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THE MORPHOLOGY OF STINGING CELLS IN THE MARINE INVERTEBRATE NUDIBRANCH, CRATENA PILATA
Citation:
Matarese, S. E., D B. Horowitz, AND G. KassSimon. THE MORPHOLOGY OF STINGING CELLS IN THE MARINE INVERTEBRATE NUDIBRANCH, CRATENA PILATA. Presented at National Society of Histotechnology Conference, Providence, RI, October 16-21, 1999.
Description:
The association between the marine invertebrate nudibranch, Cratena pilata, and its food source has intrigued researchers for many years. These nudibranchs, or shell-less snails, obtain stinging cells by feeding on the jellyfish-like coelenterate, Tubularia sp. It is believed that these stinging cells become the protection mechanism for the otherwise defenseless nudibranch. By microscopically studying the morphology and organization of these cells in their original coelenterate host and comparing it to the way they are incorporated into their new nudibranch host, we hoped to learn and understand the mechanisms required in this process. Embedded within the epidermis of the tentacles of the Tubularia are specialized stinging organelles called nematocysts. In coelenterates, nematocysts are used in the stinging and capture of food, defense from predators, and for motility. Each nematocyst has sensory hairs, or cnidocils, that when touched trigger the discharge of an encapsulated tubule containing the stinging components. Once the nematocysts have been ingested, they are taken up into specialized cells called cnidophages. These are located in the cerata, finger-like projections on the dorsal side of the nudibranchs. Cerata occur in clusters distributed symmetrically on the sides of the nudibranch's body and are principally digestive and respiratory in function, consisting mostly of liver tissue. Nematocysts from food sources pass into the digestive diverticulum within the ceras. They then pass through a narrow ciliated channel into the cnidosac where they are engulfed by cnidophage cells. The cnidosac is a specialized structure at the tip of the ceras that contains cnidophage cells. Histopathological techniques helped explore the morphology, relationship, and function of the nematocysts in the nudibranch and the coelenterate. Microscopic examination revealed that the orientation of the nematocysts within the cnidosac of the nudibranch is similar to their orientation in the tentacle of the coelenterate. Connective tissue, neurological, and other histochemical stains characterized the chemical mechanisms of the nematocysts in their natural state within the Tubularia and their orientation and use for protection by their new host animal.