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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
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.
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).
Extant FW Invertebrate Probability
Signature
Probability
(Kaster, various data)
0.6
0.5
0.4
0.3
0.2
0.1
0
Known FW
Probability
Br Ec Bz Po Pe An Ga Cr
Taxon
Extant FW Invertebrate Probability
Signature
Probability
(Kaster, various data)
0.6
0.5
0.4
0.3
0.2
0.1
0
y = 5E-05x4.4233
2
R = 0.9302
Br Ec Bz Po Pe An Ga Cr
Taxon
Extant FW Invertebrate Probability
Signature
Probability
(Kaster, various data)
0.6
0.5
0.4
0.3
0.2
0.1
0
4.4233
y = 5E-05x
2
R = 0.9302
Extant
Predicted
Pow er Function
Br Ec Bz Po Pe An Ga Cr
Taxon
Cenozoic FW Invertebrate Probability
Signature
(Raup, 1900 -1970 data)
0.6
Probability
0.5
0.4
y = 0.0004e0.9056x
R2 = 0.7886
0.3
0.2
0.1
0
Br Ec Bz Po Pe An Ga Cr
Taxon
Mesozoic FW Invertebrate
Probability Signature
(Raup, 1900-1970 data)
0.6
Probability
0.5
0.4
0.3
y = 0.0008e0.7131x
R2 = 0.6345
0.2
0.1
0
Br Ec Bz Po Pe An Ga Cr
Taxon
Paleozoic FW Invertebrate
Probability Signature
Probability
(Raup, 1900-1970 data)
0.6
0.5
0.4
0.3
0.2
0.1
0
y = 0.0028e0.5252x
R2 = 0.8103
Br Ec Bz Po Pe An Ga Cr
Taxon
Precambrain FW Invertebrate
Probability Signature
Probability
(Raup, 1900-1970 data)
0.6
0.5
0.4
0.3
0.2
0.1
0
y = 8E-05e0.927x
R2 = 0.7311
Br Ec Bz Po Pe An Ga Cr
Taxon
Ordovician
22%
Devonian
21%
Permian
95%
Triassic
20%
Paleozoic
Fauna
600 - 230
TIME
Mesozoic
Fauna
230 - 63
Cretaceous
75%
2.6
2.5
2.4
2.3
2.2
2.1
ta
nt
Ex
oi
c
Ce
no
z
es
oz
oi
c
M
Pa
le
oz
oi
c
br
ia
n
2
Pr
ec
am
Shannon Diversity
2.7
Are there too many species clustered in too few Phyla?
P
R
O
B
A
B
I
L
I
T
Y
Pm=0.81
Pm=0.72
Pm=0.61
Pm=0.53
Precambrian
Fauna
Pm=0.51
Paleozoic
Fauna
Mesozoic Cenozoic Extant
Fauna
Fauna Fauna
Idealized Probabilistic Signature of the Freshwater
Invertebrate Fauna
Permian Extinction FW Probability
Signature
(Raup, 1900-1970 data)
Probability
0.2
Pre-extinction
Post-extinction
0.1
0
Br Ec Bz Po Pe An Ga Cr
Taxon
K-T Extinction FW Probability
Signature
(Raup, 1900-1970 data)
0.2
Probability
Pre-extinction
Post-extinction
0.1
0
Br Ec Bz Po Pe An Ga Cr
Taxon
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).
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)
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.
B
R
O
O
D
I
N
G
F
A
U
N
A
85%
15%
Polar
Lake
Continent
Lake
15%
Equatorial
85%
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
85
%
Increased
Habitat
15%
K
Polar
Lake
Continent
Decreased
Habitat
Lake
Equatorial
15%
r
“Regression Period”
85%
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
85
%
Decreased
Habitat
15%
K
Polar
Lake
Continent
Increased
Habitat
Lake
Equatorial
15%
r
“Transgression Period”
85%
S
H
E
D
D
I
N
G
F
A
U
N
A
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”
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.
Ca2+ Mg2+
Na+ HCO3
CO32- SO42Cl-
K+
Earth leaches K+ : Na+ = 1
K+ is readily absorbed to soil particulates and thus
there is less K+than Na+ in sea water (K+ : Na+ = 0.021)
and freshwater (K+ : Na+ = 0.028)
K+ is preferentially incorporated into the crystaline lattice of minerals
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.
Immigration of K-strategist, marine brooding invertebrates to freshwater
largely followed a polar corridor.
A “K+ bottleneck” during early life history stages is suggested
as a critical factor that regulates freshwater colonization success.
The de novo evolution of muscle and nervous systems of the primal
metazoans (protozoan-metazoan megaleap) required high benthic K+.
Metazoan de novo “K+ scavenging” may have lead to herbivory
and “K+ predation” to predation.