Vandenspiegel, D., M. Jangoux and P. Flammang. 2000. Maintaining the line of defense: Regeneration of Cuverian tubules in the sea cucumber Holothuria forskali (Echinodermata, Holothuroidea). Biological Bulletin 198: 34-49.
It has long been understood that Holothuria, upon disturbance, will expel sticky and immobilizing tubules from the aboral end (opposite of mouth). Further research indicated that these Cuverian tubules can regenerate once expelled, however the mechanism was unclear. How do Cuverian tubules regenerate?
Prior to this paper, virtually nothing was known of these unique defensive organs, aside from the structure, organization and function. Blind ended Cuverian tubules can be found in the hundreds in the coelomic cavity, while attached at one end to the left respiratory tree. The animal is able to contract and tear the wall of the cloaca, thereby allowing the tubules to lengthen and paralyze animals that subsequently come in contact. The tubules that are forced out obliterate their attachment and fall off; a new tubule is then regenerated.
The authors attempt to analyze the problem at three levels: macroscopic regeneration stages, creation of tissue layers, and cellular origins of the tubules. Specimens were obtained and subject to one of two procedures. Either gently stimulated or strongly stimulated, the latter causing expulsion of a large number of tubules. The animals were then reared, and dissected at varying times after induced expulsion.
Results indicate that regeneration takes place in three phases, taking five weeks to complete. A complicated progression of differentiation of cells and growth constitutes a new tubule. A final consideration suggests that these tubules are a very effective defensive mechanism, they are numerous and not costly to regenerate.
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