10/13/14 1 Biosc 41 Announcements 10/13 Today’s lecture: Phyla Annelida and Nematoda Today’s lab: Phyla Mollusca and Annelida Wed: Quiz covering Phyla Platyhelminthes and Mollusca Lecture Exam 2 Wed 10/22- Study guide posted by this Wed. Lab Exam 2 Mon 10/27- Study guide posted by this Wed. Quick Platyhelminthes Review What type of symmetry do animals in Phylum Platyhelminthes have? Digestive system: mouth only (protostomes) How does gas exchange take place? What are protonephridia for? What is the class of free-living flatworms? An example? 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 SAR clade Archaeplastida Unikonta Excavata Slime molds Tubulinids Entamoebas Nucleariids Fungi Choanoflagellates Animals Lophophorates: Phyla Ectoprocta and Brachiopoda 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 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
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10/13/14
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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?
v Characterized by a lophophore, a crown of ciliated tentacles around their mouth § Lophophorates have a true
coelom v 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
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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
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Video, Osedax worms on whale falls (~ 2 min): https://www.youtube.com/watch?v=URi8KccVkks
Polychaeta - Osedax 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
Epidermis
Circular muscle
Cuticle
Longitudinal muscle
Dorsal vessel
Chaetae
Intestine
Nephrostome
Fused nerve cords
Ventral vessel
Clitellum
Esophagus Pharynx
Crop
Metanephridium
Coelom
Septum (partition between segments)
Anus
Skin
Metanephridium
Intestine
Gizzard
Ventral nerve cords with segmental ganglia Circulatory
v Most species of leeches live in fresh water; some are marine or terrestrial
v Leeches include detritivores, predators of invertebrates, and parasites that suck blood
v 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