Nematoda vs annelida

1. Nematoda vs Annelida

2. Core concept (Nematoda)

3. •Roundworms, phylum Nematoda, are
characterized by elongated cylindrical bodies
that are tapered at both ends and covered by
a tough cuticle.

4. •Nematodes are bilaterally symmetrical and
are the simplest animals with a complete
digestive tract with two openings: a mouth
and an anus, thus they have a tube-within-a-
tube body plan.

5. •These animals are pseudocoelomate,
possessing a pseudocoel located between the
endoderm and mesoderm, enabling them to
move freely than more primitive forms and it
provides more space for organs.

6. Core Concept (Annelida)
•The segmented worms, phylum Annelida, are
distinguished by bodies that are divided into
segments.

7. •Annelids have a tube-within-a-tube body plan.
The body wall, which is covered with
ectoderm, is the outer tube, while the
digestive tract, which is lined with endoderm,
makes up the inner tube.

8. •A fluid-filled cavity, the coelom, is found
between the inner and outer tubes. The
coelom is lined with mesoderm and
outgrowths from this hold the body organs in
place, allowing the development of a more
complex organization.
•

9. •The phylum contains three classes:
Polychaeta(marine sandworm), Oligochaeta
(earthworm) and Hirudinea (leech).

10. Keywords (Nematoda)
•Nematoda
•roundworms
•complete gut
•cuticle
•ganglion
•pseudocoel
•pseudocoelomate
•tube-within-a-tube body plan

11. Keywords (Annelida)
•Annelida
•Oligochaeta
•Polychaeta
•Hirudinea
•closed circulatory system
•coelom/coelomate
•ganglion/ganglia
•nephridia
•parapodia
•segmentation
•septum
•setae
•trochophore larva

12. Characteristics (Nematoda)
•the name: NEMA (thread) + ODA (like)
•smooth narrow cylindrical body tapered at
both ends and covered by a protective layer
called a cuticle
•bilaterally symmetrical, triploblastic,
pseudocoelomate

13. •pseudocoelom containins fluid that acts as a
blood vascular system that transport nutrients
throughout the body
•tube-within-a-tube body plan with the
development of a complete digestive tract, i.e.,
the gut is the inner tube which t is open at both
ends – mouth and anus, while the body wall is
the outer tube
•are among the most numerous animals ranging
from microscopic free-living forms to the larger
parasitic nematods

14. Structure and function
•Feeding – complete gut with two openings
(mouth and anus)
•Respiration and excretion of metabolic wastes –
through the body wall
•No internal transport – through diffusion
•Nervous system – several ganglia in the head
region, but no brain; simple sense organs
present, nerves extend from ganglia
•Movement – longitudinal muscles in strips down
the length of the body wall  thrashing
movement

15. Reproduction
•most are dioecious; females generally larger
than males
•internal fertilization
•zygote is resistant (capable of surviving harsh
conditions)
•development is direct in free-living forms;
parasitic forms have a complex life cycle with
two or three hosts
•

16. Examples
•Free-living nematodes
•Turbatrix aceti – vinegar eel
•C. elegans – soil nematode; used in research
•
•Parasitic nematodes
•Ascaris – infects intestines of pig, horse & man
•Filaria worm (Wuchereria bancrofti) – causes elephantiasis
•Trichina worm (Trichinella spiralis) – causes trichinosis; larvae encyst in
muscles
• Eyeworm (Loa loa) – infects tissues just below the skin
• Pinworm (Enterobius) – deposits eggs in anal region
•Hookworm (Ancylostoma and Necator) – infect people walking barefoot
on contaminated soil
•
•

17. Characteristics (annelid)
•The name: ANNELLUS (ring)  ringed/segmented
worms
•The body is divided externally and internally into
segments separated internally by a membrane
(septum), wherein most segments are identical except
for some that are modified to perform specific
functions; while segmentation is obvious externally as a
series of rings separating the segments.

18. •Annelids have elongated bodies that are bilaterally
symmetrical with a tube-within-a-tube body plan,
possessing a complete digestive tract/gut.
•Between the gut and other body organs there is a fluid-
filled cavity called the coelom which acts as a
hydrostatic skeleton, while the lining of the coelom
holds the organs in place.
•Annelids thrive in marine, freshwater & terrestrial
habitats; most are free-living, while a few species are
parasitic.
•

19. Structure and Function
•digestive system – complete gut; may be carnivorous,
herbivorous or detritus feeders
•respiratory system – through the skin or gills
•circulatory system – closed type (blood travels through
vessels)

20. •excretory system – metabolic waste via nephridia; solid
wastes through anus
•nervous system – ganglionic w/ dorsal brain & ventral
nerve cord
•muscular system – body wall contains muscles
(longitudinal and circular) for burrowing & swimming

21. Reproduction
•asexual by budding (rare)
•most reproduce sexually
–dioecious - through external fertilization (spawning)
–monoecious/hermaphroditic - through internal
fertilization
•CLITELLUM  specialized segment that secretes
mucus ring into w/c sperm & eggs are released
•

22. Taxonomy
•Class Polychaeta
–POLY (many) + CHAETA (bristles)
–paired paddle-like appendages (parapodia) that
are tipped w/ bristles
–w/ well-defined head (has eyes & antennae)
–e.g.marine annelids  sea mouse
–bloodworms
–marine sandworm (Nereis)

23. •Class Oligochaeta
–OLIGO (few) + CHAETA (bristles)
–bristles help in anchoring or burrowing
–most live in soil or fresh water, some marine
–e.g. earthworms (Lumbricus terrestris)
–tubifex worms

24. •Class Hirudinea
–includes leeches
–body flattened & tapered at both ends; w/o
bristles
–suckers for attaching to host (anterior & posterior)
–PROBOSCIS to penetrate the skin of the host
–fresh water, marine or terrestrial
–e.g. medicinal leech (Hirudo medicinalis) 
secretes HIRUDIN w/c prevents blood from
clotting (used to treat hematoma)