Two cases of polydactyly in the Italian crested newt, Triturus carnifex

Herpetology Notes, volume 7: 477-478 (2014) (published online on 25 August 2014)
Two cases of polydactyly in the Italian crested newt,
Triturus carnifex
Francesca Gatti1 and Marco Sannolo2*
Polydactyly can be defined as an increased number
of metatarsal and polyphalangy as the duplication of
the phalangeal sets (Rothschild et al., 2012). Several
cases of both polydactyly and polyphalangy have been
described for Triturus cristatus (Arntzen and Wallis,
1991; Jarvis, 2011). However, to our knowledge, only
one report of such abnormalities has been published for
the Italian populations of Triturus carnifex (Zaffaroni et
al., 1996).
In the contest of a long-term study on the demography
of a population of Triturus carnifex in the Groane
Regional Park (Lombardy, Italy), we captured-markedrecaptured the individuals of a pond. The site is a natural
ecosystem, the pond has an area of approximately 400
m2 (but it is subjected to wide fluctuations), and the
plant association is typical for the marsh ecosystems in
the temperate plain areas in northern Italy (Gariboldi
L. pers. comm.). The moor surrounding the pond is
dominated by Molinia sp. and Calluna vulgaris as
herbaceous plants and by Betula pendula and Quercus
robur as trees. The edge of the pond is characterized
by Juncus sp., Iris pseudacorus, Ranunculus flammula
and Veronica scutellata. In the pond can be founded
Typha latifolia, Utricularia australis, Glyceria fluitans,
Ludwigia palustris and Juncus sp.
During the 2014 sessions of capture, we found two
individuals that were characterized by abnormalities
in the limbs. To our knowledge, this is the first report
of polydactyly in Triturus carnifex for the Groane
Regional Park.
The two individuals were both males in apparent
wealthy and tonic condition. The first, captured on
26 April 2014, was long 6.74 cm SVL (snout-to-vent
length) and 4.25 cm in tail length (TL), for a total length
of 10.99 cm. The second male was captured on 17 May
2014 and was long 6.67 cm SVL and 4.80 cm TL, for a
total length of 11.47 cm. In both individuals the anomaly
occurred on the anterior left limb. The malformation
Via Garibaldi 34, 20090 Vimodrone, Milano, Italy
Via Petrarca 35, 20093 Cologno Monzese, Milano, Italy
* Corresponding author; e-mail: marco.sannolo@gmail.com
1
2
consisted in the presence of two sets of reduced and
partially fused digits (Fig. 1 and 2)
In the dorsal view, the first individual showed the first
and the second finger reduced and more swollen than
the right ones. The third and the fourth finger were also
reduced and, moreover, fused together. The second set
of fingers developed from the external part of the hand
and was kept laterally or ventrally respect to the first
four fingers. The second set was composed by four digits
that were similar in shape and relative position to the
healthy ones of the right hand. The left forearm showed
and enlargement, probably caused by the duplication of
part of the soft and hard tissues that sustained the two
sets of fingers. Interestingly, of the two left hands, the
internal-abnormal one, well visible in the dorsal vision,
was the mobile and apparently the unique used.
The second individual was rather similar to the first
one in body size and the abnormal limb was also the
left one. However, this male was characterized by both
polydactyly and polyphalangy. Dorsally, it showed four
digits that were shorten and more clustered than those
of the right hand. The second set of digits developed
partially laterally and then ventrally with respect to the
first one. The first digit of the second set appeared as a
fifth finger of the first hand.
Data about the frequency of this kind of abnormalities
are scanty, mainly because there is the need of a long term
capture-mark-recapture study to estimate the population
dimension and then to assess the abnormalities
frequency. As part of a long term study in the described
area, we captured 336 newts, and therefore the
observed abnormality frequency was 0.0059 (0.59 %).
Abnormalities frequency below 1% are considered rare,
while frequency ranging between 1-5% is considered
normal by Blaustein and Johnson (2003). Amphibian
malformations arisen as result of environmental factors,
UV-B radiations, parasite loads, chemical pollution and
genetic mutation (Blaustein and Johnson, 2003). There
is also the possibility that predation by dragonfly nimphs
caused similar deformations (Session and Ballengée,
2010). The studied site was natural and undisturbed, nor
did we have data about environmental pollution in the
478
area. However the site is situated in the Groane Regional
Park, a partially anthropized area, with many urban
settlements and several highways relatively nearby the
pond. In conclusion, we have no data to suppose some
kind of pollution either of air or water that could have
caused the observed abnormalities and therefore we
suppose that probably the observed abnormalities were
caused by predation attempts or fall into the normal
mutation frequency.
Acknowledgment. This results from part of a long term study on
the demography of Triturus carnifex conducted in respect of the
current Italian laws (Prot. 0008880/PNM). We would thank Dr.
Luca Gariboldi for the assistance with the characterization of the
pond’s vegetation. Patri gently revised and commented an early
draft of the manuscript.
Francesca Gatti & Marco Sannolo
References
Arntzen, J.W., Wallis, G.P. (1991): Restricted gene flow in a moving
hybrid zone of the newts Triturus cristatus and T. Marmoratus in
western France. Evolution 45: 805-826.
Blaustein, A.R., Johnson, P.T.J. (2003): The complexity of deformed
amphibians. Frontiers in Ecology and the Environment 1: 8794.
Jarvis, L.E. (2011): Triturus cristatus (great crested newt).
Malformation. Herpetological Bulletin 117: 40-41.
Rothschild, B.M., Schultze, H.P., Pellegrino, R. (2012):
Herpetological osteopathology. Annotated bibliography of
amphibians and reptiles, New York, Springer.
Session, S.K., Ballengée, B. (2010): Explanation for missing limbs
in deformed amphibians. Journal of Experimental Biology 312:
770-779.
Zaffaroni, N.P., Arias, E., Lombardi, S., Zavanella, T. (1996):
Natural variation in the appendicular skeleton of Triturus
carnifex (Amphibia: Salamandridae). Journal of Morphology
230: 167-175.
Figure 1. The first male captured that displayed an anomaly on the anterior left limb.
Figure 2. The second male captured, also displayed an anomaly on the anterior left limb.
Accepted by Zoltán Nagy;
Managing Editor: Philip de Pous