Mom! They're Copying Me!

The old saying goes: "Don't pretend to be something you're not." It's great advice for humans trying to navigate the complexities of identity and our place in society.

I'm lookin' at you, High School Me!

However, if you're a small creature that's constantly at risk of being eaten, pretending to be something else might not be so bad. 

There's familiar examples of passive camouflage everywhere in the ocean. Sea Dragons look like loose, floating kelp; stonefish lie as unmoving as their namesakes on the bottom; grunt sculpins are nearly indistinguishable from a barnacle when they're still. There are even animals that actively camouflage to look like their environment. The many species of decorator crabs attach seaweed, sponges, hydroids, and any other flappy materials to their shell to blend in with their surroundings.

Microscopic hooks cover the crab's shell to facilitate camouflage

Courtesy: Ruth Hartnup via Flickr, and

Monique Salazar and W. Randy Brooks via Journal of Marine Science

But sometimes blending into the background isn't enough. Sometimes, you've got to do more than look the part. Sometimes you have to live your role to complete the illusion. Enter the cephalopods.

Octopus, squid, cuttlefish, and nautilus are all cephalopods (pronounced: sef-a-lo-pod). Cephs are probably the most intelligent and adaptable invertebrates in the world. A closer look at their anatomy can help us understand why. Cephalopods don't have claws or spines; they're not very fast; they have a sharp beak, but they have to get close to use it; and except for nautiluses cephs don't have a hard shell to protect their squishy, protein-rich bodies. So what do you do when you lack anatomical defenses? You get smart.

The most famous of this class to have the smarts to watch another animal and copy its behavior is the appropriately named mimic octopus (Thaumoctopus mimicus).

<in a nasally mocking voice> "watch another animal and copy its

behavior is the appropriately named mimic octopus"

Courtesy: Rickard Zerpe via Flickr

Dude, don't copy me that's ridiculous.

"Don't copy me that's ridiculous."

Courtesy: Avi Alpert via Flickr

<The following was typed very fast so the mimic octopus couldn't possibly copy it quick enough, and we can all actually learn something>

Mimic octopuses are found on sandy bottoms in the waters around Indonesia, the Philippines, and Papua New Guinea. These sandy and silty bottom habitats have few rocks, little animal growth, and minimal algae to hide among. While mimic octos can change their colors to match the background just as well as their cousins; movement tends to break the illusion. Other octopus species take advantage of rocky reefs or coral crevasses to slink along unnoticed while in motion, but mimics don't have that luxury. They also typically have to swim farther and more often than octopuses in other habitats because their prey isn't concentrated in a small area. A swimming octopus is very distinct, so mimics exactly copy the swimming behavior of flounder to conceal their true nature. They bend all their arms around and cluster them together so their eyes are sticking up in front of a big flat disk. As their arms trail, the ends flap just like the fins of a flatfish. The octopuses even stop and start moving with the same frequency as flounders all while hugging the contours of the rippled bottom.

We don't know why, but sometimes the mimic octopus will keep its distinct pattern while moving like a flounder and sometimes it will change to the fish's usual coloration.

Courtesy: Klaus Stiefel and Bernard Dupont via Flickr

The internet is full of reputed stories of mimic octos copying other species as well. While reports of mimic octopuses mimicking lionfish, sea snakes, and stingrays are out there we should remember that octopuses evolved entirely without our perceptions in mind. This means that what may clearly look like a lionfish to us, may look nothing like it to a grouper hungry for a bite of octopus arm. However, it may be that the mimics' strategy is just to look like "not an octopus", and whatever other creatures they see, they try and copy.

Amazingly mimic octopuses aren't the only species of octopuses to mimic other creatures. Living in the same waters as mimics the excitingly named "blandopus", which has which hasn't been formally described yet, also copies flounder. And if you Atlantic Ocean folks have been feeling left out, don't worry. The Caribbean has a copy-cat octo as well. Atlantic longarm octopuses (Macrotritopus defilippi) live in a very similar habitat to mimics and blandopus, and also engage in flat fish plagiarism.

Some species just have no regard for copyright law.

Courtesy: Wayne via Flickr 

Clearly impersonating another animal is an effective way to avoid becoming someone's lunch. But can cephalopods use mimicry to catch their own prey?

Just off the coast of southern Brazil; in the southern summers of 1999, 2000, and 2001 a pair of scientists used lights shined from a boat to attract zooplankton. Light attractants like this are an important tool in many fisheries, particularly those for squid. Rodrigo Silvestre Martins and Jose Angel Alvarez Perez wanted to study how a community of predators and prey develop under these lights. Who's eating whom, how are they going about catching one another, and what could that mean for fisheries conservation? The researchers found that a column of animals, gradually increasing in size, formed under the lights. The smallest zooplankton were near the surface, and as you descended  progressively larger predators lurked, waiting for a chance to strike at the prey above them.

Lurking in the shadows is pretty typical behavior for any predator, but one squid species' actions caught Martins and Perez by surprise. Atlantic brief squid (Lolliguncula brevis) are an estuary specialized squid that eat small schooling fish like anchovy and sardines. During Perez and Martins' study they watched brief squid regularly mimic the shape, color patterns, and swimming behavior of anchovies in order to get inside their schools without being noticed before striking.

