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??

The Hippest Post you Know! New Hippasteria species!

Research! People often speak of the rigors, hardships and even agony of their research. The long days in the field to the writing and so forth.. But what a lot of folks don't often spotlight is how damn satisfying it is (at least for me) to see something you've been doing for several YEARS come to fruition in a paper! 

Case in point is my newest starfish monograph, just published a week ago in the prestigious Zoological Journal of the Linnean Society!  You can go here to find it (sorry-paywall).

This was part of a project that began years ago in 2011 or so, as I discovered several of the specimens described below in the collections at the Muséum National d'Histoire Naturelle during one of my visits to study their starfish from far and distant lands! 

This, then combined with a project I was working on with my colleague Dave Foltz at Louisiana State University and eventually snowballed, adding on Marc Eleaume, my colleague from Paris and Kate Neill from the New Zealand Institute of Water and Atmospheric Research (NIWA). 

What's it all about?? 

You may remember a post I wrote last year about some work I did with my colleagues where we discovered that the starfish species Hippasteria phrygiana was not simply one species in the Atlantic but in fact one species that was found across THREE OCEANS! (here to see the full story)

Part of this work involved not only Hippasteria phrygiana, but testing whether or not the OTHER species of Hippasteria were the same! And what about other potentially new species?? Were those new?? 

My colleagues, especially Dave Foltz analyzed tissues sampled from samples of multiple Hippasteria species taken from all around the world. From the Atlantic to the North Pacific to New Zealand (South Pacific) to Kerguelen Island in the southern Indian Ocean! 

We sampled for genes and compared them using analysis software to get this tree, which showed us which were the mostly strongly supported species..

We ended up with 7 species, 3 of them were new to science!  Of the other 4, H. phrygiana we kinda changed (see below) and here. Hippasteria californica had some weird dynamics (see below, Hippasteria heathi was a "good" species but we found out that it had cousins which were found WAY beyond where  it was found and the final species Hippasteria lepidonotus turned out to have been "oversplit" into the genus Cryptopeltaster. That is, it turns out to be a redundant name which was likely created because of the deceptive amount of differing morphology in that species (and thus thought to be more different than it actually was).  

So, let's see some new species!!  Many Hippasteria related species are predators of deep-sea coral predators and I've described other new starfish species related to these, which you can read about here.  

1. Hippasteria muscipula

This one is the biggest and neatest of the new species I described.. A big, massive critter about 30 cm (about a foot across)! 

It was collected from various tropical Pacific localities: Hawaiian Islands, New Zealand south of New Caledonia in deep-water. 425 to 1500 meters!

What's cool about it?? The name.  The species has these very big and toothy pedicellariae (aka claw like structures on the surface, possibly used for defense)

The species was Hippasteria muscipula after the pedicellariae's resemblance to the Venus fly trap (Dionaea muscipula)!

One other cool thing we found? The specimen from New Caledonia had its stomach wrapped around a deep-sea "coral" called Metallogorgia, which is kind of an odd looking gorgonian that looks like a living wire hanger! Possibly feeding on it??  Interesting. 

2. Hippasteria tiburoni
This new species was a little tiny thing collected by the Monterey Bay Aquarium Research Institute from Pioneer Seamount in the North Pacific (southwest of San Francisco) in 2005

This species was distantly related to Hippasteria heathi, which occurs primarily in the Aleutians..

This species was named for its "collector" the now defunct Remotely Operated Vehicle Tiburon which served science and MBARI well between 1996 and 2008!

Hippasteria tiburoni, despite its size was observed feeding on deep-sea bamboo coral!!  Ain't it an awesome little critter?? 

3. Hippasteria mcknighti
The third new species we described was found among specimens sent to us from the New Zealand Institute of Water and Atmospheric Research.  It resembles the North Pacific Hippasteria heathi but the genetic and morphological data support it as being distinct..

This species was named for Don McKnight (1936-2012), a famous echinoderm biologist who worked on echinoderms for NIWA for many years. His obituary is here. 

