The Rotulidae: Strangest of the Sand Dollars

Leave it to echinoderms to take even the best known of animals, like a sand dollar, and make it even STRANGER than you could have thought!!



But first things first. Sand dollars are highly modified SEA URCHINS that live on sandy bottoms, mostly in shallow tropical to temperate water places. Please make a note of it. (or go read this post here!)

Most sand dollars are either kind of disc-shaped such as this Pacific Dendraster excentricus.
                     






But then you get THESE weirdos!

See all of those flanges or finger-like projections coming off the edges?? Those are NORMAL for these sand dollars!  Let me introduce you to the sand dollars of the family Rotulidae! 

There are actually THREE genera of rotulid sand dollars, Rotuloidea (the oval one), Rotula (the one with holes) and Heliophora (the one without holes). And all of them seem to have some degree of these weird finger-like projections. Living rotulids seem to occur almost exclusively in the West Africa region (and some are fossils-see below).

This image is from Wikipedia! 

Let's go through and meet these three kinds of rotulid sand dollars!! By the way, if you want a scientific guide to ALL THE SAND DOLLARS including the rotulids, it is available as an OPEN ACCESS file here. A fine piece of work by California Academy of Sciences Curator and sea urchin/echinoderm expert Rich Mooi. 

I should note that all members of the Rotulidae are also found as fossils...
                          

1. The genus Rotuloidea. The first is this relatively simple looking guy.. Rotuloidea fimbriata. This species is only found as a fossil, occurring from the Miocene to the Pliocene (that's between 3-23 million years ago).  Found in Morocco.

Image from this Echinoids Gallery page

2. The second member of this fantastic sea urchin trio is the genus Heliophora! 

 That is ONE FANCY ass name! The genus is actually Latin for "Bearer of the sun" and you can sort of see why if you see one positioned as such (upside down). This genus includes two species.. Heliophora orbiculus and Heliophora orbicularis. 

This website recites a legend that Heliophora are actually coins left by mermaids! I wasn't able to verify it, but it does sound reasonable (as a legend of course. Mermaids aren't real.. :-) )

What is going on with all of these crazy flanges??? Its not really been shown exactly what they do. Studies suggest that they might be related to feeding or play a role in keeping the animal from being swept away. (more on that below)..

This species has actually been studied in the field by Joe Ghiold in a paper published in 1985 (note that it is Heliophora, not Rotula as indicated)

His work seems to suggest that these feed like other sand dollars, i.e. in the sand on the bottom. Ghiold suggests that the spines may further function to facilitate feeding. 

Also of interest is that the plates which form the perimeter of these animals seems to grow a LOT faster than the more proximal areas. 

Some members of the genus Heliophora get kinda CRAZY... 

This image borrowed from this Excellent French site: Sciences de la Terre et de la Vie. Photo by Coco CHATAIGNER

3. The genus Rotula. Last but not Least! The scientific name "Rotula"is Latin for "Little Wheel" There is one spectacular species here: Rotula deciesdigitatus. I believe the species name refers to "deci" or 10 in conjunction with "digitatus" or digit referring to the number of flanges or projections. 

So the name literally means "Little Wheel with 10 digits"

Note that in this species there are TWO BIG holes!! These are what's called LUNULES. While these have not been specifically tested, an earlier post I wrote summarized how these holes (the lunules) were thought to prevent sand dollars from being gaining "lift" and being "blown" away by water current!!

And that still does not explain the MANY weird "fingers" along the edge! and on only one side! 

I managed to snap a cool shot of a specimen in Paris awhile back showing the oral side of one of these with ALL the spines or "hair" present...

Living sand dollars are covered by "hair" which are in fact tiny spines that move food to the mouth. 

                             

Here's a video of a sand dollar (but not Rotula) with said spines in full motion!  This is the oral side where the mouth is located.  

Even for sand dollars, these critters are very odd! Many evolutionary and functional biology questions! What are the flanges for? How do they develop? Why ONLY in this group???  Is there something unusual about the environment that is associated with these flanges and shapes???

