If you have even had the chance to see or feel a tunicate, you’ll know they’re weird little creatures. At first glance, the tunicate resembles a sponge, with an exhalent and inhalent opening. They’re often found in similar environments, encrusting rocks, ships, and docks. Like sponges, many species of tunicates are also colonial, colourful, and generally unassuming, which is why you may not have noticed, or even heard of, tunicates.
Colonial tunicate (Botrylloides violaceus)
Red encrusting sponge – credit: Nick Hobgood
Despite their initially similar appearance, sponges and tunicates couldn’t be more different. For starters, if you give them a gentle touch, you can immediately feel a difference. Sponges will often be soft, porous, and somewhat flexible, whereas most tunicates feel solid, firm, and gel-like (kind of like a gel-cushion you’d buy for your shoes). If you have ever accidentally stepped on a tunicate, you might have received a shot of water back, hence why they are often called “sea-squirts”. Stick them under a microscope, or even look at them with a magnifying glass, and you should start to notice that tunicates are much more complex animals than sponges. This is because while sponges are the simplest of all animals, not even having cells organized into tissue, tunicates belong to the phylum which has the most complex animals of all: the Chordata.
Solitary tunicate – credit: Nick Hobgood
Yellow tube sponge – credit: Nick Hobgood
For those of you that are familiar with the word “chordate”, you might be surprised. That’s because the phylum Chordata is our own phylum, including all vertebrate animals. That’s right: tunicates are your closest invertebrate relatives! Chordates include all animals which have a notochord at some point in their development. Notochords are stiffened (but flexible) rods that run along the dorsal (back) side of the animal, and provide structural support for muscles and bone. Most vertebrates only have a notochord early in their embryonic life-stages (although some adult fish still have them), and adult tunicates also lose their notochords.
Larval tunicates (called “tadpoles”) have a well-developed notochord, which allows them to be very strong swimmers. They use their notochord as a “push-pull” point for their little muscles. Tunicate tadpoles are attracted to light, non-feeding, and have a very short larval stage (it takes a lot of energy to swim so much!). Being a strong swimmer is therefore very important for finding a suitable environment in which to settle. After as little as a few hours, the tadpoles will start to swim down and try and find a place to settle. They settle “tail-up”, and the tail/notochord begins to resorb as they undergo metamorphosis.
Tunicate tadpoles (Botrylloides violaceus) – Credit: Riley C. Nolan
Diagram of a tunicate tadpole – Credit: Jon Houseman
Adult tunicates look very different than their tadpoles. The organs are near the base, and the majority of the body consists of a large feeding organ called the pharyx or “gill-basket”. Food particles are trapped as water is drawn in through the inhalent opening (atrial siphon in the diagram below), and through slits in the gill-basket. The entire body is covered in a sheath called the tunic, which is filled with an acellular jelly-like substance called tunicin (I love it when terminology makes sense).
Diagram of an adult tunicate – Credit: Jon Houseman
Colonial tunicates – Credit: Nick Hobgood
The fossil record for tunicates is very, very poor, and specimens from the Cambrian and Carboniferous that were once considered tunicates have since been found to be organisms from other phyla (Chen et al. 2003). However, there are several well-preserved fossils of a critter called Shankouclavafrom the Early Cambrian of southern China that are still considered tunicates(Chen et al. 2003). Considering tunicates are the “base” of our own phylum, this find is a pretty big deal, and shows that the group has had little change over more than 500 million years! (check out their paper for some neat images!)
I’ve been rather quiet on my blog this past year, in part due to an intense workload down in California, studying for my candidacy exam (I passed, phew), the usual suite of conferences and writing, and of course, life. But I’ve also been doing a lot of thinking and reflection on how to be a better science communicator. This year was an immense year of growth for me both as a scientist, and as a human being. The folks of Bodega Marine Lab were amazing, and I learned so much during my time down there about marine science, the importance of collaboration and peers, and how to advocate for science. I am probably going to do a blog or two about my time in California, but I figured I’d start with something familiar.
Anyone who has ever been tide-pooling along the rocky intertidal of the Pacific coast of Canada or the US has probably come across a little blackish-purple snail, often with an eroded apex that can look either pearly or orange, called the black turban snail. Its scientific name is Tegula funebralis (although this is hotly debated, and it should probably be called Chlorostoma funebrale, but I’m not going to get into that). During a low tide, you can find them by the hundreds, clustered around the bottoms of rocks, or in tide pools, munching on their favourite algae.
