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What is this strange object floating in our lake?

strange object 1

strange object 1

The Question: On two different occasions we have retrieved similar strange objects floating in the lake we stay at in New Hampshire. I know it looks like it could be latex or some other man-made material-but it had a fleshy feel and no openings that could be seen. We did not cut it open. It had a bit of a fishy smell. It was about 13 cm (5 inches) and more like flesh than a plant. What are these?

strange object 2

strange object 2

Submitted by: Alison, New Hampshire, USA

(click on photos and graphics to expand)

The Short Answer: I didn’t recognize these UFOs (unidentified floating objects) right away, but I’m guessing there are some fishermen out there who would. When I started trying to imagine what kind of natural object from a northern lake would float, it suddenly occurred to me that the swim bladder of fish would qualify (also called air bladders or gas bladders).  Swim bladders are air filled sacks in the body that help a fish maintain neutral buoyancy in water.  Most of the large game fish Alison could find in a New Hampshire lake, such as bass or pike, have a swim bladder with a single bulb, but carp have a bladder that is in two parts, just like the ones Alison found.

My guess is that someone in Alison’s lake is catching fairly large carp, cleaning the fish by removing the internal organs, and dumping those organs in the lake. Most of the guts probably sink immediately and are eaten by scavengers. But the swim bladder, if it hadn’t been punctured, would float. And that’s what Alison found.

When I sent Alison a photo of the swim bladder of a carp, she immediately agreed it matched her UFOs.

carp anatomy

carp anatomy

Which came first, lungs or swim bladders? Anatomists long ago figured out that the lungs of some fish, the lungs of land vertebrates and the swim bladders of most fish are all homologous, meaning they develop in the same place in embryos as bulges on the pharynx, the tube that connects the mouth to the rest of the digestive system. That suggests that one of the organs evolved from the other, or they both evolved from the same earlier organ. Since we think of land vertebrates as “higher,” and more evolved organisms than fish, the natural assumption is that lungs evolved from swim bladders. In fact, Charles Darwin himself made that suggestion in On the Origin of Species.

But as evolutionary biologists looked deeper, it appeared that lungs may have come first in early fish that probably lived in shallow, oxygen deprived water. Because air holds far more oxygen than water, gulping air, as some fish do today, would have given these early fish the ability to survive in water with low oxygen. Over the generations, fish that had a pocket in the esophagus that held air did an even better job at gaining oxygen. Natural selection eventually led to fish that had actual lungs as modern lungfish do.  And all land vertebrates, from salamanders to people, are evolved from those early air breathing fish.

But that same apparatus that provided oxygen could also affect buoyancy, and for some fish, that may have proven to be even more useful than lungs because it would have allowed them to venture off the bottom of the ocean or river with minimal effort, opening up enormous expanses of water that had been a struggle to reach for fish that would otherwise sink. And over time, natural selection favored those fish with more and more effective swim bladders.

Further evolution of swim bladders led to the two main types. Fish like carp have a swim bladder that is still attached to the gut so that they are able to regulate the amount of air in the swim bladder by either gulping or burping/farting air. Turns out those cartoon pictures of goldfish blowing bubbles are somewhat accurate.  (Goldfish are in the same family as carp and have the same kind of swim bladder.)

Most fish, however, have swim bladders that are closed off. They fill the bladder by diffusing oxygen and other gasses from the blood into the air bladder, or absorbing them back into the blood. This system is less rapid than gulping, but it allows for the swim bladder to be regulated at any depth, without the need to surface. In fact, there are fish that can “pump” gasses into their swim bladders even against the enormous pressures of the deep ocean.

Sharks and rays, by the way, are part of a relatively small group of fish that don’t have swim bladders.

Swim Bladders and Beer: Commercial beer and wine manufactures often use a produce called isinglass to clarify their products. Because the yeast used to ferment beer and wine tend to float easily in water, particles of yeast can give the product a cloudy appearance. If you wait long enough, the yeast will fall to the bottom of the container, at which point, you can siphon off the clear liquid above. But long ago, brewers realized that certain types of natural collagens, the structural protein that makes up a large part of animal bodies, when mixed with newly made beer and wine, will cause the yeast to clump together and settle out more quickly, clarifying the beer or wine. The collagen you get when you process fish bladders, called isinglass, is especially good at this.

