gather food in a variety of ways, from preying directly on other planktonic
creatures to grazing on phytoplankton and detritus. Jellyfish and
other drifting carnivores like ctenophores use
sticky or stinging cells to capture their food, while larvaceans cast a
mucus net to ensnare prey and filter out edible items. Copepods are
raptorial predators, actively scanning for tasty prey and then using their
fine locomotion skills to grab them. Similarly, different kinds
of animals rely on various cues--including chemical, visual, and physical--to
detect possible food sources. For example, copepods respond
to the chemicals associated with phytoplankton cells.
or larvae, may not feed at all. Veligers of the gastropod Nucella
and the larvae of the bloodstar, Henricia are known as "lecithotrophic"
because they rely entirely on energy stored in the egg. Many other
larvae, such as those of the ochre seastar Pisaster and the acorn
barnacle Balanus glandula, are "planktotrophic," meaning that they
capture food for development and metamorphosis into adulthood. Barnacle
nauplii use appendages to sieve appropriately sized particles from the
water column. The young of clams and snails, known as veligers, use opposing
bands of cilia to filter food particles into a "food groove" that leads
to the mouth. Polychaete young use cilia as well, sweeping food particles
of a desirable size towards the mouth. Some developing echinoderms,
such as sea urchin and sand dollar larvae, use well-developed ëarmsí
to sweep food into their mouths.
in turn serve as important food for other members of marine food webs.
Copepods, perhaps the most abundant type of animal in the world's oceans,
sustain many marine fish populations. On completely different spatial
scale, baleen whales, such as the humpback whale, consume 1.5 tons (1,361
kg) of planktonic animals and small fish each day. In intertidal
communities, sessile animals such as barnacles and anemones rely on planktonic
organisms for food, as well.
The feeding ecology
of planktonic animals is of great interest to many types of scientists.
Evolutionary biologists ask questions such as, "How do larvae with different
feeding structure capture prey? Are some structures more efficient
than others?" Ecologists may be interested in questions such as "What
environmental conditions, such as current velocity, might influence feeding
efficiency? Does competition for food resources limit growth?"
Clearly, investigations of plankton span many branches of marine science,
both biological and physical. To learn more about plankton-related
research, check out our Literature