Which of the following has a central gastro-vascular cavity with a single opening, mouth on hypostome?
Hydra (a cnidarian) has a central gastro-vascular cavity with a single opening, mouth on hypostome.
Scypha has a spongocoel which opens out by an osculum.
Taenia lacks a body cavity and a mouth.
Locusta is an insect. Its body cavity is haemocoel. Its alimentary canal has two openings – mouth and anus.