Brief squid isn't a cool enough name for these masters of infiltration.
I propose we call them "subterfuge squid" from now on.
Courtesy: NOAA Photo Library via Flickr 

Now, squid aren't the only cephalopods to pantomime another animal in order to get close to prey. We've found one species of cuttlefish engages in a similar behavior to creep up on reef fish.

Pharaoh cuttlefish (Sepia pharaonis) are a widespread, small cuttlefish found throughout the warm waters of the Indian and Western Pacific Oceans. In 2011 a team of Japanese researchers noticed their cuttles doing something weird when they were placed in a large open tank for an experiment. The cuttlefish pushed together their upper pair of arms and colored them like eyes on the end of stalks. Then they set their other arms at odd, jointed angles and started twitching them, seemingly at random. Lastly they colored their mantle a shade lighter than all of their arms. The whole illusion came together to look exactly like a hermit crab.

In case the video widget doesn't work, click here to watch the pharaoh cuttles in action; it's astonishing. The research team thought maybe the cuttlefish were mimicking to protect themselves from potential predators when exposed in a large barren tank; kind of like mimic octopuses pretending to be other animals when they're moving in the open. But the scientists were curious if faking crabbiness (definitely the scientific term) could also help the cuttles catch prey like brief squid pretending to be anchovies.

So in 2013 they collected more pharaoh cuttlefish and put them in a tank with small tropical damselfish. The cuttles that pretended to be crabs got closer to the schools and caught twice as many fish as those that hunted while acting like cuttlefish! So yeah, I'd say that's an effective hunting strategy.

As we begin to look closer at cephalopods we're starting to understand just how diverse and seemingly intelligent their behavior is. Mimicries like these are just a sample of the ways octopus and their cousins use their adaptable camouflage. So maybe pretending to be something you're not isn't always bad. Maybe we shouldn't deal in absolutes all the time and recognize that there's advantages and disadvantages to lots of behaviors and life styles. There's a lot to be learned still about cephalopods, but there's also a lot to be learned from them.

References:

Hanlon, Roger T., Watson, Anya C., & Barbosa, Alexander, "A 'Mimic Octopus' in the Atlantic: Flatfish Mimicry and Camouflage by Macrotritopus defilippi", Biological Bulletin, 218: 15-24, Feb. 2010.
Accessed via: http://www.journals.uchicago.edu/doi/10.1086/BBLv218n1p15

Hanlon, Roger T., Conroy, Lou-Anne, & Forsythe, John W., "Mimicry and Foraging Behaviour(sic) of Two Tropical Sand-flat Octopuses of North Sulawesi, Indonesia", Biological Journal of the Linnean Society, Jan. 2008.
Accessed via: https://academic.oup.com/biolinnean/article/93/1/23/2701347

Martins, Rodrigo Silvestre & Perez, Jose Angel Alvarez, "Cephalopods and Fish Attracted by Night Lights in Coastal Shallow-waters, off Southern Brazil, with the Description of Squid and Fish Behavior", Revista de Etologia, Vol. 8 No. 1 Pg. 27-34, 2006.

Accessed via http://pepsic.bvsalud.org/pdf/reto/v8n1/v8n1a03.pdf

Okamoto et Al., "Unique Arm-flapping Behavior of the Pharaoh Cuttlefish, Sepia pharaonis: putative Mimicry of a Hermit Crab", Japan Ethological Society and Springer Japan, May 2017.

Accessed via: https://link.springer.com/article/10.1007/s10164-017-0519-7

Basking Case

What follows is a cautionary tale. A story about acting out in frustration; of letting passions get the better of our collective judgement. A yarn of life, economy, adventure, and...tourists.

Folks living in major coastal towns around the world know the story. As the days lengthen the sun's rays warm the air and the scent of dry grass drifts in the breeze. Locals finally get on the water as the rains and long dark of winter are left behind. But that's when they come: massive, constantly in the way, slowly moving in impassable groups, gorging themselves on an all you can eat buffet. 

Courtesy: Devin Braun via Flickr 

I am, of course, talking about basking sharks (Cetorhinus maximus). 

-"Hey, Kool-Aid"

-"Oh Yeah!" 

Courtesy: jidanchaomian via Flickr

Basking sharks and cruise ship travelers may not seem to have much in common at first, but diving in (Ha! Ocean puns) to their life history reveals some surprising commonalities.

Baskers are the second largest fish species in the world, growing to average lengths of 15-20 feet, but they can get as long as 30. Because they're so big; a single flick of a basking shark's tail moves a lot of water and thus their streamlined bodies are propelled smoothly along with very little effort. This energy efficient movement allows basking sharks to travel great distances through temperate seas. One shark was tagged in late June of 2007 between Ireland and the UK, and had traveled all the way across the Atlantic to south of Greenland by early August. Like other related sharks that make long treks, basking sharks are cruising in search of food. But these massive fish aren't hunting for seals or other large prey; they're cruising along, mouths agape, straining plankton from the water. The filters on their gills are so good at collecting particles, yet remaining unclogged, that they're even inspiring engineers designing industrial and commercial water and air filters.

