Ringmaskar

Ringmaskar, also known as annelids, are a large and diverse phylum of segmented worms. Their bodies are divided into serial segments (metameres), often giving a ringed appearance, and most possess bristle-like structures called chaetae. The segmentation enables flexibility and complex movement.

Annelida includes several major groups: Polychaeta (polychaetes), which are predominantly marine; and the Clitellata, which comprises earthworms (oligochaetes) and leeches (Hirudinea). While polychaetes are mostly marine and often have numerous setae and parapodia, earthworms and leeches tend to live in freshwater or terrestrial habitats and lack well-developed parapodia.

Morphology: The body shows a clear head and trunk with a pygidium; many segments bear chaetae; polychaetes often have paired lateral appendages called parapodia used in locomotion and respiration; clitellates lack parapodia and have a clitellum for reproduction.

Ecology: Annelids occupy a wide range of habitats: marine sediments, freshwater bottoms, and soil. Roles include detritivores, scavengers, filter feeders, and predators. They contribute to soil structure and nutrient cycling and serve as food for many other animals.

Reproduction and development: Reproduction is diverse. Some species are hermaphroditic, others gonochoric. Most release eggs and sperm into the environment or care for brood; developmental stages range from free-swimming trochophore larvae to direct development in clitellates.

Significance: Ringmaskar are important indicators of environmental health and are used in ecological and toxicological studies. Leech species have medically valuable uses, including therapeutic applications in microsurgery and wound care.