Tuesday, September 24, 2013

Brittle Star Domination! When Ophiuroids Carpet the Murky Deep!

Common brittle star
Image by MatYts
Brittle stars are THE most diverse of living echinoderms.

There are well OVER 2135 species known and many more discovered every day.  However, its not enough to know that there are many KINDS of brittle stars, but another important fact is that they are also some of the most ABUNDANT echinoderms.

They live everywhere..small cryptical hiding things. Under rocks, in crevices, on other animals, under other animals, buried in sediment, even hiding among OTHER brittle stars!

Here, for example are brittle stars with their arms emerging from the holdfast (i.e. the anchor) on kelp!
Brittle Stars Infestation of Holdfast
Image by Mr. Lobos
So, sometimes, it strikes one as kind of unusual when all of a sudden you see them literally CARPETING the seafloor!
Brittle Star Carpet
Image by Jylnott
What's going on with these?? When we see this many of some OTHER echinoderm, we often wonder if there is some ecological problem.. For example, with sea urchins, we have a situation where we see "urchin barrens"   and really.. you can't help but wonder what's going on here...
Purple Urchins
Image by Anne Crawley
In this case, the removal of predators has unleashed a huge torrent of sea urchins which devour everything in their path!  Hence the name "barren" because there is naught else but urchin!

When one sees brittle stars en masse, one cannot then, be a little concerned...
spiny brittle star
Image by shawn_broes
BUT fear not!  As it turns out, these massive aggregations of brittle stars are NATURAL. So while the effect appears the same, perhaps "barren" is not quite as appropriate or even accurate!

What's going on? 
So, I'll discuss two kinds of situations where brittle stars literally CARPET the sea bottom.

In a cold-temperate water genus of brittle stars, called Ophiothrix which you can find in Europe, and in the cold-temperate waters of both the Pacific and Atlantic coasts of North America, they frequently occur in very dense, very abundant numbers!

How dense?  One paper by G.F. Warner found that the mean population of O. fragilis in the British Islands was found to cover 23% of the ground in some areas, with a mean population density of 1330 indivdiuals per square meter!! 

For example, here's a couple of nice shots of dense Ophiothrix fragiis beds them from Scotland (and thus the North Atlantic!)
IMG_0187
Image by MatYts
Brittle stars. Ophiothrix fragilis.
Image by hsacdirk
This one is a pic of a different, Pacific species but it is a tighter shot and it gives you an idea of how the animals are positioned and what they look like individually.. Note that their arms are ALL extended up into the water!
brittle star
Image by echo&dust
Spines are ALL over these things.. but they aren't necessarily for defense!
Brittle stars. Ophiothrix fragilis.
Image by hsacdirk
Here is a nice video of Ophiothrix in Santa Barbara, where they completely carpet the bottom.  

Another video of Ophiothrix from Anacapa Island, Channel Islands

And another species occurring in Monterey.. perhaps members of the Amphiuridae..

In either case, arms are extended into the water current where their spines capture organic food particles being carried along by the water....Spines are used in conjunction with tube feet for filter feeding!  WATCH those tube feet go!  An example of the original science of this can be found here.

So, they're feeding. Fine.  WHY ARE THERE SO DANG MANY OF THEM???
Wall of brittle star
Image by Kristy Moore
HOW did they get there???  Did they all migrate there?  Or did they all just kinda... START there and never went anywhere else?

YES! This paper by Raphael Morgan and Michel Jangoux showed that larvae were encouraged to undergo metamorphosis into adults by the presence of OTHER adults.

So, in theory, one or others settle down because they are taking advantage of a desirible water/current/food flow. And then another and then another..

And before ya' know it the larvae in the water sense that other adults are around and THEY settle out and more and MORE...
Brittle stars
Imge by MatYts
...and BOOM there goes the neighborhood!  Even if you're a voracious Crossaster papposus "rose star" you can only eat and go through so many brittle stars...
IMG_0175
Image by MatYts
If you're an urchin or a starfish trying to make an earnest living, you've got to push all the pesky things out of the way! 

Filter Feeders can also be found in the deeps! Remember Brittle Star city?? Go here to see a nice write up of this massive colony of Ophiacantha living on a near-Antarctic seamount! 


But What about in the Deep-Sea???
I said TWO kinds of brittle star carpets! so here ya' go...    Ophiuroids are crazy abundant in the deep-sea as well.. comprising a HUGE amount of the biomass living on the bottoms!
exp_R_levin_ophiuroids_001
Image by Scripps Oceanography
Here's a dramatic image by my Japanese colleagues at JAMSTEC from the Shinkai 2000 submersible of Ophiura sarsi carpeting the bottom...

yikes.

