More Like this

1. Clownfish hosting anemones (Anthozoa, Actiniaria) of the Red Sea: new associations and distributions, historical misidentifications, and morphological variability

   https://doi.org/10.1186/s41200-021-00216-6  

   Bennett-Smith, Morgan F.; Majoris, John E.; Titus, Benjamin M.; Berumen, Michael L. (December 2021, Marine Biodiversity Records)

   Abstract Background The Red Sea contains thousands of kilometers of fringing reef systems inhabited by clownfish and sea anemones, yet there is no consensus regarding the diversity of host anemone species that inhabit this region. We sought to clarify a historical record and recent literature sources that disagree on the diversity of host anemone species in the Red Sea, which contains one endemic anemonefish, Amphiprion bicinctus Rüppell 1830. Results We conducted 73 surveys spanning ~ 1600 km of coastline from the northern Saudi Arabian Red Sea to the Gulf of Aden and encountered seven species of host anemones, six of which hosted A. bicinctus. We revise the list of symbionts for A. bicinctus to include Stichodactyla haddoni (Saville-Kent, 1893) and Stichodactyla mertensii Brandt, 1835 which were both observed in multiple regions. We describe Red Sea phenotypic variability in Heteractis crispa (Hemprich & Ehrenberg in Ehrenberg, 1834) and Heteractis aurora (Quoy & Gaimard, 1833), which may indicate that these species hybridize in this region. We did not encounter Stichodactyla gigantea (Forsskål, 1775), although the Red Sea is the type locality for this species. Further, a thorough review of peer-reviewed literature, occurrence records, and misidentified basis of record reports dating back to the early twentieth century indicate that it is unlikely that S. gigantea occurs in the Red Sea. Conclusions In sum, we present a new guide for the host anemones of the Red Sea, revise the host specificity of A. bicinctus, and question whether S. gigantea occurs in the central and western Indian Ocean. 

   more » « less
2. Modified meiosis in the tardigrade Hypsibius exemplaris maintains heterozygosity across the genome

   https://doi.org/10.1093/genetics/iyag167  

   Coke, Adriana N; Zhang, Siqin Aurora; Papell, Lillian D; Burch, Christina L; Goldstein, Bob (July 2026, GENETICS)

   Lenormand, T (Ed.)

   Abstract In asexual reproduction, meiosis must be bypassed or altered to maintain ploidy from mother to daughter without fertilization. Most of the ways meiosis can be modified to this end are expected to reduce heterozygosity within individuals; however, many asexual species are highly heterozygous. Asexual reproduction is especially common among species of microscopic, desiccation-tolerant animals such as rotifers, nematodes, and tardigrades, but the cellular and genetic mechanisms underlying asexual reproduction have not been definitively documented in any species of tardigrade. Here, we show that the asexual tardigrade Hypsibius exemplaris fails to complete the cell division of meiosis I, followed by a complete meiosis II-like division, and reproduction proceeds without detectable loss of heterozygosity. We used a combined cytological and genomic approach to characterize the mechanism of reproduction and pattern of allele inheritance in this species. Furthermore, we identified heterozygous variants in a subset of transcriptionally active genes consistent with loss of function in one allele, suggesting that maintained heterozygosity in this species allowed divergence between alleles over time. This work establishes the meiotic mechanism and inheritance pattern of reproduction in H. exemplaris, which provides a framework for interpreting genetic variation in this organism as a laboratory model. Additionally, our finding that meiosis is modified in H. exemplaris via a mechanism that maintains heterozygosity across the genome adds to a growing list of asexual animals that have evolved to reproduce clonally despite the expected long-term costs. 

   more » « less
3. Environmental and molecular regulation of asexual reproduction in the sea anemone Nematostella vectensis

   https://doi.org/10.1098/rsos.230152  

   Al-Shaer, Layla; Leach, Whitney; Baban, Noor; Yagodich, Mia; Gibson, Mathew C.; Layden, Michael J. (June 2023, Royal Society Open Science)

   Cnidarians exhibit incredible reproductive diversity, with most capable of sexual and asexual reproduction. Here, we investigate factors that influence asexual reproduction in the burrowing sea anemoneNematostella vectensis,which can propagate asexually by transverse fission of the body column. By altering culture conditions, we demonstrate that the presence of a burrowing substrate strongly promotes transverse fission. In addition, we show that animal size does not affect fission rates, and that the plane of fission is fixed along the oral–aboral axis of the polyp. Homeobox transcription factors and components of the TGFβ, Notch, and FGF signalling pathways are differentially expressed in polyps undergoing physal pinching suggesting they are important regulators of transverse fission. Gene ontology analyses further suggest that during transverse fission the cell cycle is suppressed, and that cell adhesion and patterning mechanisms are downregulated to promote separation of the body column. Finally, we demonstrate that the rate of asexual reproduction is sensitive to population density. Collectively, these experiments provide a foundation for mechanistic studies of asexual reproduction inNematostella,with implications for understanding the reproductive and regenerative biology of other cnidarian species. 

