Phylogeny of the Myriapoda – Crustacea – Insecta: a new attempt using photoreceptor structure*

By H. Paulus. 2000

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According to molecular sequence data Crustacea and not Myriapoda seem to be the sister-group to Insecta. This makes it necessary to reconsider how the morphology of their eyes fit with these new cladograms. Homology of facetted eye structures in Insecta (Hexapoda in the sense of Ento- and Ectognatha) and Crustacea is clearly supported by identical numbers of cells in an ommatidium (two corneageneous or primary pigment cells, four Semper cells which build the crystalline cone and primarily eight retinula cells). These cell numbers are retained even when great functional modification occurs, especially in the region of the dioptric apparatus. There are two different possibilities to explain differences in eye structure in Myriapoda depending on their phylogenetic position in the cladogram of Mandibulata. In the traditional Tracheata cladogram, eyes of Myriapoda must be secondarily modified. This modification can be explained using the different evolutionary pathways of insect facetted eyes to insect larval eyes (stemmata) as an analogous model system. Comparative morphology of larval insect eyes from all holometabolan orders shows that there are several evolutionary pathways which have led to different types of stemmata and that the process always involved the breaking up the compound eye into individual larval ommatidia. Further evolution led on many occasions to so-called fusion-stemmata that occur convergently in each holometabolic order and reveals, in part, great structural similarities to the lateral ocelli of myriapods. As myriapodan eyes cannot be regarded as typical mandibulate ommatidia, their structure can be explained as a modified complex eye evolved in a comparable way to the development to the fusion-stemmata of insect larvae. The facetted eyes of Scutigera (Myriapoda, Chilopoda) must be considered as secondarily reorganized lateral myriapodan stemmata, the so-called ‘pseudo-compound eyes’. New is a crystalline cone-like vitreous body within the dioptric apparatus. In the new cladogram with Crustacea and Insecta as sister-groups however, the facetted eyes of Scutigera can be interpreted as an old precursor of the Crustacea – Insecta facetted eye with modified ommatidia having a four-part crystalline cone, etc. as a synapomorphy. Lateral ocelli of all the other Myriapoda are then modified like insect stemmata. The precursor is then the Scutigera-Ommatidium. In addition further interpretations of evolutionary pathways of myriapodan morphological characters are discussed.

Subfields: Cellular and Molecular Neuroscience, Genetics, Oceanography

View Paper: https://www.semanticscholar.org/paper/fc3f381dcb8c48bfdccbd48b5a0b25dbd430b30d

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Citations in the corpus

Organization and evolutionary trends of primary olfactory brain centers in Tetraconata (Crustacea+Hexapoda) (2005, background): “, 2004), morphological evidence for or against a Hexapoda/Crustacea clade is still inconclusive (Paulus, 2000; Klass and Kristensen, 2001; Bitsch and Bitsch, 2004).”
Adding mitochondrial sequence data (16S rRNA and cytochrome c oxidase subunit I) to the phylogeny of centipedes (Myriapoda: Chilopoda): an analysis of morphology and four molecular loci (2004, background): “Although the status of Myriapoda, Atelocerata and Tetraconata are contentious issues (see Dohle 1997, 1998, 2001; Paulus 2000; Richter 2002), only the brain data of Loesel et al.”
The Tetraconata concept: hexapod-crustacean relationships and the phylogeny of Crustacea (2002, background): “These ‘vitreous bodies’ can be interpreted as reduced cone cells (Paulus 2000), and the number four is indeed suggestive.”
The compound eye of Scutigera coleoptrata (Linnaeus, 1758) (Chilopoda: Notostigmophora): an ultrastructural reinvestigation that adds support to the Mandibulata concept (2003, methodology): “The presence of primary pigment cells resembles the condition in hexapods, in which also the same cell type secretes the cornea and produces a primary pigment shield around the cone, whereas in crustaceans the corneagenous cells do not contain pigments (Paulus 1979, 2000).”