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Biotecnologia Aplicada
Elfos Scientiae
ISSN: 0684-4551
Vol. 13, Num. 1, 1996
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Biotecnologia Aplicada 1996 Volume 3 No. 1
CONFIRMATION OF CUBA CROCODILE HYBRIDS USING DNA THERMAL
PROFILING
S. R. Akkaraju,^1 J. E. Ahlquist,^2 W. McMahan,^3 C. L.
Parkinson^1 and M. H. Perlin^1
^1 Department of Biology, University of Louisville, Louisville,
KY, 40292 USA. ^2 Southeast Fisheries Science Center, Charleston
Laboratory, Charleston, SC 29422 2607, USA. ^3 Herpaquarium,
Louisville Zoo, 1100 Trevilian Way. Louisville, KY 40213,
USA.
Code Number:BA96033
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Introduction
The Cuban crocodile, Crocodylus rhombifer, the most
endangered crocodilian of the New World, has recently been
included in the Species Survival Plan of the American Association
of Zoos and Aquaria (AZA). There is a need to characterize pure
C. rhombifer individuals for captive breeding
purposes and for future reintroductions into the wild. In this
study, second derivative DNA thermal denaturation profiles were
used to confirm C. rhombifer x C acutus and other hybrids
that were identified based on morphological characters and
circumstantial evidence.
One study conducted on yeast mitochondrial DNA used first
derivative DNA thermal denaturation profiles to distinguish two
strains of yeast (1). We have previously used fifth derivative
DNA thermal denaturation profiles to study crocodilian phylogeny.
These analyses resulted in relationships congruent with those of
other molecular phylogenies (2). DNA thermal profiling has
recently been developed to study genetic variation within a
vertebrate species (3).
The application of this technique to conservation problems is
comparable to establishing a new type of DNA fingerprint for the
identification and characterization of endangered individuals.
DNA thermal profiling has several advantages over other molecular
techniques used routinely by conservationists: a) DNA thermal
profile data can be generated in less time and requires very
little preparation: b) this technique circumvents the use of
radioactive probes, gel electrophoresis, elaborate staining
procedures, Southern blots, autoradiography, and PCR: and c) the
cost of materials to run the procedure are quite small.
Methods
Total genomic DNA was extracted from 24 Cuban Crocodile
individuals originating from seven zoos in the US. DNA was melted
in a Gilford Response II spectrophotometer from 60 C to 100 C at
0,1 C increments. Second derivative thermal denaturation profiles
were generated and the temperature corresponding to each peak was
used in a parsimony analysis.
Results and Discussion
The results from parsimony analyses confirmed that five of
the 24 crocodiles were Cuban Crocodile hybrids rather than pure
C. rhombifer individuals. The individuals identified by DNA
thermal profiling were as follows:
TOLEDO ZOO- Two hybrids:
Cuban Crocodile (1/2) X Nile Crocodile (1/2)
One hybrid:
Cuban Crocodile (3/4) X Nile Crocodile (1/4)
BRONX ZOO- One hybrid:
Cuban Crocodile (1/2) X Indian Mugger (1/2)
GLADYS
PORTER ZOO- One hybrid:
Cuban Crocodile (1/2) X American Crocodile (1/2)
Although no new hybrids were identified in this study using DNA
thermal profile data, the fact that expected hybrids could be
confirmed by the method is promising. This suggests that the
method will be useful for such identifications in the future.
Moreover, such profiles can serve in the development of a
database that would eventually be used by zoos for captive
breeding programs, as well as by law enforcement agencies to
monitor the crocodilian skin trade.
1. Bernardi G, Faures M, Piperno G and Slonimski PP. J Mol Biol
1970;48:23.
2. Akkaraju SR, Moody SM and Ahlquist JE. 2nd World
Herpetological Congress. Adelaide, South Australia. Abstract
1993.
3. Akkaraju SR and Ahlquist JE. Midwest Ecology and Evolution
Conference Northern Illinois University. Abstract 1994.
Copyright 1996 Elfos Scientiae
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