Circulating α-Tocopherol and Retinol Concentrations in Free-Ranging and Zoo Turtles and Tortoises
Abstract
Although clinical signs of vitamin E imbalances have not specifically been reported in chelonians, plasma concentrations of this nutrient have been shown to vary directly with dietary content in other species.1,2 Hence, blood samples can provide a basis of quantitative evaluation of vitamin E status. Conversely, vitamin A status and dietary adequacy cannot be as readily assessed by blood sampling.3 Vitamin A-responsive syndromes have been reported in numerous turtle and tortoise species. Toxicities and induced fat-soluble vitamin antagonisms should also be considered in evaluating the nutritional health of reptiles. Samples were opportunistically obtained from turtles and tortoises during normal zoo medical procedures, and during field work with free-ranging specimens. Plasma was separated by centrifugation, and samples were stored frozen (-20°C to -70°C, or liquid nitrogen) for no more than 6 mo prior to analysis using high performance liquid chromatography as per standardized laboratory methods that have been previously detailed.5 These survey data were compiled to contrast and compare “physiologically normal” circulating levels of tocopherol and retinol, as measures of vitamin E and A assessment, respectively, in non-aquatic chelonian species. A total of 547 blood samples from 24 species are summarized in Tables 1 and 2.
Table 1. Circulating tocopherol and retinol concentrations measured in selected turtle species (x±SD)a
|
Species
|
n
|
Sampling location(s)
|
α-tocopherol
μg/ml
|
γ-tocopherol
μg/ml
|
Retinol
μg/ml
|
|
Callagur borneoensis
Painted terrapin
|
3
|
1 US zoo
|
2.65±0.94
|
n.d.b
|
0.11±0.06
|
|
Chelydra serpentina
Snapping turtle
|
21
|
1 US zoo
|
3.28±1.71
|
n.d.
|
0.35±0.15
|
|
4
|
NY, USA
|
3.77±2.85
|
n.d.
|
0.31±0.25
|
|
Chrysemys picta
Painted turtle
|
47
|
2 US zoos
|
5.21±3.19
|
n.d.
|
0.16±0.09
|
|
Clemmys guttata
Spotted turtle
|
22
|
NY, USA
|
6.93±3.22
|
n.d.
|
0.22±0.09
|
|
5
|
1 US zoo
|
2.45±0.56
|
n.d.
|
0.08±0.04
|
|
Clemmys muhlenbergii
Bog turtle
|
2
|
NY, USA
|
17.23±0.03
|
n.d.
|
0.28±0.05
|
|
Cuora amboinensis
Malayan box turtle
|
2
|
1 US zoo
|
10.30±5.35
|
n.d.
|
0.19±0.01
|
|
Cuora galbinifrons
Indochinese box turtle
|
1
|
1 US zoo
|
6.96
|
n.d.
|
No data
|
|
Mauremys caspica
Caspian turtle
|
1
|
1 US zoo
|
7.85
|
n.d.
|
0.06
|
|
Podocnemis erythrocephala
Red-headed Amazon river turtle
|
9
|
1 US zoo
|
6.82±5.15
|
0.15±0.05
|
0.10±0.08
|
|
Sternotherus odoratus
Common musk turtle
|
11
|
NY, USA
|
6.64±2.10
|
n.d.
|
0.04±0.02
|
|
Terrapene carolina carolina
Eastern box turtle
|
3527
|
2 US zoos
NY, USA
|
3.91±6.42
5.37±3.34
|
n.d.
0.23±0.13
|
0.06±0.06
0.14±0.07
|
|
Terrapene carolina triunguis
Three-toed box turtle
|
3
|
1 US zoo
|
2.01±0.95
|
n.d.
|
0.07±0.04
|
aAll data from Wildlife Conservation Society Nutrition Laboratory, summarized through Jan 99.
bNone detected.
