Question

1) Describe the route that water follows as it passes through a clam starting from the incurrent siphon and finishing with the excurrent siphon

2) Members of such a large and diverse phylum as Mollusca impact humans in many ways. Discuss this statement. 500 words max.

Answer 1

1) Water passes through these structures in the following order: incurrent (inhalant) siphon; inhalant space, through the interfilament spaces or ostia in the ctenidia, into the exhalant space inside the ctenidia, to the suprabrachial chamber and out the excurrent (exhalant) siphon.

Siphons are filters through which water is sucked through. This permits only the food particles to enter the clam. The flow of water out of the bottom of a siphon, which depends on the difference in height between the inflow and outflow. It cannot be dependent on atmospheric pressure.

2) Mollusca is a large phylum of invertebrate animals and members of this phylum are known as molluscs. Molluscs are bivalves such as clams and mussels. It has an important food source of anatomically modern humans. Most molluscs with shells can produce pearls, but only the pearls of bivalves and some gastropods, whose shells are lined with nacre are valuable. Other luxury and high-status products are made from molluscs. Humans can use mollusks as food and used as pests because of damage, snails and slugs damage gardens and vegetation, and snails can act as intermediate hosts for serious parasites of humans and animals.