by Rick O'Connor | Aug 23, 2024
Roundworms differ from flatworms in that… well… they are round. You might recall from Part 1 of this series that flatworms were flat which helps with exchange of materials inside and out of the body. Flatworms were acoelomates – they lack an interior body cavity and thus lack internal organs. So, gas exchange (etc.) must occur through the skin. And a flat body increases the surface area in order to do this more efficiently.
A common nematode.
Photo: University of Florida
But roundworms are round, which reduces this surface area and reduces the efficiency of material exchange through the skin. Though gas exchange through the skin does happen, it is not as efficient. So, there is the need for internal organs and that means there is a need for an internal body cavity to hold these organs. But with the roundworms there is only a partial cavity, not a complete one, and the term pseudocoelomate is used for them. Though the round body has adaptations to deal with gas exchange, it is a better shape for burrowing in the soil and sediment.
There are about 25,000 described species of roundworms, though some estimate there may be at least 500,000. They are placed in the Phylum Nematoda and are often called nematodes. Nematodes live within the interstitial spaces of soil, sediment, and benthic plant communities. They have been found in the polar regions, the tropics, the bottom of the sea, and in deserts – they are everywhere. They are usually in high numbers. One square meter of mud from a beach in Holland had over 4,000,000 nematodes. Scientists have estimated that an acre of farmland may have at least 1 billion of them. A decomposing apple on the ground in an orchard had about 90,000 nematodes. So, they are found everywhere and usually in great abundance. There are parasitic forms as well and they attack almost all groups of plants and animals. Food crops, livestock, and humans have made this group of nematodes a concern in our society.
Like many pseudocoelomates, nematodes have an anterior end with a mouth, but no distinct head – rather two tapered ends. Most of the free-living nematodes are less than 3mm (0.1in), but some soil nematodes can reach lengths of 7mm (0.3in) and there are marine nematodes that can reach 5cm (2in.) – it is a group of small worms.
Roundworms usually need water in order to move, even the soil species. They typically wriggle and undulate, similar to a snake, when moving and under a microscope they wriggle quite fast. In aquatic habitats they may swim for a short distance, and a few terrestrial species can crawl through dry sand.
Marine Nematode – Dr. Roy P. E. Yanong, UF/IFAS Tropical Aquaculture Lab
Many free-living nematodes are carnivorous and feed on tiny animals and other nematodes. Some feed on microscopic algae and fungi. Some terrestrial species pierce the roots of plants and digest the material within. Many marine species will feed on detritus lying on the seafloor. The carnivorous species may possess small teeth, and many have a stylet they can use to pierce prey or the plant root to access food. The mouth leads to a long digestive tract and eventually an anus – nematodes have a complete digestive tract.
The brain is basically a nerve ring near the head that leads to numerous nerve chords that run the length of the body. Sensory cells are most associated with the sense of touch and smell.
Having separate sexes is the rule for nematodes, but not for all. Males are usually much smaller and usually have a hooked posterior end which they use to hold the female during mating. 50-100 eggs are usually produced and laid within the environment.
Farmers and horticulturists are familiar with these free-living nematodes, but it is the parasitic ones that are most known to the general public. There are many different forms of parasitism within nematodes. Dr. L.H. Hyman categorized them as follows:
- Ectoparasites that feed on the external cells of plants – using their stylet to pierce the plant tissue and remove nutrients.
- Endoparasites of plants. Juveniles of some nematodes enter plants and feed on tissue. This can cause tissue death and gall-like structures.
- Some free-living nematodes, while juveniles, will enter the bodies of invertebrates and feed on the tissue when the invertebrate dies.
- Endoparasites within invertebrates as juveniles, but the adult stage is free-living.
- Some are plant parasites as juveniles and animal parasites as adults. The females live within the bodies of plant eating insects, where they give birth to their young. When the insects pierce the plant tissue, the juveniles enter the plant and begin feeding on it. When they mature into adults, they re-enter the insects and the cycle begins again.
- Those that live within animals. The eggs, or newly hatched young, may be free-living for a short period, where they find new animal hosts, but the majority of the life cycle occurs within the animal. Many known to us infect dogs, cats, pigs, cattle, horses, chickens, fish, and humans.
Heartworms, pinworms, and hook worms are names you may have heard. For dog nematodes, the eggs are released into the environment by the dog’s feces. Another dog eats this feces and becomes infected.
