Welcome to the Blog on Invertebrates. Over 97% of life on Earth consists of the invertebrate. Those are the life forms without a spinal backbone and consists of creatures from the land to the sea. This blog will talk about those animals and on-going research.
I really love to study about the life in the ocean. That is the reason that I double majored in marine biology and zoology. Life is so exotic and alien in the depths and it fascinates me in the evolution of species from the bottom dwellers to the splash zone. These organisms are part of an ecosystem that remains a favorite of mine to research. Every once in a while, I stumble upon interesting creatures that I like to gain a better understanding of, so I scour the internet and libraries looking for information on those animals. One such animal that I recently undercovered an interest on is called Anomalocaris, or the abnormal shrimp that is related to the arthrods. It is an extinct genus of anomalocaridid. The first fossils were found in both theOgygopsisShale and in the famed Burgess Shale.Can you imagine coming up on one of these creatures while diving? Take a look at the size of these "monsters" in comparison to a human. I would be so frightened to have one of these approach me.
The size of the Anomalocaris in comparison to a human
What are Anomalocaris?
These animals were first discovered 1886. Originally, three sections of the animal was discovered and each section was thought to be a different organism. The arms were assigned to be a crustacean, the mouth a jellyfish and the body that of a sponge.
This predator that ruled the oceans during the Cambrian Era, stalked the seas over 540 million years ago. Early fossils were found in British Columbia, Australia, China, Greenland and the USA (Utah). Many researchers regard this creature as an abnormal shrimp probably the largest animal in the Burgess Shale.
It's length is approximately 60 cm long (some reached 6 feet as discovered in China). It has large complex eyes, circular mouth, an oval-shaped head and in the front it's feeding appendages look like combs. To swim, there were 11 pairs of lobes underneath its body, swimming much like a manta ray and was devoid of any type of walking appendages.
It is believed that the Anomalocaris dined on hard-shelled animals, specifically trilobites, as it was discovered in the trilobite beds of the Ogygopsis Shale. There is very strong evidence that they did eat the trilobites through their fossilized fecal pellets containing trilobite parts that were so large that it was determined that only the Anomalocaris was the only creature that was large enough to eat these animals. The round and cylindrical mouth was located underneath the head and contained many tiny teeth that faced inward like sharks. Like the modern shrimp, food was captured by the feeding appendages curling it up and bringing it to the mouth. As it may seem difficult for this prehistoric shrimp (because of the lack of mineralised tissue and unlikely to penetrate the hard shells), to eat these hard-shelled animals, it has been suggested that the creature grabbed their prey in their jaws and using their appendages rock the animal back and forth rupturing the exoskeleton to gain control of the innards. It this was true, it is noted to suggest that perhaps this gave rise to the trilobite behavioral evolution of rolling up to avoid flexing until snapping. Still the jury is out whether Anomalocaris did consume these hard-shelled animals or perhaps sucked on smaller, soft-bodied organisms.
Artist rendition of what Anomalocaris may have looked like
Whatever the case may be, these predators were one of the largest, if not the largest, predator in the sea during the Cambrian Era. They along with the anomalocarid family became extinct after the Mid-Cambrian Period due to the possibility of climatic changes or the emergence of more super predators. They are an interesting animal to read about.
Sponge is a simple word used to discuss these animals. Sponges are known by scientists as Porifera. In Latin, this means "pore-bearing." The pores, or tiny holes, in the skin of a sponge water in so that the sponge can extract oxygen and food for all of its cells to stay alive. The water passes by the mesohyl, also called the mesenchyme which contains cells and the sclerocytes. Sclerocytes make spicules. After the water is filtered, it is pushed out of the sponge. First it goes to a hollow area called the spongocoel, which is a large, empty cavity. Sponges contain one large hole at the top of their bodies, known as an osculum, and they also have smaller holes on the sides known as ostia. With so much water flowing in and out of a sponge every day, sponges in the Caribbean Sea can filter the entire sea in just one day. That's pretty impressive for an animal that was thought to be a plant until the year 1765!!!
