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Evaluating the diversity of crinoids (Echinodermata: Crinoidea) in Singapore accurately has been challenging due in part to inadequacies in crinoid taxonomy. Most species descriptions have neither incorporated morphological variation of juveniles into diagnostic characters nor analysed species' molecular phylogenetic affinities. In this study, we performed detailed morphological examination and phylogenetic analyses of the mitochondrial cytochrome c oxidase subunit I marker on Himerometroidea crinoids collected from the Singapore Strait, and showed that specimens could not be reliably identified to species based on existing taxonomic descriptions. Specifically, juveniles identified as Heterometra spp. and Zygometra sp., and adults as H. cf. producta, solely based on morphological features were revealed to comprise three distinct species: Zygometra cf. comata, Heterometra schlegelii, and Dichrometra sp. The juveniles were found to have sizes smaller than the ranges given in existing descriptions, with considerable variabilities in traits that limited the utility of morphology for species taxonomy. Features contributing to misidentification of specimens and their application in past species diagnoses are discussed. Revised descriptions of these species, as well as the recently revised Homalometra crenulata, are also presented. More broadly, this study emphasises the need to revisit diagnoses of crinoid species according to various ontogenetic stages and to uncover more congruent morphological characters based on a robust molecular phylogeny. [ABSTRACT FROM AUTHOR]

Despite the ecological and economic significance of stony corals (Scleractinia), a robust understanding of their phylogeny remains elusive due to patchy taxonomic and genetic sampling, as well as the limited availability of informative markers. To increase the number of genetic loci available for phylogenomic analyses in Scleractinia, we designed 15,919 DNA enrichment baits targeting 605 orthogroups (mean 565 ± SD 366 bp) over 1,139 exon regions. A further 236 and 62 barcoding baits were designed for COI and histone H3 genes respectively for quality and contamination checks. Hybrid capture using these baits was performed on 18 coral species spanning the presently understood scleractinian phylogeny, with two corallimorpharians as outgroup. On average, 74% of all loci targeted were successfully captured for each species. Barcoding baits were matched unambiguously to their respective samples and revealed low levels of cross‐contamination in accordance with expectation. We put the data through a series of stringent filtering steps to ensure only scleractinian and phylogenetically informative loci were retained, and the final probe set comprised 13,479 baits, targeting 452 loci (mean 531 ± SD 307 bp) across 865 exon regions. Maximum likelihood, Bayesian and species tree analyses recovered maximally supported, topologically congruent trees consistent with previous phylogenomic reconstructions. The phylogenomic method presented here allows for consistent capture of orthologous loci among divergent coral taxa, facilitating the pooling of data from different studies and increasing the phylogenetic sampling of scleractinians in the future. [ABSTRACT FROM AUTHOR]

Sargassum is a cosmopolitan brown algal genus spanning the three ocean basins of the Atlantic, Pacific and Indian Oceans, inhabiting temperate, subtropical and tropical habitats. Sargassum has been postulated to have originated in the Oligocene epoch approximately 30 mya according to a broad phylogenetic analysis of brown macroalgae, but its diversification to become one of the most widespread and speciose macroalgal genera remains unclear. Here, we present a Bayesian molecular clock study, which analyzed data from the order Fucales of the brown algal crown radiation (BACR) group to reconstruct a time‐calibrated phylogeny of the Sargassum clade. Our phylogeny included a total of 120 taxa with 99 Sargassum species sampled for three molecular markers – ITS‐2, cox3 and rbcLS – calibrated with an unambiguous Sargassaceae fossil from between the lower and middle Miocene. The analysis revealed a much later origin of Sargassum than expected at about 6.7 mya, with the genus diversifying since approximately 4.3 mya. Current geographic distributions of Sargassum species were then analyzed in conjunction with the time‐calibrated phylogeny using the dispersal‐extinction‐cladogenesis (DEC) model to estimate ancestral ranges of clades in the genus. Results strongly support origination of Sargassum in the Central Indo‐Pacific (CIP) region with subsequent independent dispersal events into other marine realms. The longer history of diversification in the ancestral CIP range could explain the much greater diversity there relative to other marine areas today. Analyses of these dynamic processes, when fine‐tuned to a higher spatial resolution, enable the identification of evolutionary hotspots and provide insights into long‐term dispersal patterns. [ABSTRACT FROM AUTHOR]

Waminoa spp. are acoel flatworms mainly found as ectosymbionts on scleractinian corals. Although Waminoa could potentially represent a threat to their hosts, not enough information is available yet regarding their ecology and effect on the coral. Here, the Waminoa sp.–coral association was analyzed in Singapore reefs to determine the prevalence, host range, and preference, as well as the flatworm abundance on the coral surface. Moreover, the impact of Waminoa sp. on the expression of putative immune- and stress-response genes (C-type lectin, C3, Hsp70 and Actin) was examined in the coral Lobophyllia radians. The association prevalence was high (10.4%), especially in sites with lower sedimentation and turbidity. Waminoa sp. showed a wide host range, being found on 17 coral genera, many of which are new association records. However, only few coral genera, mostly characterized by massive or laminar morphologies appeared to be preferred hosts. Waminoa sp. individuals displayed variable patterns of coral surface coverage and an unequal distribution among different host taxa, possibly related to the different coral growth forms. A down-regulation of the expression of all the analyzed genes was recorded in L. radians portions colonized by Waminoa individuals compared to those without. This indicated that Waminoa sp. could affect components of the immune system and the cellular homeostasis of the coral, also inhibiting its growth. Therefore, Waminoa sp. could represent a potential further threat for coral communities already subjected to multiple stressors. [ABSTRACT FROM AUTHOR]