Ultrastructural aspects of nervous-system and statocyst morphogenesis during embryonic development of Convoluta psammophila (Turbellaria, Acoela)

Ferrero, Enrico; Bedini, Celina

doi:10.1007/bf00027592

Cited by 26 publications

(2 citation statements)

References 20 publications

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“…The term endonal brain was introduced based on the assumption that neurons surrounding the statocyst in acoel and spiralian brains are homologous. However, based on developmental studies [ 39 , 40 ], structural properties (no SLI and RFLI in Acoelomorpha unlike in Platyhelminthes [ 7 , 41 ]), and phylogenetic considerations (see background), it can be concluded that these assumptions were wrong.…”

Section: Discussionmentioning

confidence: 99%

The nervous system of Isodiametra pulchra (Acoela) with a discussion on the neuroanatomy of the Xenacoelomorpha and its evolutionary implications

Achatz

Martinez

2012

Front Zool

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IntroductionAcoels are microscopic marine worms that have become the focus of renewed debate and research due to their placement at the base of the Bilateria by molecular phylogenies. To date, Isodiametra pulchra is the most promising “model acoel” as it can be cultured and gene knockdown can be performed with double-stranded RNA. Despite its well-known morphology data on the nervous system are scarce. Therefore we examined this organ using various microscopic techniques, including histology, conventional histochemistry, electron microscopy, and immunocytochemistry in combination with CLSM and discuss our results in light of recently established phylogenies.ResultsThe nervous system of Isodiametra pulchra consists of a bilobed brain with a dorsal posterior commissure, a frontal ring and tracts, four pairs of longitudinal neurite bundles, as well as a supramuscular and submuscular plexus. Serotonin-like immunoreactivity (SLI) is displayed in parts of the brain, the longitudinal neurite bundles and a large part of the supramuscular plexus, while FMRFamide-like immunoreactivity (RFLI) is displayed in parts of the brain and a distinct set of neurons, the longitudinal neurite bundles and the submuscular plexus. Despite this overlap SLI and RFLI are never colocalized. Most remarkable though is the presence of a distinct functional neuro-muscular system consisting of the statocyst, tracts, motor neurons and inner muscles, as well as the presence of various muscles that differ with regard to their ultrastructure and innervation.ConclusionsThe nervous system of Isodiametra pulchra consists of an insunk, bilobed brain, a peripheral part for perception and innervation of the smooth body-wall musculature as well as tracts and motor neurons that together with pseudostriated inner muscles are responsible for steering and quick movements. The insunk, bilobed brains with two to three commissures found in numerous acoels are homologous and evolved from a ring-commissural brain that was present in the stem species of acoelomorphs. The acoelomorph brain is bipartite, consisting of a Six3/6-dependend animal pole nervous system that persists throughout adulthood and an axial nervous system that does not develop by exhibiting a staggered pattern of conserved regulatory genes as in other bilaterians but by a nested pattern of these genes. This indicates that acoelomorphs stem from an ancestor with a simple brain or with a biphasic life cycle.

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Section: Discussionmentioning

confidence: 99%

The nervous system of Isodiametra pulchra (Acoela) with a discussion on the neuroanatomy of the Xenacoelomorpha and its evolutionary implications

Achatz

Martinez

2012

Front Zool

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“…The membrane of this vacuole is thought to have a rich repertoire of ion pumps, transporters and exchangers [31,37]. Some lithocytes have mitochondria adhered to the crystal [39,40]. In placozoan crystal cells, both immature and mature, mitochondria surround the vacuole enclosing the crystal ( [3,18]; present study) suggesting that mitochondria could be essential for biomineralization process.…”

Section: Discussionmentioning

confidence: 65%

Differentiation of Crystal Cells, Gravity-Sensing Cells in the Placozoan Trichoplax adhaerens

Mayorova

2021

JMSE

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Trichoplax adhaerens are simple animals with no nervous system, muscles or body axis. Nevertheless, Trichoplax demonstrate complex behaviors, including responses to the direction of the gravity vector. They have only six somatic cell types, and one of them, crystal cells, has been implicated in gravity reception. Multiple crystal cells are scattered near the rim of the pancake-shaped animal; each contains a cup-shaped nucleus and an intracellular crystal, which aligns its position according to the gravity force. Little is known about the development of any cell type in Trichoplax, which, in the laboratory, propagate exclusively by binary fission. Electron and light microscopy were used to investigate the stages by which crystal cells develop their mature phenotypes and distributions. Nascent crystal cells, identified by their possession of a small crystal, were located farther from the rim than mature crystal cells, indicating that crystal cells undergo displacement during maturation. They were elongated in shape and their nucleus was rounded. The crystal develops inside a vacuole flanked by multiple mitochondria, which, perhaps, supply molecules needed for the biomineralization process underlying crystal formation. This research sheds light on the development of unique cells with internal biomineralization and poses questions for further research.

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Comparative morphology of statocysts in the Plathelminthes and the Xenoturbellida

Ehlers¹

1991

Turbellarian Biology

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Ultrastructural aspects of nervous-system and statocyst morphogenesis during embryonic development of Convoluta psammophila (Turbellaria, Acoela)

Cited by 26 publications

References 20 publications

The nervous system of Isodiametra pulchra (Acoela) with a discussion on the neuroanatomy of the Xenacoelomorpha and its evolutionary implications

The nervous system of Isodiametra pulchra (Acoela) with a discussion on the neuroanatomy of the Xenacoelomorpha and its evolutionary implications

Differentiation of Crystal Cells, Gravity-Sensing Cells in the Placozoan Trichoplax adhaerens

Comparative morphology of statocysts in the Plathelminthes and the Xenoturbellida

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