BIS2C: Lecture 31: Deuterosomes I: Echinoderms & Hemichordates

Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016

Lecture 31:

Deuterosomes I: Echinoderms & Hemichordates

BIS 002C Biodiversity & the Tree of Life

Spring 2016

Prof. Jonathan Eisen1


• SLIDES AVAILABLE AT http://tinyurl.com/BIS2CL31

2

http://tinyurl.com/BIS2CL31


Where we are going and where we have been…

3

•Previous lecture: •30: Triploblasts: Protostomes:

Ecdysozoans II I

•Current Lecture: •31: Deuterosomes I: Echinoderms &

Hemichordates

•Next Lecture: •31: Deuterosomes II: Chordates


Topics ..

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• Deuterostome innovations and uses of these innovations

• Major Groups of Deuterostome

• Focus on Echinoderms

• Innovations

• Symmetry

• Tube feet

• Chordate Introduction


Animals - AKA Metazoans

5

Metazoans

Clicker

What evidence supports the assertion that the common ancestor of metazoans at least colonial, if not multicellular?

A. Comparisons of modern metazoans

B. Comparisons of metazoans to choanoflagellates

C. Neither A nor B

D. Both A and B

!6Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016

Clicker

What evidence supports the assertion that the common ancestor of metazoans at least colonial, if not multicellular?

A. Comparisons of modern metazoans

B. Comparisons of metazoans to choanoflagellates

C. Neither A nor B

D. Both A and B


Clicker

What is the best evidence that sponges are the deepest branching group within the metazoa?

A. They are the most primitive animals

B. They have cells similar to those seen in choanoflagellates

C. All other animals are more complex

D. Sponges are not bilaterally symmetric

E. Branching patterns in molecular phylogenies


Clicker

What is the best evidence that sponges are the deepest branching group within the metazoa?

A. They are the most primitive animals

B. They have cells similar to those seen in choanoflagellates

C. All other animals are more complex

D. Sponges are not bilaterally symmetric

E. Branching patterns in molecular phylogenies


Figure 31.1 A Phylogenetic Tree of the Animals


Notochord

Hemichordates

DEUTEROSTOMES (Chapter 33)

Chordates

EchinodermsRadial symmetry

Placozoans

Cnidarians

Arrow worms

Lophotrochozoans

Calcareous sponges

Demosponges

Glass sponges

Ecdysozoans

PROTOSTOMES (Chapter 32)

Centopheres

Sponges (Chapter 33)

Diploblasticanimals(Chapter 31)

Bilaterains(triploblastic)

Eum

etazoans



Notochord

Hemichordates


Chordates


Placozoans

Cnidarians

Arrow worms

Lophotrochozoans

Calcareous sponges

Demosponges

Glass sponges

Ecdysozoans


Centopheres




Eum

etazoans

Common ancestor



Notochord

Hemichordates


Chordates


Placozoans

Cnidarians

Arrow worms

Lophotrochozoans

Calcareous sponges

Demosponges

Glass sponges

Ecdysozoans


Centopheres




Eum

etazoans

Common ancestor

•Colonial •Cell adhesion systems



Notochord

Hemichordates


Chordates


Placozoans

Cnidarians

Arrow worms

Lophotrochozoans

Calcareous sponges

Demosponges

Glass sponges

Ecdysozoans


Centopheres




Eum

etazoans

Common ancestor




Notochord

Hemichordates


Chordates


Placozoans

Cnidarians

Arrow worms

Lophotrochozoans

Calcareous sponges

Demosponges

Glass sponges

Ecdysozoans


Centopheres




Eum

etazoans

Unique cell junctions; collagen and proteoglycans in extracellular matrix

Common ancestor




Notochord

Hemichordates


Chordates


Placozoans

Cnidarians

Arrow worms

Lophotrochozoans

Calcareous sponges

Demosponges

Glass sponges

Ecdysozoans


Centopheres




Eum

etazoans


Multicellularity, Blastula

Common ancestor




Notochord

Hemichordates


Chordates


Placozoans

Cnidarians

Arrow worms

Lophotrochozoans

Calcareous sponges

Demosponges

Glass sponges

Ecdysozoans


Centopheres




Eum

etazoans



Common ancestor


Monoblasts (Sponges)



