Saturday, June 13, 2015

Ramble Report June 11 2015

Ruby throated humming bird on nest

Today 21 Ramblers assembled at 8AM at the Arbor. Those who read the Athens Banner Herald this morning saw that a female hummingbird has built a nest in the Garden. I wanted to set up a spotting scope to see the bird and I knew it was going to take some time to do that. It is not easy to find a camouflaged nest the size of a golf ball on a slender, leafy branch 20 feet up in an oak tree. Uncertain about how long it would take I suggested that we skip our customary reading and hustle over to the lower part of the garden where the tree and nest are located. Everyone was careful not to disturb the nesting bird and waited patiently while I fumbled around with the scope. I finally found the nest and everyone got a chance to see it, some while the female was perched inside.

Today's route: The recent rainy weather has encouraged the growth of mushrooms so we went down the purple trail to seek what we could find.

International garden:
As we crossed the International Garden bridge we heard loud noises coming and stopped to listen. Most of what we heard sounded like banjo strings being plucked by a six year old child. There were a few snores thrown in, but the majority of the sounds were "glunks." This is the call of the male Green frog, which looks like a smaller version of a Bull frog. The snores sounded like the call of the Southern Leopard frog, but may have simply been excited Green frogs. This website has a recording of Green frogs calling.

Hugh enjoying the Bottlebrush Buckeye
Just beyond the end of the bridge the Bottlebrush buckeye that we've been watching for many weeks has finally exploded into bloom. It is covered with numerous inflorescences each composed of hundreds of white flowers. We should
Bottlebrush buckeye flowers
have started a pool to bet on when it would bloom. The curious thing about this plant is that even though it is covered with thousands of flowers only a few will produce the very large buckeye seeds that are typical of the plants in this genus (Aesculus). The ratio of seed to flower size is enormous. Look for those few fruits in the fall.

Near the edge of the buckeye Tom spotted a large, gangly fly bobbing up and down. I initially thought this was a "dance" fly, but now I am confident that it is not even a true fly. It is a type of mecopteran, a hangingfly. While my attention was drawn to the male with its hypnotic, bouncing flight I overlooked the object of its intention – a female hanging from the vegetation in
front of it. It wasn't until I saw Don's photo of the female that I realized my
Hangingfly closeup
mistake. Courtship in some of the hanging flies is similar to what I mentioned at the ramble – the male presents the female with a nuptial gift of a dead insect. If she accepts it, then he mates with her as she consumes the gift. I didn't see any "present" being held by the courting male, so this might be a species that forgoes this gentlemanly gesture. (And what is the difference between a true fly and a hangingfly? True flies have only one pair of wings while hangingflies have two pairs.)

Black Cohosh inforescence
A little further along the sidewalk was a nice group of Black cohosh in vigorous bloom. The flowers lack petals; the white fuzziness is produced by the multiple stamens in each of the tiny flowers that make up the inflorescence. As pointed out on previous rambles this plant has a history of medicinal usage in the treatment of menopausal and other female-related conditions. If you'd like to read more information about this topic here is a very thorough review.

Purple Trail: We looked specifically for mushrooms and found many popping up through the leaf litter or on decaying wood. And we happened upon other interesting organisms as well. The problem with mushrooms is that none of us can reliably identify most of them to species level, so we have to be satisfied with our semi-educated guesses. Or just enjoy seeing the diversity exhibited by this unfamiliar part of the living world.

Tom spotted a strange growth on one of the uppermost leaves of a Highbush blueberry. Examination with a hand lens revealed to be the remains of a fungus infected insect. I can't
Fungus-infected arthropod
identify this fungus but it looks similar to pictures I have seen of fungi in the genus Cordyceps. These fungi infect insects and have the unusual ability to change the behavior of their host. As the fungus grows within the body of the insect it causes it to climb to a higher, exposed location that would be more favorable for the dispersal of fungal spores. When the zombie bug reaches such a place it stops and eventually dies as the fungus consumes its internal organ and then produces spore-bearing projections from various places in the insect body. The spores are carried away by the gentlest of breezes and if they happen to land on an unlucky insect or spider the cycle of infection continues. This bug was so overwhelmed by the fungus that I couldn't determine what kind it was. It could have been a cricket or even a spider.

American toad, typical coloration
As we walked along the trail we kept noticing tiny, newly metamorphosed toads hopping about the leaf litter. These probably came from the closest body of water, the beaver marsh. Toads lay literally thousands of eggs and, of the
American toad, reddish variety
ones that hatch a fairly large percentage may survive through metamorphosis, if the pond they are in does not contain too many predators. (The nymphal stages of dragonflies relish a good tadpole dinner.) The newly emerged toads now eat insects instead of algae and they have to forage far and wide for their food. They can do this only when the weather is suitable – rainy so that the leaf litter stays damp. When the litter dries out they have to crawl down deeper and can't move about so freely. Of the thousands of toadlets that emerge from the ponds only a small percentage will survive to reproduce the following year. The terrestrial environment is dangerous and inhospitable, but a few do manage to survive.

