Planktonic organisms 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.
 
 
 
 

Developing invertebrates, 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.
 
 

Planktonic animals 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 and Links.