Gene expression profiles of dicyemid life-cycle stages may explain how dispersing larvae locate new hosts

Metazoans have evolved a great variety of life histories in response to environmental conditions. A unique example is encountered in dicyemid mesozoans. In addition to a highly simplified adult body comprising only ~ 30 cells, dicyemids exhibit a parasitic lifestyle that includes nematogens (asexual reproductive adults), rhombogens (sexual reproductive adults), vermiform larvae generated by nematogens, and infusoriform larvae generated by rhombogens. However, due to the difficulties of observing microscopic endoparasites, the complex life cycle and biological functions of life-cycle stages of dicyemids have remained mysterious. Taking advantage of the recently decoded genome of Dicyema japonicum, we examined genes that undergird this lifestyle. Using stage-specific gene expression profiles, we found that biological processes associated with molecular transport, developmental regulation, and sensory response are specified at different stages. Together with the expression of potential neurotransmitters, we further suggest that apical cells in infusoriform larva probably serve sensory functions, although dicyemids have no nervous system. Gene expression profiles show that more genes are expressed in free-living infusoriform larvae than in the other three stages, and that some of these genes are likely involved in locating new hosts. These data provide molecular information about the unique lifestyle of dicyemids and illustrate how an extremely simplified endoparasite adapted and retained gene sets and morphological characters to complete its life cycle. Supplementary information: Supplementary information accompanies this paper at 10.1186/s40851-019-0146-y

Dicyema Pax6 and Zic: tool-kit genes in a highly simplified bilaterian

<p>Abstract</p> <p>Background</p> <p>Dicyemid mesozoans (Phylum Dicyemida) are simple (8–40-cell) cephalopod endoparasites. They have neither body cavities nor differentiated organs, such as nervous and gastrointestinal systems. Whether dicyemids are intermediate between Protozoa and Metazoa (as represented by their "Mesozoa" classification) or degenerate species of more complex metazoans is controversial. Recent molecular phylogenetic studies suggested that they are simplified bilaterians belonging to the Lophotrochozoa. We cloned two genes developmentally critical in bilaterian animals (Pax6 and Zic), together with housekeeping genes (actin, fructose-bisphosphate aldolase, and ATP synthase beta subunit) from a dicyemid to reveal whether their molecular phylogeny supported the "simplification" hypothesis, and to clarify evolutionary changes in dicyemid gene structure and expression profiles.</p> <p>Results</p> <p>Genomic/cDNA sequence analysis showed that 1) the Pax6 molecular phylogeny and Zic intron positions supported the idea of dicyemids as reduced bilaterians; 2) the aa sequences deduced from the five genes were highly divergent; and 3) <it>Dicyema </it>genes contained very short introns of uniform length. In situ hybridization analyses revealed that <it>Zic </it>genes were expressed in hermaphroditic gonads, and <it>Pax6 </it>was expressed weakly throughout the developmental stages of the 2 types of embryo and in the hermaphroditic gonads.</p> <p>Conclusion</p> <p>The accelerated evolutionary rates and very short and uniform intron may represent a part of <it>Dicyema </it>genomic features. The presence and expression of the two tool-kit genes (<it>Pax6 </it>and <it>Zic</it>) in <it>Dicyema </it>suggests that they can be very versatile genes even required for the highly reduced bilaterian like <it>Dicyema</it>. Dicyemids may be useful models of evolutionary body plan simplification.</p

movement self-screening scores and pain

Background : Various musculoskeletal screening and functional performance tests are used to evaluate physical condition. However, validated analysis tools that can identify gaps in pain knowledge during athletes’ daily training are lacking. This study aimed to investigate the relationship between pain intensity in athletes during their daily training and the KOJI AWARENESS™ test in order to determine whether body dysfunction is related to pain among athletes. Methods : This cross-sectional study was conducted in a fitness center at the authors’ affiliated institution. Thirty-five athletes (17 women and 18 men) aged 20-40 years were selected for study participation. KOJI AWARENESS™ self-evaluated test scores and pain intensity during daily training, as assessed on the numerical rating scale (NRS), were recorded. Results : The KOJI AWARENESS™ score showed a strong negative correlation with the NRS score for pain intensity during daily training (r = −0.640, P < 0.001). There was a significant negative correlation between KOJI AWARENESS™ and NRS scores, even when body mass index, sex, and age were entered as control variables. Conclusions : KOJI AWARENESS™ was highly accurate in detecting pain in athletes during their training

