Why measure UVB to manage Vitd3 p.synthesis ?

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Re: Why measure UVB to manage Vitd3 p.synthesis ?

Postby claudiusx » Fri Jun 28, 2019 8:04 pm

Now im done in this thread.
You'll post anyways in response because you always have to have the last word. But just try to do some unbiased research instead of cherry picking what agrees with you.

-Brandon
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Re: Why measure UVB to manage Vitd3 p.synthesis ?

Postby kingofnobbys » Fri Jun 28, 2019 9:27 pm

claudiusx wrote:Im not talking about summer in Australia vs the us, I'm talking about you using a chart of uv levels during a SOLSTICE. Do you not read the charts you post? Do you not understand what a solstice is? Or do you purposely post misleading charts and hope no one will notice. Saying 200 uW is acceptable because a chart during a SOLSTICE shows levels in the 400 is extremely ill founded.

And you can go ahead and read Francis' articles yourself. Unlike you, my ego doesn't dictate that everyone think im smart or know it all. I care about false dangerous information and suggestions being spread, and dont care who has to be listened to for that to stop.
So if I don't fit your criteria of credible (idk how I'll sleep tonight now that I know you think that of me) then open up your mind, leave your ego at the door, and go read Francis' work. Although its clear if you don't agree with it, its wrong. But just try huh, you can do it.

-Brandon


I've seen her site and read her articles.
Don't need to do so again. I am also aware her site has large sections made private and which are under revision and being updated / corrected.

You are just badgering and not contributing anything substantive to this.
CBDs: Cleopatra & Caesar born 28Jan19.
Puff (RIP 10Dec15),Rex (RIP 16Mar17),Toothless (RIP 26Nov17).Peppa (RIP 22Mar19).
EBTSs : George & Mildred (born july 2010).
EWSs : Fluffy - 4yr rescued lawnmowing accident victim 14Nov17.
Lucky - cat attack rescue, fatal SI RIP 21Jul2010.
Wriggles - rescued injured ,thought she was a big lizard, over 8 yrs old, RIP 2Feb16. .
Gecko : Godzilla the hatchling GEHYRA GECKO (hatched May 2019)
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Re: Why measure UVB to manage Vitd3 p.synthesis ?

Postby kingofnobbys » Thu Jul 11, 2019 7:07 pm

Posted elsewhere and here to show the scientific basis for using UVB flux to control VitD3 photosynthesis in your reptile's skink and to show why UV-Index is not a good measure for reptilian UV response.

My apologies for the high level of the science in the papers cited below , but to get a handle on this one needs to try to get a grip on the science and measured data related to this.
Added here for completeness so it doesn't get buried in the other thread.

Some real physical data from the natural range of pogona species of the UV irradiance in typical summer months (peak of the pogona breeding season in their natural range) that is not supportive of using UV-Index to control pogona UV irradiation and supports higher levels of UVB irradiation ( and UVA too) than advocated some here.

I have several other peer reviewed scientific papers that support my philosophy regarding UV irradiation levels
I started investigating what should be best husbandry practices for the species I've been keeping because of my unease about the disparaty and vagueness of the advise given by self appointed lay experts who have little or no formal scientific training who at best can only to provide anecdotal "evidence" unsupported by hard testable observational measurements that can not reproduced or independently tested in any meaningful way ( somewhat of an issue across the board in this hobby of herpetology).
No small wonder noobs mess up.

Measurements of global spectral irradiance in the UV and visible range were carried out during December 1995 and January 1996 in Townsville, Australia (19.33 degS, 30 m above sea level ) were carried out during December 1995 and January 1996 in Townsville, Australia
using the mobile [scanning] spectroradiometer [provided by the Fraunhofer Institute for Atmospheric Environmental Research].

[ my comment : typical latitude for pogona species , you will note there is no mention of UV-index in this peer reviewed scientific paper ]

The maximum erythemally weighted (UVB) irradiance measured during the campaign was 429 mW/m^2 ( 429 microW / sq.cm) , and the average daily erythemal irradiation for this period was 6.06 kJ/m^2 .


For the year 1991, the December and January values of the monthly mean daily erythemal irradiation found in the survey for Darwin, Brisbane and Perth are as follows:
Darwin, 5.70 kJ/m^2 (December) and 3.72 kJ/m^2 (January)
Brisbane 4.76 kJ/m^2 (December) and 4.47 kJ/m^2 (January)
Perth 5.30 kJ/m^2 (December) and 5.77 kJ/m^2 (January).


The albedo of sand is about 10% in the UV [Blumthalear & Ambach]. According to model calculations UV levels for "desert areas" [dry grasslands and dry woodlands are regarded by these researchers from Germany as "deserts"] should be approximately 3% higher than for forested land.