Basking sharks migrate seasonally across the ocean, and daily up and down in the water column following their favorite food: calanid copepods (pronounced: ko-peh-pods).

Copepods are rich in fats despite their constant failed attempts
at stealing the Krabby Patty secret formula.
Courtesy: DFO via WOrld Register of Marine Species

During the winter these planktonic crustaceans tend to hang out deeper in the water and farther out to sea, so baskers do the same. During the summer, copepod populations explode near shore as lengthening days cause massive blooms of phytoplankton for the copepods to graze on. Basking sharks head shoreward just ahead of this explosion of life to catch the bloom right as it begins and optimize their own feeding. Like most other zooplankton, copepods also participate in the planet's largest migration. During the day they descend to avoid active predators at the surface, and at night they come up to the phytoplankton rich layer that formed while the sun was high. Typically basking sharks do the same daily vertical migration, but occasionally tons of copepod predators called arrow worms will show up at the surface at night. This unexpected pulse of predators drives the majority of the copepods, and consequently the basking sharks, deep when we'd expect them to be shallow.  So not only do basking sharks show up in the inland waters of the far north and south like cruise ships and their passengers, but they also predictably attend to the abundance of the buffet at the times of day it's most well stocked.

Basking sharks' feeding and travel habits aren't the only ways they jive with tourists. As their name implies, basking sharks often hang out in the sun not doing much. Since the sharks already have a pretty bitchin', deep-brown tan they must not be longing to soak up rays. Nope, it's that layer of copepods again. Because there's so much food at the surface, basking sharks don't have to move fast or far during the spring and summer blooms. The sharks are found in aggregations hundreds strong just lolling at the surface with their mouths open like they've fallen asleep sunbathing.

Okay I know there's a shark in this picture somewhere but...
Courtesy: candiche and Noodles and Beef via Flickr

These high concentrations of slow moving basking sharks occur in only a few places in the world. It's likely that these big shivers (the name for a group of sharks) show up in places like southern Chile, but we only know for sure that they happen in the Irish Sea, outside the Bay of Fundy, and historically in the Northwest Straits of the Salish Sea.

Just in case you're not from one of those places or didn't pay attention in geography

Now, you might have noticed that I said "historically" in the Salish Sea. In the past, basking sharks came to the region in droves every year to bathe in the Pacific Northwest sun and chow on the rich abundance of copepods in those waters. But like any pulse of summer tourists visiting a port; they were slow, in the way, and causing problems for traffic.

I'm lookin' at you; Pike Place!
Courtesy: Michael Munch via Flickr

As happens with anyone who deals with influxes of tourists too often; salmon fisher folk in British Columbia largely hated this yearly migration. The sharks were so numerous and slow that they frequently became entangled in salmon gill-nets. Basking sharks also have the same skin-teeth that other sharks possess, so when they thrashed to free themselves they often destroyed more of the net than just where they were caught.

Since much of the BC economy relied on salmon fishing at the time, basking sharks were listed as "Destructive Pests" by Canada's fisheries department in 1949. Six years later the department began an eradication program that, coupled with a commercial fishery for their skin and oil, did exactly as intended. Basking sharks were functionally extinct in the Salish Sea by the late 60s.

The Comox Post with its shark-slicing bow blade
was the pride of the program.
Courtesy: Popular Mechanics via Google Books

However attitudes towards basking sharks (and to a lesser degree cruise tourists) are changing. People better understand the role baskers play in the marine ecosystem as the massive end of a petite food chain. Ironically basking sharks now bring tourists to the Irish Sea and surrounding waters every year to watch their incredible shivers. Having basking sharks and cruise tourists around can greatly enhance the economies of northern port towns in the summer. And Lord knows we can use that extra cash for good beer and faux daylight to get us through the dreary mists of maritime winters.

There's also hope for the Salish Sea's population of basking sharks. They've been granted the protections that being listed as "endangered" under Canada's Species At Risk Act affords them since 2010. Baskers are also occasionally showing up in unexpected parts of the Salish Sea. In 2014 a basking shark gave a family out fishing a unique encounter when it basked about their boat for 15 minutes off of Edmonds, just 16 miles north of Seattle. No word on if the shark was planning to visit Pike Place.

" Excuse me, can you tell me how to get to the gum wall?"
Courtesy: Grace Coale via Q13 Fox

References:

Gore et al., "Transatlantic Migration and Deep Mid-ocean Diving by Basking Shark", Biology Letters: Marine Biology, Vol. 4 pg. 395-398, 2008.

Accessed via: http://rsbl.royalsocietypublishing.org/content/4/4/395

Lorch, Matt, "Close Encounter with Rare 25-foot Basking Shark in Puget Sound: "I didn't really feel scared, just excited", Q13 Fox News, Aug. 13th 2014

Accessed via: http://q13fox.com/2014/08/13/close-encounter-with-rare-25-foot-basking-shark-in-puget-sound-i-didnt-really-feel-scared-just-excited/

Pynn, Larry, "Rare B.C. Photograph of Endangered Basking Shark Shines Light on Change in Federal Attitudes", Vancouver Sun, Nov. 11th, 2013.

