#nematocysts

[adelicateculturecell]

Journey to the Microcosmos

[lifesciencepotluck]

Exploding poison capsules

One of the biggest reasons why I developed a deep obsession with anemones is because of my fascination with cnidae. Cnidae are subcellular structures that can do a bunch of stuff. They can play a part in aggression, adhesion and even building tubes for burrowing anemones. Cnidae are usually secreted by the Golgi apparatus, go through some fabulous modifications before moving to the surface of tentacle (or other tissues). There are three major type of cnidae: spirocysts, ptychocysts and nematocysts. They usually have a thin hollow tube that can be discharged. Spirocysts look like little corkscrews and they help anemones to stick to things. They are also unique to Anthozoans. Ptychocysts are specific to tube anemones (which aren't technically anemones but that’s a conversation for another day) and well, they help the tube anemones make adorable tubes that help them burrow into the sand. Nematocysts are the ones that involved in storing and injecting toxins.

The mechanism injecting toxins is straight out of a Michael Bay movie. Basically, the capsule (nematocysts), swells up and explodes. The thin hollow tube is shot out like a harpoon and it injects the venom into whatever poor fool is contact with the anemone or jellyfish. The actual mechanism of cnidae discharge is still a bit hazy because this entire process happens within nano seconds. 

Step 1: Have some kind of chemical or mechanical stimulation. (AKA piss off the anemone by poking it or drastically change its environment) 

Step 2: A bunch of cations (or positively charged ions) will flood the cnidae and due to the magic of osmosis, the capsule swells up as the osmotic pressure increases.

Step 3: At some point the pressure will be too damn high and the nematocysts will burst. 

Step 4: The thin hollow tube is flung out, it penetrates the target and the venom flows through the hollow tube. Congrats you have successfully injected venom into target! Yay!

Step 5: Slaughter your foes with your exploding poison capsules.

Do you finally see why I’m obsessed with these things?  

There are other theories of how the cnidae discharges (which I will cover later on), but this a general summary of what happens. The type and distribution of cnidae is impacted by a bunch of factors such as: anemone species, prey size, salinity, types of thirsty predators the anemone has to deal with, etc. Of course, there are different types of nematocysts as well. There are two main types of nematocysts: haplonemes and heteronemes. Haplonemes have tubes and spines on nematocysts that are not divided into different parts. On the other hand, heteronemes have spines, plus there is a distal basal shaft and distal tube combo. You can identify the type of cnidae through light microscopy of tissue samples from cnidarians. Sometimes you have to look at the discharged or fired nematocysts so you can see the threads/tubes in order to differentiate between different types of cnidae.

Atrichs: Haploneme. They are usually found in catch tentacles (they are extra pair of tentacles used to fight other or even the same species of anemones). Have smooth threads without nay shafts or barbs.

Holotrichs: Haploneme. There is no distinct basal shaft but there are barbs on the threads.

Basitrichs: Heteroneme. They have threads without shafts but they have barbs at the base only.

Microbasic b-mastigophores: Heteroneme. They have a shaft and the threads are not well distinguished from the shaft. The shaft contains barbs. 

Microbasic p-mastigophores: Heteroneme. The shaft is distinct from the base and has funnel shape when the nematocyst is unfired. Sometimes the thread is armed (hoplotelic).

Microbasic a-mastigophores: Heteroneme. The thread is smaller and only the barbed shaft is present. This shaft is three times as long as the capsule.

Macrobasic a-mastigophores are similar to microbasic amastigophors, but the shaft is more than three times as long as the capsule. In unexploded capsules the shaft forms coils. So, you need to have fired cnidae to tell the difference between microbasic and macrobasic a-mastigophores.

I wish my drawings of cnidae were this beautiful—but they aren’t.  So here you go. (Source: http://www.meghanrocktopus.com) 

Everyone knows that flow charts make evyerthing better! (This is from Shick’s A functional Biology of Sea anemones)

This is how nematocysts look like under a microscope. 

Cnidae aren't the only parts of an anemone that can contain toxins, some anemones have ectodermal and endodermal gland cells which can secrete and store toxins. Understanding the cnidae composition for each tissue for your anemone is important for venom extraction. Trust me you will need all the information you can get because venom extraction is a special kind of purgatory, which I will cover in my next post.

