Tunicates, tunicates, tunicates....

[Anonymous]

I was wondering if anyone had any direct knowledge of tunicates at all. As far as I know most reefers consider them very difficult to keep. I think they're a beautiful animal, and if there was more info out there about their husbandry I might be tempted to keep one. Like sponges, they perform a valuable function of clarifying the water by filtering out bacteria, detritus, etc.

FWIW, tunicates (Subphylum Urochordata) are more closely related to us than any other invertebrate!

 

[rabagley]

I would check out Steve Tyree's stuff at http://www.dynamicecomorphology.com. He's very much into using sponges and tunicates as "skimmer replacements", though he tends to use the term "sea squirts" to refer to tunicates depending on his audience. In spite of his common terminology (like many aquarists, I strongly prefer the biologist's names for creatures), his research is some of the best for identifying particularly hardy and wasy to keep species of both sponges and tunicates.

Tunicates have one of the most amazing lifecycles, with a real spinal column in the larval stage before settling down to become a sessile filtering animal. Absolutely fascinating stuff IMO.

Regards,
Ross

 

[Anonymous]

Ross,
It was Steve who got me interested in them

He was at our local reef club meeting, and I thought his talk was very interesting. If anything, it's another very cool animal we could be keeping in our tanks. Just wanted to gauge the interest at RDO.

The juvenile stage of tunicates looks just like a lil' tadpole. The thing we share with them is a notochord, along with all other chordates. Some of the Urochordates are pelagic too.

 

[Anonymous]

I had one come in as a hitchkiker on a colony of Tubipora a few years back.
It was pretty much buried in the colony originally so it was tough to id at first.
My particular species ( I believe there are over 2000 ) did very well in a skimmerless tank dosed with phytoplankton daily. Unfortunately it succumbed to heat when areas of Chicago had a 3 day blackout during a heatwave.
At the time Bill Rudman had an interesting item on them but that link no longer works ( I'll see if I can find a reference for it elsewhere ) also just saw an interesting Dutch Site on Ascidians:

http://www.ascidians.com

Regards,
David Mohr

 

[Anonymous]

I have some clear ones hidden uder a few pieces of LR.

 

[Unarce]

I used to have several dozens of these guys in my sump. After I restocked the sump with turbo snails, they were all gone.

 

[Anonymous]

I'm just about ready to mark this one for archiving, let's get more good info in here!

 

[Anonymous]

Unfortunately Bill Rudman's article is no longer available but he does have a brief one on his Seaslug Site:

http://seaslugforum.net/ascidian.htm

Also found another hallway decent but brief summary at:

http://www.meer.org/M20.htm

and this one that's fairly detailed:

http://www.tunicates.com/

Most Sites tend to be regional species as opposed to details on all species.

Regards,
David Mohr

 

[hdtran]

Matt,

In my dim distant past (way way past), like the early 70's, I vaguely remember that tunicates (along with echinoderms) were classified into Chordata, despite the lack of a spinal column as adults.

Is that still the case, or is my memory playing tricks on me, or have they been reclassified outside of Chordata?

Hy

 

[Anonymous]

Actually they are distant relatives both posessing a common gene called Dll.
Researches have determined that the common gene dates back to about the Pre-Cambrian Era. This gene directs cell to create organs that bud off from the main body axis, such as legs and antennae. This gene is associated in siphons of adult Ascidians, and in the spines and larval tube feet of Sea Urchins (Echinoderms). Some Cambrian echinoderm-like fossils have been suspected of being of the phylum Chordata. So yes there is still some confusion. :wink:
Sorry Matt.

Regards,
David Mohr

 

[Anonymous]

My most recent Invertebrate bio book classifies Tunicates (Urochordata) along with Vertebrates and Cephalochordates as the only members of the Phylum Chordata. All chordates possess a notochord and pharyngeal (sp?) gill slits at some point in their life cycle, IIRC. Echinoderms don't possess these, afaik. Of course taxonomy is becoming more based on genetics as David points out rather than on physical features, so that could kind of change the classification a lot.

http://www.cartage.org.lb/en/themes/Sci ... ostome.htm

Echinoderms, Chordates, and some others (Sipunculans ?) are grouped together as Deuterosomes, because of the way the egg cell splits. Annelids, molluscs, arthropods, and virtually all other invertebrates are grouped together as protosomes for the same reason. Some phyla don't fit into the proto-deutero thing though, like Porifera. I'm basing this all on memory, so David might be able to clear this up a bit better.

But to sort of answer your question, echinoderms are pretty closely related to us.

 

[Anonymous]

My most recent Invertebrate bio book classifies Tunicates (Urochordata) along with Vertebrates and Cephalochordates as the only members of the Phylum Chordata. All chordates possess a notochord and pharyngeal (sp?) gill slits at some point in their life cycle, IIRC. Echinoderms don't possess these, afaik. Of course taxonomy is becoming more based on genetics as David points out rather than on physical features, so that could kind of change the classification a lot.


Echinoderms, Chordates, and some others (Sipunculans ?) are grouped together as Deuterosomes, because of the way the egg cell splits. Annelids, molluscs, arthropods, and virtually all other invertebrates are grouped together as protosomes for the same reason. Some phyla don't fit into the proto-deutero thing though, like Porifera. I'm basing this all on memory, so David might be able to clear this up a bit better..

Damn I hated taxonomy, I just liked to sit on the boat drinking beer or diving. Notochords, visceral clefts and arches, pharyngeal gill slits........aaaarg. Much is also based on reproductive organs, dna, fossils, etc.
We're openning a real complex discussion here and it's getting to my bed time so let me put this off until tomorrow night and I'll delve into this more thoroughly.

