Attendant phobias may merge to create this condition of aviophobia. For example, acrophobia (a fear of heights) may merge with claustrophobia (a fear of being in a small enclosed area) to form an extreme fear of being trapped in the confines of the seating area of a plane and not being able to leave the space because the plane is in flight.
Most aquarium fish can regrow their tails to some degree. However, this ability is not magic. You need to identify the cause of the fin damage and correct it to prevent recurrence.You will also need to provide optimal conditions to encourage regrowth.sually, a fish will regrow fins without incident. But sometimes, fin rot and other disease may impair its ability to do so. If you see signs of infection and salt doesn't help, consider purchasing antibiotics from the pet shop.
Bony fishes can swim forward and backward.   Gills:   Both cartilaginous and bony fish have gill slits but the bony fish also have gill covers (an operculum).   Reproduction:   In the Chondrichthyes the males have claspers which assist in copulation. Fertilisation is internal-almost unique among fish. Scales:   Cartilaginous fish have large scales called placoid scales. These have a bone like base embedded in the skin and a backward projecting enamel covered dentine spine. The whole thing has a central pulp cavity (rather like the structure of teeth). The epidermis and dermis form placoid scales.