When Daphnia pulex are presented on one side of their visual field with diffuse, large-area linearly polarized light with a horizontal e-vector and on the other side of their visual field with large-area polarized light with a lower degree of polarization, they swim towards the place with the higher degree of polarization. The response is intensity-invariant: Daphnia pulex swim towards the place of maximal polarization regardless of which side of their visual field has the higher intensity of light. As a result of Rayleigh scattering in a pond, the light surrounding the Daphnia is polarized and has a horizontal e-vector. Near the shore, polarization is not homogeneous. The light seen in the direction of the open water has a higher degree of polarization than that seen in the direction towards the shore. Therefore, in a pond, swimming towards the place with the highest degree of polarization leads the Daphnia away from the shore. For Daphnia, this response explains a mechanism that underlies the well-known phenomenon of ‘shore flight’, the active departure of small pelagic crustaceans from shore zones.

Frost
J.
(
1974
).
Eye movements in Daphnia pulex (de Geer)
.
J. Exp. Biol
62
,
175
–.
Kriska
G.
,
Horvath
G.
,
Andrikovics
S.
(
1998
).
Why do mayflies lay their eggs en masse on dry asphalt roads? Water-imitating polarized light from asphalt attracts Ephemeroptera
.
J. Exp. Biol
201
,
2273
–.
Schwind
R.
(
1985
).
Sehen unter und uber Wasser, Sehen von Wasser: Das Sehsystem eines Wasserinsektes
.
Naturwissenschaften
72
,
343
–.
von Frisch
K.
(
1949
).
Die Polarisation des Himmelslichtes als orientierender Faktor bei den Tänzen der Bienen
.
Experientia
5
,
142
–.
Wildermuth
H.
(
1998
).
Dragonflies recognize the water of rendezvous and oviposition sites by horizontally polarized light: A behavioural field test
.
Naturwissenschaften
85
,
297
–.
This content is only available via PDF.