Tuesday, July 15, 2014

Sea Cucumber Skin Up Close! Bizarre & Beautiful!

Thelenota ananas Via Wikipedia commons. Photo by Nick Hobgood
Cool Crowdsourced Photo time! This week..some gorgeous closeups of the neat skin textures on tropical sea cucumbers!

Some of these give you an idea of how colorful and unusual the skin in sea cucumbers can be. This one is called  Thelenota rubolineata (the species name literally means "red lines"). This is an example of what the whole animal of one of the pics below looks like...

What do they feel like? Sort of soft and rubbery. Firm. And yes, people eat these species...

Here's a nice roundup of similar closeup photo essays of other echinoderms 
  1. Here's the one for Up close Starfish! 
  2. Another one showing close ups on Crinoids (aka Feather stars)
  3. COLORS! in brittle stars! 
  4. Crabs that live in sea cucumber anuses! here.
  5. Worms & Snails that live on sea cucumbers! here
Below.. you will find many different close ups of the skin of sea cucumbers.






this one is Thelenota I think...





Some striking full body pics...



Wednesday, July 9, 2014

The Colorful Challenge of Identifying Fromia monilis, an Indo-Pacific species complex!

From Wikipedia! 
Identifying animals is tricky business.

The other day, I was helping some folks out with an identification of a starfish they had photographed diving, but I stopped short of giving them the full species. "Why?" they asked. "Isn't this just the the XXX?" (they quoted the most common and easily identified species).

"Well.  Its complicated."

Hard to explain these things in a a few lines on Facebook or on Twitter so I thought I would take an example of how complicated the whole taxonomy and identification process is, using a widely photographed example, a starfish called Fromia monilis.

F. monilis occurs widely throughout the Indo-Pacific. It goes by many common names, Necklace star, Tiled star, Candycane star, Peppermint star, etc.  Scientists don't use those names because they're so inconsistently used and often because its a contrived name in a field guide, created as a convenience for readers.

This species is often seen in the wild and is a common species in the aquarium trade. You can see it in shallow-reefs from Okinawa to New Caledonia, in the Philippines, Indonesia, etc. and over to the edge of the Indian Ocean.

Bottom line: This species is distributed over a VAST area. Because it does, the range of variation (discussed below) is likely to be greater.

F. monilis is a bright red and white species with a distinctive color pattern. The plates on its body surface (i.e., the many circles and shapes you see on the body) are also pretty diagnostic. Most of these starfish are about 2-3 inches (about 5-6 cm) in diameter. So far so good.

Here is what I would say is the most commonly encountered and "typical" form of this species.
From Wikipedia. Here
But bear in mind, that often times, as biologists (such as myself) who specialize in describing and identifying these species, what we often end up working with is a specimen like this...
The dry specimen isn't as impressive as the real, living color one of course, but specimens like this are extremely useful for understanding the species definitions, evolution and ultimately, the taxonomy of these animals.

Some of these specimens have been in museums for, literally hundreds of years and remain essential to our understanding of how these species are defined.

Many of these species get distinguished by fine character differences on these specimens. Some might vary by plate pattern arrangements, or by the number of spines present on the underside, or the particular shape of granules present on the surface.  Its often difficult to synch up these characteristics (i.e. the species definitions) with qualities of the animal when it was alive.

BUT, because of dry specimens above, we can usually look at a specimen like this crazy thing below and tell that it is STILL Fromia monilis.
                 
Why?

Specimens in museums, accumulate over time and can be very abundant, giving us an idea of the natural VARIATION of a species. Size. Body forms. Aberrant shapes. etc.

So, you know how, some people have blond vs. brown hair? Or how some people can roll their tongue or perhaps more exceptionally,some folks have an extra toe or finger? Well, this kind of variation is present in all species and can make understanding classification and understanding evolutionary relationships...interesting.

