Research Training ProgramSmithsonian
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| Tomasz J. Proszynski University of Warsaw Warsaw, Poland Jonathan A. Coddington "Working side by side with the most prominent scientists in a friendly atmosphere made this program magnificent and unforgettable." |
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Comparative study of tapetum in spiders
ABSTRACT
Spiders are important predators of arthropods, and, for example, help to regulate many agricultural pests. Spiders are adapted to many habitats and forage in various ways. Most wait in ambush or use webs, but some hunt actively for prey. Eyes are obviously important in a few groups, but the general assumption has been that sedentary predators do not rely principally on their eyes to capture prey. Terrestrial adaptations in arachnid ocelli occurred independently of insects and crustaceans, and are thus an independent solution to the problem of vision on land. Secondary spider eyes usually possess a light-reflecting tapetum that concentrates light on the retina to improve perception of movement and shape under dim light. This study designed new techniques for the investigation of tapetal diversity, and presents evidence that tapetal diversity is more complex than previously appreciated. Digital pictures of tapeta were collected from over 35 species, 26 genera, and 17 families of spiders. Three types of tapetum have been previously described: "primitive", canoe-, and grate-shaped. Additional types of unusual tapeta (some observed by previous authors) were discovered. A study was also done on taxa whose tapetal morphology were previously unknown. In some cases, the tapetum structure observed in this study conflicts with descriptions in the literature. Tapeta were found that were intermediate between canoe and "primitive" type. Similar derived tapetum morphologies seem to have originated convergently in a number of families. The phylogeny of spiders is currently subject to intensive investigation. Variation in tapetal morphology may supply additional systematic characters, and will certainly enhance understanding of the evolution of spider visual systems.
This research was made possible by a grant from the Smithsonian Women's Committee.