>Yes, Vitta usnea lives in brackish to freshwater, one of several problems,
>questions, issues, etc. with this species.  Say (1822, who named the species
>Neritina reclivata) wrote, "I found this species in great plenty, inhabiting
>St. John's river in East Florida, from its mouth to Fort Picolata, a
>distance of one hundred miles, where the water was potable."  I would say
>100 miles inland is pretty much beyond tidal influence and can be safely
>called freshwater.  It has been listed by various authors as direct
>developing with crawl away juveniles.  BUT, even this is unclear.  According
>to Andrews (1935:42) this is one of the few nerite species with direct
>development.  Specimens kept in small glass dishes laid eggs that hatched
>into miniature "crawl-away" adults bypassing the more typical veliger stage.
>This has not been observed in my aquariums.  And, young Vitta usnea (<6 mm)
>were collected on turtle grass in three feet of saltwater off Gulf Breeze,
>Florida (Cheshire, 2004); indicating a tolerance for salt water.  There may
>be two forms (there is certainly enough, though not dramatic, variation in
>radular and shell morphology), one that has evolved to a completely
>freshwater existence and the other that has remained diadromous - and is
>still tied to the sea.

I have noticed that old eggcapsule bases are abundant on freshwater
neritids in Fiji, and saw them on images of V. usnea also (I didn't
see any on the V. usnea that I collected, which were WELL outside
tidal reach).

If they develop directly, are their capsules larger than those of other spp?

Is it possible that there are two cryptic species being labelled V.
usnea? This could be tested by... DNA analysis!

>Sounds like a job for DNA analysis. Where is David Campbell when you need
>him?
>
>Incidentally, Thomas Say's old publications (many dating to the 1810's)
>often contain ecologic tidbits in the species descriptions. It's charming --
>and sometimes highly informative.

Good point. You never know when a seemingly-minor observation might
be pivotal in research. You can't have too much data!

>The tendency is to think that everything
>is already known about common species, yet here is an abundant, attractive,

It is, isn't it?

>widespread species that lives in accessible localities at very shallow water
>depths whose basic biology is still very incompletely understood.

Sounds like many molluscs...

>A shell
>collector who wants to make a real contribution to science need look no
>further than to add to our knowledge of such species.

--
Andrew Grebneff
Dunedin
New Zealand
Fossil preparator
<[log in to unmask]>
Seashell, Macintosh, VW/Toyota van nut

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