Hydra is a small tube-shaped animal. When expanded they are about 1-3 cm long and 1 mm wide. When removed from the water, they turn into a soft and shapeless lump. Hydra’s body consists of three parts. Hypostome, body stem and foot.
1. Hypostome: The word Hypostome is formed from hypo meaning below and stoma meaning mouth. The upper part of the body has a mouth opening. The small and twisted contractile organ below the stoma is called the hypostome. Stomata receive food, water and oxygen. It expels undigested or waste material.
2. Body: The entire body except the hypostome and the base is called the body. Different parts of the body-
(i) Sterile: At the base of the hypostome there are 6-10 slender, long, hollow and contractile-expanding sturgeon. Each karshika is twice or thrice as long as the body. The outer wall of Karshika consists of batteries of small nematocysts like tumors. Karshikas are arranged in a circle. It participates in food intake, movement and self-defense.
(ii) Mukul: Favorable environment or environment with sufficient food during summer. Hydra gains physical growth by consuming food. As a result, one or more buds are formed in the middle region of the body. Each bud matures and gives birth to a new hydra. This is one of hydra’s asexual reproduction methods. Dr. Siddiq Publications
(iii) Genitalia: During hibernation and winter, temporary genitalia are formed on the body of the metamorphosed hydra. The upper part of the body contains the spermatozoa and the lower part the ovary. The testicles produce sperm and the ovaries produce eggs. Participates in sperm and egg production.
(iv) Pedicel: The part between the stem and the foot is the petiole. It is narrow, narrow and contractile. It connects the body and the foot.
3. Padachakti: The round and pressed part in the lower part of the body is the sole of the foot. A sticky substance secreted from the soles of the feet keeps the hydra attached to objects. Bubbles help float in water. It helps the hydra to move by forming a membrane. Hydra displays gliding movements with the help of discs. Dr. Siddiq Publications