Tuesday, April 22, 2014

Learning about Luidia! 5 Things about The OTHER Sand Star!

Luidia clathrata from the Wikipedia page! thank you!
Probably one of the most frequently encountered but unappreciated of starfish is Luidia, a genus of seastar that occurs in tropics all throughout the world. Often times, in shallow-water and seen by MANY but known by few.

Some species, such as this Luidia alternata from the Southeast United States were recently mistaken for brittle stars by some, no-doubt, well intentioned but misinformed journalists! (here) Just to clarify: these are NOT brittle stars. Go here to see some characters you can use to tell them apart.  
I'm talkin' about sea stars in the genus Luidia, which is the only genus in the family Luidiidae. There are 49 species which are found all over the world, mostly in shallow tropical to temperate waters. Some get deep, but not very.. None occur at high latitudes (i.e., Arctic or Antarctic).

This group of starfish is named for the Welsh naturalist Edward Lhuyd who went by the latin name Luidius!

Luidia was an important animal in the big "Which starfish is primitive" arguments in the early 20th Century, and there was one time when this animal was part of a big argument that raged in the pages of the journal Nature...

Let's learn about Luidia!

1. Where Do They Live?
Sea stars in the genus Luidia typically inhabit shallow-water, tropical to temperate water places among sand or mud.  Basically, wherever loose sediment is found. In this respect, they are similar to the better known "sand stars" in the genus Astropecten. (Also a reason why common names don't have much use for scientists).

They use their spines and feet to bury themselves into the sand, or mud or whatever sediment they live in/on....




Here's a big Luidia maculata buried in the sand. Disturbed and then turned over..


I would note that the reason you often see these washed up after storms is because so many of these stars live on sandy bottoms. When you have any kind of turbulence they get "blown" up and washed onshore.

2. What Do They Look Like? 
Luidia can be pretty plain looking. But body form in these is pretty distinctive.

Arms are long and straplike (Luidia clathrata from the SE Atlantic shown here).                                  
And kinda flat... (Luidia clathrata shown here)
A close up look shows a lot of square-shaped plates known as "paxillae" with many tiny spinelets...

These vary in size on the center of the disk relative to those on the sides.. Spines are present on the lateral edges of the animal....


Some have elaborate patterns.... (L. maculata from Singapore)

Some with sharp spines!
Even the pointed tube feet have stripes sometimes...!


3. Diversity: How many kinds are there?
As mentioned earlier, there's some 49 species of Luidia known. They occur in the Atlantic, Pacific and Indian Oceans in temperate to tropical waters. A few live in deeper water.

Some, such as this Luidia clathrata from the SE Atlantic coast of North America are 5-rayed and kind of plain looking. Albeit with some coloration..These are pretty medium sized (see pic above) but the disk is maybe about the size of a quarter or a half dollar...
                            
Others, such as this Luidia superba from the Galapagos are HUGE. This species is one of the largest known (see here).  This species gets to be easily 2 feet across....
Others, such as this Luidia latiradiata have kind of a throwing star shape...
Several Luidia species have MORE than 5 arms, often 12-15.  You can see from some of the other videos and pics..these get pretty big also!!


4. What Do They Eat? and How?
Luidia (and the family Luidiidae) are members of the Paxillosida, which is to say the "Mud stars." Almost all of these swallow either prey in sediment or sediment in order to find food.

Luidia is predator and feeds on a variety of prey which live in mud, sand or other sediment. Prey items vary but they include sea urchins, snails, clams, brittle stars, other starfish (see below), sea cucumbers and even tiny crustaceans...

But, as with other members of this group, they lack an eversible stomach (such as what you would see in say, common intertidal starfish). So, they actually just SWALLOW what they eat WHOLE.

You can get an idea of how this works by watching this..

Or this...
From the SERC Invertebrate Gallery
Here's the Galapagos Luidia superba which was caught with a sand dollar in its gut. These usually just spit these out after they're done...


So, yeah. You get the idea. 

5. Ecology! What does Luidia interact with? 
If its one thing I've observed a lot of since starting this blog is how many sea stars are actually HABITATS for other animals. aka 'commensals' wherein the host is unaffected by the presence of the critter taking advantage.

I've written about how closely some polychaete worms have relationships with sea stars before. (here).

A 2002 paper by H. Kohtsuka at Notojima Aquarium and my colleague Toshihiko Fujita at the National Science Museum of Tokyo (Reports of the Noto Marine Center 8: 17-27) shows that several polychate worms live in association with at least two different species of Luidia, including Luidia quinaria and the large, multi-armed L. maculata in the Sea of Japan.