These sand dollars have been known since the 19th Century and yet we know next to NOTHING about them (relative to their more northern counterparts). These sand dollars are seen throughout hobby websites and are collected by enthusiasts! And yet we know very little about them.

 They present many tantalizing and interesting questions to the future marine and evolutionary biologists! 

Deep-Sea Poop, Amoebas, Basket Stars, Pinwheel Crinoids and MORE! Pics from the NOAA Deep-sea Photo Archive!

Gulf of Alaska 2004 Expedition. NOAA Office of Ocean Exploration 

This week I have been researching images from deep-sea video on the home page for the NOAA Photo Library, which has housed ALL of the deep-sea and other imagery from NOAA's deep-sea expeditions since 2003, including those of the Okeanos Explorer!

Many of you know that I have participated in the last two R/V Okeanos ROV dives as an onshore advisor. I often identify asteroids (i.e. starfish) and provide other information as I am able. I've only helped them out since 2013 but found lots of their images useful for my research.

You can find NOAA-Okeanos dive screengrab recaps on my blog here for 2013 and here for the recent 2014 dive. 

Those of you on my Twitter account (@echinoblog) have been watching me post links to various pictures as I have been reviewing these pics.. There are literally THOUSANDS of pictures of deep-sea biology, geology and history !!!  Who would be crazy enough to go through all of it one by one???  Yes. Me!

So, for your education and infotainment I have cherry picked many noteworthy images and have showcased them below. (note that ALL images have original links below them)! Enjoy!

Giant Amoeba Houses??
Here's a cool structure made by a giant amoeba called a xenophyophorean! (deep-sea Galapagos) Take a moment to consider that a UNICELLULAR organism could have made this! (and yes, they will eat proper animals!)

From the 2011 NOAA Okeanos Explorer Program, Galapagos Rift Expedition 2011 

But in contrast, what about this from Indonesia??? A Mystery?? Another xenophyophorean?? 

From July 2010 NOAA Okeanos Explorer Program, INDEX-SATAL 2010

Basket Stars Behaving uh... badly? 

What is going on here? I've honestly never seen TWO basket stars so close to one another. What are they doing? Fighting? Doin teh sex? The gorgonocephalid equivalent of a backrub?   Only they know for sure.  (North Atlantic)

From Lophelia II 2008: Deepwater Coral Expedition: Reefs, Rigs, and Wrecks 

Brittle Stars Doing Crazy Things! 

From the Atlantic... Probably just filter feeding, but I don't know that I've ever seen so many of them with their arms all curled up like that just FLAT on the sediment. Weird.

From the Lophelia II 2008: Deepwater Coral Expedition: Reefs, Rigs, and Wrecks 

and more of the same...

from Lophelia II 2008: Deepwater Coral Expedition: Reefs, Rigs, and Wrecks 

Here is what we call in science "a fancy pants brittle star" (note the gorgeous red and white pattern though) on a really extended whip coral (aka antipatharian). Video from the Bahamas in 2009. 

From Bioluminescence 2009 Expedition, NOAA/OER 

And still MORE!

From 2009 Bioluminescence 2009 Expedition, NOAA/OER 

PIN WHEEL CRINOID?? 

A cool looking "pin wheel" stalked crinoid (Hyocrinidae) from Indonesia, a new species currently being worked on by colleagues in Paris. This is what it looks like "open"

From NOAA Okeanos Explorer Program, INDEX-SATAL 2010 

and curiously, this species retracts its arm in repose like this! As the kids say these days "That is pretty whack! "

From NOAA Okeanos Explorer Program, INDEX-SATAL 2010

BIG PACKS OF FILTER FEEDING ECHINODERMS! 

Stalked isocrinid crinoids! From the Marianas Arc, Pacific Ocean! All turned into the current!! 

 Image courtesy of Submarine Ring of Fire 2006 Exploration, NOAA Vents Program 

Also from the Marianas Arc, Pacific Ocean: A crazy huge field of basket stars (Gorgonocephalidae)..

