Tuesday, April 24, 2012

Pt. 2! Snails and the Starfish that love to eat them!

More escape responses! This time snails (i.e., gastropods) and some "extreme" behavior on their part to get away from predatory starfish!

Japanese Astropecten vs. snails!

The neat snail escape response to the sand star Astropecten begins at 1:30!  Honestly, I've never seen a snail pull the ol' push myself out of the way with my foot maneuver!

Pycnopodia vs. abalone! 

Here's a few videos of abalone escaping the large Pacific Pycnopodia helianthoides!

This one shows that even brief contact with a sunflower star will ellicit the escape response..

Scale Worm Helps Snail! Biting Starfish (Pycnopodia)!  I missed this one I don't know-but COOL!  the good part begins at 0:55

And here's an escape response ellicited by the sea slug Dendronotus!

Sunday, April 22, 2012

Cockles and the Starfish who like to eat them! A nice gallery of escape responses!

Here's a neat escape response that was captured on Flickr between a Florida cockle and the sand star Astropecten! Images captured by "The LivingSea.com"  Plus some video of Pacific cockles being chased by sunflower stars!

Here, we see Astropecten articulatus in contact with the cockle (Trachycardium egmontianum) A Beaded Sea Star picks up the scent of a mollusc nearby

The cockle is alerted! And it extends its large muscular foot to begin its escape! Florida Prickly Cockle extends its foot to leap away (Trachycardium egmontianum)

 The foot pushes the cockle away!
 Mollusc uses its foot to escape predation

And aWWAAAAYYYY it goes!
 A Florida Prickly Cockle avoid predation (Trachycardium egmontianum)
And away!
Bivalves methods to avoid predation

On the Pacific coast, different species of predatory starfish (in this case the sunflower star Pycnopodia helianthoides) also feed on cockles.. an identical response is observed..

Here's a really nice one

Here's one that literally does a judo like flip on Pycnopodia!

here's a decent one with a wacky sound track..

Here's a variety of responses to both cockles AND scallops!  (the scallops are the one that "jet" away using their excurrent siphons)

Thursday, April 19, 2012

Sea Urchin attacks crinoid in time lapse!

So a bonus video today!  A cool time lapse of a sea urchin attacking a crinoid. We've made mention of the predatory propensities of sea urchins relative to crinoids before..  HERE  and here

Tuesday, April 17, 2012

The Sea Urchin Flame Wars of Theodor Mortensen!

Today, as they said on TV, a special "echinological" episode! Something a little offbeat...

I focus on a giant in the historical echinoderm literature-one Professor Ole Theodor Mortensen (1868-1952) who was at the Zoological Museum of Denmark.

Its not an understatement to say that Mortensen was a HUGE name in echinoderm biology. He published on every group and on multiple aspects-classification, larval biology and the list goes on...

Probably his most incredible achievement though was that he wrote this huge series of 15 HUGE books that established THE classification of sea urchins . Go here to read more about them.. 
But, all genius comes with a certain...eccentricity.

Mortensen could be a harsh critic and towards the twilight years he began to rather strongly express his dissatisfaction with the work of his fellow colleagues!

Some of the opinions stated are OUT IN THE OPEN and published in a book that he probably realized would persist for hundreds of years.

I found all of these quotes in just ONE volume (albeit the last one) of Mortensen's famous sea urchin monograph published in 1951... but much of his work spans several decades.

Some Background on Taxonomic Synonymy
To give you readers a bit of background MOST of these discussions are about what's called taxonomic synonymy.  You can read a full account here

Basically, this is when extra names are produced for the same species owing to
1.  Ignorance or mistakes (i.e., new "species"named without checking the literature to verify that the species name did not already exist)
2. Incorrect species assessments (the author may have seen a damaged specimen or simply had a species description that did not account for all the details)

Either way- the oldest name has priority over all the others. Its often the work of a dedicated taxonomists or systematist (such as myself or Theodor Mortensen) to make certain that there are NO "extra" names out there. And of course, that we as scientists, do not produce unecessary names cluttering up the place!

So, yes-a perfect profession for you very order-obsessed types!