Scientists believe that sponges were the first animals to be alive. The ancestors of today's sponges were alive billions of years ago. Sponges have looked the same for millions of years. They are the most simple of all animals, with no brain or organs, but they have been helping mankind and nature for as long as they have been on the planet.
Sponges may seem to be plants, but they are really just primitve, simple animals. They are not animals like humans because they only have cells. Cells are the tiniest parts of the body, and you can't even see them. Each cell in a sponge has a special job, and when cells of the same type come together, they make tissues. Tissues create organs, but sponges don't have any organs. That means no brain, eyes, hearts, etc. However, despite all that is set against them, they always manage to stick together. While their spicules, tiny needles that stick out from the sponge, hold them together, sponges also have another special way to stick together. If you had a sponge in a salt-water aquarium and break it up into thousands of pieces, the cells would come back together again in the exact same shape within several hours.
In 2008, Gordon Love of the University of California Riverside discovered fossil traces in an oil field on the Arabian Peninsula. They became the oldest evidence yet of animals, pushing back the known origins of higher life to more than 635 million years ago. They were unearthed in Oman and reveals that tiny sea sponges were abundant 635 million years ago, long before most of the planet's other major animal groups evolved, according to a new analysis.
Love’s team identified the fossils while analyzing sedimentary deposits mined by Oman’s national oil company. The sediments date to the last stages of the the aptly-named Cryogenian period after a deep freeze.
What life may have looked like in the Ediacaran Sea
This early life hardly looked like us, but some of the so-called demosponges can be sizable today. Demosponges still make up 90 percent of all sponges on Earth and 100 percent of Earth's largest sponges, including barrel sponges, which can be larger than an old-style phone booth.
The ancient demosponges — probably measuring across no more than the width of a fork tine — were pinned down via fossilized steroids, called steranes, which are characteristic of the cell membranes of the sponges, rather than via direct fossils of the sponges themselves.
Class Hexactinellida (Glass Sponges)These are deep-sea sponges. They lack an epidermal covering, and their skeletons are composed of spicules of silica. The spicules, which often form a latticework, have six points or some multiple thereof. Many hexactinellids are called "glass sponges." Hexactinellids were the first group of sponges to develop, but as said before, many scientists do not believe that they are sponges at all. Oddly enough, they have electric receivers on their spicules which can conduct electricity!
Body plan with lattice of spicules, flagella in chambers of pores
Glass sponges are pale in color and are cup- or basket-shaped. The spongocoel is large, and the osculum is covered by a grillwork of fused spicules. When the living tissue is removed, the cylindrical skeletons often have the appearance of spun glass. The glass sponge known as Venus's-flower-basket (Euplectella) supplies a home for certain shrimps that become trapped by the lattice of spicules. The body plan of Hexactinellida is between syconoid and leuconoid.Glass sponges are different from other sponges in a variety of other ways. For example, most of the cytoplasm is not divided into separate cells by walls but forms a syncytium or continuous mass of cytoplasm with many nuclei (e.g., Reiswig and Mackie, 1983). Like almost all sponges, the hexactinellids draw water in through a series of small pores by the whip like beating of a series of hairs or flagella in chambers which in this group line the sponge wall.
The Venus's Flower Basket
Hexactinellids are, typically, limited to the deep sea with the result that few people have seen them or studied them. An exception may be the “Venus’s Flower Basket” A pair of shrimp remain protected together inside. The sponge together with the imprisoned pair of shrimp is often given as a gift at weddings in Japan and the Philippines to signify a long relationship.
Reef-building glass sponges were once thought to have been extinct for 100 million years. But a new live cluster of the organisms has been discovered off the west coast of the US - only the second known to exist.
Furthermore, unlike the other known glass sponge reefs in Canada, the US reefs appear to be fuelled by methane. Paul Johnson, of the University of Washington, US, led the expedition that discovered the reefs on 10 June off the coast of Washington state. He says they are oases of marine life, several hundred feet across, and surrounded by uninhabited expanses of seafloor.
