Fatty acid compositions of arthropod and cephalopod photoreceptors: interspecific,seasonal and developmental studies |
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Authors: | E Eguchi Y Ogawa K Okamoto K Mochizuki |
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Institution: | (1) Department of Biology, Yokohama City University, 22-2 Seto, Kanazawa-ku, 236 Yokohama, Japan;(2) Department of Chemistry, Yokohama City University, 22-2 Seto, Kanazawa-ku, 236 Yokohama, Japan |
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Abstract: | Fatty acid compositions of the compound eyes of insects (soldier-bug, Hemiptera, and silk moth, Lepidoptera), crustaceans
(crayfish and grapsid crab, Decapoda) and inner and outer segments of visual cells of a squid (Cephalopoda, Mollusca) were
analyzed by gaschromatography for interspecific comparison. Fatty acid compositions showed great variation among species.
In insect compound eyes, 16:0 and 18:0 were the main saturated fatty acids, and 18:1 was the dominant unsaturated fatty acid.
Silk moth eyes contained, in addition, considerable amounts of 18:2 and 20:5. In crustacean compound eyes, the main saturated
fatty acids were 16:0 and 18:0, and 14:0 (5.0%) was only detected in grapsid crabs; the main unsaturated fatty acids were
20:4, 20:5 and 22:6. Both whole eyes and rhabdom fraction of crayfish showed similar profiles of fatty acid compositions.
Both inner and outer segments of squid retinae were characterized by high amounts of unsaturated fatty acids, especially 22:6.
Compound eyes of grapsid crabs were used for the experiments on seasonal changes of fatty acid compositions. UFA/SFA ratios
(weight in % of unsaturated fatty acids saturated fatty acids) were lowest (1.0) in July and highest (2.5) in March, and unsaturation
indexes (average number of double bonds per molecule) were lowest (1.5) in July and highest (2.3) in March. Fatty acids 18:0
and 20:1 showed a significant correlation with the changes of seasonal temperature. Fatty acid analysis of the developing
compound eyes of silk moths during the pupal stage revealed that eicosapentanoic acid (20:5) increased remarkably in parallel
with the development of photoreceptive membranes, the rhabdoms. This suggests that eicosapentaenoic acid may play an important
role in formation and function of rhabdoms. |
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Keywords: | Fatty acid composition Compound eyes Rhabdom Gas-chromatography Squid Doryteuthis |
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