Echinodermata! Starfish! Sea Urchins! Sea Cucumbers! Stone Lillies! Feather Stars! Blastozoans! Sea Daisies!
Marine invertebrates found throughout the world's oceans with a rich and ancient fossil legacy. Their biology and evolution includes a wide range of crazy and wonderful things. Let me share those things with YOU!
I've been in Japan for the last 6 weeks studying Japanese sea stars at the National Museum of Nature and Science in Tsukuba, Japan!
As this is my last week at the museum I thought I would share some neat pics of some of the interesting echinoderms that I've encountered over the last few weeks....
Trophodiscus almus. This is an unusual species, which brood baby sea stars on its top surface! You see those weird round to star shaped white spots on the surface? Those are the juveniles which live on the surface among the "forest" of spines present..
Close up of the stalked crinoid Saracrinus nobilis! This closeup shows us the arrangement of plates on the various arms and how they fuse together to form the various skeletal architecture used to identify them and to compose the arm structure..
A picture of the stalk.. note the angles!! Cool!
A slightly different crinoid.. a feather star. (an unstalked vs. the stalked species above).but a closeup of the arms and how they articulate and form different fused pieces...
Image by Viktor Lyagushkin. Gorogonocephalusfrom the White Sea
Basket stars are a very unusual kind of brittle star (note that they are NOT proper starfish) which have long, branching arms which they extend into the water in order to feed. Tiny little hooks on the arms are used to capture food which eventually makes its way back to the mouth.
Here are some gorgeous Gorgonocephalus sp. (which occurs mainly in cold-water settings) images to kick off 2013!! Enjoy!
Some gorgeous shots of G. arcticus from the White Sea by Alexander Semenov
G. eucnemis from echeng (the "rose star" is the solasterid sea star Crossaster papposus) in Alaska.
Gorgonocephalus from Norway, 928 meters! Arms are tucked away...Image by SERPENT Project!
Several more on a ridge, using their arms to feed. Also Norway, 928 meters. Image by SERPENT Project.
More G. eucnemis from Alaska.. Images by jrixundewater
Close up of the arms..
An unusually pale, "bushy" individual from British Columbia. Image by Ed Bierman
Here's a really nice one of G. eucnemis. by "northwest diver" Gorgonocephalus fr. Newfoundland. Image by Derek Keats
Newfoundland Image by Derek Keats
Hmmm... y'know, it never occurred to me before but Gorgonocephalus DOES bear a striking resemblance to a certain CRYSTALLINE ENTITY from the 24th Century...
A little bit of Echinoblog extra today! thanks to biologist Jackson Chu (His website can be seen here. thanks Jackson!) has posted some exciting new deep-sea video that *needed* to be shared...
Deep-sea Echinoderms from Canada (submersible ROPOS from what the tags say..)
This starts with Gorgonocephalus and proceeds to show deep-sea cucumbers (including some sea pigs!), various starfish, other ophiuroids and sea urchins...
Also kind of cool... video of the predatory tunicate Megalodicopia (not an echinoderm-but closely related to you and me). Most tunicates are filter feeders-but these have modified their "in" siphons so that they capture prey in the bowl-shaped hood... (and on top of it you get some cool music from Kill Bill!)
As a follow up to this week's earlier post on Gorgonocephalus- Today we have some nice videos of Gorgonocephalus and its relatives in the Gorgonocephalidae! (i.e., other basket stars!)
Enjoy!
A nice Gorgonocephalus time-lapse! (try to ignore the silly music)
Probably not Gorgonocephalus but possibly something related...
Not Gorgonocephalus but probably something related... pt. 2
Its been awhile since I've done a "creature feature"..so today, I give you the "Basket Star"aka Gorgonocephalus!! Go here for a photoessay.
Gorgonocephalus belongs to the class OPHIUROIDEA, that is, it belongs to the same group as the more typical 5-armed "brittle stars" you may be more familiar with. Such as the one here and the ones here.
Gorgonocephalus occurs mainly in cold-water environments, and is found in the Arctic, the Antarctic and in the deep-sea throughout the world. Although, shallow in some places (such as Alaska, Canada, etc.) it is found mostly in deep-water. There are about 10-12 species (look them up here). Good luck telling them apart though. Many are VERY similar in appearance and are distributed over a wide range...