Image from the Submarine Ring of Fire 2006 Exploration, NOAA Vents Program 

Some translucent Swimming Sea Cucumber intestine showing POOP?? 

 from NOAA Okeanos Explorer Program, Mid-Cayman Rise Expedition 2011 

Is this Sea Cucumber Poop??
Exotic Indonesian Sea cucumber poop?  Or possibly from an Acorn Worm? (below)

 From NOAA Okeanos Explorer Program, INDEX-SATAL 2010 

From NOAA Okeanos Explorer Program, INDEX-SATAL 2010

Deep-Sea Urchin POOP! 

Here is a great shot of an Echinothuriid urchin (aka the pancake or tam o shanter urchin) taking a poop!! A Gulf of Mexico species. Contrary to what the labels on the website say, this is defecation and NOT gametes being released.

NOAA Okeanos Explorer Program, Gulf of Mexico 2012 Expedition 

 Deep-sea Urchin Poop! 

NOAA Okeanos Explorer Program, Gulf of Mexico 2012 Expedition 

and a special non-echinoderm poop bonus! Acorn Worm POOP! 
Images from Indonesia.. Worms leaving unique castings in the sediment...

From NOAA Okeanos Explorer Program, INDEX-SATAL 2010 

From NOAA Okeanos Explorer Program, INDEX-SATAL 2010 

What I hope is that this will provide a spotlight on NOAA's very EXTENSIVE library of images!

MANY valuable and interesting things in there! Enough for many more posts. But what's most amazing? A lot of it is UNPUBLISHED stuff!!

But its hard to make a guess as to what kinds of things you will find (sometimes because you don't know what you are looking for)  This provides a taste of the diversity and abundance of tantalizing images. Sponges! Corals! Worms! Even protists!
                              

Sea Cucumber Skin Up Close! Bizarre & Beautiful!

Thelenota ananas Via Wikipedia commons. Photo by Nick Hobgood

Cool Crowdsourced Photo time! This week..some gorgeous closeups of the neat skin textures on tropical sea cucumbers!

Some of these give you an idea of how colorful and unusual the skin in sea cucumbers can be. This one is called  Thelenota rubolineata (the species name literally means "red lines"). This is an example of what the whole animal of one of the pics below looks like...

What do they feel like? Sort of soft and rubbery. Firm. And yes, people eat these species...

Here's a nice roundup of similar closeup photo essays of other echinoderms 

1. Here's the one for Up close Starfish! 
2. Another one showing close ups on Crinoids (aka Feather stars)
3. COLORS! in brittle stars! 
4. Crabs that live in sea cucumber anuses! here.
5. Worms & Snails that live on sea cucumbers! here. 

Below.. you will find many different close ups of the skin of sea cucumbers.

this one is Thelenota I think...

Some striking full body pics...

The Colorful Challenge of Identifying Fromia monilis, an Indo-Pacific species complex!

From Wikipedia! 

Identifying animals is tricky business.

The other day, I was helping some folks out with an identification of a starfish they had photographed diving, but I stopped short of giving them the full species. "Why?" they asked. "Isn't this just the the XXX?" (they quoted the most common and easily identified species).

"Well.  Its complicated."

Hard to explain these things in a a few lines on Facebook or on Twitter so I thought I would take an example of how complicated the whole taxonomy and identification process is, using a widely photographed example, a starfish called Fromia monilis.

F. monilis occurs widely throughout the Indo-Pacific. It goes by many common names, Necklace star, Tiled star, Candycane star, Peppermint star, etc.  Scientists don't use those names because they're so inconsistently used and often because its a contrived name in a field guide, created as a convenience for readers.

This species is often seen in the wild and is a common species in the aquarium trade. You can see it in shallow-reefs from Okinawa to New Caledonia, in the Philippines, Indonesia, etc. and over to the edge of the Indian Ocean.

Bottom line: This species is distributed over a VAST area. Because it does, the range of variation (discussed below) is likely to be greater.

F. monilis is a bright red and white species with a distinctive color pattern. The plates on its body surface (i.e., the many circles and shapes you see on the body) are also pretty diagnostic. Most of these starfish are about 2-3 inches (about 5-6 cm) in diameter. So far so good.

Here is what I would say is the most commonly encountered and "typical" form of this species.

