The Sponge that Might Have Been Us

A story by John Pearse, PhD.

Sponge Oscarella

What do you do when you find your lab samples contaminated with a brown scuz? If you’re a biologist, like John, you hunt for an explanation. Sherlock Holmes would have been proud. John’s sleuthing took him to a Venezuelan student, a Brazilian researcher in France, a discovery in Vladivostok, Siberia and to the tidepools off Carmel, California. What he found was a species new to science right here at home, the most exciting find for any researcher.

John’s introduction is available in another blog post.

You can watch John’s story on Youtube: https://www.youtube.com/watch?v=7BRL1VIEL5s&t=451s

The other story that I really wanted to talk about a bit as a scientist, maybe people would appreciate, is that I had a lab in Santa Cruz where I did a lot of experiments. We had running seawater in the lab, and we started to get a brown scuz growing on the glass. I scraped some of it off and looked at it under a microscope, and I realized it was a sponge. But it was a sponge that had no spicules. Most sponges have lots of either calcareous or glass spicules that hold them up. This was one that has no spicules at all. It doesn’t even have the fibers that make up a spongy sponge. It’s just tissue. It’s called a slime sponge. It’s just a slime that’s on the rocks. I’d never seen anything like it.

I thought that I knew that there was supposed to be a sponge here that didn’t have a skeleton, and I’d never seen it, and I thought it must be that. I was looking at it, and spending a little bit of time. It was fascinating! I could look with the microscope right through it and see the feeding chambers inside. The embryos it had. So I thought this would be a fantastic animal to look at and keep and culture.

But nobody’s ever been able to culture it. It grows on the sides of things. But we had a graduate student who was really good with sponges, and she was from Venezuela. She came in the lab, and I said, “Christina, what do you think this is?” And she said, “Oh, I don’t know, I’ll take it back. I can’t tell. I’ll have to look at it with a scanning electron microscope.” And she came back and she said, “John, that’s Oscarella, a genus which is only known in the Mediterranean, and in Europe. It’s not found here.” Oh, my goodness. How did it get here? It’s a slime.

Then I was up at the Aquarium[1]. I went over to the Aquarium and I saw it there, in the Aquarium. Maybe the Aquarium brought it here, for some kind of thing. They have animals from the Mediterranean, and it GOT OUT! Got somehow into my lab. I couldn’t figure out how it could get into my lab.

And I talked to people at the Aquarium, and they said, “Oh yeah, it’s terrible!   It grows up sometimes in the spring, and you have to scrape it off quickly. What is that?”

So I was worried a little bit about it. And after I retired, I used to take my students to Carmel Point – all along here – but Carmel Point was one of my favorite places. At Carmel Point there’s a little red flatworm, which is described as endemic to the Monterey Peninsula. It used to be everywhere. You’d go out and there’s a green sea lettuce, alga, that is there, and there’d be red spots on it. And that’s another one of those things you remember from the past, and it’s not here now.

I used to take my students out, and I’d try to stop and I’d say, “Look at these little flat worms. These are the simplest flatworms, simplest animals”, and I’d go on about it, and they’d look at me and go, “What’s he talking about?” To me they’re really fascinating, really interesting bilateral animals. They don’t have a gut. They just have a kind of incision, and they’re predatory. They jump on lower crustaceans and enclose them. It’s a terrible way to go. You can see the thing inside trying to get out, and it’s engulfed. But they almost disappeared.

And so after I retired, I said, I’m gonna have time to really look for them, see what happened to them. They were so abundant here. They’ve all but disappeared. I can hardly find them.

And as I was looking, I found this sponge. And that’s when I thought, “Oh my goodness, the damn thing’s out.” It’s gonna take over the coast. We need to find out what this is! I wrote to Christina who had gone back to Venezuela by then, and said, Can you help me? We need to find out what this is!” And she said there’s one person in the world who knows anything about this and he’s Brazilian, and he did his PhD in France.

So I contacted him, and he said, “Yes, if you’ll fix them for a transmission electron microscope, that’s the only way we can tell them apart. They have no characters.” So I did, and he found some characters that he said he’d never seen before. It’s a different species. So we described it. It was the first species of that whole group of animals found in the Pacific. About the same time there was another species discovered, which is found in Vladivostok in Siberia.

At any rate, there it was. It turns out this sponge is really fascinating, I think, because it’s a sponge that doesn’t have any characters like typical sponges. But it does have some characters that other sponges don’t have, that we humans have, in its cells. The cells, the tissue, most animals have kind of a basement membrane underneath the epithelium. Sponges don’t – excepting this one does! So its sperm is more like other animal sperms than most sponges. So this one looks like it could be almost a sponge that was us five hundred million years ago, though it turns out it’s probably not.

Since we described it, here’s another interesting thing.

There’s a student at Berkeley who was very interested in sponges, and I met him at a conference, and he gave an organizer’s symposium on sponges. So I went up to him. I said, “Scott (his name was Scott Nichols), have you looked at Oscarella? He says, “NO, NO, I can’t get any! Those French! You know those French they have all that Oscarella, but they won’t send me any. They are so secretive and oh…..” “Well, come to my lab.”

So he came down to my lab. Did some nice studies. We published all of them about the characteristics, because he looked at them as somewhat of a transition between sponge-like organization, and the rest of us. He did molecular stuff on them, too, and found out that they are certainly a different species. In fact, there are two species now on a molecular basis. He hasn’t named the second one yet, but they now have their own genome. If you’re in biology and you have these relationships with genomes, with different groups of sponge – there is this species, which was only described in 2004. So that to me was very exciting. It’s a very different kind of story than diving for abalones at Año Nuevo, but it’s my story.

Sponge Oscarella

Sponge Oscarella

Thank you for sharing your story with us John!

[1] Monterey Bay Aquarium