Precious Argo

How's the old saying go? "If it looks like a duck, swims like a duck, and quacks like a duck, then it's probably a duck."

"Quack?"

Courtesy: Derek Bruff via Flickr

By extension I can imagine this test applies to any animal. Let's pick a random one and try it, shall we? If it looks like a..... Nautilus, swims like a nautilus, and has a shell like a nautilus it must be a nautilus. 

"Oh my God! What did you just call me!?"

Courtesy: Michael Vecchione via TOLWeb.org

Oh yeah I'm sorry, paper nauti..... I mean greater argonaut (Argonauta argo). I totally forgot about you. How about I make the rest of this post about how awesome you, and the other three species in your family, are to make up for it?

"We can live with that. I'll just sit here and make sure you

 don't mess up again"

Courtesy: NOAA Photo Library via Flickr

Okay where to start? Well, how about at the very beginning like my nanny used to say. Disclaimer: My nanny may have just been Julie Andrews movies. Anyway, we've known about argonauts for an incredibly long time. Their delicate, paper-thin, shells have been found painted on artifacts from 4000 years ago! Of course, back then we barely knew anything about these animals because we were mostly finding their old shells washed up on the beach. 

However many of the ancient Greeks were talented naturalists, and they started looking closer at these coiled beauties. Aristotle noticed that the argonauts could climb out of their shells because they aren't attached to them like a true nautilus or any other shelled mollusk. So how did Aristotle think argonauts got their shell? Well he assumed they stole it. For the longest time scientists thought that argonauts couldn't be making their own shells, so they were taking them from an unknown animal and using them as boats. Now this seems a little crazy, but add in the fact that female argonauts have sail-like webs on two of their arms, and you have the perfect animal to send after the golden fleece. 

Hahaha...What is it even...? Hahaha...There's a boat to compare it to..Hahahaha!

Bless you for this: Gerard Van der Leun, via Flickr

Although the theory that argonauts combined Grand Theft Auto and that pirate Assassin's Creed (Hold on I have to go pitch an idea to Microsoft) persisted well into the 1800's, eventually science started to sober up. We later discovered that female argonauts make the shells using glands in their webs that secret calcite. They spread these webs out over the shell and lay down material bit-by-bit like nature's 3D printer. 

 On the left you can see the webs with chromatophores, extended over the shell.

On the right this female has pulled the webs back, exposing her construction.

Courtesy: Michael Vecchione via TOLWeb.org

 If you're an astute reader, you've probably noticed that I've only mentioned female argonauts so far. This follows the history of these animals because for the longest time we had no idea what the males looked like. Why? You might ask, well they're tiny, like really tiny, only 1% the size of a female, and the biggest species' female only gets to 30cm across. Plus the males don't build shells, oh and sometimes they only have seven arms.

See argonauts are octopuses, and they normally have eight arms like any of their relatives. However one of a male octopuses arms is very different from the others. The third arm on his right side is called a hectocotylus (pronounced: heck-toe-cot-oh-luss) and it's used for reproduction. The males of most bottom-dwelling octopuses insert their hectocotylus into the female's gill opening; and sit there for a bit while a packet of sperm passes from inside his body, down the arm, and into the female's oviduct. Argonauts don't have the luxury of that kind of time though. They differ from their cousins by living up in the water column, instead of down on the sand. Living in the open ocean is great way of avoiding competition with your cousins down below, but it also means you have to travel far and quick to find food, mates, and shelter. 

Because the ocean is so big, and argonauts so small, males may not have many chances to find a female. To make sure they mate effectively the male argonaut's hectocotylus actually breaks off inside the female's body cavity, and he swims away. By embedding his sperm delivery system in the female, the male has insured that it's his DNA that fertilizes the eggs. Plus it's a great way to screw with naturalists. This is not a joke, the scientist who first found a hectocotylus buried in a female argonaut thought it was a parasitic worm!

 Plus what the hell do we call this thing, a septopus?

The eighth arm is kept inside that pouch.

Courtesy: Edwald Rubsamen via Wikimedia Commons and Public Domain

Now here's where the functional beauty of the female's shell can accompany its aesthetic beauty. Since she lives up in the water there's very little to attach her eggs to, and good material could be floating hundreds of miles from the female argonaut, so she lays her eggs right inside the shell. Female argonauts handcraft baby strollers to push their kids around in until they hatch. Not only that, but the shape of the shell allows the female to trap air in its top which helps counter-act the weight of her body and the eggs; and keeps her from rising or sinking too fast. 

