Phylum Nemertea & Phylum
Chaetognatha
Ribbon Worms
Arrow Worms
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Phylum Nemertea & Chaetognatha
Phylum Nemertea

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Long, slender, soft unsegmented worms with an
eversible proboscis
Phylum Nemertea & Chaetognatha
The Proboscis
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Phylum Nemertea & Chaetognatha
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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Phylum Nemertea & Chaetognatha
Reproduction
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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
Phylum Nemertea & Chaetognatha
Local Representatives

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Milky ribbon worm (Cerebratulus lacteus)
Phylum Nemertea & Chaetognatha
Phylum Chaetognatha (Arrow
Worms)

Defining Characteristics
–
–
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A series of curved
chitinous grasping spines
on both sides of the head,
for seizing prey
Lateral stabilizing fins
Phylum Nemertea & Chaetognatha
Chaetognaths Habits

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Living Chaetognaths
are almost invisible
in the water
Possess two eyes
that are useful for
sensing motion and
light intensity
Phylum Nemertea & Chaetognatha
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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Phylum Nemertea & Chaetognatha
Reproduction
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Phylum Nemertea & Chaetognatha