FORMAL ATTIRE REQUIRED! The Tuxedo Urchin Spawning Event

Added: 2026-05-05

[00:00:00]What is up you guys? Welcome back to Title Gardens. In this video, I want to talk about my odyssey in trying to breed sea urchins. It starts a long time ago, maybe 3 4 years ago, when I was talking to Jamie Crags from the UK. Jaime is known for the sexual reproduction of Acroppora. But in his original paper, one aspect of that aquaculture program was co-breeding tuxedo urchins so that those little baby acropporas get cleaned up. The interesting thing to me was that he was growing so many of these small little baby urchins that he had no outlet for them at all. He had to basically sell them to whomever he could. I'm looking over here at my coral farm. I know that I can use practically an infinite supply of these herbivores.

[00:00:54]Whenever I try to order sea urchins, it's such a crapshoot. Often times, we'll place an order and let's say we place an order for something like 90 urchins. We might only be getting 60 of those 90. 30 of them might have died before they were able to ship to us. And then on top of that, within a week of us receiving those 60, maybe three of them are still alive. Those three urchins, what's the math on that? A couple hundred a piece. The whole order is $800. I get three urchins out of it. Not the best math in the world.

[00:01:31]I like tuxedo urchins specifically because to me, they are an elite herbivore. They can chew down macro algae. They can chew down calccarious algaee, the coraline, and they do it very gently because there's plenty of other bigger urchins that bulldoze. And we've even had one that was able to grab a 25 coral tray and drag it up the side of the glass all the way to the surface.

[00:02:02]Tuxedo urchins don't do that. And the last super appealing thing about the aquaculture of sea urchins is that the smaller they are, the better. Sometimes when they get to that 2 to 3 in size, they no longer can scoot in between our frag plugs, and that's usually where we need the most cleaning. The babies, they can get all the way up to the flesh of the coral in the middle of a tray.

[00:02:28]They're perfect.

[00:02:31]When we're collecting urchins out of our tank, we're obviously hoping for a split of males and females. I'm not an urchin biologist, so I don't know how to identify which are males and which are females. So, we're grabbing a dozen and hoping that we don't grab all dudes. The other thing leading up to our attempts to spawn urchins, we actually have to beef up their nutrition. And this is something that has a lot of room for improvement for us. Often times these urchins are surviving in your tank, but they're not doing so well that they're able to produce healthy gametes. So it's very ironic that we need these guys to mow down a lot of our algae. But in addition, we have to feed them more algae. Once we have our dozen urchins collected, we have to induce spawning.

[00:03:25]Basically, what that amounts to is that we have to gently stress them to give them the impression that they might die.

[00:03:34]And we have to do this without actually killing them. There's three popular techniques. The first popular technique is to change the salinity ever so slightly. We have not tried that.

[00:03:48]However, it is also the least popular of the three techniques. Second technique by far the most popular at least as far as like this industry is concerned and that is heat stress. If you slowly increase the temperature of the water from about let's say your tank is 77 78 you can increase that temperature slowly to a maximum of about 85. Anything above 85 you're risking some serious cellular damage in these urchins. You don't want to go above that. We've mistakenly gone above that before. We did lose a couple of urchins. Not the goal, right? In this process of slowly stressing them out over the course of let's say 15 minutes to get up to temperature, they can be held at that temperature for no more than 60 minutes. So you are working on a hard cutoff at that point. Lastly, you can inject them with potassium chloride, specifically 0.5 molar concentration potassium chloride, 1 ml, maybe 2 mls per urchin. This to me is the most risky. Way back in college, 1996, let's say, right around that time frame. That was the last time I actually bred urchins was for genetics lab. and we injected potassium chloride into these urchins. They died. That's again, it's not something that I want to take lightly. I would prefer to obviously not kill my urchins. This is the laboratory standard technique because unlike the heat stress that could take up to 45 minutes to an hour, potassium chloride works practically immediately and it's highly controllable in the sense that you're dosing it. For this attempt, I am trying heat stress.

[00:05:41]In the past, when I tried this, I had all the urchins together in a tub and slowly increase the temperature. This time, I'm doing it slightly differently.

[00:05:51]I'm individually setting the urchins into their own beaker, and I'm putting them into a warm water bath. There's some benefits to this. This way, if one urchin were to spawn, I know it's a male or female. It doesn't pollute the water of any of the other urchins. It's a lot cleaner because if one urchin spawns, it practically immediately clouds the water for all of the urchins. And at that point, it can be a little bit difficult to stay organized. Another benefit is that the heater is not exposed to the urchins. So, in that sense, you're never risking an urchin crawling onto the heater and cooking itself, cuz the rest of the water might be 80, but that heater is 98. And I guess lastly, it's just the organization of having them all isolated. You're never at risk of kind of just losing track of an urchin as it crawls around and on top of the other ones.

