Modern* Skeleton-Breaking Predators Structure Temperate

and Tropical Benthic Communities

Modern* Skeleton-Breaking Predators Structure Temperate

and Tropical Benthic Communities

Teleostean Fish

Neoselachian Sharks and Rays

Decapod Crustaceans

Teleostean Fish

Neoselachian Sharks and Rays

Decapod Crustaceans

*Modern = Product of Post-Paleozoic Radiations of Shell-Breaking Functional Groups*Modern = Product of Post-Paleozoic Radiations of Shell-Breaking Functional Groups

Paleozoic EraPaleozoic Era

Mesozoic EraMesozoic Era

Modern predators begin to diversifyModern predators begin to diversify

Cenozoic EraCenozoic Era

Functionally Modern, Shell-Crushing Predators are Absent from the

Antarctic Shallow Benthos

Functionally Modern, Shell-Crushing Predators are Absent from the

Antarctic Shallow Benthos• No crabs or lobsters.

• No sharks or rays.

• The bony fish (notothenioids) eat amphipods and other soft foods.

• No crabs or lobsters.

• No sharks or rays.

• The bony fish (notothenioids) eat amphipods and other soft foods.

BASBAS

BASBAS

TemperateTemperateTropicalTropical

Polar: AntarcticPolar: Antarctic

After G. J. VermeijAfter G. J. Vermeij

Inferred Latitudinal Gradients:CalcificationPredation

Inferred Latitudinal Gradients:CalcificationPredation

www.gastropods.comwww.gastropods.com

90° S90° S

0°

180°

South America

NZ

Australia

Africa

Antarctic Circle66° 32' S

McMurdo Sound

Top Predators: Slow-Moving Invertebrates of a Paleozoic Functional GradeTop Predators: Slow-Moving Invertebrates of a Paleozoic Functional Grade

Top Predators: Slow-Moving Invertebrates of a Paleozoic Functional GradeTop Predators: Slow-Moving Invertebrates of a Paleozoic Functional Grade

Julian Gutt, AWIJulian Gutt, AWI

90°S90°S

0°

180°

South America

NZ

Australia

Africa

Antarctic Circle66° 32' S

Seymour Island

Seymour IslandSeymour IslandFossils from 55–33.5Fossils from 55–33.5

million years agomillion years ago

Seymour IslandSeymour IslandFossils from 55–33.5Fossils from 55–33.5

million years agomillion years ago

Eocene La Meseta Fm

Paleozoic EraPaleozoic Era

Eocene EpochEocene Epoch

Fossil BrittlestarsFossil Brittlestars

Fossil Sea LiliesFossil Sea Lilies

The 41-Ma Cooling EventThe 41-Ma Cooling Event

• Predation pressure reduced.

• Appearance of dense crinoid and ophiuroid populations.

• Appearance of undefended gastropods.

• Predation pressure reduced.

• Appearance of dense crinoid and ophiuroid populations.

• Appearance of undefended gastropods.

Morphometric Analysis (MDS) of Gastropod Shells:Architectural Defenses Against Predatory Crabs

Post-Cooling Genera(poorly defended)

Pre-Cooling Genera (well defended)

2D stress = 0.1533D stress = 0.900

Struthioptera

Conomitra

Polinices

Antarctodarwinella

Zelandiella

Calliostoma

Taioma

Why No Shell-Crushing Predators?Why No Shell-Crushing Predators?General Physiological Barriers

• Calcification is costly at cold temperatures.

• Power output of muscle at 0 °C is one-tenth that at 25 °C.

General Physiological Barriers

• Calcification is costly at cold temperatures.

• Power output of muscle at 0 °C is one-tenth that at 25 °C.

Teleosts• Atifreeze fish—notothenioids—are the only

teleosts living in Antarctica, and they are not shell-crushers.

• Teleosts living in the Arctic that ARE shell-crushers have independently evolved THE SAME AFGPs.

Teleosts• Atifreeze fish—notothenioids—are the only

teleosts living in Antarctica, and they are not shell-crushers.

• Teleosts living in the Arctic that ARE shell-crushers have independently evolved THE SAME AFGPs.

Why No Shell-Crushing Predators?Why No Shell-Crushing Predators?

Decapod CrustaceansProblem of Magnesium Regulation

• Crabs and lobsters cannot regulate Mg2+ ions in their blood at low temperatures. They pass out and die when sea temperatures dip to 0–1°C.

• King crabs and hermit crabs also have this problem. King crabs (Lithodidae) tolerate temperatures of 1–2°C by operating in a torpid, hypometabolic state.

• Isopods and amphipods don’t have this problem. They are all over the Antarctic benthos.

Decapod CrustaceansProblem of Magnesium Regulation

• Crabs and lobsters cannot regulate Mg2+ ions in their blood at low temperatures. They pass out and die when sea temperatures dip to 0–1°C.

• King crabs and hermit crabs also have this problem. King crabs (Lithodidae) tolerate temperatures of 1–2°C by operating in a torpid, hypometabolic state.

• Isopods and amphipods don’t have this problem. They are all over the Antarctic benthos.

Why No Shell-Crushing Predators?Why No Shell-Crushing Predators?

Paralomis birsteini (Lithodidae): Continental Slope, 1100 m Bellingshausen Sea off the Antarctic PeninsulaJanuary 2007

Paralomis birsteini (Lithodidae): Continental Slope, 1100 m Bellingshausen Sea off the Antarctic PeninsulaJanuary 2007

Water Temperature: 1–2 °C

Water Temperature: 1–2 °C

Global Warming in AntarcticaGlobal Warming in Antarctica• Summertime SSTs off the western

Antarctic Peninsula have increased ~1°C in the last 50 years.

• That is double the global average.• Shelf habitats along the Peninsula are

now at 0–1°C and will be warm enough for modern predators within the next 50–100 years.

• Summertime SSTs off the western Antarctic Peninsula have increased ~1°C in the last 50 years.

• That is double the global average.• Shelf habitats along the Peninsula are

now at 0–1°C and will be warm enough for modern predators within the next 50–100 years.

Avenues for Reinvasionof Antarctica

Avenues for Reinvasionof Antarctica

• Eddies from the ACC transport crab larvae, which will be more likely to survive as sea temperatures rise and the growing season expands.

• Increasing ship traffic has already introduced alien crabs from the Subarctic!!

• King crab populations on the continental slope will move into shallow-water shelf habitats as sea temperatures rise.

• Eddies from the ACC transport crab larvae, which will be more likely to survive as sea temperatures rise and the growing season expands.

• Increasing ship traffic has already introduced alien crabs from the Subarctic!!

• King crab populations on the continental slope will move into shallow-water shelf habitats as sea temperatures rise.

McClintock et al. 2008. American Scientist.McClintock et al. 2008. American Scientist.

McClintock et al. 2008. American Scientist.McClintock et al. 2008. American Scientist.