The Wit of Theodor Mortensen!

To put you in his mindset (and to be fair to him) remember that he'd been working on these books for DECADES.  And this was after MANY years of having to deal with the various crazy "legalese" of taxonomic synonymy and nomenclature.

He often seemed particularly exasperated (a frustration I know well!) when his colleagues simply did not exercise the care or effort to publish their species names correctly.

I should also mention that for scientists-statements like this are VERY unusual..especially when you put them into, not just a journal, but a book....

Some of the most colorful comments were about his colleague-paleontologist Jules Lambert...

pg. 579-he starts with kind words..
I am exceedingly indebted to that work, as well as to many other works of Thiery and especially Lambert, works so full of learning about the fossil Echinoids. Without, especially the Essai de nomenclature raisonnee it would have been impossible for me to get an anyway adequate knowledge of the immense number of the fossil Echinoids.  
But then cuts loose!
But the way in which, particularly Lambert treats the nomenclature, arbitrarily adopting old, impossible names instead of names otherwise unanimously used in the whole echinological literature and thus changing the old good names and interchanging them-like the names Echinocyamus and Fibularia- or using them in quite a new meaning like e.g., Spatangus or Schizaster, and then impertinently, as a dictator, changing the names of the recent forms, about which he knows next to nothing, can only be characterized as a crime to science. 
Authors on recent Echinoids have in general neglected Lambert's nomenclatural changes, whereas his paleontological colleagues generally followed him through thick and thin. Alone Fourtau (Fortau was another researcher) ventured sometimes to defy the tyranny of Lambert. (!)
On the next page (pg. 580), we are treated to his opinions regarding Hubert Lyman Clark, a widely published  researcher at the Harvard Museum of Comparative Zoology
Image from the Smithsonian Archives.
In this connection it may be mentioned that H. L. Clark sometimes undertook quite absurd changes of names, as e.g., the name Echinocyamus pusillus changed into Echinocyamus minutus on the base of a very dubitable old text....
Mortensen frequently took HL Clark to task...here is a bit from pg. 37-38 (some details omitted for the sake of getting-to-the-point)
Apparently Clark did not take the trouble of reading Leske's description of his Spatangus ovatus...... It is also an offense...... to think that he could draw the very characteristic test of Maretia planulata so badly....on the whole, this Spatangus ovatus, badly figured and described, and without locality deserves only to be left entirely out of consideration as not recognizable. But Clark deserves to be seriously  blamed for having so inconsiderately inroduced such change of a common, otherwise universally used name.
Mortensen (pg. 85) was often sarcastic... (on a rival colleague's observation of behavior in a sea biscuit type irregular urchin)
Another observation by MacBride , Op. cit is that he has seen a young specimen climbing up the vertical walls of an aquarium as do regular sea-urchins; he sees herein proof that it must be a descendant from some Regular Echinoid. Well, yes, of course--What else could be the origin of the Irregular Echinoids!
But probably one of the most interesting "conversations" was Mortensen summarizing his differences  with noted marine biologist Alexander Agassiz.  At first, he is effusive with praise!!
A great step forwards in our knowledge of Echinoids was made by the grand work "Revision of the Echini" by A. Agassiz (1872-74). With immense learning and energy he cleand up the older literature on the recent Echini, examining the specimens in the various collections in the world. This work will remain classical, the foundation of the study of the recent Echini; and most of the photographic illustrations are simply perfect, nothing like it having ever been published. 
But then there is a turn in his opinion...
But much worse I found his second great work, the report on the Challenger Echinoidea (1881)..... going into a critical study of the work I could not help finding it--I cannot help saying it--a bad piece of work, not at all worthy the author of the "Revision of the Echini"...
Strong words! But not without repurcussions..
In my first larger work, the report on the Echinoidea of the Danish Ingolf Expedition I. 1904, I gave--rather unrestrictedly I admit--vent to my criticism especially of the Challenger Echinoidea, which resulted in a furious attack on me in Agassiz's next work, the "Panamic Deep Sea Echini", even accusing me of "gratuitous misrepresentation of facts" (Op. cit. pg. 25)..  I replied to Agassiz's criticism and proved its injustice, particularly the alleged misrepresenation of facts, which was of course, not at all justified, there being no misrepresentation at all....
Amazingly..there is more and much of it is spread throughout Mortensen's work.. His opinions and comments are a fun little "easter egg" that sometimes pop up when going through his monographs and published papers.

