Cnidaria (Jellyfish, Anemones and Corals)
Description: Cnidaria is a relatively large and diverse group of invertebrates which include the sea anemones, corals and jellyfish. Cnidaria has over 11,000 species and they can be either mobile (free-swimming medusa) or immobile (sessile polyps), depending on the species or their life stage. Both forms have a mouth that is surrounded by tentacles that help with the capture of prey. They are an entirely aquatic group, with 99% of species being marine. The inner and outer walls of their bodies are separated by a gelatinous material called the mesoglea. They exhibit radial symmetry, which allows them to react to their environment from all sides.
Feeding: Cnidaria have cnidocytes, which are stinging cells, around their mouths and on their tentacles. These cells contain nematocysts, stingers, which can be used to ensnare, immobilize and paralyze the prey with toxins. The food is then pulled into the mouth and slowly digested in their bag-like central digestive cavity.
Reproduction: Cnidarians can reproduce both sexually and asexually, and this can change depending on their life stage. Asexual reproduction is typical of the polyp stage and is accomplished through the formation of new polyps or strobilation, which creates tiny medusae. Medusa usually reproduces sexually with external fertilization.
Classes: Cnidaria is divided into 4 classes
1. Anthozoa – the sea pens, sea anemones and corals;
2. Cubozoa – the box jellyfish;
3. Hydrozoa – they have tiny size with a plant-like appearance;
2. Scyphozoa – the true jellyfish.
Ieranto bay consists of Hydrozoa, Scyphozoa and Anthozoa.
