Question

Haemocoel is found in
(a) Hydra and Aurelia
(b) Taenia and Ascaris
(c ) Balanoglossus and Herdmania
(d) Cockroach and Pila

Answer 1

Hint: Both the animals in which haemocoel is present possess a hard exoskeleton that is made up of complex modified polysaccharide chitin or calcium carbonate. One is a common insect while another one has a shell around it.

Complete answer:
Haemocoel is the main body cavity in insects and molluscs. Cockroach belongs to phylum Arthropoda while Pila is a freshwater Mollusc. They possess the open circulatory system, wherein the blood flows freely in the body cavity i.e. haemocoel. It bathes the cells directly.
-In cockroach, the haemocoel is present in the thoracic and abdominal regions and it is divided by the diaphragm, into three large sacs.
-In Pila, the haemocoel is used to store the blood as there are no capillaries present to transport blood or any fluid collected from tissues to the heart.
-In Hydra and Aurelia, the circulatory system is absent so their oxygen and nutrient demands are met directly by the process of diffusion from the water surrounding them.
-In Tenia solium and Ascaris the circulatory system is absent so the oxygen and nutrients demand is met by the process of diffusion.
-In Balanoglossus the circulatory system is partially open with dorsal and ventral vessels, a heart and a series of sinuses (cavities). Whereas in Herdmania the circulatory system is well developed and closed.

So, the correct answer is ‘Cockroach and Pila’.

Note:
-The blood-filled spaces in arthropods are of three types– dorsal or pericardial sinus, middle or perivisceral sinus and ventral or perineural sinus.
-Dorsal sinus encloses the heart, the middle sinus encloses digestive, respiratory, excretory, and reproductive systems, ventral sinus encloses the sterna and nerve cord.