When we saw these tiny toads hopping in the leaf litter many ramblers said "Look, a frog!" and I corrected them by saying, "No, that's a toad." Which prompted Bob to ask me "What, exactly, is a toad?" Before I answer Bob's question let me introduce a useful term: anuran. Anuran means "without a tail" and is a collective name for both toads and frogs. Anurans are amphibians that lack tails as adults. Salamanders are amphibians that have tails as adults. A toad is an anuran with dry, warty skin that is found away from water, as in your back yard. When they are chased or surprised they hop away. Hopping consists of little short jumps. On the other hand, a frog is usually found near permanent water, like a pond or lake, and has smooth, moist skin. They leap, not hop, into the water when you surprise them. Examples of frogs that you might be familiar with are Leopard frogs and Bullfrogs. Where these distinctions fail is that almost all of our anurans return to water to reproduce. So at some time in their life toads as well as frogs will be found in ponds or temporary pools, mating and laying eggs. There are also anurans that don't fit well into either category. For example, our common Gray tree frog has slightly warty skin that is moist and is often found away from water, clinging to a window or sliding glass door. So should it be considered a frog or a toad? Or is it a case of trying to shoehorn nature into inappropriate categories? There is nothing wrong with using the names toad or frog – just recognize that they are not precise and there are going to be a lot of gray areas. They are like the terms "car" or "truck." How well do station wagons, hatch backs, SUVs and dragsters fit into those two categories? Formal classification divides the anurans in our region into five different families with semi-official common names: Bufonidae (true toads), Ranidae (true frogs), Hylidae (tree frogs), Scaphiopodidae (spadefoot toads) and Microhylidae (narrowmouthed toads). The last two of these are not commonly seen by non-herpetologists. I hope this explanation is not overkill.

Single Sourwood flower
At several spots on the trail we noticed tiny white specks. Closer examination revealed that they are the flowers of the Sourwood tree. The inflorescences are high in the air and we couldn't see them, but, if we could, they would resemble those of Lilly of the valley.

With our focus on fungi today it might be a good idea to remind everyone about what makes fungi different from other life forms. You have probably seen molds, a type of fungus that grows on stale bread or an old piece of cheese. If you look carefully past the colorful spores you will notice white fuzz radiating out in a circle from a little mound. That fuzz is a mass of very fine threads. An individual thread is called a hypha (plural: hyphae). A fungus consists of a mass of hyphae. The fuzzy part is called the mycelium and in nature it is normally unseen as it grows underground or in rotting wood. It may be unseen but it makes up the bulk of the fungus. The mycelium is the feeding organ of the fungus. It performs the same functions as the roots of a plant – it gathers water and mineral nutrients from the soil or whatever it is growing in. And, in addition, the mycelium secretes digestive juices that break down the food stuffs in which it is growing. If it were an animal we would say that the mycelium digests its food. But it's a fungus, so we say that it rots its food. But the two processes are the same – complex carbohydrates, fats and proteins are broken down into smaller, simpler molecules. Those products of digestion (or rot) are then absorbed by the mycelium and used to produce more hyphae. (We do the same thing in our digestive tract, but it is, of course, inside our body, not on the outer surface as it is in the fungi. If humans were like fungi we could eat a hamburger just by holding it in our hand and squeezing our fingers into the bun and the patty.) This pattern of external digestion and absorption of nutrients is characteristic of fungi. They, along with bacteria, are responsible for all of the recycling of materials in the natural world. Collectively they are the decomposers that return organic material back to the soil. 

