Download Pseudocoelomates: Round Worms

Pseudocoelomates:
Round Worms
Chapter 11
Round Worms
• 2 Main Phlya
– Nematoda “thread worm”
• ex: hookworms, pin worms, ascaris, filarial worms
– Rotifera “wheel -bearer”
Phylum Nematoda
Species: ~16,000
• One of the most abundant animals on
Earth
– 5 Billion per Acre of Fertile Garden
Soil
Food: Organic Matter
• Many are Parasitic
• Tissue of Animals & Plants
• Rotting Substances
• Recycle nutrients in soils &
bottom sediments
Phylum Nematoda
Reproduction
• Sexual
• Sperm is amoeboid
• Dioecious – males and females separate
• Males smaller than females (dimorphic)
• 100s -1000s of eggs per day
Lifestyles:
• Mostly parasitic
• Some free-living
Phylum Nematoda
Digestive Tract
• Complete digestive tract
• Mouth surrounded by lips
– that have sensory organs
• Mouth, teeth, jaws, buccal ‘mouth’ cavity,
pharynx, intestines, rectum, anus
Phylum Nematoda
Excretory System/Waste Removal
• 1 or 2 renette cells – glands absorb wastes
from pseudocoelom and empties them
outside through a excretory pore
• Osmoregulation of Nitrogen:
– Ammonia & Urea
Phylum Nematoda
Body:
• Size: microscopic – several meters
• Molt their cuticle
• Body wall has only longitudinal muscles
• Triploblastic
• Bilateral symmetry
• Unsegmented
• Pseudocoelomate
Phylum Nematoda
Nervous System
• Anterior nerve ring
• Neuroendocrine
secretions (hormones)
– Growth, molting, cuticle
formation,
metamorphosis
Phylum Rotifera
Phylum Rotifera
• Species:~2,000
• Ciliated corona surrounding mouth
• Muscular pharynx (AKA Mastax)
– Jaw-like function
– Parthenogenesis is common
• Unfertilized egg develops into
a new individual
• Freshwater or Marine
• Size: Very small! 0.1 - 0.5mm