Tuesday, May 16, 2017

Tremaster mirabilis! Five things I have learned about a Fantastic Starfish!

Baker Island
Back in 2008 I wrote a post about a great looking starfish that I wanted to know more about, a weird looking deep-sea star called Tremaster mirabilis!  

Its a striking looking animal and its not unusual for odd looking animals to have some kind of story attached to it..and as we learn more about it, the more intriguing it becomes! 

The species name "mirabilis" is Latin for "wonderful" or "to marvel at" and as we'll see the genus name Tremaster has an equally appropriate descriptive etymology! 

Since I wrote that introductory post in 2008 not only have I learned more about it-but we've now seen it ALIVE all over the Atlantic and  the tropical Pacific thanks to the livestream videos of Okeanos Explorer!

Brief Introductory Details: Tremaster is a starfish in the family Asterinidae, that puts in the same family as "bat stars" and a bunch of other sea stars you probably recognize from shallow waters and home aquariums. Go read this account on this huge and diverse group, which I wrote a while back...
Bat star
image via Flickr by Ed Bierman
But one of the people I/we owe the MOST to is a diligent and smart-as-a-whip young researcher named Ms. Katie Gale (more at her website here) who was working in the deep-sea biology/ecology & reproductive biology lab of Dr. Anne Mercier at Memorial University in Canada! 

Katie published this great paper on feeding biology and ecology of deep-sea asteroids collected off the coast of Canada in the North Atlantic in Deep-Sea Research in 2013.  I blogged it up here.

During the course of Katie's research she collected a fair amount of cool "anecdotal data" which amounts to singular observations and some other stuff which furthers the "natural history observation" of a starfish about which we know very little!   So her observations along with some further observations from the 2017 research legs of the NOAA Okeanos Explorer, some further homework on my part and voila!

Let us learn MORE about the weird starfish Tremaster mirabilis!

1. It eats coral (possibly)
Probably one of the BIGGEST questions I had for such a strange looking sea star! As we'll see, this species is seen quite a bit and yet one of the most immediate questions about it seemed elusive!

Fortunately Katie Gale was quite lucky and was able to capture and image of this specimen of T. mirabilis taken by the fine people who operate the Remotely Operated Vehicle ROPOS/DFO. Gale's paper cites this image showing our mysterious starfish feeding on CORAL! 

Specifically the octocoral Acanthogorgia!  
Tremaster mirabilis occurs widely around the world and of course, its always possible that there is variation in feeding or that possibly the animal in the picture has somehow been caught doing something completely else that we have no clue about-BUT our best guess is that its feeding. So, we continue on with that notion..

BUT we have THIS image taken on Whaley Seamount during Leg 3 of the Okeanos Explorer mission at 875m!

Could its location on the rock surface be because its near a yummy food source? Another coral predator to add into our understanding of deep-sea coral ecosystems???


2. Time lapse movement and?? 
This probably seems like a common sense thing-we KNOW starfish move albeit VERY slowly. and can actually show some behavioral complexity (here) 

Katie nabbed some of this GREAT video showing this species moving around its aquarium and more importantly NOT attacking this sea anemone in the aquarium.

This is actually an important point because we know MOST starfish CAN move but they often don't.

So, ACTUALLY capturing it doing so gives us some insight into what they do when we aren't watching them..
Tremaster mirabilis and Flabellum
Katie for example caught THIS unusual variation in posture:  Could this be avoidance of the bottom somehow? Filter feeding? Some kind of stress response? 
Tremaster mirabilis
Note in this image that the "skirt" is lifted compared to the in situ Okeanos images below where the animal is flush with the bottom..
Tremaster mirabilis
What is it doing?? This is a bit of a A mystery. 

and on Pau Pau Seamount and elsewhere Tremaster  is CRAAZY abundant! Are they moving around to feed? to reproduce?  How does all of this come together??? These behavioral bits add to our understanding but also to the mystery!

If we sped the movement of this "constellation" of Tremaster mirabilis up, would we still see no movement? or  is it a Times Square of Deep-Sea Starfishes??? 

3. One species lives in at LEAST THREE Oceans?
It USED to be that everything we knew about this species was taken from museum specimens and indeed we are STILL dependent on samples from throughout the world for new records of where many species live.

There is some question about whether or not this one species "Tremaster mirabilis" is actually one species or possibly several 'cryptic' species disguised by the fact that all the individuals observed all appear to be the same.