For a species that we have virtually no understanding of, any character variation (without seeing its presence in the population) might be used to distinguish a separate species. Without an understanding of this kind of variation (or having population genetics data of course), someone who has never seen a human being before could separate me from Morgan Freeman as a different species. 

In the case of the above specimen of Fromia monilis, having seen MANY other specimens of this species, and understanding (we think?) the variation at play,  we know that most known individuals have 5 arms that don't bifurcate. The bifurcation is perhaps due to an attack or some damage during the animal's life time. The extra rays are just an unusual trait, perhaps equivalent to a person with an extra finger. 

Color in the individual above is also consistent. Red disk with red armtips. White in between. Okay. What could be more unusual than the 7 rayed crazy thing above??

Enter the 21st Century (and late 20th Century) and the era of Flickr and digital cameras ALL OVER THE WORLD!
So remember how the "typical" Fromia monilis had that particular color pattern??

What happens when you don't have the red color on the armtips?? Could this be a juvenile? (no size indicator on this pic unfortunately)?  This specimen is from Indonesia. Could these vary by region?
The one above (w/the red disk) is from Borneo.

Is this the same species? But simply with a different color pattern?? Or a different species??  Some species of starfish are thought to vary by color based on their food, does this one as well??  How important is the color as a feature in identification?

The same questions here. Color patterns vary even more drastically. No red on the disk, but there IS red on the armtips! The patterns are a little different?  Is this variation? Size? Or a new species? This one is from Lembeh Strait (Indonesia). 

This one from Papua New Guinea. Same color pattern as above. 
Here is a Fromia sp from Thailand. Color and plate patterns are different. Is this a new species?? Or the same species (F. monilis) showing the starfish equivalent to having lactose intolerance? Or blond hair?

Here is another closely related species, Fromia nodosa which occurs primarily in the Indian Ocean. This species is primarily distinguished based on the larger and more prominent round plates running down the radius of each arm. But it looks familiar, doesn't it??

This individual is from the Maldives (tropical Southern Indian Ocean). It shows the same pattern as F.monilis above and the distinguishing characteristic is kind of variable itself. In other words, it doesn't always hold up.  Does that mean it should just be consolidated into F. monilis??

Here's another indivdiual of Fromia nodosa, also from the Maldives. On both of these individuals, we also see the marginal plates as larger and uneven in one but NOT the other?? 
This one is from Thailand... Mayyybe?  its F. nodosa?? And what's going on with the dark armtips???
This strange thing is from the Philippines. It adheres to the definition of Fromia nodosa (big radial plates, etc.) but its a different color (or at least I assume this is not some photo artefact)!!
And then to make it even MORE confusing.. we have these things from the Red Sea and adjacent areas...

I initially thought this was Fromia monilis but in fact, they might actually be a separate, already established , but this species might actually be a species in a poorly known genus called Paraferdina. Further examination of specimens and research is needed to figure out which one is which... This specimen is from the Red Sea.

This one is from Egypt. The color pattern is familiar but the plate patterns on the arms?? Very different and yet, similar... F. nodosa? F. monilis? Paraferdina???


..and so on...

This is mainly to demonstrate the limits of how the colors and patterns get complicated quite quickly.

And yes, at some point, someone may work this out.. Lots of diving and subsequent DNA lab time. Plus looking over photos and museum visits! Woo!

But this also explains why scientists, such as myself,  are often more reluctant to give you a full species name for a picture when its sent for identification without a specimen. Are these one species? MANY species? Which ones correspond to pre-existing species?

Falling back on the one, most common name can often disguise the truly rich diversity in these wide-ranging, closely related species which are only now, just becoming understood. I argued that this was also the case with the "Bobbit worm" (Eunice aphroditois)

So, yes. Knowing more doesn't necessarily give you all the answers, but it does give you some pretty exciting questions! 

