles are similar to those of tuna.

"Moo?"
Courtesy: Io [Public domain], via Wikimedia Commons

It's kind of incredible that we have a lot of information about what Opah taste like, and you can find plenty of recipes online, because we hardly know anything about their biology and life history. Opah live in deep water, rarely coming to anything shallower than 50 meters and they don't live in schools. Both those things make them especially hard to study. It doesn't help that during the day when we humans like to be awake, opah spend time at the deepest parts of their range foraging mostly for squid.

Most encounters with opah come from fisher people long-lining for tuna. Long-lining is a fishing technique where several-hundred meter lengths of line are dropped down covered in hundreds of baited hooks. Inevitably something other than the target species gets caught; thinking they're snagging a free meal. This is referred to as bycatch, and many bycatch species aren't commercially valuable, so they're thrown back dead. Fortunately for fishers opahs' tasty meat makes them very valuable and they're able to keep and sell them. You can watch some guys in Hawaii filleting an opah in the video below. Skip ahead to the 2:50 mark to get past the local TV shenanigans, or enjoy the dorky jokes and watch the whole thing.

The thing is we don't know how this catch affects the opah population. Some people think they're safe because there isn't a targeted fishery, and others think we don't know enough to say whether they're being seriously harmed or not. The Monterey Bay Aquarium's seafood watch program, which is well researched, recommends avoiding eating opah from international sources, and only occasionally enjoying those caught in US waters. This is because the US has some of the best fisheries management in the world, and lots is being done to cut down on bycatch.

References:

Lee, Jane, "Rarely Seen Moonfish, Size of Manhole Cover, Caught on Camera." National Geographic: Weird and Wild, February 5th, 2015

McClain et al., "Sizing Ocean Giants: Patterns of Intraspecific Size Variation in Marine Megafauna", PeerJ, 2015, DOI: 10.7717/peerj.715, Accessed via: https://peerj.com/articles/715/

Polovina, Hawn, & Abecassis, "Vertical Movement and Habitat of Opah (Lampris Guttatus) in the Central North Pacific Recorded with Pop-up Archival Tags.", Marine Biology, 2007 DOI: 10.1007/s00227-007-0801-2

"Order Summary for Lampriformes", Fishbase, 

Accessed via: http://www.fishbase.org/Summary/OrdersSummary.php?order=Lampriformes

What is a Seahawk Anyway?

You may or may not have seen that Chris Evans (Captain America) and Chris Pratt (Star Lord) got into a discussion on twitter over who would win the NFL championship today (I can't legally say the name of the event due to copyrights, yay!). Depending on which team wins the big game; one of their superhero personas will show up at non-profit for children with cancer in the other's hometown. Chris Pratt is from North of Seattle, and Chris Evans is from Boston. During the exchange Chris Evans asked a question that's actually pretty common even here in the land of the 12th Man. #whatisaseahawkanyway? Good question Chris, I think this week we'll answer that.

Seahawk (Superbowli repetensis)

It's not always the case with sports emblems, but the seahawk is actually surprisingly accurate to it's namesake.

 You were expecting it to be blue weren't you?

Courtesy: vladeb via Flickr

That bird is an osprey (Pandion haliaetus) and some of its alternative common names are: fish hawk, fishing eagle, and sea hawk. Now don't me started on the hilarious missed opportunity when we didn't call the team the fishawks, but otherwise this bird of prey is a powerful emblem for my home team.

If you feel like you've seen this bird before you probably have. Osprey are distributed world wide, from North to South America, and from Europe across Asia to Australia. The only place where these birds don't winter or breed is in Antarctica. There's only one requirement for these raptors to survive somewhere; fish. 

Osprey are almost exclusively piscivorous (piss-i-vore-us), not unlike that guy everyone knows who claims to be vegetarian, but doesn't count fish for some reason. Fish approaches 100% of their diet with occasional hors d'oeuvres of reptiles, rodents, and small mammals. The grace and power with which osprey catch their prey is astonishing. Their adaptations for hunting would make them pretty great football players as well.

Ugh this guy's Endzone celebration is really weird...

Courtesy: David Mills via Flickr

Osprey begin their hunts by circling above the water searching for the right place to strike. Not unlike Russell Wilson in the pocket, an osprey's eyes are perfectly adapted to find their target in all sorts of weather. The dark bars around their eyes help reduce glare (the charcoal football players use does the same thing) so they can see into the water. Once they've spotted a fish they have a couple ways they can catch it. There's the Richard Sherman style snag where they swoop down and snatch up their prey without getting touched by the water. You may have seen bald eagles do the same type of catch. Or they can go Beast Mode and crash directly into the water, talons outstretched in front of them, penetrating the surface to about 3 feet. This type of hunting is unique to osprey because most birds of prey can't scramble back to flight after getting wet. You can see both styles of hunting in this great video from Wildscreen.

They are so good at holding on to struggling fish because their talons are covered in minute hooks. These dig into the fish and make sure the osprey never fumbles. They also have another unique adaptation that allows them to get back to the air; wrists. They can bend their wings at a joint most other birds can't and that allows them to get lift straight out of the water from a dead stop.

Oh, Wilson's lost in the scrum at the line of scrimmage.

Courtesy: Jeff Bosco via Flickr

But wait he's managed to scramble out for a five yard gain!

Courtesy: Michael Utin via Flickr

So what are seahawks anyway? They're a unique and well adapted predator with all the skills necessary to dominate in almost any environment. Also they're a bird.

