How to Stay Cool the Lungfish Way

Via: Science News for Kids

Common Name: The Lungfish

A.K.A.: Subclass Dipnoi

Vital Stats:

  • 6 species; 4 in Africa, 1 in South America, 1 in Australia
  • Some species can reach up to 2m (6.6’) long and weigh 43kg (95lbs.)
  • Omnivorous, eating plants, insects, crustaceans, worms, fish, and frogs
  • Largest genome of all terrestrial vertebrates at ~133 billion base pairs

Found: Slow-moving freshwater bodies in South America, Africa, and Australia

It Does What?!

Well, they’re not much to look at, but in the “quietly carrying on while everything drops dead around you” department, the lungfishes are tops. These large, eel-looking creatures are what biologists refer to as “living fossils”, species which have existed in more or less their present form for a very, very long time. In the case of the lungfishes, around 400 million years. For the sake of comparison, this was around the same period that plants developed roots and leaves. That long ago. In fact, researchers believe that the lungfishes are the closest living relatives of the terrestrial vertebrates (that is, anything with a spinal column that lives on land).

These will probably outlast humanity.
Via: One More Generation

So what makes these things so interesting, besides being old? First off, they breathe air, as you might have guessed from their name. Australian lungfishes have a single lung, and, while they normally breathe through their gills, are able to supplement their oxygen intake with air during times of high exertion or when their water gets stale (Fun side note: During mating, Australian lungfishes make loud burping noises at the surface of the water which are thought to be part of the courtship ritual. I’ll refrain from making any Aussie jokes here… ). African and South American lungfishes, on the other hand, have two lungs and breathe nothing but air. Their gills are completely atrophied, such that they could actually drown if kept under for much longer than their usual 5-8 minutes between breaths.

“Hey! I’m trying to aestivate in here!”
Photo by: Tobias Musschoot

This ability to breathe without water results in the other fantastic ability of subclass Dipnoi. South American and African lungfish live in habitats which often dry up completely during the hottest part of the year. The fishes’ gross but brilliant answer to this is to burrow up to half a metre down into the soft mud and excrete a huge amount of mucous. As the surrounding mud dries up, the mucous forms a hard shell which keeps the curled up lungfish moist and cool. A small hole at the top of this snot-cocoon allows the fish to breathe. It’s metabolism slowed to only a small fraction of the normal rate, the creature will aestivate (like ‘hibernate’, but without the cold) like this for several months until the rains return. Laboratory experiments have shown that an African lungfish can remain alive under these conditions for as long as six years.

“Granddad”: probably older than your Granddad
Via: Shedd Aquarium

Aside from their amazing survival abilities, these fish have unusual lives, as fish go. They are extraordinarily long-lived. The Shedd Aquarium in Chicago holds an Australian lungfish known as “Granddad” which arrived there as an adult in 1933, making him at least 80 years old. Females of this species don’t even mate until they’re at least 22 years old (or so they tell their parents). What’s more, some species actually care for their young. The mother and father build an underwater nest for their offspring, which can only breathe via their semi-atrophied gills for the first seven weeks, and the father uses his body to release additional oxygen into the surrounding water, helping them to breathe. So, dual childcare: not such a new idea after all.

[Extra Credit –  Here’s a short video of a lungfish being stalked by a pelican. Spoiler: It ends badly for the lungfish.]

Says Who?

  • Brinkmann et al. (2004) Journal of Molecular Evolution 59: 834-848
  • Fishman et al. (1992) Proceedings of the American Philosophical Society 136(1): 61-72
  • Glass (2008) Respiratory Physiology & Neurobiology 160: 18-20
  • Joss (2006) General and Comparative Endocrinology 148: 285-289
  • Lee et al. (2006) General and Comparative Endocrinology 148: 306-314
  • www.fishbase.org

The Stinging Tree, or, Australia Hates Mammals

Can’t Touch This
(via: anhs.com.au)

Common Name: Stinging Tree, Gympie-Gympie

A.K.A.: Dendrocnide moroides

Found: Rainforests of Northeastern Australia

It Does What?!

Australia, which was apparently intended only for the very bravest of human beings, is home to many of the world’s most poisonous snakes, spiders, and scorpions. Even the surrounding ocean is exceptional for the number of ridiculously venomous species it contains. Still, a person could be forgiven for thinking that, so long as they stay out of the water and keep away from the creepy-crawlies, they’ll be okay. Ha ha ha… nope. In Australia, everything is out to get you.

