9780521861724htl 1..2

rather than a general increase in the size of existing polyps. This method has its
limitations, however, because while it enables escape from a size limit imposed
by energetic constraints, other size limits may well be imposed, for instance, by
suitable ambient velocities, substrata, local food depletion, local competition,
or ‘self-shading’ (Sebens,1982, 1987; Kim & Lasker, 1998 ; Okamura, Harmelin &
Jackson, 2001 ).
A method available to non-colonial animals is to modify existing body parts to
act as feeding structures (sometimes even to the exclusion of their original
function). Examples include the use of locomotory arms raised into the current
in brittle stars, and the limbs of some euphausiid shrimps. By using such

(a)

(b)

25

45

40

35

30

25

20

15

10

5

0

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07

20

15

10

5

0

0 0.005 0.01 0.015 0.02 0.025 0.03

Energetic intake/cost (mJ/s)

Energetic intake/cost (mJ/s)

Body size (mass, kg)

Body size (mass, kg)

Figure 2.2Cost:gain curves for two suspension feeders: (a) the musselMytilus edulis, and
(b) the sea anemoneAnthopleura xanthogrammica. Solid lines are gain functions, broken
lines are cost functions. Redrawn from Sebens ( 1987 ).

BODY SIZE AND SUSPENSION FEEDING 23