Complete mitochondrial genome and evolutionary analysis of Turritopsis dohrnii, the "immortal" jellyfish with a reversible life-cycle

Characterization and phylogenetic analysis of the complete mitochondrial genome of Cotylorhiza tuberculata assembled using next-generation sequencing

In this study, the complete mitochondrial genome (mitogenome) of Cotylorhiza tuberculata (Scyphozoa; Rhizostomeae; Cepheidae) was assembled by the next-generation sequencing data. The complete mitogenome spanned 16,590 bp and contained 14 protein-coding genes, two transfer RNA genes, and two ribosomal RNA genes. Total AT% content was 67.7%, comprising A 30.22%, C 16.16%, G 17.05%, and T 36.56%. The gene arrangement exhibited consistency with the known mitogenomes of other jellyfish species. Furthermore, the phylogenetic relationship of C. tuberculata was investigated based on analysis of the 13 common protein-coding genes. Results indicated a close relationship between C. tuberculata and both Cassiopea xamachana and Cassiopea andromeda. These findings provide a valuable reference for advancing understanding of the phylogenetic relationships, taxonomic classification, and phylogeography of jellyfish species.

Aging as a loss of morphostatic information: A developmental bioelectricity perspective

Maintaining order at the tissue level is crucial throughout the lifespan, as failure can lead to cancer and an accumulation of molecular and cellular disorders. Perhaps, the most consistent and pervasive result of these failures is aging, which is characterized by the progressive loss of function and decline in the ability to maintain anatomical homeostasis and reproduce. This leads to organ malfunction, diseases, and ultimately death. The traditional understanding of aging is that it is caused by the accumulation of molecular and cellular damage. In this article, we propose a complementary view of aging from the perspective of endogenous bioelectricity which has not yet been integrated into aging research. We propose a view of aging as a morphostasis defect, a loss of biophysical prepattern information, encoding anatomical setpoints used for dynamic tissue and organ homeostasis. We hypothesize that this is specifically driven by abrogation of the endogenous bioelectric signaling that normally harnesses individual cell behaviors toward the creation and upkeep of complex multicellular structures in vivo. Herein, we first describe bioelectricity as the physiological software of life, and then identify and discuss the links between bioelectricity and life extension strategies and age-related diseases. We develop a bridge between aging and regeneration via bioelectric signaling that suggests a research program for healthful longevity via morphoceuticals. Finally, we discuss the broader implications of the homologies between development, aging, cancer and regeneration and how morphoceuticals can be developed for aging.

The complete mitochondrial genome and phylogenetic analysis of hydrozoan jellyfish Eirene ceylonensis (Cnidaria, Hydrozoa, Eirenidae) in the coastal sea of Qinhuangdao, China

Eirene ceylonensis, a hydrozoan jellyfish species with a complex polymorphic life cycle, is widely distributed in the Chinese coastal sea. In this study, we conducted sequencing and analysis of the first complete mitochondrial genome of E. ceylonensis, obtained from the coastal sea of Qinhuangdao, China. The linear mitochondrial genome is 14,997 bp in length with the overall AT content being 72.8%, encoding 13 protein-coding genes (PCGs), two transfer RNA (tRNA) genes (tRNA-Met and tRNA-Trp) and two ribosomal RNA (rRNA) genes (rrnS and rrnL). Phylogenetic analysis of 13 PCGs suggests that the E. ceylonensis is closely related to Laomedea flexuosa. The availability of the complete mitochondrial genome of E. ceylonensis will be useful for studying the evolutionary relationships of hydrozoan jellyfish species.

Studying of Molecular Regulation of Developmental Processes of Lower Metazoans Exemplified by Cnidaria Using High-Throughput Sequencing

A unique set of features and characteristics of species of the Cnidaria phylum is the one reason that makes them a model for a various studies. The plasticity of a life cycle and the processes of cell differentiation and development of an integral multicellular organism associated with it are of a specific scientific interest. A new stage of development of molecular genetic methods, including methods for high-throughput genome, transcriptome, and epigenome sequencing, both at the level of the whole organism and at the level of individual cells, makes it possible to obtain a detailed picture of the development of these animals. This review examines some modern approaches and advances in the reconstruction of the processes of ontogenesis of cnidarians by studying the regulatory signal transduction pathways and their interactions.

Nontraditional systems in aging research: an update

Research on the evolutionary and mechanistic aspects of aging and longevity has a reductionist nature, as the majority of knowledge originates from experiments on a relatively small number of systems and species. Good examples are the studies on the cellular, molecular, and genetic attributes of aging (senescence) that are primarily based on a narrow group of somatic cells, especially fibroblasts. Research on aging and/or longevity at the organismal level is dominated, in turn, by experiments on Drosophila melanogaster, worms (Caenorhabditis elegans), yeast (Saccharomyces cerevisiae), and higher organisms such as mice and humans. Other systems of aging, though numerous, constitute the minority. In this review, we collected and discussed a plethora of up-to-date findings about studies of aging, longevity, and sometimes even immortality in several valuable but less frequently used systems, including bacteria (Caulobacter crescentus, Escherichia coli), invertebrates (Turritopsis dohrnii, Hydra sp., Arctica islandica), fishes (Nothobranchius sp., Greenland shark), reptiles (giant tortoise), mammals (blind mole rats, naked mole rats, bats, elephants, killer whale), and even 3D organoids, to prove that they offer biogerontologists as much as the more conventional tools. At the same time, the diversified knowledge gained owing to research on those species may help to reconsider aging from a broader perspective, which should translate into a better understanding of this tremendously complex and clearly system-specific phenomenon.