Accessed via: 

http://www.vancouversun.com/technology/Rare+photograph+endangered+basking+shark+shines+light+change+federal+attitudes/9152553/story.html

Sanderson et al., "Fish Mouths as Engineering Structures for Cross-step Vortical Filtration", Nature Communications, Vol. 7, Article #11092, 2016.

Accessed via: https://www.nature.com/articles/ncomms11092

Siders et al., "Seasonal Variation in the Spatial Distribution of Basking Sharks (Cetorhinus maximus) in the Lower Bay of Fundy, Canada", PLoS ONE, Vol 8 Issue 12, 2013.

Accessed via: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0082074

Sims et al., "Habitat-specific Normal and Reverse Diel Vertical Migrationin the Plankton-feeding Basking Shark", Journal of Animal Ecology, Vol. 74 pg. 755-761, 2005.

Accessed via: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2656.2005.00971.x/full

Going Solar

It seems like the news on energy these days is all about solar. Solar collectors, community solar programs, solar getting cheaper than fossil fuel. Solar, solar, solar. We humans may think we're hot stuff for figuring out how to harvest the energy from the sun for our own needs, but other animals have been using their own kinds of solar panels for eons.

In particular, corals and sea anemones have been acting as green power plants since the times of the earliest dinosaurs. Which is pretty clever when you consider they don't have a brain. Of all the photosynthetic cnidarians out there my favorite has got to be the Aggregating Anemone (Anthopleura elegantissima) AKA the Pink-tipped Anemone.

You can probably guess how it got those names.

Courtesy: Bureau of Land Management via Flickr

If you live on or have visited the Pacific coast of North America, you probably recognize this anemone. They're extremely common very high in the intertidal zone. Which means that if you've ever visited a rocky beach when the tide was even a little low, you've probably encountered these anemones. They're often found in large aggregations, hence the name. These mats of anemones would be astonishing just for their sheer number, but they're even more incredible when you realize each colony is a series of clones.

Have you ever had one of those days where you're so ambivalent about a decision that you wish you could just tear yourself in two and do both? Well aggregating anemones basically have that luxury. They're so good at restoring their tissues after damage that they can literally pull themselves in two different directions and split into separate anemones.

"I weigh a fraction of what I used to, thanks to the elgantissima 
weight loss program!"
Courtesy: Brocken Inaglory via Wikipedia

If the conditions on a particular rock are good enough; one anemone will make many clones, which will make many clones, and so on, and so on until entire sections of beach are covered in copies of the original. These colonies work together to make each individual anemone more successful. Some anemones will specialize in spawning and produce more eggs and sperm than the other clones. Anemones at the edge of the colony will grow more stinging cells than those toward the center, and act as warriors to defend the colony from predators and other aggregating anemones trying to horn in on their turf. If Lenin had a spirit animal, it was probably pink-tipped anemones.

Fight, fight, fight! The white bulbs are sacks of densely packed
stinging cells used to ward of predators and other anemone colonies.
Courtesy: Brocken Inaglory via Wikipedia

Okay so aggregating anemones are pretty cool on their own, but what do all these adaptations have to do with collecting solar energy? Everything. Just under the skin of aggregating anemones live colonies of dinoflagellates, single-celled algae, or both. In the southern portions of the anemone's range you only find dinoflagellates in their tissues, but further north you find a combination of algae and dinoflagellates. We believe that the dinoflagellates are better able to tolerate warm water, and that the algae may help the anemone collect more sun where the days are shorter in fall and winter.

Dinoflagellates (pronounced: dai-no-fla-jell-ates) are a confusing single-celled organism that isn't quite animal and isn't quite plant. Most are a single cell with a wavy appendage like a sperm tail called a flagella. Many can both consume food and produce it via photosynthesis. The dinoflagellates under the skin of aggregating anemones are exclusively photosynthesizers and they're only found living in the tissues of cnidarians.

These individual cells work like the individual panels on a solar array. When exposed to sunlight each cell produces carbon and oxygen, both essential ingredients for the chemistry of life in complex organisms. Aggregating anemones harvest these products from their photosynthetic roomates just like electrical engineers harvest electricity from photovoltaic panels. In turn the anemone maintains the solar power plant by producing carbon dioxide, and waste. Carbon dioxide, which the anemone breathes out, is an essential ingredient in photosynthesis, and animal waste is full of the nutrients plants crave.

The anemone's green-blue color actually comes from the algae
and dinoflagellates in the skin. This clear one probably lives in 
the shade of a large boulder and so doesn't host photosynthesizers.
Courtesy: Peter Pearsall/USFWS via Flickr

Now it's not as easy being a living solar farm as it is being a synthetic one. Human solar arrays can be made of glass and other materials that resist wear and tear, but anemones and their symbiotic solar cells are made of good old squishy, damageable protein.

