Tuesday, April 29, 2014

5 Echinoderm Highlights from the Okeanos Explorer Expedition to the Gulf of Mexico 2014


As a big marine/deep-sea biology nerd, I've been following the recent NOAA Gulf of Mexico Expedition undertaken by the Okeanos Explorer via the live stream on their website. For those who may not be familiar, the Research Vessel (R/V) Okeanos Explorer deploys an ROV (Remotely Operated Vehicle) aka a robot submarine which can deploy to 6000 meters.

The ROV has cameras that basically broadcast a High definition signal back to the ship, which then provides the stream to everyone via the Internet. You can see this here. The feed is usually narrated by two scientists who provide running commentary on the many biological and geological points of interest which they observe.

BUT they have a direct line to scientists on shore, who can instantaneously provide their expertise and/or knowledge without having to actually be on the ship. I am one of these experts and I've called in every so often to observe or point out some interesting and/or useful point.

Last year I was able to help provide some identifications and/or commentary for the 2013 Northeast Atlantic Canyons Expedition undertaken by the Okeanos Explorer. Go here to see a roundup

The current expedition was from April 10 to May 1st and its last cruise will be this week.

I've been watching their live feed as best as I can between various projects and day-to-day work. Many screengrabs and so forth have been made by several folks on Twitter, including myself (@echinoblog), Dr. Chris Kellogg(@DrChrisKellogg), the Voss Laboratory (@VossLaboratory), Steve Auscavitch (@steveauscavitch), NOAA Ocean Explorer (@oceanexplorer) and of course, the Okeanos Explorer itself (@okeanosexplorer)...

BUT, the video feed can be long and filled with mostly uneventful transit and/or deep-sea bottoms until something interesting pops up!   And even under the best of circumstances, important observations are missed and/or the ROV has to move on.....

So today, I've taken the liberty of rounding up 5 echinoderm-related observations condensed from the last 2 weeks of expedition video stream which I thougtht were interesting!!  (sorry if you were more drawn to fishes, sedimentary structures or coral....)

These are presented here with my own personal comments on each!   Enjoy!

5. Swimming Sea Cucumber Pooping!
Swimming Sea Cucumbers! MANY were seen in the first couple of weeks of the expedition on the abyssal bottoms! (>2000 m depths).  They in fact, saw many different species. I've written about swimming sea cucumbers here... 

But perhaps one of the most photogenic and frequently seen is Enypniastes. These live a combined bottom and swimming life.  They live primarily on the bottoms, extending their mouth tentacles to the bottoms looking for fresh, organic (but nutritious!) goo which has fallen to the sea bottom...
When done, its off to the next! They take off in search of the next new spot with freshly fallen food!                                   

But what made this Okeanos observation so memorable?? Enypniastes was shot not only eating.. but DEFECATING!!!

You can see its intestine RIGHT THROUGH the transparent body! And that's the "cleaned" sediment pooping out of the end!
Shallow water sea cucumbers act in an ecological role similar to earthworms. They digest organic materials, leaving inorganic sediment which aids in aerating soil for other organisms. (see here for this).

Its likely that the processing of organics through these sea cucumbers is important for organic and carbon cycling on the deep-sea floor...but here are FIVE good reasons why sea cucumber poop is so important!  (not all reasons may apply to deep-sea species but these give you a good idea why seeing this happening is important).


4. Goniasterid starfish (Peltaster?) feeding on glass sponges
All throughout my PhD, I worked on goniasterid starfish. This is a family of sea stars with over 256 species! One of the most diverse among the Asteroidea. But there was maybe less than a dozen species that we knew anything about their biology or had even EVER seen alive.

What do they eat? What color are they alive? Most goniasterids live in deep-sea habitats and so, very few of them had ever been observed doing well... anything, really.

So, every new observation, even anecdotally is potentially important and definitely interesting!

So, here we have a "cookie" shaped goniasterid, possibly Peltaster or something related (positive ID unclear from the pics)... but hunched over some glass sponges upon which it is most likely feeding.
                                       
A closer look.... I can only wonder what it gets out eating a glass sponge which really doesn't have much in the way of tissue to digest...

3.  Watching Dytaster insignis (Astropectinidae) & Nymphaster arentatus (Goniasteridae) ALIVE!
When we talk about deep-sea starfishes, ESPECIALLY the ones that live below 2000 meters, we really don't know a lot about their biology.  At one time, seeing ANY deep-sea starfish alive was biased by having to keep it in a cold-water aquarium AND by having to bring it up to the surface. RARELY have these species been seen alive, much less in situ (i.e. in their natural setting)

But even basic questions were often unknown. What was its natural posture? What color was it when alive? What was it eating? What was it doing? How was it moving?

