Phylum Nemertea & Chaetognatha 1 Phylum Nemertea & Phylum Chaetognatha Ribbon Worms Arrow Worms.

Phylum Nemertea & Chaetognatha 1

Phylum Nemertea & Phylum Chaetognatha

Ribbon Worms

Arrow Worms

Phylum Nemertea & Chaetognatha

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Phylum Nemertea

Long, slender, soft unsegmented worms with an eversible proboscis


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The Proboscis


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Digestion and Circulatory Systems

Lacks an exoskeleton; skin is densely ciliated which circulates water for gas exchange

Eyespots are located on the head near the brain

Food is digested rapidly and processed in a linear digestive tract


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Reproduction

Sexes are separate with fertilization occurring in the water column

– Usually solitary animals that aggregate at spawning

– Long lived free-swimming larvae pilidium

Great powers of regeneration


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Local Representatives

Milky ribbon worm (Cerebratulus lacteus)


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Phylum Chaetognatha (Arrow Worms)

Defining Characteristics– A series of curved

chitinous grasping spines on both sides of the head, for seizing prey

– Lateral stabilizing fins


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Chaetognaths Habits

Living Chaetognaths are almost invisible in the water

Possess two eyes that are useful for sensing motion and light intensity


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Chaetognatha Feeding

A prey item is sensed by cilia along the body

Feed on copepods, larval crustaceans, young fish and each other

Can occur in very high concentrations several hundred per cubic meter

Can have substantial effects on eggs and larvae some of which are commercially important


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Reproduction

Phylum Nemertea & Chaetognatha 1 Phylum Nemertea & Phylum Chaetognatha Ribbon Worms Arrow Worms.

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