TY - JOUR
T1 - Fixed focal-length optics in pulmonate snails (Mollusca, Gastropoda)
T2 - Squaring phylogenetic background and ecophysiological needs (II)
AU - Gál, József
AU - Bobkova, Marina V.
AU - Zhukov, Valery V.
AU - Shepeleva, Irina P.
AU - Meyer-Rochow, V. Benno
PY - 2004
Y1 - 2004
N2 - Our results suggest that freshwater pulmonates like Lymnaea stagnalis, Radix peregra, Physa fontinalis, and Planorbarius corneus have inherited from their terrestrial ancestors eyes with a spherical, immobile lens with fixed focal-length optics. Unable to change the dioptric apparatus to form an image under water, modifications to the retina had to occur if sharp vision was required. Computer-assisted calculations and 3-D eye reconstructions demonstrate that the photoreceptors in the deeper, ventral pit are in a position to perceive focused images under water. Vision in air, however, would favour photoreceptive cells located in the shallower, dorsal pit. On the basis of histological, ethological, and optical comparisons, we conclude that the eyes in L. stagnalis and R. peregra, species that are known to escape and seek temporary refuge above the water surface, are well adapted to function in water as well as air, but that the eyes in P. fontinalis and Pl. corneus are less modified from those of their terrestrial ancestors. We also conclude that good resolving power may be of greater importance in the aquatic pulmonates than the terrestrial species, since the former have to locate thin, vertical stems of reeds and sedges to ascend in order to reach the surface to breathe.
AB - Our results suggest that freshwater pulmonates like Lymnaea stagnalis, Radix peregra, Physa fontinalis, and Planorbarius corneus have inherited from their terrestrial ancestors eyes with a spherical, immobile lens with fixed focal-length optics. Unable to change the dioptric apparatus to form an image under water, modifications to the retina had to occur if sharp vision was required. Computer-assisted calculations and 3-D eye reconstructions demonstrate that the photoreceptors in the deeper, ventral pit are in a position to perceive focused images under water. Vision in air, however, would favour photoreceptive cells located in the shallower, dorsal pit. On the basis of histological, ethological, and optical comparisons, we conclude that the eyes in L. stagnalis and R. peregra, species that are known to escape and seek temporary refuge above the water surface, are well adapted to function in water as well as air, but that the eyes in P. fontinalis and Pl. corneus are less modified from those of their terrestrial ancestors. We also conclude that good resolving power may be of greater importance in the aquatic pulmonates than the terrestrial species, since the former have to locate thin, vertical stems of reeds and sedges to ascend in order to reach the surface to breathe.
KW - Eye
KW - Lens
KW - Optical modelling
KW - Photoreception
KW - Visual behaviour
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U2 - 10.1111/j.1744-7410.2004.tb00147.x
DO - 10.1111/j.1744-7410.2004.tb00147.x
M3 - Article
AN - SCOPUS:3242656239
SN - 1077-8306
VL - 123
SP - 116
EP - 127
JO - Invertebrate Biology
JF - Invertebrate Biology
IS - 2
ER -