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The habits and feeding organs of Dentalium entalis

  • J. E. Morton
Extract

The Scaphopoda or tusk-shells are the smallest and most uniform class of molluscs. They burrow in sand of medium to coarse shelly grade, and specialize on a diet of hard-shelled microbenthos, particularly Foraminifera. Dentalium entalis L. is the commonest West European species, and may become locally dominant. Le Danois (1948) has described a ‘Dentalietum’ in deeper water sandy ground at about 100 fathoms in the southern Celtic Sea. Stephen (1933) discusses the distribution of D. entalis in the northern North Sea, where it is largely restricted to the ‘Offshore zone’, the southern limit being marked by the 60 m line. Low salinity is probably responsible for its absence from the southern North Sea; and in general it seems limited more by hydrographic conditions than by the relative abundance of foraminiferan food. For example, in Stephen's Thyasira+ Foraminifera Zone, it is no more than sparsely present. Holme (1953) finds Dentalium entalis rare or absent near Plymouth, though it was relatively common at the Eddystone Grounds at the end of last century (Allen, 1899). It has today receded to the mouth of the Channel, in coarse deposits resulting from fairly strong scour, and Holme suspects it to be one of the list of species sensitive to recent hydrographic changes in the area.

For the living material used in this study I am greatly indebted to Mr N. A. Holme, who collected it in deeper water in the Celtic Sea on a 1953 cruise of the R.R.S. ‘Discovery II’. With it were collected Chlamys opercularis, Caryophyllia and in places Astropecten irregularis; there were also many of the tusk-shaped serpulid tube worm Ditrupa arietina which as I found can impose a neat deception on the uncritical hunter for scaphopods.

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References
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Allen, E. J., 1899. On the fauna and bottom deposits near the thirty fathom line from the Eddystone to Start Point. J. mar. biol. Ass. U.K.. Vol. 5, pp. 365542.

Bidder, Anna M., 1950. The digestive mechanism of the European squids. Quart. J. micr. Sci., Vol. 91, pp. 143.

Clark, W., 1849. On the animal of Dentalium tarentinum. Ann. Mag. nat. Hist., Ser. 2, Vol. 4, pp. 321–30.

Dales, R. P., 1955. Feeding and digestion in terebellid polychaetes. J. mar. biol. Ass. U.K., Vol. 34, pp. 5579.

Danois, E Le., 1948. Les Profondeurs de la Mer. Paris: Payot.

Dell, R. K., 1957. A revision of the recent scaphopod Mollusca of New Zealand. Proc. roy. Soc. N.Z., Vol. 84, pp. 561–76.

Fol, H., 1889. Sur l'anatomie microscopique du Dentale. Arch. Zool. exp. gen., T. 7, pp. 91148.

Holme, N. A., 1953. The biomass of the bottom fauna in the English Channel off Plymouth. J. mar. biol. Ass. U.K., Vol. 32, pp. 149.

Morton, J. E., 1956. The tidal rhythm and action of the digestive system in Lasaea rubra. J. mar. biol. Ass. U.K., Vol. 35, pp. 563–86.

Owen, G., 1955. Observations on the stomach and digestive diverticula of the Lamellibranchia. I. The Anisomyaria and Eulamellibranchia. Quart. J. micr. Set., Vol. 96, 517–37.

Smith, J. E., 1947. The activities of the tube feet of Asterias rubens. Quart. J. micr. Sci., Vol. 88, pp. 114.

Stephen, A. C, 1933. Studies on the Scottish Marine Fauna: The natural faunistic divisionsof the North Sea as shown bythe quantitative distribution of themolluscs. Trans, roy. Soc. Edinb., Vol. 57, pp. 601–16.

Yonge, C. M., 1937. The circulation of water in the mantle cavity of Dentalium. Proc. malacol. Soc. Lond., Vol. 22, pp. 333–8.

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Journal of the Marine Biological Association of the United Kingdom
  • ISSN: 0025-3154
  • EISSN: 1469-7769
  • URL: /core/journals/journal-of-the-marine-biological-association-of-the-united-kingdom
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