Kinorhyncha is a small phylum of marine animals, typically under 1 mm in length, that live among sediment grains. These minute invertebrates occur in many parts of the world’s seas and are most often found in muddy or sandy substrates. Because of their appearance and habitat they are commonly called “mud dragons.”
Description
Kinorhynchs are microscopic, segmented animals with a body divided into a retractable head (introvert), a short neck, and a trunk made up of eleven segments. The introvert bears rings of spines (scalids) used for grasping and movement. Their bodies are covered by a molted cuticle, and they lack specialized circulatory and respiratory organs.
Habitat and distribution
These animals live interstitially between particles of mud and sand, and have been recorded from shallow coastal areas down to the deep sea. They are true marine organisms, adapted to life within sediments at a wide range of depths.
Feeding and ecology
Different kinorhynch species feed on microscopic algae, detritus, and other organic material trapped in the sediment. Some species graze on diatoms, while others consume amorphous organic particles, contributing to the breakdown and recycling of organic matter in benthic environments.
Diversity and biology
About 150 recognized species of kinorhynchs have been described. Most species have separate sexes (dioecious), and development is generally direct, with juveniles resembling miniature adults. Kinorhyncha is placed among the molting animals (Ecdysozoa) and is studied for its distinctive anatomy and role in sedimentary ecosystems.