Rotifera & Acanthocephala


Aschelminth Groups


Advances in Aschelminths

1. Digestive - all have a mouth and anus

2. Circulatory

3. Nervous - brain, nerve cords, ganglia

4. Skeletal - pseudocoel - hydrostatic

5. Cuticle or thickened epidermis

6. Reproduction - dioecious, parthenogenesis


Phylum Rotifera


Characteristics of Rotifera

1. Sack-shaped, elongate body, 0.1 to 1 mm

2. Anterior end bears ciliated organ - corona

3. The corona moves food into buccal tube:

buccal tube -> mastax -> intestine -> cloaca

4. May have well developed foot and toes (attachment and movement)

5. Lack a cuticle, but have a syncytial epidermis composed of actin filaments (some have a lorica)

6. Large pseudocoel, two pairs protonephridia

7. Nervous system: brain, antennal ganglia, paired nerve cords

8. Reproduction dioecious, parthenogenic


Rotifers: Life History and Ecology


Phylum Acanthocephala


Characteristics of Acanthocephala

1. Large pseudocoel, no digestive system

2. Spiny proboscis for attachment to host intestine

3. Dioecious - gonads suspended in pseudocoel by ligament sacs, fertilization is by copulation

4. Longitudinal retractor muscles

5. One pair of protonephridia open to gonopores (cloaca)

6. Fertilizated encapsulated egg develops into a spiny acanthor larva, which is eaten by intermediate host

7. Transmission to definitive host is by consumption of the infected intermediate host


Aschelminth Biology: Misfit Metazoans?