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Axanthism in Emys orbicularis hellenica (Valenciennes, 1832) (Testudines: Emydidae) from Piedmont, northern Italy

Authors:
  • Centro Emys Piemonte - Eleade Soc. Coop.
  • Independent scientist

Figures

36 Herpetological Bulletin 146 (2018)
The European pond Turtle Emys orbicularis (Linnaeus,
1758) is a polytypic and polymorphic species with a
western palearctic distribution for which several subspecies
were described based on molecular and morphological
differences (Lenk et al., 1999; Fritz, 2003). In Italy, three
subspecies are currently recognised: E. o. ingauna Jesu,
Piombo, Salvidio, Lamagni, Ortale & Genta, 2004 in
Liguria, E. o. galloitalica Fritz, 1995 along the Tyrrhenian
coast and E. o. hellenica (Valenciennes, 1832) on the
Adriatic one (Zuf et al., 2011).
In the latter, the coloration is typically characterised
by a black carapace with yellow elements (spots in males
and lines organised in radial pattern in females) and a
yellow plastron. Yellow areas are also present on soft parts
like specks on limbs and also on the head in females. Iris
coloration is usually white or yellow in males (Zuf et al.,
2011), sometimes reddish (R. Cavalcante pers. obs.), while
females typically possess a yellow iris (R. Cavalcante
pers. obs.). As in other Mediterranean subspecies, E. o.
hellenica hatchlings present a well-dened yellow pattern
on the marginal scutes of the carapace and the plastron is
covered for at least two-thirds by a black central blotch,
leaving yellow coloration only on the lateral rim (Fritz et
al., 2006).
Given that E. o. hellenica is at risk of local extinction in
Piedmont (Zuf et al., 2011, Seglie & Cavalcante, 2016),
the Conservation Centre “Centro Emys Piemonte” has been
implemented in 2016, provided with an outdoor breeding
facility. The main activity of the Centre was to rescue adult
individuals in the Po and Orba natural reserves to create
breeding groups, which would then provide 3-4 years old
individuals to be reintroduced in restored habitats. All of
these operations were authorised by the Italian Ministry of
Environment, Land and Sea (Protocol number 0015025/
PNM-28/07/2015). A molecular characterisation was
carried on rescued individuals by Ana Rodriguez Prieto at
Museo delle Scienze (MUSE) in Trento, which ascribed
all the turtles to the hellenica subspecies. The outdoor
breeding facility is designed to allow the collection of the
eggs right after the deposition for articial incubation.
However, not all the nests are easy to spot, and some litters
are discovered only at the time of hatching.
On 3 September 2017 during an inspection of these
nests, in an area where three females and one male were
kept, two out of twenty-nine hatchlings were found to
display an anomalous coloration. In these individuals,
Axanthism in Emys orbicularis hellenica (Valenciennes, 1832)
(Testudines: Emydidae) from Piedmont, northern Italy
RICCARDO CAVALCANTE1* & GIACOMO BRUNI2
1Centro Emys Piemonte, Via Vasco Vittone, 6 13046 Livorno Ferraris (VC), Italy
2Vrije Universiteit Brussel, Boulevard de la Plaine 2, 1050 Ixelles, Bruxelles, Belgium
*Corresponding author Email: scaval_@hotmail.it
SHORT COMMUNICATION The Herpetological Bulletin 146, 2018: 36-38
portions of the carapace, plastron and soft parts that are
typically yellow present a whitish-greyish coloration (Fig.
1A), and the iris is dark brown (Fig 2A). This particular
coloration was never observed before in wild individuals
or in other hatchlings born in the Centre (10 in 2016, 38 in
2017 and 44 in 2018).
Yellow, orange and red coloration in reptiles are
produced via the interaction between xanthophores
and the underlying iridophores (Cooper & Greenberg,
1992; Morrison et al., 1995; Steffen & McGraw, 2009).
Xanthophores contain pteridines like xanthopterin,
sepiapterin and riboavin inside pterinosomes and