You can see the eggs hanging out of the lower part of this female's shell.

She's new to this whole arts and crafts thing.

Courtesy: Bernd Hoffman via Wikimedia Commons

So how'd I do argonaut? Did we cover everything that makes you so cool? Be fair, we don't know much about you since you're all so small and you live in oceans around the entire world.

Whoooo! Nice work! Go team Argo! High eights all around!

Courtesy A.E Verrill via Wikimedia Commons and Public Domain

References:

Finn, Julian K., "Taxonomy and Biology of the Argonauts (Cephalopoda: Argonautidae) with Particular Reference to Australian Material", Molluscan Research, 2013, Vol. 33, No. 3, 143-222.

Heeger, T., Piatowski U., & Moller, H., "Predation on Jellyfish by the Cephalopod Argonauta argo", Marine ecology Progress Series, Vol. 88, 293-296, 1992.

Orenstein, Marcie, "Marine Invertebrates of Bermuda: Paper Nautilus (Argonauta argo)", The Cephalopod Page, 

Accessed via: http://www.thecephalopodpage.org/MarineInvertebrateZoology/Argonautaargo.html 

Mangold, K., Vecchione, M., & Young, R., "Argonautidae", Tree of Life Project, 

Accessed via: http://tolweb.org/Argonauta

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.

Mommy, Where do Baby Sharks Come from?

Let's start this week off with a little quiz, shall we? What's in the picture below?

"Sand." Alright smart-ass, what else? "Shells."

Courtesy: Patrick Feller via Flickr

If you said mermaid's purse, or shark/skate egg then you're right. All of those animals are part of the chondrichthyes (pronounced: con-drick-thees) class of fish.These fish have skeletons made of cartilage rather than bone. We talked a lot about chondrichthyes diversity in the very first blog post if you'd like to get a refresher. The name mermaid's purse applies to the egg cases of all cartilaginous fish because they're leathery, and most are rounded squares like a purse. The leathery-ness is important too because it's tough but flexible. This means the case is tough enough to protect the embryo, but is flexible enough not to shatter. Instead of nesting; skates and egg-laying sharks just kind of drop their kids off somewhere sheltered on the bottom and get on with their lives. That might sound mean, but mom's body produces a yolk that's so rich and full of nutrients that the babies come out of the case fully formed and ready to survive. (Editor's Note: Depth and Taxa does not condone abandoning one's children with 18 year's worth of food and calling it good.) Laying eggs is a method of reproduction called oviparity, and it's only one of several different ways of developing your babies, all of which cartilaginous fish are capable of.

Oviparity is pretty familiar stuff, but let's go over it anyway because it's the root of the other types of reproduction in sharks and their relatives. Unlike many of their bony relatives, chondrichthyans all fertilize their eggs internally. You can actually distinguish males and females of these fish because males have what are called claspers on their pelvic fins (the fins closest to where hips would be.) Claspers are used to hold onto females during mating and deliver sperm into her vent. (the multi-purpose opening of many marine animals.)

The claspers are the little finger-like nubs on the inside of the fins.

Courtesy: eustatic via Flickr

Once the eggs are fertilized they develop the familiar embryo and yolk combination you might have seen shining a flashlight through a chicken egg. Then, like we talked about before, mom drops the eggs off and they develop until they hatch. While inside the mermaid's purse the embryo has only the yolk for nutrients, so when it runs out the baby starts to get hungry and that helps prompt hatching.

Plus the WiFi in the ocean is terrible, so there's no Netflix to

 keep you perfectly still for weeks at a time.

Courtesy: Marian Gonzales via Flickr

 Of the four types of chondrichthyes; sharks are less likely to lay eggs than some of their relatives. All skates lay eggs, as do all of the chimeras. None of the rays lay eggs, and only about a third of what we commonly call sharks don't give live birth.

The next type of fetal development is a weird combination of eggs and live birth. For a long time this was referred to as ovoviviparity (pronounced: oh-vo-viv-i-pair-itty), but this term is falling out of favor because it implies the fetuses aren't getting any nutrients from mom. Recent research suggests that many, but not all, sharks and rays with this means of development contribute at least some nutrients to their babies. This can be through secretions from the uterus that the unattached babies absorb through their skin or consume, or in the form of unfertilized eggs which the developing young eat after their yolks run out. In at least one species the first fetus to use up its yolk will actually eat its brothers and sisters before being born!