And fish bladders are a fairly cheap commodity, since there are enormous numbers of them that would otherwise be wasted when commercial fishing catches are cleaned. So the next time you drink a glass of beer or wine, remember the connection to Alison’s strange floating objects and wonder about the irony that an object designed by nature to float, does such a good job at making yeast sink.

(By the way, there is another use of the word “isinglass.” It can also mean sheets of the mineral mica.)

Sources: Thanks to Sarah Longo, a PhD candidate who studies fish evolution at the University of California, Davis, for her help.

Longo S., Riccio M., McCune A. R. 2013. Homology of lungs and gas bladders: Insights from arterial vasculature. JOURNAL OF MORPHOLOGY. Volume: 274. Issue: 6. Pages: 687-703.

Cite this article as: Pelletier, TC. (August 22, 2015). What is this strange object floating in our lake? Retrieved from http://askanaturalist.com/strange-object-floating-in-our-lake/ on August 30, 2015.

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How fast do the tiny toads grow?

The Question: I work at a farm in northeast Pennsylvania. I read your article about toadlets. I have been enjoying seeing hundreds of these mini toads as I garden. Mine are still only about an inch long. How long does it take for them to reach full size?

Submitted by: Victoria, Pennsylvania, USA

(click on photos and graphics to expand)

The Short Answer: Victoria, glad to hear you are enjoying the toads. There are so many tiny toads all over my yard right now that I worry about inadvertently stepping on them. In northeastern Pennsylvania where you live, there are two toad species, the American toad (Anaxyrus americanus – formerly Bufo americanus) and the very similar Fowler’s toad (Anaxyrus fowleri – formerly Bufo fowleri). The easiest way to tell the two species apart is to flip them over and look at their bellies. If it has dark speckles, it’s probably an American toad and if not, it’s probably a Fowler’s toad.

toad-growth-chartBoth species start out as tiny toadlets, about 1 cm (3/8 inch) long. They grow rapidly in the first year and then slow down dramatically. By their second birthday, they are pretty close to full grown. Males generally begin to breed in their second year, females in their third. This chart is based on data for the American toad from Frogs of the U.S. and Canada by C. Kenneth Dodd. The book lists the size range of adult American toads as 5-9 cm (2-3.5 in.). The largest American toad on record was a whopping 15.5 cm (6.1 in.). Fowler’s toads are somewhat smaller at 4.5-8.2 cm (1.7-3.2 in.), with a record size of 9.2 cm (3.6 in.).

If your toadlets are already about an inch (2.5 cm), then they must have been early hatchers this year that have done very well eating small insects around your garden. Toads are pretty voracious insect eaters. One study estimated that an adult American toad could eat nearly 10,000 insects a year!

Sources: Dodd, C. (2013). Frogs of the United States and Canada. Baltimore: Johns Hopkins University Press.

Cite this article as: Pelletier, TC. (July 22, 2015). How fast do the tiny toads grow? Retrieved from http://askanaturalist.com/tiny-toad-growth/ on August 30, 2015.
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What to do about this window dove nest?

sam's-doveQuestion #1: This bird made a nest next to my kitchen window. What kind of bird is this?

Submitted by: Samantha, New York City, New York USA

Question #2: A pair of mourning doves have made their nest on the outside windowsill of my home office on the 6th floor of an apartment building. At least one and possibly two fledglings are in the nest and are already trying their wings. I don’t want to harm the birds, but I want to remove the nest as soon as possible because it has infused my office with a barnyard smell. I have read that these birds can raise multiple broods in a season. Is there a time window for me to remove the nest and install a block to prevent their return?