In order for their symbionts to do photosynthesis, aggregating anemones have to live where there's plenty of sun, hence their high position in the intertidal. However, as any fair-skinned individual can attest, sunlight is loaded with ultraviolet radiation which wreaks havoc on organic tissues. In order survive exposure to all that radiation aggregating anemones have to possess some unique defenses. Thankfully the dinoflagellates secrete a chemical that coats the anemone's cells and acts as a sunscreen. The chemical absorbs the most dangerous parts of the UV and dissipates them as softer visible light.

Of course they say help comes to those who help themselves, and the anemone pulls its own weight in protecting its investments. Along the sides of aggregating anemones are little sticky bumps called verrucae (pronounced: ver-oo-key). The anemone uses its verrucae pick up particles of shell, sand, and other materials. These bits act like a big floppy sun hat to protect the anemone's sensitive skin.

Who Wore it Better? Sandy Beach Edition.
Couretsy: A. Strakey & Diane Main via Flickr

 Even though the anemones have solved the sun exposure problem, there's even more challenges to running a living solar facility. Photosynthesis produces oxygen, which is great if your tide pool is getting hot and losing gas to the atmosphere, but not so great if you're cells start to fall apart from oxidation. Oxygen is a really powerful molecule because it often comes in a form you might of heard of called a free radical. Free radical oxygen has characteristics that make it pull other molecules apart, which is why oxygen is toxic in high concentrations. So if the algae and dinoflagellates are phtosythesizing away, pumping free radical oxygen almost directly into their hosts cells, the anemone could die of oxygen poisoning. Thankfully the anemone's body produces high concentrations of chemicals that bind with free radical oxygen and render it harmless.

The final challenge for an organism trying to run a biological green power facility brings us back to where we started at the anemone's position along the shore. Living high up the beach means that a couple of times a day the tide is going to go out on you. If you're an animal that's normally adapted to living underwater that's a challenge. The shells and sand grains on the anemone's stalk will help block some of the desiccating effects of the dry air, but it's not always enough; so aggregating anemones hold their breath. As the tide recedes the anemones suck as much water as they can into their body cavity to keep them moist and oxygenated while the water is out. If you've ever touched an aggregating anemone and it squirted you, you know what I'm talking about. Careful though, as making them spray their water is kind of like telling your friend to hold their breath and then punching them in the gut. Sure its funny as the air or water comes rushing out, but the anemone/guy who just got punched is left very winded and uncomfortable.

"Anemone Punch" The new album from Olympia punk band: Cnidaria 
Courtesy: Ingrid Taylor via Flickr

More and more, engineers are drawing inspiration from nature for building materials that improve our daily lives. If the flippers of humpback whales can make wind turbines more efficient, maybe we can draw inspiration from nature's original solar plants to improve other areas of green infrastructure. It's a beautiful irony that the fight to save species from climate change might be resolved by looking at the very animals we're trying to protect.

References:

Furla et Al.. "The Symbiotic Anthazoan: A Physiological Chimera Between Alga and Animal", Integrative and Comparative Biology, vol. 45, issue 4, pg 594-604, 2005

Accessed via: https://academic.oup.com/icb/article/45/4/595/636401/The-Symbiotic-Anthozoan-A-Physiological-Chimera 

Lajeunesse, T.C., & Trench R.K., "Biogeography of Two Species of Symbiodinium (Freudenthal) Inhabiting the Intertidal Sea Anemone Anthopleura elegantissima (Brandt)", The Biological Bulletin, vol. 199, no. 2, October 2000

Siren Songs

Last week we looked at one of the most productive ecosystems on earth, sea grass prairies. Sea grass prairies house many animals that fill very similar ecological roles to terrestrial counterparts. The most notable, and tragically least discussed in the previous post, is the manatee. Thankfully manatees and their cousins are such a rich topic that they've earned their own post.

 Try not to look so excited, geez.

Courtesy Tracy Colson via Flickr

Almost everyone has heard that manatees are likely the source of mermaid legends, or at least were mistaken for mermaids after the legend had been around for a while. In fact the name of the manatee's order, Sirenia (pronounced: sih-ree-nee-uh), actually comes from the sirens that tempted Odysseus while he sailed from home after the Trojan War. Many people find it a bit surprising that such large, grey, and cowish looking animals could be mistaken for half women, half fish; but beyond sailor's missing home there's actually a decent reason sirens could have been mistaken for their namesake. Female sirenians have breasts in the exact same position that human females do. Add the fact that they nurse their young while floating vertically with their heads above water, and you can see how people could have made the mistake that there were aquatic humans.

Though manatees are often called sea cows; it's believed that sometime around 50 million years ago a close relative of elephants slipped into lakes and streams to feed on the rich grasses growing underwater. Over time these four-limbed sirens became more and more adapted to the life aquatic and their descendants spread out across the globe. Then as the earth cooled to today's more familiar state many sirenians went extinct, leaving us with only four species.

Unfortunately there isn't anywhere in the world where you can see all 

four species at once. This manatee quartet (dibs on the band name) is made 

up entirely of one species.