[00:06:48]Once you get to temperature, you have to look for signs of spawning. It takes about 15 minutes or so for the males to start spawning. They'll start to release like this little cloud of white sperm.

[00:07:00]And at that point, what I do is I collect that sperm with a pipet, put it into another small container, and put that on ice. You can keep sperm on ice for about 45 minutes, which is pretty much as long as you need. If you leave it at room temperature, if you leave it in salt water, it'll start to react and the sperm won't keep as long. So that's what the ice bath is for. In this particular attempt, we got seven of the males to spawn. The nice thing about once you get the males spawning is you no longer have to subject them to all this heat stress. They've done their job. You can take them, put them back into the tanks. We used this as an opportunity to try to sort our urchins a little bit better. So we put all of our males into one particular tank. And once we kind of identify the females, we will put them in a completely separate tank.

[00:07:50]That way, we know that we can feed those females more. It'll be less of a guessing game in the future. Whether you've picked all males or all females, you should be able to get a 50/50 split at this point.

[00:08:03]Let's talk about collecting eggs. This is a challenge because the the females take longer with the heat stress. They can take anywhere from 45 minutes to the full hour before you hit that hard 60-minute cut off. The males take 15 minutes, the females take 45 minutes.

[00:08:20]These jokes are writing themselves. The behavior that I'm looking for, and this is specific to the females, is called wafting. It's where their little tentacles start to extend further and start to do this like rhythmic pulsing almost, almost like a pulsing xenia, if you can imagine that. Soon after that, they're going to release this cloud of eggs. Theoretically, in this particular attempt, it was 45 minutes. We're not seeing any eggs. It's 50 minutes. We're not seeing any eggs.

[00:08:52]55 minutes. I'm starting to get worried because we've got our sperm on ice already. I really need one of these remaining five urchins to give me something. But if one of these five doesn't produce any eggs, this is going to be a really short video.

[00:09:10]I didn't want to inject these urchins.

[00:09:12]So, one video that I've seen is that instead of injecting the urchins, you can do this topical approach where you put a couple of drops of that onto the urchin. That will relax their muscles and hopefully get them to spawn. We gave that a go and nothing.

[00:09:31]we're going to have to inject them. Once we were almost at that 60minute cutoff, I made the executive decision to inject them with potassium chloride. I have a lot of reservations about jabbing these things with a needle. It kind of freaks me out a little bit. I felt so bad. I apologized to each of the five that I injected, but I gave them each 1 ml, gave them a little bit of a shake, then kind of just waited.

[00:09:58]One of them almost immediately spawned.

[00:10:01]And this is where that microscope comes in super handy because immediately on first glance it doesn't look a lot different than sperm. But I am now able to inspect it under a microscope and sure enough we have eggs. The other four gave me nothing. Not after 1 hour in the warm water bath. Not after the injection. Nothing. I am thinking that we have a nutrition issue. They're not getting enough calories and healthy fats to produce eggs. But I did get one of the 12 urchins to give me eggs.

[00:10:40]When we're fertilizing the eggs, we have to first dilute that sperm that we've put on ice. All of the guidelines say less is more because there is a condition that you can cause called hyperspermy.

[00:10:55]If multiple sperm are fertilizing a single egg, that becomes unviable.

[00:11:00]You'll basically kill the egg. It is way better to introduce not enough sperm than too much. So, I was very conservative with it. I took just a few of the eggs and put in this very dilute sperm solution over top of them. And what I'm looking for is about an 80% fertilization rate. And you might be wondering, how on earth do you tell if these eggs are getting fertilized? A fertilized urchin egg will form a halo.

[00:11:32]After about like 5 to 10 minutes after the introduction of sperm, you should start seeing these eggs develop these halos. If you can see 10 eggs under the microscope, you're looking for eight of them to get fertilized and the other two remaining unfertilized. So that 80% fertilization rate is kind of the sweet spot. Again, it is way better to have a bunch of unfertilized eggs than losing the entire batch to hyperspermy.

[00:12:02]Fast forward a few more minutes. What will happen is the healthy eggs will start to float up. They'll become more buoyant and they'll float up into the water column. the unfertilized eggs, the sperm, and all like the debris and everything like that from the spawning in general, that will all settle down towards the bottom of the beaker. You have to start to rinse these fertilized eggs. And the way you do that is you decant them over and over and over again to kind of leave that what amounts to like detritus layer of unfertilized eggs and whatnot at the bottom of the beaker.

[00:12:42]And so all the clean fertilized eggs will remain up top. What I did was six rounds of decanting from that single original beaker. And at the very end, I didn't want to discard whatever was in that beaker because I only had one female spawn. All of these eggs, as far as I'm concerned, are precious. Now, that particular original beaker has the most chance of failing and spoiling, but we'll give it a go. At that point, it's already received a 95% water change from all the different uh decanting efforts into the other beers.

