Development of the nervous system in the
				"head" of Limulus polyphemus (Chelicerata:
				Xiphosura): morphological evidence for a correspondence between the segments of
				the chelicerae and of the (first) antennae of Mandibulata

Mittmann, Beate; Scholtz, Gerhard

doi:10.1007/s00427-002-0285-5

Cited by 118 publications

(83 citation statements)

References 31 publications

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“…According to Hox -gene expression patterns and morphological investigations, the deutocerebrum and the deutocerebral antennae are homologous within Mandibulata and correspond to the chelicere neuromere in Chelicerata [91-93]. Although in some Chelicerata glomerular chemosensory processing areas associated with a sensory appendage are located in the trunk ganglia (e.g.…”

Section: Discussionmentioning

confidence: 99%

Comparative analysis of deutocerebral neuropils in Chilopoda (Myriapoda): implications for the evolution of the arthropod olfactory system and support for the Mandibulata concept

et al. 2012

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BackgroundOriginating from a marine ancestor, the myriapods most likely invaded land independently of the hexapods. As these two evolutionary lineages conquered land in parallel but separately, we are interested in comparing the myriapod chemosensory system to that of hexapods to gain insights into possible adaptations for olfaction in air. Our study connects to a previous analysis of the brain and behavior of the chilopod (centipede) Scutigera coleoptrata in which we demonstrated that these animals do respond to volatile substances and analyzed the structure of their central olfactory pathway.ResultsHere, we examined the architecture of the deutocerebral brain areas (which process input from the antennae) in seven additional representatives of the Chilopoda, covering all major subtaxa, by histology, confocal laser-scan microscopy, and 3D reconstruction. We found that in all species that we studied the majority of antennal afferents target two separate neuropils, the olfactory lobe (chemosensory, composed of glomerular neuropil compartments) and the corpus lamellosum (mechanosensory). The numbers of olfactory glomeruli in the different chilopod taxa ranged from ca. 35 up to ca. 90 and the shape of the glomeruli ranged from spheroid across ovoid or drop-shape to elongate.ConclusionA split of the afferents from the (first) pair of antennae into separate chemosensory and mechanosensory components is also typical for Crustacea and Hexapoda, but this set of characters is absent in Chelicerata. We suggest that this character set strongly supports the Mandibulata hypothesis (Myriapoda + (Crustacea + Hexapoda)) as opposed to the Myriochelata concept (Myriapoda + Chelicerata). The evolutionary implications of our findings, particularly the plasticity of glomerular shape, are discussed.

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Section: Discussionmentioning

confidence: 99%

Comparative analysis of deutocerebral neuropils in Chilopoda (Myriapoda): implications for the evolution of the arthropod olfactory system and support for the Mandibulata concept

et al. 2012

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“…However, the latter author stressed at the same time the lack of other conclusive characters to substantiate serpulid interrelationships. To further assess this issue, neuronal innervation patterns of organ systems may be used as an independent test of homology prior to phylogenetic analysis, as illustrated by recent neuroanatomical studies on euchelicerates and pycnogonids (seaspiders) [63-65]. In addition, the comprehensive studies on the cephalic nervous system of polychaetes by Orrhage [7-9] highlight the relevance of such investigations for the homologization of anterior appendages in annelids.…”

Section: Discussionmentioning

confidence: 99%

Neurogenesis suggests independent evolution of opercula in serpulid polychaetes

Brinkmann

Wanninger

2009

BMC Evol Biol

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BackgroundThe internal phylogenetic relationships of Annelida, one of the key lophotrochozoan lineages, are still heavily debated. Recent molecular analyses suggest that morphologically distinct groups, such as the polychaetes, are paraphyletic assemblages, thus questioning the homology of a number of polychaete morphological characters. Serpulid polychaetes are typically recognized by having fused anterior ends bearing a tentacular crown and an operculum. The latter is commonly viewed as a modified tentacle (= radiole) and is often used as an important diagnostic character in serpulid systematics.ResultsBy reconstructing the developmental neuroanatomy of the serpulid polychaete Spirorbis cf. spirorbis (Spirorbinae), we found striking differences in the overall neural architecture, the innervation pattern, and the ontogenetic establishment of the nervous supply of the operculum and the radioles in this species. Accordingly, the spirorbin operculum might not be homologous to the radioles or to the opercula of other serpulid taxa such as Serpula and Pomatoceros and is thus probably not a part of the tentacular crown.ConclusionWe demonstrate that common morphological traits such as the prostomial appendages may have evolved independently in respective serpulid sublineages and therefore require reassessment before being used in phylogenetic analyses. Our findings corroborate recent molecular studies that argue for a revision of serpulid systematics. In addition, our data on Spirorbis neurogenesis provide a novel set of characters that highlight the developmental plasticity of the segmented annelid nervous system.

