Cnidarians | Cnidaria
Cnidarians or Cnidaria are mostly found in marine environments. However, some species are found in freshwater bodies. They include sea anemones, corals, and jellyfish. They are identified by the cnidocyte cells for capturing prey. Their body is sandwiched between two epithelium cells and composed of a living jelly-like substance called mesoglea. Cnidarians mainly prey on planktons, parasites, and small animals like turtles and sea slugs. Adult cnidarians have no heads and would appear as free-swimming medusae or sessile polyps. They have tentacles around their edges and inner mouths and reproduce either sexually or asexually.
Cnidarians are aquatic animals with two body forms (the ectoderm and endoderm separated by a mesoglea). To capture prey or even defend themselves, cnidarians have unique and well-developed specialized cells in their mouths and tentacles for stinging attackers. These cells, called cnidocytes, have toxins that are released when their body is touched.
Sexual and asexual reproduction are the forms of reproduction seen among cnidarians. Besides, some are hermaphrodites — capable of producing both eggs and sperms at the same time. However, asexual reproduction is the most common in this species. Sexual reproduction may occur only in one phase of a cnidarian’s life cycle.
What cnidarians have are diffuse nets of nerves that coordinate messages around their bodies. Research shows that these nets of nerves are just as complex as that of human beings. In addition, some like jellyfish, have no heart or eyes. Most cnidarians also have a transparent body covered in a chitinous exoskeleton.