Thursday, 23 October 2014

Species of the Week: Leafcutter Ants

If you're a naturalist or have an interest in wildlife, then you'll most likely have heard of Leafcutter Ants. These industrious little insects are a wonder of the natural world, and well worth a Species of the Week dedicated to them.
The common name Leafcutter Ants is pretty vague, since it can mean any of the species belonging to either genus Atta or Acromyrmex. Distinguishing the genus is easy: Atta species have a smooth exoskeleton with 3 pairs of spines, whereas Acromyrmex species have a rough exoskeleton and 4 pairs of spines. There are 47 known species in total, and they can be found in Mexico, South and Central America, and also parts of southern United States.

Within a species there are several variations, known as castes, which specialise in doing a certain job. In most Leafcutter species there are the following castes:
Minims - these look after the young and fungus gardens (more on them later). They are the smallest caste.
Mediae - the actual leaf cutters. They cut up vegetation using their mandibles and transport it back to the nest.
Minors - these patrol the borders of the nest and attack intruders.
Majors - also known as soldiers, this caste deals with enemies that get past the minors. They have enormous mandibles to bite at intruders.
All these, as well as a Queen, larva, pupa, and eggs, live in an underground nest that can span over 30m across! The nest may contain up to 8,000,000 individual ants!

 An Acromyrmex octospinosus mediae cutting a leaf.

This Acromyrmex octospinosus mediae is making good progress cutting the leaf.

Some Atta columbica mediae take leaves back to their nest. Often the minors will ride on the leaves being carried, possibly keeping an eye out for parasitic flies that may endanger the mediae.

You might think that the only creature on Earth that can farm plants and animals are humans. But ants also do it - several species 'farm' aphids for honeydew, and Leafcutters farm fungus. It is a common misconception that Leafcutters are taking the cut foliage back to their nest to eat - but they're actually growing fungi on it. They have a chamber in their nest called the fungus gardens, in which all the foliage is placed. The fungi grows on the cut leaves and is tended to by the minims. The fungi also releases a chemical that the ants can detect, telling them that a particular type of leaf is toxic to them. The ants will remove the offending foliage and never collect it again. The farmed fungus is fed to the larva - the adults never eat it, instead they have a diet of tree sap.

Some Leafcutter Ants in their fungus garden.

A group of hard-working mediae can strip a whole citrus tree in just 24 hours. Because of this, they aren't too popular amongst farmers and are seen as an agricultural pest.

The Queen is always hard at work in the nest laying eggs. She may lay up to 1000 in a single day! When the larva hatch out, they are immediately fed pieces of fungus by the minims.

A Leafcutter Ant Queen amongst several different castes

Every so often, young Queens and males will leave the nest and fly up into the air. This is known as the revoada. A female will mate with several males while she's flying, then land on the ground and shed her wings. She begins to make a burrow: the beginning of her own colony. She takes with her a little piece of fungus from her previous home to kick-start a fungus garden. She will begin to lay eggs in her new nest, and when they hatch and the larva turn into adults, she will have her first workers.

 Some captive Atta cephalotes take leaves back to their nest

I hope that you have enjoyed this post as much as I have enjoyed writing it.
These ants really are incredible creatures. Next to humans, they have the most complex societies of any animal. If that's not amazing, then I don't know what is.

Until next time, keep on the wild side!

Top 4 Strangest Cephalopods

Cephalopods are truly fascinating animals and all of them are pretty strange, so choosing 4 of the weirdest was hard. But here they all are: behold my top 4 strangest cephalapods. 

Glass Squid (Chranchiidae)

This family of odd squid contains 60 species, each one weirder than the last. They are so named because a majority of the species are transparent, which helps them evade predators. Distinguishing features include the swollen body and the tiny tentacles, though in some species the third pair are enlarged and may be used to capture prey. Several species have bioluminescent spots on them, which are probably used to cancel out their shadow and therefore make them further camouflaged.
Juveniles live as plankton at the ocean surface, but as they mature they retreat to deeper areas.

Paper Nautilus (Argonauta)

Obviously these creatures aren't really made of paper, but nor are they related to the nautilus. Egg Case Octopus would be a more fitting name, because they're actually an octopus and the 'shell' is a paper-thin egg case. The female secretes the case from 2 specialised tentacles then lays her eggs inside. She will then squirm into the egg case and stay there so that she can watch over her eggs. It was once believed that these surface dwelling octopus used their tentacles as sails and bobbed along like a ship.
Paper Nautilus exhibit extreme sexual dimorphism: the male grows to only 2cm long, compared to the 10cm long female, excluding the egg case. It is thought that the male will mate only once in his life, whereas the female will mate with several males many times.
They catch invertebrate prey using their tentacles, then subdue it with venom from the beak. If the prey has a shell then the octopus will use a hard radula to drill through it to the soft flesh inside.

