title: Light and dark adaptation mechanisms in the compound eyes of Myrmecia ants that occupy discrete temporal niches.
abstract: Ants of the Australian genus Myrmecia partition their foraging niche temporally, allowing them to be sympatric with overlapping foraging requirements. We used histological techniques to study the light and dark adaptation mechanisms in the compound eyes of diurnal (Myrmecia croslandi), crepuscular (M. tarsata, M. nigriceps) and nocturnal ants (M. pyriformis). We found that, except in the day-active species, all ants have a variable primary pigment cell pupil that constricts the crystalline cone in bright light to control for light flux. We show for the nocturnal M. pyriformis that the constriction of the crystalline cone by the primary pigment cells is light dependent whereas the opening of the aperture is regulated by an endogenous rhythm. In addition, in the light-adapted eyes of all species, the retinular cell pigment granules radially migrate towards the rhabdom, a process that in both the day-active M. croslandi and the night-active M. pyriformis is driven by ambient light intensity. Visual system properties thus do not restrict crepuscular and night-active ants to their temporal foraging niche, while day-active ants require high light intensities to operate. We discuss the ecological significance of these adaptation mechanisms and their role in temporal niche partitioning.
authors.affiliation: Department of Biological Sciences, Macquarie University, 205 Culloden Road, Sydney, NSW 2109, Australia Research School of Biology, The Australian National University, 46 Sullivans Creek Road, Canberra, ACT 2601, Australia ajay.narendra@mq.edu.au.
authors.forename: Ajay
authors.identifier: 0000-0002-1286-5373
authors.initials: A
authors.lastname: Narendra
authors.affiliation: Research School of Biology, The Australian National University, 46 Sullivans Creek Road, Canberra, ACT 2601, Australia.
authors.forename: Birgit
authors.initials: B
authors.lastname: Greiner
authors.affiliation: Research School of Biology, The Australian National University, 46 Sullivans Creek Road, Canberra, ACT 2601, Australia Department of Biology, University of Lund, Lund S-22362, Sweden.
authors.forename: Willi A
authors.initials: WA
authors.lastname: Ribi
authors.affiliation: Research School of Biology, The Australian National University, 46 Sullivans Creek Road, Canberra, ACT 2601, Australia.
authors.forename: Jochen
authors.initials: J
authors.lastname: Zeil
mesh_terms: D000818:Animals; D001000:Ants / Q000502:physiology* / Q000528:radiation effects*; D002940:Circadian Rhythm / Q000528:radiation effects; D054910:Compound Eye, Arthropod / Q000502:physiology* / Q000528:radiation effects* / Q000648:ultrastructure; D003623:Dark Adaptation / Q000528:radiation effects; D005247:Feeding Behavior / Q000528:radiation effects; D008027:Light; D010860:Pigments, Biological / Q000378:metabolism; D011680:Pupil / Q000502:physiology / Q000528:radiation effects; D013045:Species Specificity; D061350:Sympatry; D013997:Time Factors
chemical_list: D010860:Pigments, Biological
keywords: Crystalline cone; Pupil; Rhabdom; Screening pigment