bis2c: lecture 28: lophotrochozoans
TRANSCRIPT
Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Lecture 28:
Triploblasts-Protostomes I: Lophotrochozoans
BIS 002C Biodiversity & the Tree of Life
Spring 2016
Prof. Jonathan Eisen
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Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Where we are going and where we have been…
•Previous lecture: •27: Diploblasts
•Current Lecture: •28: Triploblasts: Protostomes:
Lophotrochozonas
•Next Lecture: •29: Triploblasts: Protostomes:
Ecdysozoans
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Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Animal Diversity Topics
• Major Groups
• Diversity within Groups
• Key Features of Groups !Body Plans, Forms and Symmetry !Reproduction and Life Cycles !Mobility !Feeding
• Examples
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Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Lophotrochozoans
• Key Features of Lophotrochozoans
• Major Groups
• Diversity within Groups
• Examples
!Molluscs
!Annelids
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Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Animal Diversity
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Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Animal Diversity
Diploblasts
Triploblasts
Monoblasts
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Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Animal Diversity
Monoblasts
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Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Animal Diversity
Diploblasts
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Clicker
!9Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Clicker
Placozoans are really simple. Why don’t we place them at the base of the animal tree? Why do we believe the molecular phylogeny?
A. Molecular phylogeny is more prone to homoplasy
B. Appearances can be deceiving.
C. Organismal complexity always increases over evolutionary time
D. Sequences cannot undergo convergent evolution
!10Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Clicker
Placozoans are really simple. Why don’t we place them at the base of the animal tree? Why do we believe the molecular phylogeny?
A. Molecular phylogeny is more prone to homoplasy
B. Appearances can be deceiving.
C. Organismal complexity always increases over evolutionary time
D. Sequences cannot undergo convergent evolution
!11Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Animal Diversity
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Triploblasts
Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Animal Diversity
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Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016 14
Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Lophotrochozoa
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Lophotrochozoa
Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Lophotrochozoa
A lophophore circular or U-shaped ring of hollow, ciliated tentacles around the mouth. It
Lophophorates
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Lophotrochozoa
Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Lophotrochozoa
A trochophore is a specialized, free-swimming larval stage. Moves and pulls in food by beating a band of cilia.
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Lophotrochozoa
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Lophotrochozoa
Zoa = Animal
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Lophotrochozoa
A Few Summaries for Your Enjoyment …
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Figure 32.6 Flatworms Include Both Parasites and Free-Living
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Figure 32.7 Rotifers and Gastrotrichs
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Figure 32.7 Rotifers and Gastrotrichs (Part 2)
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Figure 32.8 Ribbon Worms
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Figure 32.9 A Brachiopod’s Lophophore
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Figure 32.10 Phoronids
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!27Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Lophotrochozoa
Not JUST for your enjoyment …
!28Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Mollusks
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• Most diverse group of Lophotrochozoans •~90,000 species, both aquatic and terrestrial.
Mollusks: Main Features
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• Bilaterally symmetrical (secondary asymmetry), coelomate protostomes • Reduced coelom • Open or closed circulatory system • Body plan: mantle, foot, and visceral mass • Mouth with a radula (lost in some groups)
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Mantle
!32Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
• Fold of tissue along the dorsal surface that covers the visceral mass and encloses the mantle cavity. • Secretes the shell (when present).
Foot
!33Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
• Large, ventral muscle mass. • Used for locomotion, burrowing, and feeding. • Modified as a siphon (bivalves) or tentacles (cephalopods).
Visceral Mass
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•Central mass that encloses digestive, circulatory, excretory, and reproductive organs.
Radula
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• Rasping organ used for feeding.
A Few Summaries for Your Enjoyment …
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Chitons
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Chitons: 1,000 species.
Eight overlapping calcareous plates, surrounded by a girdle, protect the organs and muscular foot.
Most are marine omnivores that scrape rocks with a radula.
They cling tightly to rock surfaces with the large, muscular foot.
Gastropods
!38Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Gastropods: snails, slugs, nudibranchs, limpets, abalones; 85,000 species.
Most move by gliding on the foot, but in a few species it is a swimming organ.
Nudibranchs and slugs have lost their shells. Many are toxic and have brilliant colors for warning (aposematic coloration). Others have camouflaged coloration.
