This is the coolest! Wildlife photographers put a camera on a remote control car and drove it into a pride of lions. The lions broke the car — no surprise there — but the resulting pictures are very cool. And for some reason watching the lions react to the car cracked me up.Print Friendly
The Short Answer: The dock Angie is referring to is normally floating and therefore the underside is typically in the water. When I sent the photos around to some marine experts, they all agreed that these are tunicates. Complicating the answer a bit, however, is that these are two very different species of tunicates. What look like upside down sand drip sculptures hanging under the dock are Didemnum vexillum, a tiny, colonial tunicate that is an invasive species in Maine and other places on the eastern shores of North America. The other ones, spread out on the top of the dock near Becki’s son’s thumb, are Ciona intestinalis, a much larger tunicate that is native and common in Maine.
What is a Tunicate: When you look at this diagram of an adult tunicate, showing its very simple structure, it might be difficult to see it as a relative. An adult tunicate is essentially a sac with an opening at the top and a second opening on the side. Water is drawn in at the top, filtered for microorganisms, and then expelled through the side opening. Food is moved down into the stomach, processed, and then waste is eliminated into the exiting stream of water. When touched, many tunicates expel water forcefully, which is why they are commonly called “sea squirts.” And they seem much like small sea cucumbers or filter feeding invertebrates like sponges. They certainly don’t seem much like you or any other four limbed animals.
But when you look at the larval tunicate in this diagram, you might not immediately think, “Uncle Fred!” but you might note that it looks tadpole-ish. And since tadpoles are the juvenile stage of amphibians, all of a sudden we’re thinking about vertebrates and not marine invertebrates. And it turns out you’d be on the right track.
As unlike us as the animal in the photo that includes Becki’s son’s thumb seems, it is a member of the Chordata, the phylum that includes all vertebrates and therefore includes you and me. Clearly, it’s a much more distant relationship than between us and a chimpanzee, or even between us and an amphibian. But there are 35 or so phyla in the animal kingdom, spanning everything from rotifers to squid to ants and apes, so to say that the odd creatures in Becki’s photos are in the same phyla as us is no minor thing, either. We share far more similarities with tunicates than we do with insects or an octopus, for example.
There are over 3,000 species of tunicates, all of which are found in marine environments. This small sampling shows a bit of the beauty of these often colorful animals. You can see more of that in the photo collection of the Encyclopedia of Life by clicking here or at the Ascidiacea World Database by clicking here. Tunicates can be colonial, with tiny individual zooids, like the Didemnum vexillum in Becki’s under the dock photo, or larger and solitary like the Ciona intestinalis in the thumb photo. The largest individual tunicates are about 30 cm (12 inches), but colonial tunicates can get much larger. In fact, odd free floating colonial tunicates called pyrosomes can be tens of meters long (20-30 feet), as seen in this video:
What to do about Didemnum vexillum:
The sponge-like colonial tunicate under Becki’s dock, Didemnum vexillum, is not native to the Maine coast. Recent genetic testing points to Japan as the original home of Didemnum vexillum, but it has been spread around the world and is a very worrisome invasive species. In some places, including off the eastern coast of the U.S. and Canada, it is spreading across the sea bottom covering everything – outcompeting all the native animals that would otherwise live on the rocks of the ocean floor. It’s not clear yet what this means for ocean ecosystems, but it doesn’t seem likely that this is good news. As we come to the end of 2013, there is no practical way to halt the spread of Didemnum vexillum or remove it from areas it has colonized. It’s pretty much the worst kind of invasive species situation: an organism that, once introduced, completely overwhelms an otherwise diverse ecosystem and we are pretty much powerless to stop it.
Thanks to Kevin J. Eckelbarger, Professor of Marine Biology at the University of Maine School of Marine Sciences, and to Sara M. Lindsay, Associate Professor of Marine Sciences & Marine Biology at the University of Maine, for their help in identification of the tunicates in Becki’s photos. Thanks also to Gretchen Lambert of Ascidian News for her help in reviewing this article for accuracy.
