poison and venom - Benjamin J. Gibson

Figure 2. Secondary defenses (poison and venom) across different taxonomic fish groups.
Poisonous species: (A) White-spotted Puffer fish (Arothron hispidus), (B) Freckled
porcupine fish (Diodon holocanthus) and (C) Longhorn Cowfish (Lactoria cornuta).
Venomous species: (D) Spotted eagle ray (Aetobatus narinari), (E) Lionfish (Pterois
volitans) and (F) Pacific spotted scorpionfish (Scorpaena mystes).
Many organisms that have trouble defending themselves have evolved anatomies that provide the defenses
needed to ward off predators. This can take the forms of many different types, whether it is spines, or a rapid
situational change in body size, or even camouflage (crypsis or countershading). This isn’t sufficient however, and
many organisms have to utilize chemical defenses such as toxins. These organisms are either poisonous or
venomous; poison and venom are commonly used interchangeably and are confused when describing the type of
chemical defense. Poisonous organisms are those that are toxic once ingested or touched, while venomous
organisms inject their toxin through some type of conduit (Russell, 1965). Common characteristics that contrast the
two types of toxins include their method of creation, where the toxin is contained, and how it is used. Poison
usually originates both directly and indirectly from the prey of the organism, and the synthesized toxins are stored
in the body tissues; poison is transferable cutaneously which is why they are toxic via touch. The venomous
organisms create their toxins themselves, storing them in specialized glands near tubular-like structures, serving as
a conduit for the transfer of venom; in the case of the species being discussed, these glands are located near
pectoral or dorsal fins. In general, poison is used as a defense against predators, while venom is typically used
against both predators and prey (Nelsen et al., 2014). However, in marine organisms, this is rarely the case, and
both poison and venom are strictly used for defense. Some marine organisms that are considered poisonous include members of families Ostraciidae (boxfish
and cowfish), and Tetraodontidae (Puffer fish), and Diodontidae (Porcupine fish). These are all a part of the same
order Tetraodontiformes. A member of the family Tetraodontidae, the white spotted puffer fish (Arothron hispidus),
contains tetrodotoxin, which makes the species poisonous (fig. 2A). There has been a long debate on whether or not
the tetrodotoxin is endogenous or exogenous. The evidence for the exogeneity of tetrodotoxin is extensive; It is
believed that the toxin is produced by several bacteria species including Microbacterium arabinogalactanolyticum,
Serratia marcescens, Vibrio alginolyticus and Bacillus spp. and this is supported by the existence of cultured puffer
fish that are free of tetrodotoxin, indicating that they cannot create it on their own (Yu et al., 2004; Wu et al., 2005;
Matsui et al., 1982). This has been challenged by a study that artificially fertilized an egg of a species of puffer fish
and found that toxicity levels increased with growth (Matsumura, 1998). Another poisonous species is actually a
closely related species to the white spotted puffer fish; the freckled porcupinefish (Diodon holocanthus) (fig. 2B).
This species, like the white spotted pufferfish, is thought to sequester tetrodotoxin from its prey. One species of
cowfish, the longhorn cowfish, (Lactoria cornuta), is a type of boxfish with two spines protruding from its head
(fig. 2C). The longhorn cowfish have poisonous flesh and can release ostracitoxin into the surrounding water in
response to stress caused by sudden movement, bright light and loud sounds (Khan et al., 2013). Venomous species include a representative from family Mylobatidae, the spotted eagle ray (Aetobatus
narinari), and members of the family Scorpaenidae, the lionfish (Pterois volitans) and the pacific spotted
scorpionfish (Scorpaena mystes). These organisms are venomous because they have spines, which transfer venom
through a stimulus. The spotted eagle ray has a few short spines behind the dorsal fin (fig. 2D). These spines have a
barbed tip and ventrolateral grooves, and on these ventrolateral grooves is an epidermal covering containing
venom-secreting cells (Bester, 2008). Envenomation occurs when the barb is driven into the body of the victim,
effectively rupturing the epidermal covering of the spine, releasing the venom into the tissue (Kumar et al., 2011).
