In this episode of the Museum Revealed Podcast we chat to Dr Merrick Ekins about searching for carnivorous sponges deep under the sea, and his Moreton Bay dugong adventures.
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Meet our guest
Merrick is the Collection Manager of Sessile Marine Invertebrates which include; Porifera (sponges), Cnidaria (hard and soft corals, jellyfish, hydroids, anemones), Ascidians, Zooanthids, Hemichordata, Bryozoans (lace corals) and Brachiopods (lamp shells)
He is involved in the collection, identification and preservation of sessile marine invertebrates and some that have a non-sessile phase like jellyfish. He is responsible for the curation of over 60 000 specimens; including 5000 species of sponges, 1000 species of ascidians and 600 morpho-species of octocorals. His job also entails field surveys to Moreton Bay, the Great Barrier Reef and most remote locations including Torres Straits.
Read Merrick’s full biography here.
What are marine sponges?
Marine sponges (Phylum Porifera) are suspension feeders, filtering seawater for organic particles and metabolising many toxic chemical compounds from the seawater excreted by other animals, plants and microbes. Hence their reputation as the most toxic animals on the planet, and thus primary targets of the pharmaceutical industry.
A few decades ago when carnivorous sponges (now known as Family Cladorhizidae) were discovered in deep-seas, that do not filter feed seawater, nor have the cellular structures to be able to do so, but have instead evolved as predators that catch and digest their prey directly (such as wayward small crustaceans).
Interested in learning more?
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Hi, I’m Dr Rob Bell, and over the coming months, I’m going to be taking you behind the scenes of the Queensland Museum Network and their brand new podcast Museum Revealed. From the mysteries of the deep sea to the world’s rarest tank, Mephisto, there’s wedding dresses, prehistoric reptiles, whales, molluscs and much more. Each week we will reveal something else from the network’s collections. What will we reveal next?
Joining us today is Dr Merrick Ekins, who works with carnivorous sponges and deep sea creatures. I am going to need to know a lot more about that, particularly with National Science Week being themed Deep Blue this year – so a lot of things about the oceans, something I find fascinating. First of all, tell me a little bit about the different creatures that you curate here in the museum.
ME: All right, look, my official title is, Sessile Marine Invertebrates. Isn’t that a mouthful? For those of you who don’t know, sessile means that it’s attached to the substrate for most of their life, marine come from the ocean, invertebrates, they lack a backbone. So basically the groups I normally work on are things like hard and soft corals, sponges, bryozoans, jellyfish, jellyfish are cool because they do have a sessile stage – the hydroid.
RB: So I think of them floating around like a blob by themselves, but so in their early life, they stuck on something?
ME: Yeah, most things like sponges. And if you like to think of us, way have a motile stage as well that swims around very briefly. So they are the groups that I work on, so I am going to talk about sponges today and sponges occupy every single habitat where there’s water from freshwater top of mountains down to the abyssal plains on the bottom of the ocean.
RB: Well that’s interesting. But I certainly think of sponges, and I’ve seen them washed up on the beach before. I certainly know that they’re in the oceans. I had no idea that there were fresh water sponges.
ME: Actually, they’re really cool. They actually get carried around on the legs of birds have migrated. Birds that have flown from Russia right down to Australia. They’re carrying the little spores and they land on a fresh water lake around here in the spores come off, then it germinates and off it goes.
RB: So they can live in those two different habitats quite happily and then migrate back the other way again?
ME: That’s right, you might, you might say, OK, these guys have convinced the birds to be their carriers for them.
RB: Wow, what a strange link in the life cycle of a sponge. So tell me, can you take us through a lifecycle or a sponge – how it survives? Because anyone who’s picked one up on the beach, it’s hard to imagine that it used to be a living organism in a way. So how do they how they function? How do they you choose where they live for one of the better way to put it. If they’re basically stuck to something and how do they eat?
ME: Well, they will land on the substrate and they’ll either to asexual reproduction or sexual reproduction, which will either mean they’ll grow immediately, close to one of their parents sponges, or they’ll go across the ocean until they land on a suitable habitat. And they can also survive fragmentation. If you rip one off, it’ll just float off in the ocean, and it will eventually colonise somewhere else as well. So they’ve got heaps of different ways of dispersing. They’ve been around for half a billion years and will be around long after we’re gone. But generally sponges, are filter feeders. So they sit in the bottom of the ocean and they take in water and filter it out and then spit the waste water out. And so it’s what they normally do. But we’re going to talk about a special one today. Carnivorous ones.
