Tuesday, April 29, 2008

In Honor of Coral Week: Echinoderms Eating Corals! Mmmmmm...

(from Wikipedia commons)

My esteemed colleagues over at Deep-Sea News have declared this week (April 27-May 3) "Coral Week" and have gone into insane 100% coral-all-the-time mode.

So at Dr. McClain's delicate urging I thought I would present a little somethin' somethin' on the echinoderm-coral intersection.

One aspect I should mention of course, is that coral reefs-both deep and shallow provide habitats for echinoderms. Here...I look at more direct interactions..and interesting aspects of those relationships....

Sea Cucumbers (Class Holothuroidea) & Crinoids (Class Crinoidea): As far as I know, sea cucumbers and crinoids don't really interact directly with corals other than as substrate or when they form habitats (as in tropical shall0w-water or deep-sea coral reefs). And if you don't believe me about cukes not eating corals..ask Dr. Seville Kent from 1883 (note: this made Nature in the 19th Century!!). So, not much on those groups here.

Brittle Stars & Serpent Stars (Class Ophiuroidea):
There are quite a few ophiuroids that live on various corals. My understanding is that relationships are generally commensal, with the ophiuroid living in or around the coral (and/or sometimes sponges). Both in tropical shallow-water and deep-sea habitats. Examples include:

* The six rayed Ophiothela danae from tropical shallow-water habitats

* Several deep-sea "serpent stars"(Phrynophiurida) i.e., those with big fleshy arms that split into massively branched arms such as this that often live on octocoral hosts.

*The Ophiacanthidae-a weird but diverse group of globally distributed spiny brittle stars). Shown here co-occurring with some deep-sea coral.

Ophiuroid-octocoral relationships are quite interesting. And various aspects of this research are being studied, including
systematic relationships
sublethal predation
and other aspects of feeding ecology and reproduction.

Perhaps though, one of the most significant relationship between echinoderms and corals is that several echinoderms EAT coral!!

Let's take a look at some prominent corallivorous echinoderms, shall we?



Diadema antillarum (class Echinoidea-sea urchins)

(images courtesy of Flickr)
One of the few non-starfish echinoderms reported to feed on coral..Diadema is a member of the family Diadematidae, which are recognized by their long sharp, needle-like spines.

Diadematids are widespread throughout the tropical Atlantic and Indo-Pacific occuring primarily in shallow-water reef habitats with some deeper members.

Diadema is primarily an epifaunal algal grazer, leaving scar marks on substratum with relatively minimal corallivorous propensities.

What's curious is that much of the review literature (citations available upon request) attributes coral as a food source, when it may actually be that much of the perceived "feeding" is in fact, grazing.

Only one paper-Bak & Eys 1975 reported feeding in D. antillarum with gut content reports but reported "scars" from coral heads as well as various outlining various prey species but that doesn't really convince me that feeding on coral polyps was not merely incidental.

Bah. onward to some REAL corallivores....


Hippasteria spp. (Goniasteridae)

Hippasteria (and the related genera Evopolosoma and Cryptopeltaster) are large, heavily calcified starfish with big thick spines that live primarily in cold-water areas, in other words the polar/sub-polar or deep-sea settings.

There are about 25-30 species with members occuring in the Arctic, New Zealand, Hawaii & Japan (deep-sea), the North Atlantic, the tropical West & South Atlantic (deep-sea) and throughout the North Pacific.

Krieger & Wing 2004
reported from their Alaskan/North Pacific study areas that in some of their study areas, Hippasteria spp. accounted for up to 45% of polyp predation on the soft-coral Primnoa. The North Pacific Hippasteria spinosa was reported by Birkeland 1974 to feed primarily on sea pens.

and without getting into too much detail, I've seen these feeding on deep-sea corals suggesting that when present, they are probably important members of deep-sea coral systems. What role and how important they are to those systems remains an open question....


Culcita novaeguineae (Oreasteridae)

(images courtesy of Flickr)
A widespread genus with three species occuring throughout the tropical Indo-Pacific region. From Hawaii to India and the east coast of Africa. Varies widely in color and morphology but maintains its distintinctive swollen appearance. The name, Culcita, is latin for "cushion".