Courtesy: David Hinkel via Flickr 

All sirenians scour the river, lake, or sea floor searching for underwater grasses to eat. Other marine mammals eat meat, and so have access to copious amounts of fat and protein to keep their weights up and their bodies warm. Sirenians are the only herbivorous marine mammals so they have to eat about 10% of their weight every day. Quite a lot when you consider they can weigh between 500 and 800 lbs. One study found that a single sirenian needed about an acre of constantly regenerating sea grass per year in order to get the food they need.

Sirenian mouths are well adapted to consuming large quantities of plants.  On every species the mouth is turned downwards to the seabed so the siren can look ahead as it grazes. Their teeth are specialized for grinding up veggies and are constantly replaced with new ones as they wear down, just like a shark's!

Modern sirenians are all found in the fresh and nearshore salt waters of the tropics and sub-tropics. They're extremely intolerant of cold and will move out of waters that fall below about 68 degrees Fahrenheit (20C). This need for environmental warmth may be a consequence of having evolved during a much warmer period in Earth's history. Only one sirenian, the Steller's Sea Cow (Hydrodamalis gigas), managed to adapt to frigid waters and survive to the modern era, but believe it or not, we ate them all. 

In case you ever thought your drawing skills aren't good enough for natural history; 

this is thought to be the most accurate drawing of a Steller's sea cow because 

it's the only one we know was drawn from a live specimen

Courtesy: Public Domain via Wikimedia Commons

Steller's sea cows were discovered by westerners looking to hunt sea otters along the Aleutian Islands where food could be scarce. The scientist who first described them tells us that they ate more algae than sea grass, and that their forelimbs were curved instead of paddle shaped to allow them to pull themselves along in the shallows while grazing. What's particularly fascinating about these animals was just how big they were, some individuals were as long as an adult orca! That's a lot of manatee. Steller's sea cows were so slow, easily reached, and edible that they were gone about 17 years after their discovery. Sadly we'll never know if we did major detriment to this species while it was thriving in an isolated population, or if they were already nearing extinction naturally when we dealt the final blow. Fortunately there may still be time to save the sea cow's closest relative, the dugong (Dugong dugon).

Om Nom Nom Nom
Courtesy: Corrie Barklimore via Flickr

Dugongs (no, not the pokemon) are the most marine of the sirenia; meaning they spend all their time in salt or brackish (mixed salt and fresh) water. Their most noticeable distinction from manatees is their forked dolphin-like tail. Manatees have big, round, paddle-like tails that are useful for holding position in still water. While dugongs are wide spread across the tropical Indian and Western Pacific Ocean their populations are spotty, probably due to human alterations in their habitat. The largest herds live along the coast of Northern Australia and in the Arabian Gulf where sea grass beds are still large and healthy. The challenge for these sirens has been human development of beaches where sea grasses grow off shore. Unfortunately sea grasses grow off of exactly the kind of sandy, relaxing beaches humans like to put hotels and beach communities on. When land plants are taken away by construction; dirt and sand run into the nearshore smothering the prairies. Fertilizer runoff from agriculture and golf courses also causes quick-growing algae to out compete sea grass. So when you choose a place to stay during your tropical vacation, keep in mind the resort's potential impact on dugongs before you book a room.

Dugongs role as grazers is extremely important for sea grass prairies because they remove old grasses and fertilize new ones. As they browse, dugongs pull sea grass up by the roots creating noticeable  tracks of bare sand like someone set the lawnmower way too low. Like any herbivore dugongs make a lot of waste and as their poop falls into the furrows they've created in the grass it provides critical nutrients for the regeneration of the prairie.

Who else wishes it was possible to hire manatees to mow
your lawn instead of goats?
Courtesy: Ruth Hartnup via Flickr

The sirenian that is the next most comfortable in ocean is the West Indian Manatee (Trichechus manatus). West Indian Manatees are the most familiar and well-studied of all sirenians because they live in highly populated regions of North, Central, and South America. You may have heard of Florida and Antillean manatees in your travels, and those are legitimate, but they are names for distinct populations of West Indian Manatees. Antillean manatees are usually found in the Southern Caribbean, and Central and South America. You can probably guess where Florida manatees are most often found. For a deeper look at what makes a species, and how populations of one species can be distinct from one another without being totally different, check out the D&T posts "Celebrating Sculpin Speciation" and "Ghost Faced Killer (Whales)".

Most West Indian manatees split their time between fresh and salt water depending on the season. In Florida these manatees spend their winters huddled nears springs of warm water, and since the advent of modern electricity generation, the heated water outflows from power plants. As ocean temps warm up in the summer Florida manatees  spread out in search of lush prairies and can be found travelling as far north as Virginia! Interestingly, although as many as 500 manatees have been seen in one spot during the winter, they aren't particularly social. The mother-offspring bond is the strongest social connection in manatees. Young manatees will stay with their mothers for two years after they're born, learning where warm refuges and feeding grounds are located.

The green on his back is algae, kind of like the stuff that grows in sloth fur.
Courtesy: Keith Ramos via Flickr

The final two sirenians are the most river-adapted species, the Amazonian manatee (Trichechus inunguis) and the West African manatee (Trichchus senegalensis). Both can be found deep into large rivers in their respective continents. Amazonian manatees have stable populations as far up the Amazon water shed as Peru and Columbia, and West African manatees can be found living in lakes 200 miles inland from the sea. These manatees deal with particularly murky water compared to dugongs and West Indian manatees, so the sensitive bristles that cover all sirenians' bodies are especially important for finding food. It's kind of like if a cat had whiskers all over their body instead of just their face.