Source :
Measurements of spectral solar UV irradiance in tropical-Australia.
. Bernhard, B. Mayer, and G. Seckmeyer
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 102, NO. D7, PAGES 8719-8730, APRIL 20, 1997
URL = https://agupubs.onlinelibrary.wiley.com ... /97JD00072

Notes
Spectroradiometers are instruments that measure the intensity of radiation as a function of wavelength.
Sampling is generally made at intervals of about 0.5 nm and at relatively high resolution, with full width half intensity (FWHI) less than 1.0 nm.
There are two means by which wavelength sampling is carried out. One uses a single detector and mechanically scans the spectrum across the detector to sample the targeted wavelength range one wavelength at a time.
The second type of instrument uses relatively new array detectors that measure all wavelengths
simultaneously over the targeted spectral range.
Both types of spectroradiometers require careful characterization, and significant effort is required to calibrate the instruments and account for any instrumental dependencies.

The UV index is based on erythemal (HUMAN skin reddening) exposure, since this has the most immediate short-term impact on humans.
It has not been developed nor is relevant to non-human (non- naked mammalian skins ie NOT for reptilian skins or specially evolved skins such that on pogona species , for these there is no model available a.t.m and it is known pogona have evolved the ability to change their skin's IR emissivity and UV albedo at will depending on the temperature and UV irradiance) .
Further
P. vitticeps modify both visible (UV-Vis range) and NIR reflectance to accommodate requirements of signalling or camouflage and thermoregulation during light phases, they are in a rest state during dark phases and have little need to display colour change for other purposes, which may explain their higher proportion of UV-Vis reflectance.
This variation in the proportion of UV reflectance is a function of a change in the spacing of reflecting platelets in iridophores , in combination with melanosome dispersion.

The scales on a reptile act as a barrier for moisture loss , and are highly transparent in UVA & UVB bands.

(OBSERVE MAMMALS (ie humans) DO NOT HAVE THIS ADAPTATION).

Light acts as a stimulus for the pituitary to release MSH, resulting in the dispersion of melanosomes and the aggregation of reflecting platelets. The aggregated reflecting platelets is thus associated with a decrease in the proportion of UV reflectance in relation to NIR reflectance, although the mechanisms moderating NIR reflectance are currently unknown.

I have seen scans of the % UV transmissivity of fish and reptile scales as a function of wavelength created using commonly available scanning UV-Vis spectrophotometers (as found in all chemistry laboratories and even in some high schools).
Some interesting studies on this (unfortunately didn't include pogona species) is here
American Society of Ichthyologists and Herpetologists (ASIH) Copeia Vol. 1959, No. 4, Dec. 30, 1959 pp 311 - 315.

Response to photoperiodic exposure to UV
https://www.ncbi.nlm.nih.gov/pmc/articl ... objectonly

sources
Cyclic Colour Change in the Bearded Dragon Pogona vitticeps under Different Photoperiods.
Marie Fan, Devi Stuart-Fox, and Viviana Cadena
PLoS One. 2014; 9(10): e111504
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4213017/

Reptilian Skin and Its Special Histological Structures
Catrin Sian Rutland, Pia Cigler and Valentina Kubale
Veterinary Anatomy and Physiology :
Published: March 13th 2019
url https://www.intechopen.com/books/veteri ... structures

VERY BASIC STUFF :
The definition of the UV Index is erythemally weighted global irradiance divided by 25 mW / m^2. (or by 25 microW / sq.cm).
This yields a non-dimensional value that typically can reach a value of 10 under clear-sky conditions at noon for mid-latitude locations during summer. For subtropical and tropical southern hemisphere sites the value can exceed 16.

W/m^2 or mW / cm^2 or microW / cm^2 are the SI units for UV flux (p/unit of area) and the SI unit of irradiation is J/m^2 .
Other dimensionless units are fudges at best since they are at best a poor estimate of erythemal irradiance expressed in an non-standardised unit called the UV-Index as already shown else in the calibration and response curve provided by SolarMeter Corp..
CBDs: Cleopatra & Caesar born 28Jan19.
Puff (RIP 10Dec15),Rex (RIP 16Mar17),Toothless (RIP 26Nov17).Peppa (RIP 22Mar19).
EBTSs : George & Mildred (born july 2010).
EWSs : Fluffy - 4yr rescued lawnmowing accident victim 14Nov17.
Lucky - cat attack rescue, fatal SI RIP 21Jul2010.
Wriggles - rescued injured ,thought she was a big lizard, over 8 yrs old, RIP 2Feb16. .
Gecko : Godzilla the hatchling GEHYRA GECKO (hatched May 2019)
kingofnobbys
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