Seed shrimp (Ostracoda) are a diverse class of tiny, bivalve crustaceans found in nearly every aquatic environment across the globe. They are encased in a protective, clam-like shell, or carapace, which gives them their common name due to their resemblance to a small seed. Ranging in size from 0.2 millimeters up to about 3 millimeters, seed shrimp form a globally ubiquitous group of invertebrates that play a significant role in aquatic food webs.
Diverse Diets of Seed Shrimp
The diet of the seed shrimp is varied and depends on the specific species and its habitat, ranging from passive scavenging to active predation. A primary food source for many Ostracods is organic detritus, consisting of decaying plant matter, dead algae, and fine animal remains that settle on the substrate. As deposit feeders, they consume this material, making them effective recyclers of biological waste.
Microscopic organisms, including bacteria, fungi, and protozoa, form a substantial part of their nutritional intake. Many species graze on periphyton—the complex mixture of algae and microbes that grows on submerged surfaces. This grazing action allows them to harvest a nutrient-dense biofilm.
Other species are effective herbivores, consuming algae and diatoms directly. The diet can also include a predatory component, especially among larger species, which actively hunt smaller invertebrates, such as rotifers or other Ostracods.
Specialized Feeding Methods
Seed shrimp utilize specialized appendages to acquire and process the food they consume. They employ modified antennae and mouthparts to interact with their environment, which dictates their ability to switch between different feeding modes.
Many species are classified as filter feeders, using their appendages to create water currents that draw suspended particles toward their mouthparts. This filtration allows them to capture fine particles like free-floating bacteria and small algae from the water column.
Other species employ scraping or grazing, utilizing specialized limbs to detach biofilms and detritus directly from surfaces of sediment or submerged vegetation. The food particles are then transferred to the mouth area for processing.
Once the food is captured, the seed shrimp uses a pair of mandibles and maxillae for mastication. These complex mouthparts effectively grind the food material into a digestible slurry before ingestion. Some predatory species possess strong mouthparts capable of grinding up the hard exoskeletons of their prey.
Ecological Role as Detritivores and Prey
The feeding habits of seed shrimp give them a function in the aquatic ecosystem, primarily as detritivores and as prey. By consuming organic detritus, they play a crucial part in nutrient cycling, breaking down dead material and recycling nutrients back into the water.
As an abundant group, Ostracods serve as a link in the food chain, transferring energy to higher trophic levels. They are a common food source for a wide array of aquatic predators, including fish (such as guppies and platies) and amphibians like newts. Wading birds and ducks also frequently consume seed shrimp, making them an important component in the diets of migratory waterfowl.