Male reproductive behaviour of Naja oxiana (Eichwald, 1831) in captivity, with a case of unilateral hemipenile prolapse

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https://biotaxa.org/hn/article/view/34541

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Introductionntroduction
The male copulatory organ in snakes is the hemipenis;
the separate right and left hemipenis is connected to the
testis of the same side. At rest the hemipenes are pulled
into the tail by a retractor muscle; during copulation only
one hemipenis is erected and inserted into the female’s
cloaca (Kelly, 2002; Funk, 2005; Mitchell and Tully,
2015). Hemipenal erection is the result of engorgement.
with blood (Kelly, 2002; Rosenthal et al., 2008).
Increased androgen levels are considered the main
trigger for mating behaviours in male snakes (Taylor and
DeNardo, 2011). However, Naja oxiana, as well as other
snakes, including garter snakes (genus Thamnophis),
exhibit a dissociated reproductive pattern with low
androgen levels during the mating period (Tam et al.,
1969; Tumkiratiwong et al., 2012; Schořálková et al.,
2017). In N. oxiana, and most other snake species with
dissociated reproduction, the triggers for copulatory
behaviour are not well known.
Cloacal prolapse (CP) is a common reproductive
disorder in reptiles (Rivera, 2008; Alworth et al., 2011),
typically caused by gastrointestinal disease, metabolic
bone disease, or reproductive disorders (Hedley and
Eatwell, 2014). Hemipenile and penile prolapses
(HP and PP) are the most common forms of CP in
reptiles (Hedley and Eatwell, 2014). Some (abnormal)
reproductive behaviours (such as excessive and chronic
mating) are associated with an increased incidence of
HP (Hedley and Eatwell, 2014; Podhade and Harne,,
2014). Two main therapeutic approaches have been
advanced for Wreating HP, namely (1) fixation of theing
hemipenis by suture, or (2) surgical amputation of the
hemipenis (%arten, 2005; Rivera, 2008; Alworth et al.,
2011). Herein we describe HP management by surgical
amputation. Furthermore, we elaborate on possible
underlying behavioural and physiological factors that
likely led to the abnormal or exaggerated mating in this
case.
Herpetology Notes, volume 11: 1061-1064 (2018) (published online on 19 December 2018)
Male reproductive behaviour of Naja oxiana (Eichwald, 1831) in
captivity, with a case of unilateral hemipenile prolapse
Alireza Nasoori1,2, Ali Taghipour3, and Bruce A. Young4,*
1 Graduate School of Veterinary Medicine, Hokkaido
University, Sapporo 060-0818, Japan.
2 Pasteur Institute of Iran, Production and Research Complex,
Biotechnology Processes Developing Center, Karaj
3159915111, Iran.
3 Department of Clinical Sciences, School of Veterinary
Medicine, Islamic Azad University, Karaj Branch, Karaj
31485-313, Iran.
4 Department of Anatomy, Kirksville College of Osteopathic
Medicine, A.T. Still University, Kirksville, MO, 63501,
USA.
* Corresponding author. E-mail: byoung@atsu.edu
Abstract. The Central Asian cobra, Naja oxiana, is a species with an uncertain conservation status that is rarely bred in
captivity. Male N. oxiana exhibit a dissociated breeding pattern, in which mating behaviour coincides with reduced levels of
testosterone; the cues that promote copulatory behaviour in this species are not fully understood. Herein we report a case where
prolonged copulation led to hemipenile prolapse in a specimen of N. oxiana. When the initial therapeutic intervention failed to
relieve the condition the affected hemipenis was amputated, after which the snake successfully recovered. In order to minimize
exaggerated copulatory behaviour we recommend keeping this species in segregated enclosures. A better understanding of the
cues that trigger normal and exaggerated copulatory behaviour in this species would facilitate its captive propagation.
Keywords. Naja oxiana, hemipenile prolapse, copulatory behaviour