See below Fig. 1 from their paper showing worms in various living positions...

And from awhile back, was this fascinating video by Blennywatcher of this crab running along in association with this L. maculata.  Undoubtedly there are more associations but these two are good examples....


Other BONUS FACTS about Luidia??
A big multi-armed Luidia on its tippy toes?  is REALLY WEIRD... For more info on this GO HERE.
From Catala's Treasures of the Tropic Seas
More cool movement videos! 



Tuesday, April 15, 2014

Watching Brittle Stars Bioturbate! Amazing brittle star burrowing videos!


Today, a cool assortment of unusual videos of brittle stars digging themselves into the sediment!

hmm.. yes, I know that doesn't sound all that special but brittle stars are some of the most abundant animals on the planet. In some settings, such as the deep-sea they are thought to comprise an incredible amount of biomass.  As I've written about before, the Amphiuridae, which often make their home in sediment and hiding in mud are among the most diverse groups of brittle stars.

For the topic at hand, some of these videos are pretty amazing. Enjoy!

We start with an Antarctic species, Ophionotus victoriae doing its thing in a special aquarium and its thing is AWESOME.


A gorgeous video of Amphiodia occidentalis from Bodega Head in the North Pacific! 


Here is a typical burrowing type of brittle star from the family Amphiuridae, in the genus Amphiura shot here moving through some loose sediment. 


If you want an idea of how important the movement of these individual brittle stars is ultimately importatnt, scientists have made videos of their communities in the sediment. They "turn over" and process the sand/mud pretty readily. 


Being buried all the time also helps in preservation of brittle stars as fossils...


and we close out with one of the most gorgeous brittle star videos ever shot "Emerging" by Robert Suntay featuring what looks to be Ophiopsila sp.  as it emerges from its burrow..
EMERGING from Robert Suntay on Vimeo.


Tuesday, April 8, 2014

What are the DEEPEST known echinoderms??

                     
The depth of the ocean has been in the news a lot lately. Here's Virgin Oceanic planning to send someone down to the bottom,  as well as this excellent infographic from the Washington Post about how deep a challenge MH370's recovery might be..  

and of course 2012 was James Cameron's big dive in the Marianas Trench!
Image from NPR
The other day this came up in conversation "Blah, blah... but its not like echinoderms occur in the deep sea? I mean, I've only seen them inshore, they are mostly shallow water aren't they??"  Au contraire mon frere!!
Echinoderms are DEEP. They live in the deepest depths of the ocean..

But how deep are we talking?? Most folks think of "deep" as anything beyond the intertidal.

Many biologists think of "deep-sea" as anything below 200 m, which is where roughly where light stops penetrating. But then you get beyond THAT... then you start entering the REAL deep sea... the ones where biologists start saying stuff like "THAR be where dragons have lease..."
Via Wikipedia! 
To me, this starts at around 1000 m..and these zones include
  1. the Bathyal at roughly 700 to 1000 m
  2. the Abyssal at about 2000 to 4000 m
  3. the HADAL from 6000 to 10000 m
Basically, the true BOTTOM of the ocean is around 6000 to 10,000 meters. ABSOLUTE FARKING cold, dark, BOTTOM of the ocean.! And yes. Cameron's sub got down to 10,000 ish meters at the bottom of the Marianas Trench.  These are places where it is cold and dark. The coldest and the darkest in that there ocean!

Here is a chart from CNN (from the Cameron dive) which gives you a sense of scale about what these zones mean..
Image from CNN here
Echinoderms are among the DEEPEST living of all animals known on the planet. HOW DEEP? Which ones?? Let's find out!

Sources for this survey include Belyaev's "Hadal Bottom Fauna of the World Ocean", the former Online Echinoderm Newsletter World Records page and the Smithsonian NMNH specimen database!

1. Sea Urchins (Echinoidea) I start with one of the most familiar but also unfamiliar of sea urchin groups! There are many deep-sea urchins. Such as the echinothurioids (the tam o shanter urchins). or the bizarre Dermechinus.  Many of these urchins go deep, but still remain one of the "shallowest" of the Echinodermata. Many urchins occur at depths >1000 m but "only" go down to about 7000 meters.  Which urchins live at that 7000 meter threshold??

Pourtalesiidae: The "coke bottle" urchins! I have written about these bizarre deep-sea sea urchins before.  YES, these are sea urchins, albeit highly strange ones.

