Shrimp molt

Most of Shimek's research is on various marine snail species, especially parastic species, and in that arena I would consider him to be a strong researcher. He has also done some work with sandbed infauna, like copepods. But, for most of his articles he just summarizes and accumulates material from grad-level marine invertebrate textbooks. This is a great service for a lot of people as it brings information that isn't available to most hobbyists to those who need it, but doing a book report on Moby Dick doesn't make you Herman Melville, ya know? ;)

Even still, I wouldn't mind if Shimek allowed open discussion of the experiments that he does on aquarium-related topics. He gets really defensive if anyone questions his methods or conclusions. For example, there's a recent thread over in his forum on RC where someone was smacked down right quick for displaying a lack of total confidence in his salt mix study. I don't get that response...what makes a strong research finding is the ability to respond to criticisms!
 
I found this in a round about fashion. Its a cancer study from the university of Shandong that I stumbled upon as a reference in another article I was reading.

"a. Molting Hormone

The clearest and most direct evidence reflecting the regulation of genetic expression at the level of transcription is the formation of "dilated vesicles " seen in the chromosomes of the salivary glands of the larvae of fruit flies and other dipterous insects. These vesicles appear one after another along with the development of the insects (The genetic transcription in the dilated vesicle zone is going on). Therefore, the "dilated vesicles" of polytenic chromosomes are regarded as the morphologic expression of essential molecules and development process---activation of specialized genes. Molting hormone can bring about the orderly emergence of the dilated vesicles of the chromosomes of the salivary glands of the larvae of fruit flies [4]. The cicada slough in traditional Chinese medicine is the skin of Gryptotympana atrata and it should contain molting hormone after ecdysis several times and eclosion. The experiment made by Sato proves the inhibition rate of cicada slough on the cancer cells cultivated extrinsically is 100% [3].

b. Thyroid Hormone

After an injection of thyroid hormone into an animal the increase of some RNA will be observed before that of the activity of the polymerase of RNA and that of a series of enzymes [9]. Although little is known about the mechanism of the compounding of RNA and proteins promoted by the thyroid hormone, it has been discovered that the thyroid hormone can combine itself with mitochondiae rapidly in cells to promote their biological oxidation. It can then change the functions of chromatins and intensify the compounding of RNA and various sorts of zymoproteins [9]. Indeed, the thyroid hormone can stimulate metamorphoses like rapid development and differentiation in animals [3]. Many facts have proved thyroid hormone deficiency has something to do with cancer. For instance, iodine deficiency is positively correlated with the incidence of mammary gland cancer in statistics [3]. c. Thyroid-Stimulating Hormone (TSH)

TSH comes from peptide hormone of the lobus anterior hypophyseos. Experiments on animals show when TSH is added to thin thyroid slices or whole animals, the absorption of iodine by thyroid cells can be stimulated by 500 times [10]. Besides, TSH can activate the adenylate cyclase on cellular membranes, so it quickens the formation of cAMP and increase cellular concentration of cAMP, which is one of the best inducers of the cellular differentiation of neuroblastoma [8]. d. Estrin"


The full text is available online at www.eciwo.sdu.edu.cn/medicine/f06.html

I'm not sure how much it helps, but it's an attempt at correlating iodine to the molting process.
 
I just wanted to run on the side of Boogie as far as Ron goes. Too often, IMHO, people praise his name. While he is a very intelligent man, his works often contain citings by papers that aren't peer reviewed. If 4 people write a paper on the feeding habits of so and so, it doesn't make them right just because there's 4 reports (on the other hand, peer reviewing by a scientific counsel doesn't always make it right either). I just feel that he throws his stuff out there too often without accepting the paper's limitations or is willing to admit that he was wrong. I read is I.O. paper too, and while it's information may have been correct, it had way to much of a "my tank crashed because of this, and yours will too" theme going for it.
 
Agreed. But wrt the original topic, I did a little reading last night. I had a chance to do some searching on all the databases that the Marine Biological Laboratory at Woods Hole has when i was there for a party, I mean meeting, in March. I skimmed it, then got busy. What I learned can be summarized as:
1) Much crustacean endocrinology is published in journals so obscure that even MBL doesn't get them.
2) Entry into the molt is controlled by 20E (20-hydroxyecdysone), under the control of MIH (molt-inhibiting hormone), and maybe methylfarnesoate (which I am ignoring because it isn't very clear). The molt starts when the old cuticle separates from the epidermal cells, and the cells begin to secrete a new cuticle. Once the new cuticle is complete enough, and a lot of the proteins and stuff from the old one are reabsorbed, the animal sheds the cuticle in a process called ecdysis. In most species, they then eat the molted cuticle to get the rest of the nummy goodness out of it. The molt is triggered when MIH stops being secreted, which causes a peak of 20E. It looks like there has to be both a rise and a fall in 20E levels for molting to happen normally, because 20E will inhibit ecdysis when injected during a molt.
What started people thinking about the existence of MIH was the fact that removal of the eyestalks, induces molting. Kids, don't do this at home, because it's abnormal, and they usually die. Anyway, this led to the discovery of the X organ, which is a neuosecretory thingy connected to the brain that resides in the eyestalks. It got its name because the discoverer marked it with an "X" on a figure.
Another way of inducing a precocious molt is to remove a few legs. This gets the molting system moving, and gets the guys new legs through regeneration. What the Skinner review said was that more legs off=faster molt.
Another interesting factoid is that serotonin inhibits 20E secretion, possibly by stimulating secretion of MIH. Stress also inhibits 20E secretion, maybe via the same pathway.
There's a lot of complexity, and many things are stage and species specific, but this is the general outline as I understand it. For example, adult lobsters molt annually, so there is a seasonal component to regulation, while shrimp that molt every 2 weeks will presumably have different triggers.
I left the papers at home, so let me know if you want the references.
Kreblak, I still like your theory that the iodine idea came about because someone equated shrimp with chickens.
If anyone wants to discuss the above, I am afraid that I, Dr Dave, will become combative and ban you from my forum. Oh, yeah, it's not my forum. Careful, I may still become difficult.
 
I just wanted to say that that was very interesting. Good searching. Can you list the database where you found it?
 
At my home base, I used Pubmed and Web of Science. At MBL I went through AFSA (aquatic science and fisheries abstracts), BIOSIS, and Zoological record. The searches were crustacea AND iodine, crustacea AND molt, crustacea and ecdysone, iodine AND molt, and probably a few other permutations. Plus generous use of wildcards. Most searches involving iodine came up with nil.
The papers I got the info from were:
Skinner, DM (1985) Molting and regeneration. In DM Bliss and LH Mantel (Eds) The Biology of Crustacea v9, 43-146. Academic press.
-Most complete, if old
Chang et al., (1993) Regulation of crustacean molting: a multi-hormonal system. Amer Zool 33:324-329
Huberman (1990) Hormonal control of molting in crustacea. Prog Comp Endocrinol [vol?] 205-210
-There's a more recent (2002?) Huberman review that came up in Web of Science, but I haven't put my hands on it yet.
They are all reviews, sorry. A lot of the original literature was not even available at MBL. Not that any of it looked like it dealt with the iodine issue based on titles and abstracts. Apologies for typos. I'm beat.
 
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