So there you have it! The old-fashioned version of Flame wars, easter eggs and the ultimate fan boy commentary.. on sea urchin papers!

Tuesday, April 10, 2012

The Panoply of Pedicellariae Post!

Pycnopodia helianthoides
Wonderful image by Judt on Flickr


No term excites a starfish biologist (well, me anyway..) more than trying to figure out what pedicellariae do!

But wait, you've never heard of the word? What are they?  I'm glad you asked! 

Pedicellariae (singular pedicellaria) is a blanket term that is used to describe a panoply of tiny claw, clamp, wrench or beak shaped structures that are present on the external surface of starfish and sea urchins. 

Pedicellariae absent in sea cucumbers, ophiuroids, and crinoids but seem to have developed as very different structures in sea urchins vs. starfish. 

As a generality though, they are used by the animal to interact with the environment. They can grab or protect-but the exact use of pedicellariae in some groups seems... mysterious. I'll treat pedicellariae in sea urchins another day but today, let's go through some examples of what some pedicellariae are known to function as. 

In some cases function is known and other times not...There are many different kinds of pedicellariae-but here are some of the best known (and easiest to see..)

1. "Forceps-like" (also called forcipulate) Pedicellariae
These are pedicellariae that are composed of three pieces with two really pronounced wrench-shaped "jaws" that usually have teeth or some kind of nasty looking shank on each piece.

In a lot of forcipulate species, such as this Antarctic Labidiaster annulatus (which I wrote about before here)  they use the pedicellariae to aid in capturing krill!  
And in fact there are at least one or two other instances of forcipulate starfish species that use pedicellariae to capture prey.. Go here to see the write up on how some starfish can capture active prey.

  But in Labidiaster, these pedicellariae are HUGE! And NASTY lookin'... The ones in this species are quite large. The one in the picture below is easily a whole MILLIMETER or two across!  (trust me that's big for pedicellariae!)
Here's a Scanning Electron Micrograph picture to give you a clearer idea of what they look like and with all of the glorious details! 
SEM pic from Dearborn et al., 1991
The pic of the pedicellariae above the SEM was taken from the arm below for scale.. Note the whitish fuzzy stuff on the surface of the arm? Those are the pedicellariae.
And here's the specimen the arm is from for reference... (a living example is above)

Forceps-like Pedicellariae are formidible and numerous.  Below are some close up pictures of these  tiny structures on two well-known species on the North American Pacific coast: the giant sunflower star (Pycnopodia helianthoides) and the ochre star (Pisaster ochraceus).

Pedicellariae are typically present around the spines in retractable rosettes or pompons, numbering in the THOUSANDS! These could be extended or retracted like gun batteries if the animal felt threatened.

Pedicellariae are smaller in other forcipulate asteroids but can be quite effective.

During the days of my halcyon youth when I worked as a docent at touch tidepools at Steinhart Aquarium and Monterey Bay Aquarium, people with hairy arms had to exercise some care not to completely apply the surface of the ochre star (Pisaster) lest  you wanted all of the thousands of little claws to tear off all your arm hair!

Here's a nice close up of Pycnopodia helianthoides-note the many, tiny white bits around each large white spine. The finger-like translucent structures are called papulae (aka the gills).
Pycnopodia helianthoides
Image by Judt
Here's a pic of the whole animal for comparison. Pycnopodia are soft to the touch but get quite large-reaching up to 2.5 to 3 feet across!
Orange Sun Star (Pycnopodia Helianthoides)
Image by Yawnthensnore

Here's an image of the pedicellariae on Pisaster ochraceus. Pedicellariae are the tiny little beak-shaped structures that are around each spine on the surface of the animal. Those big white things are spines-
Starfish close-up texture photo
Image by Alan Davis Photo

Here's a pic pulled farther back to give you some scale as to where pedicellariae are found..
Starfish close-up texture photo
Image by Alan Davis Photo

There are often several types of pedicellariae on each species. In addition to the ones above Pisaster ochraceus also has these really distinctive ones that look like claws rather than beaks!
Image from Fisher, 1930, Fig. 8a

There are a few species of forcipulate asteroids that display how pedicellariae are used-probably for feeding and maybe defense.