Lionfish has several venom glands along its fin spines and when stimulated with pressure, it releases venom
through the spines (Vetrano et al., 2002) (fig. 2E). This is similar to the pacific spotted scorpionfish, which injects
venom through its sharp spines seated near the dorsal fin. This usually occurs when pressure is placed on it,
stimulating the spines and forcing venom to flow from the venom gland through the spine (Pryor, 2008) (fig. 2F). All of these organisms have one thing in common: these poisons and venoms appear to be contingency
plans, or last-resort defenses, since their morphological features indicate other deterrents that should stop the
majority of predatory attacks. The longhorn cowfish have spines, both the white spotted pufferfish and the freckled
porcupinefish have the ability to become larger by blowing themselves up, the porcupinefish also has large spines
that erect as the body increases in size, the pacific spotted scorpionfish have cryptic coloration, lionfish have their
aposematic coloration, and spotted eagle rays have their countershading, which is a type of camouflage. It can be
speculated that this is indicative of the amount of energy it must take to produce or sequester these toxins. More
than 200 species of marine fish are venomous or at least suspected to be venomous, and the vast majority of these
are nonmigratory, slow-moving fish that inhabit often protected coastal waters (Maretic, 1998). It has been
suggested that the tendency to be inactive has been linked to the evolution of venom conduits (Cameron and
Endean, 1973). The toxin that is seen in the members of Tetraodontiformes, tetrodotoxin, is named after the order,
which indicates that the majority of the species in the order contains the ability to sequester the toxin from the
bacteria (Yasumato et al., 1986). For this reason, it can be concluded that because these organisms are relatively
slow moving individuals, they need more than one way to get away, which in these organisms, are toxins. References
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Bester, Cathleen. 2008. Ichthyology at the Florida Museum of Natural History. Florida Museum of Natural
History. Web. Feb 11 2015.
• 
Cameron AM, Endean R. 1973. Epidermal secretions and the evolution of venom glands in fishes. Toxicon.
11: 401-406
• 
Khan SK, Siddique MAM, Haque MA. 2013. New record of the longhorn cowfish Lactoria cornuta
(Linnaeus 1758) from inshore waters of the Bay of Bengal, Bangladesh. Zool. Ecol. 23(1): 88-90.
• 
Kumar KJ, Vennila R, Kanchana S, Arumugam M, Balasubramaniam T. 2011. Fibrinogenolytic and
anticoagulant activities in the tissue covering the stingers of marine stingrays Dasyatis sephen and Aetobatis
narinari. J. Thromb. Thrombolysis. 31(4): 464-471.
• 
Maretic Z. 1998. Fish venoms. In: Handbook of Natural Toxins: Marine Toxins and Venoms. (Tu AT, Dekker
M) New York. pgs 445-477.
• 
Matsui T, Sato H, Hamada S, Shimizu C. 1982. Comparison of toxicity of the cultured and wild puffer fish
Fugu niphobles. Bull. Jpn. Soc. Sci. Fish. 48: 253.
• 
Matsumura K. 1998. Production of Tetrodoxin in Puffer fish Embryos. Environ. Toxicol. Phar. 6(4): 217-19.
• 
Nelsen DR, Nisani Z, Cooper AM, Fox GA, Gren ECK, Corbit AG, Hayes WK. 2014. Poisons,
toxungens, and venoms: redefining and classifying toxic biological secretions and the organisms
that employ them. Biol. Rev. Camb. Philos. Soc. 89(2): 450-465.
• 
Pryor KJ. 2008. Venom, Poison, and Electricity. Macmillan Education Australia. p.14.
• 
Russell FE. 1965. Marine Toxins and Venomous and Poisonous Marine Animals. Adv. Mar. Biol. 3:
256-257.
• 
Vetrano SJ, Lebowitz JB, Marcus S. 2002. Lionfish envenomation. J. Emerg. Med. 23(4): 379-82.
• 
Wu Z, Yang Y, Xie L, Xia G, Hu J, Wang S, Zhang R. 2005. Toxicity and distribution of
tetrodotoxin-producing bacteria in puffer fish Fugu rubripes collected from the Bohai Sea of
China. Toxicon. 46(4):471-476.
• 
Yatsumoto T, Nagai H, Yasumura D, Michishita T, Endo A, Yotsu M, Kotaki Y. 1986. Interspecies
distribution and possible origin of Tetrodotoxin. Ann. NY. Acad. Sci. 479(1): 44-51.
• 
Yu CF, Yu PHF, Chan PL, Yan Q, Wong PK. 2004. Two novel species of tetrodotoxin-producing
bacteria isolated from toxic marine puffer fishes. Toxicon. 44(6):641-647.
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Matt Koch – Photo credit: Figures 2A, B, D