1. Pseudocoelomates
Aschelminths

2. Achelminth Phyla Gastrotricha Rotifera Kinorhyncha Nematoda
Nematomorpha
Acanthocephala
Loricifera
Priapulida
Entoprocta

3. Pseudocoelomates Define pseudocoelomate.
formed directly from the cavity of the blastula
The cavity is small
Mostly filled with intestine and oviducts or testes.

4. Gastrotricha Microscopic Marine and freshwater species
Common in lakes, ponds and seashore sands

5. Rotifera Ciliated crown or corona at the anterior end
Carnivorous or parasitic
Most common in freshwater environments
Body structure:
Head has corona
Trunk has ridged plates and spines
Foot has toes for attachment.

6. Rotifera

7. Kinorhyncha About 150 species Lives in marine sediment
Uses head as an anchor, pulls body after it.
Sexes are separate
Feed on algae and bacteria

8. Nematodes bilaterally symmetrical worm-like
surrounded by a cuticle secreted by epidermal cells
longitudinal muscles only

9. Nervous System - Nematodes
Simple ring of nervous tissue around pharynx
dorsal and ventral nerve cords running the length of the body

10. Nematode Movement Contract longitudinal muscles
High internal pressure causes the body to flex
Moves by thrashing back and forth
No cilia or flagella

11. Excretory Systems
Some have specialized cells that excrete nitrogenous wastes
Others have canals
Others have canals plus specialized cells
Nematodes do not have flame cells

12. Nematode Reproduction
Most nematodes are dioecious
Males use special copulatory spines
The sperm move by pseudopodia, like amoebas

13. Nematode Diversity Close to 500,000 species
Some species are generalists
Others are much more specialized -
one species of nematode is known only from felt coasters placed under beer mugs in a few towns in Germany.

14. Nematode Lifestyles Many free living Many also parasitic
Play critical ecological roles as decomposers and predators on microorganisms

15. Nematode-Caused Diseases
Roundworms - more than ½ the world's humans
Hookworms
Trichinosis
Pinworms infestations - extremely common parasite in the United States
can be transmitted from human to human by eggs floating in household dust
Filariasis (elephantiasis)
Onchocerciasis (river blindness).

16. Nematomorpha – Horsehair Worms or Gordian Worms
Up to 1m long, but very slender animals (1-3mm).
Free-living as adults
Often find adults in very clean streams

17. Juveniles are Arthropod Parasites

18. Acanthocephala - spiny headed worms
2-host parasites
Must have invertebrate host
Spiny protrusible proboscis
About 1150 species
Dioecious
Both circular and longitudinal muscles

19. Acanthocephalans - Nutrition
Nutrition by diffusion
Proboscis attaches to host intestine
Cause extensive damage to the intestinal walls
Economic importance: Some forms cause serious discomfort and ill-health to domestic livestock

20. Excretion Reproduction Protonephridia lined with flame cells
Reproductive structures are contained in strange ligament sacs.
In males two testes are contained within this sheath.

21. Loricifera Discovered in 1974 Dioecious Have a large brain
Little else is known about them.

22. Priapulida – The Penis Worms
Only 9 species
All marine worms
Found in colder water
Predaceous
Fossils date back to Middle Cambrian.

23. Entoprocta (Bryozoa) Ciliary feeding device - LOPHOPHORE
Were known as Bryozoa (moss animals)
4000 species
Few > 0.5 mm long
All aquatic (marine and freshwater)

24. Ectoproct Feeding

25. Entoprocta Most are colonial
Lives in secreted exoskeleton (zoecium) that may be:
Gelatinous
Chitinous
Stiffened with calcium
Impregnated with sand.
Some ectoprocts could be mistaken for hydroids but their tentacles are ciliated.

26. Ectoproct Colony