Tuesday, September 27, 2011

Tilting at Windmills to Tilting at "Killer Starfish"! Ecology vs. Hyperbole!

So, last week the UK newspaper-The Telegraph provided this interesting bit of news...
one of the few times that sea stars have managed to get some front page coverage! The story has been picked up by a bunch of other news sites as you can see on Google...

The quick and dirty version? There is a prominent offshore"wind farm" on the Kentish Flats, about 6 miles off the coast of Whitstable, Kent (this is on the Southeast coast of the UK). More on this here.
There are plans to increase the number of these wind turbines (essentially big windmills) from 30 to 47.

Fisherman are outraged! Why?

The article states that installation of these windmills riles up/disturbs the seabed and this apparently leads to areas that are "swamped with starfish" (presumably the predatory Asterias rubens).
(Asterias rubens image from Wikipedia)
This then leads to concern by the nearby coastal towns that these starfish will prey upon Whitstable's big cash "crop"... OYSTERS!
One fisherman was quoted:
Studies show how wind farms attract starfish that eat oysters and if that happens they will wipe out most of the oyster population here and ruin our tourist industry.

Vattenfall (the company who oversees the windfarms) should have come to the fishermen of Whitstable and asked us what the least damaging place for the wind farm is.

I supply native oysters to 14 Michelin-starred restaurants every week. What will happen to my livelihood if I can no longer do that? It could wipe out our native industry and destroy Whitstable tourism in one hit.
As much as I enjoy seeing press about my favorite animals, I also dislike some of the irrational hyperbole compounded by inaccuracies (and contradiction with science) that seems to infect "popular" articles.

My "take" here would be that the very acrimonious statements by the fishermen seem to come from the long-time enmity that has historically existed between oyster fisherman and the "common starfish" Asterias rubens which is one of the most evident predators of shellfish, such as oysters and mussels.

But the relationships among Asterias and other invertebrates in this ecosystem are MORE than the "killer starfish eat oysters" meme that the article tries to capitalize on..

But are the statements tilting at windmills??? (or windfarms as the case may be!)

Let's find out!!

Much of the data from this post comes from some classic work (1955!) by D.A. Hancock on the feeding behavior of "starfish on Essex oyster beds" that you can find here as a pdf. A nice abstract of the paper can be found here.

So, basically I've assembled 4 points that reflect, uh..lets say some "inaccuracies" in the article. And some information that might shed further light on the ecological players.

I'll caveat of course, that I have no data on the specific ecological case. I'm merely taking a lot of established information and presenting it, so that the more... hyperbolic conclusions... are put into a different context...

1. Asterias rubens is not the ONLY animal that feeds on oysters!
Probably one of the most inoccuous but damaging pests to European oysters is the introduced Oyster Drill, Urosalpinx cinerea. Some info on it here..but short version, each individual can devour about 40 oyster spat per YEAR.

These often leave a nice, neat little drilled hole in the shell.
(from the Marine Biological Association site)

Starfish like Asterias rubens feed by humping over the shell and waiting out or pulling open shellfish valves until they can get their stomachs inside the shell. No drilling or hard parts involved....

Another pest to oysters is the slipper shell-Crepidula fornicata. The "fornicata" part is so-called because alternating mating pairs are often attached to one another. More info on this species here.
Slipper shells aren't predators on oysters but they attach to oyster shells and are thought to be significant competitors for food and other resources that oysters like.

An important consideration here is that Asterias feeds on Crepidula--sometimes preferentially!

Hancock actually had this to say in 1955:
Only when Crepdiula is relatively scare and oysters occur in fair numbers will more oysters be killed. Under the present condition in the Essex rives, Asterias is by no means the most important cause of mortality among oysters and oyster spat; it may even provide some measure of control over the pests such as Crepidula, Balanus (a barnacle), Elminius, and even the fearsome of the fearsome oyster drill Urosalpinx and may therefore be considered as beneficial to the oyster population.
And of course, there are OTHER starfish species, such as Crossaster papposus which can feed on small oysters and other shellfish.. but one important consideration??

These also feed on Asterias!!
here's a picture of just these few players and how they interact...
Bear in mind that these are only SOME of the players. There are likely many more species at play.... Asterias feed on mussels also. I don't know which food source the local populations prefer, but you can spend years working on the ecology of a region like this..