 The external characters vary only slightly and its not unusual for a widely occurring species to demonstrate some... variation throughout its range. However, when we examine dead museum specimens we are often missing data such as color and behavior which can be important.  Especially when its range where it lives is at least THREE oceans!

Tremaster is a moderately occurring deep-sea species.. occurring roughly between 200 and 600 m

Thanks to submersibles such as Okeanos Explorer we now have VIDEO and ON SITE (in situ) observations of LIVING animals!

Tremaster mirabilis is supposed to be one species..but as you can see there is a SLIGHT difference in body form..

North & Central Atlantic: An image from Nygren Canyon (top) and the lower image from Puerto Rico. Note there's more of a "skirt" around the edge versus the Pacific ones.
Throughout the tropical Pacific
Here's a brilliant deep-orange one seen on the recent Okeanos leg from Jarvis Island..

And interesting brick colored one from Pau Pau seamount
and this interesting lighter colored individual from Baker Island..

Other Records show this species in New Caledonia and throughout the Pacific. I've not yet seen it from the Indian Ocean however..

Another place where Tremaster shows up? Antarctica and nearby...

4. There are Jurassic Fossils
As if dealing with living animals weren't enough, these intriguing beasts show a CLEAR relationship to at least TWO Jurassic fossils!

Bear in mind that the Jurassic is quite a LONG time ago. These sea star were living in the world's oceans while dinosaurs roamed the Earth!

AND like its modern descendents-these were quite spread out. Antarctica versus Switzerland!

Here's Protremaster felli, from the Jurassic of Antarctica! Described by Andrew Smith and T. H. Tranter in Geology Magazine 1985


and YET another "Tremaster" like fossil sea star, described in 1981 from the Jurassic of Switzerland: Mesotremaster  zbindeni described by famed Swiss paleontologist Hans Hess!
Image from the Wikipedia file: https://commons.wikimedia.org/wiki/File:Mesotremaster_felli.jpg
Close up of the plate detail showing a familiar pattern for "Tremaster" like asteroids...


4a. Interesting Evolutionary History...  I had also mentioned briefly in my account of the importance of the family Asterinidae (here)  And well, Tremaster is possibly VERY important to the evolution of starfishes. It has a history showing them in the Jurassic.. and to those in the know.. these show a close resemblance to several weird deep-sea species! 


5. What does "Tremaster" actually mean? And"brood chambers"??
FINALLY! What does the genus "Tremaster" actually MEAN anyway? "aster" is obviously "star" but it turns out "Trema-" refers to "aperture" or OPENING!

When Addison Emery Verrill described this genus in 1880 he made allusion to these FIVE openings present in each interradius! These were one of the distinctive characters he used to diagnose his (then) new genus!! and "mirabilis" of course refers to "wonderful"

Here's a photo of the underside of a Tremaster specimen.. the openings are indicated by yellow circles!
So, as it turns out if you look more CLOSELY at these openings, they are actually OPENINGS into chambers present INSIDE and THROUGH the body wall and open up on the TOP:


Here are images of a dissected individual from the underside showing these openings (i.e. these are close ups of what's in the yellow circles above)
According to the author who described this species (and subsequent literature), there are actually BROODED young in these chambers! Its not clear to me if they are simply embryos or actual juvenile individuals. Strangely enough, these have not been documented..at least not in the literature that I could locate. and I have yet to actually spot them. But perhaps I've simply not been looking at the right ones...

Thus, the openings appear to provide an opening for water to circulate into these chambers which could serve any number of purposes.. Possibly to aerate the "brood" chambers? Or perhaps they assist in the degree of arching the dome-like shape is capable of??  Filter feeding? Predation??

One of the great things about science is how it marches on! Its been 9 years (!!) since I wrote that first post and I LOVE that what in addition to what I've learned from reading, there has ALSO been genuine progress in learning NEW information on the biology of these animals..  And one of these days we will more FULLY understand it and its strange signficance!

Also GREAT to see that animals like this INSPIRE! Here is a GREAT illustration of this species by "Cartoon Neuron" on Twitter...

Monday, May 8, 2017

Brittle Stars of (squid & fish) Death pt 2! Okeanos Explorer Edition!


This Saturday we were witness to one of the most AMAZING echinoderm related ecology/natural history moments that I've seen in awhile!

