365 Urban Species. #151: Pond snail

[urbpan]

Photos by urbpan. Location: Ward's Pond, Olmsted Park, Boston.

Urban species #151: Pond snail [edited] Probably genus Physella

The ancestors of pond snails evolved lungs to survive out of the ocean, only to return to the water, and come up for air once an hour or so. They are found in fresh or brackish water, and are tolerant of pollution. In fact, they feed on algae, and some pollutants (sewage and fertilizer) promote algae growth, increasing the numbers of this snail. The many similar pond snails in the [edited] family Physidae grow quickly, and have shells that are so thin that they are (once cleaned of mud) nearly transparent. Under the evolutionary pressure of shell-crushing predators, such as pumpkinseeds and carp, populations of pond snails develop more rounded shells, which resist crushing.

Like most snails, pond snails are hermaphrodites. [edited] After mating, wherein one snail takes the female role and the other the male role, they attach their gelatinous egg masses to vegetation or debris in the water. Unless eaten, pond snails usually live about one year.


Egg mass at bottom.

Comments

[fledchen.livejournal.com]

Ampullariidae (apple snails) are not hermaphroditic

http://www.applesnail.net/
http://en.wikipedia.org/wiki/Apple_snail

[urbpan.livejournal.com]

Thanks for that.
I may end up doing apple snails--they've been introduced to a couple bodies of water around here (I think due to aquarium dumps).