The comparative characteristics of freshwater hydra and white planaria give a clear idea of the features of the organization and development of two types of multicellular animals - intestinal and flatworms. In our article, we will consider this issue from the perspective of complicating the features of their structure.
Habitat
On this issue, the comparative characteristics of freshwater hydra and white planaria are similar. The first animal got its name by habitat. Although its many related species live in the seas. Planaria also prefers small freshwater bodies where it hides under snags and pebbles.
Lifestyle
The type of freshwater hydra is a single polyp. It is attached to underwater objects by the base of its stalk - the sole, which acts as a suction cup. At the opposite end of the hydra's body are tentacles. With their help, the animal captures, holds the prey and directs it into the mouth opening. Due to the presence of specialized skin and muscle cells, the hydra can contract and bend. Unlike a freshwater polyp, planaria leads a mobile lifestyle.
Many representatives of intestinal and flatworms lead a completely different lifestyle. For example, the hepatic trematode and broad tape, which are parasitic worms, attach to the ducts of the internal organs of the hosts.
Type of food
A comparative characteristic of freshwater hydra and white planaria is impossible without considering the type of food. In these matters, these organisms have much in common. Planaria and hydra are heterotrophic organisms. Moreover, both of these species are predators. Hydra hunts with stinging cells that paralyze prey.
Planaria also attacks small aquatic animals. Epithelial cells that swell in water help to capture and fix the victim. The digestive system of the planaria is the mouth and intestines. The latter has anterior and middle sections that end blindly.
Structural Features of the White Planaria and Hydra
Hydra has a ray symmetry. Her body is formed by two layers - ecto- and endoderm. They include various types of specialized cells: digestive, sex, epithelial-muscular, stinging, glandular, digestive, nerve. They are scattered throughout the body of the polyp and do not form tissues.
The white planaria, which is a representative of the type of flatworms, has a characteristic body shape. It is flattened in the dorso-abdominal direction and resembles a small leaf. This is an animal with bilateral symmetry. Planaria have real tissues, organs, and their systems. It is musculoskeletal, digestive, excretory, nervous, sexual. A common feature of these animals is a high level of regeneration. So, hydra can recover from a mushy state, and planaria is capable of vegetative propagation.
The comparative characteristics of freshwater hydra and white planaria indicate a significant increase in the level of organization of flatworms. Intestinal, along with sponges, are the first multicellular representatives of the animal world. However, they do not have real tissues. This structure appears only in flatworms. Therefore, their structure and activity is characterized by a higher level. Primitive features of their structure are the absence of organs of the respiratory and circulatory system. Therefore, gas exchange in flatworms occurs through the surface of the body.