copepod mouthparts (Box 7.2) is in the viscous regime of flow, that is, at low
Reynolds numbers. The aspect of this most obvious in their movies is that there is no
inertial “carry” of the flow after a given propulsive limb motion is complete. Water
moves while a limb applies force, but it stops almost instantaneously when the force
is off. If a particle advances toward the body, and the animal stops its limb motions,
the particle stops also. It does not swirl off in residual eddies. Thus, the effect of
recurring limb movements is a sequence of step-like advances of the surrounding
water and contained particles up to and around the searching animal.
Box 7.2 Feeding limbs of Calanus
(^) To understand Koehl and Strickler (1981), you the must know the head limbs of copepods (shown in
Box Fig. 7.2.1).
Box Fig. 7.2.1 Lateral view of feeding limbs of Calanus.
(^) (After Cannon 1928.)
(^) The most anterior pair are the antennules, unbranched (uniramous), tubular limbs that stick out to the
sides of the body during feeding. In Box Figure 7.2.1 they are lopped off and appear as circles. The
biramous antennae are major generators of the feeding “current” which moves water past the body to
be searched for food. The mandibular palps are also involved in generating the feeding current. An
“endite” (a side branch off one segment), termed the mandibular gnathobase, at the base of each
mandible bears the copepod’s teeth and extends into the mouth under the labrum. The palps operate
almost independently of the gnathobases. Next are the maxillules (or first maxillae), which are large
flaps looking a little like elephant ears. A basal endite on each maxillule bears a comb of very stout