Alireza Nasoori et al.
1062
Clinical Findings
Hemipenal prolapse.—Naja oxiana (Fig. 1) is a
terrestrial elapid occurring in the Transcaspian region
from northeast Iran to northern India (Nasoori et
al., 2016). The individual described in this case was
captured in Sabzevar, Khorasan Province, northeastern
Iran (ca. 36°13’N, 57°40’E; Nasoori et al., 2014)..
This area has a desert climate with a yearly average
temperature of 15.6°C. The warmest month is July
(average temperature 30°C), the coldest month is
January (average temperature 0.6°C).
Naja oxiana is a solitary, oviparous species, whose
sexual cycle is poorly known. The captive colony at
the Pasteur Institute of Iran in Karaj, Iran (35°50’N,
50°59’E; colony temperature ca. 26°C), houses 16
individuals (four males, 12 females) that exhibit mating
behaviour and oviposit in July. During one of the mating
episodes on 20 July 2016, we observed that one of the
males engaged in prolonged copulation and thereafter
presented with unilateral hemipenile prolapse (Fig. 2).
We isolated the snake, which was lethargic and
anorectic. For the first four days after isolation, we
used a non-surgical therapeutic approach to promote
the deflation and retraction of the prolapsed hemipenis.
The prolapsed organ was rinsed daily with normal
saline and treated with ointments containing lidocaine,
hydrocortisone, and soluble lubricant (Frye, 1991). At
the end of the therapy period there was no observable
change in the size of the protruded hemipenis, and the
animal did not appear to improve. In order to prevent
the possibility of subsequent necrosis and infection wee
decided to amputate the prolapsed hemipenis.
Anaesthesia and surgery.—Thirty minutes prior to the
procedure, the snake’s head and forebody were pinned
against the substrate using a handling tool fitted with an
expanded pad at the end. A short segment of the cobra’s
mid-body was isolated by hand, so that injections
could be safely administered to the axial muscles. The
animal received a 2.5 mg/kg intramuscular injection
of gentamicin (Gentamicin 5%, DarouPakhsh, Iran) as
prophylaxis, followed by intramuscular injection of 2
mg/kg diazepam (Zepadic, 10 mg/2ml, CaspianTamin,
Iran) for immobilization. Lidocaine hydrochloride (0.2
ml, Lignodic 2%, CaspianTamin, Iran) was injected into
the root, body, and head of the prolapsed hemipenis to
induce local anaesthesia. The prolapsed hemipenis and
the surrounding area were disinfected with povidone
iodine (10%, Iran), followed by a normal saline rinse.
The prolapsed hemipenis was ligated with a non-
absorbable silk 2-0 suture (Supa, Iran) at a distance of
2 mm distal to the root, and amputation was performed
just distal to the ligation. The animal was checked for
bleeding repeatedly immediately after the procedure
and, when none was observed it was returned to its
(sterile) isolation cage.
Recovery.—Daily, the snake was gently pinned (as
described above) and the amputated area was rinsed
with povidone iodine and normal saline, followed by
the application of oxytetracycline spray (OTC, Vetaque,
Iran) to the surgical area. On Day 2 of recovery, 10
mg/kg Enrofloxacin (Hipralona Enro-I, 10%, Hipra,
Spain) and Vitamin B complex (Osve, Iran) were
intramuscularly administered. On Day 3 after the
procedure, the snake raised its head and neck, expanded
its hood, and appeared fully alert to peripheral cues. On
this day the ligature was removed from the base of the
Figure 1. Naja oxiana in life, showing an ovipositing female
(main image) and a close up of the head and neck (insert).
Photos by Alireza Nasoori.

amputated hemipenis without bleeding or complication,
and the snake was judged to have fully recovered.
Discussioniscussion
Treating prolapses.—Amputation of prolapsed
hemipenis is generally recommended, in part, because
it prevents necrosis and subsequent infection (Frye,
1991). Since in snakes the hemipenes are paired, and
do not function in excretion, unilateral amputation of a
prolapsed hemipenis compromises neither urination nor
future copulation (Kelly, 2002; Funk, 2005; Mitchell and
Tully, 2015). In thepresent case,the individual recovered
rapidly after the hemipenectomy, which is consistent
with earlier reports of HP and PP management (Nisbet
et al., 2011; Da Silva et al., 2013; Podhade and Harne,
2014). Nevertheless, treatment and management of CPs
(including PP and HP) are not always promising. About
27% of prolapse cases recur after the prolapsed organ
is physically replaced (with or without an overlying
suture), and a nearly equal percentage of cases end in the
death (or euthanasia) of the animal (+edley and Eatwell,
2014). Given that HPs and PPs are frequently caused
by reproductive behaviours, as with the present case,
understanding the underlying mechanisms that trigger
mating behaviour in snakes could provide insights to
reduce the incidence of CPs.
Reproduction in Central Asian cobras.—Cobras
are seasonal breeders Tam et al., 1969; Lance, 1976;;
Tumkiratiwong et al., 2012) and the N. oxiana group
kept in the serpentarium showed both copulatory
behaviours and laid eggs in July. Sperm in snakes can
stay viable for a long time both in males or (after mating)
in females (Shine, 1977; Rivas and Burghardt, 2005)..
As such, it is uncertain if the July egg clutches were the
result of the observed copulations at the serpentarium
or were fertilized by sperm the females were storing in
their bodies. Sperm storage for periods of several months
have been well documented in snakes (Halpert et al.,
1982) and there are claims of viable sperm being stored
for over five years (e.g., Magnusson, 1979). Male cobras
typically have postnuptial (or Type II of Lance, 1998)
reproduction cycles (Taylor and DeNardo, 2011), which
means they initiate spermatogenesis months before
mating, and store spermatoza in their vas deference (or
epididymis) before copulation (Lofts et al., 1966; Tam
et al., 1969; Tumkiratiwong et al., 2012). In vertebrates,
including reptiles, androgens are considered a key
trigger for male courtship and copulatory behaviours
(Schořálková et al., 2017). In some species, including
cobras, the level of testosterone is not high at the time
of mating (dissociated reproduction; Tam et al., 1969;
Tumkiratiwong et al., 2012; Schořálková et al., 2017). In
these forms it remains unclear what cues are triggering
mating behaviour.
Prolonged copulation is an evolutionary strategy to
increase mating success in male snakes through sperm
competition (Shine, 2003). However, the hemipenal
trauma during copulation can cause pathologic
conditions such as HP or PP (Raiti, 1995). It is
unknown whether or not fluctuations in testosterone
(or other androgens) play a role in either the normal,
and abnormally prolonged, copulatory response in male
snakes with dissociated breeding pattern. Snakes are
not usually regarded as territorial reptiles (Rivas and
Burghardt, 2005); nevertheless, male-male combat in N.
oxiana has been reported before (Shine, 1994; Nasoori,
2014). Translocation of snakes is another factor that
increases stress +eiken et al., 2016). Thus, keeping
these snakes in captive situation together in a group
can lead to injurious conflicts, so we advise keeping N.
oxiana in segregated enclosures.
Male reproductive behaviour of Naja oxiana in captivity 1063
Figure 2. Male Naja oxiana showing a prolapsed hemipenis in two views. Photos by Alireza Nasoori.

Accepted by Hinrich Kaiser
Acknowledgment. We thank the Serpentarium of the Pasteur
Institute for their cooperation and assistance.
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