Various factoids taken from Glynn & Krupp 1982:
  • Culcita prefers feeding on Pocillopora over Porites, Montipora, and Fungia
  • Based on lab feeding results, Culcita can eat 1.0 square meter per year of Pocillopora or 0.9 square meters of mixed coral prey. This represents ONE FIFTH of the feeding rate of Acanthaster planci (see below) which is about 6 square meters a year.
  • Abundance of Culcita is also FAR below what Acanthaster reaches.. Culcita was reported in one instance approaching 25 individuals per hectare vs. 65 individuals per hectre for Acanthaster. Based on this, it seems doubtful that Culctia could have a deleterious effect on reef growth.
  • HOWEVER, Culcita seems to feed primarily on younger colonies and thus, could have an effect on coral community structure by limiting abundance of one species over another in different areas and in conjunction with Acanthaster could affect coral population structure.

Acanthaster planci
(Acanthasteridae)

(courtesy of Flickr)

aka the Crown of Thorns Starfish or...COTS by some. The BIG one. A caveat here..this is a SHORT summary. Based on the amount of literature available on this animal, I could literally spend a whole frackin' WEEK just on the COTS.

Pursued, studied, and in many cases destroyed due to their perceived threat to shallow-water tropical reefs. Probably one of the most notorious, and as a consequence one of the best-studied, starfish in the world.

The COTS is widespread, occuring from Hawaii and southern Japan to the Pacific coast of Panama to the Indian Ocean on the east coast of Africa and as far south as the subtropical Kermadec Islands. Acanthaster varies widely over this range in color and morphology.

A whole book is devoted to the biology and ecology of Acanthaster planci. Much of my info here hails from this useful volume.

Two important aspects of COTS biology contribute to human concerns:

Acanthaster is a voracious predator of corals

Individual animals can ingest up to 6 square meters of living reef a year.

Acanthaster has undergone huge bursts in population (known as "outbreaks")
Accounts of
these outbreaks have been estimated based on relative size based on catch records.
One study collected 8,083 individuals from American Samoa but surveys estimated that the total population to be 212,000 individuals!! (that's 26.5X as large!!)

Another study from American Samoa collected 486,933 but "so many thousand remained that no estimate was made of the proportions killed"

Interestingly, abundance can fluctuate by as many as six orders of magnitude within a year or two.
For example:
Prior to late 1977, numbers of A. planci in American Samoa were of the order of less than 2 per year, as observed by "knowledgeable persons". By late 1977, HUNDREDS of THOUSANDS of starfish appeared on both sides of the main island!!!

These two issues combined have resulted in a LOT of COTS devouring coral and leaving dead white rubble in their wake...

So why the outbreaks? Different hypotheses have been advanced (I will caveat that there are probably others but these seem to be some of the two most prominent):
  • The outbreaks are natural. Analysis of Acanthaster ossicles (i.e., fossil remains) were analysed and showed regular fluctuations.
  • Outbreaks are caused or directed by anthropogenic (i.e., man-made) forces. For example, increased nutrient run-off from land resulting in higher juvenile survivorship and thus greater adults. An older idea, that overfishing of giant "trumpet shell" snails (Charonia) resulting in loss of natural predators has essentially been discounted as the sole cause.
Other links of interest:
Long Term outbreak monitoring on the Great Barrier Reef can be read-about here

Controlling Crown of Thorns Starfish

Monday, April 28, 2008

Echinoderm Big Battle! Sea Urchins Feeding on Stalked Crinoids!!

(Courtesy of C. Messing)
So, the other day, I was giving a tour and making the point that as much as the scientific method is a critical part of our analytical process, an important part of science is primary exploration and discovery. Something people seem to forget amidst busy times.

New facts or observations (some would say qualitative data-others would say "natural history") can inspire many new questions and a diverse array of hypothesis-driven studies. A simple observation can drive a host of inquiries!!

A case in point? Let's look a very interesting recent paper by Baumiller, Mooi & Messing 2008 which documents an observation that has repercussions for paleoecology, paleobiology, and broad evolutionary dynamics.