Table 2. Circulating tocopherol and retinol concentrations measured in selected tortoise species (x±SD)a
|
Species
|
n
|
Sampling location(s)
|
α-tocopherol
μg/ml
|
γ-tocopherol
μg/ml
|
Retinol
μg/ml
|
|
Geochelone carbonaria
Red-footed tortoise
|
1
|
1 US zoo
|
0.68
|
n.d.b
|
0.32
|
|
Geochelone chilensis
Chilean tortoise
|
1
|
1 US zoo
|
0.47
|
n.d.
|
0.47
|
|
Geochelone denticulata
Yellow-footed tortoise
|
1
|
1 Guatemalan zoo
|
2.36
|
n.d.
|
0.08
|
|
Geochelone elephantopus
Galapagos tortoise
|
9
|
1 US zoo
|
1.54±0.68
|
0.08±0.02
|
0.23±0.06
|
|
Geochelone gigantea
Aldabra tortoise
|
34
|
2 US zoos
|
2.20±2.09
|
0.27±0.02
|
0.33±0.06
|
|
Geochelone pardalis
Leopard tortoise
|
7
|
3 US zoos
|
6.58±6.99
|
0.71±0.44
|
0.56±0.66
|
|
Geochelone radiata
Radiated tortoise
|
30
|
3 US zoos
|
2.60±1.38
|
0.39±0.19
|
0.25±0.12
|
|
Gopherus polyphemus
Gopher tortoise4,6
|
155
|
GA & FL, USA
|
1.56±1.04
|
0.14±0.07
|
0.17±0.08
|
|
Indotestudo elongata
Elongated tortoise
|
2
|
1 US zoo
|
1.71±1.24
|
n.d.
|
0.04±0.03
|
|
Malacochersus tornieri
Pancake tortoise5
|
37
|
Tanzania - 2 sites
|
2.34±1.17
|
0.21±0.06
|
0.34±0.12
|
|
Testudo graeca nikolskii
Russian spur-thighed tortoise
|
75
|
Russia - 4 sites
|
4.66±2.62
|
0.13±0.07
|
0.61±0.16
|
|
Testudo hermanni
Spur-thighed tortoise
|
2
|
1 US zoo
|
0.52±0.12
|
n.d.
|
0.10±0.03
|
aAll data from Wildlife Conservation Society Nutrition Laboratory, summarized through Jan 99.
bNone detected.
Comparative values among species which occupy differing ecologic habitats, and particularly differences between free-living and zoo-held species, need to be interpreted with caution. Variables that are known to affect concentrations (e.g., sex, age, seasonality, and diet)1-6 need to be better examined through controlled feeding trials with chelonians to allow adequate data interpretation. Nonetheless, some useful broad interpretations can be made. 1) In general, the more herbivorous tortoise species tended to display lower circulating levels of α-tocopherol than more omnivorous chelonians. 2) Further, levels of α-tocopherol measured were comparable to ranges reported for dietetically equivalent (herbivorous vs. omnivorous) mammalian species.1,2 3) Additionally, a greater proportion of tortoise species examined displayed measurable concentrations of γ-tocopherol in blood samples compared with turtles. Gamma-tocopherol isomers are found almost exclusively in plant-based tissues, whereas α-tocopherol is distributed in both animal and plant tissues. The presence/absence of specific tocopherol isomers may be useful to distinguish differences in primary dietary ingredients. 4) With some exceptions, retinol concentrations in turtles and tortoises were at the lower end of the expected normal range for domestic livestock species (0.2 to 0.8 μg/ml). 5) Where direct species comparisons were possible between free-living and captive populations, no statistically significant differences were noted.
Literature Cited
1. Dierenfeld, E.S. 1989. Vitamin E deficiency in zoo reptiles, birds and ungulates. J. Zoo Wildl. Med. 20:3–11.
2. Dierenfeld, E.S. and M.G. Traber. 1992. Vitamin E status of exotic animals compared with livestock and domestics. Pp. 345–360. In: Vitamin E in Health and Disease, L. Packer and J. Fuchs, eds. Marcel Dekker, Inc., New York.
3. Gibson. R.S. 1990. Principles of Nutritional Assessment. Oxford University Press, New York.
4. Raphael, B.L., E.S. Dierenfeld, and J. Spratt. 1995. Circulating vitamin A & E concentrations of free-ranging gopher tortoises (Gopherus polyphemus). Proc. 5th Internat. Symp. Pathol. Reptiles & Amphibians, Alphen a/d Rijn, The Netherlands.
5. Raphael, B.L., M.W. Klemens, P. Moehlman, E.S. Dierenfeld, and W.B. Karesh. 1994. Health profiles of free-ranging pancake tortoises (Malacochersus tornieri). J. Zoo Wildl. Med. 25:63–67.
6. Raphael, B.L., J. Spratt, J. Behler, E.S. Dierenfeld, R. Hayes, and B. Winn. 1996. Health status of a colony of translocated gopher tortoises (Gopherus polyphemus). Proc. Wildl. Dis. Assoc., Fairbanks, AL. P. 81 (abstract).