Tuesday, October 26, 2010

Maybe its the HEAT and not the acidity? A study of how Climate Change Affects Echinoderms!

So, there was big climate change news on the BBC website with a headline of "Sea urchins tolerate acid water" yesterday. An interesting article that showed the effects of carbon dioxide-rich water Atlantic shallow water sea urchin, Psammechinus miliaris to quote:
Whilst the scientists found no adverse effects on larval development or soft tissue production in the present study, they did observe a significant decrease in the amount of calcium carbonate that the organisms produced, resulting in smaller and thinner skeletons.
I should note that I haven't seen or had a chance to read the BBC paper as yet.. but a discussion on this topic with my colleague Dr. Allison Gong of UCSC (and who provided some Pycnopodia pix) reminded me of a paper I had seen awhile back.

Dr. Maria Byrne and her colleagues in Southern Australia published this 2009 paper with a telling title " Temperature, but not PH, comrpomises sea urchin fertilization and early development under near-future climate change scenarios".

I have previously written about how climate change may affect intertidal invertebrates here (effects on Pisaster and such)..
Byrne and colleagues studied the ecologically important sea urchin Heliocidaris erythrogramma which occurs widely throughout temperate-water Australia.

So, climate change's biggest impacts will most likely be in terms of sea-surface warming and ocean acidification. Good introductory articles on Wikipedia to global warming are here and for ocean acidification, here (short version: increased carbon dioxide creates more acidic ocean water) .
(this image from the BBC)
Echinoderms are composed of an internal calcium carbonate skeleton that is made up of millions of tiny pieces that are all infused with tissue.

As a consequence, echinoderms are one of the organisms likely to be affected by climate change because their skeletons are most likely be affected by the animal's uptake of calcium carbonate. Acidic (or warmer) water can dissolve/change/alter the chemical nature of calcium carbonate (aka chalk, limestone, etc.),

Byrne and her colleagues ran experiments that simulated future conditions of increased sea surface temperature AND an increasingly acidic ocean (i.e., a higher pH).

But rather than focus on adults, their efforts were directed at different life stages of Heliocidaris.
Namely, their larvae and the fertilized eggs.
This is actually one of the MOST important aspects of understanding the biology and evolution of marine animals. Like almost ANY animal, their "baby" stages are influenced and/or changed by the environment.

Larvae are also often WIDESPREAD. The little floating eggs and "babies" are found all throughout the water column and can be changed/affected by environment in ways that the adults can't be...
So, Byrne and her colleagues ran experiments where they changed the temperature and acidity during rearing conditions of fertilized/developing eggs of Heliocidaris.

They compared experiments versus a "control" standard was set at 20 degrees C (which is 68 degrees F) (with a PH of 8.2)

They varied environmental conditions up to 24 degrees C and 26 degrees C.

There were two experimental conditions outlining +4 and +6 degrees over the "control" temperature.

Their results are summarized in their Figure 1 below:
The top graph represents % of eggs that underwent fertilization
The middle graph represents % of normal cleaving embryos as temps increase from left to right.
The bottom represents % of normal gastrulation as temps increase from left to right.
Bar color represents the pH: black-8.2, dark grey-7.9, light grey-7.8, white-7.6 (so becoming MORE acidic from left to right)

What's Happening?

-The % of normal cell cleavage AND gastrulation (these are critical stages of cell development) were significantly LOWER. (dropping from the 65% that developed normally to LESS than 20% that developed normally!) at the warmest temperatures!
Basically, higher temperature created a BIG Developmental FAIL!!! Regardless of the pH (i.e., the acidity). Temperatures may affect various physiological processes that affect the development of the egg resulting in developmental failure!

How does this compare with other urchins?
Byrne et al. compared these results with the temperature and pH tolerances of other species and found that for five other species most of the known tolerances are only affected by a pH of LESS than 7.4 (the lowest they reached in the experiment was a pH of 7.6).
(thanks to Wikipedia for the pH scale!)

Normal seawater has a pH of about 8 (8.2 was measured for the sea urchins), and distilled water is about a pH of 7. Hydrochloric acid, what we use to digest food, is a pH of about 1.

Only the WORST CASE of ocean acidity would begin to seriously and fatally affect fertilization and development of baby sea urchins.

But it turns out that acidity on its own is a mixed bag for sea urchins (and probably other echinoderms)...

-on one hand, many sea urchins are quite tolerant to low pH (i.e., acidic conditions) owing to the relative acidity associated with fertilization. Sea urchin sperm actually has a pH of about 7.6!!

Indeed..some studies (such as this one by Wood et al. ) have shown that some echinoderms, such as brittle stars will actually show increased growth under acidic conditons!

-BUT on the other hand, decreased pH may have a negative effect on larval calcification i.e, the ability to use calcium carbonate to develop their endoskeletons after sea urchins undergo early development. Animals could be weaker or have weaker "bones" as adults.

