Primal%20Origin%20of%20the%20Freshwater%20Invertebrates

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Primal Origin of the Freshwater Invertebrates
Jerry L. Kaster
What is the Geologic Time-Scale History of
Freshwater Invertebrates?
What are the Colonization Routes of the
Freshwater Invertebrates?
Habitat Corridors
Continental Corridors
Regression-Transgression
Route associated competitive strategies
What was the Role of K Scavenging in
Establishing a Brooding Fauna?
Bryant 1775
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What is the Geologic Time-Scale History of
Freshwater Invertebrates?
Assumptions
First, the contemporary marine and freshwater
faunas are more ecesis compatible than are faunas
not contemporary.
Second, marine taxa with a high survival rate
(implying gene pool breadth) on a geological time
scale are more likely to colonize new habitats,
both marine and freshwater, than taxa with a low
survival rate.
By example, the extinct trilobites would have a
zero probability for a modern colonization of
freshwaters whereas extant marine forms without
a contemporary freshwater counterpart, such as
branchiopods or echinoderms would score a
probability for a modern occurrence in
freshwaters. The fact that the latter two forms
do not now exist in freshwater does not rule out
the possibility that they may colonize in the
future.
Third, the predicted probability of occurrence
for a ancestral freshwater fauna is a
recapitulation of its descendant freshwater
fauna.
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PFPt ((MPt FPt) ? 2) ? MSP
PFPt ? 1 ((MPt ?1 PFPt) ? 2) ? MSP
PFPt ? 2 ((MPt ?2 PFPt? 1) ? 2) ? MSP
PFPt ? 3
Where PFPt Predicted freshwater
probability MPt Extant marine taxon
probability FPt Extant freshwater
taxon probability MPt-n Fossil marine
taxon probability (mainly Raup 1976)   t
Faunal geological period, where 1
Cenozoic 2 Mesozoic 3
Palaeozoic 4 Precambrian
MSP Marine taxon survival probability (Easton
1960) Crustacea (0.930), Gastropoda (0.821),
Annelida (0.973), Pelecypoda (0.423), Porifera
(0.560), Ectoprocta (0.504), Echindermata
(0.270), and Brachiopoda (0.015).
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Devonian 21
Ordovician 22
Mesozoic Fauna 230 - 63
Permian 95
Cretaceous 75
Triassic 20
Paleozoic Fauna 600 - 230
TIME
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Are there too many species clustered in too few
Phyla?
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Idealized Probabilistic Signature of the
Freshwater Invertebrate Fauna
Pm0.81
P R O B A B I L I T Y
Pm0.72
Pm0.61
Pm0.53
Pm0.51
Extant Fauna
Precambrian Fauna
Mesozoic Fauna
Cenozoic Fauna
Paleozoic Fauna
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Suppositions
A shift along the time series is characterized
by an overall rise in dominance of fewer taxa
with high probable occurrence.
Communities of greater horizontal
energy-material exchange have more rare
species and should be distinguished by greater
evolutionary innovation.
Catastrophic Permian community disruption reduced
rare taxa, with common taxa gained dominance
(reduced diversity). The K-T disruption increased
rare taxa relative to common taxa (increased
diversity).
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What were the Colonization Routes of the
Freshwater Invertebrates?
Immigration Routes   Habitat
Corridors   Sea ? Land ? Freshwater
(pulmonate snails, insects, mites)   Sea ?
Estuary ? Freshwater (zebra mussels)   Sea ?
Psammolittoral ? Phreatic ? Freshwater (protozoa
micrometazoans)   Sea ? Marsh ?
Freshwater (amphipods)
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Immigration Routes
Route associated competitive strategies
Continental Corridors
Equatorial Continental Von Martens,
1857   Shotgun approach   Typical
r-strategists. Large pool of tropical species
with pelagic larvae.   Polar Continental de
Guerne Richard, 1892   Finesse approach
  Typical K-strategists. Small pool of polar
species with brood representing a pre-adapted
life cycle to freshwater.
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S H E D D I N G F A U N A
B R O O D I N G F A U N A
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85
Polar
Lake
Continent
Lake
85
Equatorial
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S H E D D I N G F A U N A
B R O O D I N G F A U N A
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K
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Polar
Increased Habitat
Lake
Continent
Lake
Decreased Habitat
Equatorial
85
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r
Regression Period
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B R O O D I N G F A U N A
S H E D D I N G F A U N A
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85
K
Polar
Decreased Habitat
Lake
Continent
Lake
Increased Habitat
Equatorial
85
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r
Transgression Period
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Why do freshwater forms lack pelagic
larvae? Broad statements (e.g., Neeham 1930
Pennak 1953, 1963, 1985) of ion/osmoregulation
provided the framework for its general acceptance
of the marine to freshwater transition.
Abundant suggestions
Ionic - Osmotic gradiant imbalance
Energy expenditure to stay afloat
Poor pelagic nutrient resources
Others
Brooding K-strategist Fauna Keen competitors
fill the barrel Shedding r-strategist
fauna poorly colonize a full barrel

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What was the role of K scavenging in
establishing a brooding fauna?
Ionic K Bottleneck
Most cations and anions are regenerated
in the epilimnion, while K
shunts to the benthos.
K
Ca2 Mg2 Na HCO3 CO32- SO42- Cl-
Earth leaches K Na 1
K is readily absorbed to soil particulates and
thus there is less Kthan Na in sea water (K
Na 0.021) and freshwater (K Na 0.028)
K is preferentially incorporated into the
crystaline lattice of minerals
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Marine invertebrate K levels are similar to
sea water medium Sea water K 9.96 mM/l vs.
inverts 11.56 mM/l (ratio 0.86)
Freshwater invertebrate K levels are much
higher than the freshwater
medium Freshwater 0.03 mM/l vs. inverts
4.75 mM/l (ratio 0.0063)
Benthic sediment K 13.8 mM/l vs. 4.75mM/l
(ratio 2.9)
Bottleneck is at the late embryo (yolk K cache
depleted) or at the early larval stage (must
shift to high K particle feeding).
K is necessary for membrane function, especially
in excitatory tissue such as muscle and nervous
tissue.
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Suppositions

Immigration of K-strategist, marine brooding
invertebrates to freshwater largely followed a
polar corridor. The de novo evolution
of muscle and nervous systems of the primal
metazoans (protozoan-metazoan megaleap) required
high benthic K.
A K bottleneck during early life history
stages is suggested as a critical factor that
regulates freshwater colonization success.
Metazoan de novo K scavenging may have lead to
herbivory and K predation to predation.