Stingrays and the toxicological
implications of their defense
mechanisms
Biology of Toxins - Spring 2009
Presented by: S. Hall, MO. Ishak,
F. Namdar, H. Hayes
•World-famous "Crocodile Hunter" Steve Irwin, known for seeking out and
handling some of the most dangerous animals in existence, died on
September 4, 2006, in a shocking accident with a stingray. Six weeks later,
a stingray jumped into a fishing boat in Florida and stabbed 81-year-old
James Bertakis in the chest.
•News agencies have reported that Irwin's encounter was with an
Australian bull ray, estimated to weigh about 220 pounds (100 kg). Irwin
was snorkeling in about 6 feet (2 meters) of water, filming a new
documentary titled "Ocean's Deadliest" off the coast of Australia. Irwin was
swimming with one of the larger species of rays out there -- Australian bull
rays can be up to 4 feet (1.2 meters) wide and 8 feet (2.4 meters) long
-Julia Layton
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The recent passing away of Steve
Irwin brought about the interest
to research the stingray toxin.
In popular media the true reason
of death was not determined.
The stingray must have been
some how provoked in order for
this sad event to have occurred.
Photo of Irwin's + a croc.
The goal of this presentation is to
further explore the toxin that was
administered from the stingray
and all of its logistics… (i.e.
ADAME)
Photo of Irwin's boat.
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If someone as
knowledgeable about
animals as Steve Irwin
died from a stingray, then
realistically anybody can.
Knowledge of stingrays is
especially important due
to the fact that they are
found in most bodies of
water and can potentially
cause harm to us.
Stingrays are often found in tourist locations
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They are found both in
marine and freshwater
habitats throughout the
world.
Many species are
“euryhaline” capable of
living in waters of a wide
range of salinity.
Most of the river stingrays
of the family
Potamotrygonidae live
permanently in freshwater
and have lost the ability to
survive in marine habitats.
Generally speaking
they can be found in a
variety of different
places and regions
around the globe.
Stingray distribution along Southern US and Mexican coasts.
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Stingrays are unique
elasmobranchs (These fish have
cartilaginous skeletons, hard
teeth and well developed jaws)
which are cousins of the well
known shark.
There are roughly two hundred
species of stingrays in the
scientific order Myliobatiformes.
Pelagic
Two types of stingrays
1) Benthic “bottom”
2) Pelagic “swimming”
Benthic
Hierarchy of Stingray Families and Subtypes
1) Benthic
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Example: Atlantic stingray
◦ Often buried in the sand
◦ Rounded, diamond shaped body
◦ Stingray located at the middle,
lower third of tail
◦ Bottom feeders (worms, clams,
shrimp, crabs, snails)
2) Pelagic
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Example: Spotted Eagle ray
and Manta ray
◦ Active swimmers
◦ Bat-like shape
◦ Stingray located near body, just
behind pelvic fans
◦ Most are bottom feeders
Defensive mechanism:
The “striking” action is
purely defensive ( an
involuntary response)
and not a conscious
decision (or attack).
Benthic:
Stingray located further
away from body.
Making it a more
effective “striking” and
defensive weapon.
Pelagic:
Stingray near base of
tail to discourage
predators from biting
near vital organs.
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Stingray attacks are
defensive. They usually
occur when an
unknowing human steps
on the creature.
When the “wings” of the
stingray are touched, it
thrusts its tail forward,
driving its venomous
spine into the victim.
Benthic stingrays burry themselves and
often go undetected.
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NO….not necessarily.
Dasyatidae
There are two separate families of poisonous
stingrays Dasyatidae and Urolophidae.
Within these two families there are 4 genera
and roughly 35 species which are poisonous
or that pose a threat to humans (out of
about 200 documented species).
Evolutionary biologists have not however,
studied the evolution of venom glands and
envenomation as a distinct subject.
Therefore, it is only possible to speculate
how stingray venom glands and delivery
systems are related to venom
producing functions in more advanced
life forms.
Urolophidae
Fig.1 – shows the basic
anatomical parts of a stingray
Fig 2 – close up of barb that
is found on tail of sting ray
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The sting apparatus is a modified
dermal denticle , with two ventral
grooves filled with venom-producing
tissue.
The venom apparatus is surrounded by
a cell-rich covering, or sheath that also
may produce lesser amounts of venom.
The venom itself is largely a proteinbased toxin that causes great pain in
mammals and may also alter heart rate
and respiration.
Rays vary in size from 10 to 12 inches
to 6 feet in width and most measure at
least 3 feet long. Their tails are often
almost twice as long as their bodies.
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Stingrays contain a
cartilaginous spine
surrounded by a thin
layer of skin.
This skin is called the
integumentary sheath and
covers two ventrolateral
grooves that contain
venom glands.
When the spine
penetrates the victim the
glandular sheath ruptures
to release the venom into
the tissue of interest.
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Dose (mL/kg):
◦ Generally speaking the administered dosage is dependent
upon the size of the stingray in question.
◦ Intra-Venous LD50 of the lyophilized (dried by freezing
in a high vacuum) venom is estimated at 28mg/kg.
Wet sting:
◦ For the most part when a victim is stung by a ray the barb
does in fact contain the ray’s toxin (which would qualify as
a wet sting).
Dry sting:
◦ Since the serotonin in stingray venom produces severe and
immediate onset of local pain, any sting that is relatively
free of pain indicates that no actual envenomation
occurred and the victim endured a “dry” sting.