Dumbo Octopus (Grimpoteuthis)

Not only does this creature come in several whacky colours such as orange, blue, and purple but it also has ear-like flaps just above its eye, giving it the nickname of Dumbo Octopus. These flaps are used to propel the creature forwards. The tentacles are attached by a web of skin, giving it a skirt-like appearance.
Most of the 37 known species live at extreme depths, flapping over the sea bed, searching for invertebrate prey.
Though the average size is around 20cm long, the largest ever found was 1.8 metres!
Dumbo Octopus are found in many parts of the world, and live for 3-5 years.

Mimic Octopus (Thamoctopus mimicus)

Most octopus can change their skin colour and texture, but the Mimic Octopus can actually bend its body into a shape that resembles other creatures. It is known to mimic up to 15 other species! It often mimics poisonous animals to deter predators, or pretends to be a harmless creature so that it can sneak up on prey. Here's a few of the animals that it mimics:
Lionfish - by shaping its tentacles to look like the fish's venomous spines, the octopus can be safe from most predators.
Sea Snake - the octopus changes its hue to the correct colour, then retreats down a burrow. It will then extend two tentacles from the burrow, making them look like the two ends of the sea snake.
Flatfish - by pressing its tentacles together and gliding over the seabed, the octopus can sneak up on prey by pretending to be harmless.
The Mimic's natural colour is a dull light brown. They can grow to 60cm long!
The octopus has been observed showing some rather interesting behavior: clumping its tentacles together to look like human legs, then running across the sea bed! What the octopus is meant to be mimicking in this case is unknown.

I hope that you've enjoyed today's post. If anybody has any suggestions for a Top 5 Strangest list, then please do let me know using the comment feature.

Until next time, keep on the wild side!

Tuesday, 7 October 2014

Top 5 Strangest Slugs and Snails

Ever seen a bright pink slug? Or how about a snail with a green shell? A slug that eats earthworms? Or a sea snail with enough venom to kill a man? Behold my top 5 strangest slugs and snails!

Long-tailed Slug (Ibycus rachelae)

This strange slug is native to Sabah, Borneo. It has a small, semi-visible shell that is half covered with flaps of skin. It will wrap its long tail around its yellowy-green body when resting. Not much is known about what it feeds on in its rainforest home, but presumably it is a herbivore (not all slugs are herbivores, as you will discover later on in my post . . .). It fires so called 'love darts' at potential mates - harpoon-like structures made from calcium carbonate. It is thought that the darts inject a hormone into the mate and increases its chances of reproduction. This has earned it the nickname of 'Ninja Slug'!

Emerald Green Snail (Papustyla pulcherrima)

This amazing species has a stunning bright green shell and is found only on Manus Island in northern Papua New Guinea. These small, 4cm long snails live high in the trees feeding upon fungi and lichen that grow there. The shell is covered in a thin protein layer that is bright green. The layer eventually drops away when the snail dies, showing the actual shell, which is bright yellow. In the picture above you can see both the yellow shell and several retaining the green layer.
Unfortunately, these snails were once in high demand, sought after as jewelry. This, along with habitat loss, has led towards these snails becoming critically endangered.

Shelled Slug (Testacella haliotidea)

Slugs are herbivores, right? The only harm they can do is eat our vegetables . . . but not if you're an earthworm and there's a Shelled Slug on the prowl! These 12cm long creatures spend most of their life underground, burrowing through the soil and hunting earthworms. When they find their prey, the worm's flesh is scraped away and eaten using the radula. They can be found in the western Mediterranean and also in Great Britain, though not in Scotland. Most people have never even seen one, not because they're particularly rare, but because they hardly ever come to the surface. If you're lucky then you might find one under a stone or log, but this is quite a rare occurrence.
As if a subterranean, earthworm-hunting slug isn't strange enough, it has a small shell, just like the Long-tailed Slug. Testacella's shell is even smaller though, under a cm in length! It serves no function that we know of.

Triboniopharus aff. graeffei 

If you're wondering what the 'aff.' part means, then it is a term used to show that the organism is related to species in the genus shown before the aff. So in this case, it is thought that the creature is related to the species in the Triboniopharus genus, because we're unsure about what genus this species actually belongs to. 

When I first heard about a bright pink slug from Australia, I hardly believed it. It's hard to believe that this creature is real, but it is. They are found only on Mount Kaputer, Australia. They spend the day in the leaf litter, but when night falls they climb up into the trees to feed on moss and algae growing on the trunk. They can grow to up to 20cm long! They have not yet been given a common name.
Nobody's really sure why the slugs are so vividly coloured. They're not advertising their toxicity, because many birds and other creatures feed on them, showing that the slugs are not poisonous. It has been suggested that the colouration may help them blend in amongst the reddening eucalyptus leaves on the forest floor, but this is unlikely because they spend the whole night up in the trees amongst the green leaves.

