An understanding of ctenophore biology is critical for reconstructing events that occurred early in animal evolution. Toward this goal, we have sequenced, assembled, and annotated the genome of the ...ctenophore Mnemiopsis leidyi. Our phylogenomic analyses of both amino acid positions and gene content suggest that ctenophores rather than sponges are the sister lineage to all other animals. Mnemiopsis lacks many of the genes found in bilaterian mesodermal cell types, suggesting that these cell types evolved independently. The set of neural genes in Mnemiopsis is similar to that of sponges, indicating that sponges may have lost a nervous system. These results present a newly supported view of early animal evolution that accounts for major losses and/or gains of sophisticated cell types, including nerve and muscle cells.
The ctenophore Mnemiopsis leidyi A. Agassiz, 1865 originates from estuaries and coastal waters along Atlantic coastlines from the Chesapeake Bay, USA, to Argentina. Through ballast waters, the ...species has spread the past 30 years over Eurasia. On the French Mediterranean coastlines, Mnemiopsis leidyi was first formally identified in the Berre Lagoon in 2005 and has been episodically present in other Mediterranean lagoons as Bages-Sigean, Vaccarès, and Estomac. Since 2010–2011 no update of the distribution of Mnemiopsis leidyi has been made. Since 2019, many records of Mnemiopsis leidyi have been reported in other French Mediterranean lagoons along the coast of the Gulf of Lion. In this context, a field survey on the French Mediterranean coast was conducted in July 2020 to measure the expansion of the Mnemiopsis population in coastal lagoons which are potential refuge habitats for this species. Mnemiopsis leidyi was present in 8 different areas: Or, Pérols, Vic, Ingril, Rhône-Sète Channel, Bages-Sigean, and Salses-Leucate. We were able to quantify for the first time the abundance and size structure of Mnemiopsis in the lagoons of Or, Pérols, Vic, Ingril, Rhône-Sète Channel, and Salses-Leucate. A decrease in the abundance of Mnemiopsis leidyi was observed from 1 ind m−3 (Ingril Lagoon) to 28 ind m−3 (Grec Lagoon) and 42 ind m−3 (Rhône-Sète Channel) between the North and the South along the Rhône-Sète Channel in parallel to the increase of salinity (from 20 to 41). The abundances measured in Bages-Sigean and Salses-Leucate lagoons were similar: 6 ind m−3 and 7 ind m−3 respectively.
•Since 2019, many records of Mnemiopsis leidyi along the coast of the Gulf of Lion.•Field survey on the French Mediterranean coast was conducted in July 2020 to measure the expansion of the Mnemiopsis.•Mnemiopsis leidyi was present in 8 different areas: Or, Pérols, Vic, Ingril, Rhône-Sète Channel, Bages-Sigean, and Salses-Leucate.
The ability to isolate, monitor, and examine specific cells of interest enables targeted experimental manipulations that would otherwise be difficult to perform and interpret in the context of the ...whole organism. In vitro primary cell cultures derived from ctenophores thus serve as an important tool for understanding complex cellular and molecular interactions that take place both within and between various ctenophore cell types. Here we describe methods for reliably generating and maintaining primary cell cultures derived from the lobate ctenophore Mnemiopsis leidyi that can be used for a wide variety of experimental applications.
Scanning electron microscopy (SEM) is a powerful tool for ultrastructural analyses of biological specimens at their surface. With comb jellies being very soft and full of water, many methodological ...difficulties limit their microanatomical studies via SEM. Here, we describe SEM protocols and approaches successfully tested on ctenophores Pleurobrachia bachei and Beroe abyssicola. Our SEM investigation revealed the astonishing diversity of ciliated structures in all major functional systems, different receptor types, and complex muscular architecture. These protocols can also be practical for various basal bilaterian lineages such as cnidarians.
Brief History of Ctenophora Moroz, Leonid L
Methods in molecular biology (Clifton, N.J.),
2024, Volume:
2757
Journal Article
Ctenophores are the descendants of the earliest surviving lineage of ancestral metazoans, predating the branch leading to sponges (Ctenophore-first phylogeny). Emerging genomic, ultrastructural, ...cellular, and systemic data indicate that virtually every aspect of ctenophore biology as well as ctenophore development are remarkably different from what is described in representatives of other 32 animal phyla. The outcome of this reconstruction is that most system-level components associated with the ctenophore organization result from convergent evolution. In other words, the ctenophore lineage independently evolved as high animal complexities with the astonishing diversity of cell types and structures as bilaterians and cnidarians. Specifically, neurons, synapses, muscles, mesoderm, through gut, sensory, and integrative systems evolved independently in Ctenophora. Rapid parallel evolution of complex traits is associated with a broad spectrum of unique ctenophore-specific molecular innovations, including alternative toolkits for making an animal. However, the systematic studies of ctenophores are in their infancy, and deciphering their remarkable morphological and functional diversity is one of the hot topics in biological research, with many anticipated surprises.
