Wednesday, October 29, 2008

Dermechinus horridus!! Trick or Treat??

(Thanks to Dave Pawson, NMNH and NIWA for this image)
So, because this is Halloween week..I had to bring out something particularly WEIRD and spooky to share with everyone! And what better than sea urchins that look like Pinhead from Hellraiser??
May I introduce what is possibly one of the strangest sea urchins alive:

Dermechinus horridus!!

UPDATED March 2013- New Video!

Dermechinus is a member of the "archetypical" family of sea urchins-the Echinidae, which includes familiar members such as Echinus and the Antarctic Sterechinus, with which it shares a sister taxon relationship (see SICB abstract by N. cox and R. Mooi!)

These "cactus urchins" live in the Southern Hemisphere, in a subantarctic band-Chile, New Zealand, off Australia and so forth. And of course, they live in the deep-sea!!

Factoids Follow!

(Thanks to Dave Pawson, NMNH and NIWA for this image)

1. Dermechinus has a test height that is THREE times its diameter!
You may have noticed how "high" the aspect is for these strange things. Smaller individuals start out more "globe-like" but larger ones become more cucumber-like. Its unclear why the strange body shape is the way it is...

In addition to the strange body size, the Aristotle's lantern (jaw structure) and oral region (the peristome) are particularly small. But its not clear exactly why....

2. They have numerous long, slender and shiny primary spines.

The name itself describes this feature: Echinus for "sea urchin" and Dermos for skin...described by the species horridus as "horrible" (so translates as: horrible skin sea urchin).

Dermechinus' secondary spines (i.e., the smaller more numerous ones closer to the body) are found with great abundance. These structures evoke the same questions...

3. Are they they Suspension-Feeding Sea Urchins???

One interpretation of the strange morphology was made by F. Julian Fell-son of the famous echinoderm biologist, F. B. Fell.
(from Heezen & Hollister, 1971-the Face of the Deep)
F.J. Fell's PhD dissertation argues that Dermechinus is the ONLY suspension feeding sea urchin based on these reasons:
  1. Posture is similar to sea cucumbers feeding.
  2. Long primary spines are perpendicular to the body forming vertical combs.
  3. Numerous small fur-like secondary spines would be "well-suited to the entrapment of fine suspended particles and the high tests would present a large area to the prevailing currents"
  4. The tiny jaw and oral region would be "adequate for a diet consisting mostly of fine particulates transpoted to the mouth by the secondary spines+ciliary currents
I make NOTE that this is an UNTESTED hypothesis. Even Dr. Fell's comments are clear that feeding has not been confirmed...BUT, its just WEIRD enough to be possible.

What do YOU think?

A trick (untested hypothesis) or treat (making it the ONLY filter feeding sea urchin!!)??


Happy Halloween!

Tuesday, October 21, 2008

The 27 Best Deep-Sea Species #10: Echinothurioid Sea Urchins

Who, What, Where:
Sea Urchins in the Echinothuroida. Most echinothuroids are deep-sea with some shallow-water tropical members (aka the Fire Urchins-see prior post here). They are thought to eat bottom detritus and "macroplant" materials. They have yolky (lecithotrophic)eggs.

How? Sometimes there's cool deep-sea echinoderms that are cool because just KNOWING them is like a cool story. They DO interesting things and HAVE interesting parts!

1. They have little "hooved" walking spines. That's right..echinothuroids often occur on soft, unconsolidated mud..and they have unique little spines that they walk around on with these odd little flat "hooves".
(Araeosoma belli, image courtesy of Dave Pawson, NMNH)
2. The top spines in some species have big, puffy, balloon-like sacs with an offensive substance. Some echinothurid urchins have big fleshy sacs which enclose the spines emerging from the top or abactinal surface.
Based on an study by Emson & Young 1998 these spines are functionally similar to hypodermic needles and may emit an offensive fluid to ward off unwanted visitors. This is similar to the tropical species which have toxic poisons in these spines.
(Phoromosa sp., image courtesy of Dave Pawson, NMNH)

3. Echinothurids were described FIRST as fossils and THEN found alive later!! Echinothurid urchin fossils were described FIRST as Jurassic fossils and then discovered later on by early deep-sea biologists! Echinothurids are also thought to be relatively "basal" on the big evolutionary tree of Echinoids. They are "Living Fossils". Where paleontology and deep-sea biology meet and greet!

4. The test is decalcified and held up by water pressure. When pulled up on deck? these animals go by the name "Pancake Urchins"

Why? Because echinothuriid urchin tests collapse like a big empty bag of water. That's because in the wild their bodies are HELD up by the positive water buoyance in delicate paper-like skeleton.

Monday, October 20, 2008

Deep Sea Echinoderm Round-UP!!

The friendly folks over at Deep-Sea News (now at their new Discovery Channel outfit) have been doing a neato countdown of the "27 Best Deep Sea Species" and TWO echinoderms are included:
#20 The Swimming Sea Cucumber Enypniastes (pictured above)-Link here

#25 "Crawling" i.e., Stalked Crinoids-Link here. the spirit of their countdown (and because they haven't included NEARLY enough deep-sea echinoderm stuff) here is a list of "Best of" Deep-Sea Echinoderm posts from the Echinoblog...(and let me tell you how startled I was that I actually HAVE enough to do a "best of" post!!)

