The food value of sea mussels / by Irving A. Field.

  • Field, Irving Angell, 1870-1921.
Date:
1911
Catalogue details

Licence: In copyright

Credit: The food value of sea mussels / by Irving A. Field. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

    19/74 (page 93)
    the farmer who ignores the first principles of agriculture. Up to the present time, however, very little study has been made of the food of marine animals or of the relative fertility of the waters in various parts of the sea. Such investigations as those of Peck (1894 and 1896) on the sources of marine food, and of Moore (1907) on the food of the oyster are of very great economic value. My observations on the food of the mussel were necessarily limited. They were con- fined to the vicinity of Woods Hole and to the months of July and August. Lack of time did not permit a determination of the food value of the water over the mussel beds. During the summers of 1908 and 1909, however, a microscopic examination was made of the material found in the digestive tracts of 50 mussels. Two methods were employed. The first was to extract the stomach contents by means of a pipette, which was thrust down the animal’s gullet. The substance drawn out from the stomach was mixed with a few drops of water and a thin layer spread across the middle of a microscopic slide. The slide was then passed several times through the flame of an alcohol lamp, until the organisms were thoroughly fixed by the heat and the water almost evaporated to dryness. A drop of glycerin or of hot glycerin jelly was next applied and a cover glass pressed down upon it. Permanent mounts were later made from these preparations by cleaning the slides outside the boundary of the cover glass and ringing the mounts first with King’s cement and, twenty-four hours later, ringing them again with asphaltum. This method proved best for pre- serving the animal forms, Protozoa, found in the stomach. The second method was to place the mussels, immediately after removal from their natural beds, in small dishes of filtered sea water. After two or three hours’ time the bottoms of the dishes were covered with intestinal discharges, which were removed by means of a pipette and transferred to a vial containing 95 per cent alcohol. After the sediment had completely settled the alcohol was drawn off and fresh alcohol added. The process was repeated, using absolute alcohol instead of the weaker grade. This was followed by a few minutes’ treatment with xylol, and after removing most of the xylol three or four drops of a rather thin solution of Canada balsam were added. This mixture was allowed to stand for a few hours, until the xylol, sediment, and balsam were thoroughly mixed. Then, by means of a pipette, a large drop was transferred to a microscopic slide and on it was placed a cover glass. This method was found best for the preservation of the plant organisms which are known as diatoms. The diatoms, thus prepared, have had the pigments and coagulated protoplasm more or less com- pletely removed, leaving a clear view of the striations and other markings on the skeleton. The food of the mussel was found to consist of microscopic plants and animals which are carried by chance to the mollusk by water currents and are swept into the mouth by means of cilia on the gills and palps. The wall of the gullet is also lined with cilia, which direct the movement of the food material into the stomach. Not only food, but dirt and other indigestible substances are swept in. From the alimentary tracts of 50