Marine intertidal ecologists are very familiar with this little snail, and most of us are unusually fond of it. Why? It’s hard to explain, but somehow this non-descript little snail, with its little black foot (body) and curious epipodial tentacles that will explore you as it wobbles across the palm of your hand, is very charismatic. It is unusually long lived for such a small snail (up to 30 years), has been used for countless studies, and is commonly found in teaching labs and touch tanks at aquariums (not as scary as in Finding Dory). Some scientists refer to it as the “most noble snail”, and there has even been an article that lightly suggests that Tegulacan explain the logic of the universe. I tend to agree.
Tegula is a large genus, consisting of some30-odd extant (living) taxa found all around the Pacific, including other species such as the brown turban snail, Tegula brunnea, which looks similar to T. funebralis, or a pretty, light coloured one called the dusky turban snail, Tegula pulligo. You can distinguish T. funebralis primarily by its purplish-black colour, eroded apex that will expose the pearly nacre of the shell, and crenulated ornament along the top margin of the whorl (spiral), although this is not always present. T. brunnea is similar in colour, and is also found in the intertidal (lower), but will be more brown than purple, does not have the eroded apex, and for living snails, will have a bright orange band on its foot that is not present in T. funebralis.
The fossil record of the Tegula genus extends back as far as the Cretaceous, to a creature called Tegula jeanae (Squires and Saul, 2005), which interestingly looks a lot like Tegula funebralis. As many Tegula are found either in the intertidal, or in the shallow subtidal, their fossil record isn’t the best, as these environments usually erode, rather than become buried. However, there is some nice material, particularly of T. funebralis, from the Plio-Pliestocene of southern California. Interestingly, I discovered from curators at the Natural History Museum of LA County Invertebrate Paleontology Collection that while most fossils lose their colour, even from the Late Pliestocene (~12,000 – 126,000 years ago), T. funebralis retains its dark purple colour, making it very easy to spot among the drawers of dusty, beige fossil shells. In addition to fossil material, there is also a lot of archaeological material from shell middens, as Tegula has been used for food by people all along the coast (Erlandson et al. 2015).
Not only is Tegula a cute little snail and excellent experimental animal, it is also important ecologically. Being one of the most common and abundant intertidal snails, it is food for lots of animals, such as sea stars, crabs, octopus, and even birds. One of the reasons we study it so much in the Leighton Lab is because populations of T. funebralis often have lots of repair scars from crab attacks, meaning we can study how this crab-snail interaction is affected by things like wave-energy, environment, other potential prey, and even ocean acidification (which is what I am exploring for my dissertation). Unfortunately, OA studies have found that T. funebralis is in trouble (e.g. Jellison et al. 2016). From theresults of my experiments, it is in huge trouble (Barclay et al. 2017 – stay tuned for updates!). And if something happens to Tegula, it could be detrimental for intertidal ecosystems. Think of it this way: without Tegula, there would be a lot less food for predators, which puts more pressure on other prey animals and could disrupt populations their populations, potentially messing up the “food chain” or established interactions within the whole ecosystem.
So the next time you happen to visit the Pacific coast, keep your eyes out for the black turban snail. Once you spot one, you’ll notice them all over the place. Lightly twist one off a rock and place it in your palm. If you are gentle and patient, it will venture out of its shell and explore your hand. Remember that they are in trouble due to climate change, and will need our help to make decisions that will work towards protecting them and their environment. And if you see a piece of kelp washed up, try feeding it to them. It’s their favourite snack, and it’s fun to watch their little raspy radula (tongues) hard at work. We could all benefit from taking to time to just sit, soak in their rocky intertidal home, and explore life at a “snail’s pace”.
Erlandson, J. M., Ainis, A. F., Braje, T. J., Jew, N. P., McVey, M., Rick, T. C., Vellanoweth, R. L., and Watts, J. 2015. 12,000 Years of Human Predation on Black Turban Snails (Chlorostoma funebralis) on Alta California’s Northern Channel Islands. California Archaeology 7:59-91.
Jellison, B. M., Ninokawa, A. T., Hill, T. M., Sanford, E., and Gaylord, B. 2016. Ocean acidification alters the response of intertidal snails to a key sea star predator. Proceedings of the Royal Society B 283:20160890
Squires, R. L., and Saul, L. R. 2005. New Late Cretaceous (Santonian and Campanian) gastropods from California and Baja California, Mexico. The Nautilus 119:133-148
It’s been a while since my last blog post, and I’m about to deviate even further from my normal routine by sharing a rather personal post. OK, a very personal post. But as someone who values science advocacy and outreach, I feel this post is nonetheless important to share with both the general public, and young aspiring scientists.
