Download Biosc 41 Announcements 10/13

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