. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 370 E. R. TRUEMAN Worms were allowed to burrow over a glass tube (3 mm. bore) buried in the sand with its external opening covered by a coarse nylon mesh to prevent entry of sand grains. This was connected by pressure tubing to the transducer, and pressure applied to the adjacent sand either by a plunger or by an Arenicola burrowing caused a negative response. The explanation of this may lie in the dilatant proper- ties of the sand (Chapman and Newell, 1947), for the applied pressure disturbs the packing of the sand-water sy
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 370 E. R. TRUEMAN Worms were allowed to burrow over a glass tube (3 mm. bore) buried in the sand with its external opening covered by a coarse nylon mesh to prevent entry of sand grains. This was connected by pressure tubing to the transducer, and pressure applied to the adjacent sand either by a plunger or by an Arenicola burrowing caused a negative response. The explanation of this may lie in the dilatant proper- ties of the sand (Chapman and Newell, 1947), for the applied pressure disturbs the packing of the sand-water system and tends to cause water to be drawn in. In a full account of this technique (Hoggarth and Trueman, 1966) it is emphasized that all recordings must be interpreted by direct visual observations but that with this proviso it serves as a useful method of determining the activity of an animal, invisible beneath the sand yet without any obstruction by electrodes. Although bur- rowing was recorded in this manner for about 50 worms, direct observations of burrowing movements were only satisfactorily made on 5 occasions when the events were marked on the recording by means of a manually operated key. Coelomic pressures during burrowing were recorded as previously with a Bourdon transducer obtained from the E. & M. Instrument Company Inc. (Trueman, 1966a). EXPERIMENTAL RESULTS The recording of external pressures derived from an Arenicola burrowing in sand covered by several cm. of water consists of a series of negative pressures whose amplitude varies with the distance of the worm from the recording device. These pressures were observed to correspond to the swelling of the anterior seg- ments and to a marked increase in the turgidity of the entire trunk region (Fig. la). i i—I—i—I—i—i—i. -1 5s FIGURE 1. Recordings of the pressures produced by Arenicola in sand (external) and in the coelom during burrowing, a, sequence from the commencement of burrowing (extreme left
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