Citations:

Wei, N., Yap, L., Fautin, D. G., Ramos, D. A. & Tan, R. Sea anemones of Singapore: Synpeachia temasek new genus, new species, and redescription of Metapeachia tropica (Cnidaria: Actiniaria: Haloclavidae). Source Proc. Biol. Soc. Washingt. 127, 439–454

Yanagi, Kensuke & Fujii, Takuma. (2015). Redescription of the Sea Anemone Exocoelactis actinostoloides (Cnidaria: Anthozoa: Actiniaria) Based on a Topotypic Specimen Collected from Tokyo Bay, Japan. Species Diversity. 20. 209. 10.12782/sd.20.2.199.

Jouiaei, M. et al. Ancient venom systems: A review on cnidaria toxins. Toxins (Basel). 7, 2251–2271 (2015).

Shick JM (1991), A functional Biology of Sea anemones, Springer Science+ Business xMedia Dordrecht, 395 pp. 

[nationalpost-blog]

Photographers stun scientists with slow-motion video of jellyfish sting: ‘I’ve got goosebumps all over, it’s great!’

Because jellyfish stings happen so quickly — on the order of milliseconds, or about the time it takes you to blink — they’re challenging to study in the lab. But with the help of his super-slow motion camera, YouTuber SmarterEveryDay was able to catch a lightening-fast jellyfish sting in action in toxicologist Jamie Seymour’s lab at James Cook University in Cairns, Australia, by touching two leads from a nine volt battery to its tentacle.

On average, it took the anemone about 11 milliseconds to fire its venom-loaded nematocysts in response to the trigger and about 1/3 of a second, or 333 milliseconds, for the venom to eject after they triggered the nematocysts. That’s a significant delay from the mere 11 milliseconds it took to fire up those needles.

The venom of a box jellyfish is one of the deadliest in the world. It attacks the heart, skin cells, and the nervous system and can be so painful that people sometimes die of shock or a heart attack before they can swim to safety.

PHOTOS: SmarterEveryDay/YouTube

[mermaidsirena]

There are over 3,000 species of these colorful sea slugs. Some nudibranchs defend themselves against predators with toxins...but not those they are born with. Some eat prey with nematocysts, and the nematocysts stored on the nudibranch's backs where they can be used to sting predators. Pretty cool!! Image: SeaWayBlog

[explosionsoflife]

Phylum Cnidaria (meaning nettle-like) is an interesting group of more than 9000 species. It takes its name from cells called cnidocytes, which contain the stinging organelles called nematocysts. Nematocysts are formed and used only by cnidarians. Another name for the phylum, Coelenterata (meaning hollow gut) is used less commonly than formerly, and it sometimes now refers to both radiate phyla (Cnidarians and Ctenophores), since it's meaning is equally applicable to both.

The phylum Cnidaria includes some of nature's strangest and loveliest creatures: branching, plantlike hydroids; flowerlike sea anemones; jellyfishes; and those architects of the ocean floor, horny corals and stony corals.

(Photo source)

[intrinsicallylinkedlife]

I love Cnaidarians, it is my favourite phylum.

Upside-down jellyfish (Cassiopea andromeda) is a type of jellyfish that usually lives in intertidal sand or mud flats, shallow lagoons, and around mangroves.

This jellyfish, many times mistaken for a sea anemone, usually has its mouth upward on the bottom. Its bell, which is yellow-brown with streaks and spots that are white or pale, vibrates to make the water flow through its arms for respiration and the obtaining of food.

You don't have to even touch this jelly to get stung, the jellyfish secretes a mucus that is filled with nematocysts (stinging cells) which is carried by the water to its' prey.

The Zooxanthellae live in the tissues of its body and it is the responsible for the color of it. As the Zooxanthellaeon gets food for the Cassiopea andromeda, in response, it gets the sunlight that is necessary for the photosynthetic algae.

This jellyfish also lives in a symbiotic relationship with photosynthetic dinoflagellate algae, the Zooxanthellae, and with shrimps.

But still, they are pretty.