|Date: ||Fri, 30 Jul 1999 08:58:53 +1200|
|Reply-To: ||Conchologists of America List <CONCH-L@LISTSERV.UGA.EDU>|
|Sender: ||Conchologists of America List <CONCH-L@LISTSERV.UGA.EDU>|
|From: ||Andrew Grebneff <andrew.grebneff@STONEBOW.OTAGO.AC.NZ>|
|Subject: ||Coiling Abnormalities|
|Content-Type: ||text/plain; charset="us-ascii"|
I am greatly interested in coiling abnormalities, primarily reversals of
rotation (dextral/sinistral), translation along coiling axis
(orthostrophy/isostrophy/hyperstrophy), and also disjunct whorls (open
An orthostrophic gastropod shell (eg Buccinum) grows by accretion of an
apertural rim following a generating curve that is constantly translating
in a "downward" direction along the axis, ie anteriorwards or in the
direction of the siphonal canal, if present.
An isostrophic shell (eg Monoplacophora; there are no truly orthostrophic
gastropods, unless bellerophontids are not monoplacophorans; the freshwater
gastropod Marisa approaches this condition) is planispiral, with no
In hyperstrophic shells (eg the dextral, but apparently-sinistral, Lanistes
and Limacina) the direction of translation is the opposite to that of
orthostrophic forms, ie it is in an "upwards" or posteriorwards direction.
This makes a mockery of the terms "adapical" and "abapical", as each term
can mean either direction, depending on strophy. Nonsiphonostomatous
dextral hyperstrophic shells look much like normal sinistral ones
(hyperstrophy occurs occasionally in specimens of New Zealand's Turbo
smaragdus). A siphonostomatous hyperstrophic shell such as an abnormal
Busycon would look wierd, with sunken spire and the canal wrapped around
the penultimate whorl, looking probably like a giant spiny Bulla (I'd
dearly like to see such a specimen).
It's amazing how few authorities realize the difference between "sinistral"
and "hyperstrophic", regularly confusing the two. Just check in any book
you care to; look up Architectonicidae, Pyramidellidae...these all have
dextral, though hyperstrophic, protoconchs.
Heterostrophic shells such as pyramidellids and other opisthobranchs have a
hyperstrophic protoconch with an orthostrophic teleoconch.
I would appreciate any information on coiling abnormalities, even if it's
only the names of species observed to be abnormal.
I would also like to obtain specimens (especially abnormal Epitoniidae!).
This includes specimens of marine gastropods which are normally sinistral.
At the moment my colection includes very few, including a hyperstrophic
Turbo smaragdus and a sinistral Cirsotrema zelebori.