Hemocytes/coelomocytes DNA content in five marine invertebrates: cell cycles and genome sizes

Coelomic fluid of asteroid echinoderms: Current knowledge and future perspectives on its utility for disease and mortality investigations

Coelomic fluid surrounds the internal organs of asteroid echinoderms (asteroids, otherwise known as sea stars or starfish) and plays an essential role in the immune system, as well as in the transport of respiratory gases, nutrients, waste products, and reproductive mediators. Due to its importance in physiology and accessibility for nonlethal diagnostic sampling, coelomic fluid of asteroids provides an excellent sample matrix for health evaluations and can be particularly useful in disease and mortality investigations. This is especially important in light of recent increases in the number of affected individuals and species, larger geographic scope, and increased observed frequency of sea star wasting events compared with historic accounts of wasting. This review summarizes the current knowledge about coelomocytes, the effector cell of the asteroid immune system; coelomic fluid electrolytes, osmolality, acid-base status and respiratory gases, and microbiota; and genomic, transcriptomic, and proteomic investigations of coelomic fluid. The utility of coelomic fluid analysis for assessing stressor responses, diseases, and mortality investigations is considered with knowledge gaps and future directions identified. This complex body fluid provides an exciting opportunity to increase our understanding of this unique and ecologically important group of animals.

Immunomodulatory Function of Polyvinylpyrrolidone (PVP)-Functionalized Gold Nanoparticles in Vibrio-Stimulated Sea Urchin Immune Cells

We investigated the role of the gold nanoparticles functionalized with polyvinylpyrrolidone (PVP–AuNPs) on the innate immune response against an acute infection caused by Vibrio anguillarum in an in vitro immunological nonmammalian next-generation model, the sea urchin Paracentrotus lividus. To profile the immunomodulatory function of PVP–AuNPs (0.1 μg mL⁻¹) in sea urchin immune cells stimulated by Vibrio (10 μg mL⁻¹) for 3 h, we focused on the baseline immunological state of the donor, and we analysed the topography, cellular metabolism, and expression of human cell surface antigens of the exposed cells, as well as the signalling leading the interaction between PVP–AuNPs and the Vibrio-stimulated cells. PVP–AuNPs are not able to silence the inflammatory signalling (TLR4/p38MAPK/NF-κB signalling) that involves the whole population of P. lividus immune cells exposed to Vibrio. However, our findings emphasise the ability of PVP–AuNPs to stimulate a subset of rare cells (defined here as Group 3) that express CD45 and CD14 antigens on their surface, which are known to be involved in immune cell maturation and macrophage activation in humans. Our evidence on how PVP–AuNPs may stimulate sea urchin immune cells represents an important starting point for planning new research work on the topic.

Characterization of Coelomic Fluid Cell Types in the Starfish Marthasterias glacialis Using a Flow Cytometry/Imaging Combined Approach

Coelomocytes is the generic name for a collection of cellular morphotypes, present in many coelomate animals, and highly variable among echinoderm classes. The roles attributed to the major types of these free circulating cells present in the coelomic fluid of echinoderms include immune response, phagocytic digestion and clotting. Our main aim in this study was to characterize coelomocytes found in the coelomic fluid of Marthasterias glacialis (class Asteroidea) by using a combination of flow cytometry (FC), imaging flow cytometry (IFC) and fluorescence plus transmission electron microscopy (TEM). Two coelomocyte populations (P1 and P2) identified through flow cytometry were subsequently studied in terms of abundance, morphology, ultrastructure, cell viability and cell cycle profiles. Ultrastructurally, P2 diploid cells were present as two main morphotypes, similar to phagocytes and vertebrate thrombocytes, whereas the smaller P1 cellular population was characterized by low mitotic activity, a relatively undifferentiated cytotype and a high nucleus/cytoplasm ratio. In the present study we could not rule out possible similarities between haploid P1 cells and stem-cell types in other animals. Additionally, we report the presence of two other morphotypes in P2 that could only be detected by fluorescence microscopy, as well as a morphotype revealed via combined microscopy/FC. This integrative experimental workflow combined cells physical separation with different microscopic image capture technologies, enabling us to better tackle the characterization of the heterogeneous composition of coelomocytes populations.

Production of WW males lacking the masculine Z chromosome and mining the Macrobrachium rosenbergii genome for sex-chromosomes

The cultivation of monosex populations is common in animal husbandry. However, preselecting the desired gender remains a major biotechnological and ethical challenge. To achieve an efficient biotechnology for all-female aquaculture in the economically important prawn (Macrobrachium rosenbergii), we achieved – for the first time – WW males using androgenic gland cells transplantation which caused full sex-reversal of WW females to functional males. Crossing the WW males with WW females yielded all-female progeny lacking the Z chromosome. We now have the ability to manipulate – by non-genomic means – all possible genotype combinations (ZZ, WZ and WW) to retain either male or female phenotypes and hence to produce monosex populations of either gender. This calls for a study of the genomic basis underlying this striking sexual plasticity, questioning the content of the W and Z chromosomes. Here, we report on the sequencing of a high-quality genome exhibiting distinguishable paternal and maternal sequences. This assembly covers ~ 87.5% of the genome and yielded a remarkable N50 value of ~ 20 × 10⁶ bp. Genomic sex markers were used to initiate the identification and validation of parts of the W and Z chromosomes for the first time in arthropods.

Genome survey sequencing of red swamp crayfish Procambarus clarkii

Red swamp crayfish, Procambarus clarkii, presently is an important aquatic commercial species in China. The crayfish is a hot area of research focus, and its genetic improvement is quite urgent for the crayfish aquaculture in China. However, the knowledge of its genomic landscape is limited. In this study, a survey of P. clarkii genome was investigated based on Illumina's Solexa sequencing platform. Meanwhile, its genome size was estimated using flow cytometry. Interestingly, the genome size estimated is about 8.50 Gb by flow cytometry and 1.86 Gb with genome survey sequencing. Based on the assembled genome sequences, total of 136,962 genes and 152,268 exons were predicted, and the predicted genes ranged from 150 to 12,807 bp in length. The survey sequences could help accelerate the progress of gene discovery involved in genetic diversity and evolutionary analysis, even though it could not successfully applied for estimation of P. clarkii genome size.

Caterpillars did not evolve from onychophorans by hybridogenesis

The evolution and loss of distinctive larval forms in animal life cycles have produced complex patterns of similarity and difference among life-history stages and major animal lineages. One example of this similarity is the morphological forms of Onychophora (velvet worms) and the caterpillar-like larvae of some insects. Williamson [(2009) Proc Natl Acad Sci USA 106:15786-15790] has made the astonishing and unfounded claim that the ancestors of the velvet worms directly gave rise to insect caterpillars via hybridization and that evidence of this ancient "larval transfer" could be found in comparisons among the genomes of extant onychophorans, insects with larvae, and insects without larvae. Williamson has made a series of predictions arising from his hypothesis and urged genomicists to test them. Here, we use data already in the literature to show these predictions to be false. Hybridogenesis between distantly related animals does not explain patterns of morphological and life-history evolution in general, and the genes and genomes of animals provide strong evidence against hybridization or larval transfer between a velvet worm and an insect in particular.