Sea Squirts – Living On the Edge

Posted in Under the Sea on October 3rd, 2010 by MadDog
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On Saturday we went out to Magic Passage in Faded Glory.  This is the first dive that we’ve done with her since she rolled over and sank on the day we left for Australia. I was a bit apprehensive, because submerging your boat in salt water is not something that is good for it. There was a stong current coming through the passage into the anchorage and the water was wonderfully clear. Unfortunately, there was a thin layer of condensation inside my camera housing, so I got no images. I did not warm the camera and housing  to drive out any moisture before sealing it.

So, today I’ll show some images of a few of the very strange creatures commonly known as sea squirts. More properly called tunicates, sea squirts live just above the edge between invertebrates and vertebrates. Because I am so lazy I ripped this directly from the Wikipedia article on tunicates.

Most tunicates feed by filtering sea water through pharyngeal slits, but some are sub-marine predators such as the Megalodicopia hians. Like other chordates, tunicates have a notochord during their early development, but lack myomeric segmentation throughout the body and tail as adults. Tunicates lack the kidney-like metanephridial organs, and the original coelom body-cavity develops into a pericardial cavity and gonads. Except for the pharynx, heart and gonads, the organs are enclosed in a membrane called an epicardium, which is surrounded by the jelly-like mesenchyme. Tunicates begin life in a mobile larval stage that resembles a tadpole, later developing into a barrel-like and usually sedentary adult form.

There. That is probably way more than you wanted to know.

This is one sea squirt which you have seen many times before here in MPBM. It is Didemnum molle:

It is very delicate and floppy. It reminds me of a bag full of lettuce.

I still have some difficulty knowing for certain whether I am looking at a sea squirt colony or something else. I am pretty sure that this is a colony, but I can’t identify the species:

My resource book tries to cover all of the invertebrates of the Indo-Pacific region, so it contains only a tiny fraction of all species.

Again, I’m at a loss to identify the species, but I’m reasonably certain that this is a sea squirt colony. There is a bit of overlap in appearance between some sea squirts and some sponges; this complicates identification, at least for me, a rank amateur:

This is another bag-like sea squirt, though they are much smaller than the D. molle:

Just from these five images you can see the wide variety of forms. These colonies grow on little stalks which are not visible in this image. They look like strange little bushes growing on the reef:

Sea squirts are a hot topic in the field of medicine. Researchers have found chemicals which are effective treatments for various cancers. Other research indicates that there is quite a bit to learn from sea squirts which may teach us how to regenerate human organs.

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The bizarre parade of physical symptoms accompanying my grief and stress continues to march through my life. I wasn’t expecting this. For weeks, long before Eunie passed on to her reward, adrenaline was coursing through my body and giving me the shakes. Insomnia was my constant companion and still is. Three or four hours of sleep a night seems to be my limit. My toes feel like ice cubes and my ears are on fire. The backs of my calves feel very cold, but are warm to the touch. What’s that  all about? Some symptoms fade and are replaced by others. The daily small panic attacks have reduced in number and intensity. They have been gradually replaced by a permanently clenched jaw. I have to tell myself a hundred times a day to unclench and stop grinding. My jaw hurts.

I feel a bit silly complaining about such trivialities. Well, insomnia is certainly not trivial, so I’ll complain about that. I was taking Temazepam to catch a little sleep. When I finally got around to reading about it I discovered why that bit of sleep began to diminish as time went by. It’s a temporary fix and may end up causing more problems than it fixed, since it reduces the body’s ability to sleep naturally. Okay, so much for “better living through chemistry”.

Among my many fond memories I can relish the time when I could get a solid eight hours of peaceful slumber.

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