Siimaeläimet

Siimaeläimet is a Finnish term referring to a group of marine invertebrates belonging to the phylum Chaetognatha. These small, predatory animals are commonly known as arrow worms. They are found in all oceans from surface waters to the deep sea. Arrow worms are characterized by their transparent, torpedo-shaped bodies and a set of grasping spines around their mouths, which they use to capture planktonic prey. They possess a distinct head region, a trunk, and a tail, separated by a constriction.

The taxonomy of siimaeläimet places them in their own phylum, reflecting their unique evolutionary position. Despite their simple appearance, they are active hunters and play a significant role in the marine food web, primarily by consuming copepods and other small crustaceans. Their distribution is widespread, and different species inhabit various oceanic zones, making them important indicators of water mass and environmental conditions. Reproduction in siimaeläimet is typically hermaphroditic, though they cross-fertilize. Eggs are released into the water column, where they develop into larvae. Their ecological importance and widespread distribution contribute to their status as a well-studied group in marine biology.