RB: So is a sponge, then classified as an animal or a plant. So obviously not a fungus.
ME: Yes it is an animal and there is this classic experiment, where they used to get a sponge and you put it through a blender and break it up into individual like cells, and then you put it through a cheesecloth and so strain it all out. And then provided, you’ve left it all in the right salt conditions, and then it will reform into a sponge, and the cells will go and form into these organelles. So it’s not just you look at a sponge and think they are all the same cells, but they’re not. They’re formed into invalant, vascular tissues and other tissues – they all have their own specific functions. But the one thing I love about sponges is that they’re all totally potent, which is like stem cells. They can go off and become a different type of thing. And when we’re going to talk about carnivorous sponges, they do this funny thing, because I have all sponges are made of silicon. Well, most sponges are made of silicon, and this is unusually long one I have here is a spicule, I’ve got here a metre long spicule, which is only one species in the bottom of the ocean that has a spicule like this, Usually the spicules are are fractions of a millimetre, down to three micrometres in size.
RB: So that’s what you’re holding there that’s come off a sponge.
ME: Yes, it’s just come sponge. That’s one single cell. It looks like a long, thin band of fibre optics. It looks like a fibre optic, a thin, clear sort of plastic, glassy, and it’s actually purer than fibre optics. So this sponge has just done this underwater. It’s amazing. But these carnivorous ones, they have one of these that are modified, well, there are all different shapes. A lot of sponges have really sharp ones, and that’s partly to stop things from eating them. Protection. And these kind of responders have used this to actually trapped prey. And that’s how they do it a little isopod will be walking along and they have lots of hair, like structures on them. And all these individual hairs will get caught on these little things. And so it gets stuck eventually and then because the cells are totally potent, the sponge basically goes, okay, this cell here is now going to go out and engulf and become a stomach thing. So that section of itself into the stomach for the purposes of eating what’s come along. And no one knows how this happens, of course, is all whole realm of science yet to be discovered?
RB: Yeah, that is quite amazing. And so, with carnivorous sponges, I suppose what they feed upon probably depends on the size of the sponge to a degree. But what sort of size creatures are we talking about? You know, tiny, up to medium size?
ME: We’re talking about tiny talking about up to several millimetres, so anything that just happens to be crawling or floating on by and get stuck with you, that’s right. Yes, these guys, it occur below 1000 metres and all the way down the abyssal floor, and the reason they’re down there so deep is that there’s so little food. They talk about taking 1000 years for a centimetre of sediment reach the bottom of the ocean floor. So a lot of these have to grow out of a sediment. And so they’re their own little structures. And I’ve got one here, I will describe it and you can see it’s got like little roots, and then it’s got one big long filament that’s like 10 centimetres long and at the top, it’s got what looks like little hairy processes, and that’s where it’s going to do with catching because they’ll be above this layer of snow and then, when something.
RB: So it stops there waving around, waiting for some food?
ME: Well, not so much waving, but eventually it will get something. And the thing is that there’s so little food coming along, that’s why they’ve decided to swap from a filter feeding to a carnivorous lifestyle they’ve decided there’s more foo to be caught that way. So evolved.
RB: So they have developed that technique I suppose to be able to survive deep down in the abyss. Now, look, I find the depths of the ocean that far down kind of probably equal parts fascinating and well, creepy is probably the wrong word. But just be strange, I suppose. A strange world because light ceases at what sort of about 50 metres is it or something like that? But you’re not talking about 100 metres with these things. You’re talking like kilometres down. So there’s there’s no life and an immense pressure. So it just seems strange to me that they have evolved to live down there, and not just by themselves, obviously. Then there’s always something for them to feed off and to reproduce. They don’t change shape greatly when they come up? Or do they? Do they lose their structure when they come up?
Do they change greatly when you bring them to sort of surface pressures?
