Beautiful & Creepy Things about Tunicates! Echinoblog Off Topic!

Image by Leander Wiseman

Today, a little off topic time for some tunicate love!

For those who are not familiar, tunicates are actually members of the same overall group to which humans and all other vertebrates belong! A subgrouping, called the Tunicata within the larger phylum Chordata. Honestly, the relationship is pretty basic info which you can find with a quick Google search

Most times, tunicates are small, out of the way or encrusting (i.e., covering surfaces over a wide area) but can be very abundant, carpeting areas until nothing else grows there..such as this one (Botrylloides diegensis) which is an invasive in San Francisco Bay from Asia.

 Image by Luis A Solórzano, KQUEST

Under many conditions, tunicates are ugly and kind of bland colored things that are common components of fouling communities. Its species such as this one which earn the oh so lovely common name "sea pork"(Amaroucium californicum). And so, they get a bad rap. 

image by Jkirkhart35

But tunicates are often gorgeous and attractive animals. PLUS, they do weird and unusual (if kinda creepy) things! Let's go see! 

1. Some Basics
This shows two siphons: one is where water goes IN and the other is where it goes OUT.

Image by Arne Kuilman, from Anilao, Philippines

Food gets caught in the "Pharyngeal basket" (=the "filter" for its filter feeding) where it gets moved down to the stomach. A pretty simple overall anatomy. But note, it has well-developed organs that you would find in a proper animal.  This is important later...

From the Marine Life Information Network

This gives you a general idea of the animal as a whole (not sure if this is the exact same species but you get the general notion)

Image by Prilfish

 Basket Close ups! 

Image by Steve de Neef

Cross section! the space between the 'tunic" and the feeding basket

Image by "stupidhead"

Image by Star Tsai

INSIDE the basket!

Image by Eric Cheng

Image by Christian Loader

Image by Steve de Neef

2. Some Diversity... 
Some tunicates are individuals

Image by bybegone

Whereas other forms are colonial...

Image by Patrick Nilsson

Botrylloides magnicoecum from Australia. And yes, those are apparently the REAL colors.

Image by Leander Wiseman

Botrylloides leachi from Australia

Image by John Tumbull

Fantastic image by Pat Sinclair

Other tunicates are more....unusual in appearance (I think these are solitary)  BEHOLD! Sea Tulips! Pyura spinifera from Australia!

Here's only a few...

Here's a LOT of them

Image by Richard Ling

Another stalked tunicate, Oxycorynia fascicularis from Anilao in the Philippines

Image by Optical Allusion

Stalked GREEN tunicates! Same species? Oxycorynia fascicularis

Image by Mer Mate-Eunice Koo

And although I've been focusing on shallow water, I can't get past tunicates without the obligatory showing of the famous DEEP-SEA predatory tunicate (Megalodicopia hians) !! The IN siphon is modified into a mouth and the OUT siphon kicks out the tunicate poop!   Let's let the British narrator take us away!


3. The predatory tunicate is a great segue for the vice versa! People EAT tunicates. As I've outlined here.  Its called the "sea pineapple" among other things in Asian cultures, but different species (called 'sea violets') are eaten by Europeans..

Image by sjbutterfield2

MMmm........tunicates and kimchi....

Image by Mark Deibert Photography

4. Tunicates are a little creepy 
If tunicates have similar enough tissues (historecognition) ie. are similar enough two physically different individuals can physically FUSE together.

Why say it, when you can SHOW it?

the description from the video:

This video shows a fusion event in progress between compatible individuals of the sea squirt, Botryllus schlosseri. At the beginning, terminal parts of vasculature, called ampullae, which surround the colony, have come into contact (one colony is on the top right, the other on the bottom left, out of the field of view). The ampullae push into each other repeatedly, and finally the cell layers between two ampullae fuse, and results in both individuals sharing a common circulation. 
Fusion can best be seen on the top left, but occurs in several places in the region of interaction. The decision to fuse or reject is based on whether the two colonies 'match' each other, analogous to how humans accept or reject transplants.

See this essay for more.  But bear in mind, tunicates may look simple like sponges-but they aren't! 