I think one of the triggers that has caused me to write this post has been this hashtag going around Twitter, #reallifescientist (and other derivations, such as #overlyhonestmethods, #reallivescientist, #realcdnsci, etc.). The general sentiment is that if we as scientists show ourselves doing normal, everyday science, perhaps we will seem less like cold, calculating figures in white lab coats, and more like real people just doing real jobs. Scientists are usually perceived as “apart” from the average person, and have generally done a lousy job at communicating what it is we do, or, more importantly, why we do it. The hashtag #reallifescientist is an attempt to reclaim the title of “scientist” in a way that humanizes us. We’ve realized that we have screwed up colossally. In a world of “alternative facts” and outright, dangerous denial of human induced climate change, it is the scientists who are admitting we were wrong.
Let me be clear: we are not wrong about climate change (and a debate on the topic is beyond the scope of this post). Rather, we as scientists, who are used to failure and trying new approaches, have pin-pointed our lack of communication skills as a major problem. We’ve started to realize that we have isolated ourselves so much that the general public doesn’t understand us or the work we do. We have realized our mistakes and have been pushing for better science communication. We are trying to get out of our ivory towers and have conversations with the average person about how science can benefit them. We’re listening to the concerns of the oil workers whose livelihoods are affected by our push against fossil fuels. We’re honing our elevator pitches, crowd sourcing our questions with citizen science, making YouTube videos, marching on Washington, and taking to Twitter with hashtags like #reallifescientist.
Scientists, like myself, are trained to be logical, critical, and “publish, or perish”. In asking for advice as to whether writing this post was a good idea, a friend and fellow scientist told me that our unwillingness to speak out about personal issues makes us seem “superhuman” to one another. So what does that make the non-scientist think?
I’m about to share some very personal information. I’m taking a professional “risk” in telling such a personal story, but I feel it is important to share. With hashtags like #reallifescientist emerging on Twitter, and the debate about whether or not science should become involved in politics, I see an underlying need for us to speak out as people, not just scientists. I also want young, aspiring scientists who may be struggling to keep up with midterms, relationships, mental health, and an uncertain future that yes, science is hard, but don’t you dare give up. So here is my story:
I’m a #reallifescientistwho works on both fossil and modern ocean ecosystems. I am part of a growing field called conservation palaeobiology, which seeks to use the fossil record as a way of understanding modern ecological crises. My PhD looks at the ecological implications of ocean acidification (caused by increased absorption of carbon dioxide into the oceans) through time. Given the drastic increase in atmospheric carbon dioxide due to humans and greenhouse gases, ocean acidification is an absolutely exploding topic of research. And yes, I’m riding the wave because I’m a #reallifescientist who will also be looking for a job in the near future.
I’m a #reallifescientist in the midst of a massive, 8 – 9 month long project at Bodega Marine Laboratory in California (I know, lucky me, I’ve missed the Canadian winter – just kidding, I really miss it). I’m investigating how ocean acidification, as well as the fear of predation, affects shell growth in two different species of snails. The idea is that if snails can’t grow their shells as well in acidic oceans, they may be more susceptible to predation by shell-crushing crabs. If the crabs are able to just wipe out all of the snails, then the crabs have nothing to eat and crab fisheries may be devastated. Or there may be an explosion of the foods that the snails used to eat, which could displace other organisms. Generally, if you mess with the snails, the whole food web may unravel.
The project is incredibly time consuming, consisting of daily water changes which take about 3 hours, photography and measurements of 320 snails, thousands of water and chemical samples and analyses, field work to get food for the snails, plus data entry and analysis. I work at the lab all day, then come home and do data entry all night. I’m lucky if I go to bed by 1, then I get up early to bike 8 kilometres to the lab, rain or shine. I knew what I was getting into, but it’s difficult all the same. I also know that many grad students struggle with similar work loads.
I’m a #reallifescientist, but this is the most I’ve written since arriving to California. I’ve only read about 5 papers too. I’m trying not to feel too bad about that because my biggest goal when I started my PhD was to recognize and fight impostor syndrome (the general feeling that you are not good or smart enough, and sooner or later, you’ll be outed as an “impostor”). As I said, I basically live and breathe this project, so everything else will just have to wait. I have learned a lot about modern ecology, and met so many amazing minds, which was the goal in coming to BML.
