Toxins in amphibians & reptiles
Amphibians & reptiles: paraphyletic group
Chapter 1: Introduction & overview of poisonous/venomous taxa
Why study it?
The study of animal toxins is beneficial for several biological and applied science fields =>
• Applied knowledge in medicine, physiology of animals can interact with other
animals’ physiology, biochemistry is important bcs toxins are molecules, often
proteins, so a basic knowledge is needed. Also, ethology, animal behavior (adapted
behaviors to toxins), immunology: for making antivenoms,
…
• Fields: Animal physiology, biochemistry, cellular biology,
ecology, ethology, evolutionary biology, immunology,
molecular genetics, molecular phylogenetics, taxonomy,
organic chemistry, pharmacology, medicine, ...
... and the study of animal toxins itself benefits from knowledge in
these fields
1.1 Some terminology to start with:
1.1.1. What is a toxin?
goes back to renaissance period
Theophrastus of Hohenheim (Paracelsus) (1493 – 1541):
• alchemist, studying different aspects of life, including toxins: what defines a toxin,
also, a theologian, etc
• better known as Paracelsus (scientists often choose Latinized names)
• “All things are poison, and nothing is without poison. Only the dose makes a thing
not to be a poison.”
• very true, even water can be poison, it depends of dose when bucket of water it
becomes a toxin, => grey zone for all molecules that exist that can be toxic to an
extent (molecules, things, …)
Wikipedia defenitions
What is a toxin What is a Poison?
“A naturally occurring organic poison “Any chemical substance that is harmful or
produced by metabolic activities of living lethal to living organisms.”
cells or organisms.”
synonymize toxin as poison => not true!! fair enough
very unscientific
These definitions emphasize the potential negative effect of a substance!
• They say basically: must be causing damage, not necessarily lethal
These definitions differ from what is currently used in scientific literature
,Ecological definition (After Fry et al. Annu Rev Genomics Hum Genet. 2009):
“A molecule used by one organism to cause a biochemical effect in another in the function
of predation, defense, or competition.”
This definition does not put any restrictions on :
• The range of taxa that produce toxins or against which the toxins are used
• the origin of the toxin (obtained exogenously or produced endogenously)
• the type or severity of the biochemical effect in the “receiving” organism
This definition emphasizes the functional value of a molecule
just says something about the ecological purpose: predation, defense, competition
We also include here vb the saliva of mosquitoes (saliva that has blood-thinning agents so
they can drink longer); these proteins are very similar to proteins in snake venom.
“... in function of predation, defense or competition” => Yes, also competition
Crossland & Shine Biol Lett 2011:
Cane toad => ecological disaster in Australia
• Bufonidae, native to the Neotropics (Central and South
America), native to the Neotropics (Central and South
America)
• Introduced as pest control (beetle in sugar canes)
• Very poisonous: alkaloids & steroids in skin secretions
• Predators (snakes, crocodiles…) to similar-looking prey in
Australia were naïve to these toxins => no resistance => a
lot of damage
• Competition against overpopulations, control of own population: Tadpoles produce
toxins, release them in the water => inhibiting the development of their own species’
younger individuals (impact on egg hatching)
Cane toad tadpoles produce waterborne chemical cues that suppress the viability
of conspecifics encountering those cues during embryonic development. Brief
(72 h) exposure to these cues in the egg and post-hatching phases massively
reduced rates of survival and growth of larvae. Body sizes at metamorphosis
(about three weeks later) were almost twice as large in control larvae as in
tadpole-exposed larvae.
Platypus also has toxins to fight each other (intraspecific function of toxins)
Revised definition (Nelsen et al. Biol Rev. 2014):
Biological toxin: A substance produced by a living organism that can cause dose-dependent
pathophysiological injury to itself or another living organism; sometimes called a biotoxin
• What we focus on in this course
• Paracelsus argument included
• “to itself” => suicide toxins, in bacteria, they can kill themselves to avoid infection by
pathogens for the whole population
,Environmental toxin: a naturally occurring substance in the environment that is not
produced by an organism but can cause dose-dependent pathophysiological injury to a living
organism. E.g.: arsenic, mercury, lead.
• vb heavy metals (mercury, lead in soil), methane that comes out of pools
Anthropogenic toxin (or “toxicant”): A substance produced by humans that does not
otherwise occur in the environment, which can cause dose- dependent pathophysiological
injury to a living organism. E.g.: dichlorodiphenyltrichloroethane (DDT), dioxin,
polychlorinated biphenyls (PCBs).
• An anthropogenic toxin is a subset of environmental toxins in a sense (we are also
organisms.
1.1.2. What is a bioactive molecule?
A term commonly used in the field of pharmacology:
milder term, does not focus on ecological purpose: toxins, drugs,… focuses on biochemistry
“A molecule with a biological effect on living matter (cells, tissues or organisms)”
! Note that this definition does not specify whether this effect is beneficial or adverse.
