Things from the pond

One of my very favorite things about the place I live is the small pond in the corner of the yard.

Other than a single goldfish, it’s fishless and teems with life. I’ve identified more than twenty species of dragonflies from it and I can almost always find something to photograph while walking around it.

Today was one of those fabulous early spring days. Absolutely clear and the temperature reached the low 70s. So naturally the first thing I did when I arrived home from work was to grab the camera and head to the pond.

The first thing I noticed was that there were Water Striders everywhere.

I have no idea what species they are and no idea how to key them out. I’m fairly certain that it can’t be done from a photograph.

I usually HAVE to know what exactly what a creature is, have to put a name to it, but in this case I think I’m content to just accept that they are water striders and leave it at that.

There was also a water boatman:

and a Central Newt (Notophthalmus viridescens) clinging to a leaf and riding it like a sailboat, tacking into the wind.

Unlike many salamanders, newts are capable of living in ponds that have fish due to the fact that they secrete a poison that makes them unpalatable. They undergo three life stages: a larval form with gills that remains in the aquatic environment in which they were hatched; a bright orangish-red terrestrial juvenile stage called an eft and the adult form that returns to the water. Their life span can reach 15 years and they can grow to five inches or so in length. The eft form travels widely during it’s two to three years, providing dispersal to new areas before returning to the water and transforming to an adult.

That leads us to the next denizen of the pond and the only one that, I’m ashamed to admit, totally creeps me out.

It’s called the Ozarks Highland Leech (Macrobdella diplotertia> and I think most people will agree with my aversion to them. It’s not that I don’t like them – I find them very interesting and actually think the color patterns are attractive – I just don’t want them touching me!

M. diplotertia is sanguivorous (feeds on blood) though a preferred host has not been identified. I have personally observed it attached to a central newt on at least two occasions, but one of my dogs insists on wading belly deep to drink from the pond and he has never came out with a leech attached.

The leech also fuctions as a predator of amphibian eggs. They have been observed feeding on the eggs of the green frog (Rana clamitans) and the southern leopard frog (R. sphenocephala) (Turbeville and Briggler, 2003) as well as those of the wood frog (R. sylvatica) and spotted salamander (Ambystoma maculatum) (Truath and Neal, 2004.) I would be surprised if they didn’t feed on the eggs of other amphibians as well.

There seems to be an interesting relationship between the newt and the leech. The coloring of the leech is very similar to that of the newt, particularly the male newt in breeding color and their swimming motions appear remarkably similar despite the fact that the newt swims with a side-to-side motion and the leech up-and-down. One study (McCallum, Beharry and Trauth, 2008) postulates that the leech is mimicing the newt to take advantage of the previously mentioned toxin secreted by the skin of the newt.

To test the theory, they offered both newts and leeches to ducks (tame and “feral,”) green sunfish and largemouth bass. Neither ducks nor fish would eat either the newt or the leech. But, it turns out, the leeches would very agressively attach both species of fish. The green sunfish would slam their bodies into the side of the aquarium to dislodge the leech, but the leeches actually killed two of the five bass.

This led the authors to the possibility that while fish can’t/won’t eat the newts due to their toxicity, they have also learned that the newts are non-threatening. This might allow the leech, by mimicing the color and swimming motion of the newt, to approach a fish more easily in order to attach and feed upon them.

A Complex Mimetic Relationship Between the Central Newt and Ozark Highlands Leech, ML McCallum, S Beharry, SE Trauth – Southeastern Naturalist, 2008

Macrobdella diplotertia (Annelida: Hirudinea) to Wood Frog and Spotted Salamander Egg Masses, SE Trauth, RG Neal – Journal of the Arkansas Academy of Science, Volume 58, 2004.

The Occurrence of Macrobdella diplotertia (Annelida: Hirudinea) in the Ozarks Highlands of Arkansas and Preliminary Observations on Its Feeding Habits. Turbeville, J.M. and J.T. Briggler – Journal of Freshwater Ecology 18:155-159, 2003

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