Glass Sponge Reef location
Glass sponge reefs were common during the “Age of Dinosaurs”, but were unknown since that time. Some were being destroyed by trawling. They have recently been designated as no trawling areas by Fisheries and Oceans Canada; but full Marine Protected Area status is needed to ensure that they remain intact. Glass sponges occur mainly on muddy sea bottoms at great depths and due to their delicate nature are broken and shattered whenever there is trawling along the muddy bottom.
Sponges may seem to be plants, but they are really just primitive, simple animals. They are not animals like humans because they only have cells. Cells are the tiniest parts of the body, and you can't even see them. Each cell in a sponge has a special job, and when cells of the same type come together, they make tissues. Tissues create organs, but sponges don't have any organs. That means no brain, eyes, hearts, etc. However, despite all that is set against them, they always manage to stick together. While their spicules, tiny needles that stick out from the sponge, hold them together, sponges also have another special way to stick together. If you had a sponge in a salt-water aquarium and break it up into thousands of pieces, the cells would come back together again in the exact same shape within several hours.
How A Sponge Takes In Food
The diet of sponges consist of bacteria and other organic matter. Some sponges feed on green algae, dinoflagellates, and cyanobacteria. To get the bacteria and other organic matter, water flows through the pores and provides the sponge with its food. They are known as “suspension feeders” and collect nutrients from the water through their choanocyte cells. About 90% of the bacteria in the water that flows through them (which is pushed through with the help of beating flagella) is absorbed as nutrients. The choanocyte cells consist of a flagella surrounded by a collar cell. As the choanocyte cells uptake the food, the flagella (a cellular 'tail' that aids in motion) creates a water current and the collar cells ingest the food. The choanocytes take up the nutrients through phagocytosis. Phagocytosis is the uptaking of large food particles. Sponges also consist of amoebocytes, which along with discarding of foreign bodies also are responsible for uptaking nutrients from the water and from choanocyte cells. Once amoebocytes uptake the nutrients, they digest these nutrients and then transport the nutrients to other cells.
• Porocytes- doughtnut-shaped cells that align the body wall.
• Choanocytes- flagellated cells that aid in circulation, water movement, and digestion.
• Amoebocytes- cells that are important in getting rid of foreign bodies.
• Mesohyl- a part of the sponge that separates the two layers of the sponge.
• Spongocoel- the mid- cavity (compartment) of the sponge.
• Osculum- larger openings within the sponge where water is passed through. (More complex sponges have more osculum)
• Epidermis- tightly packed cells aligning the sponge. Spicules- makes up the skeleton of the organism, they provide the support need to keep the pores open. Spicules are made of calcium carbonate and silica, or the organic substance spongin.
How Do Sponges Reproduce?
Sponges are hermaphrodites, which means that they have male and female reproductive parts. Sponges also produce female and male gametes (sperm and egg). Egg and sperm arise from the choanocyte and amoebocyte cells of the sponge. The eggs of sponges are housed in the mesohyl. The sperm is carried out through the water current that circulates the sponge. Sperm are created, concentrated and sent out the excurrent openings, sometimes in masses so dense that the sponges appear to be smoking. The temperature of the water that the sponges live in usually determine when the sponges release the sperm. These sperm are then captured by female sponges of the same species. When the sperm enters a collar cell of a neighboring sponge, the collar cell loses its collar, transforming the cell into a specialized cell that brings the sperm to the eggs. Fertilization (the combination of egg and sperm) occurs in the mesohyl of the sponge. Sponges can also reproduce asexually (by not having sex) as pieces of the sponge break off and are then repaired. Some species will make internal buds, called gemmules, that can survive in extreme conditions which the rest of the sponge cannot survive in. Some sponges reproduce asexually.