Tuesday, July 1, 2014

5 EPIC Deep-Sea Giant Isopod (Bathynomus) Observations from JAPAN!

From the Toba Aquarium's Twipple Account
Since my trip to Japan, I've been watching a LOT more social media from Japan. Their culture, for many reasons, has a deep appreciation of ocean life, especially of invertebrates. The weirder and the more unusual, the better. 

Japan is an ocean-nation and as such, via fishing, swimming, and etc. their country encounters one of the richest faunas of invertebrates anywhere in the world.  Japanese pop culture has recently seen a HUGE uptick focusing on interest in deep-sea animals, especially ones like the Giant Isopod: Bathynomus

This is in part, due to the various aquariums which have had this species on display, including the Toba Aquarium and the Numazu DeepSea Aquarium. 


Defining my Terms. What Species of Bathynomus
In the big world of the Internet, its easy to start dropping names. Not many taxonomists, and too little information. So, let me take a moment to talk about diversity in "giant isopods" aka Bathynomus.

Bathynomus is a genus of deep-sea isopod which occurs throughout the Atlantic, Indian and Pacific oceans, roughly between 200 to 2140 meter depths. Isopods are of course, crustaceans. You may be more familiar with their terrestrial counterparts which go by many common names: "potato bugs", "rollie pollies" or "wood louse". But they're all members of the same group of crustaceans, the Isopoda.

Its easy to get caught up with the excitement associated with the most famous of all the Bathynomus species, Bathynomus giganteus. It is among one of the largest of marine animals and has an easy name to remember. Its species name literally means "Gigantic" Bathynomus.
There are about 18 species of Bathynomus occurring all around the world. According to an account by Lowry & Dempsey in 2006, Deep Sea Benthos (here)  they divide he various species into "Giants" which only reach 150 mm (about 6 inches) and "Supergiants" which reach up to 500 mm (almost 2 feet long!).

Yes. They can get to be bigger than a CAT.

B. giganteus, which occurs only in the western Atlantic is a "Supergiant". About half of the known species are "supergiants". A great summary to B. giganteus was written by the famous (now retired) Kevin Zelnio here, from many years ago..

The Japanese species, Bathynomus doderleini gets to be a decent size. About the length of a hand or foot. But it is apparently collected with some abundance in Japan and as such, has been put on display in several aquaria, permitting many interesting things to be learned about its biology.

There was one account earlier this year of an individual (apparently B. giganteus brought from the Gulf of Mexico) at Toba Aquarium which famously refused food for FOUR YEARS before it finally died in 2013.
From the Toba Aquarium Twipple
Interesting Names of Giant Isopods in Japan
The Japanese have a surprisingly consistent naming system used in labelling animals. As far as I can tell, this system is used in addition to the standard Latin names used for various significant species around the world. I've discussed some of these for starfish here

The popular term for Giant Isopod in Japanese is the word for the armor worn by shogun! Gusoku!  You can sort of see the resemblance: the overlapping plates and the helmet, etc..
The  name for Bathynomus doederleini, is Oo gusoku mushi
オオグソクムシ(大具足虫)
"oo" basically means "big", "guosku" refers to the armor of the samurai. and "mushi" refers to "many legged insect", "bug", or "critter"
From the Numazu Twitter pics
There is actually a separate name for the Atlantic Bathynomus giganteus, Daioh-Gusoku-mushi which roughly translates to "Grand King Armored Critter" ("dai" means grand or BIG).
ダイオウグソクムシ(大王具足虫)

What's that? You want MORE??? here's a bunch of amazing observations, spied via social media and etc. about everyone's favorite deep-sea isopod! Some biological. Some cultural...

5. Bathynomus feeding.  
Here is a tank in Japan filled with what is presumably Bathynomus doderleini, Watch the fish put in at 0:15-0:20 then, followed by FEEDING FRENZY and subsequent flesh-free fish skeleton!! Forget piranha.. throw James Bond into a pool full of these sometime!