So, fishermen may visually SEE Asterias (or Crossaster) MOST frequently but probably not ALL of the influential animals that affect the oysters they prize so heavily..

Those little oyster drills probably do just as much (if not more?) to affect oyster crops as any starfish.

So, now you see more of the players...what about the game??

2. " and if that happens they will wipe out most of the oyster population here and ruin our tourist industry..." Do the starfish actually eat ALL of the OYSTERS like the fisherman guy was worried about??
So, let's maybe assume that somehow, all those other critters weren't POSSIBLY the cause of the oysters being eaten. Could Asterias by itself in a natural setting STILL be responsible?

This discussion assumes that Asterias rubens in its natural setting, where they interact with their native predators, competitors and environment.

If you introduce a predator like Asterias into an ecosystem, such as with Asterias amurensis in Australia where it has no natural predators or ecological relationships with prey (see this post and this one)-then uh..well, things can get out of hand..

But ecological theory has come quite a ways over the years and our understanding of how predators hunt (and how much energy is expended) leads to many considerations, such as....
  • Will predators always pursue the prey to the very end?
  • When do they "give up" before pursuing new prey?
  • How much energy is expended on different kinds of prey?
  • How does feeding on different prey structure the ecosystem in which the animal lives?
Under natural conditions, predators are generally not more abundant than their prey and cannot ultimately feed on ALL possible prey items (rendering their food source extinct).
(photo by Sue Scott, image from the MarLin Gallery!)

Several experiments with mussels and Asterias rubens in the Atlantic (such as this one by Norberg and Tedengren, 1995) do in fact show that starfish will "give up" on some mussels but not on others. What determines this is not clear-but it may involve variation of different species in different areas as well as shell shape, size and so on.

Other studies suggest that starfish such as Asterias or Pisaster affect the actual ecological structure of the areas in which they live. They devour mussels and/or other faunal members such as snail drills or barnacles that affect the amount of space that different animals settle onto.
This is the basis, in part of the keystone species concept, which I will get some other day...

So, they ARE important in affecting various mussels, oysters and what have you...

But will they eat up ALL the oysters just indescriminately? Nope.

They will likely devour many oysters-but its not even clear if Asterias will always (or even frequently) feed on the largest, showiest (and presumably most desirable for seafood market) oysters (which conceivably have stronger resistance to predation)....

One could argue that Asterias goes after weakened oysters or those with an optimal size for pulling open? Surprisingly, there is not nearly as much data on this as one would think..

3. So what COULD conceivably crash the oyster market in Whitstable, Kent??
There was no evidence in the Telegraph's account about why the fishermen might have been so concerned.. if the windfarms had truly led to an increase in starfish populations. But if you want to be worried about oysters?

This recent study indicates that oyster populations worldwide have plummeted indicating that up to 85% of oyster reef habitat has been lost.

The original paper (click here) shows the United Kingdom region as "Poor". But the overall reason for the decline seems to be due to multiple causes.. including harmful fishing practices, environmental abuse, and decline of environmental quality...

4. One final bit of picayune but thorough nitpicking....The starfish used in the article below?? Henricia sp. does NOT eat shellfish!

So, what we have here to me, seems to be a lot of overblown, hyperbolic fears, probably from years of perceived resentment that really, is probably kind of misplaced.

Instead of Don Quixote tilting at windmills, we have might more appropriately have Asterias' "Tilting at Starfish" (on windfarms)

Thursday, September 22, 2011

NEW! Sea Pig & other Deep Sea Cucumber videos!

So, because Neptune Canada has gone and posted this new deep-sea "sea pig" video.. I've been compelled to go and collect as many deep-sea cucumber vids as I can find and put them here!


This one is an elasiopod sea cucumber, similar to but different from Scotoplanes below.. This was identified by Dave Pawson as either Amperima or Periamma, but is close to Amperima rosea (Perrier, 1896). From the North Pacific...

Observed here feeding on the fine, fine mud of the deep-sea bottom!

Want to know more about "sea pigs"? Click here.

And here's Paleopatides, I believe?

Deep-Sea Sea Pen (Umbellula) & Swimming Sea Cucumber Video! Also courtesy of Neptune Canada! (cuke begins at 1:00 into the video)

I believe this is Enypniastes? bioluminescence.....

Video of the sea cucumber Peniagone swimming...

Hmm.. not sure which one this is..