Choanocytes and Amoebocyte location of eggs and sperm for reproduction
They and their larvae, gobble up Aphids (genus Aphis) as though there were no tomorrow. If you find lacewings indoors during autumn and winter; leave them to over-winter in your home.
Lacewing eggs are normally laid on thin sticks. Eggs laid on thin sticks is believed that it helps to prevent cannibalism. Lacewing larvae are active predators.
Green Lacewing (genus Chrysopa) Larvae are most effective in humid areas including greenhouses and interior gardens. They are considered a very good natural control of a number of insects, including:
Aphids (Greenfly) & Gnats (Blackfly)
Spider mites and Red mites
Thrips, whiteflies, long-tailed mealybugs
Eggs of leafhoppers, moths and leafminers
Small caterpillars, beetle larvae and tobacco budworms
Greenflies
Aphids (greenflies) are sucking insects which draw great quantities of sap, causing leaves and stems to become distorted. This distorted growth may be mistaken as herbicide injury. Some plant sap is excreted as honeydew, which makes the plant sticky. Sidewalks, cars, and patio furniture may become wet with honeydew. A sooty mold often grows in the honeydew and blackens stems, leaves and any other surface. Aphids may transmit plant pathogens.
Blackfly Gnat
There are over 1,800 known species of black flies (of which 11 are extinct). Most species belong to the immense genus Simulium. Most black flies gain nourishment by feeding on the blood of other animals, although the males feed mainly on nectar. They are usually small, black or gray, with short legs, and antennae. They are a common nuisance for humans.
A very special disease caused by gnats is a special kind of paralysis starting at the ankle level and progressing to knee level. This is due to the toxins secreted by the bug which many times keeps attached to the host body.
Lacewing Eggs
After a few days, the eggs hatch and tiny larvae emerge which are also known as" aphid lions" because of their voracious appetite. The larvae have sickle-shaped jaws (mandibles) with which they pierce prey and suck out body juices. Adults have chewing mouthparts. Adults are poor fliers, active at night and feed on pollen, nectar and honeydew (the exudate of aphids and other sucking insects). Some species are predaceous as adults to a limited extent.
The larvae, called "aphid lions", are extremely carnivorous and predaceous on many soft-bodied insects and mites, including insect eggs, thrips, mealybugs, immature whiteflies and small caterpillars. Larvae have sickle-shaped jaws that contain tubes with which they can inject prey with a paralyzing venom and then suck out the body fluids. They can consume over 200 aphids or other prey per week. There is no other better predator known to consume vast quantities of eggs and the soft bodies of aphids, mealy-bugs, spider mites, leafhopper nymphs, caterpillar eggs, scales, thrips, and white-flies. The lacewing larvae attack the eggs of most pests and, if the bodies are not to hard and fast moving, will attack the adult pest stage as well.
During the Eocene, continents were in different locations from those they occupy today
Here's an interesting story that BBC covered in the last few days about these wonderful animals and their migration that I found fascinating. I have always found the ant to be a curious insect. So, I will be covering this small invertebrate quite a lot in my blog. Without further adieu, here comes another story on the ANT (Titanomyrma lubei).
A giant ant growing over 5cm (2in) long crossed the Arctic during hot periods in the Earth's history, scientists say, using land bridges between continents.
The ant, named Titanomyrma lubei, lived about 50 million years ago and is one of the largest ant species ever found.
Fossils were unearthed in ancient lake sediments in Wyoming, US.
Hummingbird and ant fossil showing size
Writing in the Royal Society Journal Proceedings B, a Canadian-US team shows that giant ants, now and then, almost always live in hot climates. The new species appears very similar to fossils found in Germany and in the Isle of Wight in southern England dating from the same period.
We don't have any [fossils of] workers from this new species, we only have a queen," said Bruce Archibald from Simon Fraser University in British Columbia. "It would have been very impressive - the one in Germany was estimated to have a body weighing as much as a wren, and this would have been of similar size," he told BBC News. Little is known about how these ants lived or what they ate - but wings are present on the fossils. They are found, in Europe and now in Wyoming, close to plants known to thrive only in temperatures around 20C (70F).