The nematode known as Ascaris lumbricoides is the most common parasitic worm in humans. It has been estimated that almost 1 billion people are infected with it. Female Ascaris release developing eggs into the environment via human feces. Other humans become infected after swallowing food or water containing the eggs. Once inside the human, the eggs hatch and penetrate the tissue moving into the heart and eventually the lungs. From here they crawl up the trachea inducing a coughing response which is followed by a swallowing response that moves the developing juvenile worm into the esophagus and eventually back to the intestines where the cycle begins again. Infections of this worm are more common where sanitation systems are not adequate and/or human feces are used as a fertilizer.
Hookworms are another human parasite that feed on blood and can cause serious infections in humans due to blood and tissue loss. Fertilized eggs of this worm are laid in the environment and re-enter new human host as developing juveniles by penetrating their skin. Once in the new host the developing worms are carried to the lungs via the circulatory system and work their way into the pharynx, are swallowed, and eventually end up in the intestine. Not all hookworm juveniles penetrate through the skin but rather enter the body when the person unknowingly consumes human feces. This can happen from not washing your hands or food (if human waste is used as fertilizer). Pinworms and whipworms are other nematodes that have similar life cycles. In Asia there are some nematodes that are passed to humans by biting insects.
The roundworm known as the nematode is a common issue for farmers, horticulturists, and as a parasite in some parts of the world. Their lifestyles, while being a potential problem for us, have been very successful for them. In the next edition in this series, we will learn more about the most advanced worms on our planet – the segmented worms. We will begin with the polychaetes.
References
Barnes, R.D. (1980). Invertebrate Zoology. Saunders Publishing. Philadelphia PA. pp. 1089.
Ascaris lumbricoides. 2024. Wikipedia. https://en.wikipedia.org/wiki/Ascaris_lumbricoides.
by Rick O'Connor | Aug 10, 2024
I bet that for most of you, this is not only a worm you have never seen – it is a worm you have never heard of before. I learned about them first in college, which was almost 50 years ago, and have never seen one. But, other than the earthworm, the world of worms is basically hidden from us.
A nemertean worm.
Photo: Okinawa Institute of Science
Nemerteans are a group of about 1300 species in the Phylum Nemertea and are often called ribbon or proboscis worms. They do possess a proboscis used to capture prey. Most are marine and live on the bottom both near the beach and a great depth. They are more temperate than tropical and do have a few parasitic forms.
Adult Nemertea Worms – Terra C. Hiebert, PhD, Oregon University
In appearance they resemble flatworms but are larger and more elongated. Most are less than 20cm (8in) but some species along the Atlantic coast can reach 2m (7ft). The head end can be lobed or even spatula looking. Some species are pale in color and others quite colorful. Most nemerteans move over the substrate on a trail of slime produced by their skin. Some species can swim.
As mentioned, the proboscis is used to capture prey. It is a tube-like structure held in a sac near the head. When prey is detected, they can launch the proboscis out and over the victim. Sticky secretions help hold on to the prey while they ingest. Many species are armed with a stylet, dart, that is attached to the proboscis and is driven into the prey like a spear. From there toxins, secreted from the base of the proboscis are injected into the prey.
For many species the proboscis is connected to the digestive tract via a tube, there is no true mouth, but they do possess an anus. They are all carnivorous and feed on a variety of small living and dead invertebrates. Their menu includes annelid worms, mollusk, and crustaceans.
Nemerteans do possess a brain and most find their prey using chemoreception, though some species must literally bump into their prey to find it. They have multiple eyes that can detect light, and, like the true flatworms, they are negatively phototaxic. They are nocturnal by habitat and is probably why most of us have never seen one.
Many nemerteans, particularly the larger ones, have a habit of fragmenting when irritated, creating new worms. Most species have separate sexes and fertilization of the gametes is external (fertilization occurs in the environment).
Nemerteans are an interesting group of semi-large, sometimes toxic, hunters who prowl through the marine waters at night hunting prey. Seen by few, maybe one evening, while exploring or floundering, you may see one.
In Part 3 we will begin to explore a group of worms that are more round than flat. The Gastrotrichs.
