15 January 2008

Gastrocopta contracta


This is probably one of the most widespread and abundant Gastrocopta species in the eastern U.S. According to Pilsbry (1948), its range even extends into Mexico and Cuba. It is also one of the smallest; the shell of this particular specimen was 2.4 mm long.


Although Say, in 1822, described this species as Pupa contracta, he thought it probably belonged to Carychium. Carychium is, of course, a basommatophoran genus. All basommatophoran snails have their eyes at the bases of their tentacles. (Here is a basommatophoran Melampus bullaoides.) Gastrocopta is, on the other hand, a stylommatophoran with its eyes at the tips of its tentacles, as you can see in these pictures.


One peculiar characteristic of G. contracta and many other Gastrocopta species I have seen is that the shells of live snails usually have bits of soil stuck to them. I don't know if that serves a function and how the debris sticks to the shell. Is their periostracum sticky or is the snails' mucus somehow involved in the process?


pascal said...

Gastrocopta that I've run across are often in more xeric habitats - perhaps there's a combination of fluctuating moisture in the soil and the snail's ecology (some are burrowers) that tends to get soil stuck to the periostracum.

Kevin Z said...

your pictures are missing :(


It must have been a temporary glitch. I can see them now.

Kevin Z said...

must have been, i can see them all now. last night none of your pics showed up