Monday, January 31, 2011

The Lost World: The biology of echinoderm "living fossils" (stalked crinoids) on an Antarctic Seamount!!

Dinosaurs Living in Underground Caves! Pre-historic Monsters Living in the Deep Sea!

This is what we envision whenever the term "living fossil" gets brought up!
At this exact moment, a whole bunch of paleontologists' heads are exploding BECAUSE I've used the term "living fossil". (BABOOM!) Why?

The term basically refers to any organism that physically RESEMBLES an organism that we know primarily as a fossil. So, examples would be..the coelocanth, lungfish, nautilus, ginko trees, and tuataras.
These types of organisms (and not just animals) are often abundant or at least, prominent in the fossil record but are really not too common today..

Why does this cause such ire in people who study fossils? Well, I would say that its inaccurate and hard to define. Technically EVERYTHING alive is a "living fossil". Its an ambiguous term at best. And the "good examples" are largely biased by public perception of the most frequently encountered fossil types. So, really the term doesn't mean anything! And yet the term persists...

THAT said.. people (including scientists) continue to have a fascination with "archaic" forms, which continue to live in the "recent" and the ecology that said forms exhibit.

It is through observation of how these modern analogs of extinct fossil animals interact that we hope to gain insight into ecosystems into the past. A romantic might almost say that these provide us with kind of a "window to the past"....

This is the subject of this week's blog.. A NEW paper by David Bowden and associated researchers at New Zealand's foremost oceanographic agency-NIWA (New Zealand Institute of Water and Atmosphere) focusing on "Archaic crinoid-dominated assemblages on an Antarctic Seamount) in the new issue of Deep-Sea Research II.

Stalked crinoids of course, are one of the most prominent of echinoderm "living fossils" and are the ancestors of the smaller feather stars seen today in tropical habitats. The relationship between the two can be seen in this past blog...
The paper features video captured by NIWA's towed video array operated by the R/V Tangaroa
From this area... (in the box). This includes Admiralty Seamount and several other seamounts and islands just north of the Ross Sea.
And it is on Admiralty Seamount that they see a substantial population of a NEW species of a large (~50 cm tall!) stalked crinoid !! (Family Hyocrinidae)

Note that hyocrinids, unlike other stalked crinoids are permanently attached to the bottom.
Out of a total seabed area of approximately 11,300 square meters..they observed 1,348 crinoids!
(images courtesy of David Bowden, NIWA)

Admiralty Seamount is apparently QUITE the hangout for the filter-feeding set. Also seen on the seamount in large densities is the large suspension feeding ophiuuroid Ophiocamax gigas...
(image courtesy of David Bowden, NIWA)

Among some of the more interesting interactions... one of this crinoid being devoured by Porania antarctica
(image courtesy of David Bowden, NIWA)

This is kind of interesting to me..because poraniids have one of the oldest fossil records of modern asteroids. A Triassic fossil poraniid (click here) was described here.

and here we see the sea urchin Sterechinus antarcticus also apparently munching on a crinoid.
(image courtesy of David Bowden, NIWA)

Sea urchins attacking stalked crinoids?? We've discussed that relationship here and here with regards to cidaroid sea urchins versus stalked crinoids in the deep-sea..

So, among the first observations is that with the crinoids and their echinoderm predators, we see a conspicuous LACK of big crab and fish predators. This suggests that it is a "Paleozoic Style" Ecosystem as proposed by Rich Aronson, Dan Blake and others which is present in the Antarctic.

This is an ecosystem dominated by suspension/filter feeders, particularly invertebrates. Certain types of predators, such as crabs and fishes, which are able to crush bony parts were absent-and so many MORE types of invertebrates flourished without being devoured.

This type of ecosystem occurs throughout geologic history wherever and whenever certain types of predators are absent.

One such ecosystem that included suspension feeding ophiuroids and crinoids similar to the ones on Admiralty Seamount was thought to have been present about 65 to 56 million years ago (the Palaeocene) but which again, ended due to a radiation of fishes and crustaceans around that time. Dang fishes and crabs!
How did this particular assemblage of crinoids and associated suspension feeders (without predators) originate?