=> toxins are bioactive molecules, but drugs are too.
! Bioactivity is mostly used in terms of the desired effect of a potential drug candidate.
pharmacologist: a scientist that investigate natural occurring things to turn them into drug
designs
toxin that slows down hart => useful for people with bradycardia (too slow heart rate)
• Drugs are also bioactive molecules
1.1.3. Toxicology vs. Toxicology
Toxicology: The scientific discipline dealing with the adverse effects of chemicals on living
organisms, communities, and ecosystems. It is the study of symptoms, mechanisms,
treatments, and detection of poisoning.
if you study mercury in a landscape, you are a toxicologist
Investigate biological toxins produced by animals regardless of wich aspect (behavior,) you
are studying in toxicology
Toxinology:
• “The scientific discipline dealing with microbial, plant and animal venoms, poisons,
and toxins.” (Prof. Dietrich Mebs, IST)
• “The science of toxic substances produced by or accumulated in living organisms,
their properties, and their biological significance for the organisms involved.” (Prof.
Jurg Meier, Editor of Toxicon)
=> The study of biological toxins and all their aspects (pathophysiology, treatment, ecology,
evolution)
, 1.1.4. Venom vs. poison
…. (nog veel meer references)
A lot of scientists look at the way of transmission: injection as criteria to say venom,
introduced through contact (& absorption): poison
• active (venom: bee stinging you) and passive (poison, vb sea urchin you must step on
it to ‘inject’)
• Passive is mostly related to defense
a lot of diversity of definitions that exist in this field
(Fry et al. Annu Rev Genomics Hum Genet. 2009)
venom poison
toxin or mixture thereof used by an animal toxin or mixture thereof that is passively
and injected into the circulatory system administered through epithelia (e.g. skin,
(e.g. blood stream or lymphatic system) of gills, lungs, intestines) by absorption,
another animal, often by means of a ingestion or inhalation.
specialized venom delivery structure (e.g.
fangs, beaks, spines, stinger)
• Venoms may have a predatory and/or • Poisons in biology mostly have a
defensive function defensive function,
• Derived words: “venomous”, • derived words: “poisonous”,
“envenomation”, “venom glands” - ! “poisoning”, “poison glands”
“venom” and “venomous” only apply • ! Plants are called poisonous, not
to animals venomous, even if they use spines to
inject the toxins.
toxic animal must bite or sting you You must bite the toxic animal
Amphibians & reptiles: paraphyletic group
Chapter 1: Introduction & overview of poisonous/venomous taxa
Why study it?
The study of animal toxins is beneficial for several biological and applied science fields =>
• Applied knowledge in medicine, physiology of animals can interact with other
animals’ physiology, biochemistry is important bcs toxins are molecules, often
proteins, so a basic knowledge is needed. Also, ethology, animal behavior (adapted
behaviors to toxins), immunology: for making antivenoms,
…
• Fields: Animal physiology, biochemistry, cellular biology,
ecology, ethology, evolutionary biology, immunology,
molecular genetics, molecular phylogenetics, taxonomy,
organic chemistry, pharmacology, medicine, ...
... and the study of animal toxins itself benefits from knowledge in
these fields
1.1 Some terminology to start with:
1.1.1. What is a toxin?
goes back to renaissance period
Theophrastus of Hohenheim (Paracelsus) (1493 – 1541):
• alchemist, studying different aspects of life, including toxins: what defines a toxin,
also, a theologian, etc
• better known as Paracelsus (scientists often choose Latinized names)
• “All things are poison, and nothing is without poison. Only the dose makes a thing
not to be a poison.”
• very true, even water can be poison, it depends of dose when bucket of water it
becomes a toxin, => grey zone for all molecules that exist that can be toxic to an
extent (molecules, things, …)
Wikipedia defenitions
What is a toxin What is a Poison?
“A naturally occurring organic poison “Any chemical substance that is harmful or
produced by metabolic activities of living lethal to living organisms.”
cells or organisms.”
synonymize toxin as poison => not true!! fair enough
very unscientific
These definitions emphasize the potential negative effect of a substance!
• They say basically: must be causing damage, not necessarily lethal
These definitions differ from what is currently used in scientific literature
,Ecological definition (After Fry et al. Annu Rev Genomics Hum Genet. 2009):
“A molecule used by one organism to cause a biochemical effect in another in the function
of predation, defense, or competition.”
This definition does not put any restrictions on :
• The range of taxa that produce toxins or against which the toxins are used
• the origin of the toxin (obtained exogenously or produced endogenously)
• the type or severity of the biochemical effect in the “receiving” organism
This definition emphasizes the functional value of a molecule
just says something about the ecological purpose: predation, defense, competition
We also include here vb the saliva of mosquitoes (saliva that has blood-thinning agents so
they can drink longer); these proteins are very similar to proteins in snake venom.