   more » « less
4. The eco‐evolutionary importance of reproductive system variation in the macroalgae: Freshwater reds as a case study

   https://doi.org/10.1111/jpy.13407  

   Krueger‐Hadfield, Stacy A; Shainker‐Connelly, Sarah J; Crowell, Roseanna M; Vis, Morgan L (February 2024, Journal of Phycology)

   Abstract The relative frequency of sexual versus asexual reproduction governs the distribution of genetic diversity within and among populations. Most studies on the consequences of reproductive variation focus on the mating system (i.e., selfing vs. outcrossing) of diploid‐dominant taxa (e.g., angiosperms), often ignoring asexual reproduction. Although reproductive systems are hypothesized to be correlated with life‐cycle types, variation in the relative rates of sexual and asexual reproduction remains poorly characterized across eukaryotes. This is particularly true among the three major lineages of macroalgae (green, brown, and red). The Rhodophyta are particularly interesting, as many taxa have complex haploid–diploid life cycles that influence genetic structure. Though most marine reds have separate sexes, we show that freshwater red macroalgae exhibit patterns of switching between monoicy and dioicy in sister taxa that rival those recently shown in brown macroalgae and in angiosperms. We advocate for the investigation of reproductive system evolution using freshwater reds, as this will expand the life‐cycle types for which these data exist, enabling comparative analyses broadly across eukaryotes. Unlike their marine cousins, species in the Batrachospermales have macroscopic gametophytes attached to filamentous, often microscopic sporophytes. While asexual reproduction through monospores may occur in all freshwater reds, the Compsopogonales are thought to be exclusively asexual. Understanding the evolutionary consequences of selfing and asexual reproduction will aid in our understanding of the evolutionary ecology of all algae and of eukaryotic evolution generally. 

   more » « less
5. Nemo knows: clownfishes differentiate cryptic host species across fine and broad geographic scales and reveal a potential adaptive radiation in the clownfish-hosting sea anemones

   https://doi.org/10.1101/2024.11.15.623784  

   Chiodo, Tommaso; De_Jode, Aurélien; Quattrini, Andrea; Gibson, Miranda K; Froehlich, Catheline_Y M; Huang, Danwei; Fujii, Takuma; Yanagi, Kensuke; Reimer, James D; Scott, Anna; et al (November 2024, bioRxiv)

   Abstract The symbiosis between clownfishes (or anemonefishes) and their host sea anemones ranks among the most recognizable animal interactions on the planet. Found on coral reef habitats across the Indian and Pacific Oceans, 28 recognized species of clownfishes adaptively radiated from a common ancestor to live obligately with only 10 nominal species of host sea anemones. Are the host sea anemones truly less diverse than clownfishes? Did the symbiosis with clownfishes trigger a reciprocal adaptive radiation in sea anemones, or minimally, a co-evolutionary response to the mutualism? To address these questions, we combined fine- and broad-scale biogeographic sampling with multiple independent genomic datasets for the bubble-tip sea anemone,Entacmaea quadricolor—the most common clownfish host anemone throughout the Indo-West Pacific. Fine-scale sampling and restriction site associated DNA sequencing (RADseq) throughout the Japanese Archipelago revealed three highly divergent cryptic species: two of which co-occur throughout the Ryukyu Islands and can be differentiated by the clownfish species they host. Remarkably, broader biogeographic sampling and bait-capture sequencing reveals that this pattern is not simply the result of local ecological processes unique to Japan, but part of a deeper evolutionary signal where some species ofE. quadricolorserve as host to the generalist clownfish speciesAmphiprion clarkiiand others serve as host to the specialist clownfishA. frenatus. In total, we delimit at least five cryptic species inE. quadricolorthat have diversified within the last five million years. The rapid diversification ofE. quadricolorcombined with functional ecological and phenotypic differentiation supports the hypothesis that this may represent an adaptive radiation in response to mutualism with clownfishes. Our data indicate that clownfishes are not merely settling in locally available hosts but recruiting to specialized host lineages with which they have co-evolved. These findings have important implications for understanding how the clownfish-sea anemone symbiosis has evolved and will shape future research agendas on this iconic model system. 

   more » « less