Encyclopedia of Life – http://eol.org/pages/1486/overview x
Ascidian News: http://depts.washington.edu/ascidian/
Ascidiacea World Database – http://www.marinespecies.org/ascidiacea/index.php
Stefaniak, L., Zhang, H., Gittenberger, A., Smith, K., Holsinger, K., Lin, S. and Whitlatch, R. B. 2012. Determining the native region of the putatively invasive ascidian Didemnum vexillum Kott, 2002. J. Exp. Mar. Biol. Ecol. 422–423: 64–71.Print Friendly
Submitted by: Erin, USA
The Short Answer: There are really two questions here. Let’s deal with the easy one first. There are two ideas of what qualifies as a fruit. The culinary definition says any generally sweet plant parts are fruits. This includes all the things we typically think of as fruit, such as apples, pears, and berries of many kinds. It also usually includes things like rhubarb. And it definitely includes bananas.
To a botanist a fruit is “… any ovary and its accessory parts that has developed and matured. It also usually contains seeds.” (From Introduction to Plant Biology, by Kingsley R. Stern) The ovary of a plant is part of the flower pistil. Most pistils are shaped like a vase, with a rounded bulb and a thin neck. The ovary would be the bulb. Once the pistil is fertilized with pollen, the seeds develop in the ovary and the ovary often becomes large and fleshy, like an apple or a peach. The botanist’s definition of fruit includes most of the things we usually think of as fruit, such as apples, peaches and berries. It would not include rhubarb, which is a plant stem and does not come from the ovary. It would also include some things people don’t typically think of as fruit, such as tomatoes, green beans, and avocados.
The botanist’s definition would most definitely include bananas, which are the developed ovaries of the banana plant. So by any definition I’m aware of, a banana is a fruit.
Is a banana tree an herb? Here’s where I think your doctor’s confusion comes from. The culinary definition of an herb is basically any plant part that has a distinctive odor or taste useful in cooking. I’m not sure a banana qualifies for that definition. Botanists however, split plants into two major groups, herbs and trees. Trees have a woody interior that persists year after year and supports the plant. Wood is the interior structure of mostly dead cells that strengthens the tree, allowing it to grow tall and survive multiple years. Trees can be as huge as redwoods or as small as the dwarf willow (Salix herbacea), which only grows to be about six cm tall (2 in.). Many botanists would limit the use of “tree” to plants that grow much larger (as hinted at by the dwarf willow’s Latin name “herbacea” which suggests that it’s like an herb).
Herbs include almost everything that isn’t considered to be a tree. It’s important to note that this is a descriptive term, not a taxonomic or evolutionary category. A spruce tree and a willow tree are clearly both woody trees, but they are not at all closely related. The willow is an angiosperm, a flowering plant, whereas the spruce is a gymnosperm. Most herbs are angiosperms, much more like the willow tree than they are like a spruce.
Banana trees grow from an underground root system called a corm, which can last for many years. Each corm sends up one or more shoots, which develop large leaves. The thick stalks of these leaves wrap around each other and thicken into the trunk of the banana “tree.” A central stem comes up through the leaf stalks and develops the banana “heart,” which is a structure that includes multiple small flowers, each of which has an ovary that develops into a banana. Once the bananas have ripened, the entire plant dies back to the ground, and the corm sends up a new shoot. Even though a banana plant can get to be over 7.5 meters tall (25 feet), it only lasts about a year or so. And the interior of it is not a structure of dead cells as with wood. So a banana “tree” is not technically a woody tree.
Therefore, to a botanist, banana is an herb. Your doctor is right about that. But from a botanist’s standpoint, whether something is an herb or not is about the plant, not the fruit. Many, if not most, herbs have fruit, including the banana tree.
If a banana is a fruit, where are the seeds? Ah, interesting question. Bananas and plantains come from plants in the genus Musa, which is native to Southeast Asia. The commercially grown banana is a hybrid of at least two species, Musa acuminata and Musa balbisiana. As with many hybrids, when M. acuminate and M. balbisiana combine, the pairing of chromosomes often goes awry, with the resulting hybrid offspring ending up with three sets of chromosomes, instead of the usual two. As is also often the case, the “triploid” hybrid is almost entirely sterile. Seeds rarely form. Which is nice for those of us who love the banana fruit. The picture here shows what a wild banana looks like and as you can see, it is full of fairly large seeds, which would spoil the fun of a banana split, I’m afraid.
So even if you don’t care whether a banana tree is a true tree or really just a large herb, you should be glad it is a sweetly defective fruit.