Silicaceous spicules

Choanocytes; spicules

Notochord

Hemichordates


Chordates


Placozoans

Cnidarians

Arrow worms

Lophotrochozoans

Calcareous sponges

Demosponges

Glass sponges

Ecdysozoans


Centopheres




Eum

etazoans



Common ancestor







Notochord

Hemichordates


Chordates


Placozoans

Cnidarians

Arrow worms

Lophotrochozoans

Calcareous sponges

Demosponges

Glass sponges

Ecdysozoans


Centopheres




Eum

etazoans



Common ancestor



Eumetazoans





Notochord

Hemichordates


Chordates


Placozoans

Cnidarians

Arrow worms

Lophotrochozoans

Calcareous sponges

Demosponges

Glass sponges

Ecdysozoans


Centopheres




Eum

etazoans


Two embryonic cell layers; nervous system


Common ancestor



Eumetazoans





Notochord

Hemichordates


Chordates


Placozoans

Cnidarians

Arrow worms

Lophotrochozoans

Calcareous sponges

Demosponges

Glass sponges

Ecdysozoans


Centopheres




Eum

etazoans




Common ancestor







Notochord

Hemichordates


Chordates


Placozoans

Cnidarians

Arrow worms

Lophotrochozoans

Calcareous sponges

Demosponges

Glass sponges

Ecdysozoans


Centopheres




Eum

etazoans




Common ancestor



Diploblasts





Notochord

Hemichordates


Chordates


Placozoans

Cnidarians

Arrow worms

Lophotrochozoans

Calcareous sponges

Demosponges

Glass sponges

Ecdysozoans


Centopheres




Eum

etazoans




Common ancestor



Diploblasts

Triploblasts (Bilaterians)





Simplification; loss of nervous system

Notochord

Hemichordates


Chordates


Placozoans

Cnidarians

Arrow worms

Lophotrochozoans

Calcareous sponges

Demosponges

Glass sponges

Ecdysozoans


Centopheres




Eum

etazoans




Common ancestor



Diploblasts







Notochord

Bilateral symmetry along an anterior-posterior axis; three embryonic cell layers

Hemichordates


Chordates


Placozoans

Cnidarians

Arrow worms

Lophotrochozoans

Calcareous sponges

Demosponges

Glass sponges

Ecdysozoans


Centopheres




Eum

etazoans




Common ancestor



Diploblasts







Notochord


Hemichordates


Chordates


Placozoans

Cnidarians

Arrow worms

Lophotrochozoans

Calcareous sponges

Demosponges

Glass sponges

Ecdysozoans


Blastopore develops into mouth

Centopheres




Eum

etazoans




Common ancestor



Diploblasts







Notochord


Hemichordates


Chordates


Placozoans

Cnidarians

Arrow worms

Lophotrochozoans

Calcareous sponges

Demosponges

Glass sponges

Ecdysozoans


Exoskeleton molting Blastopore develops into mouth

Centopheres




Eum

etazoans




Common ancestor



Diploblasts







Notochord


Blastopore develops into anus

Hemichordates


Chordates


Placozoans

Cnidarians

Arrow worms

Lophotrochozoans

Calcareous sponges

Demosponges

Glass sponges

Ecdysozoans


Exoskeleton molting Blastopore develops into mouth

Centopheres




Eum

etazoans




Common ancestor



Diploblasts



Animal Diversity

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Protostomes

12

Protostomes


Protostomes

13

Deuterostomes


Deuterostomes

14

Figure 33.1 Phylogeny of the Deuterostomes


General/Common Features of Deuterostomes Common Ancestor


General/Common Features of Deuterostomes Common Ancestor


• Development !Radial cleavage !Blastopore becomes the anus

and mouth forms on opposite side

!Coelom develops from mesodermal pockets that bud off from the gastrula cavity

!Triploblastic, coelomate animals with internal skeletons

!Complete gut.

• There are far fewer species of deuterostomes than protostomes.

Three Main Clades


Echinoderms

Hemichordates

Chordates


Ambulacrarians

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Chordates

Common ancestor (bilaterally symmetrical, pharyngeal slits present)

Echinoderms

Hemichordates

Lancelets

Tunicates

VertebratesVertebral column, anterior skull, large brain, ventral heart

Notochord, dorsal hollow nerve cord, post-anal tail

Am

bulacrarians

• Two main groups: echinoderms and hemichordates

• Have ciliated, bilaterally symmetrical larvae

• Adult hemichordates are also bilaterally symmetrical.


Ambulacrarians

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Chordates


Echinoderms

Hemichordates

Lancelets

Tunicates



Ciliated larvae

Am

bulacrarians





Ambulacrarians

19

Chordates


Echinoderms

Hemichordates

Lancelets

Tunicates



Radial symmetry as adults, calcified internal plates, loss of pharyngeal slits

Ciliated larvae

Am

bulacrarians





Ambulacrarians - Others - Xenoturbellids

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Xenoturbellids

Xenoturbellids (two species): wormlike organisms that feed on or parasitize mollusks in the north Atlantic.

Xenoturbella in the news



• VIDEOS

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Ambulacrarians

26

Xenoturbellids


Ambulacrarians

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Xenoturbellids

Acoels

Acoels: also wormlike, live as plankton, between grains of sediment, or on other organisms such as corals.