The story is in many ways similar to those at shallow water depth.. juveniles sense the presence of other adults and settle.. but arms are not upheld in the water as readily... What could they be doing down there?

Many have indicated that they are possibly detritivores. Feeding on dead stuff and other organic material as it falls to the deep-sea bottom... as seen here (and fighting amongst each other for food!)


In one of my earliest posts.. I also shared the delightful world of these brittle stars as PREDATORS of moving prey! A living carpet of OPHIUROID DEATH!   You can read more on that here. 
thanks always to Steve Stancyk for the images!

Ophiuroids! I wouldn't want to mess with a bunch of them in a dark alley! They're takin' over!

Tuesday, September 17, 2013

Who Named the Bobbit Worm (Eunice sp.)? And WHAT species is it.. truly??

Bobbit worm (Eunice aphroditois)
Photo by EunJae Underwater Photography
There's a certain few marine invertebrates, which for various reasons, capture the imagination of the public and manage to get a foothold into popular culture. Bathynomus-the giant deep sea isopod!  Sea Pigs, such as Scotoplanes and their relatives-weird looking deep-sea sea cucumbers. 

Among this pantheon of photogenic and/or striking bunch of marine animals is a formidible polychaete worm- in the genus Eunice, also known as the BOBBIT WORM!

Here's video of this animal's remarkable prowess (more videos are here). These worms  reach 3 m (~10 FEET) long and are raptorial predators which use spring loaded jaws to capture their prey... One record holder indicates a worm which was nearly SIX meters in length when collected! 

Yes. That's basically a worm the size of a large SNAKE with jaws to match!

This animal has been getting increasingly more exposure as various sites have been introducing marine invertebrates into their blogs and such. This is a good thing for those of us who study marine invertebrates. An animal once known only to specialists is now becoming accessible to everyone..

I've noticed increasingly however that many of these newer accounts of the Bobbit Worm are missing something.

Where did such a distinctive NAME come from?  Wired asked where the name came from! And they were not answered.  Even my colleagues at Deep-Sea News asked and were not answered! 

This question has even been probed in scientific journals by scientists! This has led to more questions!

Where does the name "Bobbit Worm" Come from?? 
In 1993 a case hit the headlines with such a resonant act, it came to be one of the defining news pop culture items of the decade. A woman, Lorena Bobbit, cut off her husband's penis with a knife. The penis was re-attached.  You can read all the gory details on Wikipedia.

In the late 90s, circa 1993-1995, I was a grad student/ curatorial assistant in Invertebrate Zoology at the California Academy of Sciences.  (I'm ancient like the hills!)  I was working through my Masters and had not yet left for my PhD.

Part of my time there involved my helping two of the curators, Gary Williams and Terry Gosliner, who were experts in soft corals and nudibranchs, respectively, identify starfish for their upcoming book on Indo-Pacific animals.

During the research for the book, Gary and Terry returned from a trip to the research dive to the Philippines where they spied a crazy thing. A great story that was told one brisk Friday in San Francisco!

(story recreated here with new images) A GIANT worm with spring loaded jaws the size of a SNAKE jumped OUT of its burrow and grabbed a freakin' FISH while it was swimming by! Images below by Eunice Khoo (Mer Mate)
Bobbit wormBobbit worm stretch
Bobbit worm attack
Image by Jason Isley
I didn't believe it. But there it was.

Bear in mind. Digital cameras were just becoming available. HD underwater Video was nowhere nearly as good as it is today. YouTube was non-existent. The WWW was around but didn't have the size and scope it was today. Most people didn't even KNOW polychaetes were any larger than about a foot long at most. If you saw polychaetes in a coffee table book or marine biology photo magazine you were pretty lucky. The only people who ever saw these huge monstrous worms were divers, scientists and maybe the locals.