Effectiveness of KOJI AWARENESS tool

Background : The KOJI AWARENESS™ screening test is a self-administered screening tool for assessment of mobility, stability, and strength. It provides corrective exercises corresponding to the individual’s answers to the KOJI AWARENESS™ test questions. However, there is no evidence of the effectiveness of corrective exercises in improving KOJI AWARENESS™ screening test scores and activity-related pain. Methods : Twenty- six healthy subjects (11 female and 15 male ; age 20–50 years) were selected for participation. In a controlled laboratory setting, subjects were administered the KOJI AWARENESS™ test and were provided with individualized exercise programs based on the results of this first test. KOJI AWARENESS™ results were checked on the first day immediately after the first exercise session, and then again after the two-week program. Pain intensity was also assessed during daily training using a numerical rating scale. Results : Compared to pre-intervention, KOJI AWARENESS™ scores were significantly higher immediately after the first corrective exercise session and after 2 weeks of intervention (p < 0.001). Moreover, pain intensity was significantly lower after 2 weeks of intervention (p < 0.001). Conclusions : Individualized KOJI AWARENESS™ corrective exercises were effective immediately on the first day and also after the two-week program in improving the KOJI AWARENESS™ score and reducing pain intensity during daily training

Dicyemid Mesozoans: A Unique Parasitic Lifestyle and a Reduced Genome

Dicyemids, previously called "mesozoans" (intermediates between unicellular protozoans and multicellular metazoans), are an enigmatic animal group. They have a highly simplified adult body, comprising only approximately 30 cells, and they have a unique parasitic lifestyle. Recently, dicyemids were shown to be spiralians, with affinities to the Platyhelminthes. In order to understand molecular mechanisms involved in evolution of this odd animal, we sequenced the genome of Dicyema japonicum and a reference transcriptome assembly using mixed-stage samples. The D. japonicum genome features a high proportion of repetitive sequences that account for 49% of the genome. The dicyemid genome is reduced to approximately 67.5 Mb with 5,012 protein-coding genes. Only four Hox genes exist in the genome, with no clustering. Gene distribution in KEGG pathways shows that D. japonicum has fewer genes in most pathways. Instead of eliminating entire critical metabolic pathways, parasitic lineages likely simplify pathways by eliminating pathway-specific genes, while genes with fundamental functions may be retained in multiple pathways. In principle, parasites can stand to lose genes that are unnecessary, in order to conserve energy. However, whether retained genes in incomplete pathways serve intermediate functions and how parasites overcome the physiological needs served by lost genes, remain to be investigated in future studies

The Magnitude of Global Marine Species Diversity

Background: The question of how many marine species exist is important because it provides a metric for how much we do and do not know about life in the oceans. We have compiled the first register of the marine species of the world and used this baseline to estimate how many more species, partitioned among all major eukaryotic groups, may be discovered. Results: There are ∼226,000 eukaryotic marine species described. More species were described in the past decade (∼20,000) than in any previous one. The number of authors describing new species has been increasing at a faster rate than the number of new species described in the past six decades. We report that there are ∼170,000 synonyms, that 58,000–72,000 species are collected but not yet described, and that 482,000–741,000 more species have yet to be sampled. Molecular methods may add tens of thousands of cryptic species. Thus, there may be 0.7–1.0 million marine species. Past rates of description of new species indicate there may be 0.5 ± 0.2 million marine species. On average 37% (median 31%) of species in over 100 recent field studies around the world might be new to science. Conclusions: Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century

Fig. 25 in Fourteen New Species of Dicyemids (Phylum: Dicyemida) from Seven Species of Decapodiformes (Mollusca: Cephalopoda) in the Kumano Sea, Japan

Fig. 25. Pseudicyema daioense sp. nov., drawn from syntype specimens on slide NSMT-Me-67: a, b, Nematogen, anterior region; c, rhombogen, anterior region; d, nematogen, entire; e, rhombogen, entire; f, g, vermiform embryo within axial cell, cilia omitted (f), optical section (g); h, infusorigen; i–k, infusoriform embryos, dorsal view (i: cilia omitted), ventral view (j: cilia omitted), sagittal section (k). Scale bars: 10 µm.Published as part of Furuya, Hidetaka & Moritaki, Takeya, 2022, Fourteen New Species of Dicyemids (Phylum: Dicyemida) from Seven Species of Decapodiformes (Mollusca: Cephalopoda) in the Kumano Sea, Japan, pp. 181-226 in Species Diversity 27 (1) on page 213, DOI: 10.12782/specdiv.27.181, http://zenodo.org/record/717517

Two New Species of the Genus Dicyema (Mesozoa) from Octopuses of Japan with Notes on D. misakiense and D. acuticephalum(Systematics and Taxonomy)

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