Road much travelled
The Eocene, 56-34 million years ago, was punctuated by periods when the Earth's temperature rose higher than it is today, probably because of the release of greenhouse gases such as methane into the atmosphere.
And the researchers believe that the giant ants must have made a journey from Europe to North America - or vice versa - during one of these "hyperthermals".
"There was plenty of life transferring between Europe and North America at that time - mammals, trees - all sorts of things," said Dr Archibald.
"And plenty of insects are similar between British Columbia and Denmark - but they could have lived in a cooler climate and crossed at any time.
"This is the first example we have of something that would have needed warmth in order to make the crossing."
The land bridges across the Arctic would have seen a temperate climate for most of the Eocene, rising during the hyperthermals.
During the course of the research, the team mapped the locations of all ant species, extinct or contemporary, growing longer than 3cm (1.2in).
They found that virtually all are associated with tropical temperatures, although the reason why remains a mystery.
The biggest extant equivalents are the driver ants of the Dorylus genus, found in Central and East Africa, which can also grow to 5cm long. (They are the most dangerous ants in the world)
Do you enjoy gardening like I do? Well, I used to never enjoy getting out there to turn soil, rake grass and trim branches or pop off dead blossoms. But, over the last few years, I can't wait to get out to do that because I know of the rewards I will get when the afternoon sun heats up the air bringing forth beautiful blooms and a beautiful green carpet where I can sit myself down and enjoy my park like surroundings. It will also bring more bees, butterflies and insect eating birds and hummingbirds to my place of solitude and with the air alive and serenading birds it brings rest and relaxation.
However, after studying entomology, plant physiology and phycology at HSU, I have a new knowledge and respect for all those critters that are best studied under a microscope. Gardening is a great hobby and brings a lot of enjoyment in the end, but it can also cause physiological affects to the human body, if the gardener is not careful when working with soils, roots, branches and the like. Parasitic animals are alive and active in those soils, on roots and on branches. When first looking at a cup of soil there appears nothing on the surface. But, put that same cup under a dissecting microscope and that top soil comes alive as it quivers and shakes with hundreds of minute and parasitic animals living their life in that habitat.
What is interesting that I never once ever really questioned where those 'wild' animals go to rid themselves of their wastes. I do know by the rancid odor amongst my flowers and bushes that some feline came and either sprayed or used my soil as a litter box. But, where do the raccoons, opossums, occasional fox, skunks and other smaller mammals go to relieve themselves? Well, why not where that cat or dog just went? And, so there parasitic animals await the next warm blooded hand to attach themselves to move from the outside to get to inside through a small cut that the owner wasn't aware of. And, those parasites cause a heap of trouble for your intestines and body organs and not to mention those specific parasites that can stay a life time and make their way to the brain bringing death to the host. But, do you have to eat that soil to get infected?
Eating dirt doesn’t necessarily mean picking up soil and deliberately putting it in your mouth: we accidentally ingest dirt when we put dirty fingers in our mouths, or eat uncooked vegetables that have not been very thoroughly scrubbed. Soil particles may even be picked up by the wind and inhaled.
Put simply, worm eggs and protozoan cysts and oocysts can’t be present in soil unless animals put them there. The commonest ones are passed in the stools of infected animals. If they are present in soil, it means that animal feces have contaminated the ground.
Nematodes
Nematodes are found in almost all habitats, but are often overlooked because most of them are microscopic in size. For instance, a square yard of woodland or agricultural habitat may contain several million nematodes. Many species are highly specialized parasites of vertebrates, including humans, or of insects and other invertebrates. Other kinds are plant parasites, some of which can cause economic damage to cultivated plants. Nematodes are particularly abundant in marine, freshwater, and soil habitats. One study in Colorado estimated that nematodes consumed about as much grass as a prairie dog colony.