Land snails and slugs are the only mollusks that live in terrestrial habitats.
The mantle tissue is modified into a highly vascularized lung.
Bivalves
!39Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Bivalves: clams, oysters, scallops, mussels; 30,000 species.
Have hinged, two-part shells. Many use the foot to burrow into mud or sand.
Feed by bringing water in the incurrent siphon and filtering food particles with large gills; water exits through the excurrent siphon.
Not JUST for your enjoyment …
!40Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Mollusk Example: Cephalopods
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• Cephalopods: squids, octopuses, nautiluses; 800 species.
• Excurrent siphon modified to eject water pulses allowing “jet propulsion.”
• Head with complex sensory organs. Eyes are comparable to those of vertebrates.
• Head has arms and/or tentacles (modified from food) used for predation and movement.
• Most retain a small internal shell for internal support.
• Octopuses completely lost shells
• Many intelligent w/ complex communications
Cephalopods: Vision
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• Single lens eye, very similar to vertebrates
Cephalopods: Outward Appearance Modification I
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Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Cephalopods: Outward Appearance Modification II
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Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Annelids
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• ~ 19,000 species, marine and terrestrial
• The coelom in each segment is isolated from the coelom in other segments.
• A separate nerve ganglion controls each segment.
• Most have a thin, permeable body wall that serves for gas exchange; restricted to aquatic or moist habitats.
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Annelid Example: Pogonophorans (Bearded Worms)
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Hydrothermal Vent
50Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016 (Image from Dive and Discover, WHOI)
Deep Ocean Seawater
Seafloor
Scientists Expected Little Life There
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• No light
• Very high pressure
• Low temperatures
• Very little food
• New seafloor
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http://nationalgeographic.org/media/deep-sea-hydrothermal-vents/
Teeming Ecosystem
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Clicker
Tubeworm symbionts fix carbon dioxide using energy and electrons from hydrogen sulfide (H2S).
This makes them
A. Chemolithoheterotrophs
B. Chemoorganoheterotrophs
C. Chemoorganoautotrophs
D. Chemolithoautotrophs
E. None of the above
!54Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Clicker
Tubeworm symbionts fix carbon dioxide using energy and electrons from hydrogen sulfide (H2S).
This makes them
A. Chemolithoheterotrophs
B. Chemoorganoheterotrophs
C. Chemoorganoautotrophs
D. Chemolithoautotrophs
E. None of the above
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Component Different FormsEnergy source Light
Photo
Chemical
Chemo
Electron source (reducing equivalent)
Inorganic
Litho
Organic
Organo
Carbon source Carbon from C1 compounds
Auto
Carbon from organics
Hetero
Forms of nutrition (trophy)
Three main components to “trophy”
Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Tubeworm Anatomy
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No Mouth
No Digestive Tract
No Anus
Basic Tubeworm Anatomy
But how can they eat with no mouth, gut, or
anus?
Colleen Canavaugh
!58Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Filled with Bacteria
59Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
Basic Tubeworm Anatomy Dr. Colleen Cavanaugh used microscopy techniques in 1981 and discovered billions of bacterial cells packed inside the tubeworm’s trophosome.
1011 bacteria per gram of trophosome!!
Plume
Trophosome
Pogonorphorans
Pogonophorans live in tubes of chitin. Digestive tract has been lost. They take up dissolved organic matter from
the substrate and have endosymbiotic bacteria in a specialized organ called the trophosome.
Hemoglobin in the tentacles imparts red color.
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Pogonophoran's
Pogonophorans were discovered in the twentieth century in the deep oceans.
Largest are up to 2 meters long and live near deep hydrothermal vents.
The endosymbiotic bacteria fix carbon using energy from the oxidation of H2S.
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Whale Fall Worms
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• Chemoautotrophs related to beard worms with similar features (no gut). • Live on ‘whale falls’ the decaying remains of whales. • Bacteria are able to metabolize bone and lipids.
!63Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016
http://video.nationalgeographic.com/video/hydrothermal-vents
Figure 32.11 Annelids Have Many Body Segments (Part 1)
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Figure 32.11 Annelids Have Many Body Segments (Part 2)
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