Physical oceanography may be the key, as several factors (including current and food) influence how the different taxa are transported onto the seamount. As it turns out, Admiralty Seamount is close to the center of a nearby ocean gyre,

(Figure 7B from Bowden et al., 2011)

The seamount's location may be influenced by a confluence of the gyre, plus cold currents from the Ross Sea region, which likely reduces the chances of larvae (small baby forms of marine animals) arriving at the seamount from the "source populations" near shore.

And both of the species above have floating larvae that disperse via ocean currents..
(photo by Allison Gong. Not from Porania nor from an Antarctic species..its just here to help demonstrate a point.)

It may be the location of the seamount under the center of this gyre and the interaction of currents from the Ross Sea shelf that prevent the larvae of predators, such as crabs, from settling and growing out as well as ensuring the preferential settlement of suspension feeding critters like crinoids and ophiuroids.

Thus, it may be the seamount's location (which effectively isolates the crinoids and ophiuroids from predators like crabs and fish) acts as a sort of "refuge" where this "Paleozoic style" ecosystem can continue to persist!

So, how long have these crinoids been around Admiralty Seamount? Some intriguing clues present themselves.

Remember how I said that hyocrinids were anchored? Their holdfasts and attachment points are found all over the sea bottom and are the remants of past animals which have died. (these are the tiny white circles on the rock).
The authors speculate that based on the accumulation of sediments formed from crinoid body parts (ossicles) in conjunction with a conservative age per generation of about 20 years, this alone suggests that the crinoids here may have "persisted for centuries...if not millennia."

Sadly, all good things must come to an end...

The authors also note that the area of seabed at Admiralty Seamount covered by sediments formed by crinoids and these basal disks is much greater than that covered by living animals.

This, in conjunction with the observed predation-the authors speculate that the crinoid population here may already be on its way out... Talk about a gentrified neighborhood!

Tuesday, January 25, 2011

Secrets of the Starfish Sieve Plate & Madreporite Mysteries? aka What is that little circle on top??

I'm back and refreshed with new Echinoblog Stuffs for 2011!! While I was away-I answered some random starfish questions for you interested Echinoblog of them asked a question I never really thought to answer! So here it is made into a blog!

What is that weird offset circle (or patch?) that you see on the surface of a starfish?? (see the pic below in the red circle!)
(image from Wikipedia commons)
This funny-looking, little offset patch/circle/whatever is called the madreporite or sieve plate. As you can see, it is composed of a bunch of grooves which are each, in turn part of a porous calcium carbonate plate covered with pores. The word "madreporite" is named for its resemblance to a genus of hard coral called Madrepora whose surface is covered by numerous small openings. As we'll see there are numerous small openings (i.e., pores) that cover the surface of the madreporite as well.

So, What does the Madreporite DO anyway??

So ALL sea stars have a madreporite. We can see how it varies among different taxa, including something as different as the asteriid Asterias above and the goniasterid Eknomiaster below...

Not only do all sea stars have a madreporite, but ALL echinoderms do as well. In some sea stars there are even multiple madreporites!Sea stars (and other echinoderms) have a unique circulatory system that basically processes and circulates sea water throughout the animal's body. Imagine if your body was basically just OPEN to sea water and funneled through a bunch of tubes that make your tube feet and stomach work.

That's basically how starfish (and their relatives) get around and hold themselves up. Other than the calcium carbonate endoskeleton in echinoderms-the only other thing that holds them up?? Water pressure.

Basically, the softer the skeleton, the more dependent the animal is on its surroundings to hold up its body. And indeed, there seems to be a consistent pattern between high osmotic pressure and relative softness of the body wall.. (observed here)

But even an open system like this needs to have an intake valve to process water for the animal's basic bodily functions-like movement and internal circulation and etc... That is what the madreporite is for..
(from Leptasterias on Walla Walla!)

Based on a series of really neat experiments using small fluorescent microbeads, much of the fundamental physiology of how the madreporite and its relationship to the Water Vascular system was worked on in a series of papers by a physiologist named John C. Ferguson including
this one. and this one.

