Ecology study guide

Toxin

A harmful substance produced by living organisms, such as bacteria, plants, or animals. It can cause various adverse effects on the body, ranging from mild irritation to severe illness or even death.

Poison

a toxic substance that is passively transferred without involvement of a delivery apparatus or infliction of a wound

• Method of delivery is a primary criterion distinguishing poison from venom

• Usually obtained through ingestion, inhalation, or absorption through the skin

Venom

a toxic secretion produced by specialized cells in an **animal** that is delivered to another animal through a **delivery apparatus**, typically through the infliction of a wound 

* Most common methods of delivery: **bite** or **sting**

Differences between poison and venom

Poison: Can be single substance or mixture, defensive produced by different organism (Butterfly)

Venom: Always a complex mixture, offensive/defensive, produced by organism using it (Snakebite)

exogenous

External; originating from different organism

endogenous

Originating or produced within an organism or system, rather than externally influenced.

Benefits of toxic and venomous animals

Pest control, Pollination, Soil Enrichment, Food Web

Sponges

Phylum Porifera

• Sessile filter-feeders lacking tissues & organs

• Most are marine; a few freshwater spp.

calcareous sponges

Calcarea

Phylum Porifera members with calcium carbonate skeletons. Filter-feeders that live in marine environments. Unique canal system for water circulation.

glass sponges

Glass sponges are marine animals characterized by their intricate glass-like skeletons. They belong to the phylum Porifera and are filter feeders.

demosponges

Phylum of sponges with diverse body structures. Most common sponge group, found in both freshwater and marine environments. Filter feeders that extract food particles from water. Have a soft, spongy body with a network of canals and chambers. Lack spicules, instead have a skeleton made of spongin fibers.

  encrusting sponges

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Organisms that attach to and grow on sponges, forming a protective layer.

How are sponges venomous?

• Contact can cause chemical irritation (contact dermatitis)

• Rapid erythema (redness), itching & stinging followed by edema (swelling) and joint stiffness

• Spicules can penetrate skin (irritant dermatitis)

• First aid: wash & dry area, use adhesive tape to pull out spicules, corticosteroid cream, antihistamines

Fire sponges

• Caribbean & Pacific tidal zone & shallows; as far north as South Carolina

• Two general habitats: among red mangrove roots and in coral reefs

• Worst sponge sting

• Helps control cyanobacteria by filter feeding

Cnidarians

• All are predators that sting their prey with cnidocytes (cells) containing cnidae (stinging capsules)

  • The term “nematocyst” is used for either of these, but see below

• Venom is used in defense and predation

  • Stings are also used in territorial disputes in sea anemones

• Stings are touch activated, so floating tentacles (or dead jellyfish on the beach) can sting

• Three kinds of cnidae:

1. Penetrant nematocysts– pierce & inject toxin that can paralyze or kill prey

2. Glutinant – stick to prey

3. Volvent – elastic lasso-like threads

Hydrozoa

fire coral, Portuguese man o’war

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Scyphozoa

true **jellyfish**

Cubozoa

box jellyfish

Anthozoa

true **corals, sea anemones**

• Hard coral skeleton can scrape skin

• Some anemones can cause toxic & allergic skin  reactions

Snakelocks  anemone

fire coral

• Found on coral reefs but not a true coral

• Danger to divers, snorkelers, swimmers, but diving suit or clothing prevents stings

• Protein toxin causes skin necrosis

• Symptoms: immediate pain, erythema, edema, can be

urticaria (hives); subsides in hours

• Usually not severe so no special first aid

other than skin lotion

Portuguese man o’ war (Physalis)

• All oceans (cosmopolitan)

• A pelagic colony with a sail (pneumatophore)

• Tentacles & polyps average 10 meters long! (NOAA)

• Hydrozoan, not

jellyfish (Scyphozoa)

*Physalia* venom

• Toxins are proteins

  • Physaliatoxin - cytolytic, hemolytic, causes death in experimental animals

• Symptoms: immediate pain, urticaria, skin necrosis; nonspecific symptoms may be present

First fatal envenoming due to acute circulatory failure reported in 1987 (Stein MR, et al. 1989. Fatal Portuguese man-o'-war (Physalia physalis) envenomation. Ann Emerg Med. 18(3):312-5. doi: 10.1016/s0196-0644(89)80421-4.

First aid for *Physalia* stings

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• Get victim out of the water;

pain may make them drown

• Remove tentacles with forceps

(use gloves), [or sprinkle with sand

and then scrape off]

• 2017 recommendation is to douse with vinegar first

• Most stings are trivial, but contact with large areas of skin may be life threatening

• Get victim to a hospital

Box jellyfish/ sea wasp (Chironex fleckeri)

• Australia & western tropical Pacific

• Bell can grow to about size of a basketball; 60 tentacles are up to 3 meters long

• A meter of tentacle contact can provoke immediate cardiovascular collapse and death within minutes

• At least 64 known deaths in Australia from 1884 to 2021

Box jellyfish antivenom

• Survival following box jellyfish envenomation relies on the early provision of advanced cardiac life support (ACLS).

• Good resuscitation should be the mainstay of treatment.

• The efficacy of box jellyfish antivenom has not been proven, nor is the optimal dosing regimen known.

Venomous molluscs

Blue ringed octopus - Class Cephalopoda

Nudibranchs -  Class Gastropoda

Cone snails - Class Gastropoda

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Shellfish poisoning

Amnesic (ASP) – domoic acid (diatoms)

Diarrheic (DSP) - okadaic acid (dinoflagellates)

Paralytic (PSP) – saxitoxin (red tide dinoflagellates)

Neurotoxic (NSP) – brevetoxin (red tide dinoflagellates)

Blue ringed octopus

• Australia & Pacific islands

• Shallow rocky reefs

• Less than 20 cm, armtip to armtip

• Parrot beak-like jaws at base of arms

• Toxins are in saliva

  • Hyaluronidase (enzyme)

  • Serotonin, noradrenaline

  • Tetrodotoxin used for prey capture; inhibits nerve transmission – bacterial origin; obtained through food chain or by endogenous bacteria (Asakawa et al. 2019)

• Envenomings due to handling; animal never attacks

Blue ringed octopus toxins

• Symptoms appear in a few minutes

  • General muscle weakness

  • Tingling of face, neck, and limbs followed by numbness

  • Visual disturbances, ataxia

  • Paralytic symptoms begin with difficulty swallowing and breathing

  • Death due to respiratory paralysis

    • At least 3 deaths; may be as may as 16

• Seek medical attention immediately because of risk of respiratory failure

  • Artificial ventilation necessary

Nudibranchs

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• Sea slugs are marine snails without shells

• Feed on cnidarians & sequester nematocysts

• Glaucus (sea lizard) even feeds on man o’war

(Physalia)

• Touching nudibranchs may cause stinging

• Painful; depends on which cnidarian the nematocysts came from and how many were eaten

• Pour vinegar over affected area

Cone snails

• Venom contains about 100 different neurotoxins

• Each species of cone snail has its own unique cocktail of toxins, with very little overlap among species, yielding >50,000 toxins among the cone snails of the world (Pierce 2020 Carnegie Museum of Natural History)

  • α-conotoxins – block transmission at synapses

  • ω-conotoxins – calcium channel antagonists; block acetylcholine release at motor nerve end plates

  • μ-conotoxins – block sodium channels of skeletal muscle membranes, not neuron membranes

  • δ-conotoxins – inhibit inactivation of sodium channels, causing contracture of skeletal muscle & paralysis

  • Others