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Eunectes murinus (Green Anaconda) Reproduction / Facultative Parthenogenesis

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Herpetological Review 47(1), 2016
HERPETOCULTURE 73
SQUAMATA — SNAKES
EUNECTES MURINUS (Green Anaconda). REPRODUCTION /
FACULTATIVE PARTHENOGENESIS. Obligate parthenogenesis
is well documented in at least 25 species of lizards, but only a
single snake species, Indotyphlops (formerly Ramphotyphlops)
braminus (Vrijenhoek et al. 1989. In Dawley and Bogert [eds.],
Evolution and Ecology of Unisexual Vertebrates, pp. 19–23
Bulletin 466, New York State Museum, Albany, New York).
Occasional cases of facultative parthenogenesis have also now
been documented in an increasing number of otherwise sexual
snake species, including Python bivittatus (Groot et al. 2003.
Heredity 90:130–135); Boa constrictor (Booth et al. 2011. Biol.
Lett. 7:253–256); Epicrates cenchria (Kinney et al. 2013. 2–13.
Zoo Biol. 32:172–176); E. maurus (Booth et al. 2011. J. Hered.
102[6]:759–763); Acrochordus arafurae (Magnusson 1979. Copeia
1979[4]:744–745; Dubach et al. 1997. Herpetol. Nat. Hist. 5[1]:11–
18); Thamnophis couchii (Germano and Smith 2010. Southwest.
Nat. 55[2]:280–282); T. elegans vagrans and T. marcianus (Schuett
et al. 1997. Herpetol. Nat. Hist. 5[1]:1–10); Agkistrodon contortrix
(Booth and Schuett 2011. Biol. J. Linn. Soc. 104:934–942); Crotalus
durrisus unicolor and C. horridus (Schuett et al., op. cit.). We here
report the first documented case of facultative parthenogenesis
in Eunectes murinus.
On 11 August 2014, a female E. murinus (SVL = 2462; total
length = 2832 mm), held in the collection at Mark O’Shea’s
Reptile World, Discovery Trail, West Midland Safari Park (WMSP),
Bewdley, Worcestershire, United Kingdom, gave birth to three
live and five dead neonates, all confirmed as females (SVL = 600–
685 mm; total length = 715–795 mm). The female has been in
the collection since 27 March 2009 (5 years, 4.5 months) during
which time it has been maintained solely in the company of a
single larger (4.0 m+) female. Prior to its arrival at WMSP, as an
immature subadult, the female was maintained in a private
collection, also in isolation from any male, thereby ruling out the
possibility of long-term sperm-storage being responsible for the
birth.
The small size of the litter, the high mortality, and its all-
female composition, are all compatible with other cases of boid
parthenogenesis (Booth et al. 2011. J. Hered. 102[6]:759–763;
Kinney et al., op. cit.). Tissue and blood samples were taken
from all live and dead neonates, and the adult female, as part of
regular veterinary screening requirements, and surplus samples
were shipped to Warren Booth, University of Tulsa, Oklahoma,
USA. The dead neonates were accessioned into the Natural
History Museum, London (NHMUK 2013.486–490, field nos.
MOS 3500–04). The three live neonates were maintained in the
WMSP collection, with the subsequent death of the weakest
on 7 January 2015. Post-mortem gross and histopathological
examination of this individual identified bacterial and fungal
pathogens and reduced body condition; the carcass was not
retained. At the time of writing, almost 15 months post-birth, the
remaining two neonates are feeding well and thriving.
MARK O’SHEA (e-mail: oshea@markoshea.info), STEVE SLATER, RE-
BECCA SCOTT, Discovery Trail, West Midland Safari Park, Bewdley, Worces-
tershire, DY12 ILF, United Kingdom; SARAH SMITH, Veterinary, WMSP,
Bewdley, Worcestershire, DY12 ILF, United Kingdom; KATIE McDONALD,
Research, WMSP, Bewdley, Worcestershire, DY12 ILF, United Kingdom; BOB
LAWRENCE, Development, WMSP, Bewdley, Worcestershire, DY12 ILF,
United Kingdom; MARIE KUBIAK, Manor Vets, 373 Hagley Road, Birming-
ham, West Midlands, B17 8DL, United Kingdom.
