early vertebrates part i vertebrate zoology (vz lecture04 – spring 2012 althoff - reference pjh...
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Early VertebratesPART I
VERTEBRATE ZOOLOGY (VZ Lecture04 – Spring 2012 Althoff - reference PJH Chapter 3)
PALEOZOIC (late Carboniferous Period)
Terrestrialnonamniotetetrapods
open water
shallow lake
lakemargin
upland
earlyamniote
12
3 4
5
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 musculatureto draw water into the mouth and
over the gills _________________ …not for filter feeding (i.e, acquiring food).
Early vertebrates
• Fossil deposits, ~540 MYAA) 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 ventrolateralfins
Fig. 3-1 p44 PJH
Myllokumingia
Astrapis
MYOMERES
DORSAL FIN
VENTROLATERAL FIN
Next….bone fragments in fossil
• Fossil deposits: Australia, Bolivia, North America A) Astraspis (North America “version”)
• Large, fish-shaped, ~ 12 - 35 cm long
• Armored – close-fitting, polygonal bony plates
• Eye “protection”
• Torpedo-shaped
• Jawless
Fig. 3-1 p44 PJH
Myllokumingia
Astrapis
BONY PLATES/SCALES
EYEPROTECTION
Conodonts – “microfossils”
• _____________ elements of true vertebrates
• < 1mm long
• Composed of apartite = __________________ 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
Fig. 3-2 p45 PJH
Clydagnathus
Idiognathus
CONODONTS
________ elements(anterior)
_________Elements(posterior)
Fig. 3-3 p46 PJH
Origin of Bone & Mineralized Tissue
• Origin of mineralized tissues still somewhat 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 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 ofvertebrate kidney clearly being anadvantage in freshwater, that mostearly evolution took place there
--now, thinking is that _________ was “fortuitously preadapted” for fresh-water 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 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 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)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 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
Also see….Fig. 4-5 p30 FS
LAMPREYoral region
Tooth-like organs
(origin: ectoderm)
Lampreys
• Females produce hundreds to thousands of eggs, 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 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 lampricideselectrical barriers
mechanical weirs
Lake trout
Sea lamprey