Transcript vertebrates

VERTEBRATE ZOOLOGY
(VZ Lecture04 – Spring 2012 Althoff - reference PJH Chapter 3)
Early Vertebrates
PART I
PALEOZOIC (late Carboniferous Period)
lake
3 margin
1 open
water
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upland
2
shallow
lake
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early
amniote
Terrestrial
nonamniote
tetrapods
Fig. 7-5 p165 PJH
The most conspicuous new features of early
vertebrates vs. nonvertebrate chordates:
A ______________ end that….
A) contained a tripartite brain that was
B) enclosed by a cartilaginous cranium
C) containing sense organs
Newly acquired pharyngeal musculature
to draw water into the mouth and over
the gills _________________ …not for
filter feeding (i.e, acquiring food).
Early vertebrates
• Fossil deposits, ~540 MYA
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A) Myllokumingia (see next slide), China
B) Haikouichthys China, too—same deposits
Small, fish-shaped, ~ 3 cm long
_____________ present
_____________ present
BUT _____ evidence of bone or mineralized
scales
Dorsal fin and ribbonlike pairs of ventrolateral
fins
Myllokumingia
DORSAL FIN
MYOMERES
VENTROLATERAL FIN
Astrapis
Fig. 3-1 p44 PJH
Next….bone fragments in fossil
• Fossil deposits: Australia, Bolivia, North
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America
A) Astraspis (North America “version”)
Large, fish-shaped, ~ 12 - 35 cm long
Armored – close-fitting, polygonal bony plates
Eye “protection”
Torpedo-shaped
Jawless
Myllokumingia
BONY
PLATES/SCALES
Fig. 3-1 p44 PJH
EYE
PROTECTION
Astrapis
Conodonts – “microfossils”
• _____________ elements of true vertebrates
• < 1mm long
• Composed of apartite = __________________
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compound characteristic of vertebrate tissue
Much like _____________ (making it uniquely
vertebrate tissue)
Complete impressions of conodont animals with
the “conodont” elements arranged within the
pharynx thus confirming they were true
vertebrates
Clydagnathus
CONODONTS
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elements
(anterior)
Idiognathus
_________
Elements
(posterior)
Fig. 3-2 p45 PJH
Fig. 3-3 p46 PJH
Origin of Bone & Mineralized Tissue
• Origin of mineralized tissues still somewhat
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uncertain
Earliest known types are _______________
in structure than mineralized tissues of living
vertebrates
____________  basic units of mineralized
tissue…tooth-like elements formed “____” the
skin (in dermal layer…unlike mollusks), then
overlaid by epidermis
No cells in adult form….acellular
__________________ of Mineralized Tissue?
• Defensive structures against predator attacks
• Design of bony tissue resulted in more
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complex function that merely protection:
system of pores and small projections
suggest ____________________
Protective against predators & insulating
coating around ______________________
that increased detection of prey
or
Subsequent advantage: ______________ &
_______________ deposition and subsequent
mobilization
Which happened first?
• Vertebrates evolved first in freshwater or first in
marine ecosystems?
--some early thinking was that because of
vertebrate kidney clearly being an
advantage in freshwater, that most
early evolution took place there
--now, thinking is that _________ was
“fortuitously preadapted” for freshwater exist….that withstanding,
“early” evolution likely was in _______
ecosystems.
Evidence of marine origin
• Earliest vertebrate __________ found in
marine sediments (paleontological evidence)
• All nonvertebrate chordates and
deuterostome invertebrates (starfish, sea urchins,
etc.) are exclusive marine forms (comparative
physiological evidence) where ____________
in same concentrations as seawater
Extant (“still living”) Jawless Fishes
• Two representatives: _________ & __________
• No specialized reproductive ducts…eggs and
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sperm released into coelum
Primitive handling of drainage from kidneys (no
duct-work, more through pores)
External fertilization of eggs
Considered ________________ a subset of
“Agnathans” = jawless fishes preceeding
conodonts and ostracoderms—both of which
are extinct groups.
Fig. 3-4 p48 PJH
Hagfishes
• Family: Myxinoidea
• Two major genera: Eptatretus and Myxine
• ~ 40 species
• ~ 0.5 m in length, elongated
• ________ scales
• ________ vertebrae
• Simple kidneys
• Eyes degenerate, covered with thick skin
• Tooth-like plates
• Found nearly worldwide (except polar regions)
• Primarily deep-sea, cold-water inhabitants
Hagfishes
• _________________ ….slime glands produce
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gelatinous mess that is a deterrent to predators.
After threat gone, makes a knot to scrap off mass
of mucus, then sneezes sharply to blow nasal
passage clear.
______________  find food by sense of ______
Also, use the “tying the knot” routine to brace
themselves against their prey, mouth attaches to
part of prey to tear off the flesh with pinching
grasp….enough to expose soft coelomic cavity of
prey.
Digestion accomplished in a mucoid bag secreted
by gut…nutrients diffuse out, then absorbed
Fig. 3-5 p49 PJH
Lampreys
• Family: Petromyzontoidea
• Two major genera: Petromyzon and Lampetra
• ~ 40 species
• ______ scales, up to 1 m in length
• ___ vertebrae, but “vertebral structures” (arculalia)
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that are ________________ skeletal elements
Kidneys – much _____________ over hagfishes,
enables better regulation of ions, water, and
nitrogeneous waste…
Exist in ___________ of salinities
Found mostly in northern latitudes - temperate
Most are _________________  live in sea/lake,
breed in rivers or streams
Lampreys
• __________  on other fishes (usually bony
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fishes, but sometimes mammals = whales &
porpoises)
Attach to host by suction
Oral gland secretes anticoagulant that prevents
host’s blood from clotting
Thus, bulk of lamprey’s diet is ___________ of the
hosts
_______, straight digestive tract…_______ “food”,
_______ “digestion”
Like many parasites, they don’t end up killing the
host…only weaken them
LAMPREY
oral region
Tooth-like
organs
(origin: ectoderm)
Also see….
Fig. 4-5 p30 FS
Lampreys
• Females produce hundreds to thousands of eggs,
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spawn with males after constructing a nest.
Fertilized eggs get “surrounded” by larger rocks
that create an eddy, dropping sediment over the
eggs
Adults die after breeding once
Larvae hatch in about 2 weeks….known as
Ammocoets, they float downstream, burrow in
mud or sand and spend about the next ____ years
as ______________________.
Finally, metamorphosis into juvenile and become
parasitic
Lampreys: Conservation Concern
• May have been indigenous to Lake Ontario….but
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not in any other Great Lakes until _________
Devasting to sport and commercial fish
populations in the Great Lakes—especially Lake
Erie by the 1940s.
Huge efforts in past 50-60 years to curb their
numbers:
chemical lampricides
electrical barriers
mechanical weirs
Lake trout
Sea lamprey