Eventually on one of their trips back, Gosliner and Williams managed to collect a specimen AND a picture of the animal, which they caught a picture of and put into their book, published in 1996...
(and which is quite good with many verified identifications. Go here to pick up a copy
The specimen had been identified to genus, Eunice sp. but not to species (I'll explain more below), but Terry Gosliner felt that it a special beast worthy of distinction! And hence the name... (excerpt below from their book)

So, Dr. Terry Gosliner, curator of mollusks and world expert on nudibranchs was the man who coined the name BOBBIT WORM. At the very least, this is the first account of the name in the literature. 
The timeline and scenario is consistent
  • When divers started looking for books to ID the critters they were seeing, they went to Gosliner et al.'s 1996 ID guide. There were other Indo-Pacific field guides around, but none used the term. 
  • As we entered the era of YouTube, Flickr and kajillion pictures of the Bobbit Worm, how did an obscure 90s reference make it into such common use? The book named the animal and it circulated. 
  • Terry Gosliner verifies himself as the name's originator!
Some clarification on various myths that have arisen....
  • The Bobbit worm name is based on the act of the knife cuttin off the Bobbit Junk. Further analysis (inappropriate blade type, the worm named for a phallus, etc.) is over thinking it. 
  • Other various stories about female Bobbit worms attacking the genitalia of male Bobbit worms are not just wrong but WAAAY wrong. Polychaetes don't have penises. 
  • And there are no reports (that I know of!) of Bobbit worms attacking tropical men swimmin' around with their junk out!

So, what species of polychaete IS a Bobbit Worm??
One major misconception that HAS arisen however, is that because the Bobbit worm is big and obvious that we know what it is! i.e. what species it is...
Eunice (Polychaete?) Worm Detail
Image by Mark Atwell
After Gosliner & Williams collected the worm, they sent it to the Smithsonian's world polychaete expert Kristian Fauchald. He identified it to Eunice but stopped short of the species.

Why? Because the group is... complicated and this has some bearing on exactly WHAT a Bobbit worm is. Allow me to explain.

We often see the species name Eunice aphroditois used as the species name for the Bobbit Worm, such as here in Wikipedia and in many other places.  But this is almost certainly an oversimplification.

Since its original use, the common name has been largely applied to almost any large, predatory polychaete, which most untrained "citizen scientists" such as divers, aquarists, etc.  are generally unable to distinguish.

For example, is this a "proper" Bobbit worm?  It looks close, but lacks the same kind of jaws. So, probably not. But its not unsual for big, attractive polychaetes to get labelled "Bobbit Worms"

This for example is another species of Eunice (I think..) but is it a "Bobbit worm"?
9522 Bobbit worm
Image by Ken Traub aka Diverken
The genus Eunice itself, contains OVER 350 accepted species found all around the world! Go here to see a list of them.  Even if you pare down that list to ONLY the really big ones as was done in this article you're still looking at a HUGE number of species that have since fallen under the umbrella term "Bobbit worm."

In fact, one hugely complicated problem is the definition of the "Eunice aphroditois" species concept itself. A problem outlined here by Sergio Salazar-Vallejo and colleagues.

The problem breaks down like this:
The 'Proper" Bobbit Worm was a species originally observed from the Philippines and may or may not be the same species frequently observed in Indonesia and thereabouts in videos and such. In fact, if you read the description above, it was originally thought to be a new species and still may be!

This paper by Anja Schutlz further outlines methods that we might further understand the questions surrounding the question "What species is the Bobbit worm??" Population genetics of the world populations and further sampling of species from around the world.. (as well as people who can identify them correctly).
The stuff of nightmares
Beautiful photo by Eric Cheng! 
So, conceivably we have not even SEEN the TRUE Bobbit Worm (i.e. the animal originally named as such) as a proper species yet!

But because the common name "Bobbit Worm" seems to have become rather liberally applied to most large eunicid worms, its likely that name will stick. Not just to Indo-Pacific eunicids but to others..

and THAT is the rest of the story...  (old-timers joke!)

Tuesday, September 10, 2013

Starfish Wasting Disease!


UPDATE: you can now upload YOUR pictures of starfish wasting disease. They are being tracked at this website (iNaturalist)

Last week I reported on an unusually large die-off of the North Pacific sunflower star, Pycnopodia helianthoides (among other starfish species) in the waters of British Columbia. The story even got picked up by National Geographic!
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This sparked some good academic discussion here which I can only hope will lead to some further insight into what is happening.  One useful thing which came up was the mention of something that would be a good follow up to last weeks' report:  Starfish Wasting Disease!

I have spoken of ciliate protist parasites in sea stars before but this is something different.

Details of the post today about Starfish wasting disease is based on this paper in the journal, Diseases of Aquatic Organisms from an article by Amanda Bates, Brett Hilton and Christopher Harley in 2009

Other information is from an account of starfish wasting disease in the Channel Islands by Ginny Eckert and colleagues. This paper is freely available here.

I should also mention that my friend and colleague Dr. Allison Gong has documented an outbreak of wasting disease in her water table at UC Santa Cruz. I've borrowed many of her pictures below. My thanks to her for allowing me to use them! 