4. There is a surprising abundance of Japanese Bathynomus products
I gotta say. They KNOW a good thing when they got it!!  I'm an echinoderm fan, but I respect a culture that loves deep-sea crustaceans!

Oh man. I don't even know where to start.
                                     

3. People EAT Bathynomus??
Yes. The full story is over here at Rocket News 24.  From what I've seen, this tends to be only B. doederleini, and not the Atlantic B. giganteus.

I only add that Bathynomus is probably NOT a good animal to depend on as a sustainable food source. But according to my colleagues, yes they are edible and not surprisingly, they taste like crab. and are pretty crunchy. Mostly they seem to be deep-fried. But I've heard they also eat them as sushi.

Video report in Japanese is here. But you'll get the idea.

2. Bathynomus Molting
Its not a secret that crustaceans molt. Crabs, lobsters, shrimps. All of them shed their exoskeleton as the body grows. And yes.. isopods also molt. Its been observed in more conventional species.. But has it ever been observed in Bathynomus?? (I couldn't locate an account but maybe it is out there?)

But here is something from the Toba Aquarium's Twipple Account (Twipple is a photohost service).  An AWESOME sequence of a deep-sea Giant Isopod undergoing a MOLT!

How many times do you get to see THAT??

First photo was recorded at 9:21 AM (Japan Standard Time),
From Toba Aquarium Twipple
This took place at about 10:00 AM. You can see more of the latter part of the exoskeleton beginning to come off..                                  
From Toba Aquarium Twipple
Based on other pics in the sequence, it got that older bit off around 2pm (JST). This is the fully removed latter half (new skeleton is brown) by about 5pm.
From Toba Aquarium Twipple
1. Bathynomus Brooding Juveniles! I thought this was amazing. So, I am not a crustacean biologist, nor am I one who knows everything there is to know about deep-sea isopods, but I did a non-trivial search in the literature for an account of Bathynomus bearing live young and I couldn't locate anything.

The Atlantic species. B. giganteus broods eggs, and some terrestrial isopods brood, so brooding juveniles in this species is not a big surprise. Its not clear to me if the Atlantic "gigantic" species does this.

But, clearly, this Japanese species does this. Priceless and awesome.
From the Numazu Aquarium's Twitter Account
There is VIDEO OF THIS!!!!

Here's one of those baby isopods... Not sure of the exact size..but looks to be about 1.0 cm long based on some of the other pics.. Awww...,
From the Numazu Twitter pics
and finally, BONUS!  a common question I always get, can Bathynomus roll up into a ball like their smaller, terrestrial cousins? 
From the Toba Aquarium Twipple
yes. 

(with the disclaimer that these are species kept in aquaria, which may provoke unusual behavior not typically seen in wild populations)

Whew! How can Japan LOVE a crustacean so much??? 
From this website

Tuesday, June 24, 2014

5 NEAT things about the Caribbean/Tropical Atlantic Cushion Star Oreaster reticulatus

Image from STRI's O. reticulatus page
Today, I thought I would treat all of you with some info about one of the most strikingly colored of Atlantic echinoderms.. the so-called "Cushion Star" of the Caribbean aka Oreaster reticulatus.

The species name "reticulatus" refers to the net-like pattern on the body surface whereas "Oreas- refers to "mountain"... So breaking it down, the latin name means "Reticulated Mountain Star."

O. reticulatus is a pretty iconic animal for this region. It is so, distinguished that it even occurs on the 1 cent coin on the Common Wealth of the Bahamas!!                       
These have been made into CUFFLINKS!
                         
and postage stamps!

The genus Oreaster only in the tropical Atlantic, on both the east and west side and is known only to occur in shallow water.  Oreaster reticulatus tends to be thought of as being primarily a west Atlantic species.

