Acid mucopolysaccharides underlie the outer epithelium of the 1st fold. The 

 4th fold contains a relatively large amount of mucus, but at least some mucus 

 is found in all folds and in the secretory ridge. Mantle epithelium generally 

 lacks glycogen, except on the inner surface of the 1st fold. Connective 

 tissue of the mantle, the area around the groove between the 1st and 2nd folds, 

 and the area at the base of the 2nd fold were relatively high in glycogen. 

 Nearly all epithelial cells, and underlying the epithelium enclosed by the 

 pallial line, had rather high concentrations of lipids. It is suggested that 

 lack of glycogen and abundance of lipids in the mantle may be related to 

 gametogenesis. When glycogen stored in mantle is transferred to gonads, 

 lipids may remain as a source of energy. - from Dissertation Abstracts 

 Internatl. 23(7), 1963: 2634-2635, pagination of thesis is given as 225 p. 

 - J.L.M. 



842 



Hillman, R. E. 1963. 



The quahog , a clam that rids itself of sand by "dribbling". Univ. Del., 

 Estuarine Bull. 7(1): 13-15. 



Mercenaria mercenaria has a self-cleansing mechanism by which it frees itself 

 of debris, and it thus does not have to be washed before eating. The mantle 

 consists of 2 broad membranous sheets of living tissue united in the hinge 

 region. Each half is in contact with the valve it secretes. The mantle 

 margin is thick and deeply grooved into 3 separate folds, which are just 

 inside the lips of the shell. These folds form a living curtain between the 

 clam and its environment when valves are open. The outermost fold is 

 secretory and lies next to the shell, the middle fold is sensory, and the 

 inner is a muscular flap which controls water flow into mantle cavity. 

 Quahog mantle has a 4th fold and an adjacent ridge of secretory tissue around 

 the mantle edge; both form mucus. The base of the 4th fold is supplied with 

 muscle fibers. If sand is pumped onto mantle surface by incurrent siphon, 

 ciliary activity carries it to the mantle edge. There it is coated with 

 mucus and is trapped in the groove between the secretory ridge and the 4th 

 fold. Mucus-wrapped debris then is exuded between mantle margins to the 

 outside. - J.L.M. 



843 



Hillman, Robert E. 1964. 



The functional morphology of the fourth fold of the mantle of the northern 

 quahog, Mercenaria mercenaria (L.). J. Elisha Mitchell Sci. Soc. 80(1): 8-12. 



In contrast with other well-known bivalves the mantle margin of Mercenaria 

 mercenaria terminates in 4 rather than 3 folds. Cells of the 4th, innermost 

 fold, and an adjacent ridge of tissues, secrete copious amounts of mucus and 

 mucoid substances which, with activity of fold and ridge, apparently aid in 

 removing detritus and pseudofeces from mantle cavity. Histological details 

 are illustrated. - J.L.M. 



844 



Hillman, Robert E. 1968. 



Histochemical studies of mucus in the mantle of two species of venerid clams. 

 In Proc. Symp. Mollusca, Pt. II. Mar. Biol. Assn. India, Mandapam Camp: 

 564-567. 



Mercenaria mercenaria and M. campechiensis produce copious amounts of several 

 types of mucus in the mantle margin. Physiological roles of these substances 

 are not yet fully defined, but they appear to serve several important 

 functions, such as calcification, removal of debris, and perhaps others. 

 Much more work is needed to clarify these processes. - J.L.M. 



235 



