Nematode - The Round Worm

 

 

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.

Nematodes inside a grub (top of body)

Healthy and nematode-infected white grubs

Feeding Habits

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.




For more information:
http://www.dowagro.com/soil/products/tomatoes-se/attacking.htm
http://www.my-grape-vine.com/blog/the-role-irrigation-has-on-fungus-diseases-and-nematodes-in-vineyards/
http://classes.seattleu.edu/biology/biol235/hodin/nematodePriapulidGroup/nematodes/parasite.htm
http://www.fcps.edu/islandcreekes/ecology/predatory_nematode.htm
http://www.firehow.com/2011010923084/how-to-control-nematodes-in-a-vegetable-garden.html

Like Escape Artists, Rotifers Elude Enemies by Drying Up and -- Poof! -- They Are Gone With the Wind

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)

Fire Ants Assemble as a 'Super-Organism' (from Fox News)

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.