Notes on McGlashan et al's article, "Embryonic communication in the nest: metabolic responses of reptilian embryos to developmental rates of siblings": Materials and methods
2. Materials and methods
(a) Study species
Source: http://upload.wikimedia.org/wikipedia/commons/0/00/Pair_of_Emydura_macquarii_-_Warrawong.JPG accessed 5 December 2011
Murray Darling Basin in New South Wales and southeast Queensland, Australia
Source: http://upload.wikimedia.org/wikipedia/commons/7/7c/Murray-catchment-map_MJC02.png accessed 5 December 2011
terrestrial nests: nests dug in holes in the ground
68C = 154.4 degrees Fahrenheit
(b) Egg collection
funnel traps: this is the basic idea of a trap where the turtle enters through a funnel, and then can't get out, but don't take this too literally as being the actual trap they used, as I couldn't find a picture of that
Source: http://www.lakeborumba.com/images/Funnel-FishingTrap-lindr-250.gif accessed 5 December 2011
subcutaneous intramuscular injection: I think they just mean "intramuscular" here; "subcutaneous intramuscular" doesn't make much sense, as they're two different types of injection.
subcutaneous injections are administered just under the skin, as in
Source: http://www.nlm.nih.gov/medlineplus/ency/images/ency/fullsize/9954.jpg accessed 5 December 2011
By contrast, intramuscular injections are administered into the muscle, as in this image that shows both kinds of injections (ignore the intradermal injection, as that doesn't concern us here):
Source: http://juvenation.org/cfs-filesystemfile.ashx/__key/communityserver-discussions-components-files/130/7356.f0329_2D00_01.jpeg accessed 5 December 2011
oxytocin: a hormone that has many effects, from inducing labor in humans and other mammals to promoting bonding. There's way too much knowledge about oxytocin to go into here, but it's interesting that it has analogous effects (inducing labor, stimulating egg-laying) in animals that appear so different as humans and turtles
oviposition: laying eggs
clutch: all the eggs laid at the same time by one animal
(see electronic supplementary material for egg maintenance during incubation): at http://rspb.royalsocietypublishing.org/content/early/2011/11/24/rspb.2011.2074/suppl/DC1 accessed 5 December 2011
(c) Experimental design
hatching synchrony = hatching "same-time" = simultaneously hatching
induced = artificially stimulated or begun
developmental asynchrony = developmental "not-same-time" = development at different times from each other
Experimental treatments were designed to test whether less advanced embryos were either hatching prematurely or potentially adjusting developmental rates throughout the incubation period.
They were investigating whether the less advanced embryos sped up development to match the stage where the more advanced ones already were, or whether they kept going at their normal rate and just ran out of time at the end before finishing development.
26C: 78.8 degrees Fahrenheit
30C: 86 degrees Fahrenheit
31C: 87.8 degrees Fahrenheit
two-tailed t-tests: a statistical test to determine whether to reject the null hypothesis and consider the study's alternative hypothesis to be confirmed
VCO2: volume of carbon dioxide
(d) Metabolic and heart rates
closed system respirometry: respirometry is the measurement of metabolic rates, and here, they used carbon dioxide breathed out over time as a marker of metabolic rate. Because the system was closed, they knew no carbon dioxide was coming in from outside, so any increase in CO2 had to come from the turtles' breathing it out. Measuring that increase in CO2 over time gave them the rate at which the turtles were producing it, thus, their metabolism.
A Qubit (S500) respirometer (Kingston, ON, Canada) was used to measure carbon dioxide production
Source: http://qubitsystems.com/wp-content/uploads/S500%20matobox%20(from%20old%20site).jpg accessed 5 December 2011
Heart rates were recorded using the Buddy digital egg monitor system (Avian Biotech, UK), which is a non-intrusive method for measuring heart rates of embryos in eggs.
Source: http://i00.i.aliimg.com/photo/v0/214696894/Buddy_Egg_Monitor.jpg accessed 5 December 2011
infrared transmitters and sensors:
Source: http://coolcosmos.ipac.caltech.edu/cosmic_classroom/ir_tutorial/images/irbody.jpg accessed 5 December 2011
Heart rates (b.p.m.): beats per minute
Incubation period was measured as the number of days from initial egg collection until pipping. Pipping (when the eggshell is first slit) is better than hatching as an index of the end of the incubation period, because it shows less variability than hatching .
Another example of trying to cut down on confounds--since pipping is less variable than hatching, there is less opportunity for those variations to create confounds.
Source: http://3.bp.blogspot.com/_h-Njfq-hyBM/Sl4FjKu-kdI/AAAAAAAAAeY/rjbL_KcSS5M/s400/Pipping.JPG accessed 5 December 2011
(f ) Post-hatching development and growth
Righting trials--I think this means they flipped them, and timed how long it took the turtles to right themselves to a standing position, but don't take my word for this. I will look it up when I get to the university and can get behind the paywall to read the Colbert article, and will update at that point.
a membranous sac attached to an embryo, providing early nourishment in the form of yolk [Wikipedia: Yolk sac]
Source: http://www.redfoots.com/pics/esac-s.jpg accessed 5 December 2011
The volume of a cube (L x W x H) was used as a crude measure to calculate the volume of yolk.
callipers: British spelling of calipers
Source: http://upload.wikimedia.org/wikipedia/commons/9/94/Messschieber.jpg accessed 5 December 2011
straight carapace: the carapace is the dorsal (back) shell of the turtle, composed of the spine and rib fused with dermal plates. This image shows the components of the carapace.
source: http://upload.wikimedia.org/wikipedia/commons/1/1f/Bojanus_fig9.jpg accessed 5 December 2011
plastron: the ventral or abdominal shell of a turtle
Source: http://upload.wikimedia.org/wikipedia/commons/6/6e/Midland_painted_turtle%2C_plastron%2C_young.jpg accessed 5 December 2011
marginal scutes on carapace
Source: http://www.turtlejournal.com/terrapindiary/lewis02/gallery/marking1.jpg accessed 5 December 2011