Sponges don't have tissue, so those videos where they grind em' up and they get back together?

Not that hard for animals that are still essentially just colonies of cells. Proper ANIMALS with tissues don't typically do stuff like that.  The fusion shown in tunicates above?  That's like you and your family, suddenly fusing into one big amorphous pile. Squicky, eh?

Go here to learn more about this.

5. Where can I learn MORE about tunicates?
*Did you know that tunicates accumulate the metal Vanadium in their body tissues? go here to learn more.
*The Dutch ascidian Site! 
*The Tunicate Web Portal! 
*Will tunicates be used as biofuel? 
and my colleague Jarrett Byrnes writes a blog that often involves tunicates!

Starfish with Babies! Brooding Behavior & Pseudocopulation Revealed!

Today: BROODING Juveniles!  Wait, What?  No, NOT like this

Seriously! This is one of the top images that comes up in a Google search for "brooding"

I meant Brooding juveniles like THIS!

from the Smithsonian NMNH USARP

In other words, these are "baby" starfish that are cared for by the mother until they are ready to head off ont their own. Parental investment resulting in a succesful offspring. 

Sometimes starfish (and indeed most echinoderms) can appear kind of alien. No head. Mouth on the bottom. 5 part radial symmetry. Strange adaptations. All kind of weird sometimes.

So, I suppose its appropriate that the WEIRDEST of ALL echinoderm (and starfish) behavior is that starfish have this almost mammal-like (or at least, vertebrate like) behavior!!   Some starfish species will actually brood and carry little starfish just like the cutest little furry thing you can think of!

Now, most starfish have a fairly straightforward reproductive cycle.

Eggs and sperm are ejected from the males and females-they fertilize and go on to form larvae which swim in the water developing through different stages, eventually eventually settling down onto the bottoms and growing up to become proper "adult" starfish.

But many starfish species stray from that typical cycle, and somewhere between the time the sperm fertilize the eggs and the settled "babies" are established the whole life cycle CHANGES to give you this:

Yes. Tiny baby or small juvenile starfish which are held by the mother around the mouth! (this varies as we'll see). Why do some starfish do this?  And not the more 'typical' behavior?

Scientists have known about brooding behavior in several species of starfish since the 19th Century but only recently has there been the extensive observation and insight to finally piece together the complete story!

The Story of Leptasterias polaris
Information herein is based on a paper by Jean-Francois Hamel and Annie Mercier at Memorial University in Newfoundland. which you can find (here) in Biological Bulletin from 1995 (vol. 188: 32-45)

They studied the large, Arctic/subArctic 6-rayed starfish Leptasterias polaris which occurs in the North Atlantic, Arctic and North Pacific Oceans.

Image by Claude Nozeres  from the Canadian Registry of Marine Species

Hamel and Mercier's paper exhaustively studies L. polaris' complete reproductive cycle, which pretty thoroughly documents the reproductive behavior in this species.  Bear in mind, that this starfish has been known since 1842 and yet our knowledge of its reproduction has only come to us recently (published in 1995)!

Information on brooding remains of interest-but the behavior and its evolution is poorly understood.

1. PSEUDOCOPULATION

Figure 1 from Hamel & Mercier 1995

 As a prelude to the actual spawning there are massive aggregations of these animals. They're involved in an unusual behavior known as pseudocopulation. There's no penetration or combination of sexual organs, nor is there any actual spawning. The animals all just get together into a big pile. Sort of preparation for the main event.

Bear in mind, OTHER than during mating season (November to February), these animals all typically ignore or even avoid one another.

Many echinoderm species practice pseudocopulation which I've written about here. Its not always clear why different species pseudocopulate. But one thing seems clear: It helps the chances of their sperm and eggs get together.

2. Spawning! There were no pics of actual Leptasterias spawning, so here instead is a closely related Asterias. I have discussed this spawning on armtips position here. It is observed widely across cold water and tropical species.

Image by Tom Ashton

Spawning in Leptasterias polaris males begins as the water gets cold, about 2 degrees C. 

Sperm (male cells) are negatively buoyant, or in other words, they sink to the bottom and form sort of a film. The sperm then go dormant until they come into contact with the female's eggs..