ME: Yes and no, these ones I have got here do not. But they used to collect ones and before, and it was done recently as well. Like the Challenger expedition, that 1800s and they put down piano wire to the bottom of the ocean. And the this is probably one of the first expeditions to work out what’s in the ocean, and so they have to reel it up. So you’ve got 12 kilometres of cable out, and then you got to pull it back up. And they describe these sponges, these carnivorous sponges, which were describe later. And they had all these flaccid bits to them and they didn’t know what they were. And it wasn’t until someone went down with an R.O.V about 20 years ago, and they went off deep underwater, and they discovered that these things are actually spheres of air or gas bubbles so that it holds itself up. So it’s floating above the surface. We’re moving out of this out of the snow like effect. Yeah, it’s crazy, I guess, But again, that’s an example of when they don’t have but ones that are made of silicon. They come up because of water. Down there is, like one or two degrees by the time you bring up the surface, everything’s parboiled as well.
RB: Of course, everything changes from 18 degrees, and it’s of course, it’s boiled up as well, under pressure.
ME: But because they’ve got this hard silicon. Most of these don’t change too much again.
RB: We’ve obviously chatted a little bit about sponges. I want to go into how you find these sponges because you mentioned that some of them are kilometres down in the abyss where it’s dark and freezing. How do you go about getting them up to the surface? How do you find these things. You’ve been out on expeditions to get these things.
ME: That’s right. And one of the exhibition’s we did a couple of years ago on the CSIRO’s Investigator vessel, which I’ve named one of my sponges after. We were there looking at the end of the continental shelf. It comes out and drops down the abyss off Australia is four kilometres deep and so we went and picked a few spots of 2000 metres, like halfway down the slope at the bottom, and to get there we didn’t have a camera or ROV that could go deep enough. So it was basically it was dropping, dropping a different type of sleds off and lowering them down and the whole of telemetry going on to try and track where the boat is and where it is in the water. You’ve got like 12 kilometres of steel cable our and because the equipments quite expensive and it’s quite rocky down the bottom, you go over with the multi beam sonar and find areas like a landing, runway if you like, and you go okay we’ve gotta try and hit that because otherwise, if you hit on it and then you can run along for a couple of kilometres because these things down there are quite far apart, they’re so rare, you know, it’s not like a rain forest. It’s more like going through a desert, you know, and you occasionally hit something. But for the moment is because the boats moving along with current to pull it and serve it if it comes up against a rock there is a high chance, they’re going to suddenly put 20 tonnes of strain on the cables and break cables. So that’s why you got to try and land on these spots. We also had these other type of sleds. There was one for collecting isopods. It was like a Santa sleigh, if you like, so it would have these Bombay doors which are closed, and then when it touched down the bottom, the lever would activate the bombbay doors open and it was about a foot off the ground so that what is doing the front of the slow sleigh was stirring up the sediment. So they were drifting and they were caught really carefully. And it’s really good, because these little isopods we are talking about are a couple millimetres in size up to several centimetres. But the thing is, before people they’ve been described and people only had the body. And for the first time ever, they realised, Oh, these guys have antennas which are three or four times the length of the body. But no one had ever seen that before, because normally you have, like this big metal cage and if you imagine going through the process if a rock gets in there, it’s bashing around with it. And you’re travelling four kilometres on the bottom and then you’ve got to travel another eight kilometres from the bottom and it’s like a washing machine. You got mud in there, so it’s all getting mashed up. A lot of times it comes on deck. It’s all covered in mud and so you have to try and sift it out and get rid of all the mud. Which, of course, washing away your precious little samples.
RB: Yes, and for the more fragile ones they don’t make it up in the condition that they were.
ME: That’s exactly right. I’m chasing these carnivorous sponges which are only a couple of centimetres long, so you can imagine if you pulled up several tonnes worth of stuff in a big net, then you have to wash it out.
RB: So to put this in context. You’re essentially like if a kid was at the beach and was doing something similar to what you’re doing, but obviously much, much more. The scale would be like tying a little plastic bucket, then dragging it through the shallow water and picking up stuff. But of course you’re doing this four kilometres down with 12 kilometres worth of steel cable, where the steel cable and you’re kilometres offshore. So how far is it how long do you take to get to the continental shelf, typically in Australia? So how far out you go before it drops off?
ME: I suppose it is between 30 and 100 kilometres out and that is in the Coral Sea. It’s a long way because of Coral Sea comes right out off a Big Plateau and the moment there is another expedition heading out there. I think the Falcor expedition is heading out to go and do some more because they’ve got an ROV too, which has a remote a camera and a little are you can go and grab stuff. So we took one up to the Osprey Reef about 10 years ago to try and pick up some samples too.