In the here and now- temperature is an important consideration!
Projections for eastern Australia indicate a surface sea temperature warming of UP TO 2 to 4 degrees C in the summer off the coast of New South Wales. Resulting in water temperatures of UP to and above 26 degrees C-Close to the temps indicated in their experiments!

And all this IN ADDITION to whatever possible stress may be caused by acidification!

So, while reports such as the one reported by the BBC are important, perhaps temperature will be the more important consideration in future studies???

Increased temperature appears to be one of the most important factors impacting many facets of the biology of adult echinoderms (and indeed-many other marine invertebrates) , including distribution, feeding, behavior, reproduction...but most importantly, the development and healthy survival of fertilized eggs and juveniles.

Wednesday, October 20, 2010

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

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

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

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

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

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

Discovering New Deep-Sea Coral Eating Starfish!

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Monday, October 11, 2010

Counting Currents with Crinoids! Using Feather Stars as a Natural Flow Meter!

Today, a new installment of "Echinoderms? What are they good for?"

This is based on a paper by my crinoid colleagues in Paris: Marc Eleaume, Nadia Ameziane, Lenaig Hemery and others..in Deep-Sea Research!

Crinoids, aka Feather Stars, are echinoderms that are filter feeders-they capture food from passing water currents.
These animals are structurally pretty simple- a cup with a mouth and guts which sit at the base of a bunch of arms. Each of these have tube feet that help capture food and move it down to the mouth.

Where does this food come from? Water currents bring tasty organic bits or what-have-you...

Crinoids hold their arms up into the water to capture food particles...but often they do so at different angles and positions relative to the flow of water... like so..
(From Echinoblog Art Department!)

The feeding "fan" created by crinoids is thus, consistently at a specific orientation (in this case perpendicular) as the current flows "downstream".

So, it turns out there's actually a USE for observing these animals when they FEED!

What if you could use the crinoid's orientation to actually determine what DIRECTION the current was flowing?

Eleaume and his colleagues took video footage from the 2007-2008 R/V Aurora Australis cruise operated by the Australian Antarctic Division, looking at 66 video transects of the bottom (each about 17 minutes long) in East Antarctica around Terre Adelie and the George V shelf. !!

While that may not sound like much, here's an example of what that video is kinda like...

Eleaume and his crew identified the number of crinoids, their position and feeding orientation.

There were four species of crinoids identified (Promachocrinus kerguelenensis, Anthometra adriani, Flormetra mawsoni, and Notocrinus virilis) all of which were abundant in the area being studied.
Based on these 66 transects, they collected a total of 1537 observations which were subsequently analyzed!!

The orientations of crinoids along each transect looked like this:

Each individual arrow above indicates an individual crinoid's orientation in the current across a transect.

The multitude of individual arrows were analyzed with Natural Neighbor Interpolation, which is part of the ArcGIS program Spatial Analyst.

The top figure below is a map that shows depth as indicated by color and gives you a general idea of the region and local topography.

This lower picture with all the arrows is essentially the combined data points that show the overall orientation and near-bottom-current flow of all the crinoids mapped onto the same area.

Eleaume et al. found that based on an interpolation of all the 1537 observations of crinoid feeding fans, there was an EASTWARD near-bottom current flow, becoming southestward over the Adelie Bank..

The authors were able to combine this plus other information to actually reconstruct a model of near-bottom current direction throughout the area. Crinoids showed dependable current directionality throughout the range studied!

What are Near-Bottom Currents Used for?
Basically, this is a very clever way to use animal observations to obtain what's called oceanographic or hydrographic data. This is useful for a variety of reasons.

Near Bottom Currents (NBCs) are important because they give us insight into where larval animals/organisms (and eventually ADULT animals and/or organisms) will be dispersed and thus how they can be present throughout their range.

This can have important repurcussions for everything from invasive species to determining how climate change can affect where some species "settle out" when they become adults.
(yes, I know its not a crinoid larvae-its just to illustrate a point)

It occurred to me as well, that something like this would also be useful for reconstructing the paleoecology of crinoids, provided there was good enough preservation and all of the individual fossils were preserved in "life mode"...

Thursday, October 7, 2010

Japanese deep-sea cuke poops! then Flies! Sand Dollars eating! Sea Urchin Escape Artist!

and what would Thursday be without a new vid of a deep-sea swimming sea cucumber pooping and then taking off!

and from the same Youtube channel.. a sea urchin escape artist!

This Japanese sand dollar (Astriclypeus manni, I think..)eats uh...something that is probably shrimp meat...

and these aren't echinoderm videos..but wow! If you enjoy the Echinoblog-these will appeal to you..

Octopus escapes from Jar!

When Giant deep-sea Isopods ATTACK!

and the BEST for last! You have probably NEVER seen this. Giant frakkin foraminifera and their pseudopods movin around' in time lapse!