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Conservation and Ecology of Marine Reptiles
MARE 490Dr. Turner
Summer 2011
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