They have EXTREMELY thin and delicate skeletons, which can be almost paper thin. They live by burrowin through and digesting mud on the deep-sea bottoms. Records for the genus Pourtalesia sp. (usually only fragments are recovered) have been collected from 6,850 meters in the Java Trench.

2. Sea Stars (Asteroidea) Next up is my favorite group! They go deep but are not among the deepest. They go 2000-8000 m. That's not to say that there aren't a bunch of DEEP weird looking critters to look at! Here are the records!

Freyellid brisingidan starfish:  Freyastera sp. and Freyella sp. Brisingids are starfish that use their arms to pick food out of the water (more here). All the members of the Freyellidae occur in the VERY deepest depths. Typically below 1000m, but many occur between 4000-6000 m. But the deepest record for a freyellid was Freyella kurilokamchatica from 6860 meters.
                                      
"Mud Stars" Family Porcellanasteridae. NOW we're talkin. This entire family lives on muddy bottoms deep on the ocean floor, where they swallow massive amounts of mud for food. Similar to the mud star Ctenodiscus (here).  The specimen figured below from the NMNH collections is from 6, 250 METERS below the ocean surface!  Deepest record for this species, Eremicaster vicinus is from 7,614 meters! These live in the deepest abyssal-hadal bottoms around 4000 to 8000 meters.
Finally, Hymenaster, aka deep-sea slime stars. Here's a post about their shallower relatives. And you can always find more on my blog about them. Pic below is from 2000 m.

The deepest record for Hymenaster is for a species from 8,400 meters in the Kurile-Kamchatka trench!  So, Hymenaster (species remains undetermined) currently holds the record for deepest starfish. But who knows what new specimens and video remain to be discovered!

2.  Brittle Stars (Ophiuroidea)As with sea stars, their close relatives, the brittle stars don't seem to be quite as deep as some of the others but are still plenty deep. Plus, there's probably a bias of sampling as many brittle stars are tiny and more difficult to collect via nets and so forth..

The plate below is from this paper by Belyaev, G.M. & N.M. Litvinova, 1972: New genera and species of deep-sea Ophiuroidea. - Byull.mosk.Obshch.1spyt. rir. 77, 3: 5-20. (In Russian)
From Belyev & Litvinova 1972
The plate above conveniently displays three of the deepest occurring brittle star records known.
  1. In the upper two boxes is Perlophiura profundissima, which has been collected between 2265 and 8015 meters.
  2. Lower, left box is Homalophiura madseni, collected from 6156 to 7,230 meters! 
  3. and finally in the lower right hand box is Bathylepta pacifica which occurs between 5740 and 8006 meters! (thanks to Sabine Stohr for tipping me off to the correct species!)
There's easily a dozen species of brittle stars found below 6000 meters! Probably more...
4. Crinoids (Crinoidea) Down to the deepest TWO groups! 
Bathycrinus carpenteri from the SERPENT website
Among the crinoids, stalked crinoids are famous members of the deep-sea fauna. There are fossils of stalked crinoids which date back to the Paleozoic and there's always been sort of an unusual mystique to them.  Members of the family Bathycrinidae are recorded from 8,175 to 9,050 meters in the Kurile Kamchatka Trench! 


5. Sea Cucumbers (Holothuroidea)  So, which group takes the deep-sea CAKE for being deepest?? How could it be any other group than the Sea Cucumbers??? 

There's a LOT of diversity of sea cucumbers at the >5000 meter depth range. All of the swimming sea cucumbers live at these depths (click here

And of course, our old friends, the SEA PIGS!! (the one shown from 1500 m). Many members of the Elpidiidae, the group to which the sea pigs belong are among the deepest known. Several species occur as deep as 9,500 meters! 


But the winning sea cuke? the DEEPEST ones? Members of the Myriotrochidae, including Myriotrochus.  Records for these sea cucumbers go down to 10,687 meters!!! The NMNH has records of Myriotrochus bruuni from the Philippine Trench at depths of 10150 to 10190 meters! So yeah, if Cameron didn't see any of these when he was down there? That's HIS problem! 

This pic is from a Myriotrochus from the Kara Sea, but you get the idea.
this image from this Russian page 
This Russian Livejournal page actually has a nice photogallery of various cold-water deep-sea sea cucumber groups. Myriotrochids, molpadiids and sea pigs! Check it out..

There's a lot of weird stuff going on and through deep-sea sea cucumbers! Here's some of it.

So, yeah. Sea Cucumbers. Deep. And don't you forget it! 

