Physiology of Finfish and Shellfish (2+1)

2.1.33. Physiology of respiration

• Mantle contracts – water is forced through gills.
• Entrance of mantle cavity closes by use of locking apparatus.
• When mantle contracts; water is forced through gills.
• Water expulsion through funnels helps aid jet prepulsion.
• Circulation of water is reverse from that of gastropods
• Since water leaves the mantle cavity by means of funnel, the exhalent current is ventral to the inhalant current.
• Water flow is controlled by contractions of the radial and circular mantle cavity muscles.

Schematic representation

Relation between gill size and life style

• To achieve fast speeds – gills need to be small – water passed over them quickly.
• Larger gills – slow moving organisms – complex system ensures constant water movement over gills.