... Here we report a case of parthenogenetic reproduction in a long-term isolated female green anaconda Eunectes murinus, validated by DNA evidence using microsatellite markers. Although parthenogenesis has been reported before in E. murinus [17], our findings are the first to definitively report facultative parthenogenesis in Eunectes based on DNA analysis. ...
... However, they had no obvious morphological anomalies. A recent suspected case of parthenogenesis in Eunectes murinus has produced viable offspring, but uncertainty remains on the status of this case as no DNA evidence in support of the parthenogenesis was included [17]. DNA-validated parthenogenetic offspring were viable in the closely related Boidae, Boa constrictor, Epicrates maurus and Epicrates cenchria cenchria [5][6][7]. ...
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Full-text available
In reptiles, the mode of reproduction is typically sexual. However, facultative parthenogenesis occurs in some Squamata, such as Komodo dragon (Varanus komodoensis) and Burmese python (Python bivittatus). Here, we report facultative parthenogenesis in the green anaconda (Eunectes murinus). We found two fully developed female neonates and 17 undeveloped eggs in the oviduct of a female anaconda isolated from other individuals for eight years and two months at Ueno Zoo, Japan. To clarify the zygosity of the neonates, we analyzed 18 microsatellite markers of which 16 were informative. We observed only maternal alleles and no paternal alleles for all 16 markers. To examine the possibility of the long-term sperm storage, we estimated allele frequencies in a putative parental stock by genotyping five unrelated founders. If all founders, including the mother, are originated from a single Mendelian population, then the probability that the neonates were produced by sexual reproduction with an unrelated male via long-term sperm storage was infinitesimally small (2.31E-32 per clutch). We also examined samples from two additional offspring that the mother delivered eight years before her death. We consistently observed paternal alleles in these elder offspring, indicating that the mother had switched from sexual reproduction to asexual reproduction during the eight years of isolation. This is the first case of parthenogenesis in Eunectes to be validated by DNA analysis, and suggests that facultative parthenogenesis is widespread in the Boidae.
Article
Snakes have increasingly been bred as pets around the world. Few studies have addressed the reproduction of boid snakes, and no study has addressed their reproductive cycles in captivity. Thus, this paper describes the reproductive aspects of Brazilian boids in captivity. We used ultrasonography to characterize the reproductive cycle of four boid species in captivity in the Southern Hemisphere: the anaconda (Eunectes murinus), the red-tailed boa (Boa constrictor constrictor), the Amazon tree boa (Corallus hortulanus), and the rainbow boa (Epicrates cenchria). Nonvitellogenic follicles occurred from January to December in anaconda and red-tailed boa and for a shorter period from September to February in Amazon tree boa and from January to May in rainbow boa. Vitellogenesis occurred from late June to late March in E. murinus in year-round (12 months), from March to March in Amazon tree boa, from late September to late March in red-tailed boa, and from late March to late September in rainbow boa. Mating occurred from late March to late September in red-tailed boa and rainbow boa and from late September to late March in Amazon tree boa. No mating was observed in anacondas, but a female probably underwent parthenogenesis. Births occurred in July in anaconda and in March to July in Amazon tree boa and from December to March in red-tailed boa and rainbow boa. In males, increases in testicular size were associated with the mating season. Ultrasonography proved to be a safe and noninvasive technique to study the reproductive cycle of giant snakes in captivity. HIGHLIGHTS • A method of diagnosing the reproductive phases that determined an ovulatory and gestational development reproductive standard. • In males was possible to relate the size of the testicles with the reproductive season. • Ultrasound examination showed an easy and inexpensive method of diagnosis.
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