Learn about the comparison between respiratory organs of Unio and Pila.
Comparison # Unio:
1. Modes of respiration in Unio is aquatic.
2. Respiratory organs in Unio are primarily the gills. Highly vascular mantle also acts as an accessory respiratory structure.
3. Two highly developed symmetrical gills are situated one on each side of the body of Unio.
4. Structure of gill of Unio is complicated structure. Each gill has two plates—external and internal gill laminae. Each gill lamina is also a double structure and is formed of outer and inner gill lamellae.
5. There are two gill lamellae in each gill. They are united all along excepting the dorsal side. The space between them is divided into a number of compartments by vertical interlamellar junctions. These compartments are called water tubes. Between the gill filaments and bounded by interfilamentar junctions there are minute apertures (ostia) leading into the water tubes.
6. The gill filaments are extremely elongated structures. Each filament is covered by ciliated epithelium. It is supported by chitinous rods and the cavity is filled with blood.
7. During respiration water from the water tubes enters into the suprabranchial chamber and finally from this chamber water goes out through exhalant siphon.
8. Pulmonary sac is absent, because Unio lives exclusively in aquatic medium.
9. Nuchal lobes are absent in Unio.
Comparison # Pila:
1. Modes of respiration in Pila is both aquatic and terrestrial.
2. Aquatic respiratory organs are mainly the gill, and mantle acts as an accessory organ. Terrestrial respiration is done by pulmonary sac or lung.
3. Single gill is situated on the right portion of the mantle cavity of Pila.
4. Structure of gill if simple in Pila. Each gill is composed of numerous triangular gill lamellae. These lamellae are arranged in single row parallel to one another along the gill axis.
5. There are numerous gill lamellae in Pila. The basal end of each gill lamella is attached to the pallial epithelium and the other end hangs freely to the mantle cavity.
6. The gill filaments in Pila are lined by ciliated epithelium towards the free end and the basal portion is com-posed of non-ciliated epithelial cells and few glandular cells.
7. There is no such structure in Pila. After gaseous exchange the water goes out of the mantle cavity through the right siphon.
8. Pila utilises atmospheric oxygen by a pulmonary sac. It is a closed sac excepting an opening on the roof of the mantle. The dorsal wall of this sac is highly vascular and helps in gaseous exchange.
9. The nuchal lobes form siphons and help in the process of respiration in Pila.