The Players:
The cidaroid sea urchin-Calocidaris micans. Cidaroid sea urchins are considered among the oldest and some would say more "primitive" within the class Echinoidea (Another way to say this is that cidaroids are sister taxa to modern echinoids).
Fossil occurrence for cidaroid sea urchins extends back to thePaleozoic (approximately 251-542 Millions of Years Ago). Today most cidaroid sea urchins live in deep-sea habitats and can be quite abundant.

Cidaroids are unusual in having an specific kind of Aristotle's Lantern and in lacking skin on their blunt, thick spines. Most sea urchins (and in fact, most echinoderms) have skin covering their entire body.
This species occurs in the tropical Western Atlantic, specifically in the Bahamas.
(Image courtesy of Dave Pawson, NMNH)
The stalked isocrinid crinoid Endoxocrinus parrae. I've already said a few things about stalked crinoids. When they are observed in nature, they can also be very abundant occurring in "meadows" numbering in the hundreds! (as seen above) Creating an alien seascape, very few people get to see in person...
(Courtesy of C. Messing)
Bear in mind, that often, deep-sea invertebrates like this, very rarely if EVER get to be observed in the wild. So our knowledge of their life habits is negligible.

Getting to the Point:
Based on observations from the Johnson Sea Link submersible the authors watched Calocidaris FEEDING on Endoxocrinus!!!!

A sea urchin chewing on a stalked crinoid! An interaction never before observed between these two kinds of animals!
Ramifications?? Well, for one thing it might explain the recent observation that stalked crinoids CAN MOVE (i.e., escape!)


Also: stalked crinoids have been known to shed distal segments of their stalk..but up until now the explanation for that behavior was a mystery.

Think of a "lizard's tail" strategy. Stalked crinoids will jettison parts of their stalk to distract the predator allowing the surviving part of the animal to escape!!

Implications & Questions?? Many.


  • Did Paleozoic cidaroids feed on Paleozoic stalked crinoids in the same way?
  • How many other cidaroids feed on other stalked crinoid taxa?
  • Could predation by slower benthic predators have affected the evolution of stalked crinoids and their morphology? 

Finally, one of their most intriguing notions: Swimming in stalked crinoids (below) has been argued in the past as an escape/defense mechanism against predatory fish.

But "Doesn't a slow-moving, kind of clumsy looking swimming thing in the water column really just seem to INCREASE the chance that a fish would eat it??"


What if it was a defense mechanism against other SLOW benthic predators??? Sea urchins, starfish and...????? Think of the scallop using a jet blast to propel itself out of harms way when a starfish attacks.

One observation.

With implications for over 500 Mya of evolution and ecological interaction.

Science!

Thursday, April 24, 2008

Crinoid Crazy!! Let's Meet Holopus!

Today we feature the strangest of a strange and wonderous lineage of creatures- The Crinoidea!!

Crinoids are suspension-feeding animals that capture food with their tube feet as water flows through their multi-branched arms.

Crinoids are considered basal to the other living Echinodermata (i.e, they are the most "primitive" and show closer relationship to older extinct echinoderms).

Today, most crinoids occur as one of two forms. The more basal or "primitive" of modern crinoids are those with a stalk. These can be seen as fossils (
many from the Paleozoic) or living today, mostly in the deep-sea. They can move (this is the subject of a post next week) but generally do not. They look like this:

(photo by David Clague, MBARI)

Modern crinoids occur primarily as unstalked forms, aka "feather stars"-the Comatulida, that can occur in the deep-sea but also in tropical shallow-water habitats. They are mobile and can be very brightly colored.

(courtesy of Flickr)

but then, there's THESE weirdos.

(from Chuck Messing's crinoid site)

These are weird beasties in the family HOLOPODIDAE (Cyrtocrinida) that are kind of an odd intermediate form. They live in the deep-sea (~100-900 m)and lack a full stalk, with five stout and stocky arms (other crinoids can have many more) but are cemented permanently to the substratum.

A new paper by Donovan & Pawson 2008 describes a new species in the genus Holopus from the tropical Western Atlantic. Their new species, Holopus mikihe is described from a single distinctive specimen with very prominent tubercular ridges on each arm as seen here:
(photo courtesy of Dave Pawson NMNH)

Based on observations from the Florida based submersible the Johnson Sea Link, (operated by Harbor Branch Oceanographic Institute (HBOI) in Ft. Pierce, Florida) several interesting observations of the tropical Atlantic species, Holopus rangii were made:

*H. rangii lives upside down on rocky overhangs.