I’m a #reallifescientist, but I am bad at statistics. Again, I recognize impostor syndrome, but I also recognize that there are skills which I need to improve upon. It’s important that everyone understands that scientists can’t be good at everything, and there are lots of different kinds of “smarts”. I’m really good at intuitively understanding organisms and recognizing patterns in nature, and I really like looking at how organisms interact. But put a formula in front of me, or ask me which test I should use to confirm the pattern I think I’m seeing, and my mind is usually blank. I’m usually right about the pattern, but just not good at knowing how to put a number to it.
I’m a #reallifescientist and a Vanier Scholar, which basically means that the Canadian government gave me a lot of money to do science. This is not meant to be a brag, but more to show that:
Despite being rather horrible at statistics, I am still a good scientist. I have several lead authored papers in good journals, and I know I crushed my master’s degree.
Invertebrate palaeontology and conservation palaeobiology are important and valid fields of study. Vanier scholarships are the biggest awards Canadian grad students can get. Snails and brachiopods may not be as flashy as the dinosaurs I thought I was going to study when I applied for university as a teen, but I find the real world impacts of palaeoecology much more satisfying.
Yes, Canadian taxpayers, you are paying me to change snail water, but don’t worry, I am working hard for the money, and should have at least a couple of papers to show for it.
I’m a #reallifescientist, but I’m also tired. I started my PhD in September of 2015. I felt confident. I’d survived my Master’s well, and was a contender for several major scholarships. I had a really cool project lined up, and felt a PhD would give me lots of time to learn all of the statistics I needed to know. And then my world began to fall apart.
I’m a #reallifescientist, but I’m also a niece. My aunt was sick with terminal cancer of the throat when I started my PhD, and even after suffering a stroke, it took her three weeks to die. It was agony to watch her, my mom, my aunts, and the rest of the family go through the pain of such a slow death. I got into a routine of calling my mom, the youngest in a family of six kids, every day after school to see if my aunt was still alive, hoping, every time, that she was gone. That it would be over. It was the first time my mom had lost a sibling, and it was horrible to watch her go through that pain, knowing that as the youngest in the family, it is likely going to happen again and again.
I’m a #reallifescientist, but I’m also a spouse. I started my PhD two weeks after getting married (I was writing my Vanier scholarship application two days before the wedding), but had to move out of my house and to a different city to do so. My husband has been so amazingly supportive, but I constantly struggle with the guilt of my decision to put our life on hold to pursue my career. I know I’m doing what I need to, but it is hard because I know I’m hurting him by making him lonely. It’s hard because I miss him too.
I’m a #reallifescientist, but I’m also a grandchild. My grandmother, and last remaining grandparent, died very unexpectedly this fall. I have been struggling with her death much more than I expected. I think it’s because we were so close. She and I were such kindred spirits, and while I lived far away, I called her regularly. We talked about anything and everything, for hours at a time. I feel like she understood me better than anyone, even my husband. She was up to date on all of my science pursuits, and had even attempted to read my latest publications. She was a writer too. In fact, they found her at the kitchen table, pen in hand, having just completed her first novel. We just had this connection. But she had been busy. I had been busy. And I forgot to call her. And then it was too late.
I’m a #reallifescientist, but I’m also a friend. My best friend from high school lost her dad when she was 10. Now, she’s pregnant with a second child that her mom might not get to see. Her mom is gravely ill with cancer, so much so that my friend and her long time fiancé decided to get married this past weekend, just to make sure that her mom was there for the wedding. I’m sad for my friend, and sad that I can’t be there for her. I’ve watched two other close friends lose parents to cancer, and never figured out how to help. I mean, how can you?
I’m a #reallifescientist, but I’m also a sister. When I started my PhD, I moved in with her. Shortly after my aunt died, my sister found out that she had a brain tumor. This has been a horrible, recurring nightmare in my life because my husband, then boyfriend, almost died of a brain tumor when we were 20. My husband, it turns out, was the lucky one. He had surgery, and has been perfectly fine ever since. My sister has not been so lucky. She had her first surgery in January of 2016, and while the surgery itself went fine, the surgeons were not able to get all of the tumor. My sister went on various drugs to see if they could control the tumor, but nothing worked. So on Halloween, she went in for a second surgery. I had booked plane tickets to come down to California, and had to reschedule them because the surgery was so last minute. We expected the surgery to go as well as the first one, and it did, but because it was a repeat surgery, they had to put a lumbar stint in her back for a few days. I left for California the day before she was released from the hospital, feeling satisfied that she was on the mend.
