Ecology Notes: Fish Unit

Almost all Fish

Sting, they don’t bite

Venom apparatus and properties are

Similar in Most Fish

Cartilaginous fishes

Fish with no bones

harks

Rays & skates

Chimaeras

Bony fishes

Lobe-finned fishes(coelacanth, lungfishes)

Ray-finned fishes(most common fishes)

Most are teleost fishes

Venom apparatus of fishes

Typically consists of venom glands located in paired grooves on either side of sharp spines, with the spine and venom gland complex covered by an integumentary sheath

Venomous fish lack musculature associated with their venom apparatus and are unable to voluntarily control their release of venom

Fish spines are modified

Scales so they can regenerate if it breaks off

Dorsal spines (spines on top) are the most

common venom apparatus

Other uncommon types of venom apparatus

Venomous fangs

cleithral spines

subopercular spines

Venomous spines are most often found in association with

the dorsal fin

Stargazers, Toadfish, and Weeverfish posses

Venomous opercular spines on either side of their heads

Stingrays produce

Serrated spines

Lionfishes

Two of the twelve species are established as significant invasive species off the East Coast of the US and the Caribbean

Stonefish

World’s most venomous fish

Capable of killing an adult in an hour

Toadfishes

Some possess the most highly developed venom apparatus

Sound like toads

Most fishes use venom

Primarily for defense

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Only 2 venomous fishes use venom in feeding roles, these are

One jawed eel and fanged tooth bennies

Components of venom in fish

Main toxins primarily contain proteins

A novel family of toxins possessing kiminogenase ( a kind of proteinase) activity have been found in

toadfish venom

A variety of smaller protein toxins as well as peptides, enzymes, and nonproteinaceous molecules have been found

in some fish toxins

Nearly all fish venoms possess

Haemolytic activity

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Hyaluronidase is

a common venom enzyme that facilitates distribution of toxic components

Death from fish envenomation has been attributed to

cardiovascular effects such as severe hypotension or cardiac or respiratory failure

Envenomation symptoms such as paralysis, muscles spasms, and prolonged weakness clearly demonstrate that

Fish venoms not only target the cardiovasular system but also the neuromuscular system

The release of **endogenous** **acetylcholine** causes variations in

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* blood pressure, respiration, and cardiac activity 

Other components trigger the release of **endogenous nitric oxide**, which

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* increases vascular permeability and causes relaxation in smooth muscle (i.e., lowers blood pressure)  

Symptoms of fish envenomation

**Intense pain (out of proportion to wound) and severe edema are the major symptoms common to the vast majority of fish envenomations**

* **Systemic symptoms include ischemia, muscle spasms, tissue necrosis, prolonged weakness, nausea, paralysis of the affected limb, hallucinations, loss of perception, hypotension, tachycardia, and respiratory distress** 
* Slow healing and **necrosis** have been observed
* **The extent of damage varies according to the species, number and depth of envenomation sites, and individual reaction to the venom component** 
* **Secondary infections are also known to occur, leading to additional damage**

Treatment of envenomation

Soak in hot water for an extended period of time in order to attempt to denature the protein components in the venom

Morphine is innefective

Stonefish venom treatment

Since so little is known about the mechanisms by which fish venoms work, it is nearly impossible to formulate highly effective treatments against them

* Commercially available **horse-derived antivenom for stonefish** **envenomation for extreme cases**

Medical applications of fish venoms

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* **Marine venoms largely ignored as source for potential pharmaceuticals, despite research suggesting that there are more marine venomous species than all venomous terrestrial animals combined**
* **Little is known about the composition of marine venoms**
* **Bioassay-guided fractionation traditionally used for marine venom analysis, but is time-consuming and requires large amounts of crude venoms, which are not always available** 

Fish poisonings

Ichthyosarcotoxism

puffer fish poisoning

• Tetrodotoxin (TTX) is one of the strongest toxins known (see previous graphic)

• Neurotoxin in fish liver, gonads, intestines & skin

  • Fish muscles are generally edible

  • Fugu is prepared in Japan by highly trained chefs & sold in special restaurants

    • Still number one cause of fatal food poisoning in Japan

  • First symptoms include tingling of lips & tongue (see last slide for more symptoms)

  • Fatal w/in 24 hours; case fatality rate is about 60%

  • No antidote; respiratory support until excreted in the urine 

  • Activated charcoal and/or gastric lavage (stomach pumping) if patient presents within 60 minutes of ingestion

Ciguatera

ciguatoxin

Scombroid poisoning

histamine

Sea turtle poisoning

Tetrodotoxin

is a neurotoxin named after Tetraodontiformes, a fish order that includes puffers, porcupine fishes, blowfish, ocean sunfishes, triggerfish, and others

Also found in rough-skinned newts, frogs, toads, blue-ringed octopus, crabs, starfish, and flatworms

Tetrodotoxic Fishes 

• Multiple species in Order Tetraodontiformes

• Puffers most common in tropics but extend into temperate zone (including US Atlantic Coast)

• Puff up by swallowing air or water

• Can also bite with large teeth or “beak”

• Offensive odor