New Zealand Journal of Marine and Freshwater Research abstracts
Anatomical and ultrastructural comparison of the eyes of two species of
aquatic, pulmonate gastropods: the bioluminescent Latia neritoides
and the non-luminescent Ancylus fluviatilis
V. BENNO MEYER-ROCHOW1
MARINA V. BOBKOVA2
Department of Biology
University of Oulu
PL 8000, SF-90401 Oulu
Finland
1Present address: International University Bremen (IUB),
Faculty of Engineering and Science, Department of Biology, Campus Ring 1,
D-28759 Bremen, Germany. email: vmr@cc.oulu.fi
2Present address: Sechenov Institute of
Evolutionary
Physiology and Biochemistry, Russian Academy of Sciences, St Petersburg,
Russia.
Abstract Light-adapted eyes of two freshwater gastropods with
similar habitat preferences (Latia neritoides (Gray 1850) and Ancylus
fluviatilis (Müller 1774)) were compared with each other in relation
to optics, anatomy, and ultrastructure. Individuals of L. neritoides not
only possess significantly larger eyes than similarly sized A.
fluviatilis, they also have a more voluminous layer of photoreceptive
membranes and appear capable of discerning at least some crude shapes. The eye
of A. fluviatilis, on the other hand, has a very shallow retina which is
so closely apposed to the lens that it can be little more than an indicator of
light and darkness. Both types of eye are generously endowed with screening
pigment granules and exhibit no signs of light-induced damage. Although the
lenticular F-values for L. neritoides (1.78) and A. fluviatilis
(1.74) alone are hardly indicative of an adaptation to a dark environment, the
greater amount of photic vesicles and the substantial development of muscle
fibres in the eye of L. neritoides suggest that the latter can adjust
its vision more rapidly to changing light levels than that of A.
fluviatilis. Since L. neritoides (but not A. fluviatilis) has
the ability to secrete a bright green luminescent mucus, a faster accommodation
system would serve the species well. There is, however, no proof that in
Latia bioluminescence alone has been responsible for the development of
a more capable eye. Most of the differences between the eyes of L.
neritoides and A. fluviatilis can be explained by the distinctly
greater nocturnal activity of L. neritoides in combination with the
ability to produce bright light in the latter species.
Keywords vision; eye; photoreceptor; bioluminescence;
mollusca; gastropoda; New Zealand; freshwater; limpet; ecophysiology; electron
microscopy
M00064
Received 31 August 2000; accepted 19 February 2001
PDF file of entire paper: medium quality (3677K); (scanned from paper original: notes about this process)
This year's abstracts |
Journal home page |
All abstracts |
Publishing home page