3. The Female Pinwheel formation. Stimulated by the males, and following the deposition of sperm on the bottoms, the females proceed to eject the eggs onto the sperm so that fertilization can proceed.

The deposition of the eggs onto the sperm re-activates the sperm allowing them to combine and fertilize.

During this phase, the females adopt this "pinwheel" formation

From Mercier's L. polaris site

Here (from Figure 5 in Mercier & Hamel) we see a close up of eggs UNDER the female in C. Which then grow up into the cute as the dickens starfish in D.  Growth was after about 5 and half months.

4. After fertilization, development proceeds. Here's a summary panel of the different stages. The top row is the developing embryo. It continues through different stages until it reaches "J." 

At that point the animal is practically ready to move off on its own..

Figure 9 showing development from embryos to small starfish 

Interestingly, Hamel & Mercer found that the development proceeded on its own if the embryos were unbrooded.  They suggest that brooding is behavior which protects the embryos/juvenile starfish from debris and other materials. Animals observed in the field were clear of excess materials.

Protection was also a likely consideration since unprotected embryos/juvenile starfish were rapidly devoured by sea urchins or other grazing animals if they were not protected by the adult. 

 The whole cycle is sumarized in this convenient cartoon!

Figure 4 from Hamel & Mercier 1995

There were MANY more details! If the topic of brooding interests you I urge you to check it out!

BUT That's NOT the end of it!  

5. Brooding is diverse.  SEVERAL different species of sea stars brood. Almost all of them are either cold-water species, living in the deep-sea or at the poles. Sometimes brooding is in temperate water species.. But typically not in the tropics.

Brooding also takes different forms. The oral 'mouth' or gastric brooding mode is but one kind. Here is Diplasterias from the Antarctic!  MANY starfish in the Antarctic brood juvenile starfish!

from the Smithsonian NMNH USARP

For example, in the suspension feeding brisingids, the Antarctic species Odinella nutrix, broods babies  in special chambers made from the arm spines present between each of the arms.

There is the strange Japanese/Russian/North Paciic Trophodiscus (go here to see more) Juveniles are brooding on the TOP of the animal among the spines (called paxillae) that compose the surface of the disk.

Here is a living specimen. Image by colleague Yoichi Kogure!

Close up

And then there's Tosia neossia, recently discovered in Australia. This species broods but without actually keeping the babies physically on the body. They are kept spread out near the animal... See the orange dots in the picture below?  That's the juveniles...  I wrote about this species here.

Here's the tiny Tosia crawling larvae!

And in the deep-sea, there is the weird "sea daisy" Xyloplax!

And that's not to mention brooding in sea urchins, ophiuroids, crinoids and sea cucumbers! and MANY other invertebrates!  Starfish brooding is just the tip of the iceberg!

Feather Star Color Bonanza!

A key lime colored crinoid by Frederique Jaffeux, South Ari Atoll in the Maldives

This week, some brightly, eye-jarring crinoids in mind-blowing COLOR! What are crinoids, aka feather stars?  They are echinoderms that hold their feathery arms up in the water and pick food out of the current as it flows through/past them!  Want to learn MORE about crinoids? Visit this awesome site by Dr. Chuck Messing!

Purple and white feeding fan of a feather star from the Maldives!

Image by Bil Stohler

Here-some brightly colored blue feeding structures called pinnules are seen on the arm...

Image by mimimoyer

A gorgeous crinoid from Okinawa withdrawn into itself

By Okinawa Nature Photography

A stunning green crinoid from Okinawa.

By Okinawa Nature Photography (Shawn Miller)

Stunning orange..

Image by Henry and Tersia. Borneo.

Black and White on a red sea fan.

Image by Randapex

Macro of Blue Oxycomanthus arms. fr. Bali.

Image by Arne Kuilman

Blue crinoid in repose fr. Indonesia.

Image by Courtney Platt

Black & White Crinoid from the Philippines

Image by Mona Dienhart & Chris Lebas

There is a fish in this picture! Can you spot it?

Image by Arne Kuilman

A crinoid in a lovecraftian pose!

Image by Eddy Wong