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The fertilized eggs secrete a tough outer coating, and, as the adult dies (due to starvation or cold), these resting eggs fall to the bottom of the lake or pond to await better conditions, whereupon they hatch into nymph Hydra. Some Hydra species, like Hydra circumcincta and Hydra viridissima, are hermaphrodites [12] and may produce both testes ...
Like humans and other animals, fish suffer from diseases and parasites.Fish defences against disease are specific and non-specific. Non-specific defences include skin and scales, as well as the mucus layer secreted by the epidermis that traps microorganisms and inhibits their growth.
The following is a list of aquarium diseases. Aquarium fish are often susceptible to numerous diseases, due to the artificially limited and concentrated environment. New fish can sometimes introduce diseases to aquaria, and these can be difficult to diagnose and treat. Most fish diseases are also aggravated when the fish is stressed.
Hydra oligactis. This species can reproduce in three ways: sexual reproduction, budding, and indirectly through regeneration. [11] When hydra reproduce sexually, simple testes, ovaries, or both will develop on the bodies of an individual. Sperm released into the environment by the testes enters the egg within the ovary.
Due to the artificially limited volume of water and high concentration of fish in most aquarium tanks, communicable diseases often affect most or all fish in a tank. An improper nitrogen cycle , inappropriate aquarium plants and potentially harmful freshwater invertebrates can directly harm or add to the stresses on ornamental fish in a tank.
HLLE begins as small pits of receding epithelium (skin) around the fish's head and/or lateral line, and sometimes onto the unpaired fins. Rarely fatal, it does cause disfigurement, making the fish less suitable for public aquarium display. At least 20 families of fish have been identified as having developed HLLE in captivity.
Hydra viridissima is a species of cnidarian which is commonly found in still or slow-moving freshwater [2] in the Northern temperate zone. Hydra viridissima is commonly called green hydra due to its coloration, which is due to the symbiotic green algae Chlorella vulgaris which live within its body. [ 3 ]
Most fire coral species have brittle skeletons that can easily be broken, for example, during storms, or by divers when diving for leisure, or when collecting fish for the aquarium trade. For instance, the yellowtail damselfish ( Chrysiptera parasema ) tends to dwell close to the branching fire coral colonies, and retreats into its branches ...