The east Atlantic/African species of Oreaster is called Oreaster clavatus and varies in color and spination...
Image borrowed from this excellent French site for identifying marine fauna "Sous les Mers"
I would comment that although they are known from shallow water doesn't mean they are really a good intertidal species, so its preferred to leave them as-is where they live underwater. Propping them up on sandy beaches with their arms propped up like a tentpole in the sand is pretty much a death warrant for this or any starfish....

Moving on! Adults do vary somewhat in color (note also juveniles below)... Some lighter
                    
Some darker...
                    
Most times, these are 5 rayed, but occasionally you get the odd one with 4 or 6..
                    
But enough with the intro!!  Here we go!

5. Oreaster reticulatus are omnivorous feeders but eat a lot of algae and encrusting food. Often, they feed in feeding "fronts"
So, one of the seemingly constant assumptions (I would say misconceptions) that are often made of sea stars is that they ALL adhere to the feeding modes of shallow-water asteriids, such as Asterias.. i.e., the old trope of "all starfish feed on mussels or clams" I have written at length about the diversity of feeding modes in sea stars. You can see more of that here and here..

O. reticulatus feeds primarily on microalgae and/or on other kinds of encrusting food. Work by Scheibling (1980 in Marine Ecology Progress Series 2: 321-327) shows them feeding on a seagrass bed where they obtain nutrients from a likely combination of organisms on the seagrass, the seagrass, and organic materials in the sediment, etc.  but what's interesting? is HOW they do this...
                   
When Oreaster reticulatus feed, they do so in a FEEDING FRONT!! Kind of like an army across the sand bed...

The pic below hails from the paper cited. The authors describe this feeding front:
A feeding front of the sea star Oreaster reticulatus off St. Croix, U.S. Virgin Islands. The front is moving from left to right. Feeding mounds (fm) of darker sediment surrounded by lighter halos can be seen behind the front on the highly turbated sand bottom. In advance of the front, the sediment appears darker because of a microalgal film which has developed in the absence of sea star grazing in the previous weeks. Average sea star diameter is 0.26 m
This from Jean-Sébastien Lauzon-Guay, Robert E. Scheibling, and Myriam A. Barbeau. 2008. Formation and propagation of feeding fronts in benthic marine invertebrates: a modeling approach. Ecology 89:3150–3162.
So, you may see this just sitting there on the sea bottom by themselves. But "on their own" in the wild?? These guys form organized feeding groups. Think about it too, they feed on algae and possibly clear the sediment. Maybe their effect is similar to that of some sea cucumbers? 

Also worth noting?  Food varies with location. Some feed on algae, but others feed on sponges. In some places, up to 61% of the species were feeding on MANY different sponge species (see Wulff 1995 in Marine Biology 123: 313-325)

Even MORE interesting? Feeding by O. reticulatus is so specific that they can actually tell apart different species of sponges that humans cannot recognize!  (see Wulff 2006 in Biol. Bulletin 211: 83-94)


3. Juveniles are a different color/appearance than the adults.
Oreaster reticulatus are members of the family Oreasteridae.  As adults, these are big, massive very heavily armored individuals.   But when smaller, most have a VERY different looking juvenile form.

This, for example, is a photo of the many growth forms that the Indo-Pacific Cushion star, Culctia novaeguineae undergoes as it gets bigger.
The same is true for Oreaster reticulatus, which undergoes size AND color transformations as it increases in size.... This probably varies even MORE depending on where the animal lives, and what its food might be...


                     
This one is more brown...
                    

3. O. reticulatus "home in" on large aggregations of other O. reticulatus 
Image from Echino LifeDesks. Photo by Simon Coppard
One interesting paper by Bob Scheibling (1980-in Marine Behaviour & Physiology 7: 213-223) studied a population of O. reticulatus in the US Virgin Islands.

They performed an experiment, where a big bunch of individuals present on a large sand patch were moved off the patch to about 20 m (about 66 feet) into the surrounding seagrass bed.