Enypniastes eximia...an oldie but a goodie!

Tuesday, September 20, 2011

The Encyclopedia of Life-Echinoderm Edition!

Today, I thought I would give everyone some space to introduce my friends over at the Encyclopedia of Life!

The EOL is a huge biodiversity database whose current ambition seems to be to be THE Number one clearing house for information on ALL organisms on the planet-from protists to plants and from archeans to echinoderms!

There's a lot of different databases of critters out there-and by my reckoning- EOL does try to include all aspects of information from taxonomy and information for the scientific professional to basic information for the public.

EOL receives information from many different "content partners" that feed the information on each page. The taxonomy from Marine Species.org (aka WoRMS), or the basic info from the Tree of Life Web project. EOL has just recently uploaded MANY new images to the database!

Given, just how many individual taxa of critters/plants/whatever that exist on Earth, many of the individual entries are a work in progress and we can see the project progressing for quite some time..

Here are screen grabs of each echinoderm page by Class which are each linked to the respective EOL page!
Here is the main Echinodermata page..

Some 4,923 images of echinoderms are present! I don't believe fossils are quite yet part of their repetoir as yet though...

The Asteroidea (sea stars aka starfish) 1877 images!!

The Ophiuroidea (brittle stars, basket stars, serpent stars) 686 images!!

The Echinoidea (sea urchins, sand dollars, heart urchins, etc.) 1524 images!

The Holothuroidea (sea cucumbers & sea pigs) 632 images

The Crinoidea (feather stars and sea lillies)- 227 images!

Thursday, September 15, 2011

Some neat deep-sea ROV video from Canada!

A little bit of Echinoblog extra today! thanks to biologist Jackson Chu (His website can be seen here. thanks Jackson!) has posted some exciting new deep-sea video that *needed* to be shared...

Deep-sea Echinoderms from Canada (submersible ROPOS from what the tags say..)
This starts with Gorgonocephalus and proceeds to show deep-sea cucumbers (including some sea pigs!), various starfish, other ophiuroids and sea urchins...

Deep Sea Echinoderms (Northeast Pacific) from Jackson Chu on Vimeo.

Also kind of cool... video of the predatory tunicate Megalodicopia (not an echinoderm-but closely related to you and me). Most tunicates are filter feeders-but these have modified their "in" siphons so that they capture prey in the bowl-shaped hood...
(and on top of it you get some cool music from Kill Bill!)

The predatory tunicate (Megalodicopia) from Jackson Chu on Vimeo.

The Galiano Glass Sponge Reef in the Strait of Georgia! (Vancover Island)

The Galiano Glass Sponge Reef from Jackson Chu on Vimeo.

And More glass sponges!

Glass Sponge Biology from Jackson Chu on Vimeo.

Some majid ("decorator") crab inside a big glass sponge..

Decorator Crab inside a Glass Sponge from Jackson Chu on Vimeo.

Tuesday, September 13, 2011

The Smithsonian-California Deep-Sea Starfish Connection! The Sunflower Star's Deep-sea cousin-Rathbunaster californicus!

Historical trivia is always kind of weird and interesting. If you know a place or an animal's scientific history well enough, its amazing the funny little coincidences and convergences that play out.

Here's a great example, inspired by a recent set of articles on one of the Smithsonian's most prominent scientist/administrators Richard Rathbun!! Part 1 and Part 2.
So, there's this deep-sea starfish that lives off the coast of California, Oregon and Washington (and by deep I mean about 130-700 meters deep, the continental shelf).

Its called Rathbunaster californicus!
Its got 12-20 arms. Gets pretty big (about a foot across) and occurs abundantly on soft bottoms, among other places. Here's some video..

Biology of this animal is pretty neat! There's a full paper by Lynn M. Lauerman (formerly of MBARI and Scripps) from 1998 in the Bulletin of Marine Science 63(3): 523-530 which outlines diet and feeding behavior of this species in Monterey.

Basically-in addition to other feeding scavenging/predatory modes, such as feeding on heart urchins (see this older post from 2009), they can also use their arms to capture SWIMMING prey!

Such as this krill
and these myctophid fish!
among other things-Rathbunaster eats?

MANY moving crustaceans (including shrimps and amphipods), swimming worms (tomopterids), and even some jellies (siphonophores)!!

