Hemichordata and Invertebrate Chordates. Phylum Hemichordata. Characteristics of Hemichordata:-. All live marine environments. Bilaterally symmetrical. Body divided into three sections, a proboscis, a collar and a trunk. Body cavity a true coelom divided into three cavities.
Characteristics of Hemichordata:-
All live marine environments.
Body divided into three sections, a proboscis, a collar and a trunk.
coelom divided into
Complete digestive tract, feeds on fine particles in the water.
Dorsal, sometimes tubular, nerve cord.
Ciliated epidermis and glands
cover acorn worms
Burrow in sandy and muddy substrates
Common name ‘acorn worms’
Lateral Pharyngeal slits,few to several hundred
Cilia and mucus assist acorn worms in feeding
Ciliary tracts converge near the mouth and form a mucoid string that enters the mouth
Deep marine water
Some live in shallow waters
Size 0.1 - 5mm
Cilia on tentacles trap and transport
Food to mouth
Respiration and excretory exchange by diffusion
Asexual budding is common and responsible for colony formation
Also some posses one or two gonads
Most species are dioecious
Planula-like larva (cnidarian)
Settles to a substrate, forms cocoon and metamorphoses into an adult
Characteristic of the chordates
Deuterostome embryo development Notochord, phayngeal slits or pouches, dorsal tubular nerve cord, and postanal tail
Two major groups: nonvertebrate chordates and vertebrates