Hippolyte, I, Jenny, C, Gardes, L, et al. (2012). Foundation characteristics of edible musa triploids revealed from allelic distribution of ssr markers. Annals of botany, 109(5), 937-51.
Stern KR, Jansky S, Bidlack, J. (2003). Introductory Plant Biology. McGraw-Hill Higher Education. New York.Print Friendly
The Question: We have a larch tree in our garden, quite close to the house, so we get to look at it through our windows. We’ve found something on it that we find odd. There are pure white very small round things dotted all over the tree on the pine needles. My son took two off, and he said they felt like cotton wool and slightly sticky, and inside one was like a tiny greenish wing? Made us think then of a green fly? The other one had little black bits in it. This is our third summer living here and this is the first time we have seen this.
The tree looks very healthy apart from the white things. It’s had plenty of rain this year, and it’s still getting new growth on it. The tree is about 60 years old, from what I can gather. We live in a village, and larch trees in gardens around here are rare. Do you have any idea what these white things are? And, if they are some kind of bug, will they be rid of when the tree dies in the winter? We’re worried about other trees as well as wheat and barley fields nearby.
We also took a picture of this creature, which seems to be associated with the white spots.
Submitted by: Angie, England
The Short Answer: The white dots are the egg cases of adelgids, probably the larch adelgid, (Adelges laricis). Adelgids are insects related to aphids. The egg cases are made of a kind of wax secreted by the insects for protection. They have a “wooly” appearance, which leads to them often being called “wooly adelgids.” There are approximately 50 species, all native to the northern hemisphere. Adelgids are specialized to feed on conifer trees, and in some cases, more on this below, they can kill the trees. The good news is that the half centimeter or so (3/8 inch) insect pictured in your palm was identified by Abby Parker from BugGuide.com as the larvae of a lady bug, which is almost certainly there because it is feeding on the adelgids – and protecting your tree.
Is Angie’s Tree Doomed? In our email exchange, Angie offered that she did a little research on her own and read about the wooly adelgids that are decimating eastern hemlocks (Tsuga canadensis) in the United States. This made her justifiably nervous about her tree. Entomologist Christine Tilbury of
British Forestry Commission told me “Two adelgid species are known to occur on larch in the UK, Adelges laricis and Adelges viridis. A. laricis is common and widespread and the more damaging of the two. A. viridis, which is also widespread but occurs less frequently, causes no serious damage. A. laricis can be a serious pest of European larch (Larix decidua), when small colonies build up over several years into vast numbers. The foliage takes on a bluish-white appearance with the woolly secretion and needles are bent or distorted. Copious honeydew produced by the Adelgids becomes blackened with sooty moulds. Later needles turn purplish brown and drop and shoots die back. On young trees sustained attack can lead to shoot dieback and bud failure which sometimes weakens and kills the whole tree, a condition known as Larch dieback. There is no recommended treatment for large trees. On small trees of high value the overwintering A.laricis nymphs, which do not secrete any protective wax, may be sprayed with a permitted contact insecticide, applied on a suitably mild and calm day between November and February. No biological controls are currently available.”
So in answering the question about the risk to your tree, it seems that the answer hinges on whether the maker of your white dots is Adelges laricis or Adelges viridis.
How can you tell?
The adelgids are very small, on about 1 mm (less than a 16th of an inch). When they hatch out of their wooly nurseries, they are called “crawlers.” If you could find a few crawlers on your tree, an entomologist could put them under a microscope and tell you which species you have (see these slides, thanks to Nathan Havill of the USDA for the pictures). Short of that, however, Christine Tilbury says there are a couple clues. “A. laricis is the most common adelgid on larch in Britain. Heavy infestations with much bluish-white waxy-wool will be due to A. laricis. Lighter infestations where there is less wool are best distinguished by examination of the needles. A. viridis causes a characteristic ‘elbow-like’ double kink distortion. There is localised needle yellowing around the site of feeding but affected needles are not killed. A. laricis also causes needle distortion but the needles are curled and twisted rather than kinked, needles turn brown and fall and there is shoot dieback. Shoots colonised by A. laricis may also feel sticky to the touch due to the production of honeydew.”