Reference
Barnes, R.D. (1980). Invertebrate Zoology. Saunders Publishing. Philadelphia PA. pp. 1089.
by Rick O'Connor | Aug 10, 2024
I was recently conducting a survey for diamondback terrapins from my paddleboard in a small estuarine lagoon within the Pensacola Bay System. Even if we do not find our target species during these surveys – I, and our volunteers, see all sorts of other cool wildlife. On this trip I was treated to nesting osprey, a kingfisher, large blue crabs, and even a swimming eel. But one neat encounter was the numerous stingrays.
The Atlantic Stingray is one of the common members of the ray group who does possess a venomous spine.
Photo: Florida Museum of Natural History
They were lying in the sand and grassbeds, lots of them, and they all seemed to be of one species – the Atlantic stingray. My brain immediately went to “breeding season”, but when I checked the literature, I found that it was not breeding season, but pupping season – the babies were being born.
Atlantic Stingray (Dasyatis sabina) are true stingrays in the family Dasyatidae. This means they do possess the replaceable serrated venomous barb that makes these animals so famous. They are one of the smaller members of this family. Females can reach a disk width of two feet while the smaller males will only reach about one foot. Atlantic stingrays are a warm water species, migrating if they need to find suitable temperatures. They have been found in water as deep as 80 feet but are more common in the warmer shallower waters near shore. They are very common in our estuaries and being euryhaline (they tolerate a large range of salinity), are found in freshwater systems. There is a population that lives in the St. Johns River. Atlantic stingrays feed on a variety of benthic invertebrates and have special cells in the nose to detect the weak electric fields their prey give off while buried in the sediment. They also like to bury in the sand to ambush prey as they move by.
Breeding occurs in the fall. The smaller males possess two modified fins called claspers connected to their anal fins that are used to transfer sperm to the female. The males have modified teeth they can use to bite the fins of the females. They do this to hold on and make sperm transfer more successful.
The females do not begin to ovulate until spring. So, though they receive the sperm in the fall, fertilization does not occur until the spring. Instead of laying eggs, as some rays and skates do, baby Atlantic stingrays develop within the mother. This is not the same as mammals, who produce a placental to feed the developing young, but more like an internal egg with no hard shell. The embryo is attached to, and feeds from, a yolk sac. Gestation takes about 60 days at which time the yolk sac is depleted, and the young must emerge. Birth usually occurs in late July and early August, and each female will produce 1-4 small pups whose disk are about 10cm (4in.) wide. It was this birthing/pupping period I witnessed.
I returned the following day to search for terrapins and the number of stingrays was significantly fewer. It may be that the birthing process is fast, and the adults leave the coves afterwards. It may have been because that day was the day Hurricane Debby was making landfall east of us and the water levels were abnormally high – something the rays may have noticed and decided to leave – I am not sure.
I was really hoping to see the young rays swimming around – I did not – but plan to search again soon. Stingrays make many people nervous. I witnessed several adult rays whose tails had been cut off – which is very unfortunate – but they are actually cool creatures and fun to watch while paddleboarding. Maybe I will see a baby soon.
References
Dasyatis sabina. 2023. Florida Museum of Natural History. https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/dasyatis-sabina/.
Johnson, M.R., Snelson Jr., F.F. 1996. Reproductive Life History of the Atlantic Stingray, Dasyatis sabina (Pisces, Dasyatidae), in Freshwater St. Johns River, Florida. Bulletin of Marine Science, 59(1): 74-88.
by Rick O'Connor | Jul 26, 2024
People enjoy animals. Zoos and wildlife parks are popular tourist destinations and animal programs are popular on television. It is usually the larger predator animals that get our attention. Sharks, panthers, and bears are popular. People like turtles, raptors, and snakes. Other animals are popular as well like antelope, elephants, and deer.
The green sea turtle.
Photo: Mike Sandler
At public aquariums you see exhibits with whales, sharks, and sea turtles. You also see tanks with reef fish, crabs, and octopus drawing crowds. But one group of animals that has never really drawn attention – either at public parks or wildlife television shows – are worms.
Worms are a world of the creepy and gross. To us, their presence suggests dirtiness or environmental problems. But worms are abundant in our environment and play an important role in ecology. In this series we will meet some of them and learn more about their lives. We begin with the flatworms.
As the name suggests, flatworms have flat bodies. In many species their heads can be identified by the presence of eyespots. Eyespots differ from eyes in that they detect light, but do not provide an actual image. Biologists describe animals as being either positively or negatively phototaxic. Most flatworms are negatively phototaxic, they do not like light. To them, light indicates daytime. A time when the predators can see and attack them. So, when they detect light, they move under rocks, mud, whatever to avoid being detected.
