Choanoflagellates Fungi ANIMALIA Choanoflagellates Porifera (sponges) ANIMALIA Multicellularity Ctenophora (comb jellies) Cnidaria (jellyfish, corals, sea anemones) Diploblasty Acoela (acoels) LOPHOTROCHOZOA Rotifera (rotifers) Loss of coelom Platyhelminthes Triploblasty (flatworms) Segmentation Annelida (segmented worms) PROTOSTOMES Protostome Mollusca BILATERIA development (snails, clams, squid) ECDYSOZOA Nematoda (roundworms) Cephalization, CNS, coelom Arthropoda Segmentation (insects, spiders, crustaceans) DEUTEROSTOMES DEUTEROSTOMES Radial symmetry Echinodermata (in adults) (sea stars, sand dollars) Deuterostome development Chordata Segmentation (vertebrates, tunicates) General Annelid Characteristics • Coelomate, Triploblastic • Protostome (lophotrochozoan) • Cephalization • Bodies are segmented, worm shaped • Setae (chaetae) • Closed circulatory system • Metanephridia • Complete digestive system • Marine, freshwater, terrestrial Phylum Annelida • Class Polychaeta (nearly all marine) • Class Clitellata – Subclass Oligochaeta (mostly terrestrial or freshwater) – Subclass Hirudinea (mostly freshwater, terrestrial) (Did clitellates also evolve from polychaete ancestors?) One Hypothesis… Is this is true, the Class Polychaeta is not monophyletic Phylum Annelida Class Clitellata Class Polychaeta Subclass Hirudinea 1 2 3 Class Clitellata Subclass Oligochaeta Earthworm Clitellum Metamerism: serial repetition of segments Septa (peritoneum) divide the coelom into compartments Septa Hydrostatic skeleton is partitioned Circular and Longitudinal Muscles Closed Circulatory System Earthworm Anatomy of an earthworm Annelids exhibit Cephalization Class Clitellata Earthworm nervous system Leech nervous system Subclass Oligochaeta Subclass Hirudinoidea The Prostomium has no conspicuous sensory structures. Complete Digestive Tract Earthworm cross-section Typhlosole, a dorsal fold in the intestine Earthworms play an essential role in aerating soil and in adding nutrients Deposit Feeders Metanephridia (tube open at both ends) Nephrostome (entrance) Nephridiopore (exit) Earthworm metanephridia anterior segment adjacent segment nephridiopore – to outside Oligochaete internal anatomy Oligochaetes have no specialized respiratory structures. Sexual reproduction in Oligochaetes (simultaneous hermaphrodites) Lumbricus Pheretima Lumbricus Eisenia Subclass Hirudinea • No setae or appendages • Anterior and posterior suckers • Few body segments – 33- 34, more flattened dorso- ventrally • No internal septa • Many are Ectoparasites Leech Subclass Hirudinea Anterior sucker, Freshwater leech Class Polychaeta Parapodium Nereis versicolor Many Setae Nereis versicolor Parapodia function in locomotion and gas exchange, are highly vascularized and increase the surface area of the body wall. Errant Polychaetes : Mobile Polychaete Parapodia Polychaete locomotion Oligochaetes Anatides medipapillata Nereis versicolor Ophiodromus pugettensis • Prostomium with tentacles, eyes, palps, cirri. Nereis The head of Nereis, a polychaete • Many have an extendable proboscis with chitonous jaws/teeth Nereis versicolor Nereis versicolor Sedentary Annelids Burrow or Tube Dwelling Suspension feeding in polychaetes Figure 13_09 Christmas-tree worms Christmas-tree worms – suspension feeders Feather duster worm Eudistylia polymorpha Eudistylia polymorpha Spirobranchus spinosus Arenicola, a deposit feeder, sedentary polychaete which burrows in soft sediments Deposit feeding in Amphitrite Amphitrite, A sedentary polychaete Extracted from burrow Spaghetti worm Feather Duster Worm, a marine polychaete https://www.youtube.com/watch?v=eS8OYF7isCU Thelepus crispus Thelepus crispus A polychaete worm Deposit feeding in the ice-cream cone worm Regeneration and asexual reproduction in some Polychaetes Syllis chaetopterid Figure 13_10 Epitoky Epitoky in Polychaetes Nereis epitoke Male Syllid epitoke Epitokous Platynereis-male with an opaque (sperm-filled) anterior and muscular posterior part with paddle- shaped parapodia. Figure 13_13 Beard worms – Family Siboglinidae vestimentiferan How do Siboglinids get nutrition? 1. External digestion of food particles by tentacles 2. Can take up DOM (dissolved organic matter) from sea water 3. Mutualistic Chemosynthetic bacteria Chemosynthesis CO2 + 4H2S + O2 (CH20)n + 4S + H2O •Bacteria in trophosome obtain energy by oxidizing the H2S or CH4 in the surrounding seawater. •Sulfides and methane diffuse across tentacles then delivered to the trophosome by hemoglobin. •Bacteria use energy they obtain from oxidizing these substrates to produce ATP. Then ATP is used to synthesize organic molecules from the carbon in CO2 (like in photosynthesis). Tevnia Riftia Riftia out of it’s tube .