By the way, the hemlock wooly adelgid (Adelges tsugae) that is such a problem in the United States has not been found in England yet. Most likely it will get there eventually. If we’re lucky, hemlocks in the UK may be immune. Most hemlocks in the UK are western hemlock (Tsuga heterophylla), which are native to the west coast of North America. In North America, they seem to be immune to the adelgid that is decimating eastern hemlock.
The Strange Life of Adelgids: Adelgids have one of the most complicated life cycles you will find in the animal kingdom. All of the adelgid species have as their primary host one of the 35 or so species of spruce trees (genus Picea) and a secondary host that is another conifer, such as larch, hemlock, pine or fir. You’ll need a scorecard, but let me see if I can run through this quickly. It’s a cycle, so there’s no real beginning, but let’s start with the tiny winged adults that fly from the secondary host to the primary spruce tree host. Once they land on a spruce tree, the adelgids lay eggs and die, sheltering the eggs with their wings. The eggs hatch into males and females that lack wings, which go through four developmental “instars” before becoming adults that mate. The mated females lay a single large egg, which hatches into a wingless female. The female feeds and then induces the spruce tree to create a “gall,” which resembles a small cone. The gall is destined to become an adelgid nursery. In the spring, the female, after going through several instars, lays a clutch of eggs that hatch and move into and are enveloped by the growing gall. These larvae feed on the gall and go through several more instars. By mid-summer, the gall dries out and opens. The adelgids emerge and molt into winged adults, which migrate to the secondary host, a non-spruce conifer.
Got all that? Good. But stay tuned. There’s more.
Once the flying adelgids have settled on the secondary host, they lay eggs and die. The eggs hatch into females and grow, through several all female generations. It is these adelgids that feed with sometimes destructive result on larches and hemlocks. These are also the generations that lay eggs covered by waxy “wool.” Some of the eggs that hatch develop into the winged adults that fly back to the original spruce host to start the cycle all over again. Others develop into wingless females that stay on the secondary host (larch or hemlock). In the spring, these females grow and lay eggs and continue the generations on the secondary host. In this way, the infestation on the secondary host can grow and eventually kill the tree without ever needing the primary spruce host.
Phew! And we thought human life was complicated.
It’s not really important to remember all that, of course. It’s just a fascinating way for a tiny creature to live. By the way, because the hemlock wooly adelgid’s spruce tree host is not found in the United States, it simply reproduces through all female generations on its secondary host, the eastern hemlock. When winged adults form, they fly away, but unless they make it to Japan, they die without ever completing the cycle. Even without that part of the cycle, the hemlock wooly adelgid has destroyed large swaths of Eastern hemlock.
Sources: Havill, N P, & Foottit, R G. (2007). Biology and Evolution of Adelgidae. Annual Review of Entomology, 52:325-49.Print Friendly
The Question: I found this little guy in my backyard. It’s smooth and green on top and gray/tan on the bottom. It has striped legs and horizontal pupils. What is it?
Submitted by: Elizabeth, southern Indiana, USA
The Question: It’s 9:00 p.m. and I live next to a small woods. I hear a noise outside and was wondering if it was a bug or bird. I hear this noise regularly. It’s a repetitive trill same note. Here’s my recording:
Submitted by: Diane, Ohio, USA
The Short Answer: I’m combining Elizabeth’s question and Diane’s question because they are both dealing with the same species … maybe. Elizabeth’s picture is of either a gray tree frog (Hyla versicolor) or a Cope’s tree frog (Hyla chrysoscelis). They are pretty much impossible to tell apart by appearance, especially since both are so highly variable. In fact, despite the “gray” in its name, the gray tree frog can be any color from green to brown or gray, as this collage shows. And the Cope’s has the same variation. To make it even more difficult, any one individual frog can change color to some extent depending on its surroundings. What both species have in common is yellow markings on the underside of their hide legs, so look for that.
The way experts tell the two species apart is by their call. Carl Gerhardt, at the University of Missouri, who studies communication in frogs, says that above 75 degrees, the difference between the two species is that you can hear distinct pulses in the call of a gray tree frog, whereas the Cope’s sounds more like a buzz. (As the temperature drops, however, the trill of the Cope’s slows down and begins to sound more like the gray.) Listen to these two videos and you should be able to tell the difference:
Cope’s tree frog: http://www.biosci.missouri.edu/gerhardt/video/Hyla%20chrysoscelis.mov
Now listen to Diane’s recording again and try to guess which frog Diane’s is. Click here to see if your answer agrees with Dr. Gerhardt.