But let's look at a few other weird shaped ones...

2. Bivalve Pedicellariae

Starfish in the Goniasteridae and the related Oreasteridae have a different type of pedicellariae. These are flattened and more "lip-like" and can be VERY abundant on the surface of some species.

This is one tropical oreasterid called Anthenea for example..

And if we want to take those bivalve pedicellariae to extremes.. here's a genus and species of deep-sea goniasterid I described a few years back from New Caledonia..called Akelbaster 

And there's some pretty neat triads of bivalve pedicellariae on this beast.. the goniasterid Eknomiaster beccae! This was another species I described awhile back.. 

Some bivalve pedicellariae are not only large but also a bit taller such that they actually seem like large clamps!
Hippasteria phrygiana
Some awesome pics of Hippasteria phrygiana by Katie Gale! 

And here is a closeup showing several tinier bivalve pedicellariae on the surface of a tropical oreasterid fron Singapore:  Anthenea aspera. The pedicellariae are the tiny little white clamp-shaped structures..
Cake sea star (Anthenea aspera)
    Image by Wildsingapore!

Very neat looking-but again the question: WHAT DO THEY DO?? 

Do they use them to protect themselves from small, annoying crustacean predators? Do they aid in feeding? Some weird biophysics thing we've not figured out yet???

3. Cholocariform or "Other"? 

And then, every so often you get an especially weird and large pedicellariae such as the one you see in the deep-sea Antarctic Chitonaster felli...

The pedicellariae are these five huge pincer-shaped structures that are present on the surface of each interradius. 

Each one seems to be made up of two clamp-like components...
But again the question?? What are they used for? Why so big in this species but so small in its sister species?  How would the animal use these as a defense?  What other function might they be used for?

Scientists have been observing pedicellariae for literally 100s of years (they were originally described as animals! if you can believe it!) but a good understanding of these structures has been elusive! Its weird stuff like this which makes echinoderms such a joy to study...

Friday, April 6, 2012

An amazing Black and White Sea Urchin film/video from... 1928???

Found this stunning Black and White video/film called "Les Oursins" which shows what I believe is the spatangoid  Echinocardium cordatum and other sea urchins..

The description reads
Réalisé en 1928, et donc muet, ce film est un des premiers grands exemples de l'art singulier de Jean Painlevé. Grâce à des techniques de prises de vue originales, mais surtout à un sens de l'image et du rythme, il parvient à décrire de manière extrêmement précise et pédagogique les caractéristiques d'une espèce animale, tout découvrant les beautés étranges, fascinantes, parfois comiques que permet l'observation d'êtres auxquels la plupart ne trouverait aucun intérêt. Chez lui, sens de la beauté et exigence savante se renforcent mutuellement.
Which translates to English as
Produced in 1928, and therefore silent, this film is one of the first great examples of the singular art of Jean Painlevé. Through techniques of original shooting, but mostly a sense of image and rhythm, he manages to describe with extreme accuracy and pedagogical characteristics of an animal species, whilediscovering the beauty strange, fascinating, sometimes comedy that allows the observation of things which most would find uninteresting. Home, sense of beauty and scholarly requirements are mutually reinforcing.
I know nothing about French filmmaking..but this is pretty amazing footage.. 

Tuesday, April 3, 2012

Deep-Sea Evolution-Consider the vertical instead of the horizontal! Discovering different species along a slope!

Image courtesy of Hawaiian Undersea Research Laboratory, Honolulu, HI
All of this talk of deep-sea submersibles goin' down to the bottom of the ocean and so forth has everyone focused on the abyss and the deep-DEEP-sea!

Now, echinoderms are a BIG component of life found below 1000 m and are among the deepest animals found in the abyss. Brisingid starfishes for example are found as deep as 6000+ meters!

