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The Larval Eye of Nannochoristid Scorpionflies (Insecta, Mecoptera)
Author(s) -
Melzer Roland R.,
Paulus Hannes F.,
Kristensen Niels P.
Publication year - 1994
Publication title -
acta zoologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.414
H-Index - 37
eISSN - 1463-6395
pISSN - 0001-7272
DOI - 10.1111/j.1463-6395.1994.tb01207.x
Subject(s) - ommatidium , biology , simple eye in invertebrates , compound eye , instar , zoology , larva , anatomy , evolutionary biology , botany , physics , optics
The stemmata of last–instar Nannochorista larvae are compound eyes composed of 10 or more ommatidia. Each ommatidium has four Semper cells, four distal and four proximal retinula cells which form a cruciform and layered rhabdom. The ommatidia are separated by epidermal cells (possibly rudimentary pigment cells). Corneal lenses are lacking. At the posterior edge, aberrant stemma units may be present which lack a dioptric apparatus and have a star–shaped rhabdom composed of at least six retinula cells. The stemmata of Nannochorista appear to be derived from stemmata of the Panorpa ‐type (Mecoptera‐Panorpidae). Differences between the stemmata of Nannochorista and Panorpa can be explained as adaptations to aquatic life (flat cornea) or as regression. A compound larval eye is ascribed to the ground plan of the Mecoptera sensu lato and is considered a genuine plesiomorphy. The identical basic number (seven) of stemmata in the Neuropteroid/Coleoptera assemblage, Amphiesmenoptera and some Mecoptera (Bittacidae, Boreidae) is attributed to parallel evolution.