Soil is an excellent habitat for nematodes, and 100 cc of soil may contain several thousand of them. Because of their importance to agriculture, much more is known about plant-parasitic nematodes than about the other kinds of nematodes which are present in soil. Most kinds of soil nematodes do not parasitize plants, but are beneficial in the decomposition of organic matter. These nematodes are often referred to as free-living nematodes. Juvenile or other stages of animal and insect parasites may also be found in soil. Although some plant parasites may live within plant roots, most nematodes inhabit the thin film of moisture around soil particles. The rhizosphere soil around small plant roots and root hairs is a particularly rich habitat for many kinds of nematodes.
Nematodes are roundworms in the Phylum Nematoda. Various authorities distinguish among 16 to 20 different orders within this phylum. Only about 10 of these orders regularly occur in soil, and four orders (Rhabditida, Tylenchida, Aphelenchida, and Dorylaimida) are particularly common in soil. More than 15,000 species and 2,200 genera of nematodes had been described by the mid-1980s. Although the plant-parasitic nematodes are relatively well-known, most of the free-living nematodes have not been studied very much. Therefore there is a high probability that most soil habitats will contain nondescribed species of free-living nematodes. Identification of these groups is extremely difficult, and there are only a few nematode taxonomists in the world who can formally describe new species of free-living nematodes to science. Therefore most nematode ecologists identify soil nematodes only to family or genus.
Soil-inhabiting nematodes can also be classified according to their feeding habits. This classification is particularly useful to ecologists in understanding the positions of nematodes in soil food webs. Several important feeding groups of nematodes commonly occur in most soils. In addition, algivores (feed on algae) and various stages of insect and animal parasites occasionally are found in soil. The nematode feeding groups are called trophic groups by some authors.
Bacterivores. Many kinds of free-living nematodes feed only on bacteria, which are always extremely abundant in soil. In these nematodes, the "mouth", or stoma, is a hollow tube for ingestion of bacteria. This group includes many members of the order Rhabditida as well as several other orders which are encountered less often. These nematodes are beneficial in the decomposition of organic matter.
Fungivores. This group of nematodes feeds on fungi and uses a stylet to puncture fungal hyphae. Many members of the order Aphelenchida are in this group. Like the bacterivores, fungivores are very important in decomposition. Predators. These nematodes feed on other soil nematodes and on other animals of comparable size. They feed indiscriminately on both plant parasitic and free-living nematodes. One order of nematodes, the Mononchida, is exclusively predacious, although a few predators are also found in the Dorylaimida and some other orders. Compared to the other groups of nematodes, predators are not common, but some of them can be found in most soils. Omnivores. The food habits of most nematodes in soil are relatively specific. For example, bacterivores feed only on bacteria and never on plant roots, and the opposite is true for plant parasites. A few kinds of nematodes may feed on more than one type of food material, and therefore are considered omnivores. For example, some nematodes may ingest fungal spores as well as bacteria. Some members of the order Dorylaimida may feed on fungi, algae, and other animals. Unknown. Since free-living nematodes have not been studied very much, the food habits of some of them are unknown. The microscopic size of these animals presents additional difficulties. For example, it can be very difficult to distinguish whether a nematode is feeding on dead cells from a plant root or on fungi growing on the cell surface. Sometimes a nematode showing this feeding behavior may be classified simply as a root or plant associate.
Free-living nematodes are very important and beneficial in the decomposition of organic material and the recycling of nutrients in soil. Nematode bacterivores and fungivores do not feed directly on soil organic matter, but on the bacteria and fungi which decompose organic matter. The presence and feeding of these nematodes accelerate the decomposition process. Their feeding recycles minerals and other nutrients from bacteria, fungi, and other substrates and returns them to the soil where they are accessible to plant roots.
There are 15,000 known species of roundworms, also known as nematodes, and another half a million roundworms waiting to be discovered and studied. That would make roundworms the second most diverse group of animals. The first would be arthropods. Certain species of roundworms can lay more than 200,000 eggs in one day. Most species of roundworms have separate sexes, but there are a few that have both male and female gonads.
