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Biosc 41 Announcements 10/13 v Today’s lecture: Phyla Annelida and Nematoda v Today’s lab: Phyla Mollusca and Annelida v Wed: Quiz covering Phyla Platyhelminthes and Mollusca v Lecture Exam 2 Wed 10/22- Study guide posted by this Wed. v Lab Exam 2 Mon 10/27- Study guide posted by this Wed. Quick Platyhelminthes Review v What type of symmetry do animals in Phylum Platyhelminthes have? v Digestive system: mouth only (protostomes) v How does gas exchange take place? v What are protonephridia for? v What is the class of free-living flatworms? An example? v What are the classes of parasitic flatworms? Example? An Introduction to the Invertebrates (part…4?!) Annelida & Nematoda Reference: Chapter 33.3, 33.4 More Relationships Excavata SAR clade Archaeplastida Unikonta Slime molds Tubulinids Entamoebas Nucleariids Fungi Choanoflagellates Animals Lophophorates: Phyla Ectoprocta and Brachiopoda v v Characterized by a lophophore, a crown of ciliated tentacles around their mouth § Lophophorates have a true coelom Two lophophorates we haven’t talked about yet: phyla Ectoprocta and Brachiopoda Lophophorates: Phyla Ectoprocta and Brachiopoda v Phylum Ectoprocta (also called bryozoans) § Sessile colonial animals that superficially resemble hydrozoans- but have lophophore instead of “feeding tentacles” § A hard exoskeleton encases the colony, and some species are reef builders Lophophorates: Phyla Ectoprocta and Brachiopoda v Phylum Brachiopoda § Superficially resemble clams and other hinge-shelled molluscs § BUT the two halves of the shell are dorsal and ventral rather than lateral as in clams- and they have a true lophophore for filter feeding § Brachiopods are marine and attach to the seafloor by a stalk Lophophore Phylum Annelida (“little rings”) v Annelids § are segmented worms Bodies are composed of a series of fused rings v Annelids are true coelomates v The Phylum Annelida is divided into two Classes § § Polychaeta (polychaetes) Clitellata (often omitted, with subclasses considered their own classes!) § § Subclass Oligochaeta (earthworms and their relatives) Subclass Hirudinea (leeches) Hydrostatic Skeleton v Hydrostatic § § § § § § § Skeleton Except in leeches, coelom is filled with fluid and serves as a hydrostatic skeleton Fluid volume remains constant Contraction of longitudinal muscles causes body to shorten and expand Contraction of circular muscles causes body to narrow and lengthen By separating this force into sections, widening and elongation move the whole animal Alternate waves of contraction, or peristalsis, allow efficient burrowing Swimming annelids use undulatory movements Annelida – Class Polychaeta v Members of class Polychaeta have paddle-like parapodia that work as gills and aid in locomotion v Most polychaetes are marine Polychaete – Christmas Tree Worm Highly modified parapodia! Polychaeta - Osedax v “Bone-eating snotflower” v Feeds on whale carcasses Polychaeta - Osedax Video, Osedax worms on whale falls (~ 2 min): https://www.youtube.com/watch?v=URi8KccVkks Annelida – Class Clitellata, Subclass Oligochaeta v The Class Clitellata includes several sub-classes (which are often considered classes, with Clitellata omitted!) § Subclass Oligochaeta are named for relatively sparse chaetae (setae), bristles made of chitin § Earthworms eat through litter and soil, extracting nutrients as the organic and mineral material moves through the alimentary canal § Earthworms are hermaphrodites but do not self-fertilize § Some can reproduce by parthenogenesis § Rarely, some groups can regenerate if chopped at certain segments § Can lose tail section and still survive – but rare, usually wind up with 2 halves of one dead earthworm Figure 33.24 Cuticle Coelom Epidermis Septum (partition between segments) Circular muscle Metanephridium Longitudinal muscle Anus Dorsal vessel Chaetae Intestine Skin Ventral vessel Fused nerve cords Nephrostome Metanephridium Clitellum Esophagus Crop Pharynx Giant Australian earthworm Gizzard Cerebral ganglia Mouth Intestine Subpharyngeal Circulatory system vessels ganglion Ventral nerve cords with segmental ganglia Annelida – Subclass Hirudinea - Leeches v v v Most species of leeches live in fresh water; some are marine or terrestrial Leeches include detritivores, predators of invertebrates, and parasites that suck blood Parasitic leeches secrete a chemical called hirudin to prevent blood from coagulating § Once used in blood-letting – not such a good idea. § Now important in treating certain injuries Video, phylum Annelida (~ 13 min): http://shapeoflife.org/video/phyla/annelidspowerful-and-capable-worms Superphylum Ecdysozoa v v v v The most species-rich animal group Ecdysozoans are covered by a tough coat called a cuticle The cuticle is shed or molted through a process called ecdysis The two largest phyla are Nematoda and Arthropoda Phylum Nematoda (“roundworms”) v v v v Everywhere! § Free-living and parasitic (on both plants & animals) § Aquatic habitats, soil, moist tissues of plants, and in body fluids and tissues of animals Triploblastic, pseudocoelomate, protostomes § Possess an alimentary canal with mouth and anus § Rudimentary nervous system § Lack a circulatory system Reproduction in nematodes is usually sexual, by internal fertilization Caenorhabditis elegans is a model organism in research Parasitic Nematodes v Eggs § may be infective stage Pinworms (Enterobius vermicularis) v Larvae § § may be infective stage Hookworm (Necator americanus) Trichinella spiralis: trichinosis Nematodes: Eggs Infective for Humans Nematodes: Larvae Infective for Humans Figure 25.26 Figure 33.27 Encysted juveniles Muscle tissue 50 µm More Relationships Excavata SAR clade Archaeplastida Unikonta Slime molds Tubulinids Entamoebas Nucleariids Fungi Choanoflagellates Animals