Arrange the following steps and anatomical structures in the correct sequence through which water and trapped nutrients travel during filter feeding in a bivalve mollusc, from initial entry to ingestion.
- 1Water carrying suspended organic matter enters the mantle cavity via the incurrent siphon.
- 2Cilia on the ctenidia (gills) drive water across gill filaments, trapping food particles in mucus.
- 3Mucus strands containing food are sorted by labial palps to separate digestible matter from rejected pseudofeces.
- 4Selected food particles enter the mouth to pass into the esophagus and stomach for digestion.
- 5Filtered water and metabolic waste products are expelled from the mantle cavity through the excurrent siphon.
Answer
The correct sequential order of filter feeding in bivalves is: Incurrent siphon entry → Ctenidia trapping food → Labial palp sorting → Mouth ingestion → Excurrent siphon expulsion.
In bivalve molluscs (such as mussels and clams), filter feeding follows a continuous path: water enters through the incurrent siphon, passes over the ctenidia (gills) where food particles become trapped in mucus, moves to the labial palps for mechanical sorting, enters the mouth for digestion, and filtered water exits via the excurrent siphon.
Step-by-Step Solution
Key Concept
Bivalve Filter Feeding Mechanism