What are the external features of Planaria?
The planarian has a soft, flat, wedge-shaped body that may be black, brown, blue, gray, or white. The blunt, triangular head has two ocelli (eyespots), pigmented areas that are sensitive to light.
Is Planaria external fertilization?
Although planarians are hermaphroditic, they normally do not self-fertilize. This means that although an individual carries both ovaries and testes, it does not use its own sperm to fertilize its eggs. When mating, planarians exchange sperm and each individual is fertilized by the other.
What is special about Planaria?
Because of their remarkable ability to regenerate lost parts, planarians are often used experimentally to study the process of regeneration. In the flatworm Planaria, the brain consists of two cerebral ganglia (clusters of nerve cells) from which nerve cords extend the length of the body.
What are the parts of a planarian?
(B) A planarian cut into three pieces (head, body, tail) will regenerate into three separate individuals.
How do you identify planaria?
Planaria are most identified by the positioning or amount of their eye-spots called ocelli, but also by their head morphology/shape or coloration.
How do planaria go through reproduction?
Abstract. Asexual freshwater planarians reproduce by tearing themselves into two pieces by a process called binary fission. The resulting head and tail pieces regenerate within about a week, forming two new worms. Understanding this process of ripping oneself into two parts poses a challenging biomechanical problem.
How do planaria sense things in their surroundings?
Many planarians have structures called eyespots in their anterior (head) region, which detect light. Planarians can sense and respond to chemical stimuli in their environment by using chemoreceptors mainly localized on the sides of their bodies (auricles).
How long does a planarian live?
The planarians live as long as they are not killed. If they are well cared for, they will live indefinitely.
How are planaria bodies supported?
Their bodies are surrounded by a dense and compact net of subepidermal muscle fibers arranged in different orientations. Locomotion in these planarians basically occurs through ciliary gliding. Muscles may support this locomotion and are mainly used to orientate the direction of the movement.
What is the structure that has the mouth of the planaria?
The digestive system consists of a mouth, pharynx, and a structure called a gastrovascular cavity. The mouth is located in the center of the underside of the body. Digestive enzymes secrete from mouth to begin external digestion.