Metamorphosis

There are lots of changes going on over here, especially on the job scene. Change is a bumpy process; sometimes it makes me uneasy about unknowns, often eager for new things, and frequently ambivalent from both.

Over in the tarantularium, I noticed that one of the crickets was also going through some changes. The plastic wall of the box is the reason for the slightly blurry quality of the photograph. There’s really no excuse for all the bad puns and silly jokes about Superman, strippers, training wheels on bicycles et cetera, except for the otherwise dryness of the subject and the stressed busyness of my recent days.

Our own maturation is not nearly as profound as those faced by the holometabolous, such as caterpillars that metamorphose into butterflies. Hemimetabolous insects like these crickets have fewer structural differences between the nymphs and adults; in addition to becoming sexually mature, they also develop full-size wings. (The “teenage” crickets just have stubby little wings, not even as useful as training wheels on a bicycle.) The male below has just molted. His exoskeleton is still soft and pale, and the wings have not yet been fully inflated. A little while later, the wings were fully extended, and his exoskeleton (shell) had “cured” and darkened to a deep brown.

Molting seems bizarre to those of us who have our structure support on the inside. (I imagine that arthropods would find vertebrates strangely inside-out.) But climbing out of your skeleton is vital when it covers you and you need to grow — think of it as being analogous to having to buy new shoes for growing children. The new, larger exoskeleton is made before the old one is removed, and it is underneath, so therefore a bit wrinkled up. (Random thought: that’s probably why Superman wore a leotard-like costume under his Clark Kent suit; amazing the cape was never wrinkled –maybe it was some space-age fabric from Krypton.)

The first step is called apolysis, which is started by the release of ecdysteroid hormone messengers that cause the cuticle (hard, shell part) to be separated from the epidermis, the living cell layer under the cuticle. Once the old cuticle is popped loose, those cells release molting fluid into the space underneath the cuticle. Word buffs: ecdysis means to shed or strip, so a fancy word for a stripper (exotic dancer who removes clothes) is an ecdysiast.

On that entertaining note, we move to the next stage, the creation of the new cuticle. First the epicuticle (outside-most layer) is built by secretions from the epidermal cells, followed by the middle layer (technically the inner epicuticle) and the third inner layer, the procuticle. That sounds pretty dull, but once these three thin layers are created, then things get interesting. That molting fluid is activated and begins to dissolve the endocuticle, which is the much thicker layer between the procuticle and the epidermal cells. Material that is being dissolved is then recycled and used to build up the new cuticle. Just before the removal, the outside layer is covered in wax to help waterproof the insect. (No, not TurtleWax like you buff on your car, insect wax. But same general purpose.)

Once all that refurbishing is done, it’s time to “take it off, take it all off“. This is the tricky part, and every now and then a critter doesn’t quite make it. The insect gulps a lot of air (aquatic arthropods gulp water, naturally) and then contracts its muscles until the old exoskeleton cracks along the “seams” or edges of a few sclerites (sclerites are like plates in armor). Because all but the epicuticle was dissolved, the remaining cuticle is actually rather thin.

Crack, pop, climb out, right? Not quite. Cuticle covers the outside of the insect, and also invaginates and lines other structures, like the anus and the structures of the head. Yes, they must pull their shells out of their butts and their faces. I’ve always imagined that pulling off old facial cuticle would feel something like engaging in a heavy-duty sinus-clearing session with the tissues. (“Invaginate” simply means that an outside layer is folded or turned in to create an inside layer, and yes, I know that invaginate and anus are an odd combination of words — I don’t make these things up!)

After the insect has successfully managed this feat, leaving behind the fragile husk of its old exoskeleton (now called exuvia) the new exoskeleton can be fully expanded, ditto the wings. Butterflies emerge from their crysalids with their wings folded up like umbrellas, and insects must pump hemolymph (insect “blood”) through the veins to expand them. The wings dry, and the exoskeleton cures and hardens in a process called sclerotization, which is similar to tanning.

The arthropod is now ready to face the world again, assuming it was able to find a safe place to molt. Molting is not only intrinsically dangerous, but it leaves the arthropod vulnerable to predation. Humans and others animals are especially fond of eating soft-shell crabs, which are crabs that, as you may now guess, have just molted. (Poem / lyric after the photo.)

[Photo description: newly-molted male cricket sitting atop a rock. He is a soft ivory color, and his wings are still crumpled up. The exuvia, or cast-off old exoskeleton is crumpled up behind him.]

METAMORPHOSIS

The time has come,
New information.
We’ve been waiting
For the transformation.

Changes happen every day
Respond in many ways.
Old days for new
Old ways to renew.

Working from the inside out,
Is what it’s all about,
Usually it’s an itch.
Sometimes it’s a bitch,

Getting stuck is hell
Midway tween the shells,
But don’t you scoff,
And ask, Can I pull it off?

Hey, it’s all we know,
Every body’s gotta grow.
Changes happen every day
Respond in many ways.

The time has come,
New information.
We’ve been waiting
For the transformation.

2 Comments

  1. 22 February 2008 at 0:35

    Heini liked this post!

    I think she likes your writing style… every bit as much as the subject.

  2. 2 February 2008 at 13:58

    […] what do Superman, strippers and training wheels have to do with arthropods? That was my recent post inspired by changes in the job scene and a cricket in the tarantularium. Susannah (AKA Wanderin’ Weeta) is also […]


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