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THE BIOLOGY OF MARINE ANIMALS 



TABLE 4.1 

 Distribution of Gill Structure in Relation to Function 



Molluscs. Purely respiratory gills display much diversity in molluscs. 

 In primitive amphineurans, such as Chiton, a row of plume-like gills lies 

 in each pallial groove. There is a single ctenidium or a pair of ctenidia in 

 the mantle-cavity of aquatic gastropods, including typical prosobranchs 

 such as whelks and periwinkles, and tectibranchs such as Aplysia. The 

 molluscan ctenidium is a respiratory structure consisting of an axis bearing 

 lamellae. The ctenidium has been lost in pteropods and nudibranchs; sea- 

 slugs such as Doris possess a tuft of retractile cerata or gills on the posterior 

 dorsal surface. 



Cephalopods have one or two pairs of feathery gills located in the 

 posterior region of the mantle cavity, and a special mechanism exists for 

 ventilating these structures. During inspiration the mantle cavity is en- 

 larged, the funnel is closed by a valve, and water is drawn in anteriorly at 





