A commissural brain! The pattern of 5-HT immunoreactivity in Acoela (Plathelminthes)

Raikova, Olga I.; Reuter, Maria; Kotikova, E. A.; Gustafsson, Margaretha K. S.

doi:10.1007/s004350050058

Cited by 72 publications

(64 citation statements)

References 20 publications

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“…The overall configuration of the brain largely resembles what has been found in similar studies of a range of Gnathostomulida (Mü ller and Sterrer, 2004), various Platyhelminthes (Rhabdocoela, Tricladida), Acoela (Reisinger, 1972;Raikova et al, 1998), and Annelida (Mü ller and Westheide, 2002). As in many of these taxa, a serotonergic dorsal and ventral commissure of the circum-esophageal connective may be recognized in Diurodrilus sp.…”

Section: Nervous Systemsupporting

confidence: 76%

“…The organization of the musculature and nervous system is often regarded as a key indicator of phylogenetic affinity among protostomes (Raikova et al, 1998;Hessling and Westheide, 2002;Wanninger et al, 2005). We document here the nervous system as well as the musculature of several Diurodrilus species using confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM).…”

mentioning

confidence: 98%

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Is Diurodrilus an annelid?

Worsaae

Rouse

2008

Journal of Morphology

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Interstitial marine meiofaunal worms of the genus Diurodrilus have always been considered part of Annelida, either as basal or derived, though generally with reference to Dinophilidae. New evidence shows that Diurodrilus has a unique anatomy, and lacks key annelid features, possibly even segmentation. We assessed the systematic position of Diurodrilus among other protostome animals via light microscopy, confocal laser scanning microscopy, and transmission electron microscopy studies of anatomy, focusing on musculature, the nervous system, as well as molecular sequence data. We show that there is little morphological or molecular evidence to support a relationship with Dinophilidae or any other annelids. Diurodrilus has some similarities to Micrognathozoa, though the latter shows complex jaws. On the basis of the configuration of the nervous system and the cuticle we regard Diurodrilus to belong to Spiralia, possibly close to Annelida; however, until further evidence is acquired it should be regarded as incertae sedis in this large animal clade.

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Section: Nervous Systemsupporting

confidence: 76%

mentioning

confidence: 98%

Is Diurodrilus an annelid?

Worsaae

Rouse

2008

Journal of Morphology

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“…In its overall arrangement, the regularly spaced and highly concentrated array of diverse sensory cells at the front end of the planula is reminiscent of the sensory neuronal arrays of simple bilaterians (Raikova et al, 1998;Gaerber et al, 2007;Kotikova and Raikova, 2008;Schmidt-Rhaesa, 2009). Moreover, the ordered array of neural processes in this plexus has morphological features that are also found in the central neuropiles of bilaterian ganglia (Meinertzhagen, 2010).…”

Section: Evolutionary Considerationsmentioning

confidence: 98%

Complex neural architecture in the diploblastic larva of Clava multicornis (Hydrozoa, Cnidaria)

Piraino

Zega

Benedetto

et al. 2011

J of Comparative Neurology

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The organization of the cnidarian nervous system has been widely documented in polyps and medusae, but little is known about the nervous system of planula larvae, which give rise to adult forms after settling and metamorphosis. We describe histological and cytological features of the nervous system in planulae of the hydrozoan Clava multicornis. These planulae do not swim freely in the water column but rather crawl on the substrate by means of directional, coordinated ciliary movement coupled to lateral muscular bending movements associated with positive phototaxis. Histological analysis shows pronounced anteroposterior regionalization of the planula's nervous system, with different neural cell types highly concentrated at the anterior pole. Transmission electron microscopy of planulae shows the nervous system to be unusually complex, with a large, orderly array of sensory cells at the anterior pole. In the anterior half of the planula, the basiectodermal plexus of neurites forms an extensive orthogonal network, whereas more posteriorly neurites extend longitudinally along the body axis. Additional levels of nervous system complexity are uncovered by neuropeptide-specific immunocytochemistry, which reveals distinct neural subsets having specific molecular phenotypes. Together these observations imply that the nervous system of the planula of Clava multicornis manifests a remarkable level of histological, cytological, and functional organization, the features of which may be reminiscent of those present in early bilaterian animals.

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“…There are a few morphological features shared by acoels, Nemertodermatids and Xenoturbellids; for instance, the lack of a stomatogastric system and the presence of a pervasive peripheral plexus (Raikova et al, 1998, Raikova et al, 2000aRaikova et al, 2001;Reuter et al, 2001a;Reuter et al, 2001b). The structural characteristics of the nervous system in the different taxa allow us to infer correlations (trends) between their neuroanatomy and their relative taxonomic positions within the group.…”

Section: The Acoel Nervous System In Contextmentioning

confidence: 99%

The nervous system of Xenacoelomorpha: a genomic perspective

Perea-Atienza

Gavilán

Chiodin

et al. 2015

Journal of Experimental Biology

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Xenacoelomorpha is, most probably, a monophyletic group that includes three clades: Acoela, Nemertodermatida and Xenoturbellida. The group still has contentious phylogenetic affinities; though most authors place it as the sister group of the remaining bilaterians, some would include it as a fourth phylum within the Deuterostomia. Over the past few years, our group, along with others, has undertaken a systematic study of the microscopic anatomy of these worms; our main aim is to understand the structure and development of the nervous system. This research plan has been aided by the use of molecular/developmental tools, the most important of which has been the sequencing of the complete genomes and transcriptomes of different members of the three clades. The data obtained has been used to analyse the evolutionary history of gene families and to study their expression patterns during development, in both space and time. A major focus of our research is the origin of 'cephalized' (centralized) nervous systems. How complex brains are assembled from simpler neuronal arrays has been a matter of intense debate for at least 100 years. We are now tackling this issue using Xenacoelomorpha models. These represent an ideal system for this work because the members of the three clades have nervous systems with different degrees of cephalization; from the relatively simple sub-epithelial net of Xenoturbella to the compact brain of acoels. How this process of 'progressive' cephalization is reflected in the genomes or transcriptomes of these three groups of animals is the subject of this paper.

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A commissural brain! The pattern of 5-HT immunoreactivity in Acoela (Plathelminthes)

Cited by 72 publications

References 20 publications

Is Diurodrilus an annelid?

Is Diurodrilus an annelid?

Complex neural architecture in the diploblastic larva of Clava multicornis (Hydrozoa, Cnidaria)

The nervous system of Xenacoelomorpha: a genomic perspective

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