Ambulacrarians

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Xenoturbellids

Acoels

s Not clear exactly where acoels branch in the tree

Figure 33.4 Highly Reduced Acoels Are Probably Relatives of the Ambulacrarians



• See http://www.nature.com/news/2011/110209/full/470161a.html for discussion of acoels

• http://www.latimes.com/science/sciencenow/la-sci-sn-churro-sea-worm-bilateria-20160205-story.html

• http://www.nature.com/nature/journal/v530/n7588/abs/nature16545.html

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http://www.nature.com/news/2011/110209/full/470161a.html

http://www.latimes.com/science/sciencenow/la-sci-sn-churro-sea-worm-bilateria-20160205-story.html

http://www.nature.com/nature/journal/v530/n7588/abs/nature16545.html

Clicker

Which of the following topics would studies of Xenoturbellid evolution be most useful for?

A. Origin of diploblasty

B. Origin of radial symmetry

C. Origin of bilateral symmetry

D. Origin of segmentation

E. Origin of blastulas


Clicker

Which of the following topics would studies of Xenoturbellid evolution be most useful for?

A. Origin of diploblasty

B. Origin of radial symmetry

C. Origin of bilateral symmetry

D. Origin of segmentation

E. Origin of blastulas



Protostomes

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Xenoturbellids


Ambulacrarians

34

Xenoturbellids

Acoels

sFocus on Two Main Lineages of Ambulocrarians


Hemichordates

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Xenoturbellids

Acoels

s Focus on Hemichordates

Hemichordates

Hemichordates Body Plan


Saccoglossus kowalevskii

ProboscisCollarTrunk




Proboscis

Proboscis used for feeding and locomotion and sometimes protection



Collar

Collar contains a stomochord similar to the notochord of chordates




Trunk

Trunk contains pharynx and pharyngeal gill slits



For Your Personal Enjoyment

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Group 1: Acorn worms

• Up to 2 m long, burrow in soft marine sediments

• Digestive tract is a mouth, pharynx, and intestine

• The pharynx opens to the outside via pharyngeal slits.

• Vascularized tissue around the slits is a gas exchange surface.

• Prey is captured with the large proboscis, which is covered in sticky mucus.

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Acorn Worms

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Slides by Jonathan Eisen for BIS2C at UC Davis Spring 2016 43

Group 2: Pterobranchs

• Sedentary marine animals that live in tubes secreted by the proboscis.

• Some are solitary, others form colonies.

• The collar has one to nine pairs of arms with tentacles for prey capture and gas exchange.



Ambulacrarians

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Chordates


Echinoderms

Hemichordates

Lancelets

Tunicates




Ciliated larvae

Am

bulacrarians

Focus on Echinoderms


Ambulacrarians

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Chordates


Echinoderms

Hemichordates

Lancelets

Tunicates




Ciliated larvae

Am

bulacrarians

Focus on Echinoderms

Echinoderms

Diversity


~7,500 species

Symmetry


Larvae are

bilateral


Echinoderm Symmetry

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Body Plan


Aboral (top)

Oral (bottom)

No head or brain

Water Vascular System


Water enters through pores known as madreporites

Circulates through canals that lead to tube feet

Hydraulic system used for locomotion, feeding, waste transport, respiration


Echinoderm Video

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Endoskeleton

• Endoskeleton derived from mesoderm • The endoskeleton is covered in epidermis • The skeletal plates are connected by collagen which can be

stiff or flexible which controls body tone without muscle



Echinoderm Endoskeleton

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For your personal enjoyment


Crinoidea- Sea Lily’s and Feather Stars


• 600 described extant species, many more in the fossil record • Both shallow water and deep trenches • Oral surface in dorsal, aboral surface is ventral • Sea Lily’s are attached to the surface by a stalk

Fossil Sea Lily’s, 330 mya

Feather Star

Asteroidea- Sea stars


• 1500 described species, both shallow and deep habitats • Mostly predaceous with an evertable stomach • Remarkable capacity for regeneration

Pycnopodia- sunflower star

Asteroidea- Evertable stomach


• When feeding, sea stars can extend their stomach pushing it through very small openings • The water vascular system is used to slowly pull muscles apart along with specialized ‘catch collagen’

Asteroidea- Crown of Thorns


• Among the largest sea stars, spines have neurotoxins • Voracious predator of coral (Great Barrier Reef) • Introduced species that is difficult to control

Ophiuroidea- Brittle stars and basket stars


• 1,900 described species • Long, slender arms often with spines; fast moving • Secretive predators, some are bioluminescent

Brittle Star Basket Star Basket Star

Echinoidea- Sea Urchins and Sand Dollars


• 950 described species • Slow moving, grazers on algae (Aristrotle’s lantern) • Protected by spines (urchins) and a calcareous test

