Underwater

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Irregular underside of the ice due to ice platelet growth

Kevin Hoefling

Under Ice Diving McMurdo Sound

Sea Urchin holding a piece of algae shrouded with platelet ice

Isopod grazing on ice crystals

Body fluids Isosmotic to SeawaterTherefore invertebrates will not

freeze????

Met

ers

3

10

20

30

300

400

500

SEA ICE 2-3 meter

PLATELET ICE 3-4m

G. acuticeps

T. bernacchii

H. vellifer

P. macropterusT. hansoni

P. antarcticum

T. loenbergii

eelpout

liparid

P. borchgrevinki

Fishes of McMurdo SoundM

eter

s

3

10

20

30

300

400

500

SEA ICE 2-3 meter

PLATELET ICE 3-4m

G. acuticeps

T. bernacchii

H. vellifer

P. macropterusT. hansoni

P. antarcticum

T. loenbergii

eelpout

liparid

P. borchgrevinki

D. mawso

ni

Fishes of McMurdo Sound

Antarctic polyps

and sponges

White Blood is Hall Mark ofChannicthyid Ice Fishes

Hemoglobin-less Channichthyid Ice fish Blood

Red-Blooded Nototheniid fish

Pagetopsis macropterus

Common Shallow Water Benthic Trematomus (nototheniid) Fishes

• Trematomus bernacchii

•Trematomus pennelli

•Trematomus newnesi

•Trematomus nicolai

McMurdo Sound Trematomus fish Resting on Anchor Ice

Antarctic toothfish

Dissostichus mawsoni

Pagothenia borchgrevinki (borks)Hiding In Ice Crevices In “Ice

Foot”!

How do invertebrates and Fishes avoid freezing in the ice-laden seawater?

• Can they warm themselves? No!

• Can they insulate themselves? No!

• Can they supercool? No!

Cold-blooded Fish and Invertebrates Beneath the Ice

• Produce little body heat.

• Unable to conserve heat because the large gas exchange surfaces (gills) act as radiators resulting in loss of any heat in the blood.

• As a result the body temperature is the same as that of seawater.

Fish theoretically can avoid freezing by supercooling; PROBLEM is there are ice crystals around !

Fish blood osmolytes (600 mOsm) -1.0oC

ColligativeF.P.

F.P. of seawater (1000 mOsm) -1.9oCNaCl

Strategies of Freezing Avoidance

Sink or Swim

Add small osmolytes

MacromolecularAntifreeze Proteins

In Antarctic notothenioid fish:

AFGP (30-40 mg/ml) 1.4oCBlood osmolytes (NaCl) ~600 mOsM) 1.0oC

F.P.

Total F.P. 2.4oC

F.P. of seawater (1000 mOsm) -1.9oC

Freezing is avoided by ~ 0.5oC of protection!

AFGP – Antifreeze Glycoprotein

n= 4 to 88m.w.= 2,600 to 56,000 Da

(a family of size isoforms)

Saffron codE. gracilis

Polar codB. saida

Greenland codG. ogac

Atlantic codG. morhua

AAT-AAT-PAT-AAT-PAT-AAT-AAT-etc

disac disac disac disacdisac disacdisac

AAT-AAT-PAT-AAT-PAR-AAT-AAT-etc

disac disac disacdisac disacdisac

Antarctic notothenioid :

Northern cod :

The other half of the story:AFGP in Northern Gadids (Cods)

AntifreezePeptides(4 types)

• Type I: 3-4 kDa

• Type II: ~14 kDa

• Type III: 7 kDa 14 kDa

• Type IV: ~15 kDa

Freezing Avoidance in Frigid Marine Environment

Where did antifreezes come from and how did they evolve?

…gactgggactagaaattcg….

Most genes evolve from pre-existing genes:• Characterize antifreeze genes• Inferred evolutionary ancestry through significant sequence similarity

Antifreeze Glycoprotein

EvolutionaryPrecursor/Homolog

EvolutionaryMechanism

AntarcticNotothenioid

AFGP

Trypsinogen-likeserine protease

(TLP)

Recruitment of TLP gene segments

and de novoamplification of 9-nt

ThrAlaAla coding element

Northern and ArcticCod AFGP

??(not TLP)

???

Antifreeze Peptide

EvolutionaryPrecursor/Homolog

EvolutionaryMechanism

Type I AFP ?? ??

Type II AFP CRD of Ca++-type lectin domain duplication& sequence divergence

Type III AFP sialic acid synthaseC-terminus

domain duplication& sequence divergence

Type IV AFP apolipoprotein domain duplication& sequence divergence

NotothenioidAFPP*

globular domainof blood complement

C1Q

domain duplication& sequence divergence