The compound eye of Scutigera coleoptrata (Linnaeus, 1758) (Chilopoda: Notostigmophora): an ultrastructural reinvestigation that adds support to the Mandibulata concept

Abstract

The lateral compound eye of Scutigera coleoptrata was examined by electron microscopy. Each ommatidium consists of a dioptric apparatus, formed by a cornea and a multipartite eucone crystalline cone, a bilayered retinula and a surrounding sheath of primary pigment and interommatidial pigment cells. With reference to the median eye region, each cone is made up of eight cone segments belonging to four cone cells. The nuclei of the cone cells are located proximally outside the cone near the transition area between distal and proximal retinula cells. The connection between nuclear region and cone segment is via a narrow cytoplasmic strand, which splits into two distal cytoplasmic processes. Additionally, from the nuclear region of each cone cell a single cytoplasmic process runs in a proximal direction to the basement membrane. The bilayered rhabdom is usually made up of the rhabdomeres of 9-12 distal retinula cells and four proximal retinula cell. The pigment shield is composed of primary pigment cells (which most likely secrete the corneal lens) and interommatidial pigment cells. The primary pigment cells underlie the cornea and surround, more or less, the upper third of the crystalline cone. By giving rise to the cornea and by functioning as part of the pigment shield these pigment cells serve a double function. Interommatidial pigment cells extend from the cornea to the basement membrane and stabilise the ommatidium. In particular, the presence of cone cells, primary pigment cells as well as interommatidial pigment cells in the compound eye of S. coleoptrata is seen as an important morphological support for the Mandibulata concept. Furthermore, the phylogenetic significance of these cell types is discussed with respect to the Tetraconata.

Evolution of arthropod visual systems: Development of the eyes and central visual pathways in the horseshoe crabLimulus polyphemusLinnaeus, 1758 (Chelicerata, Xiphosura)

“…It is well documented that the eye fields of Trilobita had a high degree of geometrical organization and that their units in most taxa were arranged in a perfect hexagonal array (e.g., Clarkson, 1975Clarkson, , 1979Cronin, 1989, 1993;Zhang and Clarkson, 1990;Thomas, 2005). In some representatives of the Chilopoda and Diplopoda, new ommatidia are also added in a way that produces a faultless hexagonal array (Mü ller et al, 2003;Harzsch et al, 2006). The symmetrical organization of the ommatidia in hexapod and crustacean eyes has often prompted a comparison with crystalline structures and needs not to be elaborated here (Land and Nilsson, 2001).…”

“…However, eye design in Myriapoda (millipedes and centipedes) is markedly different to that of Tetraconata. They have fields of optical units, the lateral ocelli, each of which is composed of up to several hundreds of cells (e.g., Paulus, 2000;Mü ller et al, 2003;Mü ller and Meyer-Rochow, 2006; for the sake of brevity, eye design of scutigeromorph chilopods will not be touched on here, but the reader is referred Mü ller et al, Harzsch et al, 2006). The pattern of eye growth in Diplopoda (millipedes) closely resembles that in Xiphosura as reported here in that new elements are added to the side of the eye and elongate the rows of earlier generated optical units (Enghof et al, 1993;Harzsch et al, 2006).…”

“…The structure of the lateral eyes has always played an important role in discussions of phylogenetic relationships of Arthropoda (recent contributions e.g., Melzer et al, 1997;Paulus, 2000, Dohle, 2001Richter, 2002;Mü ller et al, 2003;Bitsch and Bitsch, 2005;Harzsch et al, 2005b;Mü ller and Meyer-Rochow, 2006). Furthermore, in recent years, aspects of eye development emerge as important characters for phylogenetic analyses and, therefore, are examined in a variety of arthropods, including Crustacea (Harzsch et al, 1999;Melzer et al, 2000;Hafner and Tokarski, 2001;Harzsch and Walossek, 2001;Wildt and Harzsch, 2002), Hexapoda (Friedrich et al, 1996;Friedrich and Benzer, 2000;Friedrich, 2003), and Myriapoda .…”

Phylogenetisches Symposium Göttingen

“…Nevertheless, the eye structure in Myriapoda is clearly different from that in Tetraconata and there is a dissent about how the myriapodan eye design is evolutionarily related to that of Hexapoda (Paulus 2000, Dohle 2001, Bitsch and Bitsch 2005, Harzsch et al 2005a. A string of recent contributions by Müller and co-authors (Müller et al 2003, Müller and Meyer-Rochow 2006, Müller and Rosenberg 2006 has contributed new arguments to this debate by providing a wealth of new information on the ultrastructure of myriapodan eyes that now allow a sound comparison of eye structure in representatives of this group with the Tetraconata. What is more, information on the development of the lateral eyes take a more and more important role in contributing informative character sets ( Fig.…”

“…In contrast, each ommatidium of the xiphosuran Limulus polyphemus has a clearly different architecture than the tetraconatan ommatidia (corneal lens but no crystalline cone) and is composed of a variable number of more than 300 cells (reviews Fahrenbach 1975, Battelle 2006. The eyes of Myriapoda (millipedes and centipedes) are fields of optical units, the lateral ocelli, each of which is composed of up to several hundreds of cells (e. g. Paulus 2000, Müller et al 2003, Müller and Meyer Rochow 2006, Müller and Rosenberg 2006; for the sake of brevity eye design of scutigeromorph chilopods will not be touched here but the reader is referred Müller et al 2003 andHarzsch et al 2007). The pattern of eye growth in Diplopoda (millipedes) closely resembles that in Xiphosura in that new elements are added to the side of the eye and elongate the rows of earlier generated optical units (Figs.…”