Ch 33.6, 42.1, 42.5, 44.3 Pseudocoelomates “soo-doe-see-low-mates”
description
Transcript of Ch 33.6, 42.1, 42.5, 44.3 Pseudocoelomates “soo-doe-see-low-mates”
Acrobeles complexus
Ch 33.6, 42.1, 42.5, 44.3 Ch 33.6, 42.1, 42.5, 44.3 Pseudocoelomates Pseudocoelomates “soo-
doe-see-low-mates”
PseudocoelomatesPseudocoelomates• 9 phyla:
– Nematoda– Rotifera– Gastrotrichia– Nematomorpha– Acanthocephala– Loricifera– Kinoryncha– Priapulida– Entoprocta
PseudocoelomatesPseudocoelomates
Plant ectoparasite
A. lumbricoides
• A heterogeneous group: – Size: microscopic several
meters– some are exclusively marine;
some (e.g., nematodes) live in a variety of habitats, esp. soil); and some are exclusively parasitic
PseudocoelomatesPseudocoelomates• Common characteristics:
1. Pseudocoelom2. Eutely3. complete digestive tract (mouth and
anus)
Common characteristics: 1) Pseudocoelom
• body cavity (pseudocoelom/ pseudocoel)
• a space b/w gut and mesodermal components of body wall
• Body cavity is not lined with a mesodermal sheet – Does not cover inner surface of body wall
Common characteristics: 1) Pseudocoelom
• No muscular tissue associated with gut tract
• No membranes suspend organs in body cavity
• Pseudocoelom is spacious, fluid-filled– Contains visceral organs– Forms hydrostatic skeleton
Evolutionary advantages of pseudocoel:– Greater freedom of movement– Space for development and
differentiation of organ systems (ie. digestive, excretory)•differentiation: process by which cells
become different, specialized– Simple means of circulation/distribution
of materials throughout body– Storage place for waste products to be
discharged to outside– Hydrostatic skeleton
•Fluid enclosed by muscular wall support
Common characteristics: 2) Eutely
• Body composed of constant number of somatic cells (or nuclei) in adults
http://www.wormatlas.org/handbook/alimentary/alimentary2.htm
Common characteristics: 3) complete digestive tract (mouth and
anus)• Most other higher animals
Do these questions Do these questions now…now…
• What type of germ layer lines the pseudocoelom in nematode embryos?
• What organ systems are present/absent in pseudocoelomates
• What are the advantages of having a pseudocoelom vs. no coelom?
• Organ systems present:– Digestive system– Excretory system– Nervous system– Reproductive system
• Organ systems absent:– Circulatory system– Respiratory system
PseudocoelomatesPseudocoelomates
Phylum NematodaPhylum Nematoda
The roundworms
Phylum NematodaPhylum Nematoda• 12,000 species
– 500,000 possible• Cylindrical body• Mostly dioecious• Only longitudinal
muscles– Undulate/thrash
around (don’t crawl) movie
Phylum NematodaPhylum Nematoda• Noncellular cuticle with several layers
– Maintains internal hydrostatic pressure– Provides mechanical protection– Resists digestion by host (in parasitic
nematodes)
Phylum Nematoda Phylum Nematoda (cont’d)(cont’d)
• Found everywhere– Oceans– Polar ice– Hot springs– soil
5 billion per acre
Phylum Nematoda Phylum Nematoda (cont’d)(cont’d)
• Eat just about every type of organic material– Rotting
substance– Living tissue
• Parasites of nearly all plant and animal species!
Ascaris lumbricoidesAscaris lumbricoides• Human parasite
– Up to 30cm long• 1.2 billion people
– Many in southeast US• Females lay 200,000
eggs a day• Unsanitary habits
contaminate ground– Ingest eggs– Hatch bury into
veins lungs pharynx
– Swallowed intestine
PinwormsPinworms
• Most common parasite in US
• 30% children; 16% adults• Large intestine• Lay eggs in anus at night• Spread
– Fecal oral route
Filarial WormsFilarial Worms• “Elephantiatis”• 250 million people
(tropics)• Lives in lymphatic system• Obstruct lymph to cause
swelling
Microfilaria of Wuchereria bancrofti
Other parasitic Other parasitic nematodesnematodes
• Hookworms• Dog heartworms• Trichinella
(causes trichinosis)
• biomedical research– C. elegans
C. elegansC. elegans
• Free living nematode
• 959 cells– Development of
every cell is known (movie)
• Genome sequenced– NCBI
http://www.nobel.se/medicine/laureates/2002/press.html
Sydney Brenner- C. elegans since 1963
• C. elegans • Nobel Prize (2002)
Brenner, Sulston and Horvitz– “Genetic regulation of
organ development and programmed cell death”
Phylum RotiferaPhylum Rotifera
Phylum RotiferaPhylum Rotifera
http://www.microscopyu.com/galleries/dxm1200/images/collothecalarge.jpg
– rota= wheel– fera= bearer
• Ciliated crown (corona)– (movie)
Phylum RotiferaPhylum Rotifera
http://micro.magnet.fsu.edu/primer/techniques/phasegallery/images/rotifer.jpg
• Mostly microscopic• 1800 species• Many resistant to
desiccation• dioecious
Phylum RotiferaPhylum Rotifera
Internal Anatomy of a Typical Rotifer
• Aquatic (mostly freshwater)– Protonephridia with flame
cells