*Arms seldom open, but when they did, they formed a funnel-like array, taking 0.8 to 1.0 seconds in response to stimuli (either the bow wave or possibly the lights from the submersible). As a model think of it as a living crinoid fist! Opening and then closing!

*It has been suggested that these things feed on active prey!! (as opposed to most crinoids that passively pick food out of the water)

OPEN
(photo courtesy of Dave Pawson NMNH)

and CLOSED!!!

(photo courtesy of Dave Pawson NMNH)


WARNING: COMPLICATED SCIENTIFIC SIMULATION OF HOLOPODID FEEDING MECHANISM (hypothetical!!) TO FOLLOW:


CHOMP!!!

Mmmm...yummy, yummy.....

Tuesday, April 22, 2008

Three of a Kind: What?? They're all the SAME??

Well..no, not quite but,

DID YOU KNOW:
That THIS:

Colobocentrotus atratus
THIS...


Echinometra sp.
AND THIS...

Heterocentrotus mammilatus

ALL members of the SAME Family!! (i.e., the same group)-the
ECHINOMETRIDAE

Weird, huh??

Monday, April 21, 2008

Holding on in a Rough World: Colobocentrotus atratus-the Shingle Urchin!!

Today's we shift gears from starfish and take a look at sea urchins! Today we look at Colobocentrotus atratus (Echinometridae), a commonly encountered resident of the South and Central Pacific rocky intertidal. If you've ever been to Hawaii they can be frequently encountered along the edge of the harsh-wave swept habitats along its beautiful volcanic shores.
They are commonly known as the Shingle or Helmet Urchin and in Hawaiian is known as kaupali which translates to "cliff-clinging"... (thanks to John Hoover's Hawaii's Sea Creatures for this info)
Notice the uniquely flattened shingle-like mosaic of modified plates covering the surface as well as the flange of flattened spines forming a close fringe around the edge.

Colobocentrotus lives in heavy wave-swept environments and its smooth, flattened plates lead one to automatically interpret them to be adaptations for surviving in these kind of environments.

A recent paper by Santos & Flammang (2007) investigates the biomechanics of how these neat beasties hold on.

It turns out..its ALL in the TUBE FEET!



They measured the adhesion of this species against other more "normal" sea urchins (e.g., the spiny Echinometra) and they found that Colobocentrotus always presented the highest measured values.

* Colobocentrotus' attachment force allowed it to resist dislodgment up to water velocities of 17.5 m/s and even up to 27.5 m/s!!! In contrast, more "typical" echinoids, like Echinometra were disodged by water velocities superior to 7.5 m/s.

How fast is 27.5 m/s??

.....basically if this was compared with a strong windy gale..that would be enough to uproot trees and cause minor damage to buildings!!! Holy Carp!! (and according to Patrick, given the density of seawater, wave strength would actually make it WORSE!)

* The shape does not appear to affect the difference in drag and lift but may function to offset the amount of shear force directed onto the animal into normal force..effectively spreading the energy load around more evenly on all tube feet.

Thus, it seems that the ability to inhabit extreme water velocities in Colobocentrotus is tied to its very high number of tube feet and not to its particular morphology (although it does seem to help in other ways).

Adaptive notions for the overall shape suggest several ideas, including:

1. The streamlined morphology might be an adaptation to lessen other hydrodynamic forces such as wave impact.

2. The flattened spines may reduce spine breakage and therefore the energy expense of constant repair, etc.

3. The morphology seems ideal for retaining extra water which can be essential to resist heat and dessication stress at low tide.

This latter idea seems interesting given this pic of Colobocentrotus huddled together....


Tough little wee beasties...so for goodness sakes! leave em' alone when you go out tide pooling!

(Photos courtesy of Flickr and Photobucket!)