"Don't mess with me man, I have seen some s**t "

Courtesy: Justin Morgan via Flickr

 What's consistent across these means of development is that the embryos are never physically attached to their mom. Most of the sharks that give live birth exhibit these strategies for developing their young. All of that is pretty weird and cool, but buckle up, 'cause we're about to take everything we just talked about and add another layer of bizarre.

The last means of fetal development is called placental viviparity. You read that right, placenta like in mammals. Placental development in sharks is a perfect example of one of my favorite concepts in biology: convergent evolution. Convergent evolution is when two very distantly related organisms develop similar traits or strategies completely independent of one another's genes. So even though some sharks have a similar fetal development strategy to mammals it doesn't mean we're related or that we got that trait from sharks.

Amazingly, in placental sharks, the embryos still start out with a yolk. Like other fish the baby shark starts off using up the yolk's nutrients, but late in this process mom's body supplies some of those nutritious secretions we talked about earlier. While her body does this, the lining of the yolk sac actually stretches out and fills with blood vessels. It reaches from the belly of the developing shark to the mom's uterine lining where it attaches and acts as the link between the two for gas exchange (getting oxygen in and CO2 out) and metabolism (getting nutrients in and waste out). This incredible strategy has developed in only a few species of sharks.

"Hey mammals, who's 'highly evolved' now huh!?"
Courtesy: Serena Epstein via Flickr

All of these strategies are spectacular means for getting chondrichthyan babies out into the world ready to survive from the second they emerge. By fully developing inside an egg or their mother; sharks, skates, rays, and chimeras have set themselves up as some of the most successful animals on the planet.

References:

Hamlett, William C., "Evolution and Morphogensis of the Placenta in Sharks", Journal of Experimental Zoology, 1989, vol. 252(S2), pp. 35-52

Musick, J.A. and J.K. Ellis, "Reproductive Evolution of Chondrichtyes", pp. 45-79, In: "Reproductive Biology and Phylogeny of Chondricthyes: Sharks, Batoids and Chimeras", William C. Hamlett, ed., Science Publishers Inc., Plymouth U, 2005

Accessed via: http://www.vims.edu/people/musick_ja/pubs/Repro_Evol_of_Chondrichthyans.pdf

Wourms et al., "The Maternal-Embryonic Relationship in Viviparous Fishes", pp. 5-10, In: "Fish Physiology: Volume XI: The Physiology of Developing Fish Part B: Viviparity and Posthatching Juveniles", W.S. Hoar and D.J. Randall, Academic Press Inc., 1988 

Getting Ston(ey)ed with Coral

We're Back! The new Depth and Taxa headquarters (AKA my apartment) is all set up with a fancy desk and everything. Thanks everyone for your patience during my moving process. So without further ado let's get back in the swing of things.

There was some great news that came out of the US National Oceanographic and Atmospheric Administration (NOAA) last month. Twenty coral species have been listed under the Endangered Species Act. "What? That's horrible, more corals are at risk of extinction!" you might be saying, but listing as endangered actually benefits many animals that are at the brink. When organisms are imperiled by extinction listing them serves to provide legal protections for, not only them, but also their ecosystems. It's kind of like a silent alarm going off. When someone breaks in, property is at risk, but once the alarm goes off; the police can come and take steps to keep you from being burgled. It's about time we got serious about protecting coral too. Whole reefs are in danger of disappearing. One study suggests that coral cover in the region between Asia, Australia and Hawaii has decreased by 20% since just the early eighties.

So why do we care? Coral is certainly very pretty, but it's also a fascinating and essential organism.

Seen here being all three at once.

Courtesy Ian Robertson via Flickr

Coral is a massive and incredibly old group of animals. In fact just about anything you think of as ancient, corals were there for its beginning: Megalodon? Coral bemoans its short time on the planet. Dinosaurs? Yeah coral thought they were cool for a while. Coelocanths? They're just trying to steal coral's old-timey charm. What I'm getting at is that coral shows up very early in the fossil record, something like 480 million years ago!

So what's the secret to coral's success? Well diversity is a big part of it. There are something like 2,500 coral species on earth today. They can be hard, soft, individual, colonial, small, large, tropical, temperate, shallow, and deep.  The corals we're most familiar with, and all of those recently added to the endangered species list, are the shallow-living stony corals we like to brag about snorkeling among when we take a trip to the tropics.