As the internet is fond of saying "What happened next, WILL AMAZE YOU!" (or at least, I thought it was interesting...) the starfish then, re-oriented and then moved BACK to the patch, re-grouped with the others within 24 hours!  That is, they HOMED in on the OTHER starfish and MOVED there.

How? Probably through some kind of chemosensory cue in the water. i.e., something that those starfish leave behind that informs the others how to find them. So, yes, they can tell where they are and determine where others are as well.


2. O. reticulatus is closely related to another species in the East Pacific!
                  
One of the cool things about many of the animals which are found in the tropical Atlantic and Gulf of Mexico, is that you can often look toward the East Pacific (i.e. the other side of the Panamanian isthmus) and find ANOTHER species which often bears a close resemblance!

I wrote a story awhile back about a starfish species, Heliaster kubiniji, found as a living from in the East Pacific, but ALSO as an extinct, fossil form from Florida.

Long story short? About 10 million years ago the isthmus of Panama was not yet closed. And it was an open waterway between the "Gulf of Mexico" and the eastern Pacific (south of Baja California).

There were MANY species in this area were once connected. Some were one continuous species while others just kind of showed a close genetic connection. Then the isthmus formed about 3-5 million years ago and formed a barrier, separating these two populations.

Before we had better genetics and fossils to tell us about the precise timing, these were often assumed to be "sister" species. In other words, two sides of the same coin.. closely related by only a few million years of separation. But it is now clear to us that several of these diverged from one another much earlier than that. And are thus much more distantly related than was previously thought...


1. O. reticulatus faces "predation pressure" from tourists and studies on populations and reproductive biology do not suggest it will do well if overfished.
Yeah, sorry, this one is not quite as fun or neat as the others, but its important.  I've written about the pending threat of "overfishing" starfish species in the Indo-Pacific. This includes the widely occurring Protoreaster nodosus  as well as several other fished species (Archaster, etc.).. 

In the tropical Atlantic, O. reticulatus is regularly taken as fodder for tourist shops and so forth. The pressure on this industry has become significant and in many places the populations of this species have become locally extinct.

Based on work by Scheibling & Metaxas (see this and MANY other refs) the population of this species are relatively low, ranging from 1 to 5 individuals per 100 sq. meter and don't turn over very quickly. It is unclear how much growth goes into a large sized, adult individual, but it doesn't seem that these are very fast growers.

The species is dependent on the algae and other food found on seagrass beds, which suggests that between collection of the adults and habtiat destruction or disruption, this does not bode well for the big familiar "cushion stars" of the tropical Atlantic..
                    
So, here is a species that seemingly everyone takes for granted but if it has an ecologically important role, maybe one we haven't fully understood? and we're taking it for tourist baubles and souvenirs??

Something to think about...

....and one extra! .. I'll be honest and say I'm not sure if this is pooping...or spawning..
                   

Friday, June 20, 2014

The Things & Critters I will Miss at the Invertebrate House at the Zoo

As many of you may have noticed from the news or from my Twitter feed (@echinoblog), the National Zoo's Invertebrate House (here in Washington DC) will be closing its doors for good on Sunday, June 22nd.  So, if you're in DC on Saturday GO see it before its gone! 


A very passionate and concerted effort to save the Invertebrates Exhibit was started by Terri Jacobsen. As of this writing (Friday, June 20)  it has garnered the support over over 2,281 signatures!   While this may not change the outcome on Sunday, I hope that her good efforts will result in some influence and/or demonstration that invertebrates are worthy of a full presence in ANY "zoological park"...

I dropped by to give my regards to my friends (both vertebrate and invertebrate). Everyone I spoke to was disappointed and like myself, sad to see the exhibit go. 

But in the meantime, as we proceed to the weekend, I thought I would offer some of the things/critters that I will miss after the closure...

1. Stomatopod! 
 2. Ant Traffic Camera! 
ANT TRAFFIC! 

3. AWESOME Marine Invertebrate Art in History! 
Nautilus
Japanese Crustacean Art! 
 Bronze Shell!  
Minoan Stirrup Jug with octopus motif! 

