Monday, December 10, 2007

Snail Luvin' update

Succinea cf. ovalis crawling up the side of the tank. The shell is about 1cm long, not quite maximum size for this species. The yellow splotches were from a pigment marker I tried to use to tell individuals apart, but it rubs off too easily.

Last month (11/30), I mentioned that two of my Succineid snails (one very large individual and an intermediate-sized one (as above) were mating. I didn't get any photos of the dirty deed, but here's an update:

•I found a clutch of about 50 eggs in the tank on Dec. 3rd. They were just below the leaf litter in a little pile.

•The larger snail of the mating pair died about 5 days later. The tank they were in was a little dry, but none of the other snails perished. It's now sitting in alcohol, awaiting dissection to confirm it's species (succineids are notoriously difficult to ID to genus, let alone species without soft tissue [i.e. genitalia], so I was hoping to get the chance to get a peek at the snails naughty bits...).

So this brings me to the point of my post, aside from some neat succineid biology: many species of snails are semelparous. That is to say, they only reproduce one in their lifetime. Other snails are iteroparous (multiple reproductive cycles). Most succineids have been reported to be semelparous, and it appears this is the case for this particular species from Duluth. One interesting note, however, is that one individual who took part in mating is (as yet) alive.

I'm guessing that the large egg clutch was produced by the larger snail, and the sperm was provided by the smaller snail. This could have a distinct advantage in snail survival. By providing sperm at least once (more than once, perhaps?), the snail can reproduce at least twice - once as a sperm donor, once as the egg donor. Thus increasing the total number of individuals with the parent's genetic material. I have more to say about itero- versus semelparity, but that will have to wait until after I get some of my PhD data published. Next up: amino acids from fossil succineids!


  1. I didn't know they were semelparous.

    Did you notice if the smaller one was on top when they were mating?

  2. Pilsbry 1948, and others noted that most succineids seem to live for about one season.

    I'm not sure, they were both sort of sideways against the side of the tank. It looked like the bigger one was eating the smaller one at first.