The burrowing of Nereis diversicolor O.F. Müller,together with some observations on Arenicola marina (L.) (Annelida: Polychaeta)

The mechanism of burrowing in Nereis diversicolor O.F. Müller is described. Proboscis eversion in order to make a hole in the substratum is accompanied by a coelomic pressure pulse of 1.2–7.5 kPa, compared with a value of ≈0.3 kPa during ambulatory activity. Forward movement of the tail in the later stages of burial is by longitudinal contraction, usually accompanied by a pulse of about 2 kPa. The septa appear to act as effective hydrostatic pressure barriers during burrowing.In the flange-proboscis sequences of Arenicola marina (L.) the coelomic pressure in the trunk during erection of the flanges is generally slightly higher than that in the head, while the reverse applies during the low-volume proboscis eversion. Major progression of the anterior usually occurs during the first flange-proboscis sequence of each cycle and that of the posterior early in the dilation sequence. External pressure recordings of irrigation-defaecation cycles are given.Nereis uses a similar method of burrowing to that of the free-moving Nephtys but the coelomic pulses of the former are lower, as in the rate of burial (about 0.02 cm s^?1) which is similar to that of Arenicola. Closure of the septa of Nereis during burial suggests that its burrowing mechanism is not as versatile as that of Nephtys.