Charactristics of Echinoderms 10B (Water-Vascular System (A system of…
Charactristics of Echinoderms 10B
A system of fluid -filled, closed tubes that work together to enable echinoderms for movement and getting food,
The strainer like opening to the system is called the madreporite.
1) Water is drawn into the madreporite
2) Then moves through the stone canal to the ring canal
3) Then water moves to the radial canals and eventually to the tube feet.
Tube feet are small, muscular fluid-filled tubes that end in suction-cuplike structures which attach to the surface.
Tube feet are used for movement, food collection, and respiration.
The opposite end of a tube foot is a muscular sac called the ampulla.
When muscles contract in the ampulla water is forced into the tube foot and it extends.
This hydraulic suction enables them to move and to apply a force strong enough to open shells
Respiration, Circulation, and Excretion
Circulation takes place in the coelom and in the water-vascular system.
Excretion occurs by diffusion through body membranes.
Cilia move water and body fluids throughout these systems.
Respiration, they can take in oxygen by three ways:
Oxygen diffuses from the water through the membranes of the tube feet. oxygen diffuse through a thin outer membranes.
Pouches called skin gills
Branched tubes called respiratory trees through which oxygen diffuses
4-Response to stimuli and movement (Modi)
A- Responce to stimuli
A nerve ring surrounds the mouth with branching nerve cords connecting to other body areas
Sensory neurons respond to chemicals, touch, water currents and light
many echinoderms sense gravity
The moveable bony plates in the endoskeleton enables them to move easily
Feather stars move by cirri (long thin appendages on the ventral sides) or by swimming up and down
Brittle stars use their tube feet and arms to move in a snakelike locomotion
sea stars use their arms and tube feet to crawl
sea urchins move by using tube feet and burrowing with moveable spines
sea cucumbers use tube feet and body wall muscle
Echinoderms use tube feet as a main feeding structure, but they have different feeding structures too.
Sea Lilies and Feather Stars extend their arms and trap food.
Sea Stars prey on a variety of mollusks, coral and other invertebrates.
Many species of sea stars can push their stomachs out of their mouths and onto prey.
They then spread digestive enzymes over the food and use cilia to bring the digestive food into their mouths.
Brittle Stars can be predators or scavengers and they can trap organic materials in mucus on their arms.
Sea Urchins use teethlike plates to scrape algae off surfaces.
Sea Cucumbers extend their branched mucus covered tentacles to trap floating food.