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“…Microtubule acetylation is non-uniformly distributed in neurons [110] and recent evidence suggests a critical role of acetylation of alpha-tubulin in neuronal migration, dendrite projections and arborizations [112]. Several studies have already used acetylated alpha-tubulin labelling to follow the establishment of the major axonal pathways during the development of different arthropods [5,7,12,13,15,113], including pycnogonids [114,115]. In pycnogonids, the cytoskeleton of all embryonic cells is intensely labelled by a monoclonal antibody against acetylated alpha-tubulin (mouse mab 6–11 B-1, Sigma, #T6793, dilution 1:100), which allows assessment of cell shapes in the ectoderm during development.…”

Section: Methodsmentioning

confidence: 99%

Embryonic neurogenesis in Pseudopallene sp. (Arthropoda, Pycnogonida) includes two subsequent phases with similarities to different arthropod groups

Brenneis

Stollewerk

Scholtz

2013

EvoDevo

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BackgroundStudies on early neurogenesis have had considerable impact on the discussion of the phylogenetic relationships of arthropods, having revealed striking similarities and differences between the major lineages. In Hexapoda and crustaceans, neurogenesis involves the neuroblast, a type of neural stem cell. In each hemi-segment, a set of neuroblasts produces neural cells by repeated asymmetrical and interiorly directed divisions. In Euchelicerata and Myriapoda, neurogenesis lacks neural stem cells, featuring instead direct immigration of neural cell groups from fixed sites in the neuroectoderm. Accordingly, neural stem cells were hitherto assumed to be an evolutionary novelty of the Tetraconata (Hexapoda + crustaceans). To further test this hypothesis, we investigated neurogenesis in Pycnogonida, or sea spiders, a group of marine arthropods with close affinities to euchelicerates.ResultsWe studied neurogenesis during embryonic development of Pseudopallene sp. (Callipallenidae), using fluorescent histochemical staining and immunolabelling. Embryonic neurogenesis has two phases. The first phase shows notable similarities to euchelicerates and myriapods. These include i) the lack of morphologically different cell types in the neuroectoderm; ii) the formation of transiently identifiable, stereotypically arranged cell internalization sites; iii) immigration of predominantly post-mitotic ganglion cells; and iv) restriction of tangentially oriented cell proliferation to the apical cell layer. However, in the second phase, the formation of a central invagination in each hemi-neuromere is accompanied by the differentiation of apical neural stem cells. The latter grow in size, show high mitotic activity and an asymmetrical division mode. A marked increase of ganglion cell numbers follows their differentiation. Directly basal to the neural stem cells, an additional type of intermediate neural precursor is found.ConclusionsEmbryonic neurogenesis of Pseudopallene sp. combines features of central nervous system development that have been hitherto described separately in different arthropod taxa. The two-phase character of pycnogonid neurogenesis calls for a thorough reinvestigation of other non-model arthropods over the entire course of neurogenesis. With the currently available data, a common origin of pycnogonid neural stem cells and tetraconate neuroblasts remains unresolved. To acknowledge this, we present two possible scenarios on the evolution of arthropod neurogenesis, whereby Myriapoda play a key role in the resolution of this issue.

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Development of the nervous system in the "head" of Limulus polyphemus (Chelicerata: Xiphosura): morphological evidence for a correspondence between the segments of the chelicerae and of the (first) antennae of Mandibulata

Cited by 118 publications

References 31 publications

Comparative analysis of deutocerebral neuropils in Chilopoda (Myriapoda): implications for the evolution of the arthropod olfactory system and support for the Mandibulata concept

Comparative analysis of deutocerebral neuropils in Chilopoda (Myriapoda): implications for the evolution of the arthropod olfactory system and support for the Mandibulata concept

Neurogenesis suggests independent evolution of opercula in serpulid polychaetes

Embryonic neurogenesis in Pseudopallene sp. (Arthropoda, Pycnogonida) includes two subsequent phases with similarities to different arthropod groups

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