I plunged right into my work when I arrived to California, and then joined most of the lab in attending a professional conference in Monterey at the end of the week. Then I got a call that my sister was back in the hospital having contracted a resilient form of bacterial meningitis from the lumbar stint. She was to be in isolation for three weeks, but we merely viewed this as an inconvenience for her.
On one night of the conference, we went to the Monterey Bay Aquarium, and I spent the evening ogling all of the beautiful ocean displays. Meanwhile, my sister had lost the ability to walk over the course of a few hours, and her throat had inexplicably closed up. They called a code blue on her, and had to force a breathing tube down her throat and drill a hole in her head to relieve pressure on her brain from the meningitis. I found out the next morning in the middle of the conference, and sort of forgot where I was.
I’m a #reallifescientist, but I broke down in the middle of a professional conference. A professor I had never met before came up to me, gave me a big hug, and held my hands as I tried to breathe. I don’t even know her name. I wanted to come home, but my parents told me that my sister was going to be fine. That I should just wait because it looked like she was recovering. But by the Monday after we had returned from the conference, my mom told me to come home. My sister’s cerebellum had been pushed down into her spinal column, preventing circulation of the cerebrospinal fluid, and causing paralysis. They had to do an emergency surgery to remove part of the back of her skull and a small piece of the lowest brain to make room for her cerebellum. I booked the next available flight, but it wasn’t until Tuesday evening. That Monday night, laying in bed in a different country with no way to get home, was the worst night of my life. And I had already experienced my boyfriend going through emergency brain surgery.
I’m a #reallifescientist, but I abandoned my project because who cares about science, or funding, or US Visas, when your sister might be dying? I got home the night after her surgery, and my husband, who had driven up to take care of my parents, picked me up from the airport and took me to the hospital in the middle of the night to see my sister. She had so many tubes, screens, and sensors hooked up to her.
She spent the next two and a half weeks in ICU. It was really touch and go for the first two weeks, and we really didn’t know if she was going to be OK, let alone ever be able to walk again. But after almost two weeks, she was finally able to breathe on her own. Regaining mobility took a little longer.
I stayed for just over three weeks before I returned to California, and when I left, she had just taken her first few steps with a walking machine. She was in the hospital for two months, but is thankfully now on the mend. She is still working on her balance and regaining strength in her muscles, but hopefully my mom will be able to go home in a few weeks, and my sister will be able to live on her own again. After everything she’s been through, part of the tumor is still there, but they will not operate on her again. She’s been started on some drugs to control the tumor, so wish us luck that the drugs work this time.
I’m a #reallifescientist, but coming back to California, just for a project, has been the hardest thing I’ve ever had to do. It’s both the reason I am “stuck” here, and the thing keeping me sane (or busy). I expected some homesickness with this trip, but I miss my sister terribly. I’ve met so many amazing, kind people here, and if it weren’t for them, I’m sure I would be very unwell right now. But, I panic every time I don’t hear from my family in a few days. I know it is unnecessary, but having been through this once before with my husband, I know it takes a while for the paranoia and fear to go away. Not to mention the guilt of not being there for my sister, let alone my husband, and my friend.
Thankfully, I might be starting to see some results with my experiments.
After all, I’m a #reallifescientist, and none of my personal problems are stopping me from doing a damn good job. Sure, I chose sleep over collecting shell measurements in February, but the loss of a few data points is not going to kill my project. My mind may be focused on my sister rather than writing my methods section, but at least I’m writing something. My goal is to submit the results of this project to a journal by the end of the year. Even if I don’t make that deadline, I know I will get it done, and will do it well. I also have to complete my candidacy exam soon after I return to Canada. But I plan to take a long holiday first.
Science takes time, and sometimes our personal lives make it hard to stay motivated. We may be burdened with family tragedies, relationship issues, personal obligations, or poor mental and physical health. But even if we struggle, or fall behind on the endless proposals, deadlines, and mountains of data, we will continue to work, and do it well. So be kind to yourself.