Another way to tell which frog you have is by location. As the range maps at these links show, if you’re looking at one of these frogs in the most southeastern states of the United States (Florida, Georgia, Mississippi, Alabama, South Carolina), you probably have a Cope’s tree frog. If you are in the northeast, from New York to New England, you almost certainly have a gray tree frog. In all the other states, it’s possible to find both. Where Diane lives in Stark County, Ohio, only the gray tree frog has been recorded, so that’s confirmation that Dr. Gerhardt’s identification from the frog’s song is correct.
Gray tree frog range map: http://www.amphibiaweb.org/cgi-bin/amphib_query?special=maps&genus=Hyla&species=versicolor
Cope’s tree frog range map: http://www.amphibiaweb.org/cgi-bin/amphib_query?special=maps&genus=Hyla&species=chrysoscelis
Elizabeth, by the way, said she took her picture in southern Indiana, which means she probably has a Cope’s tree frog.
The Weird Genetics: It’s clear that the Cope’s tree frog and the gray tree frog are very closely related. Just how closely was discovered in the 1970s when scientists realized that the gray tree frog is basically a Cope’s tree frog with a doubled set of chromosomes.
If you remember your high school biology, in most organisms every cell has two copies of each chromosome. When cells in the reproductive organs undergo meiosis to create eggs and sperm, the chromosomes are duplicated, resulting in four copies of each chromosome. Then the reproductive cells divide twice, each time halving the number of chromosomes. The end result is egg and sperm cells with one of each chromosome. When you put and egg and sperm together you get back to having pairs of chromosomes, one from the egg and one from the sperm, just in time to make an embryo.
Sometimes, this process goes awry and an egg or sperm cell will end up with two sets of chromosomes or even three or four, instead of one. When it joins with its partner, the resulting embryo will have more than the usual number of chromosomes. Usually when this happens, the embryo doesn’t develop, or it dies after developing.
But sometimes the embryo develops normally and results in an organism with more than the usual number of chromosomes. For some reason, this is relatively common in amphibians. And the gray tree frog is an example. It is essentially a Cope’s tree frog with a doubled set of chromosomes. Having twice the number of chromosomes means that the Cope’s tree frog and gray tree frog are generally unable to interbreed, which is why they remain separate species.
But the fact that a gray tree frog genome is essentially the same as a Cope’s tree frog genome, only doubled, explains why they are so similar and so hard to tell apart. In fact, careful analysis of the DNA of these frogs shows that some gray tree frogs are more closely related to certain populations of Cope’s tree frogs than they are to each other, suggesting that while the gray tree frogs all have the same doubled set of chromosomes and look and act the same, they may actually represent three separate events where the chromosomes of Cope’s tree frogs were doubled. And because the doubled chromosomes of the three separate gray tree frog populations match, they are able to interbreed readily.
What’s interesting is that the three populations of gray tree frogs sound very much the same when they sing – and sound similarly different from Cope’s tree frogs. This suggests that the doubled chromosomes themselves lead to the different song. In fact, Dr. Gerhardt and one of his students have been able to artificially create frogs with three sets of chromosomes (midway between the two of a Cope’s and the four of a gray tree frog). These frogs sing a song whose trill rate is between the Cope’s and the gray.
How this happens is not well understood. But having extra genetic material does have effects. For one thing, it makes the cells of the gray tree frog larger than those of the Cope’s tree frog. It seems likely that the larger cells cause the slower trill rate in the artificially created frogs and in the gray tree frog.
Which is good for us, because otherwise, the only way to tell the two species apart would be to put their cells under a microscope and count chromosomes.
Thanks to Dr. Gerhardt for the identification of Diane’s recording.
Keller, M J & Gerhardt, H C. (2001). Polyploidy alters advertisement call structure in gray tree frogs. Proceedings – Royal Society. Biological sciences, 268(1465), 341-5.
Amphibiaweb summary of scientific research on Hyla chrysoscelis and Hyla versicolor: http://amphibiaweb.org/cgi/amphib_query?where-genus=Hyla&where-species=chrysoscelis.
Gray tree frog (Hyla versicolor). Click to return.Print Friendly