Partial albinism in Sibynomorphus ventrimaculatus

Herpetology Notes, volume 7: 475-476 (2014) (published online on 25 August 2014)
Partial albinism in Sibynomorphus ventrimaculatus
(Boulenger, 1885) (Serpentes: Dipsadidae) in
Rio Grande do Sul state, Brazil
Arthur Diesel Abegg1,*, Conrado Mario da Rosa1, Camila Pivetta Cavalheiro1,
Flora Roncolatto Ortiz2 and Leandro Malta Borges1
Albinism is a condition caused by homozygous
recessive alleles, which prevent an individual from
producing melanin, the pigment responsible for the
dark colors (e.g., black and brown) in animals (Griffiths
et al., 1998; Alberts et al., 2004). Although it is a rare
phenomenon in wild tetrapods, this chromatic anomaly
has a frequency of 1 in 20,000 individuals across all
vertebrate classes (Bérnils et al., 1990; Alberts et al.,
2004; Oliveira, 2009; Santos and Silva, 2010; Nogueira
and Alves, 2011; Veena et al., 2011; Noronha et al.,
2013). Partial albinism is characterized by the absence of
melanin in certain body regions, with the skin presenting
a white color with pigmented zones, or producing
lighter shades of the common colors (Cademartori and
Pacheco, 1999).
On 17 February 2014 at around 1000 hrs one adult male
specimen of Sibynomorphus ventrimaculatus (Fig. 1B)
was found under construction debris in an urban zone
of the city of Santa Maria (29°42’26.2” S, 53°51’52.3”
W), Rio Grande do Sul, Brazil. The specimen was
photographed, captured, euthanized by intercoelomic
injection with sodium pentobarbital, and deposited in
the herpetological collection of the Instituto Butantan
“Alphonse Richard Hoge” (IBSP), and accessioned
as IBSP 85.286. Measurements included a snout-vent
length of 360 mm, tail length of 94 mm, and weight
of 14 g. A liver sample was collected for molecular
analysis.
Universidade Federal de Santa Maria, Avenida Roraima,
1.000, Camobi, CEP 97105-900, Santa Maria, RS, Brazil.
2
Instituto Butantan, Avenida Vital Brasil, 1.500, Butantã, CEP
05503-900 São Paulo, SP, Brazil.
* Corresponding author. E-mail: [email protected]
1
The geographic distribution of S. ventrimaculatus
encompasses the Brazilian states of Rio Grande do Sul,
the eastern region of Paraná, southern São Paulo, Mato
Grosso do Sul, and the northeast of Argentina (Franco,
1994; Giraudo and Scrocchi, 2002). The species has a
terrestrial habit and is nocturnal (Laporta-Ferreira et
al., 1986; Franco, 1994), with a diet consisting of slugs
and snails (Oliveira, 2001; Lema, 2002). It is oviparous,
with clutches comprising 4–5 eggs (Leitão-de-Araújo,
1978; Pontes and Di-Bernardo, 1988). Its defensive
behavior consists of expelling cloacal contents, hiding
its head under the body, erratic movement, and head
triangulation (Abegg and Entiauspe, 2012). According
to Franco (1994), chromatic differences, especially in the
dark patches of the dorsal pattern, exist in populations
of this species across Brazil. However, on the venter all
patterns exhibit numerous randomly distributed dark
patches with irregular edges (Fig. 1A).
The typical dark dorsolateral patches are present in
the partially albinistic specimen, but in lighter shades
as compared to normally colored specimens; some even
have a pink shade. In contrast, the dark patches in the
ventral region of this individual almost disappear, with
the remaining few distanced from each other and of a
much lighter shade and smaller size as compared to the
normal color pattern. There is a significant reduction
in number and a difference in the shade of the head
pattern, as also seen in the ventral pattern. The iris
coloration is also different. Whereas normal specimens
have a brownish color and clear pupils, the anomalous
specimen presents a uniformly black iris, which makes
it impossible to distinguish the pupils from the sclera.
The discovery of this very unusual specimen of
S. ventrimaculatus corroborates the idea expressed
by Sazima and Di-Bernardo (1991) that snakes that
are nocturnal, cryptic, or in any way protected from
visually oriented predators tend to have a greater chance
476
Figure 1. (A) Adult specimen of Sibynomorphus ventrimaculatus showing normal coloration. (B) S. ventrimaculatus specimen with partial albinism (IBSP 85.286). The insets
show the detail of the ventral coloration. Photos by Leandro
Malta Borges.
of survival in the wild compared to individuals with
unusual behaviors or features. If this were not the case,
albinistic individuals might be encountered with greater
frequency.
Acknowledgements. We are very grateful to Elocir Cavalheiro
for discovering and collecting the specimen. We thank Paulo
Sérgio Bernarde for a prior review of the manuscript, Omar
Machado Entiauspe Neto for helping with the translation and the
Instituto Butantan for receiving and accessioning the collected
specimen in its scientific collection.
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Accepted by Zoltán Nagy;
Managing Editor: Hinrich Kaiser