Unlike most other ophiuroids, the special "basket star" and "serpent star" group have a VERY different arm structure related to how they feed. For example:
1. Arm structure in basket stars has a thick, fleshy covering over the basket star endoskeleton. If we look at a cross-section through the arms, we see in green that there is an exterior leathery "skin" that completely covers the calcium carbonate "ossicles" aka vertebrae that compose the arm structure. ...and here's the rest of it! (with skin removed from vertebrae-like endoskeleton) 2. Arm structure (i.e., the vertebrae-like endoskeleton) in this group SPLITS (aka bifurcates) instead of staying in a single linear series. There's a whole bunch cool stuff about Gorgonocephalus, the least of which is its NAME, which literally translates into "Gorgos" and "-cephalus" aka the Greek for "Gorgon's Head" named for the fearsome monsters (e.g., Medusa) with snakes for hair whose gaze could turn people to stone!! ....and here is one for comparison! Remarkably little is known about these animals. But there are some GREAT feeding studies on Gorgonocephalus, including this recent one by Rosenberg et al., (2005) and this earlier one by Emson et al. (1991). So, let's look at that!
FEEDING in Gorgonocephalus is relatively straightforward. They sit on perches, often corals, sponges, rocks or sometimes just on the seafloor bottom like this:
Gorgonocephalus feed mostly on small crustaceans and similar critters, such as the "northern krill" Meganyctiphanes norvegica . That's in contrast to other kinds of "filter feeders", like crinoids, that pick up small to microscopic food particles.
Functionally, this makes basket stars-PREDATORS! Pretty weird ones, when you think about it..
How do they feed? They use their crazy numerous and COILED arms in big, extended feeding "basket", which coil and curve in and around on themselves...like this...
Bear in mind that the arms are covered with HOOKS and SPINES! Here is a closeup....
(Fig. 2 from Rosenberg et al., 2005)
These hooks function along with spines and the tube feet to capture (i.e., snag and snare)prey that get too close! and work it down to the mouth... Which, represents the SECOND echinoderm-thing that kinda looks like the Sarlacc pit from Return of the Jedi!! (or maybe the Sarlacc is just a giant desert Gorgonocephalus???) The studies I read suggest that Gorgonocephalus prefers a pretty mellow current.
Rosenburg et al. (2005) mention that in high current speeds (> 50 cm/second) these animals have difficulties keeping their arms stretched out and the number of curled arms increased, which they believe will decrease drag!!!
Some basket stars, such as Gorgonocephalus have arms that will reach almost 2 to 3 feet across! Not all of them are this big but a lot of them are pretty sizeable.... 2. Ophiopsammus maculata (New Zealand)
A member of the Ophiodermatidae, which are usually pretty small tropical beasts..but this one gets pretty big!
A disk that is about 2-3 inches across with an impressive arm span of over 6 to 7 inches!!
Its unclear how they feed but some suspect that they do something very similar to this! 3. Astrostoma agassizi (Antarctic: Southern Ocean)
Okay, so, I'm cheating. Because Astrostoma agasszi IS a member of the Gorgonocephalidae (see above).
I will probably write this up in more detail later but here's some quick details at this site:
Astrotoma is BIG. Disk is easily 2-3 inches across with correspondingly thick arms.
They live in the Southern Ocean/Antarctica in relatively deep-water (about 90-1500m) and feed on crustaceans and other various prey using their very long arms!
4. Ophiarachna incrassata: Giant Green Fish-eating Brittle Star (tropical Indo-Pacific) I wrote up something about this species awhile back There's a lot of neat things to say about it..but it is BIG. check this video out again! 5. Ophiocoma aethiops (Baja California/Mexico)
All members of the genus Ophiocoma are tropical, shallow-water in all of the world's oceans and all of the species are pretty sizeable. But for some reason, Ophiocoma aethiops from tropical East Pacific is just a bit bigger then the others species of Ophiocoma that one sees in the Indo-Pacific. There's more to this beast..but for now..just appreciate the fact that its a BIG one! Honorable Mention: Stegophiura ponderosa
So, this is a deep-water species (at least 100-500 m) from off the west coast of North America, Japan, and Russia.
This animal is pretty big, but doesn't get beyond about 2 inches in diameter?? So how do they qualify??
Stegophiura ponderosa is thick!!! Maybe about two to three disks thick???
Unfortunately, very little is known about its biology. What does it do with all that heavy body mass?? Arms that don't really move out of one plane?? What do they eat??
How do we know so little about critters that are this frakkin' big????