Most flatworms are less than 10mm (0.4 in) in length, though some are 60 cm (24 inches). They possess a mouth on their belly side (ventral) and often it is in the middle of the animal, not at the head end. This mouth leads to a simple stomach, but they lack an anus so solid waste must exit the worm through the mouth – what is called an incomplete digestive system.
This colorful worm is a marine turbellarian.
Photo: University of Alberta
One class of flatworms are the free-swimming turbellarians. Most are carnivorous, feeding on small invertebrates and dead carcasses. Some feed on sessile creatures like oysters and barnacles. And some feed on microscopic plants like diatoms. The carnivorous species wrap their prey with their bodies secreting slime over them. They engulf their prey whole. There are two classes of flatworms that are parasitic: the trematodes (flukes), and the cestodes (tapeworms).
Flatworms lack an internal body cavity (coelom) and thus lack internal organs. Not having lungs and kidneys they must take in need gases, and other materials, and well as expel nitrogenous waste, through their skin. Being flat increases their surface area and the efficiency of doing this. This is why they are flat.
Reproduction in flatworms occurs in different ways. Some will reproduce asexually by simple fission – they split apart producing two worms. Many species reproduce sexually using sperm and egg.
Another class of flatworms are the parasitic trematodes; commonly called flukes. They resemble turbellarians in body shape and design, though the mouth is usually at the head end. Most are only a few centimeters long, but one can reach the length of 7 meters (24 feet)! Their bodies are covered with a skin-like material that protects them from the digestive enzymes of their hosts.
The human liver fluke. One of the trematode flatworms that are parasitic.
Photo: University of Pennsylvania
As with turbellarians, flukes are hermaphroditic but use internal fertilization with other worms to produce young, though self-fertilization can – and does – happen. Their life cycles can include one or several hosts. The primary host, the one the adults reside in, are usually vertebrates, most often fish. The intermediate hosts, the ones the juveniles reside in, are often snails but can be other species.
Life cycle of a trematode. Image: Center for Disease Control.
The life cycle is complex, but a general one would include the fertilized eggs being encased in a shell and released into the environment via the feces of the primary host. A ciliated larval stage hatches from this egg and is either consumed by the intermediate host or penetrates the skin of it. Once inside the second larval stage begins. This eventually becomes a third and fourth larval stage. At the fourth larval stage the young worm possesses a mouth and digestive tract. At this stage it leaves the intermediate host as a free-swimming larva seeking a second intermediate host. Here it goes through more larval stages and eventually becomes encased within a cyst (a hard shell). The encysted larva stage enters the primary host (a vertebrate) after that primary host consumes the second intermediate host. Here it develops into the adult trematode.
A third class of flatworms are the parasitic tapeworms – Class Cestoda. Tapeworms differ from other flatworms in that they have a round head – called a scolex – attached to a flat body, and they lack a digestive tract. The flat part of the body is made up of small square segments called proglottids. They continually add proglottids and can become quite long – some have measured over 40 feet! The scolex has four suckers and a ring of small hooks with which they can attach to the inner lining of the digestive tract with.
The famous tapeworm.
Photo: University of Omaha.
The reproductive organs occur within the proglottids. Cross fertilization between these hermaphroditic worms is the rule but self-fertilization does happen. The fertilized eggs are released when the proglottid ruptures and exit the host via the feces.
Tapeworms do require intermediate hosts. The extruded egg hatches into a ciliated larva which is consumed by the intermediate host before that host is consumed by the primary host – typically a vertebrate.
As we can see the lives of these flatworms are (1) secretive, and (2) not pleasant to think about. But they do play a role in our marine and estuarine ecosystem and are very successful at what they do. They should be appreciated for their success.
In our next article on the World of Worms we will look at the nemerteans.
Reference
Barnes, R.D. (1980). Invertebrate Zoology. Saunders Publishing. Philadelphia PA. pp. 1089.
by Rick O'Connor | Jul 19, 2024
In this series we have found that in the 1970s and 1980s climate scientists developed models that could predict the effects of a warming planet on society.
We saw that society, at that time, had little faith in the accuracy of those model predictions.