4. Big Taxonomic Changes! 

The rest of the paper addresses multiple taxonomic changes (i.e. names of species).  Among the most significant of these was the big discovery of how wide-ranging a species, Hippasteria phrygiana turned out to be!!   This was a species found in THREE OCEANS! 

The problem with this discovery was that historically, folks would often describe a new species if it was not previously known from that part of the world and sometimes there are widely occurring animals which do form regional subspecies. It depends.

                    

But in this case, thanks to our genetic data, we could tell that a great many described species, which were likely separated as distinct species based on minor differences are in fact, just minor variation of one wide-ranging species!

In this case nearly a dozen species, were found to be "redundant" or were applied to Hippasteria phrygiana throughout different parts of the world. 

We also looked at the other species of Hippasteria, H. californica which occurs in deeper water habitats than H. spinosa... 

Image by Dr. Steve Lonhart Via SIMON

What we had found, up this point had been pretty consistent with what had been known until we found two individuals of this species which were revealed by genetics to have been Hippasteria californica BUT in SHALLOW WATER habitats in British Columbia AND which looked like H. spinosa!

Weird.

Image by Neil McDaniel (check out his website here)

STRANGE! And a mystery that we shall have to investigate for another day....

OTHER Related Posts:
New genera and species of Hippasteria related starfish species! 

Deep-sea Corallivore Video from MBARI!

Deep-Sea Coral Starfish PREDATORS! New Genus! New Species! Deep-sea Corals shudder in FEAR!

So, today you guys get something a little special that I've been cooking up! After a few years of gathering specimens and working up data, I finally published this paper with Martha Nizinski of the National Marine Fisheries Service (NMFS) and Lonny Lundsten of the Monterey Bay Aquarium Research Institute (MBARI).

My paper describes THREE new species and one new genus in the subfamily Hippasterinae, which is a group within the family Goniasteridae. Goniasterids occur all over the world and and are probably the MOST diverse of all the starfish groups with some 64 genera and close to 260 species!

This one subfamily, the Hippasterinae, includes the familar Hippasteria (below) which live primarily in the deep-sea, but in some parts of the world, can be seen SCUBA diving depending on where you live (e.g., Washington, Oregon, British Columbia, etc.).
Hippasteria has been known to humanity for a LONG time. It was literally one of the first sea stars described by European scientists in 1840. But for the most part, its a deep-sea species and we didn't know much about it or its relatives up until recently.

So, it turns out that Hippasteria's got some pretty important eating habits. It and its relatives are voracious predators of cnidarians, specifically deep-sea CORAL. I've written about various sea star corallivores before (early on in the Echinoblog-here).

But as a quick reminder-Hippasteria (and its relatives) aren't the ONLY asteroids that feed on "corals" (which can be broadly defined as almost any cnidarian with a biogenic skeleton).
Shown above, is Acanthaster planci-the infamous Crown-of-Thorns starfish which attacks and devours primarily shallow-water tropical "hard" coral (i.e., scleractinian). While the above species has grown to plague proportions-it is an important member of the coral-reef ecosystem. As it is likely these deep-sea corallivores are ALSO likely to be... So, how did this whole process begin? As with many things...it started with me identifying a starfish...

Discovering New Deep-Sea Coral Eating Starfish!

My colleague, Dr. Martha Nizinski approached me several years ago with some pretty large-sized starfishes from the tropical Atlantic.

These were in the NMNH collections as part of the considerable "backlog" of unidentified material from her studies with the Johnson Sea Link. I had just arrived and was examining everything that I could...
It turns out that there were not one but TWO species among the specimens that Dr. Nizinski had collected!

One was a rare species called "Hippasteria" caribaea that turned out to be incorrectly classified and was more properly placed in a Pacific-only genus called Gilbertaster, making the full correct name Gilbertaster caribaea.

It turns out that Gilbertaster caribaea is rarely encountered. Only 6 specimens are known
Its a very neat looking animal with all of these very LARGE lip-shaped pedicellariae.

