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Posted: Dec 27 2006

Puperita pupa (Linnaeus, 1767), And form P. tristis (Orbigny, 1842)

Puperita pupa and P. tristis are presented in various publications as both separate species and with P. tristis as a form of P. pupa. Currently, most workers familiar with these shells do not consider P. tristis a separate species.

The following descriptions are from Abbott's American Seashells, 2nd Ed.

P. pupa - Chalky-white with black, axial, zebra-like stripes                         P. tristis - Black with small white spots. 
Elbow Cay, Abaco, Bahamas. 10mm                                                          Ocean side Tavenier Key, Florida Keys, 9mm 


Aperture light to dark orangish-yellow                                      Aperture tends towards bluish-yellow to bluish-white

Tom Eichhorst is putting the finishing touches on his upcoming book on worldwide Neritidae. The following tidbit of interesting information about P. pupa is taken from his manuscript with his permission and reflects the interesting content we can expect throughout his book.

"Puperita pupa can be found on rocks exposed to direct wave action, in tide pools that are constantly washed with salt water and maintain a fairly consistent salinity, in tide pools that are only filled at extreme high tides and become super saline due to evaporation, and finally in stream-fed tide pools that become almost pure fresh water during rainy periods. The single concession to different salinities seems to be a shift in the pattern and color of the shell. Gunderson and Minton [Puperita tristis (d’Orbigny, 1842)(Gastropoda: Neritidae) is an ecotype of Puperita pupa (Linneaus, 1767), American Malacological Bul. 16(1/2), pp. 13-20] found what they thought were intermediate forms of Puperita pupa living in fresh water pools along side the black form with white spots then known as Puperita tristis (Orbigny, 1842). They decided to experiment and transplanted some normal Puperita pupa (black stripes on white) from salt water to fresh water pools. They also transplanted some P. tristis forms (white spots on black) from fresh water into salt-water pools. Three months later they observed the normal forms had begun laying down shell that was black with white spots and the tristis forms had begun laying down the normal Puperita pupa black stripes on a white shell, both a reversal of the original shell pattern. DNA tests also showed the two to be very much (but not exactly) alike. While certainly not conclusive, this suggested to the two authors that there is a single species involved that changes shell color and pattern in response to environmental cues, especially salinity."

This photo by Tom Eichhorst illustrates Gunderson's and Minton's findings.

The following four specimens (10mm - 11mm) are all from Ohio Key, Florida Keys. The Keys forms almost all differ from the classic P. pupa and only infrequently are the same as the P. tristis described by Abbott.

The following three specimens (2 with side-by-side images and one single image) are all from Boca Chica Key, Florida Keys.  10mm - 12mm

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