The modern ocean is full of scary, disgusting, bizarre, awesome, and adorable organisms (multiply that by several thousand times, and you can cover prehistoric oceans too). While crinoids might not strike terror into your heart, they are pretty strange animals, which are often mistaken for plants at first glance (the name crinoid means “sea lily”). I personally find them somewhat adorable (living, swimming feather dusters? I mean, come on).
Crinoids are a class of echinoderms, the group which includes creatures like sea stars, urchins, sand dollars, and sea cucumbers. Echinoderms are characterized by having some form of five-sided symmetry, and a system of thousands of tiny appendages called tube feet, which allow the organisms to move and feed. Many echinoderms have five or more arms which are lined with tube feet, often improving their ability to catch food. Another characteristic of echinoderms is that they have a skeleton formed in the middle layer of the skin, just like vertebrates, which actually makes echinoderms our closest invertebrate relatives. Most other invertebrates have a skeleton which forms in the outer layer of skin, like the exoskeleton of an insect.
Crinoids are composed of three or four main sections: the holdfast, stalk (sometimes), calyx, and arms. At the base of the animal is a kind of root system, which is used for attachment onto a surface or substrate. This is called the holdfast (get it? It holds the crinoid fast/tight to something. I love it when terminology makes sense). Some crinoids then have a stalk, which leads to the head, including the mouth and anus, which is called a calyx.
Why the feather duster analogy for crinoids? Coming from the calyx, crinoids have a lot of very thin, long arms, with secondary arms (called pinnules) that look like the main barb and secondary filaments on a feather. The pinnules on a crinoid’s arm are covered in long tube feet, which act like a net to catch food particles out of the water. The tube feet then move food down the arm to the mouth, which is located on the calyx. The overall effect is that crinoid arms look like a bunch of feathers. Hence: feather duster of the sea.
As I mentioned, modern crinoids can, indeed, swim, flicking their arms to paddle through the water. They do get tired fairly easily, so swimming isn’t usually sustained for more than a minute or so. Some crinoids can also walk or drag themselves along the ocean floor. This is especially advantageous if they get knocked over, covered in sediment, or perhaps need to flee a predator. Check out this YouTube video of a swimming crinoid in action:
While most modern crinoids just have the holdfast, calyx, and arms, the majority of fossil crinoids also had a stalk. The stalk gives them the appearance more of a pinwheel than a feather duster. The stalk is comprised of a series of disks (called columnals) which are stacked on top of one another, and elevate the calyx high above the ocean floor, much like the trunk of a tree. Imagine a series of poker chips (the cheap plastic ones with the ridges along the edge) stacked on top of one another, with a hole in the middle and a string (liagment) passing through and holding them together. That is basically the stalk of a fossil crinoid. However, not that long ago, modern, stalked deep sea crinoids were discovered, leading to the group being termed “living fossils”.
Given the nature of a crinoid’s skeleton, which is composed of many tiny pieces, just like the bones of vertebrates, we usually don’t see intact crinoids in the fossil record. Instead, we more commonly find crinoid columnals, and other disarticulated pieces, scattered among our other fossils. Sometimes, you can find the calyx still intact, but they are often still very fragile. There are some beautiful examples of completely intact crinoids, but these are somewhat rare, and require exceptional preservation, just like the conditions needed to find intact vertebrate skeletons.
Crinoids may seem like an obscure group now, but they were one of the dominant ocean invertebrate groups until they were badly decimated by the end-Permian mass extinction, which wiped out about 85 – 95% of all living things, and is the worst mass extinction event ever recorded on Earth. Luckily, crinoids did manage to recover a bit, and you can now enjoy pictures and videos of the ocean’s very own feather dusters and pinwheels.
As always, if you have questions, comments, or requests for blog topics, please let me know!
For more information on crinoids, check out these resources:
Bryozoans are the coolest little animals you’ve never heard of. And when I say little, I mean really little. As I tell my students, if you aren’t using a microscope, you’re missing the point. You can’t really see anything without a scope.
Otherwise know as “moss animals”, these tiny little critters are mostly colonial, and most commonly found in marine environments. They are generally thought to be related to brachiopods and another group called phoronids, all of which have a specialized feeding organ called a lophophore. The lophophore is a cilliated (tentacled) structure which actively pumps water/food to the mouth (located at the base of the lophophore).
Most bryozoans secrete a hard skeleton in which they live, much like a coral. Individuals within the colony are called zooids. Some types of bryozoans have specialized zooids that only perform one function for the colony, such as providing food, defense, or reproduction. Because they are colonial, bryozoans are capable of both sexual and asexual (budding) reproduction. To reproduce sexually, sperm, and sometimes ova, are released into the water column (some colonies with specialized reproductive zooids will keep ova in brooding chambers).
