Morphological study on the form and number of eyes in scorpions and spiders


Department of Biology, Collage of Education for Pure Science (Ibn Al-Haitham), University of Baghdad, Baghdad, Iraq



Scorpions and spiders belong to the class Arachnida in phylum Arthropoda. Scorpions are easily distinguished by median eyes on obvious the center of the carapace and have one pair, and lateral eyes have 2-8 in some species. Scorpions do not have good eyesight so the median eyes have always been simple and they are more sensitive than the lateral pairs. They have anterior median eyes (AME) with narrow field of view and pairs of lateral eyes (LE) with more sensitivity and response to light. Family Buthidae have 2-6 lateral eyes in Compsobuthus Mesobuthus, Hottentotta, while  Vaejovidae, Chactidae and Chaerilidae have 2 pairs of lateral eyes. In addition, 3 pairs are found in Orthochirus and  Androctonus. Spiders have six eyes in family Pholicidae, Sicariidae, Araneidae, Salticidae, while  eight eyes in Theridiidae, Lycosidae   and some with two eyes or four in the carapace of the prosoma. Spider have anterior median eyes, anterior lateral eyes, posterior median eyes, or posterior lateral eyes. Scorpions and Spider eyes are not compound but simple. There is one lens for each eye. Spiders have poor vision, not able to see light and darkness. Scorpion and spider taxonomy is based on the forms and number of eyes. So, the reasons to study these organisms are important in studies of medical, ecology, morphology and taxonomy.  and it is a little known about their biology and  fauna.


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