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ABSTRACT The ostreid genus Anomiostrea Habe & Kosuge, 1966, is monotypic for A. coralliophila Habe, 1975, which is known as a symbiont inhabiting the burrow of the ghost shrimp Neocallichirus jousseaumei (Nobili, 1904), but despite this unusual habit among oysters its phylogenetic position within the Ostreidae remained unknown. Using specimens collected from two distant localities of the Indo-Pacific, Oman and Japan, we compared shell morphology of these specimens with the holotype and assessed their phylogenetic relationships based on DNA sequence data from two mitochondrial and two nuclear genes. The genetic distance in cytochrome c oxidase subunit I between the specimens from Japan and Oman was 5.5%, indicating substantial geographic differentiation. Our molecular phylogenetic results suggest that A. coralliophila is sister to Ostrea algoensis G. B. Sowerby II, 1871, an oyster from rocky shores in South Africa, and both are closely related to other Ostrea species. This confirms assignment of Anomiostrea to Ostreinae and suggests that this burrow-wall symbiont evolved from typical rocky-shore oysters. Moreover, A. coralliophila was not monophyletic with another symbiotic ostreid Ostrea permollis G. B. Sowerby II, 1871, nor with other symbiotic oysters, indicating that the symbiotic habit evolved multiple times in the Ostreinae. 

The only revision of Iphione was made by Pettibone in 1986, who recognized four species including two newly described in that work: I. muricata (Savigny in Lamarck, 1818) (type species), I. ovata Kinberg, 1856, I. treadwelli Pettibone, 1986, and I. henshawi Pettibone, 1986. She included I. fimbriata de Quatrefages, 1866, I. glabra de Quatrefages, 1866, and I. fustis Hoagland, 1920 within I. muricata, and I. spinosa Kinberg, 1856 and I. hirotai Izuka, 1912 in I. ovata. Three other species were later added to the genus: I. reticulata Amoureux, Rullier & Fishelson, 1978 from the Red Sea, I. coriolis Hanley & Burke, 1991 from the Coral Sea, and I. malifera Piotrowski, 2014 from the Philippines. A recent contribution showed that I. ovata ranges from the Red Sea to the Eastern Pacific and includes I. spinosa and I. reticulata. Our objectives were to revise the genus, evaluating all species and describing new ones by assessing the relevance of morphological features, assisted in part with COI sequence data. We studied the morphology of type and non-type material from 18 institutions and sequenced 52 specimens representing 11 species. We found that the size and position of eyes, the size relationships between cephalic appendages, and the number of rows of macrotubercles in elytra vary with body size. The most relevant diagnostic features for species delineation, confirmed by genetic species delineation, are the type and size relationships of macrotubercles, the presence of fimbriae, the development of the basal tubercle of dorsal cirrophores, the type of neurochaetae (falcate versus acicular), and their tips (uni- vs bidentate; or simple vs hooded). We clarified the type species of the genus as I. ovata, and recognized 17 species, nine previously described and eight new. Our main results include: 1) the restriction of I. muricata; 2) the reinstatement of I. fimbriata including I. fustis; 3) redescriptions of I. coriolis, I. henshawi and I. treadwelli; and 4) the description of eight new species: I. ankeri sp. nov. from Guam, I. corbari sp. nov. from the Saya de Malha Bank, I. harrisae sp. nov. from French Polynesia, I. hourdezi sp. nov. from New Caledonia, I. hyndmani sp. nov. from Hong Kong, I. readi sp. nov. from the Red Sea (including many earlier records of I. muricata), I. richeri sp. nov. from New Caledonia, and I. wilsoni sp. nov. from Australia. Descriptions the eight newly described species include only one based upon a single specimen. Keys are included for the genera in the family, and species of Iphione.  

We document aggregations of an undescribed benthic solitary tunicate of the family Pyuridae from the Arabian Sea. This new genus was found forming dense thickets in shallow rocky substrates around Masirah Island and the Dhofar area in Oman. Such aggregations of tunicates have not been reported before from coral reefs in the Indo-West Pacific region and the Atlantic. This observation contributes to our understanding of the ecology and biogeography of ascidians, setting the stage for a comprehensive species description and in-depth analysis of this species. 

Molecular systematic studies of the anthozoan class Octocorallia have revealed widespread incongruence between phylogenetic relationships and taxonomic classification at all levels of the Linnean hierarchy. Among the soft coral taxa in order Malacalcyonacea, the family Alcyoniidae and its type genusAlcyoniumhave both been recognised to be highly polyphyletic. A recent family-level revision of Octocorallia established a number of new families for genera formerly considered to belong to Alcyoniidae, but revision ofAlcyoniumis not yet complete. Previous molecular studies have supported the placement ofAlcyonium verseveldti(Benayahu, 1982) in family Cladiellidae rather than Alcyoniidae, phylogenetically distinct from the other three genera in that family. Here we describe a new genus,Ofwegenumgen. nov.to accommodateO. verseveldticomb. nov.and three new species of that genus,O. coronalucissp. nov.,O. kloogisp. nov., andO. collisp. nov., bringing the total number of species in this genus to four.Ofwegenumgen. nov.is a rarely encountered genus so far known from only a few locations spanning the Indian and western Pacific Oceans. We present the morphological characters of each species and use molecular data from both DNA barcoding and target-enrichment of conserved elements to explore species boundaries and phylogenetic relationships within the genus. 

