86
H. U. Riisgard and P. Kamermans
4.2.1 Suspension-Feeding Behaviour
Observations by Riisgard (1991) of feeding behaviour in Nereis diversicolor
were carried out in glass tubes immersed in seawater (Fig. 4.2). Within 5 to
20 min after adding a suspension of algal cells, the worm moved to one end of
the glass tube where it fixed mucus threads to the glass wall forming the
circular opening of a net-bag. The net was completed as the worm slowly
retreated down the tube moving its anterior end from side to side in semicircles. During construction of the funnel-shaped net-bag, and for a period (5
to 15 min) after the bag was completed, the ragworm pumped water through
the net by vigorously undulating its body. Particles suspended in the inhalant
water were retained by the net and, after the period of pumping, the worm
moved forward to swallow the net-bag and its entrapped food particles.
4.2.2 Mucus-Net and Particle-Retention Efficiency
The structure of the' food-trapping net of Nereis diversicolor was studied by
Riisgard et al. (1992). Electron micrographs of the filter-net structure showed
(a)
r-----'
L _____ .J
(b)
er eis
mucus net
(c)
glass tube
I
Fig. 4.2. Nereis diversicolor lodged in a glass tube. a The undulating body movements
produce a water current that is filtered through a mucous net-bag made visible by means
of suspended carmine powder. b Magnification of anterior end of the same worm. c The
worm is swallowing the mucous net-bag 3min after photograph a was taken. (Riisgard
1991)
H. U. Riisgard and P. Kamermans
4.2.1 Suspension-Feeding Behaviour
Observations by Riisgard (1991) of feeding behaviour in Nereis diversicolor
were carried out in glass tubes immersed in seawater (Fig. 4.2). Within 5 to
20 min after adding a suspension of algal cells, the worm moved to one end of
the glass tube where it fixed mucus threads to the glass wall forming the
circular opening of a net-bag. The net was completed as the worm slowly
retreated down the tube moving its anterior end from side to side in semicircles. During construction of the funnel-shaped net-bag, and for a period (5
to 15 min) after the bag was completed, the ragworm pumped water through
the net by vigorously undulating its body. Particles suspended in the inhalant
water were retained by the net and, after the period of pumping, the worm
moved forward to swallow the net-bag and its entrapped food particles.
4.2.2 Mucus-Net and Particle-Retention Efficiency
The structure of the' food-trapping net of Nereis diversicolor was studied by
Riisgard et al. (1992). Electron micrographs of the filter-net structure showed
(a)
r-----'
L _____ .J
(b)
er eis
mucus net
(c)
glass tube
I
Fig. 4.2. Nereis diversicolor lodged in a glass tube. a The undulating body movements
produce a water current that is filtered through a mucous net-bag made visible by means
of suspended carmine powder. b Magnification of anterior end of the same worm. c The
worm is swallowing the mucous net-bag 3min after photograph a was taken. (Riisgard
1991)