Regards,
David Mohr

 

[Anonymous]

Ummm Riiight

 

[Johnsteph10]

Just imagine trying to memorize what structures come from which pharyngeal gill arch in diffrent animals vs. humans and then having to research why.

argggggggg. bad memories.

John

 

[Anonymous]

Well let's see if we can clear this up a bit or make the picture muddier.
I'm going to post this in series as I don't want to get timed out.
The traditional or Linnaean system of Taxonomy divides living things into 5 Kingdoms. They are grouped into categories based on how similar they are. Many of the taxon are based on morphology or anatomical similarities. With the advent of genetic research may species thought to be similar in appearance are more distant than previously thought. Because of this the Linnaean System does not accurately tell how ancestrally close members of a particular taxon are though it does give a good systematic approach to discussing and naming known organisms. Since this system has named and categorized all known species we can now modify the taxa according to genetic information.
In the Kingdom organism are distiguished according to cellular characteristics and methods of obtaining nutrition.
We'll be considering the Kingdom of Animalia.
Animalia are organisms that ingest nutrition.
You can also have Subkingdoms but we'll skip that.
Both Tunicates and Enchinoderms are Members of the Kingdom: Animalia
Animalia is then divided into Phyla according to basic, physical similarities.
We'll be considering the Phylum Chordata.
This Phyla is now divided into 3 Subphyla: Vertebrata ( animals with spinal chords ), Urochordata ( invertebrates ) and Cepalochordata ( invertebrates ).
Phylums are categorized into Classes in which members are grouped according to their skeletal system, environmental adaptations and their reproductive systems.
Classes are now divided into Orders in which organisms are grouped according to closer morphological similarities.
Orders are then divided into Families which are grouped by even more detailed morphological traits.
Families are now divided into Genera for which organisms are grouped by even closer similarities.
Lastly the Genus is divided into species.
Now let's get to the Phylum Chordata.
All Chordata have bilaterally symmetrical bodies. At some point in their life they have gill pouches or gill slits to obtain oxygen in a liquid environment. Chordates also have a notochord, a stiff cartilage that runs under the dorsal surface of their body.
Subphylum: Cepalochordata are marine filter feeders closely ancestral to Echinoderms.
Subphylum: Vertebrata when the notochord is replaced by a complex spinal chord in the embryonic stage.
Subphylum: Urochordata which contains the 2000 known species of Tunicates or sea squirts.
(end of first post.)

 

[Anonymous]

Hopefully this gets added at the end of your post, since it looks like we're typing at the same time here.

Just to clarify on my post above...

All bilaterally symmetric animals are classified as either Coelomates, Pseudocoelomates (includes Rotifers, Nematodes), or Acoelomates (includes Flatworms and Nemerteans). I'm not even going to bother explaining what a coelom is. Anyway, coelomates are divided into Protostomes and Deuterostomes. Humans, and vertebrates, are Deuerostoms, along with Hemichordata, Chaetognatha, Pogonophora, Echinodermata, Cephalochordata, Tunicata, and Vertebrata. These are listed in order of their proximity to Vertebrates in the taxonomy.

Later I'll post some details about each of these phyla. It's very interesting how alien they appear yet how closely related they are.

 

[Anonymous]

Now we'll examine some characteristics of Chordata. As mentioned in previous posts the most distinctive morphological features of chordates are the notochord, nerve chord and visceral clefts and arches.
The notochord is an elongated rod like skeletal structure ventral to the nerve chord and dorsal to the gut tube. The notochord should not be confused with the vertebral column or backbone of adult vertebrates. The notochord appears early in embryogeny and plays a role in organizing and promoting the embryonic development of nearby structures. In most adult chordates the notochord disappears or becomes highly modified. The nerve chord of chordates develops dorsally in the body as a hollow tube above the notochord. In most species it differentiates in embryogeny into the brain anteriorly and the spinal chord that runs thru the trunk and tail.
In the Subphylum Urochordata ( tunicates ) the structure of the notochord is present only in the larval, swimming stage of the animal and does not extend to the head. The visceral ( pharyngeal ) clefts and arches are located in the pharyngeal part of the digestive tract anterior to the esophagus and behind the oral cavity. The visceral clefts appear as several pairs of pouches that push outward from the lateral walls of the pharnyx eventually to reach the surface to form clefts which are continuous slit like passages connecting the pharnyx to the exterior. The soft and skeletal tissues between adjacent cefts are the visceral arches. In the nonvertebrate chordates such as tunicates and cephalachordates the clefts and arches form elaborate straining devices designed to capture small food particles from the water column.
In the next post I'll try to show some of the similarities between Enchinodermata, Porifera and even Mollusca that have at times led them to be classified in the same Phylum.
(end of second post)

 

[Anonymous]

I'm going to continue this tomorrow as I have a day off and I'll let Matt post his piece on Deuterostomia, etc. There's already a problem with the classification of Tunicates as Deuterostomia and that's the state of flux in taxonomy at the moment but I need some beauty rest.
Catch ya tomorrow.

Regards,
David Mohr

 

[Anonymous]

This is all well and good, Mr. Mohr, but.. hey, you're not related to Jay Mohr, are you? Cuz, if you are, that guy is funny as hell! Where was I..? Oh yeah, taxonomy is all well and good, but what can you offer in terms of husbandry techniques? I'm thinking that if you can keep sponges alright, you might be on the right track for tunies.

 

[Anonymous]

SM, there's just not much to go on. Rob wouldn't even mess with them.

I kind of consider sponges to be an equivalent tool, and the HH types are fairly hardy and spread fast. I've never noticed a HH tunicate, but apparently some have. It would be great if we could get some decent #s of these and share them amongst us hobbyists.

In any case, I think the taxonomy stuff is interesting.