What is Starfish Wasting Disease? 
Symptoms of the disease are relatively straightforward:
  1. White colored lesions appear and grow rapidly
  2. There is a loss of body pressure (i.e., turgor)
  3. Body disintegration and autotomy of arms, etc. 
  4. and finally death...
Bates nicely outlines the various stages of the disease in her paper focusing on Pisaster ochraceus, the ochre star.
Fig. 2 from Bates' et al. 2009
Allison Gong recently documented these symptoms in her blog

Lesions...


followed by decay and autotomy (i.e., arms begin to shed..)





The effects DO seem very similar to what happened with the Pycnopodia die-off
P1050330
fr. Jonathan Martin
But what actually causes the disease?? Sadly, we are just beginning to understand it and so we don't actually know WHAT the causative agent is.  Molecular tests for bacteria haven't confirmed anything.
Could it be a virus? A fungus? Some strange combination thereof?

Its also unclear if it is the SAME agent at work in EVERY case. Different species? Different strains? Different diseases?

The symptoms of the disease have been documented widely: on the west coast of North America. From British Columbia down to the Gulf of California. But also in the Mediterranean and the North Atlantic coast of North America.

Nothing yet from the Southern Hemisphere.. Australia, New Zealand, etc.

What Species Does It Affect?
Wasting disease appears to be pretty widespread across MANY starfish groups. 

The symptoms of the disease have been observed as early as 1972 from the east coast of North America in the "common" starfish Asterias vulgaris (now called Asterias rubens, pic on the left)

In 1982, there was a mass die-off of Heliaster kubiniji in the Gulf of California, which was so severe that it led to local extinction in several areas where it had once been abundant. (Image of Asterias by "misenus1", Image of Heliaster by manzanita-pct)
Northern Sea Star, Asterias vulgarisGulf Sunflower Star

Eckert's account in the Channel Islands however, documents the widest spread where it was recorded affecting TEN species of most commonly occurring sea stars! Not to mention three sea urchins, two brittle stars, and one species of sea cucumber!

Disease outbreaks in these species resulted in die-offs and significant population declines.

In our recent example with Pycnopodia, which looks very much like wasting disease, we saw not just Pycnopodia, but also the sun star- Solaster dawsoni..(pics by Jonathan Martin)
P1050397P1050395

Solaster dawsoni feeds on sunflower stars..

Similarly, Allison observed the bat stars, Patiria miniata feeding on decaying Pisaster ochraceus. Can the disease be conveyed as food? Will we start to see greater spread? 

But again, we don't know the actual agent of wasting disease. The symptoms might be something that happens in parallel as a result of several different agents.

Temperature! The Key to Wasting Disease
Eckert's paper speculated that warmer waters in the Southern California region accompanied the onset of wasting disease in the species they studied.

Amanda Bates & her team study studied Pisaster ochraceus in British Columbia and studied several variables and how they affected the disease. 


Indeed, temperature turns out to be a very important factor in the spread of starfish wasting disease! 

The graph below shows that the prevalence of the disease in starfish under experimental conditions is significantly higher under warmer conditions. This was also reflected by observations in the wild as they saw higher incidence of disease in the summer (June) than in August.
Figure 3 from Bates et al. 2009
One final and important observation that Bates and her team recorded was that the disease prevalence was higher in a protected inlet (GM=Grappler Mouth) versus an open wave-swept area (SB=Scott's Bay). 

This highlights another aspect: What aspect of starfish in the protected inlet vs. the open area to the higher infection rate? 
  • Wave action? (and thus more current and temperature circulation)
  • Freshwater input? resulting in higher vulnerability? (starfish don't tolerate freshwater very easily) Sewage? 
Aquaria, it was observed, also tended to show higher incidences of infection. 

So, it appears there seems to be a good correlation with wasting disease prevalence and infection strength with higher temperature. Also being exposed to open ocean conditions vs. more enclosed conditions..

Starfish Wasting Disease in the Big Picture

1. Global Warming. If this disease and the ciliate castration parasite are both temperature dependent and we are seeing an across-the-board increase in ocean temperature, this could have significant or even profound effects on populations.  

Higher rates of diseases and greater vulnerability to diseases affecting not just sea stars, but urchins, and other echinoderms could seriously impact populations of these species. 

2. Impact? Many if not all of these sea star species (to say nothing of the other possible echinoderms that could be affected) are what's called keystone species, that is, in an ecosystem their presence (or absence) represents a profound effect on many other species. 

Ochre stars for example affect mussels and other animals in marine ecosystems that cover rocky intertidal bottoms. Sunflower stars are a major predator of everything from snails to sea urchins, and sometimes other starfishes. 