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A sharp inner barb with a
thin sheath surrounding it
that contains the venom.
When the spine is ejected,
the barb pierces the venom
sac, along with the victim’s
skin, and the poisonous
slime is introduced into the
wound.
The venom contains enzymes
that cause tissue death.
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Breathing difficulty, low blood
pressure, generalized cramps,
inflammation, fainting,
headache, weakness, paralysis,
and bleeding are a short list of
the side effects.
Venom causes tissue necrosis,
especially to muscle and fat.
Even after the apparatus is
removed, pieces of the spine
and membrane, along with
toxin and mucus, can remain,
producing a festering chronic
ulcer and secondary infection if
the wound is not inspected and
de-brided meticulously.
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Orpotrin
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Phosphodiesterases
◦ Vasoconstrictor peptide (causes arteriolar
constriction)
◦ Causes Hydrolysis of phosphodiester bonds in
DNA and RNA
◦ Necrosis and tissue breakdown
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Hyaluronidase
◦ Causes Hydrolysis of hyaluronic acid of extra
cellular matrix (diffusion factor)
◦ Has antigenic properties
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Serotonin
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5’-nucleotidase
◦ Causes severe vasoconstriction. (painful severe
contractions of smooth muscle)
◦ Platelet activation ultimately leading to plug
formation
◦ This is why the victim feels severe pain from the
sting
◦ Causes complete degradation of linear nucleic
acids
◦ Exonuclease- it breaks the last nucleotide in the
end of a polynucleotide
◦ Necrosis and tissue breakdown
Hyaluronidase
Serotonin
Phosphodiesterase
HGGYKPTDK (1002 Da)
Orpotrin
5’-nucleotidase
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The sheath may have been
previously ruptured, leaving
no venom to administer in
the most recent sting.
The sheath failed to
penetrate the wound.
The sheath failed to rupture
and therefore failing to
release the toxins.
The stingray had a broken
spine.
Sea turtle and broken barb from stingray
MJA 2001;175:33-34
Cardiac injuries from
stingray barbs are rare,
even world wide; all but
one have been fatal
(diagram is from the
case that survived
cardiac injury from a
stingray barb)
Stingray barb entered the pericardial sheath causing
cardiac tamponade. Patient recovered fully after
pericardialcentesis.
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The effects of the venom may be local and/or
systemic.
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Local effects include severe pain at the site of
injury, and tissue necrosis.
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5 Systemic effects include nausea, vomiting,
salivation, sweating, respiratory depression, muscle
fasciculations, convulsions, cramping, abdominal
pain, arrhythmias (first-, second-, third- degree
heart block, and asystole), myocardial ischaemia,
and, rarely, death.
Many of the systemic effects have been
documented only in patients with viscous
penetration, and not in those with peripheral
stingray injuries.
Local venom effects are usually more troublesome
in peripheral stab injuries, but if the barb pierces a
vital organ or structure mechanical damage may be
more dangerous than the venom effects.
Ouch!
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Most importantly keep the victim calm!
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Remove sting fragments with gloves to reduce the risk of
injuring your self.
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Wash wound with salt water.
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Induce injured extremity to warm (43-45 C) water for 40 to
90 minutes (venom is thermolabile or is subject to
destruction/decomposition or change in response to heat).
Use analgesics, NSAIDS, local anesthetics, muscle relaxants,
antihistamines, and corticosteroids for pain, itching, and
swelling.
Antibiotics are commonly used to fight infection.
Serotonin
is metabolized to 5-hydroxyindole
acetaldehyde by monoamine oxidase and
excreted through the kidneys into urine.
Phosphodiesterase, 5’nucleotidase, Orpotrin,
and Hyaluronidase are also all excreted through
the kidneys into the urine.
This could pose a problem later on in life in
regards to nephrotoxicity as well as damage to
the bladder possibly leading to cancer.
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Humans are rarely
killed unless the barb
punctures vital
organs, such as the
heart or lungs.
Stingrays main
predators are sharks,
and the barbs are
usually ineffective at
killing.
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Steve Irwin did in fact get stung by a
poisonous stingray, however he most likely
died before the poison took effect on his
body.
The serotonin in the toxin does have many
effects on cardiac tissue but with the time of
death being immediately after the barb was
removed it can be determined that platelet
activation and vasoconstriction leading to
death had yet to have occurred.
The stingray punctured Irwin’s chest and
lodged itself into his heart. The spine was
removed, ultimately causing his death due to
hemorrhaging.
◦ If (Irwin) was conscious he would have been in agony," Dr Fry told the
Reuters news agency.
◦ Dr Fry states, stingray venom was a defensive weapon similar to that
in stonefish, whose poison is generally fatal, but in the stingray's case
the toxin was not lethal. It was the serrated barbs on the stingray's tail
that would have delivered the fatal injury, he said.
◦ "It's not the going in, it's the coming out," Fry said. "They have these
deep serrations which tear and render the flesh as it comes out."
◦ Dr Geoff Isbister, a clinical toxicologist, said that little was known
about stingray venom, but he agreed that it was the physical trauma
associated with the wound that would have killed Irwin.
◦ "What happened to Steve Irwin is like being stabbed in the heart," Dr
Isbister said.
◦ http://www.timesonline.co.uk/tol/news/world/article627862.ece
RIP Steve Irwin
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•http://animals.howstuffworks.com/fish/stingray.htm