Goniasterid Starfish LOVE to eat Octocorals!

Okeanos Explorer has begun Leg 4 into the Northern Hawaiian Islands and their last stream on Sunday was chock full of amazing vistas full of deep-sea (about 400-500 m) sea pens and corals! 

Probably one of the most exciting parts of these cruises is that I'm able to actually watch my favorite starfish species, some of which I described, in ACTION! Feeding on what turns out is their favorite food: octocorals!!

I've documented sea stars feeding on octocorals from the Atlantic Okeanos expeditions before (here).  and many of the species are the same.

Sea pens are big fleshy octocoral colonies that look sort of like an aquatic "quill" or pen. Here's one called Ptilosarcus, which occurs in shallow water from about SCUBA depth. 

Octocorals are specific type of cnidarian, which have eight arms on each polyp. They have a whole diversity of body forms and can be more colonial, such as this gorgonian or more like a big fleshy stick like the sea pens seen above..

The majority of the sea stars that we have observed feeding on octocorals are in the family Goniasteridae. As a generality, they look like this.

                                    

A big peripheral ring of plates frames their body. They can be anything from completely pentagonal to more star shaped. Many are covered by spines whereas others are not..

Among the best known of shallow-water goniasterid octocoral predators is the so called "spiny star" aka Hippasteria phrygiana (aka Hippasteria spinosa, etc.), which used to be known by MANY species before being recognized as one wide-spread species which occurs in three oceans! (here). 

This species occurs at SCUBA depth (and deeper) and many, involved studies have documented how these animals are important parts of ecosystems due to their predation on sea pens.

Thus, it makes a lot of sense that several of the deeper water species of Hippasteria, such as this Hippasteria imperials seen by the Okeanos Explorer should be a fairly active predator on deep-sea sea pens! 

Disks are swollen with water...

Here is just a gorgeous shot showing a seemingly endless vista of sea pens with these two large, Hippasteria imperialis roaming around like they own the place! 

BUT, Hippasteria imperialis isn't the only goniasterid starfish which feeds on octocorals. Many of its relatives, both close and far are also pretty active predators on deep-sea octocorals..

This big guy is Hippasteria muscipula! A species I just described last year! (here) It would seem to occur over a pretty wide depth range..from several hundreds to several THOUSANDS of meters!

They seem to be primarily predators on bamboo "corals" which are octocorals in the family Isididae.

and there was THIS stunning image showing H. muscipula but with 3 polynoid worms crawling around on its body surface. This is unusual, since polynoid worms usually crawl on the oral surface in the tube foot grooves..

Another closely related Hippasteria-like sea star which we've seen in the Hawaii region is the genus Evoplosoma.  

We've seen plenty of examples of Evoplosoma feeding in the Atlantic as well as parts of the Pacific. 

This shot is just awesome. We can see its stomach and tube feet hard at work clearing off the meat from the bamboo coral's stalk..

BUT that's not all! We've encountered multiple goniasterid species apparently feeding on coral! 

1. Astroceramus eldredgei

This was a new species I described recently and named in honor of Dr. Lu Eldredge formerly of the Bishop Museum. Observations by the Hawaiian Undersea Research Laboratory showed this very handsome animal munching on the blue plexaurid octocoral Astromuricea theophilasi.

Its a relatively shallow water animal (about 266-429 meters) compared to some of the other goniasterids here... None known below 500 m.

2. Calliaster pedicellaris

This species was described by Walter K. Fisher in 1906 and VERY rarely seen since then. 

3. Circeaster pullus

Here's another species I described back in 2006 and named in honor of Dr. Craig Young at the Oregon Institute of Marine Biology. It was observed perched on this coral skeleton where it was presumably feeding..

Have not seen any of these on the Okeanos dives as yet though.

4. Circeaster arandae? 

This one was a surprise because it very much looks like a species I described in 2006 from Madagascar!!  But it lives in deep, DEEP water (>1000 m) which is consistent with my earlier account. But weird to find it so far off..

How many more octocoral predators will we see??

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..

UPDATE! Ophiothela brittle stars Invade the Atlantic!

UPDATE: New pictures provided by Gustavo Beolchi show Ophiothela from Angra in Brazil..
on sponges..


on a gorgonain



BEFORE....
A recent alert went out from ophiuroid biologist at the Los Angeles County Museum- Dr. Gordon Hendler that a six-rayed brittle star from the Indo-Pacific has invaded the Atlantic! 

A pdf account of this from Coral Reefs can be downloaded here.

Invasive species are those which are artificially introduced into regions where they are not native. Their presence can directly or indirectly have significant to dire consequences on the ecology of a particular region.

Ophiothela is a clonal, six-armed brittle star that typically occurs in the Indo-Pacific as seen here (species shown is Ophiothela danae).  Photo by Wild Singapore.


Wild Singapore has a great page on these (note that not all of these seem to be Ophiothela however)
go here to see it!

But Ophiothela mirabilis seems to have invaded Brazil and St. Vincent as reported above. The species was first observed in Brazil of 2000 and has been observed slowly spreading throughout Brazil and the Caribbean.

This brittle star is asexual, specifically it is fissiparous and so it clones itself, thus facilitating its spread. Unlike other tiny commensal brittle stars, this one seems to have "low host specificity" which means that it can live on just about anything that it is compatible with (as seen below) from gorgonians to sponges..

Courtesy of the Brazillian website Cifonauta here is one of several videos of this invasive species in Brazil! They have several more pictures of this species also...

Can Crowd-Sourcing Help???
A quick look on Flickr indeed shows Ophiothela mirabilis as observed on Polymastia janeirensis (a sponge) from João Fernandes Beach - Buzios - RJ - Brazil (image from August 16, 2009). O. mirabilis is the tiny little orange thing clinging on below...

Photo by "Sea Girl".

Here's another pic from Brazil of what look to be Ophiothela (or maybe not hard to say without a close up) wrapped around what the photographer calls Leptogorgia punicea (a gorgonian)


The many eyes and cameras of the internet permit greater powers of tracking and observation of this species!  Got one from the Atlantic?  Post links to pics in the comments! Or contact me (or Dr. Hendler) for more info!