12. ANNELIDA
Page 1: Title and Overview
Title: Annelida: The Metameric Body Form
Chapter: 13
Page 2: Copyright Information
Copyright © The McGraw-Hill Companies, Inc.
Permission required for reproduction or display
Photographs courtesy of Dr. Simon Foale, ARC Centre of Excellence for Coral Reef Studies, James Cook University, Queensland, Australia
Page 3: Copyright Information Continued
Similar copyright notice and permissions as page 2.
Page 4: Phylum Annelida
Characteristics:
Triploblastic, coelomate animals
Exhibit bilateral symmetry
Size ranges from 1 mm to 3 m in length
Possess ventral nerve cords
Have a closed circulatory system
Page 5: Key Features of Annelida
Segmented Body: Metameric structure
Setae Presence: Absent in leeches
Coelom: Divided by septa
Excretion: Nephridia in each segment (metanephridia or protonephridia)
Page 6: Metamerism
Definition: Segmental arrangement of body parts in an animal
Advantages:
Each segment can be controlled independently
Reduces the impact of injury on the organism
Allows specialization for functions such as feeding, locomotion, and reproduction
Page 7: Classes of Phylum Annelida
Three Main Classes:
Polychaeta: Mostly marine
Oligochaeta: Earthworms
Hirudinea: Leeches
Page 8: Class Polychaeta
Characteristics:
Mostly marine organisms
Typically range from 5-10 cm long
Largest class within the annelid phylum
Adapted to various habitats: under rocks, burrowers, and tube dwellers
Distinct features: parapodia and setae
Page 9: N/A
Page 10: Feather Duster Worm
Species: Sabella melanostigma
Habitat: Lives in a tube drilled through dead shell or limestone rock
Behavior: Intricate maroon tentacles will contract quickly at the slightest shadow
Class: Polychaeta, Sub-class: Sedentaria
Page 11: N/A
Page 12: Fireworm
No specific content provided.
Page 13: Polychaete Structure
Prostomium: Contains sensory structures like eyes, antennae, and palps
Peristomium: First body segment surrounding the mouth, bears sensory tentacles or cirri
Page 14: Detailed Polychaete Anatomy
Overview of digestive and structural features:
Jaw, tentacle, and everted pharynx
Palps and sensory organs
Intestinal structure and associated muscles
Coelomic epithelium and respiratory capillaries
Page 15: Polychaete Anatomy Illustrated
Diagram illustrating various structures of a polychaete worm, including:
Jaw, tenticles, eyes, and cirri
Page 16: Digestive System Functions
Feeding:
Predatory species: Evert proboscis (pharynx) to capture prey
Other feeding types: herbivores, scavengers, or filter feeders
Digestion: Long, straight intestine used for defecation
Page 17: Circulatory System
Type: Closed circulatory system
Components:
Anterior and ventral blood vessels, dorsal capillaries
Blood coloration can be colorless, green, or red
Page 18: Excretory System
Each segment contains a pair of excretory tubes known as metanephridia
Types of excretory systems include:
Protonephridia
Nephridial tubule
Gonoducts and openings for excretion
Page 19: Regeneration and Reproduction
Remarkable powers of regeneration: Ability to replace lost parts
Some species can sever themselves to escape predators
Asexual reproduction via budding; predominantly sexual reproduction
Fertilization: Typically external, example: Platynereis megalops
Page 20: Polychaete Anatomy Continued
Overview of structures including:
Prostomium with sensorial functions and mouth structures
Presence of ciliated bands and dorsal structures
Page 21: Class Hirudinea (Leeches)
Characteristics:
Anterior and posterior suckers, flattened body
Sense spots, nephridiopores, and specialized mouthparts
Habitat: Found in lakes and sluggish rivers
Page 22: Leech Feeding Adaptation
Leech as a parasite and predator:
Three teeth for cutting into the host
Use of anticoagulants to keep blood flowing
Long feeding durations with infrequent feeds
Page 23: Leech Locomotion
Utilizing anterior and posterior suckers for movement
Needs solid substrates for stable movement
Page 24: N/A
Page 25: Additional Resources
Type: Not specified
Page 26: Classes of Phylum Annelida Overview
Classes and Key Features:
Oligochaeta: Head reduced, no parapodia, segmented worms with setae (e.g., earthworms)
Polychaeta: Well-developed head, each segment typically has parapodia (tube-dwelling and free-living worms)
Hirudinea: Flattened body, reduced segmentation, and body structure featuring suckers, parasitic or scavenging nature
Page 27: Circulatory Systems
Comparison of circulatory mechanisms in annelids:
Fast blood flow through large-diameter vessels
Slower diffusion in smaller vessels
Page 28: Metamerism and Body Structure
Review of organizational body structures in Annelida:
Features of metamerism explained through septa and segments
Page 29: Setae and Parapodia
Setae: Bristles aiding in locomotion and burrow anchorage
Parapodia: Lateral extensions assisting in movement and gas exchange.