Meet Gympie-Gympie, the Stinging Tree (or to be more accurate, stinging shrub). Growing in rainforest clearings and along creek edges- anywhere the canopy is broken- this two metre (6.5ft) high plant has large, heart-shaped leaves and juicy purple fruit. And every square centimetre of it, from the soil on up, is covered in tiny, poison-filled hypodermic needles. These hollow silicon needles are delicate enough to break off at the slightest touch, leaving them embedded in the skin of whatever creature was unfortunate enough to do so. The skin will often then close over them, making the needles nearly impossible to remove. The substance they’re filled with is a very potent neurotoxin with a very long shelf life- herbarium specimens of the plant collected in 1910 are still able to cause pain. And since the body is unable to break down silicon, this all adds up to a very long punishment for a very small mistake.

Go on, I dare you.
(Photo by Melanie Cook)

A brief brush against a stinging tree produces intense pain that peaks after about half an hour, but can literally take years to subside completely. Numerous dogs and horses have died because the pain was so intense. There is even one official record of a human having died- a Dutch botanist of the 1920s. Oddly enough, no actual tissue damage is done by the neurotoxin- death due to the plant is attributed to heart failure due to the shock of the pain, described by one researcher, Dr. Marina Hurley, as “like being burnt with hot acid and electrocuted at the same time.” An ex-serviceman who fell right into one of the trees while crossing a creek in the 1940s describes having had to be tied down to his hospital bed for three weeks because the discomfort was so intense. One intrepid/insane researcher actually purified the neurotoxin and injected himself with it, suffering terribly and thereby proving that the toxin, rather than the needles, causes the majority of the pain. But not all of it… simply standing near a gympie-gympie for an extended period can cause allergic reactions and nosebleeds as the needles are shed in the wind.

“I eat neurotoxins for breakfast.”
(Via: Billabong Sanctuary)

So this must be just about the best herbivore-defence system ever, right? Amusingly, no. The trees still undergo heavy damage due to hungry spiders, ants, snails, and especially beetles, all of which can avoid its defences. The tree is even prey to one species of marsupial, the red-legged pademelon, which is either immune to the neurotoxin or has enormous pain tolerance. So why develop this extensive arsenal if it’s completely ineffective? One expert has suggested that it may have evolved to protect the plants from the now long-extinct giant Diprotodonts which once inhabited the Australian rainforest, making it one more dangerous relic of a long-ended war. You win, stinging tree, you win.

[Fun Fact: The best way to attempt to remove some of those poisonous silicon needles embedded in your arm?  Wax hair removal strips, according to the Queensland ambulance service.]

Says Who?

Every Day is a Crappy Day for the Bird-Dropping Spider (Celaenia excavata)

Celaenia excavata
(via: http://commons.wikimedia.org/wiki)

Common Name: The Bird-dropping Spider

A.K.A.: Celaenia excavata

Found: Eastern and Southern Coastal Australia

It Does What?!

Quick, what’s the first thing that comes to your mind when someone says “disgustingly inedible” ?

If you said “Why, poop, of course!”… congratulations, you think just like Celaenia excavata. And if the thing you’re trying to look inedible to is a bird, naturally, you go with bird poop. Such is the evolutionary reasoning behind the politely-named Bird-Dropping Spider. And while remaining motionless is a must, looking the way it does allows the spider to sit comfortably atop a leaf all day, secure in the knowledge that spiders’ main predators, birds and wasps (who apparently aren’t into eating bird poop either), won’t take an interest.

“Nobody here but us droppings.”
(Thanks to Ron Atkinson at http://www.findaspider.org.au)

But the mimicry doesn’t end there for this sneaky little guy- by day it sits inactive and gross-looking, but by night, it hangs upside down from a leaf and releases the mating pheromones of a female moth. When some unlucky male moth comes looking for a good time, the spider snatches it right out of the air with its powerful front legs and wraps it up for dinner. The moth may be eaten right away or, if its capturer isn’t feeling hungry quite yet, be hung under a leaf next to the spider’s egg sacs, which, oddly enough, look like nuts (see top photo).

Believe it or not, Celaenia excavata isn’t the only spider out there masquerading as merde. Another such trickster is Mastophora cornigera, a North American species which is part of a group known as the Bolas Spiders, or Fishing Spiders. Not content to hope their prey wanders into arm’s reach, bolas spiders release pheromones to attract male moths, then dangle a line of silk with a sticky blob on the end. Once a moth gets close enough, the spider swings its line and –yoink– rips the poor thing right out of mid-air. Whoever thought up Spiderman’s web-slinger clearly had a bolas spider in mind.

So there you have it, the leisurely lifestyle of a successful spider: pile of poo by day, upside-down fisherman by night.

Says Who?