Occasionally the mycelium produces a conspicuous mushroom. What is the mushroom for if the mycelium is the part that does all the decomposition? In a word – reproduction. The mushroom is the fungal equivalent of a flower. Because we don't see the mycelium when the mushroom is absent we incorrectly assume that the mushroom is the whole organism. It's like saying an Azalea is not there unless it has flowers. The function of a flower is to produce seeds and it does this via a sexual process – you know, the talk about the birds and the bees. But in the fungi the sex starts long before the mushroom appears. It begins when the mycelia of different, sexually compatible fungi meet and fuse. This sounds like the way in which each of us got started with an egg and sperm getting together to produce a fertilized egg. But fungi don't have males and females. They can have multiple "sexes" that are better thought of as mating types. When mycelia of the same mating type grow through the soil they pretty much ignore one another, but when they meet a mycelium of a different mating type they fuse together and their nuclei intermingle. But fertilization as we know it doesn't occur just yet. Instead the mushroom has to be built. The mycelium now contains genetically distinct nuclei and its hyphae grow and differentiate into the body of a mushroom. The hyphal cells that are found in the gills or pores of the mushroom is where the fusion of the different nuclei takes place. And this fertilized nucleus then divides in the same way that our cells that produce gametes (egg and sperm) divide. You probably were exposed to the cell division called meiosis. That is the type of division that produces cells with one half the number of chromosomes of the parent cell. The products of the fungal cell division become spores, not gametes. The spores are produced by the trillions and are carried away on the breeze to start a new generation of fungal mycelia.

Some of the mushrooms we saw today participate in a symbiotic (mutualistic) relationship with trees. Their mycelia form an intimate connection with tree roots and obtain carbohydrates (sugar) from the tree. In return they supply the tree with water and mineral nutrients, especially phosphorus and nitrogen, that are essential for tree growth. These mushrooms are called mycorrhizal, meaning "fungus-root." Without the mycorrhizal fungus the trees do not grow as well. In addition, one mycorrhizal fungus can form associations with more than one tree. It has been shown that carbohydrates can be passed from tree to tree via these mycorrhizal connections. The implications of this tree-tree interaction are only beginning to be explored and understood.

Here is a gallery of some of the mushrooms we observed:

Pinwheel Mushrooms

Sulfur Bolete

False Turkeytail

Old Man of the Woods

What are slime molds and how are they different from fungi?

Slime molds were originally thought to be a kind of fungus. They produce spores from specialized structures, just like fungi do, but their life history is very different. When a slime mold spore germinates it does not produce a hyphal thread – it releases an amoeba like single celled organism. This amoeba wanders through the soil or rotting wood eating bacteria and yeasts that it encounters and it eats them in an animal-like way. The food is not externally digested, as it would be by a fungus. Instead the amoeboid cell engulfs it and brings it inside the cell where digestion takes place. The amoebae grow and divide and wander about until they run out of food. Then they emit a chemical signal that attracts other amoebae. In one type of slime mold, called a plasmodial slime mold, the mass of amoebae fuse with one another to form a giant, amoeboid cell with thousands of nuclei. This giant amoeba creeps and crawls up to the surface where it is exposed to the air. There it produces spores which are carried away on the breeze to start the life cycle over again. 

In another kind of slime mold, called a cellular slime mold, the amoebae aggregate but do not fuse together. Instead they become a multicellular organism that creeps to the surface where some of the cells stream upward to form a stalk capped with a mass of spores. The cells that form the stalk do not get a chance to reproduce, that is, form spores; only the ones on the top of the stalk form the reproductive spores. This is just like the division of labor we see in more complex multicellular plants and animals.

Click here to see a time lapse video of a plasmodial slime mold, the kind that produce a giant, multinucleate amoeboid organism.

Here are a couple of slime molds we saw today:

White coral (L); Wasp nest slime mold (R)

White Coral slime mold

Finally, it was growing hotter, so we decided to return. Some of us enjoying further conversation and beverages at Donderos'.

Common Name
Scientific Name
Ruby throated hummingbird
Archilochus colubris
Green frog
Rana (Lithobates) clamitans
Bottlebrush buckeye
Aesculus parviflora
Hanging fly
Order Mecoptera
Family Bittacidae
Black cohosh
Actaea racemosa
Golden St. John's Wort
Hypericum frondosum
Unidentified marasmius mushroom
Marasmiellus sp.
High bush blueberry
Vaccinium elliottii
Fungus on unidentified insect
Cordyceps sp.?
False turkey tail mushrooms
Stereum ostrea
Sulfur bolete
Boletus campestris
Unidentified bedstraw
Galium sp.
Chanterelle mushroom
Cantharellus cibarius
White coral slime mold
Ceratiomyxa fruticulosa
Fly agaric
Amanita muscaria
Black footed marasmius
Marasmiellus nigripes
Wasp nest slime mold
Metatrichia vesparium
American toad, brown and red
Bufo (Anaxyrus) americanus
Sourwood [flowers]
Oxydendrum arboretum
Pinwheel mushrooms
Marasmius rotula
Oak apple gall/oak apple gall wasp
Amphibolips confluenta
Tapioca slime mold (tentative)
Brefeldia maxima
Black winged damsel fly
Calopteryx maculata
Old Man of the Woods
Strobilomyces floccopus
Common split gill mushroom
Schizophyllum commune
Eastern gray squirrel
Sciurus carolinensis

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