235 



Cake, Edwin W. , Jr. 1977. 



Larval cestode parasites of edible mollusks of the northeastern Gulf of Mexico. 

 Gulf Research Repts . 6(1): 1-8. 



Larval cestodes of the genus Tyloeephalum have been found in Venus (Mereenaria) 

 mereenaria texana and M. campechiensis from the eastern Gulf of Mexico. These 

 are not known to be infective to humans who eat clams raw, and experimental 

 evidence obtained in this study suggests that these larvae are destroyed by 

 human digestive acids and enzymes. Heavy infestations of larval cestodes may 

 cause physiological stress in the host, which reduces the quality of meats. 

 101 larval cestodes were found in 6 M. eampechiensis from 5 stations, in 69 

 M. campeehiensis from 9 stations; and 477 larval cestodes in 3 M. m. texana, 

 of 4 from 2 stations. - J.L.M. 



236 



Calabrese, Anthony. 1972. 



How some pollutants affect embryos and larvae of American oyster and hard- 

 shell clam. Mar. Fish. Rev. 34(11-12): 66-77. 



Clam embryos and larvae were exposed to a range in pH from 6.0-9.5. Embryos 

 developed normally in the pH range 7.0-8.75. At pH 9.0 development was 

 reduced, and there was no development at pH 9.25-9.5. The pH range for 

 normal larval survival was 6.25-8.75. The pH range for normal larval 

 growth was 6.75-8.5. Larval growth was most rapid at pH 7.5-8.0. Heavy 

 siltation or any pollution that changes the pH of waters could cause 

 failure of clam recruitment. - D.L. 



237 



Calabrese, Anthony, and Harry C. Davis. 1966. 



The pH tolerance of embryos and larvae of Mereenaria mereenaria and 

 Crassostrea virginiea. Biol. Bull. 131(3): 427-436. 



Embryos and larvae of hard clams were reared in seawater with pH adjusted 

 from 6.00 to 9.50. The pH range for normal embryonic development was 7.00- 

 8.75. The lower pH limit for survival of clam larvae was 6.25. Survival 

 in the pH range 6.25-8.75 was 68%. The pH range for normal growth for clam 

 larvae was 6.75-8.50. Growth dropped rapidly at pH below 6.75. The optimum 

 pH for larval growth was 7.50-8.00. Any siltation or pollution that would 

 cause pH to fall below 7.00 or rise above 9.00 could cause failure of hard 

 clam recruitment. - D.L. 



238 



Calabrese, A., and H. C. Davis. 1970. 



Tolerances and requirements of embryos and larvae of bivalve molluscs. 

 Helgolander wiss. Meeresunters . 20: 553-564. 



This review paper contains no original data. The papers cited are abstracted 

 elsewhere in this volume, thus a brief abstract is sufficient. The authors 

 prefer to induce spawning rather than to strip. This eliminates broken 

 tissue and immature eggs. Clams are placed in dishes filled with seawater 

 and temp is raised in a water bath. If 28°C does not induce spawning, 

 stripped sperm are added. Fertilized eggs are poured through a screen to 

 remove faeces and other debris. Food for larvae must usually be less than 

 10 u in diam. It must be digestible, and contain the necessary carbohydrates, 

 fats, proteins, and vitamins. Naked flagellates are better than those with 

 cell walls. Some algae which produce toxic metabolites must be avoided. If 

 bacteria grow in algal cultures, even good food organisms may become toxic. 

 Some bacteria produce toxic metabolites, others do not. Growth of hard clam 

 larvae was much better when fed mixed naked algae than with Chlorella. Hard 

 clam is less tolerant of low salinity than other bivalves. Below 22°/°° most 

 embryos fail to develop to straight-hinge stage. Larvae, however, can 

 survive and grow reasonably well at 17.5°/°° or even 15°/°°. Growth of clam 

 larvae is much less affected by temp than are oyster larvae. Larvae tolerate 

 a considerably wider range of pH than embryos. For successful recruitment of 



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