Submitted by: Ron, New York City, New York USA

(click on photos and graphics to expand)

The Short Answer: These two reports of mourning doves (Zenaida macroura) nesting on window sills in New York City came within a week or so of each other. In one case, Sam and her small children were thrilled to have a bird nest so easily visible outside their window. In the other case, Ron was a little less happy, because the birds were nested right below his air conditioner, which was pulling in bird nest smell. Still, he was willing to wait till the dove chicks were free of the nest to remove it.

More Information: Like most species of the family Columbidae, mourning doves lay two eggs. They are remarkably flexible about where they will build their nest, sometimes choosing a low bush, and other times nesting 80 meters (260 feet) up in a tree. They’ll also nest on buildings, window ledges and even on the ground.

mourning-dove-chicksParents share incubation of the eggs, which hatch in 14-15 days. They also share feeding of the chicks with regurgitated “crop milk,” a liquid made from partially digested seeds. As the days go on, parents increasingly mix in seeds. The chicks are ready to leave the nest in about two weeks and after their first flight, and once they fledge they may return to the nest for a day or two, and then begin roosting in trees at night. For another two to four weeks the male parent will feed them until they are independent. Meanwhile, the female may begin laying new eggs.

Pairs can raise as many as six clutches in a single year, so Ron’s concern about his doves renesting under his air conditioner is a valid one. The U.S. Migratory Bird Treaty Act makes it illegal to tamper or move the nest of a native bird while it has eggs or chicks, however. So Ron’s best bet for a humane and legal solution is to watch for the baby birds to leave and then wait a day or two and remove the nest, hopefully before the female begins laying a whole new clutch.

Pigeon and doves: As I mentioned above, the family Columbidae includes doves and pigeons. In fact, there is no difference between the two from a taxonomic standpoint. Some members of the Columbidae are called doves and others are called pigeons, but that’s more about traditional names than anything scientific. In fact, our familiar city “pigeon” is also called both a “rock dove” and a “rock pigeon” (Columba livia).

Sources:

Otis, David L., John H. Schulz, David Miller, R. E. Mirarchi and T. S. Baskett. 2008. Mourning Dove (Zenaida macroura), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/117.

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What are these jelly blobs on my car?

gel blob triciaThe Question: I found these on my car in the driveway. What are they?

Submitted by: Tricia, suburbs of Buffalo, New York, USA

gel blob susanThe Question: There were numerous gel filled discs all over my car after a heavy rain. They were clear with tiny yellow specks towards the middle of the blob. What are they?

Submitted by: Susan, suburbs of Buffalo, New York, USA

(click on photos and graphics to expand)

The Short Answer: Interesting that I received these two questions within a week of each other, both from the Buffalo, New York area. I’m pretty sure the same, or very similar, insects laid these egg masses on Tricia’s and Susan’s cars. I sent the photos to Dr. Gabor Horvath and Dr. Gyorgy Kriska, researchers at the Eötvös University in Budapest, Hungary who have studied why insects sometimes lay their eggs in the wrong place. Based on the photos, Dr. Horvath and Kriska suggested that these are egg masses laid by caddisflies in the family Limnephilidae. Most species in this large family lay their eggs on leaves overhanging water. When the eggs hatch, the caddisfly larvae drop into the water, where they develop in a fairly standard caddisfly way (see this caddisfly article). They glue together a house, which protects them as they feed on detritus. Eventually, they metamorphose into adults, mate, lay eggs on leaves and start the cycle again.

So why did they lay these eggs on cars, instead of on leaves? How does an insect, with a tiny brain, figure out where to lay its eggs in the first place?

It’s not that a caddisfly female thinks about where to lay. Her brain is coded with a recipe or algorithm for where to lay. For example, the instructions might say, fly till you find yourself over water. Then fly up until you come to a horizontal object. Lay your eggs there. I’m oversimplifying it, but the process is probably something like that. And for many insects, especially those whose eggs and larvae need to be associated with water, automobiles cause confusion. That’s what probably happened in both these cases.