Friday, April 18, 2008

Taxonomic Update!! Pawsonaster parvus

I thought it might be an interesting notion to make announcements regarding recent taxonomic changes made from the literature aimed at people who are not reading fastidiously The Systematic Journal of....... (or whatever) every passing moment of the day...

 Here..we have an attractive deep-sea goniasterid starfish from the tropical Atlantic/Gulf of Mexico, formerly known from as Tosia parva (as seen in Starfishes of the Atlantic by Clark & Downey 1992) and originally described as Pentagonaster parvus by Edmond Perrier in 1881.

A recent paper by Mah 2006 using a phylogeny based on morphological data separates this beast from the Indo-Pacific members of the Australian genus Tosia and establishes it within a new genus named for Dr. David Pawson, curator of echinoderms at the Smithsonian in honor of his contribution to our knowledge of deep-sea echinoderms from the tropical Atlantic!

Wednesday, April 16, 2008

People Eating Starfish

No..not starfish that eat people, but the other way around...

I was sent one of the two videos below. Many have perhaps seen fried starfish on a stick in various Asian seafood marketplace pictures, such as this one:

starfish kabob

Okay, first. Yuck.

Taxonomy: From the video and from various pictures floating around on the internet, the species looks like Asterias amurensis, the North Pacific species of the well-known asteriid Asterias, which includes your well-known experimental lab rat Asterias rubens, etc.

Details: In addition to the video and pictures floating around on the internet, I have encountered two anecdotal accounts including:

*I have two packages of a starfish soup mix from Asia that apparently use the starfish as a component you add to dried fungus and boiling water.

*There were rumors when I visited New Zealand that people were using tube feet as part of clam dip.

Good Reasons why I would AVOID eating starfish:

*
There's no meat. Mostly calcite. (Interestingly though, a note in one of the Youtube videos suggests that one eats the gonads or soft parts.)

* Body walls, of many, if not all asteroids are laden with toxic biochemicals, from saponins to tetrodotoxins. Many accounts report that feeding starfish to dogs or cats results in vomiting and the subsequent death of those animals.

* Some accounts-especially from Asia, such as this one, show that that some species which digest bivalves (e.g., Asterias amurensis, Astropecten scoparius, Asterina pectinifera) can actually convey paralytic shellfish poisoning.

*And finally.. Eww...





Monday, April 14, 2008

A Day In the Life: Echinoderm Forensics

Today, a little bit of sharing about my professional life and a story about helping people with my taxonomic expertise.

Among the the skills I've found most useful (and necessary) in my profession is my skill in taxonomy-identification, classification, and all of the associated history which accompanies the knowledge about a specific group of organisms. In my case, the starfishes. Class Asteroidea in the phylum Echinodermata.

I am often consulted by a wide array of agencies, professionals, and interested persons to identify their animals from a wide variety of sources. Some from specimens, some from videos, and frequently from pictures.

Last week, I received an unusual request from a veterinarian via a colleague of mine (excerpt in part):

He had a case of a pet boxer that consumed a dried ornamental starfish,
proceeded to vomit and exhibit sustained seizures, and despite aggressive
supportive therapy over the course of about 18 hr, failed to improve and
was euthanized. They managed to remove one large chunk of the starfish
by stomach pumping, but radiographs showed that much of it remained in
the stomach. Surgery to remove the chunks would have been the next step
if it had not been euthanized. The dog was cremated without necropsy,
so the only sample that remains is the 2-arm chunk of starfish that was
removed by the stomach pumping. They are interested in determining whether or not the starfish was actually the culprit in causing the seizures.

While treating the dog they called some poison control centers and learned that some starfish can carry tetrodotoxin, and I see from some quick web searching that that is indeed the case, so it is plausible. Starfish poisoning wasn't covered in my veterinary toxicology course for some

reason. I figure the first logical step is to identify the species, then
see if we can find a marine biotoxins lab that might be willing to assay
the starfish tissues for tetrodotoxin and/or harmful algal bloom toxin

I suspect humans and terrestrial mammals very rarely consume starfish,
so there is probably not much opportunity to observe whether or not there
is associated toxicity. Unfortunately, with the prompt cremation, there is
no way to determine what else may or may not have been associated with the seizures. I have no idea what the stability of tetrodotoxin or other marine biotoxins is, but drying might not be too harsh on them. I also don't know if there might have been a preservative of some sort applied to the starfish that could be responsible, rather than the starfish itself, but I think they can just be dried, and it doesn't look like there's any shellac or painting on it. Can you identify it from the attached images? and if not would the identification be possible with the actual specimen in hand?