[00:13:21]One interesting thing that I'll share with you guys, when I'm looking under the microscope, I came across these flatout alien looking things. They look like alien claws. And I have no clue what I'm looking at. I eventually learned that they are called petty celery. I'm sure I brutalized that pronunciation. What those are for is protection for the urchin. They're actually venomous. And supposedly fish don't like to mess with urchins because of these little twitchy things.

[00:13:58]Now that we've got some fertilized eggs, the development of these eggs happens way faster than you might think. We missed a lot of the early phases just because I was off doing other things in the coral farm while these beers just sat in their warm water bath. The next time I'd looked at them, they were already in the blastula stage. They probably already went from the one egg cell to a 32 cell blastula. These eggs are going to stay in those beers for the next 48 hours. No water flow, no nothing. And they just sit there sitting in the water column, neutrally buoyant, and they just sit there developing. The next time I look, definitely more cells.

[00:14:41]Eventually, the next day, we are looking at what is called a prism phase. They kind of have this cool little triangular pyramid shape. Towards the end of that 48 hour period, they start to turn into earlyphase plutous. And so they're taking on this jellyfish look if the jellyfish was made of crystal. Very, very cool stuff.

[00:15:08]At this point, I'm going to start slowly introducing them into our crystal tank.

[00:15:15]Creole tank is basically like a jellyfish tank. We have to keep these guys suspended in the water column and don't allow them to settle. If they settle, they might get bacterial infections and stuff like that. So, jellyfish tank it is. My goal was to slowly decant these larve into the chrysal tank over the course of about 3 days. That is obviously an opportunity to do a water change on those beers.

[00:15:40]Also, like the most mature ones that are in the water column will end up in the creole. After that 72-hour period, I would say that the vast vast vast majority of the larve are in the creole.

[00:15:53]Everything else kind of on its own, we just put them into a tank.

[00:16:00]Once they are in that plutous phase, swimming around the chrysal tank, now we've got to feed them. We are feeding them a mix of three different phytolantons. We are feeding tsorris, rodamonus, and ketocerus. And we've chose those three because that's basically the gold standard when it comes to feeding urchin larve. They're very complimentary to each other and they greatly accelerate their development in the chrysal tank.

[00:16:28]Accelerating through this planktonic phase is really attractive to me. This is by far the most laborintensive part of this whole thing. There is no filtration on a Chrysler tank like this.

[00:16:41]So I have to be the filter. That means two water changes per day. And the reason that I have to do two water changes per day is I need to control the bacteria population because heterotrophic bacteria doubles in population every hour or something like that. And once that gets to too high of a concentration, it's going to crash your colony. two water changes a day just to knock down all the bacteria and to help process the waste from both the phytolanton spoiling and also the waste products from the urchin larve itself.

[00:17:18]Theoretically if I was just to feed Topis it would take up to 30 days for these larve to settle. If I add rodamonus to that mix I should reduce that time frame from 30 days down to 20 days. If I add in that third phytolankton, the keto, it can bring it all the way down to 15 days. The difference between 30 days and 15 days is a lot of water changes. And not only that, but it's a lot of risk.

[00:17:50]Every single time you're doing a water change, you're introducing a lot of chaos in there. You're probably killing a few here and there. The fewer days, the better.

[00:18:03]The way that I do the water change is with a parastoaltic pump and a siphon tube. The siphon tube is basically a DIY project. Stick the siphon tube down into the water and then I parasultic pump out very slowly. Really important that I don't want to pin a whole bunch of these little urchin larve against that screen aggressively. No matter what, you're going to get them stuck on that screen.

[00:18:29]But every now and again, I like to pour just a little bit of new salt water down that tube, flush them out again, parastolic pump some more. Once I remove about 20 to 40% of the water, then I take out the parastolic line and I start to refill the chrysal tank and I like to pour that down through the siphon tube.

[00:18:53]I save a little bit of room towards the top because now I've got to top off the phytolanin again. All I'm looking to do is introduce a very slight green tinge into the water. I'm not so worried about urchins not getting quite enough food.

[00:19:07]I'm worried about the nutrient and bacterial load going crazy.

[00:19:13]While they're going in this grail tank, they will start to develop more arms. So you start off first with the prism and then into a forearm pludius and then a couple days later you'll get six arm and then maybe like 4 days after that it'll develop eight arms.

[00:19:34]After it develops eight arms, I now have to pay really close attention because it's going to start developing what's called a rudiment where the head of that jellyfish shape is going to start changing and it's going to start to send out what looks like urchin spikes through there. At that point, these things are going to try to start to settle. They're going to exhibit this testing behavior where they're going to start to try to land on the sides of the cryal tank and just dabble at the idea of touching down and lifting off. At that point, I should start to collect them with a turkey baster and put them into our settling tanks. This sounds like a lot, but this is only halfway there, if you can believe it or not. So far, thrilled with how things are going, but there's quite a bit more in this journey to go. But that is a story for another time. Till next time you guys, happy reefing.