References:

Flemming, Stephen, & Smith, Peter, "Environmental Influences on Osprey Foraging in Northeastern Nova Scotia", Journal of Raptor Research, 24(3):64-67, 1990

Accessed via: https://sora.unm.edu/sites/default/files/journals/jrr/v024n03/p00064-p00067.pdf

"Pandion haliaetus, Osprey"

The Encyclopedia of Life

Accessed via: http://eol.org/pages/1049145/details

"Pandion haliaetus"

US Forest Service

Accessed via: http://www.fs.fed.us/database/feis/animals/bird/paha/all.html

On the Origin of Fish Face

Fish face. It's one of the first impressions we do of an animal, and the second you say those words almost everyone knows what you're talking about. Hands at the side of your head, cheeks sucked in, lips puckered, and moving your lips open and closed.

Yeah that's the one! Not really sure how the top hat fits in, but whatever.

Courtesy: Mark Norman Francis via Flickr

Opening and closing their mouth over and over is characteristic of many of the bony fish that we see most often, especially gold fish. Why are they doing that? Well they're breathing, and we're just seeing them getting water into their bodies. It's a bit like your stomach or chest going up and down as you breathe. When you make a fish face your hands on the side of your head moving with your breathing are mimicking an important part of the bony fish breathing system. It's not the fins (although I know that's what of lot of people are mimicking), and it's not technically the gills, it's the gill cover. It might seem like a silly distinction, but in fish the gill cover is as different from the gills as your nostrils are from your lungs. If it helps you can call the gill cover by its more scientific name, the operculum (oh-perk-you-lum).

To breathe, the opercula (plural) close and the fish creates negative pressure to pull water into its mouth. Then the mouth closes and the opercula open pushing water across the gills and out the fish's body. The gills themselves though, are the coolest part of this system.

This is either a fish gill or someone scalped Ronald McDonald.

Courtesy: Allan Reyes via Flickr

Gills are really amazing because they take huge amount of surface area and bundle it into a tiny package. One study found that Atlantic horse mackerel (Trachurus trachurus) can have 14 square meters of surface on their gills! That's a greater area than the floor plan of this guy's house, all packed into a 70cm long fish. How is that possible? Each of those red filaments coming off of that yellow arch are covered in microscopic sheets called lamellae (lam-ell-ay). There are a ton of filaments on each arch and even more lamellae on each filament. It's just another great example of how tiny things can really add up in surprising ways.

Scanning electron micrographs of filaments on the left and lamellae on the right

Courtesy: Evans et al. 2005

All of that surface area is very important to the fish's ability to breathe underwater. Fish don't actually breathe the water itself. It would take a huge amount of energy to break water molecules apart to get at the oxygen, so instead animals with gills breathe tiny bubbles of gas dissolved in the water. If you can't picture that, think about a soda bottle. None of the bubbles are visible until you take the cap off the bottle. Just like the horrifying amount of sugar in there; the bubbles are really small and surrounded by water. When the cap comes off the tiny bubbles expand, slam into each other, make bigger bubbles, and escape. 

The problem is that there's only a fraction of the oxygen available in air, in the water. So gills actually need to be more efficient than lungs at removing oxygen from their surroundings All of those lamellae are in contact with the water and have deoxygenated blood running just under their surface (that's why they're dark red). The blood has less oxygen in it than the water nearby so the oxygen moves from the water into the blood. Nature doesn't care for an uneven distribution. 

Communist implications of nature aside, it's a really efficient system for getting an essential chemical into the body. It's also great for getting waste out of the fish's body. Not only can CO2 leave through the gills, but other waste as well, nitrogen based wastes like ammonia especially. Even though fish do have kidneys that process waste; the gills are just so damn efficient at exchanging chemicals with the water that they actually excrete most of the fish's nitrogenous waste. In some species up to 80% of the ammonia and urea are excreted through the gills. Imagine if we only had to pee one fifth as often because we breathed our waste out. Netflix binges would be so much easier.

"Oh god! Is that what all these warm spots are?"

Courtesy: Alex Derr via Flickr

There's one more question I want to pose to you all this week. If fish breathe gas inside the water, why do they suffocate in dry air? It could be that their gills need to be wet to work. Which makes sense since our lungs are wet and protected from outside. But there's more to it than that. It could also be that it's harder for gasses and materials to move between two different media, in this case gas and liquid, which is also true. But one of the most significant reasons is that when a fish comes out of water the filaments and lamellae aren't buoyed up by the water and they lay flat on one another. When they bunch up, the surface area on the gills decreases, and the efficiency benefit is lost. So if you're doing catch and release fishing and you take your fish out of the water for a minute, slowly swish them back and forth a little in the water a little to help get their gills unstuck. That way he/she will stay healthy and have lots of babies so you can keep coming back every year.

References:

Evans et al., "The Multifunctional Fish Gill: Dominant Site of Gas Exchange, Osmoregulation, Acid-Base Regulation, and Excretion of Nitrogenous Waste.", Physiological Reviews, Vol. 85 No. 1, 2005, DOI: 10.1152/physrev.00050.2003

Accessed via: http://physrev.physiology.org/content/85/1/97

Hughes, G.M., "The Dimensions of Fish Gills in Relation to Their Function.", Journal of Experimental Biology, 45, 177-195, 1966

Accessed via: http://jeb.biologists.org/content/45/1/177.full.pdf

"Trachurus trachurus, Horse Mackerel" 

Encyclopedia of Life, Accessed via: http://eol.org/pages/206048/details