Greg W Rouse

University of California, San Diego | UCSD · Scripps Institution of Oceanography (SIO)

The discovery of four new Xenoturbella species from deep waters of the eastern Pacific Ocean is reported here. The genus and two nominal species were described from the west coast of Sweden1,2, but their taxonomic placement remains unstable3,4. Limited evidence placed Xenoturbella with molluscs5,6, but the tissues can be contaminated with prey7,8....

The exploration of Earth's biodiversity is an exciting and ongoing endeavour. Here, we report a new species of seadragon from Western Australia with substantial morphological and genetic differences to the only two other known species. We describe it as Phyllopteryx dewysea n. sp. Although the leafy seadragon (Phycodurus eques) and the common seadr...

Darwin [1] hypothesized that sexes in a species should be similar unless sexual selection, fecundity selection, or resource partitioning has driven them apart. Male dwarfism has evolved multiple times in a range of animals, raising questions about factors that drive such extreme size dimor-phism [2–4]. Ghiselin [5] noted that dwarf males are more c...

We describe a new genus, Osedax, and two new species of annelids with females that consume the bones of dead whales via ramifying roots. Molecular and morphological evidence revealed that Osedax belongs to the Siboglinidae, which includes pogonophoran and vestimentiferan worms from deep-sea vents, seeps, and anoxic basins. Osedax has skewed sex rat...

Within Polynoidae, a diverse aphroditiform family, the subfamily Macellicephalinae comprises anchialine cave-dwelling and deep-sea scaleworms. In this study, Lepidonotopodinae is synonymized with Macellicephalinae, and the tribe Lepidonotopodini is applied to a well-supported clade inhabiting deep-sea chemosynthetic-based ecosystems. Newly sequence...

Mineral-rich hardgrounds, such as ferromanganese (FeMn) crusts and phosphorites, occur on seamounts and continental margins, gaining attention for their resource potential due to their enrichment in valuable metals in some regions. This study focuses on the Southern California Borderland (SCB), an area characterized by uneven and heterogeneous topo...

The methane seeps on the Pacific margin of Costa Rica support extensive animal diversity and offer insights into deep-sea biogeography and phylogeography. During five expeditions between 2009 and 2019, we conducted intensive faunal sampling via 63 submersible dives to 11 localities at depths of 300-3600 m. Based on these expeditions and published l...

This study presents a comprehensive taxonomic revision of the family Suberitidae (Porifera: Demospongiae) for California, USA. We include the three species previously known from the region, document two additional species previously known from other regions, and formally describe four new species as Pseudosuberites latke sp. nov., Suberites califor...

Osedax is now known to be distributed around the world with more than 30 named and undescribed species. Here we report the discovery of four new species from two localities: Osedax bozoi n. sp. and Osedax craigmcclaini n. sp. from the Gulf of Mexico and Osedax estcourti n. sp. and Osedax traceyae n. sp. from off New Zealand. Osedax bozoi n. sp., Os...

Spirorbinae, a ubiquitous group of marine calcareous tubeworms with a small body size as adults, have a fascinating diversity of brooding modes that form the basis for their taxonomic division into six tribes (traditionally subfamilies): in-tube incubation, with varying degrees of attachment to adult structures (four tribes), and external incubatio...

Nereidid polychaetes are well known from shallow marine habitats, but their diversity in the deep sea is poorly known. Here we describe an unusual new nereidid species found at methane seeps off the Pacific coast of Costa Rica. Specimens of Pectinereis strickrotti gen. nov., sp. nov. had been observed dating back to 2009 swimming just above the sea...

We present the mitochondrial genome of the deep-sea, epibenthic, irregular echinoid Echinocrepis rostrata, representing the first sequenced mitogenome of the order Holasteroida. The length of the complete E. rostrata mitochondrial genome is 15,716 base pairs, and its GC content is 34.87%. It contains 13 protein-coding genes, two rRNA genes, and 22...

Pilargidae is a family of free-living and burrowing marine annelids. A lack of available molecular data for most of these species has precluded a molecular assessment of their phylogenetic relationships and has left uncertain the placement of Antonbruunia, which is hypothesized to be either a member of Pilargidae or its sister clade, the monotypic...

Endoparasitic annelids living inside another annelid host are known, particularly with regard to Oenonidae, but in general are poorly studied. The dorvilleid Veneriserva pygoclava is known from southern California, and its genus name (Latin = Venus's servant) alludes to the close association with the host aphroditid scaleworm Aphrodita longipalpa....

