One hundred years of Ceriantharia (Cnidaria): a mixed-methods review of research trends, biases, and knowledge gaps in tube-dwelling anemones

Abstract The subclass Ceriantharia comprises tube-dwelling anemones that play important roles in energy flow and the structural organization of marine benthic ecosystems. Although ceriantharians function as habitat-forming organisms and support diverse associated fauna, current knowledge of the group remains fragmented and uneven. We conducted a mixed-methods literature review integrating bibliometric and systematic approaches to synthesize research trends, thematic focus, and knowledge gaps across 89 peer-reviewed studies on Ceriantharia retrieved from the Web of Science Core Collection and Scopus, spanning publications from 1900 to 2024. Our principal research questions were: (1) how has research output on Ceriantharia changed over time; (2) what thematic, geographic, taxonomic, and methodological biases characterize the existing literature; and (3) what environmental information is currently available to characterize the environmental niche of Ceriantharia. Our results reveal pronounced temporal, geographic, taxonomic, and methodological biases. Early research was largely descriptive and taxonomically oriented, whereas recent decades have been characterized by a marked expansion of molecular and phylogenetic studies. Research effort is concentrated in a limited number of ocean basins and taxa, particularly within the family Cerianthidae, while several marine regions and lineages remain poorly investigated. We also identified substantial Wallacean and Grinnellian shortfalls: only 18% of studies reported geographic coordinates for specimen collection, and more than 56% failed to describe habitat characteristics or report environmental variables associated with the sampled organisms. Despite these limitations, the available literature provides a broad overview of the environmental conditions occupied by Ceriantharia, although this characterization remains strongly influenced by geographic and taxonomic sampling biases. We conclude that future progress will depend on expanding ecological investigations across underrepresented species and regions, improving the reporting of spatial and environmental data, and adopting integrative approaches that explicitly link taxonomy, molecular biology, ecology, and biogeography.