Pedicellariae are pincer or wrench-shaped structures that sea stars use to interact with the environment.

Perhaps they are used to fend off predators? or perhaps to keep their surfaces clear of settling debris? Its not clear what the function is in all taxa... but one thing IS clear? There's a LOT of pedicellariae on the body surface...(each lip-shaped pedicellariae is about 2-5 mm long each)
and there's a bunch of them on the oral surface around the mouth (again, each about 2-5 mm long each)
AND in addition to Gilbertaster caribaea above, there was ANOTHER SPECIES. One that had NOT been recognized by scientists before. Not only was it a new species...but a new GENUS.

The animal has a really stout, heavy body and so I called it Sthenaster from the Greek "sthenos" for strength and -aster for star. So, "Strong Star"
It too has the many, many large pedicellariae...
Finally, I named the species after my colleague Dr. Emma Bullock in the NMNH Mineral Science Department, with the name Sthenaster emmae !!

Dr. Bullock is shown here holding her namesake!
At about the same time, Lonny Lundsten, one of my colleagues from the West coast at the Monterey Bay Aquarium Research Institute had just returned from several cruises off the coast of California..
And he had discovered several NEW specimens of ANOTHER rarely encountered sea star in the genus Evoplosoma. At the time, Evoplosoma was known less than about a dozen specimens worldwide

Here's a pic of the Atlantic species to give you an idea of what they look like...
Lots of spines and pedicellariae...

Well, it turns out that Lonny had MORE than just the preserved specimens..he also had VIDEO and photos of these animals on the sea bottom (>2000 m depths!) doing stuff like this!
NO species of Evoplosoma was known from off the west coast of North America! After examining specimens, it turned out there were TWO distinct species of Evoplosoma present. Both were observed feeding on deep-sea corals.

I named one, Evoplosoma voratus. "Voratus" means to "greedily devour" and the second, Evoplosoma claguei I named for Dr. David Clague an MBARI Geologist who headed the mission and collected several of the specimens!
I proceeded to engage in a phylogenetic analysis of these and other related sea stars in the Hippasterinae/Goniasteridae, including Hippasteriaand the closely related Cryptopeltasterusing computer software to analyze the external characters to group similar taxa together...
To get a tree that looks like this!

The tree shows some interesting stuff... the genus Evoplsoma is found ONLY in the deep-sea and is probably a derived (i.e., highly specialized) member of the Hippasterinae. And so, its ancestors probably hail from a shallow-water ancestor.

I also realized that there were observations of coral predation from nearly EVERY member of the Hippasterinae. There was no evidence for Gilbertaster feeding on coral-but there was for all the rest.

As you can see here, the starfish is actually climbing UP the stalk and leaving the skeleton of the animal devoid of living flesh as it devours the animal like delicious deep-sea cnidarian lollipop!
I checked the gut contents of our new genus and species, Sthenaster emmae which had been collected in close proximity to deep-sea corals! Examining the food left in the stomach of these animals resulted in our discovering ...SCLERITES
Sclerites are skeletal bits from certain kinds of deep-sea corals. They are also distinctive enough for some species that they can be used to identify species!! Later examination of the collection video of these animals did in fact show that these WERE feeding on deep-sea corals!

I've also gotten to looking for these animals on the internet. Its actually seen on quite a few oceanographic expeditions in the Atlantic and the Pacific!
Here is an image from a 2004 Alaskan Seamount expedition. Probably Hippasteria...Here's another image of what is probably Evoplosoma from the same 2004 ExpeditionAnd from a 2003 HURL mission to Hawaii...Although I'm not sure which species this is..and I observed Evoplosoma on the 2009 Pacific Northwest Expedition!
And this 2004 account of what turns out to be a new species of Evoplosoma from Bear Seamount in the Atlantic!Potentially, we are seeing the discovery of a pretty widespread ecological interaction...and an important part of understanding deep-sea corals! A conservation priority in the deep-sea as outlined by NOAA and others...

Hopefully the paper will find good use as discovery of these sea stars becomes increasingly more common...