Namely watching this brittle star CAPTURE and EAT SWIMMING PREY!.. and this happened all LIVE on Okeanos Explorer's live stream deep-sea research!  http://oceanexplorer.noaa.gov/okeanos/media/exstream/exstream.html

The Okeanos Explorer was surveying Jarvis Island in the central Pacific at a depth of about 400 to 500 m. They were watching a tiny squid swimming through a thicket of deep-sea "bushes" composed of hydroids and worm tubes, covered by many, MANY animals including brittle stars!

Most times we see brittle stars, they have their arms up in the water, presumably filter feeding... Brittle stars are frequently numerous as I've written about here. 

The tiny squid (apparently in the genus Abralia (as identified by Mike Vecchione at NMFS) was moving along its merry way..when suddenly.... (at 0:25 to 0:30) the tiny squid is knocked around and then CAUGHT by the arm of one of the ophiothricid brittle stars!!!

(video captured by 2011ACVVV)
(video captured by Steve Hornik of the Facebook Underwater Screengrab Group)

As indicated by the Biology Co-lead Dr. Scott France "Did that really happen?"

Here it is again blow by blow...

Spines in these brittle stars is sharp and often with jagged edges..so capturing something soft-bodied isn't TOO surprising..

Brittle star eating dead squid! followed by many OTHER brittle stars sharing the prey!
 
The GIF 
WHAT?? Brittle Stars feeding on swimming prey? THAT'S CRAZY! but, its happened before...

Yes! Most of us don't think of sea stars OR brittle stars as capturing fast moving or SWIMMING prey!  Strangely enough, THIS WAS CAUGHT ONCE BEFORE!!

Once, back in 1996 at the San Francisco International Echinoderm Conference Dr. Steve Stancyk and C. Muir at the University of South Carolina and Dr. Toshihiko Fujita of the National Science Museum in Tokyo presented some fascinating data showing the very abundant deep-sea brittle star Ophiura sarsi capturing and then swarming over and DEVOURING fish and shrimp as they got too close to the abundant carpets of brittle stars on the deep-sea bottom!!!  Here was my blog post about back in 2008! 

I remember seeing the presentation of this talk at San Francisco State University. The room was Standing Room ONLY! EVERYONE had to see the famous video of the brittle stars capturing swimming prey!!

BUT ! Dr. Stancyk has graciously NOW permitted his VIDEO of this event to be put up on Youtube making it AVAILABLE FOR THE FIRST TIME!!Basically... at about 4:48, a myctophid fish (and later a squid) gets too close to the "brittle star carpet", gets caught in a loop by the arm, gets DRAGGED down and then overcome by DOZENS of brittle stars!!! 


 Perhaps the most...striking part of this and the Okeanos Explorer video is how.. BRUTAL the brittle stars are when finally tearing apart their prey. Ophiura sarsi was literally rending those fish and squid apart! 

Similarly.. the ophiothricids seen by the Okeanos were carrying off their tiny squid prey..likely to be devoured by many, brittle stars which collaborated in the capture... Ophiuroids have teeth! and presumably DO use them on food! 
What will Okeanos Explorer see next??

Tuesday, April 25, 2017

Okeanos Follow-up: Giant Sea-Spiders EAT! Cnidarians, Anemones, Hydroids & Corals! oh my!

Many of you know that I occasionally "call in" when the NOAA deep-sea research platform Okeanos Explorer goes out to see on its missions. (remember the next leg BEGINS APRIL 27  http://oceanexplorer.noaa.gov/okeanos/media/exstream/exstream.html)

Mostly I call in on starfishes or echinoderm biology..but I do have a broad interest in deep-sea biology. And I just LOVE seeing observations like the one above: a weird animal doing something no one is familiar with!

And the BEST thing about Okeanos Explorer? EVERYONE can enjoy it along with you!! Here's a BUNCH of Sea spider observations from the Atlantic Okeanos Explorer in 2014! 

...BUT of course, our ship and shore-side scientists can't know EVERYTHING. We'll often observe an event, many of us make note of it in case we see it again and often times we'll move on.... forgetting about it until such a time when the observation comes up again.

ONE such observation was one from 2014 on the Atlantic Physalia Seamount wherein we observed a sea spider in the genus Colossendeis sp. with its proboscis (that's the long cigar shaped feeding tube) stuckINTO into this hydroid (an animal similar to a Hydra from freshwater)! Was this feeding? Was it NEW?
Physalia Seamount in the North Atlantic
A brief into: Sea spiders are not spiders. They belong to a group known as the Pycnogonids (also called the pantopods) which are mysterious arthropods. Some folks consider them distantly related to the greater group of arachnids whereas others think they are even more unusual...

