The nematode phylum includes horsehair worms, which are long thin worms that are parasites as larvae and live freely as adults. They can grow up to 3 feet in length. Horsehair worms have a cuticle layer and longitudinal muscles but no circulatory, respiratory or excretory systems. There are two classes - Nectonematoidea contains marine species that parasitize crustaceans as larvae and swim freely in coastal waters as adults. Gordioida contains the familiar 'hair worms' that parasitize insects and other arthropods as larvae and are commonly found in freshwater or moist soil as adults.

1. The Phylum
Nematomorpha

2. Nematomorpha
Etymology: from the Greek word
“Nema” for thread
“Morphe” for shape or form

3. GENERAL DESCRIPTION
They are called Horsehair Worms, because
they used to be found in horse watering
troughs and they look like the hairs from a
horses tail.
typically tan to black in color

4. GENERAL DESCRIPTION
They are long thin worms (1 to 3 mm
diameter and 3 ft in length)
bilaterally symmetrical, and
vermiform

5. GENERAL DESCRIPTION
Body possesses in a cuticle and
longitudinal muscles.
Has an intra-epidermal nervous
system with an anterior nerve ring.

6. GENERAL DESCRIPTION
has no circulatory, respiratory and
excretory systems
Its body possesses a through gut
which is normally non-functional.

7.  Nematomorphan larvae are parasitic,
eating and absorbing their hosts’ body
tissues in early stages.
MODE OF NUTRITION
 They are parasites of invertebrates,
though not necessarily aquatic ones.

8. MODE OF NUTRITION
 Feeding on nutrients from the bodily
fluids.
The larvae have a better
developed digestive system than the
adults.

9. Nematomorphans are dioecious and
reproduce sexually
REPRODUCTION
 Males have one or two testes which
open to cloaca via sperm duct

10. REPRODUCTION
 Females may have pair of elongated
ovaries, which open to the cloaca via
semina receptacle
 A female may lay millions of eggs
during breeding seasons.

11. Longitudinal muscles (no circular)
underlie cuticle. Move with
characteristic s-shaped movements.
LOCOMOTION

12. HABITAT
Nematomorphans are found in
aquatic or occasionally terrestrial
 Either aquatic individuals
themselves or within terrestrial
host
 Habitat regions:
 Saltwater or marine
 Freshwater

13. CLASSIFICATION
Class Nectonematoidea
 species are marine floating
worms
 are found in coastal, marine, and
open sea environments as adults
 are found as parasites
in decapod crustaceans as larva
 a dorsal and ventral nerve
cords

14. CLASSIFICATION
Class Nectonematoidea
 Cuticle possesses swimming bristles
 They are known from the waters of
Indonesia, Japan, New Zealand, the
Northern Atlantic, and the Mediterranean.
 parasitize marine invertebrates
 Single reproductive gland (as an
ovary or testes) that produces
gametes only.

15. CLASSIFICATION
Class Gordioida
 A dorsal and ventral nerve cords.
 Generally called hair worms.
 Only a ventral nerve cord.
 Are found in freshwater, most commonly
along the banks of ponds and streams,
and some are semi-aquatic and live in
damp soil.

16. CLASSIFICATION
Class Gordioida
 They are known from every continent,
with the exception of Antarctica.
 The most common host are grasshoppers,
crickets, and some beetles and cockroaches.
However, some are found in humans,
livestock, and pets.
 They utilize terrestrial arthropods and are free-
living and aquatic as adults.