Ctenophores are gelatinous marine animals famous for locomotion by ciliary combs. Due to the uncertainties of the phylogenetic placement of ctenophores and the absence of some key bilaterian neuronal ...genes, it has been hypothesized that their neurons evolved independently. Additionally, recent whole-body, single-cell RNA sequencing (scRNA-seq) analysis failed to identify ctenophore neurons using any of the known neuronal molecular markers. To reveal the molecular machinery of ctenophore neurons, we have characterized the neuropeptide repertoire of the ctenophore Mnemiopsis leidyi. Using the machine learning NeuroPID tool, we predicted 129 new putative neuropeptide precursors. Sixteen of them were localized to the subepithelial nerve net (SNN), sensory aboral organ (AO), and epithelial sensory cells (ESCs), providing evidence that they are neuropeptide precursors. Four of these putative neuropeptides had a behavioral effect and increased the animals’ swimming speed. Intriguingly, these putative neuropeptides finally allowed us to identify neuronal cell types in single-cell transcriptomic data and reveal the molecular identity of ctenophore neurons. High-resolution electron microscopy and 3D reconstructions of the nerve net underlying the comb plates confirmed a more than 100-year-old hypothesis of anastomoses between neurites of the same cell in ctenophores and revealed that they occur through a continuous membrane. Our work demonstrates the unique ultrastructure of the peptidergic nerve net and a rich neuropeptide repertoire of ctenophores, supporting the hypothesis that the first nervous system(s) evolved as nets of peptidergic cells.
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•Ctenophore neurons and sensory cells bear multiple unique neuropeptides•Several neuropeptides affect ctenophore swimming behavior•Peptidergic ctenophore neurons have long anastomosed neurites•Ctenophore neurons have both common and unique molecular and morphological features
Sachkova et al. reveal the neuropeptide repertoire; peculiar, anastomosed neurites; and the molecular machinery of ctenophore neurons. Multiple peptidergic neurons of the ctenophore Mnemiopsis leidyi support the hypothesis that the first nervous system(s) evolved as nets of peptidergic cells.
The genus
Mnemiopsis
is comprised of a single species,
Mnemiopsis leidyi
A. Agassiz, 1865, that has recently made the transition from a distribution limited to the Atlantic coasts of North and South ...America to an invasive range that includes the Black, Caspian, Mediterranean, North, and Baltic seas. We review the foundations of the ctenophore’s invasive success, which include the source-sink dynamics that characterize
Mnemiopsis
populations in temperate coastal waters where the ctenophore achieves its highest biomass levels and ecosystem impacts. Within its native temperate range,
Mnemiopsis
is frequently a dominant, seasonal, colonizing species with limited dispersal capacities. Cross-oceanic transport within ballast waters of intercontinental shipping vessels has altered this dispersal limitation and initiated a rapid global spread of
Mnemiopsis
. Owing to continuing transport via transoceanic shipping, we anticipate continued range expansion and review the variables most likely to determine whether introduction of
Mnemiopsis
to a novel community results in an inconspicuous addition or a disruptive invasion.
Ctenophores (commonly known as comb jellies) are among the earliest branching extant lineages of the animal kingdom. Here, I present a brief overview of the ctenophore nervous system, discussing its ...cellular architecture and molecular composition, as well as insights it offers into the early evolution of neurons and chemical neurotransmission.
Ctenophores or comb jellies are representatives of an enigmatic lineage of early branching metazoans with complex tissue and organ organization. Their biology and even microanatomy are not well known ...for most of these fragile pelagic and deep-water species. Here, we present immunohistochemical protocols successfully tested on more than a dozen ctenophores. This chapter also illustrates neural organization in several reference species of the phylum (Pleurobrachia bachei, P. pileus, Mnemiopsis leidyi, Bolinopsis microptera, Beroe ovata, and B. abyssicola) as well as numerous ciliated structures in different functional systems. The applications of these protocols illuminate a very complex diversification of cell types comparable to many bilaterian lineages.
Ctenophora: Illustrated Guide and Taxonomy Moroz, Leonid L; Collins, Richard; Paulay, Gustav
Methods in molecular biology (Clifton, N.J.),
2024, Volume:
2757
Journal Article
Ctenophores or comb jellies represent the first diverging lineage of extant animals - sister to all other Metazoa. As a result, they occupy a unique place in the biological sciences. Despite their ...importance, this diverse group of marine predators has remained relatively poorly known, with both the species and higher-level taxonomy of the phylum in need of attention. We present a checklist of the phylum based on a review of the current taxonomic literature and illustrate their diversity with images. The current classification presented remains substantially in conflict with recent phylogenetic results, and many of the taxa are not monophyletic or untested. This chapter summarizes the existing classification focusing on recognized families and genera with 185 currently accepted, extant species listed. We provide illustrative examples of ctenophore diversity covering all but one of the 33 families and 47 of the 48 genera, as well as about 25-30 undescribed species. We also list the 14 recognized ctenophore fossil species and note others that have been controversially attributed to the phylum. Analyses of unique ctenophore adaptations are critical to understanding early animal evolution and adaptive radiation of this clade of basal metazoans.
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