StrongylocentrotusAristotle’s lantern

Echinoidea- Sea Urchins and California Kelp


• Urchins feed on kelp (brown algae) • Kelp forests in California harbor a great diversity of species • If unchecked, urchins can create ‘urchin barrens’ • Sea otters prey on urchins (using tools) keeping populations in check; they are a keystone species

Kelp forest, Monterey Bay

Holothuroidea- Sea Cucumbers


• 1,200 described species, scavengers and filter feeders • Soft-bodied, secondary bilateral symmetry* • Catch collagen allows them squeeze into tight places • Unique defense (evisceration), some are toxic


Chordates

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Chordates


Echinoderms

Hemichordates

Lancelets

Tunicates




Ciliated larvae

Am

bulacrarians

Focus on Chordates


Deuterostomes

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Deuterostomes

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Chordate Derived Traits Most Apparent in Juveniles


Notochord


• Notochord is a dorsal supporting rod. • Core of large cells with fluid-filled vacuoles, making it rigid but

flexible. • In tunicates it is lost during metamorphosis to the adult stage. • In vertebrates it is replaced by skeletal structures.

Dorsal hollow nerve cord


• Formed by an embryonic folding of the ectoderm • Develops to form the central nervous system in vertebrates

Post Anal Tail


• Extension of the body past the anal opening • In some species (e.g., humans) most visible in embryos • The combination of postanal tail, notochord, and muscles

provides propulsion

Pharyngeal Slits


• The pharynx is a muscular organ that brings water in through the mouth (via cilia) which then passes through a series of openings to the outside (slits).

• Ancestral pharyngeal slits present at some developmental stage; often lost or modified in adults.

• Supported by pharyngeal arches.


Clicker

71

Why are pharyngeal slits NOT considered a synapomorphy of chordates?

A. They occur in other deuterostomes B. They are lost in some chordates C. They are modified into gills in vertebrates D. They only occur in the embryo of some chordates


Clicker

72

Why are pharyngeal slits NOT considered a synapomorphy of chordates?

A. They occur in other deuterostomes B. They are lost in some chordates C. They are modified into gills in vertebrates D. They only occur in the embryo of some chordates

Figure 33.1 Phylogeny of the Deuterostomes



Chordates

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Chordates


Echinoderms

Hemichordates

Lancelets

Tunicates




Ciliated larvae

Am

bulacrarians

Focus on Chordates


Chordates

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Chordates


Echinoderms

Hemichordates

Lancelets

Tunicates




Ciliated larvae

Am

bulacrarians

Three Major Groups *Lancelets *Tunicates *Vertebrates


Lancelets (aka Cephalochordates)

76

Chordates


Echinoderms

Hemichordates

Lancelets

Tunicates




Ciliated larvae

Am

bulacrarians

Focus on Lancelets


Branchiostoma lanceolatum

Gut

TailAnusDorsal hollow nerve cord

NotochordPharyngeal slits

Lancelet Has Key Chordate Features


Branchiostoma lanceolatum

TailAnusDorsal hollow nerve cord

NotochordPharyngeal slits

Lancelet Features

• Lancelets (aka amphioxus) are very small, less than 5 cm.

• Notochord is retained throughout life.

• Burrow in sand with head protruding; also swim.

• Pharynx is enlarged to form a pharyngeal basket for filtering prey from the water.

• Fertilization takes place in the water.

• Segmented body muscles


Lancelet development

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Tunicates

80

Chordates


Echinoderms

Hemichordates

Lancelets

Tunicates




Ciliated larvae

Am

bulacrarians

Focus on Tunicates


Adult Tunicates

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• Tunicates (sea squirts or ascidians, thaliaceans, and larvaceans):

• Sea squirts form colonies by budding from a single founder. Colonies may be meters across.

• Adult body is baglike and enclosed in a “tunic” of proteins and complex polysaccharides secreted by the epidermis.


Adult Tunicates

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• Solitary tunicates seem to lack all of the synapomorphies of chordates?

• No dorsal hollow nerve cord, no notochord, no postanal tail


Adult Tunicates

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• Solitary tunicates seem to lack all of the synapomorphies of chordates?

• No dorsal hollow nerve cord, no notochord, no postanal tail

HOW ARE THESE CHORDATES?


Juvenile Tunicates

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Ascidian tunicate larva

• Sea squirt larvae have pharyngeal slits, a hollow nerve cord, and notochord in the tail region.

• The swimming, tadpolelike larvae suggest a relationship between tunicates and vertebrates.

• Larvacean tunicates do not undergo the metamorphosis and retain all of the chordate features.

Larvacean tunicates


Vertebrates

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Science

BIS2C: Lecture 31: Deuterosomes I: Echinoderms & Hemichordates