*Brisingid Starfish & Their Etymology

*The Rare and Mysterious "Sea Daisy" Xyloplax! Parts one: Teh Weirdness and two: Conundrums & Controversies.

*Behold Tremaster mirabilis-"about which little is known.."

*Echinoderm Big Battle! Sea Urchins vs. Stalked Crinoids!

*The Odd Deep-sea crinoid Holopus!

I will be posting jointly WITH Deep-Sea News on the next in the deep-sea species list on WEDNESDAY! Wowza!!

here's a hint..

Thursday, October 16, 2008

End of the Week Echinoderm Odd, Dumb & Silly

Starfish Meet uh..non-sand Dollars!

Luidia spp. (looks like L. clathrata then L. alternata) set to Sister Hazel!

The Sea Urchin Song!! (mostly about uni)

and finally..PLEASE, PLEASE don't do this. (sigh).

Monday, October 13, 2008

Brisingids pt. 2! The Norse Gods+Deep-Sea Starfish= GREAT marine invertebrates party trivia!!!

Brisingid starfish have plenty of exciting things going for them..they're weird, they live in a distinctive and unique way and they have a royal majesty that amazes me.

I am personally fascinated by the basis of latin names-but I think that even the most jaded non-classical student would think that the ETYMOLOGY of these beasts is cool!

Here is a quote from an early work on brisingids (G.O. Sars, 1875) describing the origin of the name. As it turns out, the original author/describer of the brisingids was the noted zoologist/and Norwegian folklorist Peter Christen Asbjørnsen and he developed a really nifty story for this unique group of animals:
"Owing to its highly magnificent appearance, and in the presentiment of its true relation to forms long ago extinct, he (Asbjornsen) applied to it the very characteristic and excellent mythological apellation Brisinga, derived from "Brising", the breast-ornament of Freya, which according to ancient Norwegian tradition was concealed by Loke (=Loki, the god of mischief & evil) in the abyss of the primitive Ocean."
The necklace (or sometimes referred to as a broach) goes by Brising or Brisingamen and there are several variations on the story.Click here to see some of the collected stories from Wikipedia.

But with the theme set, most of the names in the Brisingida became further based on characters in Norse mythology. Here are four that are the most apparent.

1. The Necklace Brisingamen.
The original subject of the story-the necklace hurled into the "Primitive Ocean"...which may not have itself, actually been star-shaped. Oddly, I could find no actual pictures of "brisingamen" or at least, none that were consistent.

Brisingamen is the inspiration for the group: Brisingida/Brisingidae

and for several genera: Brisinga, Brisingella, Brisingaster, Brisingenes, Craterobrisinga, and Stegnobrisinga.

2. Odin, the Chief of the Norse Gods.
Odin is the Chief of the Norse gods. And the namesake for Wednesday (=Wodensday). According to Wikipedia he is associated with wisdom, war, battle, death, magic, poetry, prophecy, victory and the hunt.

He is also the namesake for two genera of brisingids:

Odinella-a weird Antarctic brisingid which broods babies in its armpits.

and the genus Novodinia (which actually used to be called Odinia until it was discovered Odinia was already in use...). Novodinia occurs all over the world and is a "shallower" brisingid then most, typically occurring above 1000 m.3. Freya, Odin's wife & Goddess of Babies and Cats.
Freya was the wife of Odin and was the Norse goddess of love, beauty, fertility, childbearing..and also, oddly enough, cats.
Since Brisingamen is Freya's necklace/broach thingie she occupies a pretty central role in the story. Allegedly, she does quite a few unsavory things to get it back after Loki steals it and hides it amongst the dwarves...

Her central role is appropriate given that she is the namesake for the Freyellidae: the truly deep brisingids that are thought to be associated with abyssal (>1000+ m) soft-bottom plains.

Genera include: Freyella, Freyellaster, Freyellidea and Freyastera.

4. Midgard-Earth: the Mortal Realm & Its Serpent

Midgardia is one of the largest of brisingids with an arm length of nearly 2 feet across (which means it would be nearly 4 feet across with arms extended!!).

According to Maureen Downey, former NMNH collections manager-Midgardia xandaros is actually named for the Norse "Midgard Serpent" which encircles the Earth.

Midgard is what the Norse myths called Earth..and xandaros is Greek for "fantastic monster"..and hence the name would be translated "fantastic monster of Earth", which is really sort of an interesting (if inaccurate) name!!
I hope that one of these days, I will have a chance to name a family of starfishes after a bunch of super-powered beings!! ha! The Justiceleagidae! Watchmenaster!

Thursday, October 9, 2008

Brisingids pt1! Weird Deep-Sea Halloween Starfishyness!

As a summer student at the Hopkins Marine Station/Monterey Bay Aquarium Research Institute program back in the late 90s I was still deciding what I wanted to do with my life.

I was thinking that I would go into Entomology unless my summer student internship thingie worked out.