4. BIG HERMIT CRAB!
 5. Giant Pacific Octopus! 
6. Ctenophores & other Jellies!
7. The AWESOME behind the Scenes where the zoo folk work! !!! 
8. That BIG spider that they let live out in the open without any glass! 
9. Watching them feed that AWESOME Cuttlefish!
                            
10. Those AWESOME colored cerianthid sea anemones!



 11. Sunflower Stars! (Pycnopodia helianthoides)
12. And of course, the AMAZING coral reef exhibit..

My BEST to everyone at the Invertebrate House! 
                                                    

Tuesday, June 17, 2014

The Cousin Itt of Sea Urchins! Irregular Urchins featuring Echinocardium cordatum!

SEA URCHINS!  Everybody knows the familiar spiny balls that live in the ocean. But fewer people realize the many unusual KINDS of sea urchins.  In the past, I have written about the most highly modified sea urchins aka the sand dollars! 

As I've discussed, urchins can be loosely divided in the "regular" urchins-round spiny balls and the "irregular" urchins- the ones with a right and left side with highly modified body, spines and jaw parts which are used for moving through sediment (mud, sand, etc.).


But it occurred to me that I had never outlined how a more typical "irregular urchin" lives.. So, I thought I would illustrate with one of the most widely occurring of irregular urchins a species called Echinocardium cordatum, described in 1777 by Pennant. A member of the family Loveniidae. 

These go by the common name "heart urchins" or as I've been observing lately, the "sea potato" (not what I would call them, but there ya' go...)

Interestingly, this species occurs widely around the world. They are present in the Atlantic but also in Australia, New Zealand, the East Pacific, and South Africa across a broad depth range (0-250 m). 

Interesting side note: based on some genetic work on various populations by some of my French colleagues (here) The global occurrence of this species may actually represent SEVERAL closely related species! 
                    
At first glance, some of these urchins are just covered in spines! and its difficult to determine what end is up! Kind of like Cousin Itt from the Addams Family! 
                                           
So, I thought I would compare with some specimens without the spines.... The genus name Echinocardium means "Spiny heart" and cordatum which also means "heart shaped", so the whole "heart shaped" thing seems to be a theme...

Here's the skeleton (called the test) of one without the spines. (individual alive with spines is the white one shown above) so, yeah, they have a heart shaped skeleton. This is the top surface..
                                                    
The skeletons on these urchins has evolved for living in sediment (i.e., sand, mud, etc.). This pic below shows the UNDERSIDE of the animal.. and that weird-shaped hole??  That's the mouth (called a peristome).
Note all of those knobs on the surface? Those are where the spines are connected to the surface of the skeleton. 

Basically, all these spines function to help shovel and move sediment INTO the mouth and serve to help the animal move through the sediment, etc. 
Here's a video of one that's been turned upside down. Its nice because it shows pretty closely all of the various spine types on the underside. Some are more spoon or spade shaped. And all of them are pretty agile..  Another nice shot of these spines is here. 
          
And of course, here is the anus (aka the periproct). Where the poop (sediment, etc.) comes out! 

How does this species live?? 
                     
According to various accounts by John Buchanan from 1966 and Dave Nichols (1959) [figure below from Nichols (1959)]  these bury themselves but run a respiratory tube foot up through the sediment.

The folks over at the British Museum have this GREAT pic of Echinocardium (below) cleared away from sediment but with the channel clearly present! Original source with a more detailed explanation is here

This video isn't terribly exciting but it DOES give you an idea of how Echinocardium starts to bury itself into the sediment. These vary around the world in terms of how they behave when burrowing.
            
One more cool thing?  Echinocardium has a decent fossil record!  AND one of the neat things that have been found are the filled in casts of the BURROWS  of Echinocardium (or something related) that these animals lived in.. (this one from the Pliocene near Tuscany, Italy)