Worm Phyla
I. Phylum Platyhelminthes
A. General Traits
1. Flatworms
2. Bilateral symmetry
3. Soft bodied
4. Invertebrates
5. Examples: Tapeworms, Flukes, Planaria
B. Anatomy
1. No respiratory organs – uses diffusion
2. No circulatory organs
3. Distinct brain & central nervous system
4. Specialized digestive system
5. Protostome - mouth
6. Acoelomate
Flatworms - Acoelomates
C. Reproduction
1. Hermaphroditic
2. Complex lifecycles involving parasitism and host infestation.
D. Phylum Platyhelminthes Classes
1. Class Cestoda
Anterior end with hooks (SCOLEX)
Body Divided into segment (PROGLOTTIDS)
No digestive tract
Nutrients absorbed through skin
Parasitic – humans and animals
Acoelomate
Protostome
Example: Tapeworm
2. Class Turbellaria
3 000 species
Habitat: Aquatic (marine)
Parasitic/Commensalistic
Hermaphroditic
Acoelomate
Protostome
Pharynx
Example: Planarian
3.
Class Trematoda
1 000 Species
Hermaphroditic
Have Digestive System
All are Parasitic
Alternate between Intermediate And Definite Host
Protostome
Acoelomate
Example: Flukes
II. Phylum Nematoda
A. General Traits
1. Roundworms
2. Not segmented
3. Bilateral symmetry
4. Adapt to every ecological niche
5. Comprise 90% of life on sea floor
6. Mostly microscopic
7. Examples: Hookworm, Pinworms
8. Parasitic on humans and animals (infect as many as1 million people)
B. Anatomy
1. Parasitic
2. Complete digestive system
3. Deuterostome - anus
3. No respiratory
4. No circulatory system
5. Simple nervous system
a. main ventral nerve
b. smaller dorsal nerve cord
6. Simple sensory organs at ends
7. Pseudocoelomate
Round Worms - Pseudocoelomate
C. Reproduction
1. Sexual
2. Some Hermaphroditic
3. Males are smaller with bent tails.
D. Phylum Nematoda Classes
1. Class Adenophorea
Most Primitive of Round Worms
12 000 species worldwide
Pseudocoelomates
Size - microscopic to 3.25 ft
Habitat – wide variety worldwide
Some Parasitic
Hermaphroditic & Individual Sexes
Cycle carbon/ nitrogen an breakdown organic material in the soil
Protostome and Deuterostome
Examples: Whipworm, Trichina
2. Class Secernentea
Almost exclusively terrestrial
8 000 species worldwide
Parasitic of plants and animals
Pseudocoelomates
Size – can reach up to 30 ft long
Hermaphroditic & Individual Sexes
Protostome and Deuterostome
Examples: Hookworm, Heartworm
III. Phylum Annelida
A. General Traits
1. Segmented
2. Bilateral symmetry
3. Habitat: most wet areas
4. Size: 1 mm to 3 m
5. Example: Earthworm, leech
B. Anatomy
1. Invertebrates
2. Closed circulatory system
3. Protostome & Deuterostome
4. Digestive tract with a gut
5. Eucoeolmate
6. Has a nerve cord and ganglia
7. Photoreceptors (but not eyes)
8. Hard chitin body
Segmented Worms- Eucoelomate
C. Reproduction
1. Asexual
a. Fission - posterior part of worm breaks off forming a clone
b. Regeneration
2. Sexual
a. Hermaphroditic or have distinct sexes.
b. Aquatic - external fertilization.
c. Terrestrial - hermaphrodites which exchange gametes
D. Phylum Annelida Classes
1. Class Oligochaeta
10 000 known species
Eucoelomate
Protostome and Deuterostome
Size: 1/32 in. to 10 ft
Habitat: Soil environments
Hermaphroditic that cross-fertilize
Setae – stiff, bristle hairs on ventral surface
Closed Circulatory System
Example: Earthworm
2. Class Polychaeta
8 000 known marine species
Eucoelomate
Numerous setae
Protostome and Deuterostome
Size: 1/8 in. to 9 ft
Habitat: Marine and Fresh water; mud
Errant Polychaetes – active crawlers/ swimmers
Sedentary Polychaetes – live in burrows or tubes; some attach to rocks
Examples: lugworms, clam worms
3. Class Hirudinea
500 species
Predacious parasitic worms
Eucoelomate
Hermaphroditic
Anterior and Posterior suckers
Protostome and Deuterostome
Size: ½ in. to 8 ft.
2 to 10 eyes (photoreceptor clusters)
Closed Circulatory System
Fixed number of body segments – 34
Examples: Leeches