It did.

I fell hard for starfish. and naturally I went directly to the strangest of a strange group of animals living in a strange world. Starfish were odd and alien enough...but to see the REALLY bizarre ones?? Amzing.

I fell in love working with these animals and the first time I ever saw a living one was a HUGE day!!
I eventually went on to "cut my teeth" on brisingids, doing my Masters in Marine Biology at San Francisco State University and the California Academy of Sciences.

What's weird and AWESOME about brisingids? Simply put.... Everything. Some basic factoids:
  • Brisingids are proper STARFISH (Cl. Asteroidea) part of the Forcipulatida-which is the same group that includes the common starfish Asterias and Pisaster. The same general kind of pedicellariae (see below) found in brisingids are also found in common intertidal starfish.
  • Brisingids are deep-sea animals. Some are "shallower", occuring on the shelf (i.e., 100-700 m) but others, such as Freyella and its kin live in the "true" deep-sea-the Abyss and so forth (>1000 m!). Some of the world's deepest starfish (~5000-6000 m) are brisingids.
  • They live all over the world. Antarctica, Pacific, Indian, and Atlantic. Oddly, none in the Arctic.
  • Brisingids are diverse. Nominally 70 species, in 14 genera, divided into at least 2 families.
  • The name "brisingid" (order Brisingida) is derived from a story in Norse mythology which is so neat that it is the subject of next week's post!!
But what is the FUNDAMENTAL thing that makes brisingids so distinctive??

Brisingids have body forms that are specially modified for suspension feeding!

This affects nearly ALL aspects of brisingid body form and ecology. But how??

While you're looking at the next couple of lines..think about the sort of body form you see in other suspension feeding echinoderms such as crinoids or even ophiuroids! Brisingids look like a weird cross between crinoids, ophiuroids and asteroids.

Body Form
The endoskeleton in brisingids is closely tied to the suspension feeding lifestyle.
  • Disk skeleton is fused into a ring and braced to support the arms as they are held up in the water.
  • Tube feet "hold down" the animal as they raise their arms into desirible current flow. But movement is possible.
  • multiple arms are found in ALL brisingids. Some might have 6 arms..but most have about 8-20 arms. This is presumably to faciliate the suspension feeding.
  • Fully developed gut and stomach are missing. Possibly for secondary absorbtion of nutrients?
  • Gonads are in the arms but space for internal structures is minimized.
The modifications are even so specialized that the ambulacrals in brisingids are actually uniquely shaped as vertebrae! Presumably to allow the most flexure. Note: "normal" ambulacrals look more like this: Feeding Mechanism
Perhaps the MOST distinctive aspect of brisingids is HOW they feed.

Bear in mind, that it was only in/around 1976 that we even KNEW that brisingids held their arms up in the water!! When they were first was thought they just dragged their arms along the bottom!

A paper by Roland Emson (at King's College in London) and Craig Young (then at Harbor Branch, now at Oregon Institue of Marine Biology) presented a detailed study of how feeding happened. (Interestingly, I had later discovered that the Russian deep-sea biologists S. Galkin and N. Korovchinsky had documented feeding in a paper from 1984. Not as detailed as Roland and Craig's work and in Russian-but earlier nonethless..) Here's how it works:

1. Brisingids have lots of spines.
Spines come off the lateral sides. They project off the tube foot furrow. They are almost everywhere! In some species-spines are even present on the surface of the body! All arranged in a familiar "cruciform" arrangement that you see over and over again in other echinoderm suspension/filter feeders. 2. Spines are covered by a "sock" of pedicellariae. Each one of those spines is covered by a sheath of tissue, like a sock. This "sock" is covered by literally THOUSANDS of Frakkin' little pedicellariae!! These are little jaw-like structures that cover the surface. Think of them like a bunch of little bear-traps.
3. The little bear-traps (pedicellariae) densely cover ALL of these spines.
4. The pedicellariae essentially "go off" when food hits them. So, some small shrimp, krill or other tasty bit of organic, edible goodness?? BAM! Snagged by the spine/pedicellariae!! Prey are held fast by the pedicellariae similar to velcro (to use Emson & Young's terminology). 5. Once food is is then moved via the tube feet to the mouth and devoured. According to various accounts, this is typically small amphipods, and other hapless crustaceans...(ha! take that small hapless crustaceans!)

Whew! More on brisingids next week!!

Monday, October 6, 2008

Fire Urchin Video!

I have for some reason encountered a trio of tropical Fire Urchin videos I feel compelled to share with everyone this week! Maybe its because they remind me of Fall?

Two of the species below belong to the Echinothuriidae..which are primarily deep-sea (I will follow up with a post on this later)..but the species featured today live in the shallow waters of the tropical Indo-Pacific!

The species at the very bottom is Astropyga which is a member of the Diadematidae...not that closely related-but similar in appearance...(sorry to be paraphyletic here..but they do all carry a theme!)

Their bright colors announce the very toxic poisons that their spines and other structures produce (more on this later when I fully write up echinothuriids later on!)

Asthenosoma varium

Asthenosoma sp.?

Astropyga sp. (Diadematidae)