Conservation and Ecology of Marine Reptiles

MARE 494Dr. Turner

Summer 2006

Thermo & Osmo RegulationLive in unique marine media that causes problems with thermal biology and regulation of salt & water

Like other marine animals have adaptations which allow for survival

Thermal BiologyUltimately tied to thermal constraints of their environment

Sea turtles are unusual among reptiles – large body size allow adults to use insulation & blood flow to alter (control) body temperature (Tb)

Large difference in thermal patterns among hatchlings, juveniles, & adults

Conformer: Physiological state = environment

Regulator: Physiological state different from environment

Bo

dy

Tem

p

Ambient Temp

0 10 20 30

Conformer

Regulator

Thermal Biology

???

Heat Exchange

Lets Get BiophysicalEnergy exchange controls the TB of sea turtle

Chemical energy drives metabolism & provides and internal heat source

Energy from the environment is main source of heat for sea turtles (land or sea) except for very large animals

Surf & TurfIn water thermal radiation absorbed near surface – heat exchange is by:

ConductionConvection

On land heat energy exchange is by:RadiationConvectionEvaporationConduction

Energy Balance EquationsQabs + M = R + C + E + G

Qabs = radiation absorbed by the surface of the animal from the sun

M = metabolic heat productionR = thermal heat emitted by surface of the animalC = heat energy lost by convectionE = heat energy lost by evaporation/gained by condensationG = heat energy lost or gained by conduction through direct contact with soil, water, or substrate

HEAT IN = HEAT OUT + HEAT STORED

Land!Sea turtles nest at night because exposure to the hot sun during the day would lead to lethal heat gain

Gradient across thickness of carapace & plastron causes internal heat lag between surface & deep body

However, deep body it not great enough heat sink to sustain but a few degrees ambient temperature increases

Basking!Sea turtles bask on land & in water

Turtles that bask on land typically seek out beaches facing outer reefs and prevailing trade winds

Lower temps than on beaches on opposite side of Island

Do we see this in practice?Punalu‘u versus Kona

Regulate to RegulateHow do basking turtles regulate internal temperatures?

Flip sand onto flippers & carapacereduce surface temperature > 10°C

Flipper into waterreduce surface temperature > 10°C+

Cold-StunnedOccurs when temperatures drop below 8°C

Lose ability to swim & dive, buoyancy control, float to surface, & die

Probably disruption of metabolic pathways

Thermoregulation?Are leatherback sea turtles homeothermic?

Metabolic rate higher than cheloniids; higher than typical reptile scaled to its size

Still ½ the metabolic rate of mammals

May allow enough for these large turtles to function at very cold temperatures during deep diving bouts – oceanic existence

Tag’em & Bag’em“Since they stopped testing on animals, a guy like me can really clean up!”

– Barney Gumble

Osmoregulation?Are leatherback sea turtles homeothermic?

Metabolic rate higher than cheloniids; higher than typical reptile scaled to its size

Still ½ the metabolic rate of mammals

May allow enough for these large turtles to function at very cold temperatures during deep diving bouts – oceanic existence

Coping with Salinity

Some

mollu

scs

“Yaarh! I hate the sea and everything in it” - Captain Horatio McCallister

Osmo Kramer

Sea turtles live in medium that is almost 3X more concentrated than body fluids

Some ions greater – 23X Mg2+

Must maintain internal osmotic & ionic homeostatis

“These pretzels are making me thirsty!” – Kosmo Kramer

Salt!Salt Concentration

Reptile ProfileRespiration not a major source of water loss in marine reptiles

Water loss function of permeability of transcutaneous osmotic gradient

Water loss via urine & feces (cloaca) low

Na+Na+Na+Na+, HeyHeyHey, GoodbyeNa+ efflux at similar levels to marine elsambranchs (lower than teleosts)

Sea turtles have low epithelia permeability for Na+

Bulk of salt loss is from salt gland60% in loggerhead90% in green

Salt IngestionIngestion major source in salt intake

Esophagus provides protection against incidental drinking – papillae & sphincter

help to “trap” food; expel water

Glands!Reptiles have a unique variety of organs used as salt glands

Salivary glands – sea snakes

Lingual glands – crocodiles

Nasal glands – lizards

Lachrymal gland – sea turtles 2X size of leatherback brain

Salt Gland Powers, Activate

When actived - discharges a fluid6X that of blood; 2X seawater

When inactive – ¼ the concentrating capability

Greater than marine birds; 2X shark rectal gland

Unlike avian glands – remove Mg2+

“Brian, take out your ring. Wonder Twin powers activate. Shape of steam.” "Peter, we got these from a box of fruit loops” – Peter & Brian Griffin

Salt Gland vs. Kidney