Xyloplax is a genus of three species of sea stars previously found only on sunken wood in the deep ocean. Their circular and petaloid bodies, which lend them their common name “sea daisy”, and their presumed exclusive diet of wood make them an unusual and rare element of deep-sea ecosystems. We describe here the fourth species of Xyloplax from the...

An increasing number of Antarctic invertebrate taxa have been revealed as cryptic species complexes following DNA-based assessments. This ultimately necessitates a morphological reassessment to find traits that will help identify these cryptic or pseudocryptic species without the need for sequencing every individual. This work concerns comatulid cr...

Sea cucumbers (Holothuroidea) are a diverse clade of echinoderms found from intertidal waters to the bottom of the deepest oceanic trenches. Their reduced skeletons and limited number of phylogenetically informative traits have long obfuscated morphological classifications. Sanger-sequenced molecular datasets have also failed to constrain the posit...

Siboglinid tubeworms are found at chemosynthetic environments worldwide and the Vestimentifera clade is particularly well known for their reliance on chemoautotrophic bacterial symbionts for nutrition. The mitochondrial genomes have been published for nine vestimentiferan species to date. This study provides new complete mitochondrial genomes for t...

First described in 2004 off California, Osedax worms are now known from many of the world's oceans, ranging from 10 to over 4000 m in depth. Currently, little is known about species ranges, since most descriptions are from single localities. In this study, we used new sampling in the north-eastern Pacific and available GenBank data from off Japan a...

Osedax, the deep-sea annelid found at sunken whalefalls, is known to host Oceanospirillales bacterial endosymbionts intracellularly in specialized roots, which help it feed exclusively on vertebrate bones. Past studies, however, have also made mention of external bacteria on their trunks. During a 14-yr study, we reveal a dynamic, yet persistent, s...

Background Common seadragons ( Phyllopteryx taeniolatus , Syngnathidae) are an emblem of the diverse endemic fauna of Australia’s southern rocky reefs, the newly recognized “Great Southern Reef.” A lack of assessments spanning this global biodiversity hotspot in its entirety is currently hampering an understanding of the factors that have contribut...

Bacterial symbioses allow annelids to colonise extreme ecological niches, such as hydrothermal vents and whale falls. Yet, the genetic principles sustaining these symbioses remain unclear. Here, we show that different genomic adaptations underpin the symbioses of phylogenetically related annelids with distinct nutritional strategies. Genome compact...

We deployed jaws of the common thresher shark ( Alopias vulpinus ) on the seafloor at ~1000 m depth off Monterey California for 8 months. The jaws disintegrated, with all the hyaline cartilage disappearing, leaving some fragments of tessellated cartilage and the teeth. Two different Osedax species, O. packardorum and O. talkovici were found to have...

Himerometroidea is a clade of chiefly shallow-water, tropical, feather-star crinoids that is currently divided, based on morphology, into four families comprising 119 extant species in 31 genera. Our molecular phylogenetic results, based on three mitochondrial (CO1, 16S, CytB) and two nuclear (ITS and 28S) markers for 55 accepted species in 23 of t...

Dorvilleids belonging to Ophryotrocha Claparède & Mecznikow, 1869 are known from deep-sea hydrothermal vents in the Pacific, Atlantic, Indian and Southern Oceans. However, how they colonized and diversified in these ecosystems has not been assessed in detail. Here, a collection of Pacific hydrothermal vent Ophryotrocha was examined using morphology...

Serpulidae Rafinesque, 1815 is a speciose group of polychaetes that all inhabit calcareous tubes. The family was traditionally subdivided into Serpulinae, Filograninae, and Spirorbinae. Recent phylogenetic analyses have suggested that both Filograninae and Serpulinae are paraphyletic, though with limited sampling. Here we report the first phylogene...

Munidopsid squat lobsters are among the most abundant decapods at abyssal depths and the most diverse squat lobster group in the East Pacific region. During recent cruises along the East Pacific, many deep-sea squat lobsters were collected. Among these, we described five new munidopsid species supported both by morphological characters and molecula...

Sea cucumbers (Holothuroidea) are a diverse clade of echinoderms found from intertidal waters to the bottom of the deepest trenches. Their reduced skeletons and limited number of phylogenetically-informative traits have long obfuscated morphological classifications. Sanger-sequenced molecular datasets have also failed to constrain the position of m...

Background Osedax, the deep-sea annelid found at sunken whalefalls, is known to host bacterial endosymbionts intracellularly in specialized roots, that help it feed exclusively on vertebrate bones. Past studies, however, have also made mention of external bacteria on their trunks. Here, we present an examination of the bacterial communities associa...