I won’t get into the systematics (grouping) of bryozoans, because it is complicated, and generally unhelpful to the non-specialist (if any specialists are reading this, I apologize. Just know that I love bryozoans!). However, there are two basic ways that bryozoan colonies can grow: erect, or encrusting.
Erect colonies grow upright into all sorts of beautiful shapes. Some grow into simple branching structures that look like trees , and some, like the fenestrates, grow to look like screen doors (but pretty). Others, like the fossil Archimedes, grow into corkscrew spirals. A lot of modern erect bryozoans look leafy, like a head of lettuce, or bushy.
Encrusting forms are usually flattened, but may grow into large bulbous structures. They can grow into sheets that encrust other organisms, or form large, dense colonies. Interestingly, during much of the fossil record, the majority of bryozoans grow into erect forms, but in the modern, most bryozoans are flat and encrusting. These modern encrusting forms are sometimes called “foulers” because they clog up pipes and foul up the sides of ships.
Bryozoans can form colonies of millions of individuals, but still never come close to reaching the size of other colonial animals, like coral reefs. The result is that bryozoans just never reach the same biomass as other marine fossils, which might make them seem like a somewhat unimportant group, despite being common marine organisms since the Cambrian/Ordovician. Bryozoans are, however, an important group, and totally rad (in my humble opinion).
For example, bryozoans are often used to examine how sessile (non-moving) animals interact with one another, or compete for space. Imagine you are a little larvae that has settled on a susbtrate that is now going to be your home for the rest of your life, and some other larvae settles too close to you, or perhaps on top of you. If you can’t move, how do you deal with this crowding or lack of space? As bryozoans are colonial, they are able to respond and grow the colony in all sorts of interesting ways. Some even have claw-like zooids that can pinch predators or anyone that gets to close. Many bryozoans will compete for “superiority” by trying to overgrow the other colony, allowing us to directly examine competitive relationships, something that is usually not possible in the fossil record (e.g. McKinney 1995).
Bryozoans also commonly encrust other organisms, such as brachiopods, allowing us to examine these relationships “in place”, which again, is a rare occurrence in the fossil record For example, are bryozoans beneficial to their hosts? Do they provide protection/camouflage from the host’s predators? Or are they parasitic, and prevent the host from feeding or moving properly? This is the area of study that I specialized in for my undergrad and M.Sc (check out my publications).
I think bryozoans are fascinating, simply because they operate on a fundamentally different size scale compared to most other animals. They are also very aesthecially pleasing.
Fun tidbit for those of you that read this far: apparently the bryozoan Bugula neritina creates a chemical (bryostatin) which is being tested for use in the treatment of cancer and Alzheimer’s disease. Can bryozoans get any more awesome?
Want to learn more about bryozoans? Check out these resources:
McKinney, F. K. 1995. Taphonomic effects and preserved overgrowth relationships among encrusting marine organisms. Palaios. 10:279-282.
One of the hardest sets of terminology and fossils/structures for students to remember is stromatoporoids and stromatolites. Not only are the names painfully similar, but they also look very similar, until you get your nose next to them. Both can be massive (tens to hundreds of metres), both appear finely laminated, and both can be round or bulbous in shape. The short version is that stromatoporoids (left image below) are body fossils, and stromatolites are more sedimentary structures (right image below). Hard to tell apart, right?
The longer version:
Stromatoporoids are considered to be an extinct group of sponges that were particularly common during the Silurian and Devonian. In Alberta, stromatoporoids formed giant reefs during the Devonian. A large reef formation (biostrome) can be observed in the Moberly Member of the Waterways Formation, which outcrops around Fort McMurray, right underneath the oil sands (McMurray Formation).
A large biostrome unit near Fort McMurray
The biostrome includes massive stromatoporoids
A round stromatoporoid from the Waterways Fm.
A side view of a stromatoporoid covered in oil (black bitumen stains).
Sponges, including stromatoporoids, are the basal group for our own kingdom (Animalia). Stromatoporoids are usually classified within the sclerosponges, a group which secretes a calcareous skeleton (most other sponges do not have a solid skeleton, but instead make their skeletons from distinct hard pieces called spicules). The skeletons of stromatoporoids are put down in layers called laminae, and separated into distinct chambers (galleries) by upright pillars. Water would have flowed through the galleries, where ciliated cells would have drawn nutrients from the water.