From Wikipedia. Here

But bear in mind, that often times, as biologists (such as myself) who specialize in describing and identifying these species, what we often end up working with is a specimen like this...

The dry specimen isn't as impressive as the real, living color one of course, but specimens like this are extremely useful for understanding the species definitions, evolution and ultimately, the taxonomy of these animals.

Some of these specimens have been in museums for, literally hundreds of years and remain essential to our understanding of how these species are defined.

Many of these species get distinguished by fine character differences on these specimens. Some might vary by plate pattern arrangements, or by the number of spines present on the underside, or the particular shape of granules present on the surface.  Its often difficult to synch up these characteristics (i.e. the species definitions) with qualities of the animal when it was alive.

BUT, because of dry specimens above, we can usually look at a specimen like this crazy thing below and tell that it is STILL Fromia monilis.

                 

Why?

Specimens in museums, accumulate over time and can be very abundant, giving us an idea of the natural VARIATION of a species. Size. Body forms. Aberrant shapes. etc.

So, you know how, some people have blond vs. brown hair? Or how some people can roll their tongue or perhaps more exceptionally,some folks have an extra toe or finger? Well, this kind of variation is present in all species and can make understanding classification and understanding evolutionary relationships...interesting.

For a species that we have virtually no understanding of, any character variation (without seeing its presence in the population) might be used to distinguish a separate species. Without an understanding of this kind of variation (or having population genetics data of course), someone who has never seen a human being before could separate me from Morgan Freeman as a different species. 

In the case of the above specimen of Fromia monilis, having seen MANY other specimens of this species, and understanding (we think?) the variation at play,  we know that most known individuals have 5 arms that don't bifurcate. The bifurcation is perhaps due to an attack or some damage during the animal's life time. The extra rays are just an unusual trait, perhaps equivalent to a person with an extra finger. 

Color in the individual above is also consistent. Red disk with red armtips. White in between. Okay. What could be more unusual than the 7 rayed crazy thing above??

Enter the 21st Century (and late 20th Century) and the era of Flickr and digital cameras ALL OVER THE WORLD!

So remember how the "typical" Fromia monilis had that particular color pattern??

What happens when you don't have the red color on the armtips?? Could this be a juvenile? (no size indicator on this pic unfortunately)?  This specimen is from Indonesia. Could these vary by region?
The one above (w/the red disk) is from Borneo.

Is this the same species? But simply with a different color pattern?? Or a different species??  Some species of starfish are thought to vary by color based on their food, does this one as well??  How important is the color as a feature in identification?

The same questions here. Color patterns vary even more drastically. No red on the disk, but there IS red on the armtips! The patterns are a little different?  Is this variation? Size? Or a new species? This one is from Lembeh Strait (Indonesia). 

This one from Papua New Guinea. Same color pattern as above. 

Here is a Fromia sp from Thailand. Color and plate patterns are different. Is this a new species?? Or the same species (F. monilis) showing the starfish equivalent to having lactose intolerance? Or blond hair?

Here is another closely related species, Fromia nodosa which occurs primarily in the Indian Ocean. This species is primarily distinguished based on the larger and more prominent round plates running down the radius of each arm. But it looks familiar, doesn't it??

This individual is from the Maldives (tropical Southern Indian Ocean). It shows the same pattern as F.monilis above and the distinguishing characteristic is kind of variable itself. In other words, it doesn't always hold up.  Does that mean it should just be consolidated into F. monilis??

Here's another indivdiual of Fromia nodosa, also from the Maldives. On both of these individuals, we also see the marginal plates as larger and uneven in one but NOT the other?? 

This one is from Thailand... Mayyybe?  its F. nodosa?? And what's going on with the dark armtips???

This strange thing is from the Philippines. It adheres to the definition of Fromia nodosa (big radial plates, etc.) but its a different color (or at least I assume this is not some photo artefact)!!

And then to make it even MORE confusing.. we have these things from the Red Sea and adjacent areas...

I initially thought this was Fromia monilis but in fact, they might actually be a separate, already established , but this species might actually be a species in a poorly known genus called Paraferdina. Further examination of specimens and research is needed to figure out which one is which... This specimen is from the Red Sea.

