12 May 2008

Dissection of Truncatella caribaeensis - Part 2

Yesterday's post was about the removal of the shell of a Truncatella caribaeensis specimen in preparation for dissection. The subsequent dissection went well and I was able to see what I wanted to see.

Here is the dissected snail after the mantle was cut open and moved aside.

TruncatellaDissection4

The white, folded organ labeled "penis" is, well, the penis of the snail. It is about a half of the spiraled body length of the snail (talk about penis enlargement).

What interested me more was the row of tiny white flaps to the left of the penis. They constitute the ctenidium or the gill of Truncatella caribaeensis. Here is a larger view.

TruncatellaDissection5

This snail spends its entire life cycle on land very close to the sea, but out of it, unless it is carried away by the waves or the tides, and because of that it is considered a land snail. But it still, as we see here, retains the gill of its aquatic ancestors from whom it evolved. On the other hand, there are other species of snails that live on land alongside Truncatella, for example, Melampus bullaoides, that lost their gills a long time ago and obtain their oxygen thru their vascularized mantle, or "lung." But they nevertheless return to the sea to reproduce, because they still have planktonic larvae as did their ancestors.

Evolution works in mysterious ways.


6 comments:

Anonymous said...

Excellent Aydin. I was away for 3 weeks, got back about a week ago and very much enjoyed reading all of your blog entries. Good work with the dissection! This is a pretty small snail!

Susan H.

Eric Heupel said...

Aydin, love the dissection posts, what is the sexual/reproductive strategy of this snail?

AYDIN ÖRSTAN said...

Sexes are separate. I don't know if mating has ever been observed. One species, probably T. caribaeensis (taxonomy has been confused), was observed to lay eggs in captivity (Ross, AMU Annual Reports, 1969). The eggs hatch into small snails; there is no planktonic stage.

Anonymous said...

Hi,
I'm a biology instructor thinking about snail dissection for my class and came across your blogs. Looks really interesting. We have land snails here in CA that are about up to 1 inch in shell size. Would you mind commenting whether the shell dissolving method you used would work? THanks-
Margaret Lee

AYDIN ÖRSTAN said...

Margaret: Shell dissolving works best for the smallest snails, especially if the snail's body is completely inside the shell. For anything larger than ~5 mm, you can break the shell away with fine tweezers. For larger snails on the order of an inch or so, it would take too long to dissolve the shell in acid & it is not necessary to do so. Large shells can be broken away with strong forceps. Start at the lip & work your way back until enough of the snail's body is exposed for dissection.

Anonymous said...

Aydin,
Thank you for your reply! I'm new to blogging, and I actually forgot to check back--sorry. Classes started in late Jan. A few weeks ago the weather here warmed up such that our snails are back out. I have a few that I may dissect soon. --Margaret