Often times, a microscope or hand lens is required to see the laminae, pillars, and galleries of stromatoporoids, but occasionally you get really nice preservation, as in the image above (a specimen from the Waterways Fm.), or this specimen below (from the Potter Farm Fm. of Michigan – Devonian). Another, sometimes more easily observed feature of stromatoporoids, at least when present, are the small bumps that would have been on the outer wall or surface of the animal. These structures are called mamelons, and would have probably assisted with drawing water into the galleries.
Side view of a stromatoporoid from the Potter Farm Fm. (Mid – Late Devonian of Michigan).
Top view with observable mamelons.
Stromatolites are sedimentary structures which are created when a layer of sticky cyanobacteria traps sediment layer by layer, sometimes creating huge mounds or sheets. Stromatolites are one of the earliest organically formed structures, dating back to the Precambrian. A new paper by Nutman et al. (2016) found stromatolites in Greenland which they determined to be 3.7 billion years old!
Because stromatolites are formed by algae/cyanobacteria, they are still technically considered fossils, but what is preserved is layers and layers of sediment. When you look closely at a stromatolite, you will see laminae, but they are not well defined or regular as in stromatoporoids, and they do not have any kind of vertical structure such as pillars or galleries.
One other cool thing about stromatolites is that they still exist today. There are some in Shark’s Bay, Australia that are about 2,000 – 3,000 years old! Check out their website for some more pictures and videos of stromatolites.
Nutman, A., P., Bennett, V., C., Friend, C. L. R., Van Kranendonk, M., J., and Chivas, A., R. 2016. Rapid emergence of life shown by discovery of 3,700-million-year-old microbial structures. Nature. 537:535–538.
It’s Science Literacy Weekhere in Canada, so in celebration, this week’s Fossil Friday post is a short compilation of some great books and reading resources for anyone interested in palaeontology, ecology, evolution, and even the Canadian Rockies.
Here’s a list of some of my favourite natural science related books:
(1) A Natural History of Shells.
Vermeij, G. J. 1993. Princeton University Press, Princeton, New Jersey.
This one is probably my favourite textbooks of all time. If you like evolution, palaeontology, or ecology, go read everything by Geerat Vermeij. He is a genius and arguably one of the top scientists in the world right now.
(2) Fossil Invertebrates
Richard S. Boardman, R. S., Cheetham, A. H., and Rowell, A. J. 1987. Blackwell Scientific Publications, Oxford.
There is another book by the same title published by Taylor and Lewis in 2007.
(3) Fossil Invertebrates
Taylor, P. D., and Lewis, D. N. 2007. Harvard University Press, Cambridge, Massachusetts.
Paul Taylor is another leader in the field, and has done a lot of work on encrustation/biotic interactions. I recommend many of the papers he and Mark Wilson have written.
(4) Invertebrate Palaeontology and Evolution.
Clarkson, E. N. K. 4th edition. 2008. Blackwell Scientific Publications, Oxford.
(5) Geographical Ecology: Patterns in the Distribution of Species.
MacArthur, R. H. 1984. Princeton University Press, Princeton, New Jersey.
This one is pretty math-heavy, but it is considered a classic, and one of the last things MacArthur wrote (he died quite young). MacArthur was another genius and is generally regarded as the top ecologist of all time (he, along with E. O. Wilson, came up with major ecological theories, such as island biogeography).
(6)Predator-Prey Interactions in the Fossil Record.
Eds. Kelley, P. H., Kowalewski, M., Hansen, T. A. 2003. Kluwer Academic/Plenum Publishers, New York, New York.
Full of really interesting chapters on a large variety of animals from a lot of different authors.
(7) Handbook of the Canadian Rockies
Gadd, B. reprint 2016. Corax Press, Canmore, Alberta.
I’ve included this one because it covers everything from plants, to birds, to geology, and even humans! Great for a general audience, and a super fun, informative, and entertaining read!
(7) Living and Fossil Brachiopods.
M. J. S. Rudwick. 1970. Hutchinson University Library, London
A must-read for anyone studying brachiopods. It might be a bit outdated, but it is very comprehensive and easy to read.
There are lots of other classics out there, such as anything by S. J. Gould, M. Rosenzwig, etc., etc., etc.
What are you reading right now? Anything to add to my list? Leave me a comment, and happy reading!