He basically introduced the dye/microbeads into the water around each subject starfish and watched the green show up wherever the water took it!
Based on the water flow, the whole thin works like this:

One important thing to remember is that ALL of this is covered by a thin skin or epithelium, which is in turn covered by countless numbers of tiny, beating hair-like structures known as cilia. These are constantly beating and moving, thus creating a current (yes-INSIDE the animal's body cavity) !!!

Water enters into the madreporite via the beating of the cilia into the various pores and enters channels into the body. Water moves along the canal connected to the madreporite and enters into the circular or RADIAL canal present in the disk. Water is then further propelled throughout the body to the water vascular system, which supports the tube feet, permitting the animal some movement!

(diagram modified from Chia & Koss, 1994. Microscopic Anatomy of the Invertebrates-Echinodermata)

Now, water can get into the body through a variety of different openings (and all of these help support the body cavity), but SOME of the water that enters through the madreporite is actually PROCESSED by small little pockets on the main ring called Tiedemann's bodies.

It turns out that small amoeba like cells and other substances are secreted into the seawater as it processes through the Tiedemann's bodies and throughout several different pockets on the central water vascular system ring. The amoebae like cells proceed throughout the body to take care of various body functions.

All the time, the tiny cilia (hair-like structures) are just beating away..moving water currents throughout the body.

Water continues to move and some of it eventually makes it into the radial canals (which branch off the central ring) and into the arms and tube feet. So, water processing through the body does eventually reach the "bottom" where the tube feet emerge from the skeleton!! This ultimately gives the support to move and do stuff...

So, wait. ALL starfish have these? Even the weird ones???
Here's where I add some of that magic Echinoblog madreporite spice! For some reason, people always assume that madreporites are the same in every species. Not so. Here, for example, is a specimen of the large, multi-armed Crown-of-Thorns-Starfish, Acanthaster planci...
What's interesting about that?? Multiple arms. Multiple MADREPORITES!!! (see red circles)
When you think about it. This makes a lot of sense. You're bigger. You've got MORE tube feet going on. So, naturally, you would need MORE water and etc. to be driving those 10 additional arms!! You can also find multiple madreporites on big ass things like Pycnopodia helianthoides-the sunflower star..
Here, we have a deep-sea starfish (Dytaster grandis) which buries itself in mud or some kind of unconsolidated sediment. The madreporite is huge and covered by spiny platform shaped plates that may serve to keep mud from clogging up the pores..
But studies of madreporite function in these animals isn't really well known.... but sometimes, it does seem to have some functional relationship..

Now, don't forget that most other living Echinoderms have a madreporite!! (or some comparable parallel structure-crinoids don't technically have a madreporite)

Here for example is an ophiuroid (aka a brittle star). Ophiuroids form a separate class of echinoderms, but are closely related to sea stars. Their madreporites are found on the ORAL surface near the mouth... (as opposed to the aboral or top surface in proper sea stars/starfish).
Madreporites on Sea Urchins are located on the aboral side (i.e., the top)

whereas the madreporites in sea cucumbers are actually INTERNAL..

Monday, January 24, 2011

PRESS UPDATES from the Echinoderm Tree of Life!

UPDATE!! 24 Jan 2011! An informative New video on the Echinoderm Tree of Life (featuring the Principal Investigators at Ohio State University)

Dec. 10, 2010!
(Photo Credit--Beth Rhenberg from West Virginia University Today)

The West Virginia University Today website and the Charleston Daily Mail both report on the involvement of paleontologist, Dr. Thomas Kammer, the Eberly College, Centennial Professor of Geology at West Virginia University in the NSF supported Echinoderm Tree of Life! Congratulations to him on his involvement!

From prior announcements...
From 12 November 2010.
Ohio's Columbus Dispatch and OSU' school newspaper, the Lantern have reported on Bill Ausich and Dan Janies' accomplishments as the new Principal Investigators on the Echinoderm Tree of Life! A big chunk of which will likely be devoted to the "pelmatazoan" echinoderms..such as crinoids and their relatives!
And the Pacific News Center has reported on Dr. Alex Kerr's , University of Guam role in the big NSF Tree of Life project!

From October 5, 2010 (Echino ATOL Launch)

Starfish, sea urchins and their kin are among the next groups of organisms to be documented in the National Science Foundation’s Assembling the Tree of Life project.