This species, Dytaster insignis has been known primarily from dead specimens, usually with a gut, gouged full of mud similar to this porcellanasterid...
Here, Dytaster insignis is alive and observed in the "wild" doing what it does naturally...This is probably one of the first times its been observed with such clarity..
What's MOST interesting about the next two shots is the disk? See how its swollen like that? Like its just about to pop??  You just don't get to see that in a preserved specimen.  
Filled with mud? Sure. But probably also with water. Is the swelling just mud?  Is there perhaps more going on as there are with deep-sea sea cucumber guts??? (here)

Another great starfish we got to see alive and in situ (i.e. in its natural setting) is a goniasterid starfish species called Nymphaster arenatus.
 See those long arms? Always wondered what they were doing with em'  Looks like they help to distribute the weight on the muddy bottoms??  Curious.

2.  Mysterious 6-rayed starfish. Ampheraster alaminos or ???
Perhaps the BEST of the various stories that come out of watching these videos is wondering which ones are possibly NEW species.

So, take this for example. Seen on this expedition in the Gulf of Mexico but ALSO on the North Atlantic cruise last year.
This 6-rayed star is a deep-sea species, from the Gulf of Mexico and superficially kind of looks like this rarely seen starfish Ampheraster alaminos. Described only in 1971 (ha! I was only a year old!). You can download this paper here.
There is a WORLD of difference between seeing an animal living and seeing a 43 year old dead, dry specimen. 

What's curious is that I've seen similar looking species (the reddish 6-rayed one) in the Pacific as well. Is this the SAME? Or just a similar appearance that superficially looks similar??   Unfortunately, the Okeanos does not yet collect specimens for examination. Could it be new??    So, we shall see some day....


1.  What are Sea Urchins doing on Seep Mounds?
Perhaps one of the most intriguing series of observations on this expedition came from a group that I don't personally work on: the sea urchins aka the echinoids.

So, early on in the dives the ROV spied these huge chemosynthetic communities, including MANY mussels as well as bacterial mats and other associated faunas...including these sea urchins (genus Echinus perhaps? )

What's weird about this? Well, most echinoderms are pretty dang sensitive to water quality, especially when the water's filled with hydrocarbons or other unpleasant materials in it. So that's one thing.  But okay... let's say they are tolerant, what's ANOTHER weird thing?....
What are they EATING??
    When you take your basic Invertebrate Zoology course, you get told that "regular" urchins (i.e., those which are ball shaped like this one vs. sand dollars, and etc.)  mainly eat plant matter, kelp, etc.  Now, I've discussed in past posts how diverse the feeding modes of sea urchins can be...ranging from herbivores to filter feeders or even carnivores!  

But we don't see any of the usual food. So WHAT are they there for?  Bacterial food? Perhaps something growing on the chemosynthetic mussels??
The urchins certainly look happy enough. So, one wonders what it is that makes their survivorship in this region possible??  When we wouldn't necessarily expect them to do well?? 
Interesting. 


1a. BONUS Sea Urchins Feeding on Corals!
First.. a big THANK YOU to Steve Auscavitch and the Voss Laboratory for capturing this image while I was off doing other things...

But yes. Sea urchins feeding on corals. We saw lots of this in the North Atlantic Okeanos expedition last year.  It was new then and remains new here....

Extra Non-Echinoderm Observation: PALEODICTYON
These were traces observed on the deep-sea bottom. Its unclear exactly which organism creates them but similar traces have been see since the Paleozoic.

One famous oceanographer, Dr. Peter Rhona made it a life obsession to find out what they were... (see this piece in the NYT).

and another account of these as "crop circles in the deep sea" at Hindered Settling. According to various sources on Twitter, Paleodictyon was also a favorite topic of the famous paleontologist Adolf Seilacher, who passed away recently..
But what are they?? I don't know but by putting it out there again maybe someone out there will be intrigued and find out some day.  Drop me a note when you find out!





P.S.  Just to clarify, these bottom living brittle stars? Probably Ophiomusium. These don't live in corals unlike euryalid ophiuroids, which have the thick, branching fleshy arms arms and mostly live in the branches of various corals..


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...



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!