Yep, that's a baby Amazonian manatee. Commence squealing with delight
Courtesy: Harvey Barrison via Flickr

We know the least about African manatees because the humans of their homeland have struggled with colonialism and the unrest it often instills in the colonized. However, this chaos may actually benefit the manatees; as development in some countries where they're found has been slow. Without speed boats, big riverside properties, and erosion problems African manatees have fewer risks to their survival than sirens in more altered regions of the world.

Dugongs and manatees are one of the weirdest and most fascinating marine mammals on the planet. For every human that's encountered them it's as hard to resist the song of these sirens calling us to discover more about them. But unlike the sirens of Greek Myth, the lure of dugongs and manatees will bring every species to a healthier life and a richer planet.

References:

Mayaba, Theodore B., Kamla, Aristide T. & Self-Sullivan, Carlyn, "Using Pooled Local Expert Opinions (PLEO) to Discern Patterns in Sightings of Live and Dead Manatees (Trichechus senegalensis, Link 1785) in Lower Sanaga Basin, Cameroon", PLOS ONE, July 21st, 2015.   

Satizabal et Al., "Phylogeography and Sex-Biased Dispersal Across Riverine Manatee Populations (Trichechus inguinus and Trichechus manatus) in South America", PLOS ONE, December 20th, 2012.

Accessed via: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0052468

Sulzner et Al., "Health Assessment and Seroepidemiologic Survey of Potential Pathogens in Wild Antillean Manatees (Trichechus manatus manatus)", PLOS ONE, September 12th, 2012.

Accessed via: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0044517 

Macdonald, Nicole, "Dugong dugon- Dugong" Animal Diversity Web. Accessed via: http://animaldiversity.org/accounts/Dugong_dugon/#food_habits

Weinstein, Brett & Patton, James, "Hydrodamalis gigas- Steller's Sea Cow", Animal Diversity Web, Accessed via: http://animaldiversity.org/accounts/Hydrodamalis_gigas/

Home, Home 'Neath the Waves

Oh give me a home, where the buffalo roam,

and the deer and the antelope play,

and seldom is heard, a discouraging word,

and the skies are not cloudy all day

The classic American folk song Home on the Range has been conjuring the American prairies in our imaginations for generations. For many, the John Denver version is the seminal cover of the song. As he sings you can see feel the warm breeze rippling the tall grass and flowers. Giant bison wade peacefully through the vegetation while waterfowl float on clear ponds nearby.

The only pie more American than apple may be the ones these guys 

leave behind after eating all that grass.

Courtesy: Ard van der Leeuw via Flickr

"But wait a minute! This is a marine science blog! Why are we talking about grass-lands?" Well imaginary snarky reader, the ocean is teeming with its own prairies. Even though they haven't gotten the same kind of press as coral reefs or kelp forests they're absolutely essential habitats. And underwater prairies are every bit as idyllic and wild as their terrestrial compatriots.

Oh give me a home, where the manatees roam,

and the snails and the isopods play,

and often is heard, the cries of seabirds,

and the waters are calm in the bay.

"Stay away from Washington State. It's terrible. There's nothing beautiful

 or interesting to give you any reason to move here ever." -Washington State Motto

Courtesy: EcologyWA via Flickr

The dominant organism in any prairie, above or below water, is grass. Though we tend to lump every under water photosynthesizer together as "seaweed"; sea grass is remarkably unique. Other "seaweeds" are algae, which is a group of plant-like organisms that doesn't have roots, lacks veins for transporting nutrients, and makes spores instead of seeds. Sea grass is a true flowering plant, just like the grass on your lawn, except this is the only flowering plant able to survive under salt water!

Algae typically grows on hard surfaces because its holdfast needs something stable to cling to. Sea grasses need soft substrate, usually sand, where their roots dig in and actually stabilize the soil. They have what are called rhizomaceous (pronounced: ry-zo-may-shus) roots which means they spread out horizontally in a net and put out new shoots where there's enough light. Anyone who's pulled ivy by hand has experience with these kinds of roots. The rhizomes of sea grass cover so much ground and hold so much soil that they're a major protector of coastal shorelines from erosion. In the Caribbean, Western Atlantic, and Gulf of Mexico where they're called turtle (Thalassia testudinium) or manatee grass (Syringodium filiforme); sea grasses keep hurricanes from washing beaches used by sea turtles and tourists alike out to sea. Grasses on the American plains once did the same thing for the land by protecting the earth from the harsh prairie winds. Losing all that grass to agriculture caused the Dust Bowl of the 1930's.

 But tell me again how humans can't affect major changes 

on the environment.

Courtesy: US Department of Agriculture via Flickr

Only 200 years ago the tall and short grass prairies of the American West were rich with a diversity of animals that thrived on the variable habitat provided by the grasses. Insects of all kinds, burrowing rodents, birds and even terrestrial crayfish skittered and survived among the blades. Sadly most of these habitats have been lost to agriculture and suburbanization, but sea grass plains have avoided these disturbances and still host an incredible diversity of organisms.