Neurovascular Inflammaging in Health and Disease

Aging is characterized by a chronic low-grade sterile inflammation dubbed as inflammaging, which in part originates from accumulating cellular debris. These, acting as danger signals with many intrinsic factors such as cytokines, are sensed by a network of pattern recognition receptors and other cognate receptors, leading to the activation of inflammasomes. Due to the inflammasome activity-dependent increase in the levels of pro-inflammatory interleukins (IL-1β, IL-18), inflammation is initiated, resulting in tissue injury in various organs, the brain and the spinal cord included. Similarly, in age-related diseases of the central nervous system (CNS), inflammasome activation is a prominent moment, in which cells of the neurovascular unit occupy a significant position. In this review, we discuss the inflammatory changes in normal aging and summarize the current knowledge on the role of inflammasomes and contributing mechanisms in common CNS diseases, namely Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis and stroke, all of which occur more frequently with aging.

Complete Mitochondrial Genomes of Two Toxin-Accumulated Nassariids (Neogastropoda: Nassariidae: Nassarius) and Their Implication for Phylogeny

The Indo-Pacific nassariids (genus Nassarius) possesses the highest diversity within the family Nassariidae. However, the previous shell or radula-based classification of Nassarius is quite confusing due to the homoplasy of certain morphological characteristics. The toxin accumulators Nassarius glans and Nassarius siquijorensis are widely distributed in the subtidal regions of the Indo-Pacific Ocean. In spite of their biological significance, the phylogenetic positions of N. glans and N. siquijorensis are still undetermined. In the present study, the complete mitochondrial genomes of N. glans and N. siquijorensis were sequenced. The present mitochondrial genomes were 15,296 and 15,337 bp in length, respectively, showing negative AT skews and positive GC skews as well as a bias of AT rich on the heavy strand. They contained 13 protein coding genes, 22 transfer RNA genes, two ribosomal RNA genes, and several noncoding regions, and their gene order was identical to most caenogastropods. Based on the nucleotide sequences combining 13 protein coding genes and two rRNA genes, a well-supported phylogeny of Nassarius was reconstructed, and several morphological synapomorphies were observed corresponding to the phylogenetic framework. In addition, the sister group relationship between N. variciferus and the remaining toxin-accumulated nassariids was determined, suggesting that the phylogeny might be related to their diet. The divergence time estimation analysis revealed a correlation between speciation events of nassariids and glacial cycles during the Pliocene-Pleistocene epoch.

Phenotypic Switching Resulting From Developmental Plasticity: Fixed or Reversible?

The prevalent view of developmental phenotypic switching holds that phenotype modifications occurring during critical windows of development are "irreversible" - that is, once produced by environmental perturbation, the consequent juvenile and/or adult phenotypes are indelibly modified. Certainly, many such changes appear to be non-reversible later in life. Yet, whether animals with switched phenotypes during early development are unable to return to a normal range of adult phenotypes, or whether they do not experience the specific environmental conditions necessary for them to switch back to the normal range of adult phenotypes, remains an open question. Moreover, developmental critical windows are typically brief, early periods punctuating a much longer period of overall development. This leaves open additional developmental time for reversal (correction) of a switched phenotype resulting from an adverse environment early in development. Such reversal could occur from right after the critical window "closes," all the way into adulthood. In fact, examples abound of the capacity to return to normal adult phenotypes following phenotypic changes enabled by earlier developmental plasticity. Such examples include cold tolerance in the fruit fly, developmental switching of mouth formation in a nematode, organization of the spinal cord of larval zebrafish, camouflage pigmentation formation in larval newts, respiratory chemosensitivity in frogs, temperature-metabolism relations in turtles, development of vascular smooth muscle and kidney tissue in mammals, hatching/birth weight in numerous vertebrates,. More extreme cases of actual reversal (not just correction) occur in invertebrates (e.g., hydrozoans, barnacles) that actually 'backtrack' along normal developmental trajectories from adults back to earlier developmental stages. While developmental phenotypic switching is often viewed as a permanent deviation from the normal range of developmental plans, the concept of developmental phenotypic switching should be expanded to include sufficient plasticity allowing subsequent correction resulting in the normal adult phenotype.

Of Mice, Whales, Jellyfish and Men: In Pursuit of Increased Longevity

The quest for increased human longevity has been a goal of mankind throughout recorded history. Recent molecular studies are now providing potentially useful insights into the aging process which may help to achieve at least some aspects of this quest. This chapter will summarize the main findings of these studies with a focus on long-lived mutant mice and worms, and the longest living natural species including Galapagos giant tortoises, bowhead whales, Greenland sharks, quahog clams and the immortal jellyfish.

Unitary Physiology

The common relationships among a great variety of biological phenomena seem enigmatic when considered solely at the level of the phenotype. The deep connections in physiology, for example, between the effects of maternal food restriction in utero and the subsequent incidence of metabolic syndrome in offspring, the effects of microgravity on cell polarity and reproduction in yeast, stress effects on jellyfish, and their endless longevity, or the relationship between nutrient abundance and the colonial form in slime molds, are not apparent by phenotypic observation. Yet all of these phenomena are ultimately determined by the Target of Rapamycin (TOR) gene and its associated signaling complexes. In the same manner, the unfolding of evolutionary physiology can be explained by a comparable application of the common principle of cell-cell signaling extending across complex developmental and phylogenetic traits. It is asserted that a critical set of physiologic and phenotypic adaptations emanated from a few crucial, ancestral receptor gene duplications that enabled the successful terrestrial transition of vertebrates from water to land. In combination, mTor and its cognate receptors and a few crucial genetic duplications provide a mechanistic common denominator across a diverse spectrum of biological responses. The proper understanding of their purpose yields a unified concept of physiology and its evolutionary development. © 2018 American Physiological Society. Compr Physiol 8:761-771, 2018.