Ohio State University scientists will lead a 10-institution team in using genetic information from modern species as well as anatomical data from fossil specimens dating back more than 500 million years to figure out precisely where echinoderms fit into the history of all life.

The project is led by Dan Janies, a biomedical infomaticist
and Bill Ausich, a paleontologist who specializes in Paleozoic crinoids.This project is rare within the NSF Tree of Life initiative for its strong representation of paleontologists, who study prehistoric life for which there is no genomic record. The team includes a number of biologists and paleontologists who specialize in morphology, the detailed description of organisms based on their specific internal and external structural features.

Meanwhile, other scientists will be able to collect genetic data on living examples of echinoderms.

That combination of research techniques will pose an information technology challenge, Janies noted. Biomedical informatics researchers link computers together to analyze massive amounts of data. In this case, they will have to devise a system to capture both genetic and anatomical data and assess various hypotheses for the history of echinoderms and humans and their very deep common ancestor.

Collaborating institutions for this project are the universities of Michigan, Tennessee and Guam; Abilene Christian, Duke, West Virginia, Louisiana State and Nova Southeastern universities; and the University of California, San Diego Scripps Institution of Oceanography.

Wednesday, January 19, 2011

in Wired: The Extinction of Scientists who study species

I am featured in a new article in Wired Science that details the growing loss of scientists who describe species..... (thanks to author Craig McClain of Deep Sea News for thinking highly enough of me to use me as an example!)

Go here...(click here or on the logo)
A quote:
We are currently in a biodiversity crisis. A quarter of all mammals face extinction, and 90 percent of the largest ocean fish are gone. Species are going extinct at rates equaled only five times in the history of life. But the biodiversity crisis we are currently encountering isn’t just a loss of species, it’s also a loss of knowledge regarding them.
I am mentioned as one of the "newer" generation of scientists who study species..

Some embellishment:

I haven't really elaborated much on my exact scientific expertise. But I am one of the only scientists currently working on classifying and describing new species of asteroids (i.e., starfish or sea stars) on a global scale. There are others, but believe it or not, there are actually more starfish paleontologists (i.e., three to four scientists who work primarily on fossils) than there are those who work on describing living species! Talk about a specialized niche!
To be fair, there are also a miscellaneous number of local specialists and retired scientists who occasionally work on species restricted to their geographic area.

More regular blogging next week!

Tuesday, January 18, 2011

Thursday, January 13, 2011

Echinoblog On the Road pt. 2:What was I REALLY doing???

I am running a bit late this week... as I am still "in the field" visiting the Invertebrate Zoology and Geology Dept. at the California Academy of Sciences in San Francisco..or AM I???

Could I instead be at a top secret installation with confidential life forms from beyond our world??

For example, here Instead of a kickin-ass RARE specimen of Pythonaster in the jar below (only 5? other specimens in the world?) Could I POSSIBLY instead have some terrible new life form humanity was not meant to know??
(hint-covert, black ops, hush-hush organizations ALWAYS have a t-shirt with a readily identifiable symbol and their name plastered across the front!)

Instead of the deep-sea starfish, Hymenaster koehleri, could this be some form of extra terrestrial menace???

Instead of a specimen lot of the deep-sea astropectinid Dytaster gilberti, could this be some terrible leftover from a world-gone by when monsters roamed the Earth??? (or maybe its both?)
Instead of harmless eppendorf tubes that I use to collect data from specimens for my phylogenetic analyses... MAYBE this serve some other SINISTER purpose involving forms from beyond our world??
Instead of about 80 identified specimens of deep-sea starfishes which I identifed and are being cataloged for the museum, MAYBE these are nodules forming part of a sinister supervillain type plot!! (well except for Chrissy in the photo-she's clearly not evil at all!)
Maybe, I reviewed THREE scientific manuscripts on my break...OR INSTEAD reviewed evil starfish relatred pages of the next Necronomicon?? (or maybe they were both! I can never tell with manuscripts these days...)
or MAYBE instead of giving a scientific talk to the scientists at the California Academy of Sciences about my starfish research, this outlines my MULTI-STEP PLAN for WORLD DOMINATION!!
What was I doing really? You decide.