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Syllinae is the largest and the most diverse subfamily in Syllidae and usually a dominant group in many marine habitats, both in terms of numbers of species and individuals. However, the lack of morphological synapomorphies for many genera and the non-monophyly of most of these suggested by molecular studies, have stressed taxonomic and systematic problems within this subfamily. Although several studies have revised some genera in the Indo-Pacific area, important gaps of knowledge remain for this biogeographic region. Thus, in this study we undertook detailed morphological examination of Syllis and Megasyllis specimens from the Philippine Islands and provide a phylogenetic analysis of Indo-Pacific Syllinae in order to evaluate the position of newly described species. We provide line drawings, light microscopy observations and electron microscopy micrographs for eight species, including five new to science. Maximum likelihood and Bayesian inference analyses of four molecular markers (28S rRNA, 18S rRNA, 16S rRNA, cytochrome c oxidase subunit I) from 85 specimens are presented, showing the non-monophyletic status of Syllis and Megasyllis. Overall, our study increases the biodiversity of syllids in this poorly known Indo-Pacific area, highlighting the importance of examining both morphological and molecular data to expand our knowledge of the subfamily Syllinae and to further resolve the taxonomic issues that remain in this group. The following new taxa are described: Megasyllis kurui sp. nov. Moreno-Martínez, San Martín & Álvarez-Campos, Syllis ireneae sp. nov. Moreno-Martínez, San Martín & Álvarez-Campos, Syllis santii sp. nov. Moreno-Martínez, San Martín & Álvarez-Campos, Syllis tini sp. nov. Moreno-Martínez, Syllis walong sp. nov. Moreno-Martínez, San Martín & Álvarez-Campos. [ABSTRACT FROM AUTHOR]

Marine worms of the genus Odontosyllis (Syllidae, Annelida) are well known for spectacular bioluminescent courtship rituals. During the reproductive period, the benthic marine worms leave the ocean floor and swim to the surface to spawn, using bioluminescent light for mate attraction. The behavioural aspects of the courtship ritual have been extensively investigated but little is known about the origin and evolution of light production in Odontosyllis that may be a key factor shaping the natural history of the group. To investigate the speciation patterns and evolutionary history of Odontosyllis, we inferred phylogenies following a gene concatenation approach using both maximum likelihood and Bayesian inference with a multilocus molecular dataset including nuclear (18S rRNA) and mitochondrial markers (16S rRNA and cytochrome c oxidase subunit I) from 51 Odontosyllis specimens. We also used the resulting phylogenetic tree to perform an ancestral state reconstruction analysis to trace the origin of bioluminescence within the group. Our results reveal that the genus Odontosyllis as currently delineated is a paraphyletic group that needs to be taxonomically revised to reflect evolutionary relationships. Nevertheless, our analyses recover two supported clades with bioluminescent species and suggest that the most recent common ancestor of luminous syllids was not bioluminescent, providing evidence that bioluminescence has evolved independently twice in the group. We discuss possible scenarios for the origin and evolution of light production and the potential role of bioluminescence courtship as a driver of speciation. Our results shed light on the evolutionary history of luminous syllids and suggest that bioluminescence might represent a key factor shaping the evolution of these organisms. [ABSTRACT FROM AUTHOR]

Syllid annelids from the so-called 'ribbon clade' are flattened, ribbon-shaped worms of the genera Parahaplosyllis Hartmann-Schröder, 1990, Eurysyllis Ehlers, 1864, Xenosyllis Marion & Bobretzky, 1875, Trypanosyllis Claparède, 1864, Ramisyllis Glasby, Schroeder & Aguado, 2012, Trypanobia Imajima & Hartman, 1964, Plakosyllis Hartmann-Schröder, 1956, Pseudosyllis Grube, 1863 and Trypanedenta Imajima & Hartman, 1964. Some species possess a remarkable reproductive strategy using multiple stolons that has been recently suggested to be ancestral to the group. Here, to evaluate the evolution of reproductive modes in the group, we assess, for the first time, the phylogenetic relationships within the ribbon clade and related genera. We collected new material of Trypanobia and Trypanosyllis from Japan, Spain, Philippines and Indonesia and sequenced it for the nuclear markers 18S rRNA and the mitochondrial markers 16S rRNA and cytochrome c oxidase I for phylogenetic inference and also performed ancestral character reconstruction for the reproductive strategy in the entire group. Formal taxonomic descriptions of a new genus and six new species are provided. The new genus, Trypanospina, gen. nov., is characterised by the spines that cover its surface. Most genera within the 'ribbon clade' are monophyletic and the relationships appeared well supported in most cases. However, our phylogenetic hypotheses are not conclusive in regard to the relationships of the genera Trypanedenta and Trypanobia, nor to the status of those to genera as distinctive, since they seem to be paraphyletic and they appear in low-supported clades. In contrast, our results shed light on the evolution of the reproductive modes within the group, showing that scissiparity (development of a single stolon each time) is the ancestral character for the entire group and gemmiparity (development of more than one stolon at the same time) then appeared twice in two independent clades. [ABSTRACT FROM AUTHOR]