We also saw that natural occurring events, like tropical storms and the eruption of Mt. Pinatubo, gave climate scientists an opportunity to test their models – and their models past with flying colors.
We have seen the development of international councils and panels to address climate change, enhance the models, and provide advice on how to turn the potential negative effects of a warming planet around.
We have also seen that many of the predictions from those early models are occurring, some have occurred faster than the models indicated they would.
So…
Is there anything we can do about it?
The answer is pretty simple really. Just like those trying to lose weight – you need to either reduce the calories you take in and/or burn those calories off. With climate you need to reduce the amount of carbon you put into the atmosphere and/or remove the excess carbon.
In 2006 NASA climate scientists stated that we had about a decade to make some serious policy changes to avoid irreversible climate change that could cause economic and ecological havoc. They mentioned we needed to cut CO2 emissions between 50-85% by 2050. Their suggestions could be found on both sides of the solution model.
| Reducing Greenhouse Emissions |
Removing Greenhouse Gases |
| Cut fossil fuel use (especially coal) |
Add technologies to both smokestacks and combustible engines to remove CO2 in their emissions |
| Shift from coal to natural gas |
Sequester CO2 by planting trees |
| Improve energy efficiency |
Sequester CO2 underground |
| Use more renewable energy and make these technologies available in developing countries |
Use better land management practices in agricultural |
| Reduce deforestation |
Sequester CO2 in the deep ocean |
| Use more sustainable agriculture and forestry methods |
|
Other methods that could help reduce CO2 emission…
- Increase the fuel efficiency of our cars. One target had vehicles getting 60 mpg by 2057.
- Reduce the distance we drive each year. One target had no more than 5000 miles/year.
- Cut electricity use in homes and offices by 25%.
- Increase solar power use.
- Increase wind power use.
- Increase the use of biofuels.
- Stop deforestation.
- Better methods in agriculture.
- Install scrubbers in fossil fuel burning engines to clean emissions.
So… How are we doing with these?
Cars are more fuel efficient than they were decades ago. Many have turned to electric cars, or hybrids.
It seems that we are driving MORE miles each year – not less. Our society is designed around the need for an automobile – we cannot function without one. And our city planning seems to have us living farther and farther from our work. When I was younger there was much talk about mass transit to reduce traffic and emissions. In large cities where this was already ongoing it continues. But in the other parts of the county this has not really caught on. We are still driving too much.
There are methods of making homes more efficient. My wife and I adopted some of these as we rebuilt our house after a fire. Compared to neighbors and friends, our power bills are much lower. Many of these methods and technologies are being used in new home developments and are encouraging.
Solar farms are increasing – even along I-10 in the Florida panhandle. There is some concern that these solar farms are replacing food farms, but there is an attempt to do this. Out west we see the same.
The same can be said for wind farms – at least out west.
According to the U.S. Energy Information Administration, biofuel production has increased each year since 1980.
Deforestation has not slowed. As a matter of fact, many developments in the Florida panhandle begin by removing ALL trees. In some cases, they replace lost trees with saplings in the new neighborhoods. But a major source of carbon removal has been removed from the system. There is much more that needs to be done with this issue.
Speaking for the farmers in the Florida panhandle – yes… many have turned to better land management practices to protect their land and reduce, or sequester, carbon.
“Scrubber” in internal combustion engines is required by law in the U.S.
Despite some of these positive changes, carbon in our atmosphere continues to increase – not decrease. Part of this is because this is a global issue and that all of human society must work together to reduce greenhouse emissions. Some countries are doing better than others. There are international summits every few years to discuss what the world should do to tur the tide on climate. But all countries need to attend, particularly those producing the largest amount of greenhouse gases.
Here at home, there is resistance to reducing the use of fossil fuels, so many programs have not moved as far forward as they need to move. It is also important to understand that even with the behavior changes we seek, it will take time to undo the damage already done. We will not see improvement right away. Enacting new programs and technologies now could take over 100 years to see the impacts. It is important to understand that the longer we put changes off, the longer it will be before we see any positive benefits from those actions.
There is the concern that the political and public will is still not there to make these changes happen. But they will need to if we are to see things begin to improve.
Until then – you can do your part. Use fossil fuels as little and efficient has you can. Plant trees to help remove carbon dioxide and shade your house so you need less air conditioning. There are many other things you can do to help turn the tide on climate. Check with your local extension office for more ideas.