Most parasitic roundworm diseases are transmitted to humans through soil. There can be thousands of roundworms in one handful of soil. The roundworms can be ingested by unwashed hand to mouth or the roundworms can enter through the skin. Some of the most common parasitic roundworms in humans are: Enterobius Vermicularis (Pinworms), Ascaris Lumbricoides (Large Intestinal Roundworms), Trichuris Trichiura (Whipworm), Necator and Ancylostoma (Hookworms), Strongyloides Stercolralis, and Trichinella Spiralis. Other roundworms affecting humans are: Dracunculiasis (Guinea Worm), Wuchereria Bancrofti, Brugia Malayi, Brugia Timori, Toxocara Canis, and Toxocara Cati. Wuchereia Bancrofti, B. Malayi, and B. Timori cause Lymphatic Filariasis (Elephantiasis). Toxocara Canis (dog roundworms) and Toxocara Cati (cat roundworms) cause a disease called Toxocariasis.
Once the eggs are ingested in the body, the roundworm larvae travels through the liver, lungs, and other organs. In most cases, these "wandering worms" cause no symptoms or apparent damage. It is when the larvae moves into the nerves or lodge themselves in the eye that they can cause permanent damage or even blindness. This condition is called visceral larva migrans.
Nematode Life Cycle
Finally, make sure that you practice good hygiene habits after working with your soil and other gardening activities. After all, to better enjoy the outside and all your work is better out there than inside battling the disease that can come about once infected by those nematodes.
A spore-bearing fungal parasite emerges from the digested corpse of a bdelloid rotifer. These freshwater invertebrates present an evolutionary puzzle because they have reproduced without sex for millions of years, but have not been driven extinct by relentlessly coevolving parasites.
Bdelloid rotifers (pronounced DELL -- oyd ROW-tiff-ers) are tiny, freshwater invertebrates that have long puzzled scientists because, as completely asexual animals, they should have been extinguished by parasites and pathogens long ago in evolutionary time. Instead, the bdelloids have proliferated into more than 450 species. Asexual animals like rotifers reproduce by cloning and this makes for a fixed gene pool.
They haven't had sex in some 30 million years, but some very small invertebrates named bdelloid rotifers are still shocking biologists -- they should have gone extinct long ago. Cornell researchers have discovered the secret to their evolutionary longevity: these rotifers are microscopic escape artists. When facing pathogens, they dry up and are promptly gone with the wind. These animals have evolved a way to avoid parasites and pathogens by drying up and blowing away," said Paul Sherman, Cornell professor of neurobiology and behavior, who wrote the paper with lead author Chris Wilson, a Cornell doctoral candidate in Sherman's lab. After drying up, bdelloids come back to life when re-exposed to fresh water. The Cornell study is featured on the cover of the Jan. 29, 2010 issue of Science.
Many scientists believe that the function of sex itself is to shuffle genes around. They theorize that the fresh genetic combinations that which sex provides allow sexual animals to fend off relentlessly evolving parasites and pathogens. The discovery that bdelloids can desiccate and wisp away with the wind helps resolve the mystery of their ancient asexuality and success.
"It also helps answer one of the deepest puzzles in evolutionary biology -- why sex is nearly ubiquitous," said Wilson.
To study the bdelloids' adaptations, Wilson infected populations of rotifers with deadly fungi and found that they all died within a few weeks.
He then tried drying out other infected populations for varying lengths of time before rehydrating them. He found that the fungi were far more sensitive to dehydration than the rotifers. The longer the infected populations remained dried out, the more successful they were at completely ridding themselves of fungi and eluding death.
In a second wave of experiments, Wilson placed dried, fungus-infected rotifers in a wind chamber. The scientists observed that the rotifers were able to disperse without the fungi and establish parasite-free populations. After just seven days of blowing around, there were as many fungus-free rotifer populations as there were after three weeks of dehydration without wind. So, by drying and drifting passively on the wind -- sometimes for hundreds of miles -- bdelloids can continually establish new, uninfected populations.