Most sea spiders are pretty tiny and are less than about an inch (2 cm) across and its not unusual for them to be quite cryptic. So even though they can be present, you really DO have to look for them...
Here a photoessay of tropical, shallow water species by scientist/photographer Arthur Anker displaying some spectactular colors!   Here's a spectacular male carrying eggs..
Male ovigerous sea spider (Pycnogonida)

Many live in shallow water but are never seen (hidden and small)... but that's NOT a problem with the deep-sea and Antarctic species!  There's one frequently encountered genus: Colossendeis which is one of the largest known sea spiders reaching a leg-to-leg diameter of over 50 cm! that's almost a FOOT and a HALF!

Most members of Colossendeis live in the proper deep ocean abyss: roughly 1000 to 5000 m and also in Antarctica where the cold-waters allow them to occur in relatively shallow water settings.

Note also the sizeable cigar shaped projection at the top end! That's called the PROBOSCIS! That will be important later! That is presumably what they use to feed.
Image from page 96 of "A contribution to American thalassography; three cruises of the United States Coast and geodetic survey steamer "Blake," in the Gulf of Mexico, in the Caribbean Sea, and along the Atlantic coast of the United States, from 1877 to 18
Unfortunately, there is relatively little information known about sea spiders..... And the deep-sea species? Even less!

So, were the observations something unusual? Has science encountered something like that before??

But much to my delight: YES! There WAS a previous account of sea spiders feeding! and WOO HOO!  It turns out my friends at the Monterey Bay Aquarium Research Institute in Moss Landing, California actually observed something JUST LIKE THIS in 2010!!! Here was their blog post about it! 


The paper, by Caren Braby, Vicky Pearse, Bonnie Bain and Bob Vrijenhoek was published in Invertebrate Biology in 2009, 128(4): 359-363. and it documented "Pycnogonid-cnidarian trophic interaction in the deep Monterey Submarine Canyon"

They observed the same genus, Colossendeis, but at least two species, C. gigas and C. japonica feeding on commonly encountered sea anemones in the deeps of Monterey Canyon.
Braby's paper reveals that only Colossendeis in Antarctica had been observed feeding. These animals fed on limpets and bristle worms and in 1999 sea spiders were observed feeding on sea anemones

Braby et al.'s observations were the first for deep-sea Colossendeis (as opposed to Antarctic) species. Her team's work focused on their feeding on the deep-sea "pom pom anemone" Liponema brevicornis, an unusual sea anemone which literally "rolls" along the bottom of the deep-sea in a manner similar to a tumbleweed!

After the last 2017 Okeanos leg in the Phoenix Islands, I rounded up a BUNCH of the sea spider-feeding observations and decided to share them here as a comparison! Who knows? perhaps it will inspire a further paper!

Remember that NOAA's Okeanos Explorer program has captured these images and made them available for EVERYONE's enjoyment! Please remember that the next time someone talks about government funded science!

Pacific Observations! Over the last few weeks of the Phoenix Island expedition, we saw a BOUNTY of sea spider feeding observations!  

Winslow Reef: This one had its proboscis firmly ensconced into this flytrap anemone and was apparently sucking something out of it! The rather lethargic looking appearance is likely the result of being on the receiving end of whatever is going on here...

And ANOTHER on Winslow Reef! that was QUITE a dive! Here's another flytrap anemone with a sea spider attacking it!   As we saw earlier from Monterey Canyon, sea anemones and other cnidarians seem to be one kind of preferred food!

Baker Island we saw one attacking what was identified as a cup coral...The proboscis seemed to be "drinking" pretty heavily on this one...


Howland Island.....and just for good measure they saw this one crawling over a glass sponge

More Atlantic Feeding? Here we had a sea spider in the Atlantic Nygren Canyon which has been identified as Pallenopsis (thanks to Bonnie Bain), climbing and possibly feeding on this sea pen.

So, unfortunately I'm not really a sea spider taxonomist, so beyond the genus Colossendeis, I'm not sure how many species we are looking at here..but images such as this inspire many questions: Is predation specific to species? Or generalized?  How significant are these events to the ecosystem?
Do sea spiders attack the big colonial corals as well?

Stay tuned for the next exciting episode!

Friday, March 17, 2017

Okeanos Tropical Pacific Highlights: RARE and BRILLIANT Echinoderms!!

