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Diversity of Life – Animals ANNELIDA (earthworms, leeches, marine worms) A Phylogeny of the Animal Phyla Porifera No true tissues Cnidaria radial symmetry diploblastic Acoelomates Ctenophora Platyhelminthes Pseudocoelomates Rotifera Nematoda Nemertea Protostomes true tissues Mollusca Annelida Arthropoda Bilateral symmetry triploblastic Body cavity Lophophorate phyla Coelomates Deuterostomes Bryozoa Phoronida Brachiopoda Echinodermata Chordata Annelida - earthworms, leeches, marine worms Annelida - earthworms, leeches, marine worms Annelids are: • coelomates • segmented* Annelida - a significant improvement in body architecture SEGMENTATION Dividing the body into smaller repeated units Annelida - a significant improvement in body architecture SEGMENTATION - Why?? 1. Allows more precise movement - reorient and twist part of the body Annelida - a significant improvement in body architecture SEGMENTATION - Why?? 2. Allows muscle contraction without bulging mesoderm = muscle If muscle contracts without segments Remember the standard coelomate body plan. contracting area Annelida - a significant improvement in body architecture SEGMENTATION - Why?? 2. Allows muscle contraction without bulging If muscle contracts without segments If muscle contracts with segments Area of contraction is restricted Annelida - Who are they Oligochaetes - the earthworms All are terrestrial All use setae (hairs anchored) in the body wall to aid in locomotion Annelida - Who are they Polychaetes - the marine segmented worms All are marine All use parapodia to aid in locomotion Annelida - Who are they Hirudinea - leeches Several are parasites Segmentation is reduced Have sucker discs for attachment Annelida - Structure Longitudinal muscles – turn body side to side in locomotion Dorsal vessel – closed circulatory system, conducts blood through body Septum – partially isolates segments from one another Circular muscles – generate waves of contraction to allow the body to move forward Metanephridium – excretory organ Chetae - stiffened hairs that anchor in the substrate and aid in locomotion Ventral nerve cord Clitellum – thickened tissue used in reproduction Cerebral ganglion –”brain” Mouth Gizzard - Pharynx Crop Annelida - Structure Note repetition of structures Annelida - Locomotion Annelida – Aids to Locomotion Chaetae Parapodia Earthworm Reproduction Polychaetes Lugworm Christmas tree worm Fireworm Feather duster worm Hirudinea - Leeches Hirudinea - Leeches Note: reduced complexity in digestive system Annuli are not segments Leech - locomotion Leech Feeding Inject anticoagulant - hirudin (only about 10% feed on blood) A Possible Annelid Phylogeny Oligochaeta Hirudinea Polychaeta Taxa we have looked at so far Phylum Class Porifera Calcarea Demospongia Hexactinellida Platyhelminthes Turbellaria (free-living) Trematoda (flukes) Cestoda (tapeworms) Mollusca Polyplacophora (chitons) Gastropoda (snails,slugs) Bivalvia (clams, oysters) Cephalopoda (octopus, squid) Annelida Oligochaeta (earthworms) Hirudinea (leeches) Polychaeta (marine worms) Order
