Discuss the habitat and peculiar characters of Obelia.

Explanation

The common name of obelia is sea fur.
Characters : Obelia is a luminescent branched filamentous structure. It consist of two types of branches, horizontal hydrorhiza and vertical hydrocauli. The body is attached to the substratum by hydrorhiza. Hydrocauli bears two types of zooids, i.e., polyps and blastostyles. Polyps are nutritive zooids which completely lie in hydrotheca. It has a manubrium or hypostome with a central mouth and 20-30 solid tentacles towards the free end. Each blastostyle is covered with gonotheca. The axis of the blastostyle buds of 3rd type of zooids, called medusae. Medusae is free swimming, reproductive zooids of Obelia. These are umbrella shaped in outline. Mouth lies at the tip called manubrium. Internally, it leads into radial canals. These radial canals merge into circular canal. Medusa is commonly dioecious. The fertilized egg or zygote develops into a free swimming larva called planula.