Great pond snail (Lymnaea stagnalis) is a very large, air-breathing, freshwater snail. It is commonly sold as an aquarium pet. The body contains both male and female reproductive organs (hermaphroditic). During copulation either the male role or the female role can be performed, though not both. This makes it the ideal subject for recent scientific research into handedness (chirality).
Great pond snail occurs in Europe, Asia, North America, and southern Australia. It occurs throughout the United States and Canada, but it is uncommon south of the 40th parallel. It is common in Minnesota. It is found in permanent, slow or still waters, usually with dense vegetation, including creeks, streams, rivers, marshes, swamps, and reservoirs, and at the edges of lakes and large ponds.
The shell is thin and has 4½ to 6 whorls. The last whorl is the body whorl and is greatly inflated. The remaining whorls are elevated forming a sharply pointed spire. When seen with the tip at the top and the opening facing up, the opening is on the right side. There is no door-like structure covering the opening of the shell. The shell is variable in color, tan to dark brown, and it has no obvious markings. A cavity within the shell has an air bubble that is refreshed every time the snail rises to the water surface to breathe.
Many-headed slime (Physarum polycephalum) is a plasmodial slime mold. It has been reported in Europe, Asia, Australia, Africa, North America, and South America. Most reports are from the eastern United States. All but a few plasmodial slime molds are invisible to the naked eye, are usually overlooked, and are little studied. Many-headed slime is an exception in all respects. It is most often found on a growth medium (agar) in laboratories, where it is frequently used in researching cell development, protoplasmic streaming, and nuclear behavior. In one interesting study it was “shown” that it “solved” a maze. In nature it is found on shaded rotting wood in forests, in woodlands, and even in treed suburbs. It is short lived, appearing after a soaking rain and disintegrating in just a few days.
Many-headed slime lives in rotting wood feeding on fungi and bacteria. In late summer and fall, after a soaking rain, it creeps to the surface of the substrate. It appears as a bright yellow, many-branched network of veins that creep along the surface. Protoplasm can be seen streaming within the veins. When exposed to light it produces spore-bearing structures (sporangia). The sporangia differ from other slime molds in having multiple heads, hence the common name many-headed slime.