“... in function of predation, defense or competition” => Yes, also competition
Crossland & Shine Biol Lett 2011:
Cane toad => ecological disaster in Australia
• Bufonidae, native to the Neotropics (Central and South
America), native to the Neotropics (Central and South
America)
• Introduced as pest control (beetle in sugar canes)
• Very poisonous: alkaloids & steroids in skin secretions
• Predators (snakes, crocodiles…) to similar-looking prey in
Australia were naïve to these toxins => no resistance => a
lot of damage
• Competition against overpopulations, control of own population: Tadpoles produce
toxins, release them in the water => inhibiting the development of their own species’
younger individuals (impact on egg hatching)
Cane toad tadpoles produce waterborne chemical cues that suppress the viability
of conspecifics encountering those cues during embryonic development. Brief
(72 h) exposure to these cues in the egg and post-hatching phases massively
reduced rates of survival and growth of larvae. Body sizes at metamorphosis
(about three weeks later) were almost twice as large in control larvae as in
tadpole-exposed larvae.
Platypus also has toxins to fight each other (intraspecific function of toxins)
Revised definition (Nelsen et al. Biol Rev. 2014):
Biological toxin: A substance produced by a living organism that can cause dose-dependent
pathophysiological injury to itself or another living organism; sometimes called a biotoxin
• What we focus on in this course
• Paracelsus argument included
• “to itself” => suicide toxins, in bacteria, they can kill themselves to avoid infection by
pathogens for the whole population
,Environmental toxin: a naturally occurring substance in the environment that is not
produced by an organism but can cause dose-dependent pathophysiological injury to a living
organism. E.g.: arsenic, mercury, lead.
• vb heavy metals (mercury, lead in soil), methane that comes out of pools
Anthropogenic toxin (or “toxicant”): A substance produced by humans that does not
otherwise occur in the environment, which can cause dose- dependent pathophysiological
injury to a living organism. E.g.: dichlorodiphenyltrichloroethane (DDT), dioxin,
polychlorinated biphenyls (PCBs).
• An anthropogenic toxin is a subset of environmental toxins in a sense (we are also
organisms.
1.1.2. What is a bioactive molecule?
A term commonly used in the field of pharmacology:
milder term, does not focus on ecological purpose: toxins, drugs,… focuses on biochemistry
“A molecule with a biological effect on living matter (cells, tissues or organisms)”
! Note that this definition does not specify whether this effect is beneficial or adverse.
=> toxins are bioactive molecules, but drugs are too.
! Bioactivity is mostly used in terms of the desired effect of a potential drug candidate.
pharmacologist: a scientist that investigate natural occurring things to turn them into drug
designs
toxin that slows down hart => useful for people with bradycardia (too slow heart rate)
• Drugs are also bioactive molecules
1.1.3. Toxicology vs. Toxicology
Toxicology: The scientific discipline dealing with the adverse effects of chemicals on living
organisms, communities, and ecosystems. It is the study of symptoms, mechanisms,
treatments, and detection of poisoning.
if you study mercury in a landscape, you are a toxicologist
Investigate biological toxins produced by animals regardless of wich aspect (behavior,) you
are studying in toxicology
Toxinology:
• “The scientific discipline dealing with microbial, plant and animal venoms, poisons,
and toxins.” (Prof. Dietrich Mebs, IST)
• “The science of toxic substances produced by or accumulated in living organisms,
their properties, and their biological significance for the organisms involved.” (Prof.
Jurg Meier, Editor of Toxicon)
=> The study of biological toxins and all their aspects (pathophysiology, treatment, ecology,
evolution)
, 1.1.4. Venom vs. poison
…. (nog veel meer references)
A lot of scientists look at the way of transmission: injection as criteria to say venom,
introduced through contact (& absorption): poison
• active (venom: bee stinging you) and passive (poison, vb sea urchin you must step on
it to ‘inject’)
• Passive is mostly related to defense
a lot of diversity of definitions that exist in this field
(Fry et al. Annu Rev Genomics Hum Genet. 2009)
venom poison
toxin or mixture thereof used by an animal toxin or mixture thereof that is passively
and injected into the circulatory system administered through epithelia (e.g. skin,
(e.g. blood stream or lymphatic system) of gills, lungs, intestines) by absorption,
another animal, often by means of a ingestion or inhalation.
specialized venom delivery structure (e.g.
fangs, beaks, spines, stinger)
• Venoms may have a predatory and/or • Poisons in biology mostly have a
defensive function defensive function,
• Derived words: “venomous”, • derived words: “poisonous”,
“envenomation”, “venom glands” - ! “poisoning”, “poison glands”
“venom” and “venomous” only apply • ! Plants are called poisonous, not
to animals venomous, even if they use spines to
inject the toxins.
toxic animal must bite or sting you You must bite the toxic animal