Diseases like this can decimate or remove these ecologically important species resulting in unforseen results! Just consider this case about abalone and otters as one example..

Tuesday, September 3, 2013

Mysterious Mass Sunflower Starfish (Pycnopodia) Die-off in British Columbia

<i>Pycnopodia</i> detail

Today is a "report from the field" by Jonathan Martin, a research associate at Simon Fraser University, who is among other things, an ROV pilot, diver and photographer. His pictures can be found at this Flickr stream here.

Martin has recently sent me a series of images and video that show a massive die off of the sunflower
star, Pycnopodia helianthoides in the waters of British Columbia in 20-50 feet of water.

A picture of the sunflower star in a healthy state is above. Pycnopodia is a prominent member of the Pacific northwest intertidal/subtidal marine fauna. It boasts about 20-25 rays and can get to be quite large (about 2 to 2.5 feet across).

A couple of years ago I wrote about a huge Pycnopodia population explosion in British Columbia waters.

ALL pictures in today's post were provided by Jonathan (except where noted otherwise).

The Evidence: Images & Video

Here's a video transect made by Jonathan


See all that white stuff on the bottom?? Those are decaying, white tissues and ossicles from sunflower stars. You can see the fleshy remains all around the bottoms.

His direct observations (dated August/September 2013):
I just got back from a dive out in West Vancouver though, and there seems to be a huge mortality event of some kind with the animals, where they seem to waste away, 'deflate' a little, and then just... disintegrate. The arms just detach, and the central disc falls apart. It seems to happen rapidly, and not just dead animals undergoing decomposition, as I observed single arms clinging to the rock faces, tube feet still moving, with the skin split, gills flapping in the current. I've seen single animals in the past looking like this, and the first dive this morning I  thought it might be crabbers chopping them up and tossing them off the rocks. Then we did our second dive in an area closed to fishing, and in absolutely amazing numbers. The bottom from about 20 to 50 feet was absolutely littered with arms, oral discs, tube feet, gonads and gills, the the extent where it was kind of creepy.
More pictures of Pycnopodia in various states of decay..
P1050297
P1050330

P1050364
Partial remains of a disk and white, dead starfish tissues..

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In some cases, arms were separated with tube feet still moving around
P1050317P1050363

What makes this such a concern?  OTHER starfish species in completely different lineages also seem to be affected. The sea star predator, Solaster dawsoni was also observed in various states of distress..

Solaster feeds on other starfish and does feed on Pycnopodia, so is there a connection??  Especially with the recent population explosion??
P1050360


P1050344


P1050397


P1050395


So What's Going On? 
So, there were a number of different ideas that buzzed through my head. Again, this is all SPECULATION on my part...

1. Is this related to the population explosion, observed almost 3 years ago??  Could the huge populations from 2010 be suddenly dying off? Famine? Disease? (see below) This would be an unusual (or at least poorly known) phenomena. I've seen Pycnopodia in aquaria  live out long lives, so I don't think this is some kind of "natural causes" thing...

2. Could this be a disease?  Jonathan has mentioned the ciliate (Protist) parasite which inhabits sea stars in the Pacific Northwest. The ciliate effectively castrates the host, but has never been observed to actually cause much more damage than that. And accounts of the ciliate suggest that it occurs in a very small % of the overall population.

There are accounts of many sea urchins being decimated by various bacterial infections, such as Bald Sea Urchin disease but my skim of the literature suggests that there isn't anything known about similar diseases in sea stars.  Most mass-mortalities of seastars have been associated with environmental changes- freshwater from rains, storm and wind, toxicity in the water from geological events and so on...

Could this be related to what has been observed on the East coast with Asterias See also this report. Where populations of the well-known intertidal starfish (and btw, SAME family as Pycnopodia) have been undergoing population declines for unknown reasons.
Purple Starfish
Image by lifeboy252
3. Why is it affecting other species? So we have one big Pycnopodia die-off. Why have all the Solaster stars ALSO been dying?  One immediate answer might be that whatever toxic substance is in Pycnopodia has been fed upon by Solaster, resulting in further mortality. Or it could be in the water.. More data and observations are needed.

Have other species in completely different ecological regimes died? 

SO FAR, this has been observed only in the British Columbia region. Hopefully, this is just an isolated incident and nothing that will be slowly moving in any other direction. 

I'm not an ecologist or an invertebrate pathologist.. so maybe someone out there with an appropriately equipped lab will embrace this and seek out the answers?  and hopefully whatever it is, won't be much more widespread..