Posts Tagged carnivorous sponge

Sunday Spinelessness – In the news David Winter Aug 08

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Spineless creatures have been all over the news this week. We’ve had strange beasts appearing on beaches, wondrous finds from the deeps and (apparently) a new front on the war on cancer.

Let’s start here in New Zealand with a surprising find on a Wellington beach.

Children touching a giant squid

Photo from stuff article /Emma Best

That’s a giant squid (Architeuthis sp.) and at 3m long it’s a baby, full grown females can reach 13m. Giant squids are really deep sea predators, so beachings are relatively rare. This one appears to have been in a fight. We don’t know too much about the food webs at the bottom of the ocean, sperm whales are the only creatures known to take on adult giant squids but sharks and other whales might very well attack sub adults like this one. As an aside, studying parasites might be the best way to work out who eats who in the deeps. When you dissect a shark or a whale its stomach contents give you a picture of what it’s eaten recently, when you look at its parasites you can paint a picture of what it’s eaten over its lifetime. However the squid got its injuries, they proved fatal. it washed up dead and was returned to the ocean with the next high tide.

Then there was the announcement of the results of the Census of Marine Life, an inventory of the species living in the earth’s oceans. The news of that story was almost universally illustrated with pretty pictures of weird animals photographed from deep sea submersibles. Here’s a particularly striking example of the genre, an amphipod with a house which showed up in the Guardian and National Geographic:

A shrimp-like cristacean inside a hollow tube

Photo from Texas A&M press

Obviously, that mean-looking shrimp-like amphipod is a spineles creature, but it might suprise you that its transluscent home is also an animal. In fact, it’s one of your closest relatives in the biological world. It’s a salp, a relative of the sea squirts, and it’s a member of the chordata – the same phylum as the all the vertebrates. Matt Cobb has all the details in his guest post at why Evolution is True.

Finally, scientists published the first complete genome sequence from a sponge. As has become customary for genome studies, the press releases and the resulting new stories all suggest that these DNA sequences will help us fight cancer. Well, perhaps. Cancer is ultimately about uncontrolled cell proliferation and sponges are the simplest animals to have to find a way of marshalling thousands of cells into a single body. But is that really the only reason we should be exciting about a tool that helps us to understand the origins of multicellularity, or being able to see where the precursors of the development programs that pattern the bodies of more complex animals came from? I’d like to think the average reader is just an excited by a little scientific awe as they are by some ill defined and far off medical benefit. (Before I sound too grumpy I should say that the press release from UC Santa Barbara was really very good, it’s just a shame some of those points didn’t get picked up in the reporting.)

To those three stories you can add a call for insects to replace red meat, sub zero octopus venom and a BBC tour of invertebrate collections form the Gulf of Mexico. It really was quite the week for invertebrate news.

Sunday Spinelessness – Attack of the Killer Sponge! David Winter May 23

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Chondrocladia turbiformis, a ruthless carnivore hauled from bottom of the sea off new New Zealand by NIWA scientists, has been named among the top ten new species described last year. This abyssal predator isn’t a kraken, a plesiosaur that time forgot or even an improbable (but awesome) hybrid. It’s a sponge.

It may come as some surprise that a sponge can be a carnivore, or even that sponges are animals. Sedentary as they are, sponges tick all the boxes for inclusion in the kingdom Anamalia. They eat other organisms to make energy and build their body (differentiating them form plants and algae), they have cells enclosed by membranes (not cell walls like plants and fungi) and they are truly multi-cellular, with specialised cell-types (which sets them apart from protists). On the other hand, sponges are pretty unusual animals. Sponges have no nervous system, no gut, not circulatory system and their cells don’t form tissues. The relative simplicity of sponges helps us to understand the evolutionary history of animals, by plotting some of the characteristics of modern animals onto a phylogeny we can see what order those characters evolved in:

How the sponges relate to other animals. The protostomes and deuterostomes differ from each other in in fate of the blastopore, the first opening to form during embryonic development. In protostomes it becomes the mouth, indeuterostomes it becomes the anus.

So, sponges are useful in trying to understand the evolution of animals. But we shouldn’t view modern species as steps along a path toward more complex animals. Sponges are amazing creatures in their own right, for a start they’re the only animals that don’t have a mouth. Most sponges feed by drawing water into the their body through pores and absorbing bacteria and small algae from that water with specialized cells on the inner surface of their bodies. The cells of the inner surface have two sets of projections to help them with this task. The tail-like flagella which beat together to get water flowing over the absorbing cells and the hair-like micro-villi which increase the cells surface area and make them more efficient absorbers (the guts of more complex animals play the same trick on a larger scale). Most sponges further increase the efficiency of this process by taking the form, and the function, of a chimney. The tubular forms are help together by a mesh of small calcium carbonate structures called spicules.

Filter feeding works well in relatively nutrient-rich shallow waters, but scientists have pulled odd looking sponges up from the bottom of the ocean. Some of those sponges still had the characteristic sponge filter feeding system, but others had lost it all together. Quite how these strange sponges were getting by in the dark and unproductive abyss without even the normal sponge feeding system remained a mystery until 1995 when French researchers found a relative of the deep sea sponges in a relatively shallow submarine cave. Abestopluma hypoa gave scientists their first chance to observe these sponges, and what they saw was amazing: it was a carnivore. In life A. hypoa projects a set of filaments into the water. Those filaments are covered in tiny spicules which act like Velcro (that’s the author’s own simile) grabbing passing crustaceans and holding them in place. It takes a while for the sponge to get its meal, cells make contact with prey within an hour but the actual ingestion follows a period of cell growth and movement which completely covers the animal after a day. It takes another couple of days to completely digest the crustacean.

Since that first discovery scientists have discovered many more carnivorous sponges, with a surprisingly large number coming from sea mounts off New Zealand and in the Southern Ocean. The topic of today’s post (I knew I’d get to it eventually…), Chondrocladia turbiformis, is one of the newest killer sponges, and it looks a bit like a mushroom:

The Chondrocladia are a bit of a special case among the carinovore-sponges because they have retained the rudiments of their filter feeding system. They don’t appear to use it to supplement their diet, rather it’s been re-purposed to inflate a balloon like structure the sponge uses to help capture prey. (For a stunning example of this structure in a live sponge see the photo that illustrates Olivia Judson’s article here.). But the thing that really distinguishes C. turbiformis from the already amazing carnivorous sponges are its spicules:

Beautiful as they are, those symmetrical curved claws in D and E are run of the mill for Chondrocladia. The spinning top spicules in G and H are something quite different. It was only through the description of C. turbiformis and a related species C. tasminae that it became apparent these spicules, with have been named trochirhabds, are present in some modern Chondrocladia species. It’s not extactly clear what these cool little spiclues are doing in modern Chondrocladia but they give us a clue to the history of carnivorous sponges. Spicules just like the trochirhabds described from C. turbiformis have been found in marine sediments from the Jurassic period. It appears the carnivorous sponges that it took us until 1995 to learn about have been living in the oceans for at least 150 million years.

The rest of the this years top ten – including bombardier worms, amphibious sea slugs and giant web building spiders – can be found here.

Vacelet, J., Boury-Esnault, N., Fiala-Medioni, A., & Fisher, C. (1995). A methanotrophic carnivorous sponge Nature, 377 (6547), 296-296 DOI: 10.1038/377296a0

Jean Vacelet,, Michelle Kelly, & Monika Schlacher-Hoenlinger (2009). Two new species of Chondrocladia (Demospongiae: Cladorhizidae) with a new spicule type from the deep south Pacific, and a discussion of the genus Meliiderma Zootaxa (2073), 57-68

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