This one is from Egypt. The color pattern is familiar but the plate patterns on the arms?? Very different and yet, similar... F. nodosa? F. monilis? Paraferdina???

..and so on...

This is mainly to demonstrate the limits of how the colors and patterns get complicated quite quickly.

And yes, at some point, someone may work this out.. Lots of diving and subsequent DNA lab time. Plus looking over photos and museum visits! Woo!

But this also explains why scientists, such as myself,  are often more reluctant to give you a full species name for a picture when its sent for identification without a specimen. Are these one species? MANY species? Which ones correspond to pre-existing species?

Falling back on the one, most common name can often disguise the truly rich diversity in these wide-ranging, closely related species which are only now, just becoming understood. I argued that this was also the case with the "Bobbit worm" (Eunice aphroditois)

So, yes. Knowing more doesn't necessarily give you all the answers, but it does give you some pretty exciting questions! 

5 EPIC Deep-Sea Giant Isopod (Bathynomus) Observations from JAPAN!

From the Toba Aquarium's Twipple Account

Since my trip to Japan, I've been watching a LOT more social media from Japan. Their culture, for many reasons, has a deep appreciation of ocean life, especially of invertebrates. The weirder and the more unusual, the better. 

Japan is an ocean-nation and as such, via fishing, swimming, and etc. their country encounters one of the richest faunas of invertebrates anywhere in the world.  Japanese pop culture has recently seen a HUGE uptick focusing on interest in deep-sea animals, especially ones like the Giant Isopod: Bathynomus! 

This is in part, due to the various aquariums which have had this species on display, including the Toba Aquarium and the Numazu DeepSea Aquarium. 

My thanks to Dr. Davin Setiamarga, University of Tokyo for his help with the Japanese!  below...

Defining my Terms. What Species of Bathynomus? 
In the big world of the Internet, its easy to start dropping names. Not many taxonomists, and too little information. So, let me take a moment to talk about diversity in "giant isopods" aka Bathynomus.

Bathynomus is a genus of deep-sea isopod which occurs throughout the Atlantic, Indian and Pacific oceans, roughly between 200 to 2140 meter depths. Isopods are of course, crustaceans. You may be more familiar with their terrestrial counterparts which go by many common names: "potato bugs", "rollie pollies" or "wood louse". But they're all members of the same group of crustaceans, the Isopoda.

Its easy to get caught up with the excitement associated with the most famous of all the Bathynomus species, Bathynomus giganteus. It is among one of the largest of marine animals and has an easy name to remember. Its species name literally means "Gigantic" Bathynomus.

There are about 18 species of Bathynomus occurring all around the world. According to an account by Lowry & Dempsey in 2006, Deep Sea Benthos (here)  they divide the various species into "Giants" which only reach 150 mm (about 6 inches) and "Supergiants" which reach up to 500 mm (almost 2 feet long!).

Yes. They can get to be bigger than a CAT.

B. giganteus, which occurs only in the western Atlantic is a "Supergiant". About half of the known species are "supergiants". A great summary to B. giganteus was written by the famous (now retired) Kevin Zelnio here, from many years ago..

The Japanese species, Bathynomus doderleini gets to be a decent size. About the length of a hand or foot. But it is apparently collected with some abundance in Japan and as such, has been put on display in several aquaria, permitting many interesting things to be learned about its biology.

There was one account earlier this year of an individual (apparently B. giganteus brought from the Gulf of Mexico) at Toba Aquarium which famously refused food for FOUR YEARS before it finally died in 2013.

From the Toba Aquarium Twipple

Interesting Names of Giant Isopods in Japan
The Japanese have a surprisingly consistent naming system used in labelling animals. As far as I can tell, this system is used in addition to the standard Latin names used for various significant species around the world. I've discussed some of these for starfish here. 

The popular term for Giant Isopod in Japanese is the word for the armor worn by shogun! Gusoku!  You can sort of see the resemblance: the overlapping plates and the helmet, etc..