Probably one of the most fascinating questions that interest biologist-regardless of where they work is to ask "How did that species evolve?" 

One such question is the subject of today's blog! This features results from a paper published by my colleague Kerry Howell and her colleagues at Southampton Oceanographic Center in the journal Marine Biology

Howell studied a deep-sea starfish called Zoroaster fulgens which occurs all throughout the Atlantic Ocean, typically between 220 and 4810 meters!  
Although you can find it both in European AND North American waters, Howell's study site was
in the Porcupine Seabight located in the northeastern Atlantic.  

From Howell et al., Fig. 2
This species occurs widely and yet, the different external features of different individuals varied slightly between several individuals.

Usually, when we see different features on different individuals we think about whether or not those variations might actually represent a different, possibly new species. 

Or alternatively, this is what's known as natural variation. 

Human beings for example are widespread and can have blond, black, or brown hair, blue or brown eyes. And yet are all considered the same species. Maybe having different body shape is how starfish express natural varaition?

In Zoroaster fulgens, Howell observed that there were 3 different "variant" types...
From Howell et al, 2004 Fig. 1

This top one for example was referred to as the "robust" form with much more solid, shorter arms.

This middle one was referred to as the "slender" form and it had more tapering, more elongate arms..

And finally, this bottom one was referred to as the "long-armed" form due to its very tapering and elongate arms.

As it turns out, each of these different forms, each occurs in a different depth range in the deep-sea. The long-armed one occurs deepest at the 3300-4020 meter depth range whereas the other two were present in shallower (but still deep) waters...
Howell then sampled DNA (2 different genes) from each of the different forms and found that indeed-there were three distinct lineages that corresponded with each distinct morphotype!
Howell et al. Fig. 3 from 16S data
She observed that the deeper long-armed form was most closely related to the one with slender arms relative to the shallower "robust" form.

Thus, even though the "robust" form and the "slender" form occur together at the same depth they were the most genetically different from one another. Two separate lineages but living side by side.

In contrast, the "long-armed" form was separated from the other two by a vertical gap of 1100 m.  

This suggested that all 3 of these species were reproductively isolated from one another. 

The "robust" form is pretty clearly separated from the other two and given the amount of genetic distance relative to the other two forms on the tree, it is very likely what is called a "cryptic species"-one that has effectively "hidden" in plain sight but has been determined to be different as supported by independent (usually genetic) evidence. 

So, in Context...
Many times we often look to examples of speciation that involve models that show how different populations have become isolated from one another (eventually becoming species) in a horizontal plane.  For example, like this..

From the Understanding Evolution website
Its unclear exactly how these different lineages of Z. fulgens may have separated. What kinds of natural barriers may have led to their isolation??  Other deep-sea invertebrates, such as crustaceans and mollusks also show speciation along deep-sea slopes.

Have the gametes and/or larvae been transported along these great distances?  Any number of oceanographic barriers or settings in the deep-sea (at different scales) could have played a role.

For example, currents that isolate settlement, or the topography (ie shape of the ocean bottom) are all possible ways that different populations/lineages of Z. fulgens might have been isolated thus leading to different species. 

But is evolution across a vertical gradient really that unusual?  Check out this blog I wrote a few years ago about the evolution of Zoroaster in and around the Antarctic..

Here is a pic of some Eocene fossil Zoroaster sp. (that looked like Z. fulgens) which, when alive, likely lived in shallow-water and looked surprisingly like the living ones..
and today.. ALL of the species in the genus Zoroaster (including Z. fulgens) live in the deep-sea.  Clearly.. a puzzle is at work and hopefully one day it will get worked out!
Image courtesy of Hawaiian Undersea Research Laboratory, Honolulu, HI

Ophiuroid eye video! feat. Dr. Gordon Hendler-LACM!!

A short addendum to last week's blog that featured a little bit about how ophiuroid "eyes" are being studied by bionics and optical physicists..

Here is a cool video featuring one of the authors of the paper-LA County Museum curator and ophiuroid biologist Gordon Hendler! Go here to see the LACM Echinoderm website!