"These animals are essentially playing an evolutionary game of hide and seek," said Sherman. "They can drift on the wind to colonize parasite-free habitat patches where they reproduce rapidly and depart again before their enemies catch up. This effectively enables them to evade biotic enemies without sex, using mechanisms that no other known animals can duplicate."
(The study was supported by Sigma Xi, the U.S. Department of Agriculture, Cornell and Cornell's Stephen H. Weiss Presidential Fellowship Fund. Cornell University (2010, February 8). Like escape artists, rotifers elude enemies by drying up and -- poof! -- they are gone with the wind. http://www.sciencedaily.com/releases/2010/01/100128142130.htm)
The ants may go marching one by one, but they end up forming a superstructure of thousands -- and together they can form a raft that stretches the boundaries of the laws of physics, according to new research released today.
Ants have exoskeletons that are naturally hydrophobic, or water repellant. A single ant can walk on water because of the buoyancy of the air bubbles trapped next to its body, and the water's own surface tension. However, when thousands of ants stand on top of each other, their multiplied weight should cause them to sink. But for years, biologists have observed fire ant colonies floating down flood plains and rivers in their native South America.
For the first time, a group of engineers has attacked the question of ant flotation from a physics perspective. Ants float as a group because they can harness the power of nearby air bubbles. Grasping each other's mandibles or front legs with a force 400 times their body weight, the ants are able to trap small pockets of air between them -- like a group floatation device.
"The ants are so tightly knit together, that air pockets form between the water and the ants, and water cannot penetrate through any part," said Nathan Mlot, a graduate student at the Georgia Institute of Technology in Atlanta and one of the study's authors.
The bottom layer of ants rests on top of the water's surface, and others pile on above them. Even when they do get submerged, the pockets of air bring them back to the surface quickly -- and allow them to breathe. When they get submerged, the ants flex their muscles in unison to form a tighter weave.
To understand exactly how the structure worked, the researchers took a raft of several thousand ants and dropped it in liquid nitrogen, immediately freezing it. Then they were able to look at the structure on an ant-by-ant level under an electron-scanning microscope. "We were surprised at just how waterproof raft was -- its ability to repel water and keep afloat," said Mlot.
What if you want to drown the ants? Just add soap to the water, which greatly reduces its surface tension of water and sinks the raft, said Mlot. "With soap, the ants will drown within a matter of seconds, whereas they can survive for days or even weeks on the raft otherwise."
To test some of the behavioral dynamics inside the pancake-shaped raft, the researchers painstakingly picked ants one by one from the top of the structure. Soon, a new one would climb from the bottom to keep the raft the same thickness.
"We know that self-assembly and self-healing are attributes of living organisms, and we have seen that ant rafts develop these on a macro scale," said Mlot. The study was published today in the journal Proceedings of the National Academy of Sciences.
"Each ant does one tiny job, but they can build these incredible structures," said Kenneth Ross, an entomologist with the University of Georgia who was not involved in the work. Ross says that the rafts include not only worker ants, but also the queen and her brood -- the reproductive cells of the giant superorganism. From what he has seen in his research, the queen usually stays in the center of the raft, with an even tighter ball of ants around her.
This level of social organization isn't common, said Joshua King, an insect ecologist at the Central Connecticut State University, in New Britain. "This study reinforces how unique the collective behaviors of social insects are when compared to other animals."
This type of research could eventually help in many fields, from making a better rain jacket to building robots that can think. When the ants link up their mandibles and legs, they form a highly waterproof weave, which could be the basis for next-generation materials for lifejackets or boats. In addition, social insects like ants have long been the inspiration for autonomous robotics that could link up to build a larger structure.
"Ants are like little computers, acting on a few simple rules of engagement," said Mlot.