The  name for Bathynomus doederleini, is Oo gusoku mushi

オオグソクムシ(大具足虫)
"oo" basically means "big", "guosku" refers to the armor of the samurai. and "mushi" refers to "many legged insect", "bug", or "critter"

From the Numazu Twitter pics

There is actually a separate name for the Atlantic Bathynomus giganteus, Daioh-Gusoku-mushi which roughly translates to "Grand King Armored Critter" ("dai" means grand or BIG).
ダイオウグソクムシ(大王具足虫)

What's that? You want MORE??? here's a bunch of amazing observations, spied via social media and etc. about everyone's favorite deep-sea isopod! Some biological. Some cultural...

5. Bathynomus feeding.  
Here is a tank in Japan filled with what is presumably Bathynomus doderleini, Watch the fish put in at 0:15-0:20 then, followed by FEEDING FRENZY and subsequent flesh-free fish skeleton!! Forget piranha.. throw James Bond into a pool full of these sometime!


4. There is a surprising abundance of Japanese Bathynomus products
I gotta say. They KNOW a good thing when they got it!!  I'm an echinoderm fan, but I respect a culture that loves deep-sea crustaceans!

Oh man. I don't even know where to start.

• Stuffed plushie toys (3 sizes   There are gold & silver variants
• Tiny candy & bottle top toys
• various "designer vinyl" kaiju toys
• Mobile iphonecase (in silver AND gold!)
• White, translucent white plastic Bathynomus figures/statues
• Keychains
• and of course, the Numazu Aquarium exclusive SOCKS! 

                                     

Here was one special item displayed by the Toba Aquarium, a glassworks Bathynomus model!! Wow! 

3. People EAT Bathynomus??
Yes. The full story is over here at Rocket News 24.  From what I've seen, this tends to be only B. doederleini, and not the Atlantic B. giganteus.

I only add that Bathynomus is probably NOT a good animal to depend on as a sustainable food source. But according to my colleagues, yes they are edible and not surprisingly, they taste like crab. and are pretty crunchy. Mostly they seem to be deep-fried. But I've heard they also eat them as sushi.

Video report in Japanese is here. But you'll get the idea.

2. Bathynomus Molting
Its not a secret that crustaceans molt. Crabs, lobsters, shrimps. All of them shed their exoskeleton as the body grows. And yes.. isopods also molt. Its been observed in more conventional species.. But has it ever been observed in Bathynomus?? (I couldn't locate an account but maybe it is out there?)

But here is something from the Toba Aquarium's Twipple Account (Twipple is a photohost service).  An AWESOME sequence of a deep-sea Giant Isopod undergoing a MOLT!

How many times do you get to see THAT??

First photo was recorded at 9:21 AM (Japan Standard Time),

From Toba Aquarium Twipple

This took place at about 10:00 AM. You can see more of the latter part of the exoskeleton beginning to come off..                                  

From Toba Aquarium Twipple

Based on other pics in the sequence, it got that older bit off around 2pm (JST). This is the fully removed latter half (new skeleton is brown) by about 5pm.

From Toba Aquarium Twipple

1. Bathynomus Brooding Juveniles! I thought this was amazing. So, I am not a crustacean biologist, nor am I one who knows everything there is to know about deep-sea isopods, but I did a non-trivial search in the literature for an account of Bathynomus bearing live young and I couldn't locate anything.

The Atlantic species. B. giganteus broods eggs, and some terrestrial isopods brood, so brooding juveniles in this species is not a big surprise. Its not clear to me if the Atlantic "gigantic" species does this.

But, clearly, this Japanese species does this. Priceless and awesome.

From the Numazu Aquarium's Twitter Account

There is VIDEO OF THIS!!!!

Here's one of those baby isopods... Not sure of the exact size..but looks to be about 1.0 cm long based on some of the other pics.. Awww...,

From the Numazu Twitter pics

and finally, BONUS!  a common question I always get, can Bathynomus roll up into a ball like their smaller, terrestrial cousins? 

From the Toba Aquarium Twipple

yes. 

(with the disclaimer that these are species kept in aquaria, which may provoke unusual behavior not typically seen in wild populations)

Whew! How can Japan LOVE a crustacean so much??? 

From this website