Wednesday, March 26, 2014

Echinoblog Travelog: Japan: the things I will miss.... Pt. 5 (final)

Just got back from Japan and the 15 hour flight just wiped me out... so today is pictures!
                                        
 See-through starfish! (Anseropoda petaloides)
 Densenman! 
Matching Socks!
Sweets! but not chocolate or the usual western types...
Nakano Broadway...
 and some of its unique and interesting goods... (cleared and stained fish skeletons for sale)
KAIJU! Ultrakaiju Gomora! (and other Japanese science fiction)
Starfish Kaiju (weird deep-sea starfish!, this one, Hymenaster is about a foot across)
FOOD! Ramen and gyoza!  (mm... tempura not pictured)
And special mention to KABOBS! After a long day of running around Tokyo? These are surprisingly satisfying....



and of course, big expensive toy robots! (shown here is Big Dai X)

Until next time Tokyo! 

P.S. These are surprisingly accurate....
 

Tuesday, March 18, 2014

Echinoblog Travelog! Pt. 4 Stories from Tsukuba & Japan!

Travel is about experiences. Here are some of mine.... Starfish and not....

1. Starfish Story! 
Found this cool disk from the starfish Plazaster borealis the other day.  I am somewhat obsessed with this starfish (see this blog). It goes by the common name "tako hitode" aka the "octopus starfish" and we know next to nothing about it.  Sadly, this specimen was found without arms. Probably something that happened when it was collected....

Cool thing about this and the specimen lot it was found in?? Collected in 1932.  This species of starfish was originally described in 1938. That means, this specimen was actually collected SIX years before the species was actually described by Dr. Tohru Uchida.
 Here's what the animal looks like in its natural state. Almost 40 arms! But they disarticulate pretty easily.

2. Starfish-Worm Story!
The other day, I encountered this: polynoid polychaete worms which live commensally on the starfish Solaster borealis! STILL attached and living to their "host".

                                        
To give you some perspective, here is what the animal looks like in situ (from the North American side of the Pacific). 
This image from the Monterey Bay Aquarium Research Institute! 
And here is a close up of the worms living inside the mouth and tube foot grooves of the starfish...
With this Japanese Solaster borealis, we are seeing the relationship among some relatively deep-sea species but this type of relationship is also seen on several North American species of Solaster, such as this one from a shallow-water Washington species.

Where better to live/feed than on the "top dog" starfish predator like Solaster?  (or any starfish for that matter!)

3. Tunicate Food Story!
Travelling to foreign lands and new places means trying new foods and dishes that you don't normally get to try when you are at home. Sometimes, these dishes can be quite exotic.

Case in point: after a presentation at the University of Tokyo, I was treated to some hospitality including the opportunity to try hoya aka raw sea squirt or tunicate! 
I wrote a post about exotic invertebrates eaten around the world here. Here is a picture of what hoya looks like alive.
What does it taste like? Hm. An acquired taste certainly. Kind of sour and medicine-like is probably the most polite way to put it... Not one of my favorites but glad that I tried it!

4. Bathroom Story!
This one is a simple lesson in keeping track of different kinds of plumbing! Behold my bathrooom set up!

The shower is nozzle connected to the sink faucet. Very efficient. There's a shunt switch that routes water either to the faucet OR to the shower head. The shower head is used in the bathtub, where it can drain. But it is stored on the wall up there over the sink.

Sometimes you forget that the shunt switch is turned to "shower" instead of "sink" AND you have replaced the shower head on the wall.

Looking to brush your teeth and BOOM!  That was messy. 

5. EARTH Story! 
So I'm workin' one night, when "I-san" a worker in the lab, who speaks only a little english, gets up and starts saying "oscillate" ????  Odd.  

So, I get up and he's pointing to the mini-fridge shaped air vent sitting above my seat (above). Big, but held up by big metal struts. It is ROCKING back and forth. The rest of the lab, the floor seems perfectly stationary.  "Ground is shaking because of Earth moving" He says. My eyes open wide, as I grasp what he is saying and realize, "Oh crap, we're having an earthquake!"  

It was a 5.1... and I very nearly ignored it. Yow. 
Info for the quake can be found here. 

There's a HUGE Diversity  of starfishes in Japan...
Whew! I'm winding down the trip to Tsukuba/Tokyo and the National Museum of Nature and Science!  I'm finding a HUGE diversity of sea stars in the collections. When I arrived, there was an estimated 200 species in Japan. When I leave, this number will be significantly higher!  Many of them will be from deep-sea habitats.

Hopefully, this trip will only be Part One!