6.3 Marine worms: flatworms, roundworms, and annelids
3 min read•july 22, 2024
Marine worms are fascinating creatures with diverse adaptations. From flat and round to segmented bodies, they've evolved unique features for life in aquatic environments. These worms play crucial roles in marine ecosystems, from filtering water to burrowing through sediments.
Beyond their ecological importance, marine worms have significant economic and medical impacts. They're used in aquaculture, serve as pollution indicators, and offer insights for biomedical research. However, some parasitic species can cause serious health issues in humans and animals.
Characteristics and Adaptations of Marine Worms
Characteristics of marine worms
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13.3 – Superphylum Lophotrochozoa: Flatworms, Rotifers, and Nemerteans – Biology 110 PSU Dubois View original
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Top images from around the web for Characteristics of marine worms
13.3 – Superphylum Lophotrochozoa: Flatworms, Rotifers, and Nemerteans – Biology 110 PSU Dubois View original
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Flatworms, Nematodes, and Arthropods | OpenStax: Concepts of Biology View original
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Superphylum Lophotrochozoa: Flatworms, Rotifers, and Nemerteans | OpenStax Biology 2e View original
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13.3 – Superphylum Lophotrochozoa: Flatworms, Rotifers, and Nemerteans – Biology 110 PSU Dubois View original
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Flatworms, Nematodes, and Arthropods | OpenStax: Concepts of Biology View original
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Have soft, dorsoventrally flattened bodies well-suited for crawling in tight spaces
Lack a true (body cavity) and are thus , with organs embedded in mesenchyme
Possess a blind gut with only one opening serving as both mouth and anus (planarians)
Rely on specialized flame cells for excretion and diffusion through the body surface for gas exchange
Some species have simple eyespots for light detection and sensory cells for chemical and mechanical stimuli
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Possess cylindrical, unsegmented bodies with tapered ends adapted for burrowing (hookworms)
Have a , a fluid-filled cavity between the digestive tract and body wall
Feature a complete digestive system with a mouth and anus, allowing for more efficient feeding
Secrete a thick, protective cuticle that provides support and defense against harsh environments
Possess specialized sensory organs called amphids for detecting chemical cues
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Have segmented bodies with a true coelom, allowing for efficient circulation and organ specialization
Possess well-developed closed circulatory systems with hearts and blood vessels for oxygen transport (earthworms)
Feature complex nervous systems with brains and ventral nerve cords for advanced sensory processing
Bear , tiny bristles on each segment that aid in locomotion by anchoring against the
Often have specialized head regions with sensory organs like eyes and antennae (polychaetes)
Exhibit remarkable regenerative abilities, able to regrow lost body parts (some oligochaetes)
Feeding Strategies and Ecological Roles
Feeding strategies in marine worms
Suspension feeding
Some annelids like feather duster worms use crown tentacles to filter suspended particles from the water
Deposit feeding
Many annelids (lugworms) and flatworms ingest sediment to consume organic detritus and microbes
Predation and scavenging
Predatory annelids (fireworms) and flatworms actively hunt small invertebrates or feed on carrion
Parasitic flatworms (flukes) and nematodes live in or on hosts, feeding on tissues or body fluids (hookworms)
Ecological roles of marine worms
Bioturbation
Burrowing worms mix and ventilate sediments, enhancing and sediment oxygenation
Nutrient
Worm waste products release nutrients like nitrogen and phosphorus, supporting primary production
Food web dynamics
Marine worms are important prey items, transferring energy to fish, crustaceans, and other predators
Habitat creation
Reef-building polychaetes secrete tubes that form complex structures, providing microhabitats for other species
Economic and Medical Significance
Economic and medical significance
Aquaculture
worms like Nereis are harvested for use as fishing bait and feed in shrimp farming
Bioindicators
Pollution-sensitive worms (some nematodes) serve as indicators of environmental degradation
Biomedical research
Planarians are studied as models for stem cell research and regenerative medicine due to their impressive regenerative capabilities
Parasitic infections
Marine flatworms (schistosomes) and nematodes can infect humans and animals, causing debilitating diseases (schistosomiasis, anisakiasis)