The only revision of Iphione was made by Pettibone in 1986, who recognized four species including two newly described in that work: I. muricata (Savigny in Lamarck, 1818) (type species), I. ovata Kinberg, 1856, I. treadwelli Pettibone, 1986, and I. henshawi Pettibone, 1986. She included I. fimbriata de Quatrefages, 1866, I. glabra de Quatrefages, 1866, and I. fustis Hoagland, 1920 within I. muricata, and I. spinosa Kinberg, 1856 and I. hirotai Izuka, 1912 in I. ovata. Three other species were later added to the genus: I. reticulata Amoureux, Rullier & Fishelson, 1978 from the Red Sea, I. coriolis Hanley & Burke, 1991 from the Coral Sea, and I. malifera Piotrowski, 2014 from the Philippines. A recent contribution showed that I. ovata ranges from the Red Sea to the Eastern Pacific and includes I. spinosa and I. reticulata. Our objectives were to revise the genus, evaluating all species and describing new ones by assessing the relevance of morphological features, assisted in part with COI sequence data. We studied the morphology of type and non-type material from 18 institutions and sequenced 52 specimens representing 11 species. We found that the size and position of eyes, the size relationships between cephalic appendages, and the number of rows of macrotubercles in elytra vary with body size. The most relevant diagnostic features for species delineation, confirmed by genetic species delineation, are the type and size relationships of macrotubercles, the presence of fimbriae, the development of the basal tubercle of dorsal cirrophores, the type of neurochaetae (falcate versus acicular), and their tips (uni- vs bidentate; or simple vs hooded). We clarified the type species of the genus as I. ovata, and recognized 17 species, nine previously described and eight new. Our main results include: 1) the restriction of I. muricata; 2) the reinstatement of I. fimbriata including I. fustis; 3) redescriptions of I. coriolis, I. henshawi and I. treadwelli; and 4) the description of eight new species: I. ankeri sp. n. from Guam, I. corbari sp. n. from the Saya de Malha Bank, I. harrisae sp. n. from French Polynesia, I. hourdezi sp. n. from New Caledonia, I. hyndmani sp. n. from Hong Kong, I. readi sp. n. from the Red Sea (including many earlier records of I. muricata), I. richeri sp. n. from New Caledonia, and I. wilsoni sp. n. from Australia. Descriptions the eight newly described species include only one based upon a single specimen. Keys are included for the genera in the family, and species of Iphione. 

Etisine crabs are some of the most abundant cryptobionts in Indo-West Pacific coral reef systems. Despite their ecological importance and abundance in museum collections, several recent systematic studies have indicated family- to subspecies-level taxonomic problems. One such case involves the former chlorodielline genus Soliella Lasley, Klaus & Ng, 2015 (treated here as part of Etisinae), which currently comprises two valid species and three available names that have been in flux in recent literature. The validity of these taxa has only been cursorily discussed. To resolve species limits and distributions, a thorough morphological examination of hundreds of specimens was conducted, including scanning electron microscopy of male gonopods, along with analysis of sequence data of the mitochondrial marker cytochrome c oxidase subunit I (COI) from 84 exemplars across the distribution of the genus. The status of two species that have Indian Ocean versus Pacific Ocean distributions with overlap in the Indo-Australian Archipelago and adjacent regions is confirmed. While external morphology is not reliable for identification, a few discrete, although slight, differences in gonopod morphology were found, and these results are consistent with a “pseudocryptic species” designation. Speciation conforms to a previously published etisine model of allopatric differentiation followed by subsequent divergence of gonopod morphology upon secondary sympatry. This pattern, the biogeography of the two species, and the term “pseudocryptic species” are discussed. 

The marine ribbon worm genusTetranemertesChernyshev, 1992 currently includes three species: the type speciesT. antonina(Quatrefages, 1846) from the Mediterranean Sea,T. rubrolineata(Kirsteuer, 1965) from Madagascar, andT. hermaphroditica(Gibson, 1982) from Australia. Seven new species are described:T. bifrostsp. nov.,T. ocelatasp. nov.,T. majinbuuisp. nov., andT. pastafariensissp. nov.from the Caribbean Sea (Panamá), and three species,T. unistriatasp. nov.,T. paulayisp. nov., andT. arabicasp. nov., from the Indo-West Pacific (Japan and Oman). As a result, an amended morphological diagnosis of the genus is offered. To improve nomenclatural stability, a neotype ofTetranemertes antoninais designated from the Mediterranean. The newly described species, each characterized by features of external appearance and stylet apparatus, as well as by DNA-barcodes, form a well-supported clade withT. antoninaon a molecular phylogeny of monostiliferan hoplonemerteans based on partial sequences of COI, 16S rRNA, 18S rRNA, and 28S rRNA. Six of the seven newly described species, as well asT. rubrolineata, possess the unusual character of having a central stylet basis slightly bilobed to deeply forked posteriorly in fully grown individuals, a possible morphological synapomorphy of the genus. In addition, an undescribed species ofTetranemertesis reported from the Eastern Tropical Pacific (Panamá), increasing the total number of known species in the genus to eleven. 

We document the benthic ctenophores Coeloplana sp. and Vallicula multiformis from Oman, extending their geographic range. A new Coeloplana species was found forming aggregations on gorgonians of two octocoral host genera, Melithaea and Euplexaura, representing associations previously unknown to occur in the Indo-West Pacific region. Our findings also illustrate the concurrent presence of the ectocommensal ophiuroid Ophiothela mirabilis, which adversely affects other Coeloplana species in the tropical West Atlantic, where it is considered invasive. This exploration contributes to our understanding of the biogeography, species distribution, and ectosymbiotic associations of these genera, setting the stage for a comprehensive species description and in-depth analysis of host relationships in future studies.