carotenoids like carotenes and xanthophylls in carotenoid
vesicles (Obika & Bagnara, 1964; Watt, 1964; Bagnara &
Hadley, 1973; Morrison et al., 1995). Iridophores contain
guanine crystals responsible for structural coloration given
Figure 1. Comparison of the plastron of an axanthic individual
(left) with the one of a normal coloured individual (right): (A)
hatchlings in September 2017; (B) one-year old juveniles in
September 2018
by light reecting properties which depends on platelets’
size and disposition (Bagnara, 1966). Regarding pigments
within xanthophores, pteridine pigments have a major role
in reptiles, while carotenoids seem to be less important
(Olsson et al., 2008; Steffen & McGraw, 2009) and
sometimes to be even absent (Kikuchi & Pfennig, 2012;
Olsson et al., 2013). While carotenoids are assimilated
from the diet (Olson & Owens, 1998), pteridine pigments
are endogenously synthesised from purines (Watt, 1967).
Colour aberration for which a reduction or absence of yellow
occurs is known as axanthism, and it can be generated
through a lack or non-functionality of xanthophores and
iridophores (Jablonski et al., 2014).
Considering that the pale coloration was maintained by
both individuals in their rst year of life, whilst becoming
slightly yellow (Figs. 1B and 2B), we assume that
xanthophores are present and that this mild “yellowing”
may be caused through carotenoids sequestered from
the diet, since they have been also fed with KOI beauty
First (Tetra®), food pellets which contain β-carotene.
Therefore, it is probable that the observed axanthism
involves primarily iridophores or some metabolic defects
in pteridine production (Olsson et al., 2013).
In literature, axanthism and other chromatic anomalies
were never reported before in the European pond Turtle.
Axanthism seems also rare in general in testudines, since
only cases of albinism (e.g. Türkozan & Durmuş, 2001;
Sönmez & Özdilek, 2011), leucism (e.g. Erickson &
Kaefer, 2015), melanism (e.g. Yabe, 1994; Gronke et al.,
2006), hypomelanism (e.g. Turner, 2011; Di Giuseppe et
al., 2014) and amelanism (e.g. Martìnez Silvestre & Soler,
2001) are currently published.
ACKNOWLEDGEMENTS
The permit for the collection, the housing and the breeding
of the European pond Turtles was issued by the Italian
Ministry of Environment, Land and Sea (Prot. 0015025/
PNM-28/07/2015).
We would like to thank Silvia Fiore and Renzo Aimaro
of the Associazione Culturale Docet Natura for their great
help in the conservation project, Daniele Seglie for his
precious teachings, help and patience, the Management
Entities of the protected areas of Po vercellese-alessandrino
and Park Pallavicino for their collaboration, Ana Rodriguez
Prieto for the molecular characterisation of the animals,
the veterinarian Giancarlo Barlaro for his essential support
and Giorgio Russo for the linguistic revision and his useful
suggestions.
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Herpetological Bulletin 146 (2018) 37
Figure 2. Comparison between one-year old axanthic (left) and
normal coloured (right) individuals: (A) coloration of head and
eyes; (B) coloration of the carapace
Axanthism in Emys orbicularis hellenica
38 Herpetological Bulletin 146 (2018)
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Accepted: 27 November 2018
Riccardo Cavalcante & Giacomo Bruni
... Colour aberrations in turtles range from the nearcomplete lack of color in albinos to very dark in melanistic individuals, but also other variations such as yellow, without yellow, and golden yellow ones (Jubber & Leyendecker, 2016;Cavalcante & Bruni, 2018;Devkota et al., 2020). We did not find any previously reported cases of amelanism or any other abnormal coloration in T. grayi under its current or previous Herpetological Bulletin 162 (2022) (Perrault & Coppenrath, 2019). ...
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