bis2c: lecture 28: lophotrochozoans

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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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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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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Lophotrochozoans

• Key Features of Lophotrochozoans

• Major Groups

• Diversity within Groups

• Examples

!Molluscs

!Annelids

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Animal Diversity

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Animal Diversity

Diploblasts

Triploblasts

Monoblasts

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Animal Diversity

Monoblasts

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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



Animal Diversity

12

Triploblasts


Animal Diversity

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Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016 14


Lophotrochozoa

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Lophotrochozoa


Lophotrochozoa

A lophophore circular or U-shaped ring of hollow, ciliated tentacles around the mouth. It

Lophophorates

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Lophotrochozoa


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


Lophotrochozoa

Zoa = Animal


Lophotrochozoa

A Few Summaries for Your Enjoyment …


Figure 32.6 Flatworms Include Both Parasites and Free-Living


Figure 32.7 Rotifers and Gastrotrichs


Figure 32.7 Rotifers and Gastrotrichs (Part 2)


Figure 32.8 Ribbon Worms


Figure 32.9 A Brachiopod’s Lophophore


Figure 32.10 Phoronids



Lophotrochozoa

Not JUST for your enjoyment …


Mollusks


• Most diverse group of Lophotrochozoans •~90,000 species, both aquatic and terrestrial.

Mollusks: Main Features


• 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)

Mantle


• Fold of tissue along the dorsal surface that covers the visceral mass and encloses the mantle cavity. • Secretes the shell (when present).

Foot


• Large, ventral muscle mass. • Used for locomotion, burrowing, and feeding. • Modified as a siphon (bivalves) or tentacles (cephalopods).

Visceral Mass


•Central mass that encloses digestive, circulatory, excretory, and reproductive organs.

Radula


• Rasping organ used for feeding.

A Few Summaries for Your Enjoyment …


Chitons


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


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


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 …


Mollusk Example: Cephalopods


• 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


• Single lens eye, very similar to vertebrates

Cephalopods: Outward Appearance Modification I


Cephalopods: Outward Appearance Modification II


Annelids


• ~ 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)


Hydrothermal Vent

50Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016 (Image from Dive and Discover, WHOI)

Deep Ocean Seawater

Seafloor

http://www.divediscover.whoi.edu/vents/basics.html

Scientists Expected Little Life There

51Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016

• No light

• Very high pressure

• Low temperatures

• Very little food

• New seafloor


http://nationalgeographic.org/media/deep-sea-hydrothermal-vents/

http://nationalgeographic.org/media/deep-sea-hydrothermal-vents/

Teeming Ecosystem


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


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”


Tubeworm Anatomy


No Mouth

No Digestive Tract

No Anus

Basic Tubeworm Anatomy

But how can they eat with no mouth, gut, or

anus?

Colleen Canavaugh


Filled with Bacteria


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.


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.


Whale Fall Worms


• 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.


http://video.nationalgeographic.com/video/hydrothermal-vents

Figure 32.11 Annelids Have Many Body Segments (Part 1)


Figure 32.11 Annelids Have Many Body Segments (Part 2)


bis2c: lecture 28: lophotrochozoans

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