More Information:
Dr. Horvath and Dr. Kriska study insect “mistakes” in order to gain insights into how the vision of insects and other animals works. In the case of insects that lay eggs on cars, the answer seems to be related to polarized light. Light that enters our atmosphere is non-polarized, which means that the light waves are oriented in all directions equally. When light bounces off a horizontal surface, such as the surface of a pond or lake, however, the reflected light is mostly oriented in a single direction. We call that polarized light.

In the natural world, the most common sources of horizontally polarized light are the surface of a body of water, or the surface of leaves. Many insects have evolved to detect that polarized light as an indication of a good place to lay eggs. It’s how they know they are flying above water or leaves and not above dirt. It appears, for example, that Limnephilidae caddisflies use polarized light as one of the signals that suggest a good place to lay their eggs on leaves over water.

Unfortunately, for those caddisflies and other insects that rely on polarized light as an indicator of where to lay eggs, reflective man-made horizontal surfaces, like the dark-colored hood or roof of a car, or even asphalt road surfaces can also reflect light in a way that polarizes it. This can lead to insects laying their eggs on top of cars, which is what Dr. Horvath believes happened in this case.

Thanks: Thanks to Charley Eiseman, co-author of Tracks & Sign of Insects & Other Invertebrates for confirmation that these might be insect eggs, and to Dr. Horvath and Dr. Kriska for their help in suggesting what kind of insect might have laid them and why.

Polarized Light: If you are curious about how the polarization of light works, you might find this video helpful: https://www.youtube.com/watch?v=gP751qpm4n4

Cite this article as: Pelletier, TC. (July 17, 2015). What are these jelly blobs on my car? Retrieved from http://askanaturalist.com/jelly-blobs-on-my-car/ on August 30, 2015.

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Move the tadpoles?

The Question: We have a very old hot tub that hasn’t been used for years and the cover has collected a good amount of water from rain and now looks almost like a tiny pond! We recently we have discovered that it is filled with tadpoles! My dad thinks it is a from a tree frog because he has heard them. Should we move them to a nearby water source? Or just leave them alone?

Submitted by: Patrice, Connecticut, USA

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GrayTreeFrog2010

gray tree frog

The Short Answer: Patrice, gray tree frog (Hyla versicolor) is probably a good guess because they are known to lay eggs in everything from ponds to puddles. Trent University in Ontario has a nice chart that compares some of the common North American tadpoles. You’ll see that gray tree frog tadpoles have red or orange on the tail. Tadpoles of some other species in the genus Hyla also have red on the tail, but the gray tree frog is the only frog in that genus found in Connecticut. So if you see red or orange on the tail, it’s a good bet your tadpoles are gray tree frog babies.

Unless you think the water will dry up, I would just leave them. They’ll feed on algae and other stuff growing in the water and they’ll prey on small creatures like mosquito larvae. Moving them is risky. One benefit of breeding in puddles and other temporary bodies of water is a lack of fish, turtles and most predatory aquatic insect larvae that eat tadpoles. You might move them somewhere where there are predators that will eat them. Or you might move them to a place where they won’t find the right kind of food. The best bet might be to trust that the gray tree frog(s) chose your hot tub pond for a reason, and hope for the best.

If you really want to help your tadpoles, the best thing would be to make sure the puddle doesn’t dry up. That would be sure death for them. So add water if the puddle gets low, but make sure you’re not adding chlorinated water straight from your tap. That might kill them. You could fill a couple of buckets with water in advance, and let them sit for several days. Any chlorine will evaporate and algae will begin to grow. If you later add the contents of the bucket to the tadpole puddle, it will give them water and food at the same time.

You could also try supplementing their food supply with scrunched up tropical fish food if you happen to have some. But don’t overdo it. If you overfeed, the uneaten food will release ammonia and nitrites, which might kill the tadpoles.

It takes about six to eight weeks for gray tree frog tadpoles to metamorphose into adults. Let us know how it goes. Good luck!

Cite this article as: Pelletier, TC. (July 14, 2015). Move the tadpoles? Retrieved from http://askanaturalist.com/move-the-tadpoles/ on August 30, 2015.
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