All corals are a part of the cnidarian phylum which you may remember from the earlier post about jellyfish.You might also remember that the scyphozoa, hydrozoa, and cubozoa have two life stages: the free-living medusa and the stuck-on polyp. Corals are part of the anthozoa which are all the animals that have no medusa stage.

Perseus can get behind an animal that removes the medusa. (I will not apologize for this terrible joke)
Courtesy Wally Gobetz via Flickr

What stands stony corals out from other members of their phylum is their structure. Unlike sea anemones or jellies; stony corals actually secrete a skeleton. Coral that you might find at a jeweler's, or on the beach, is in fact the skeletal remains of a stony coral. So your beach house may have skeletons in its closet as well as on its coffee table. These skeletons, made of the same molecules as eggshells, are what allow for the gigantic reefs seen in tropical waters throughout the world. And amazingly every reef starts out as a single teeny-tiny coral polyp.

See when a coral mommy-daddy and daddy-mommy (many stony corals are hermaphroditic) love each other very much, and the season and tidal phase are right, they pour floating packets of sperm and eggs out of their bodies and into the water. It's all very romantic as thousands of other animals circle the waters around them devouring their genetic material before it even has a chance to mix. But luckily there are so many of these gamete (reproductive cells) balloons that some do make a new baby coral. At this point in their life baby corals are called a planula, they're microscopic, and they're covered in little cellular oars that allow them to move and find a place to settle. As they settle, baby coral metamorphoses into its adult form, but its still incredibly tiny and all alone. So our intrepid hero begins making itself some friends, by cloning.

"I'm pleased...we're pleased...it's nice to meet you"
Courtesy Nhobgood via Wikimedia Commons

Each of those little anemone looking things up there is a clone of a single polyp that settled on a hard surface. If the entire colony is very large, then the original polyp probably settled decades ago. Some head's of coral have been estimated to be over a thousand years old! This slow growth rate is one of the reasons many coral reefs are at risk of extinction.

 Amazingly, although the clones are separate individuals from the other polyps they all share body tissues with one another. As the polyps catch prey with their stinging tentacles and eat it; the nutrients from that food are actually spread across the shared tissue so that the whole colony benefits. These shared tissues are also what secrete the hard skeleton of stony corals. And it's inside the corals' shared tissues that we can find the reason for their stony skeleton.

Just beneath the skin of stony corals lives one of a number of different algae. These single-celled seaweeds, called zooxanthellae, (pronounced zo-zan-thell-ee) are taken in by the coral deliberately because they can benefit one another greatly. The algae is protected from the thousands of mouths out in the plankton and the corals' wastes make great fertilizer. The coral also benefits because the algae's photosynthesis provides oxygen and nutrients both of which the coral can use. So the coral creates this elaborate skeleton in part to reach for the sun. The skeleton acts like the trunk and branches of a tree pushing the coral and its algae buddies towards the light. The constant competition for sun is what has driven the evolution of so many amazing forms and shapes of different corals.

Enough sun salutes to make a yogi weep for joy
Courtesy US Fish and Wildlife via Flickr

 This mutual symbiosis has been going on for so long and is so beneficial that some coral species can't feed themselves without their zooxanthellae. When people talk about coral bleaching this is what they mean. Something has gone wrong in the ecosystem, so the algae have either gone elsewhere or died. Leaving only skeletons behind. Luckily you can easily help prevent bleaching if you visit tropical areas. Danovaro et. al discovered that synthetic sunscreens actually encourage the growth of viruses that infect and kill zooxanthellae. So when you take that snorkeling trip make sure to use non-synthetics like titanium dioxide or zinc oxide. Often times these sunscreens are labeled as "coral safe" or "sensitive skin" so they're easily found.

References:

http://www.fws.gov/endangered/laws-policies/

http://www.noaanews.noaa.gov/stories2014/20140827_corallisting.html

http://www.ucmp.berkeley.edu/cnidaria/anthozoafr.html

https://marine.rutgers.edu/pubs/private/Mass%20et%20al_Immunolocalization_PNAS2014.full.pdf

Danovaro et. al, "Sunscreens Cause Coral Bleaching by Promoting Viral Infections", Environmental Heatlth Perspectives Apr. 2008: 116(14): 441-447. Accessed via http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2291018/

Hoover, John P. "Hawai'i's Sea Creatures: A Guide to Hawai'i's Marine Invertebrates", pg 46-49, Mutual Publishing, 1999