Dispersal and speciation: The cross Atlantic relationship of two parasitic cnidarians

TEMPERATURE AND SALINITY AFFECT DEVELOPMENT OF THE PARASITIC SEA ANEMONE EDWARDSIELLA LINEATA POTENTIALLY LIMITING ITS IMPACT AS A BIOLOGICAL CONTROL ON THE CTENOPHORE MNEMIOPSIS LEIDYI

The lined sea anemone, Edwardsiella lineata, parasitizes the ctenophore Mnemiopsis leidyi, which is one of the most destructive marine invasive species in the world. Mnemiopsis leidyi is known to tolerate a wide range of environmental conditions. However, the environmental tolerances of its most prominent parasite have never been characterized. Here we determined the effects of temperature (18, 22, 26, and 30 C) and salinity (6, 15, 24, and 33 ppt) on the survival and development of E. lineata from a vermiform parasite to a free-living polyp. At higher temperatures and lower salinities, E. lineata experienced significantly higher mortality, and it failed to develop into an adult polyp at the highest temperature (30 C) and lowest salinities we tested (6 ppt or 15 ppt). While such temperature and salinity restrictions would not currently prevent E. lineata from infecting M. leidyi in many of the European waters where it has become a destructive invasive species, these environmental limitations may be reducing overlap between host and parasite within the host's native range, a situation that could be exacerbated by climate change.

Gems of the southern Japanese seas - four new species of Edwardsianthus (Anthozoa, Actiniaria, Edwardsiidae) with redescriptions of two species

Edwardsianthus England, 1987 is a genus of Edwardsiidae, a family of burrowing and worm-like sea anemones characterized by lacking four mesenteries in the first cycle and containing only one type of nematocysts in nemathybomes. Until now, this genus has accommodated only two species since its establishment and has been recorded only from Indo-West Pacific regions. In this study, six species are reported from Japan: two are previously known species, E.pudicus (Klunzinger, 1877) and E.gilbertensis (Carlgren, 1931); four are new species, E.carbunculussp. nov., E.sapphirussp. nov., E.smaragdussp. nov., and E.amethystussp. nov. Based on these results, the diagnostic features of the genus are revised.

Evolutionary Analysis of Cystatins of Early-Emerging Metazoans Reveals a Novel Subtype in Parasitic Cnidarians

The evolutionary aspects of cystatins are greatly underexplored in early-emerging metazoans. Thus, we surveyed the gene organization, protein architecture, and phylogeny of cystatin homologues mined from 110 genomes and the transcriptomes of 58 basal metazoan species, encompassing free-living and parasite taxa of Porifera, Placozoa, Cnidaria (including Myxozoa), and Ctenophora. We found that the cystatin gene repertoire significantly differs among phyla, with stefins present in most of the investigated lineages but with type 2 cystatins missing in several basal metazoan groups. Similar to liver and intestinal flukes, myxozoan parasites possess atypical stefins with chimeric structure that combine motifs of classical stefins and type 2 cystatins. Other early metazoan taxa regardless of lifestyle have only the classical representation of cystatins and lack multi-domain ones. Our comprehensive phylogenetic analyses revealed that stefins and type 2 cystatins clustered into taxonomically defined clades with multiple independent paralogous groups, which probably arose due to gene duplications. The stefin clade split between the subclades of classical stefins and the atypical stefins of myxozoans and flukes. Atypical stefins represent key evolutionary innovations of the two parasite groups for which their origin might have been linked with ancestral gene chimerization, obligate parasitism, life cycle complexity, genome reduction, and host immunity.

Dynamic Evolution of the Cthrc1 Genes, a Newly Defined Collagen-Like Family

Collagen triple helix repeat containing protein 1 (Cthrc1) is a secreted glycoprotein reported to regulate collagen deposition and to be linked to the Transforming growth factor β/Bone morphogenetic protein and the Wnt/planar cell polarity pathways. It was first identified as being induced upon injury to rat arteries and was found to be highly expressed in multiple human cancer types. Here, we explore the phylogenetic and evolutionary trends of this metazoan gene family, previously studied only in vertebrates. We identify Cthrc1 orthologs in two distant cnidarian species, the sea anemone Nematostella vectensis and the hydrozoan Clytia hemisphaerica, both of which harbor multiple copies of this gene. We find that Cthrc1 clade-specific diversification occurred multiple times in cnidarians as well as in most metazoan clades where we detected this gene. Many other groups, such as arthropods and nematodes, have entirely lost this gene family. Most vertebrates display a single highly conserved gene, and we show that the sequence evolutionary rate of Cthrc1 drastically decreased within the gnathostome lineage. Interestingly, this reduction coincided with the origin of its conserved upstream neighboring gene, Frizzled 6 (FZD6), which in mice has been shown to functionally interact with Cthrc1. Structural modeling methods further reveal that the yet uncharacterized C-terminal domain of Cthrc1 is similar in structure to the globular C1q superfamily domain, also found in the C-termini of collagens VIII and X. Thus, our studies show that the Cthrc1 genes are a collagen-like family with a variable short collagen triple helix domain and a highly conserved C-terminal domain structure resembling the C1q family.