. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MECHANISM OF BURROWING IN ARENICOLA 371 0) 3 i/) lA 2! a "5 c L. 0) x. FIGURE 2. Recording of the pressures produced in sand by Arcnicola when burrowing against glass with the trunk almost completely beneath the surface. Flanging (F) and proboscis eversion (P) were marked by direct observation of the anterior segments. Synchronous recordings demonstrate that the negative pressures correspond to the pressure peaks in the coelom (Fig. Ib). At the commencement of burrowing the latter increase in amplitude with penetration
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MECHANISM OF BURROWING IN ARENICOLA 371 0) 3 i/) lA 2! a "5 c L. 0) x. FIGURE 2. Recording of the pressures produced in sand by Arcnicola when burrowing against glass with the trunk almost completely beneath the surface. Flanging (F) and proboscis eversion (P) were marked by direct observation of the anterior segments. Synchronous recordings demonstrate that the negative pressures correspond to the pressure peaks in the coelom (Fig. Ib). At the commencement of burrowing the latter increase in amplitude with penetration (Trueman, 1966a; Fig. 6) and a similar feature occurs in respect of the negative pressures (Fig. la, X). This indicates that until a firm anchorage is obtained, maximum pressures are not exerted on the substrate. The external pressure recorded fluctuates continuously between the negative peaks and it has not been possible to interpret these changes in detail. The most marked positive peak, following immediately after the negative pressure, may be due to the dilatant properties of the sand-water system. Proboscis eversion and the oc- currence of flanging were marked by visual observations, through the side of a glass tank. Flanging (Fig. 3b) was most clearly observed on the first three trunk- segments where the fleshy parapodial ridges each form an annulus which may be raised suddenly into a sharply projecting flange (Wells, 1944, 1961). Flanging and proboscis eversion were never observed at peak pressures but occurred between these (Fig. 2). Conversely the anterior 4 or 5 segments became very dilated when the maximum pressures were recorded (Fig. 3a). High pressures were clearly not synchronized with proboscis extrusion nor was there any apparent forward move- ment of the head of the worm at this phase of digging activity. It was previously (Trueman, 1966a) considered likely that the high coelomic pressure contributed to forward movement of the head of the worm but in the light
Size: 3062px × 816px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