Textile Cone (Conus textile)

This sea snail may look pretty and harmless, but it's actually quite the opposite. Found in most tropical oceans and growing up to 10cm long, this creature, along with other Cone snails, is probably one of the most dangerous molluscs in the world. It has a long, harpoon-like radula which it uses to spear prey. Some species harpoon fish, but C. textile specializes in hunting other sea snails. Once a prey item is speared, toxins are injected into its body via the radula. Picking up this creature would be a big mistake, because it will also use its toxins in self-defense as well as hunting. Several human deaths have been attributed to this species.
Females lay hundreds of eggs, which hatch in 16-17 days. The larvae will then float in the current for around 16 days, then settle down and become adults.

I hope that you've enjoyed today's post. Please do let me know which species you thought was strangest using the comment feature.

Until next time, keep on the wild side!

Monday, 6 October 2014

Species of the Week: Hermit Crabs

I am very fond of Hermit Crabs - they're fascinating crustaceans, and I have good memories of watching them scrambling about in my old marine aquarium. Hermit Crabs are a superfamily, known scientifically as the Paguroidea superfamily. They are well known for using empty sea snail shells as a mobile house, but occasionally they will use hollow stones or bits of wood!
Hermit Crabs have lots of adaptions to make life in a salvaged shell much easier. They have 10 legs in total, but only 6 are visible - these are called the walking legs. The remaining 4 are small and hidden in the shell. These legs are so small that they almost appear vestigial, but they're actually used to cling to the inside of the shell, making sure that the crab doesn't slip out. When they sense a potential predator they retreat deep into their shell and use their hard claws to block the entrance.

This man-made glass shell allows us to see the long, soft back end of the crab and its small, usually hidden back legs.

Though most are fully aquatic, some are terrestrial - but their larvae still need to develop in the water. One of these terrestrial species is the enormous Coconut Crab, which despite being a Hermit Crab, does not use a salvaged shell. It is mainly found on islands in the Indian Ocean. This remarkable animal can grow up to a metre long and weigh a whopping 4.1 kg - earning it the title of the world's largest terrestrial invertebrate. These crustaceans get their name from reports of them climbing trees and cracking open coconuts to feed on the flesh inside. Although they can and do climb trees, and they are strong enough to crack open the hard husk, coconuts do not form a major part of their diet. They mainly feed on seeds, fruit, nuts, and even carrion.

 A Coconut Crab inside its burrow.
Some Hermit Crabs have developed a symbiotic relationship with sea anemones. The crab attaches the anemone to its shell and allows it to feed upon leftovers from the crab's meal. In return the anemone protects the crab using its stinging tentacles.
 A Hermit Crab with an Anemone on its shell.
An interesting experiment has been done with Common Hermit Crabs (Pagurus bernhardus), which is native to the UK. This experiment includes 2 tanks full of sea water, one of which has black sand, and the other golden sand. In the black sand tank several black shells are placed, and in the golden sand tank several golden shells are added. Now some Hermit Crabs with golden shells are added to the tank with black sand and shells. Some Hermit Crabs with black shells are then added to the tank with golden sand and shells. At this point most Hermit Crabs swap their shell for one already in the tank. This shows that the crabs are capable of noticing colours and behaving accordingly so that they can remain camouflaged.
 A Common Hermit Crab.
Hermit Crabs have been around for many millions of years. Interestingly, a fossil Hermit Crab from the Early Cretaceous period (146 million years ago) has been discovered using an abandoned ammonite shell as a home!
As I have already mentioned, I used to keep several tropical Hermit Crab species in a marine tank. They were fascinating to watch, and several times I observed them swapping shells. I had some particularly large ones with blue and black legs called Calcinus elegans. Sometimes one of these crabs would see a shell that it liked being used by another. It would then tap unrelentingly at the shell until the owner was eventually forced to leave it. The tapping was pretty loud and could easily be heard through the glass! My favorite species that I had was Ciliopagurus strigatus, also known as the Halloween Hermit Crab. It had bright orange and red bands on its legs, and was one of my larger species. I also had some Scarlet Reef Hermit Crabs (Paguristes cadenati) and Dwarf Zebra Hermit Crabs (Calcinus laevimanus).
 A Halloween Hermit Crab.

Calcinus elegans

Probably the strangest Hermit Crab species that I've ever seen is the Hairy Yellow Hermit Crab (Aniculus maximus), a large marine species from the Indo-Pacific. They are opportunistic feeders, eating pretty much anything that they find. They are well known as a bad aquarium inhabitant because they usually eat everything else in the tank and destroy the rock work.
 A Hairy Yellow Hermit Crab
I hope that you've enjoyed today's post as much as I've enjoyed writing it. Hermit Crabs really are amazing creatures.
Until next time, keep on the wild side!