Over the last 10 days or so since Okeanos Explorer has resumed its ROV-telepresence based exploration of the Phoenix Islands and adjacent areas in the tropical Pacific they've seen some REMARKABLE animals of all kinds, from corals to siphonophores, crabs to ribbon worms, etc... but particularly ECHINODERMS!

Before I get into the cool pix.. remember NOAA OPERATES Okeanos Explorer!! NOAA has been threatened with severe budget cuts. CONTACT YOUR CONGRESSIONAL REP AND TELL THEM THAT NOAA IS AN ESSENTIAL Agency!

1. PELAGOTHURIA!  The "TRUE" swimming Echinoderm!!
I have written about this amazing animal before when I found an image of it misidentified as a jellyfish in the Galapagos Rift 2011 Okeanos photo gallery and have written at some length about swimming sea cucumbers here.

Basically, almost all sea cucumbers and indeed most echinoderms are benthic..that is they live entirely on the sea floor and never get into the water column the way fish or jellyfish do.. Yes. Some sea cucumbers can swim but ultimately they return to the bottom.

Pelagothuria is unique because it LIVES SWIMMING in the water column! Similar to the way a jellyfish does. As a result of its strange lifestyle, it has MANY bizarre adaptations and looks unlike most other sea cucumbers much less other echinoderms!

Its not a commonly encountered animal..and we live in a wonderous time that we can see several minutes of HD video of this seldom seen animal swimming by...

The video for this can be found HERE:  http://oceanexplorer.noaa.gov/okeanos/explorations/ex1703/dailyupdates/media/video/dive08_seacuke/seacuke.html
Here are the feeding arms extended into the water...


Pelagothuria is contrasted with this other swimming sea cucumber which, after landing on the bottom, poops and then takes off! (from that unnamed seamount off Winslow Reef)



2. The strange irregular urchin Phrissocystis! From Polo Seamount, about 2100 m we saw one of the most seldom seen spatangoid urchins known! These are highly evolutionarily derived sea urchins which live by digging through and swallowing sediment looking for food.

Although they are bristling with spines, they are actually quite delicate. One collected many years ago apparently collapsed as soon as it was brought out of the water in the submersible collection box!

3. A stunning new phyrocrinid stalked crinoid! From an unamed seamount in the Phoenix Island chain, this bold and striking stalked crinoid was observed..and ultimately collected after it was identified as a new species by crinoid scientist Chuck Messing (based on a paper by Tunniclife et al.)

It was quite large with an unusual texture to the stalk and the cup...

4. The "jumping" brittle star Ophioplinthaca
Brittle stars, distant cousins of sea stars, are EVERYWHERE in the ocean. And especially in the deep-sea you can see them inhabiting numerous cracks, crevices and living on corals!

Some are VERY spiny.. such as this species, what I think is called Ophioplinthaca. We've been seeing these ever since the first leg of the Samoa Expedition.  They seem to occur on corals with the tissue removed.. possibly by the ophiuroid itself..

Another curiosity is that these seem to "jump" off their perches as soon as the ROV approaches. Whether this is due to light, vibration, the bow wave of the D2 or disturbance in the "ophiuroid force" (NOTE: Ophiuroid force does not exist) is unclear...



5. The enigmatic sea star Tremaster mirabilis Here's another strange one! A sea star that basically looks like a bowl on the top of a table!

We've seen these before on Atlantic Okeanos dives (see that here) and I wrote about this animal many years ago before people started seeing them alive..

There is nominally ONE species present in almost every ocean in the world.. they've been found in the Atlantic, around New Caledonia, near Hawaii and in the Antarctic. Not sure if they've been found in the Indian Ocean.

Interestingly, these were found in astonishing abundance on one of the seamount dives



5a. The Deep-Sea Slime Star HYMENASTER 
From Titov Seamount was this glorious, glorious deep-sea SLIME STAR, in the genus Hymenaster.

I've written about the shallow water representatives of this genus here. and explored the diversity of Hymenaster in the deep-sea here


*EXTRA! and of course a bunch of weird sea cucumbers!!
A deimatid sea cucumber with many tentacular extensions, this one from Swains Atoll
and this one from Titov Seamount  but they look to be similar if not identical


This one has been seen repeatedly rearing back and presenting what I think is its mouth into the water. so maybe feeding?

A red one from Polo Seamount
This interesting purple/translucent one from Polo Seamount

Some kind of translucent "sea pig" (family Elpidiidae?) also from Polo Seamount