SO, if there's ONE thing that I hope all of you get from reading the Echinoblog? Its that at least some STARFISH catch things that MOVE faster than them! Another example is the large, Antarctic bottom predator Labidiaster (click here and on the pic to see other examples of starfish that catch moving prey items!)
So, Rathbunaster is pretty cool, eh?? Well, guess what? THERE's MORE!!

You may have already picked up on this-

the genus name RATHBUNASTER is an honorific of Doctor Richard Rathbun of the Smithsonian!

A combination of the surname "Rathbun" and "-aster" which means "star" in Latin. The "californicus" species name refers to the place where the animal was collected.

The name literally translates to "Rathbun's California Star".
Here's a scan of the original description....

and who to name this new species (back in 1906) other than Walter K. Fisher-the famous starfish biologist and Director of Stanford University's Hopkins Marine Station-himself??
Fisher was likely grateful to Rathbun, as Fisher was actually given the "OK" by Richard Rathbun to study this species and MANY other species of the North Pacific.

Bear in mind that at the time, the marine fauna of this region was only JUST becoming known, even to scientists. And so, being THE authority on any particular fauna or group was what you did back then and the big guns got access to the best material!

Here is a quote from Fisher in the preface to his major 3 part treatise on the starfish of the North Pacific..
I had completed special reports on collections Nos. 2 and 3 when the collection from the U.S. National Museum, sent by Dr. Richard Rathbun, Assistant Secretary of the Smithsonian Institutution, was received. This is probably the largest and most complete single collection ever assembled from a restricted region (the west coast of North America). Doctor Rathbun at one time contemplated working up this material, and to that end made a preliminary sorting of specimens in several groups. He was however, prevented by routine work from carrying out his plans.
As if this wasn't enough... the study of this starfish even takes you to an intersection with the famous intertidal biologist Ed "Doc" Ricketts, the biologist made famous by John Steinbeck's novel Cannery Row!

This quote from the Fisher (1928) monograph of forcipulate starfish:
Several live specimens captured in about 300 fathoms off Santa Cruz and presented to the Hopkins Marine Station by Mr. E.F. Ricketts were kept in an aquarium for a week in water about 12 degrees higher than the 42 or 43 degrees F to which they were accustomed at their normal depth. These specimens were kept in subdued light and were fairly active. Small crabs and shrimps allowed to fall on the abactinal surface were instantly seized and held by the numerous batteries of crossed pedicellariae of the spine sheaths. In some cases,the prey was then seized by the tube-feet and carried rapidly to the mouth. In others, the victims succeeded in escaping. Doubtless in normal circumstances this species reacts as quickly and vigorously as Pycnopodia.
Well, now, that's interesting. He mentions the nearly world-famous Sunflower star Pycnopodia helianthoides!!
But sadly, only a select few know about the very similar but taxonomically distinct Rathbunaster. (sort of like Pycnopodia's lesser known sister)

Hmmmmm... They DO sort of look alike dont' they??

Fisher outlined the definition of Rathbunaster pretty thoroughly in his papers and maintained that they were unrelated and very distinct from each other. Going so far as to place them in separate families.

I've literally taken apart the skeleton of Rathbunaster and Pycnopodia and compared them. They were similar (as many multi-rayed specis are) but in many ways VERY different.

Morphology can be frustratingly vague. How were they related? How distantly? How closely? A mystery.

Flash forward to my recent DNA paper with Dave Foltz in the Zoological Journal of the Linnaean Society!

Our molecular tree shows the two, Pycnopodia and Rathbunaster as VERY closely related sister-taxa!
Shown here in the context of the immediate clade
When two taxa occur as "sister taxa" like this on a DNA tree (at this level) a number of interpretations are possible
  • They are the same. And one should be taxonomically subsumed into the other.(i.e., one name is redundant and by convention can be made obsolete by international regulation)
  • They are legitimately two separate distinct groups that might simply be very closely related.
  • We haven't sampled enough taxa and this doesn't show the full picture... yet.

Much remains to be discovered about the evolution/separation/ecology of Pycnopodia and Rathbunaster..

And so, in many ways the pendulum has swung from coast to coast.

From Richard Rathbun to Walter K. Fisher (who described) and then to me, travelling from California to Washington DC.
Any of you California/West coast DNA types ready to take on the challenge of Rathbunaster/Pycnopodia and return the pendulum to the west coast??