Sea grass creates vertical habitat just like trees do in forests; so many species can grow on, in, and around the grass. One study in Denmark found more than 200,000 organisms of 86 types on a little more than 1,000 blades of grass. The folks doing the research even found entire tiny ecosystems on the blades. Diatoms, a kind of single-celled algae, grew in mats on the leaves. Isopods, a relative of crabs and shrimp, would walk along and graze on the algal mats. The tiny crustaceans were eaten in their turn by small anemones that also attached themselves to the grass.

We've recently discovered that these minuscule animals may actually benefit the sea grass as well. Sea grasses have male and female flowers just like terrestrial plants, and just like terrestrial grasses males release pollen that has to get into the female flower some way or another. On land, pollen is transported by the wind and by animals that travel between plant flowers. Until recently we assumed sea grass pollen was only transported by waves and currents. But we've found evidence that planktonic baby crabs, and nearly microscopic, bristly, worms are actually acting as pollinators for sea grass. These plankton visit male flowers where pollen grains get stuck on the appendages that normally help prevent the animal from sinking. Then they swim along to the next flower in search of food and inadvertently pollinate the female. I don't have the right permissions to post a picture of the pollen grains on the plankton, but you can see the incredibly cute pictures in the article at this link.

This species, called tape grass (Enhalus acoroides), is found in Asia.

The male flowers (white nubs) float way from their parent, and get 

caught in the female flower (yellow petals).  

Courtesy: Ria Tan at Wild Singapore via Flickr

The abundance of grass and wealth of small animals inevitably attracts larger animals to these rich feeding grounds. Like lions on the Serengeti or wolves in Yellowstone; seals, sharks, and other big predatory fish move through sea grasslands to consume the smaller predators drawn by the smorgasbord. Of course it wouldn't be a grassland without big grazers. North America and historically Europe have bison, Asia and Africa have rhinos and buffalo, Australia has kangaroos, and South America: llamas. The plains of the ocean: manatees, dugongs and sea turtles.  Sea grasses also bring in the massive assemblages of birds that are often seen on prairies. The coolest of these is probably the brant (Branta bernicla).

I'm a goose, he's a goose, she's a goose, cause we're all geese, hey!

Courtesy: JimGain via Flickr

In Europe, brant are called Brent Geese, presumably because the name Brent is used exclusively to identify obnoxious frat bros in the US. They're an incredible relative of the more familiar Canada goose (Branta canadensis), and they cannot survive without sea grass. The Pacfic's subspecies, the black brant (B.b. nigricans) summers on the north slope of Alaska and the islands to the north where their chicks can develop relatively free from predators. As the year wanes the brant are chased south by the frigid nights of winter. But brant aren't like the many marathon flyers that breed in the arctic. Brant have such a big body relative to how small their wings are that they can't make a trip from Alaska to to the southern hemisphere in one go like a bar-tailed godwit. Brant have to take pit stops the whole way from Prudhoe Bay to Baja to rest and refuel, and what do they look for en route? Sea grass.

The sheer abundance of eel grass (Zostera marina), as we call it on the west coast, makes it the perfect resource to gas up on. Eel grass is found all along the migration route, and because the blades are coated in organisms, the herbivorous goose probably gets much needed proteins and fats for energy. 

"Waiter, there's a bunch of bugs on my salad. <Chomp, chomp, chomp> 

Actually never mind, don't worry about it."

Courtesy: Jon. D. Anderson via Flickr

Brant are the ideal illustrator of how important and powerful something as commonplace as grass can be. A good sea grass prairie produces so much food that it can attract an entire population of animals. We believe that every single black brant stops at Izembek bay in Western Alaska, which has the largest eel grass bed in the world, on their way north and south each year. And just like their Canadian cousins that settle over the prairies of the US interior during the winter brant show us the soothing wildness of grasslands. It's just too bad John Denver didn't SCUBA dive.

Oh give me a home, where the manatees roam,

and snails and the isopods play,

and often is heard, the cries of seabirds,

and the waters are calm in the bay.

References:

Ganter, Barbara, "Sea Grass (Zostera spp.) as Food for Brant Geese (Branta bernicla): An Overview", Helgoland Marine Research, vol. 54, pg. 63-70, 2000.

Accessed via: https://tinyurl.com/zm95khs

DeAmicis, Stacey & Foggo, Andrew, "Long Term Field Study Reveals Subtle Effects of the Invasive Alga Sargassum muticum Upon the Epibiota of Zostera marina", PLoS ONE, September 14, 2015.

Accessed via: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0137861

Thormar et Al., "Eelgrass (Zostera marina) Food Web Structure in Different Environmental Settings", PLoS ONE, January 11, 2016. 

Accessed via: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0146479

Tussenbroek et Al. "Experimental Evidence of Pollination in Marine Flowers by Invertebrate Fauna", Nature, vol 7, 2016.
Accessed via: http://www.nature.com/articles/ncomms12980