ostracod

Ostracods are a class of small crustaceans, sometimes known as seed shrimp. They are typically very small, with most species ranging from 0.1 to 2.0 millimeters in length. Their most distinctive feature is a bivalved carapace, or shell, which encloses their body and limbs, resembling a tiny clam.

They inhabit a wide variety of aquatic environments, including both freshwater and marine habitats worldwide. Ostracods can be found from the deepest ocean trenches to temporary puddles. They are important components of the ecosystem, serving as a food source for many fish and other aquatic animals. Their diet is varied, including algae, detritus, and smaller organisms.

Ostracods are noteworthy for their extensive fossil record. Because their calcareous shells fossilize easily, they are abundant in sedimentary rocks dating back over 450 million years. This makes them extremely valuable to geologists and paleontologists for dating rock layers and reconstructing past environmental conditions, such as water temperature and salinity.

Some species of ostracods are bioluminescent and can produce light. They release a luminescent secretion into the water as a defense mechanism to confuse predators.

Reproduction methods vary; some species reproduce sexually, while others are parthenogenetic, meaning females can produce offspring without fertilization. Due to their diversity, abundance, and long evolutionary history, ostracods are a significant group for scientific study in both ecology and paleontology.