RB: I’ve always been fascinated by a few deep sea footages I’ve seen, it’s just because of these ancient kind of things that squiggle around down there and don’t have much shape and what not? But I think I think it’s crazy that they lived down there in the dark and are probably good snacks for seals and other things that come along. But just the variety of creatures that live down there is just strange. But it’s not all down there. You also go and collect sponges from a little closer to home a little closer to the surface. Tell me, how do you get those ones?
ME: Yeah, almost a lot of what we do is scuba diving as you probably know, the coral, it’s all photosynthetic, so young it dies out after a certain depth. And so we go out and basically dive down and photograph stuff underwater and then quick little sample, then bring it back and to identify sponges and octocorals and things. It requires a lot of microscope work. You look at this fine detail structures, unfortunately, so, unlike fish your birds, which we can flip through a book and see things. One hour in the field, usually generates a week if not a month or two of work. So you go in once, give a dive trip, and every time I go, I will pick up probably about 30 sponge or so, and pretty much one of those will be a new one to science so there is so much we don’t know. I mean, the carnivorous sponges I got from the that one trip. I got 17 brand new species to science.
RB: Where do you go?
ME: So we go around the Great Barrier Reef and also Moreton Bay. But so much is unknown. It’s really I mean, for example, in the just a sponge is in the museum collection here. We’ve got over 5000 morpho species, but probably about 800 of them have been described already. So I’ve got 4,500 species to describe.
RB: So you’ve got a lot of work ahead of you. I want to take a really quick detour from Sessile Invertebrates because I heard you also go out on Morton Bay tagging dugongs.
ME: Yeah, I help out. Well, it’s a fun project. I’ll help out with Janet Lanyon from University of Queensland. Um, well, basically, we get a dugong and we find a herd, and then you try and separate one from the herd, and then we follow it and we try and get it to do a bit of a run. So tire it out a bit and we usually get it on what we call third breath. It usually does about two minutes, but it kind of comes up. Takes a breath on the third breath as it comes up, it then arches its back and its head goes underwater. And then four of us jump off in coordinated off a boat and two of us grab it round the back, and then other two of us jump in front and try and grab around the pec. And then it’s like several minutes, heavy duty, rinse cycle and the dugong bucks and tries to throw us off.
RB: So it’s like a dugong rodeo?
ME: That’s exactly what it is. It’s funny because sometimes from the boat and you jump off and you go, where are there? Other times you might see a dugong going past at high speed and you go what’s going on or sometimes see it going past with one person attached. You’re the only one who gets on it and then try and grab them. And if you could stay on the 30 seconds and other people could grab onto you and climb up and then well, how so? It’s just quite rough in a way, it is. But on the other hand, it’s really gentle because where this using our hands and our bodies, whereas when they do this with manatees overseas, they have to use cranes and nets and lassoes and things. We do this and we just sit in the water with it. And then we could take measurements on a samples and tag while the dugong is in the water, whereas overseas they have these boats and they lasso them and then they haul it out with crane on the deck and while it sounds rough what we do, and it is physically rough – rough enough for us, we come back bruises all over my body probably rougher on you than them.
RB: And what’s the purpose of, I guess, What’s the end result of a lot of this? Is it to track their movements around Moreton Bay, see where they’re going, see what the population is?
ME: It’s usually population it’s to work out how big the population is and now you can take a genetic sample to work out who’s related to who so can see with and whether these populations are mixing with ones like Harvey Bay. And also by doing a health survey. Because no one knows what a healthy dugong is. There’s no one knows anything about its metabolic requirements or anything, So it’s basically establishing baseline data so we can work out how they’re going to go in the future.
RB: They are such fascinating animals and they’re on our doorstep here in Moreton Bay.
ME: It’s one of the few places of the world where we can see these amazing animals. In Japan, they have seven of them, I think the six now. But you know, every now and then one gets caught by fishing and they’ve just got such a reduced population. Most other parts of the world they hunted for food and in great numbers. So Australia is the stronghold for dugongs in the world. And we got some right here, right next to a major city.
RB: Thanks so much for joining us. Dr. Merrick Ekins for the Museum Revealed podcast and listening. What did you uncover this episode? Interested in learning more? Follow Queensland Museum on social media at @qldmuseum, or head to our website at qm.qld.gov.au. While you’re there sign up to our eNews list to be the first to know when our next season will be revealed. Until next time, stay curious!