Page 275 - (DK) Ocean - The Definitive Visual Guide

RIBBON WORMS 273

Ribbon Worms Anatomy stylet proboscis nerve ganglion

Nemertean worms have a long, nerve
excretory
DOMAIN Eucarya unsegmented body with strong muscles in organs
ALSO CALLED NEMERTEAN worms,
the body wall that can shorten the worm to a
KINGDOM Animalia ribbon worms can reach great lengths proboscis
fraction of its full length. Unlike flatworms, ribbon sheath
PHYLUM Nemertea of at least 160 ft (50 m), although worms have blood vessels and a complete gut with blood
many are small and inconspicuous. vessel
CLASSES 2 mouth and anus. It is often difficult to distinguish
While they are commonly slightly between the front and rear end of the worm, but most ovary
SPECIES 1,358
flattened, the longest are cylindrical species have many simple eyes at the front. The most
and are often called bootlace worms. The majority of ribbon characteristic feature of these worms is a strong, tubular
worms live in the sea under rocks, among undergrowth or in structure called a proboscis that lies in a sheath above
the gut. It can be thrust out by hydrostatic pressure, gut
sediment, and some are parasitic. A few species live inside
either through the mouth or a separate
the shells of mollusks and crabs. BODY SECTION
opening, and is used to capture prey.
Ribbon worms have no body cavity
In some species, the proboscis is or gills; a simple circulatory system
armed with a sharp stylet. carries oxygen around the body.
Reproduction
Most marine ribbon worms have separate sexes and their
numerous, simple gonads produce either eggs or sperm.
These are usually shed into the sea through pores along the
sides of the body. Some species cocoon themselves together
in a mucous net where the eggs are duly fertilized. In
some types of ribbon worms, the eggs develop directly
into juvenile worms, while others initially hatch into
various types of larvae. The long,
fragile bodies of ribbon worms tend SWIMMING LARVA
to break easily but they have the useful Some ribbon worms
WARNING PATTERN ability to regenerate any lost parts. Some develop from a
Some ribbon worms have bright patterns species even use regeneration as a method planktonic larva called
that may serve as a warning to predators a pilidium. It is able to
that they are toxic. Drab-colored species of asexual reproduction, where the body swim by beating hairlike
only emerge at night to hunt. breaks up into several pieces and each structures, called cilia.
piece develops a new head and tail.

One of the most strikingly colored The bootlace worm makes up for
CLASS ANOPLA CLASS ANOPLA
ribbon worms, the football jersey its rather drab brown color by its
Football Jersey Worm worm has a patterning of longitudinal Bootlace Worm incredible length. Only a fraction of
white lines and regularly spaced white an inch in diameter, it reaches
rings. It may be found lying in an at least 33 ft (10 m) in length, and is
Tubulanus annulatus Lineus longissimus
LENGTH Up to 30 in untidy pile beneath stones on the LENGTH one of the longest animals known.
(75 cm) lower shore and may also be seen Up to 180 ft (55 m) On the shore it appears as a writhing
DEPTH 0–130 ft scavenging when the tide is out. DEPTH mass of knots lying on muddy sediment
(0–40 m) More usually it lives below the shore Intertidal beneath boulders. Like all anoplan
HABITAT Gravel, stones, on almost any type of seabed, HABITAT worms, it has its mouth behind the
and sediment including mud, sand, and shell gravel. Sediments and stones brain. This worm is difficult to pick up,
DISTRIBUTION Cold and temperate waters of north To camouflage itself, it secretes a DISTRIBUTION Temperate waters of northeast because it exudes large amounts of
Atlantic and north Pacific mucous tube that becomes covered Atlantic mucus when handled.
in surrounding sediment.

CLASS ENOPLA
Ribbon Worm

Nipponnemertes pulcher
LENGTH Up to 3 / 2 in
1
(9 cm)
DEPTH 0–1,900 ft
(0–570 m)
HABITAT Coarse
sediments
DISTRIBUTION Temperate and cold waters of Arctic,
Atlantic, Pacific and Southern oceans

This worm belongs to a class of beneath. This species has a distinctive,
nemertean worms called enoplan shield-shaped head with numerous
ribbon worms, whose mouth is eyes along its edges. The number of
located in front of the brain. eyes increases with age. It is usually
Nipponnemertes pulcher has a short, seen when dredged up by scientists OCEAN LIFE
stout body with a width of up to /4 in from the coarse sediments in which
1
(5 mm) that tapers to a pointed tail. it lives, but is sometimes found
The coloration varies from pink beneath stones on the lower shore.
to orange or deep red and is paler Its full distribution is unknown.