Thanks for any assistance you can provide.
Best regards,
Along with these pictures:





Most of my requests for identification are biodiversity related-so it was unusual to get one with a chewed-up, half-digested specimen and involved with a canine death no less!

I have over 10 years of experience with identifying starfish..and even so, its not easy to ID a species from pictures of fragments- but I got it: Pentaster obtusatus. A commonly encountered Indo-Pacific oreasterid that often makes its way into shell and curio shops.
Exp.105
Image by Kee Alfian

Unfortunately, it was chewed up and swallowed by this dog. Many starfish contain saponins and other toxic biochemicals in their body walls..likely as a defense against predatory vertebrates. And much of the older toxicological studies "back in the day" report dogs and cats inadvertently eating starfish, such as this one, exhibiting similar symptoms, followed by death.
I was able to quickly report to the inquiring veterinarian about the likely nature of the cause of fatality and its toxicology.

There were certainly several unanswered questions here...but knowing the name of this poor beastie was an important fact in this case and I was happy to provide an answer that helped figure it out.

Friday, April 11, 2008

Weekend Sea Urchin Pic

The Cherry Blossom festival is in Washington DC this weekend and the cherry blossoms are in bloom

Photobucket

making me think of this....

Sea Urchin

Yeah. I'm a weirdo.

(courtesy of Photobucket)

Thursday, April 10, 2008

Blastoids from Belgium-the Music Video!

Just to show right off the bat that I'm not biased against the Paleozoic..here is a terrific Youtube MUSIC video about a Class of Paleozoic echinoderms..the Blastoidea

And REALLY..how often do you get people creating great folksy tunes about Paleozoic fossils?

Enjoy!

Massive Starfish Die-off along the Kent (UK) coast

(image from the Times Online)

Various news sources, including the Times Online and the BBC have reported massive die-0ffs of the common European Asterias rubens (Asteriidae, Forcipulatida) along the east Kent coast numbering in the thousands of individuals.

Several multi-tiered explanations have been offered, including

*killed by fisherman dredging the bottom for shellfish

*being dislodged and rendered ashore by extreme storms and high tides.

Sources indicated in the Times article speculated that the die-off wouldn't even "dent" the population. (which sounds reasonable given how prolific Asterias can be....)

I've seen Pisaster mass die-offs in California following storms..but never to this degree. Seeing that many dead starfish seems sad...

Wednesday, April 9, 2008

Welcome to the Echinoblog!!

(my thanks to John Lawrence for the image)
Greetings!

The Echinoblog will be an ongoing venue for collecting and presenting perspectives, popular news, and articles on the Echinodermata! Echinoderms are a phylum of exclusively marine animals, that are familiar to almost anyone who has heard of the ocean.


The group’s living members include starfish (Asteroidea), brittle and serpent stars (Ophiuroidea), sea urchins, sand dollars, and sea biscuits (Echinoidea), feather stars and stone lilies (Crinoidea), and sea cucumbers (Holothurians). Tired of modern echinoderms? There are easily two to three times as many major Paleozoic echinoderm groups. Many of which are strange and unusual forms that one could easily mistake for extraterrestrial life on another ocean!

What I hope to include:

*Short articles on various aspects of echinoderm biology that highlight various taxa and topics of interest.

*Collected popular news articles featuring different echinoderm taxa.

*New developments in the professional field of echinoderm biology highlighting as many different disciplines as possible: paleontology, conservation, systematics, deep-sea biology, ecology, reproduction, etc.

*Unusual or striking images and/or websites


*Contemporary issues or questions to the echinoderm (and related professional) community


*Anything that seems of general interest.


I hope to update multiple times throughout the week-sometimes shorter, sometimes longer.

I am happy to entertain contributions if you have something to say about your research project or announcement for an event, or whatever.

Please feel free to comment or email me! I'd love to hear from you.

The Echinoblog! Coming soon!