Osedax , the deep-sea annelid found at sunken whalefalls, is known to host Oceanospirillales bacterial endosymbionts intracellularly in specialized roots, that help it feed exclusively on vertebrate bones. Past studies, however, have also made mention of external bacteria on their trunks. During a 14-year study, we reveal a dynamic, yet persistent,...

The North Pacific bigeye octopus, Octopus californicus (Berry, 1911) is a cold‐water, deep‐sea octopod. Little is known about their biology due to difficulty accessing their natural habitat and obtaining live specimens. Although they are a frequent bycatch product in commercial bottom trawl fisheries, individuals of this species have rarely been ra...

The taxonomy of ribbon worms (Nemertea) is particularly challenging due to the sparsity of distinct morphological characters, causing a significant underestimation of the group's true diversity. The number of named deep-sea species is very limited and there is a vast number of undescribed deep-sea nemerteans still to be discovered. In this paper we...

Annelids have repeatedly evolved symbioses that allow them to colonise extreme ecological niches, like hydrothermal vents and whale falls. Yet, the genetic principles sustaining these symbiotic lifestyles remain unclear. Here we show that different genomic adaptations underpin the symbioses of phylogenetically related annelids with distinct nutriti...

The marine annelid Osedax has evolved a unique heterotrophic symbiosis that allows it to feed exclusively on sunken bones. Yet, the genetic and physiological principles sustaining this symbiosis are poorly understood. Here we show that Osedax frankpressi has a small, AT-rich genome shaped by extensive gene loss. While the Oceanospirillales endosymb...

Here, we present the first mitochondrial genome of Eiconaxius baja. The mitogenome contains 13 protein-coding genes (PCGs), two rRNA genes, and 22 tRNA genes. The total length of the complete E. baja mitochondrial genome is 16,212 base pairs, and the GC content is 26.82%. The gene order is consistent with that of Eiconaxius serratus, and most other...

Continental margins host methane seeps, animal falls and wood falls, with chemosynthetic communities that may share or exchange species. The goal of this study was to examine the existence and nature of linkages among chemosynthesis-based ecosystems by deploying organic fall mimics (bone and wood) alongside defaunated carbonate rocks within high an...

Specimens of a new species of torquaratorid acorn worm (Hemichordata, Enteropneusta) were video recorded and subsequently collected at abyssal depths in the eastern North Pacific at sites ranging from Oregon to northern Mexico. These worms are described here as Yoda demiankoopi n. sp. by molecular and morphological methods. The new species differs...

The Antarctic marine environment, although rich in life, is predicted to experience rapid and significant effects from climate change. Despite a revolution in the approaches used to document biodiversity, less than one percent of Antarctic marine invertebrates are represented by DNA barcodes and we are at risk of losing biodiversity before discover...

Galapagomystides is an exclusively deep-sea group of Phyllodocidae, originally erected for Galapagomystides aristata from hydrothermal vents of the Galapagos Rift. In this study, Phyllodocidae collected from hydrothermal vents and methane seeps from the Pacific Ocean, including specimens from vents of the East Pacific Rise identified as Galapagomys...

Background Seahorses, seadragons, pygmy pipehorses, and pipefishes (Syngnathidae, Syngnathiformes) are among the most recognizable groups of fishes because of their derived morphology, unusual life history, and worldwide distribution. Despite previous phylogenetic studies and recent new species descriptions of syngnathids, the evolutionary relation...

Echinoids are key components of modern marine ecosystems. Despite a remarkable fossil record, the emergence of their crown group is documented by few specimens of unclear affinities, rendering their early history uncertain. The origin of sand dollars, one of its most distinctive clades, is also unclear due to an unstable phylogenetic context. We em...

Oenonidae are an unusual group of annelids in that many of them are parasitic or have a parasitic phase in their life, often in other polychaetes. Most Oenonidae adults are medium- to large-sized annelids, ranging from 1 to 90 cm long with over 1000 segments (Paxton, 2000a) but usually thin. Externally many of them resemble Lumbrineridae , from whi...

Lumbrineridae adults are medium sized to large annelids, ranging from a few centimetres to over half a metre in length and several hundred segments (Pl. 6a).

Pilargidae is part of Phyllodocida , with adult sizes of the animals usually one to a few centimetres long but having up to several hundred segments. Many live Pilargidae lack specific pigmentation patterns and are of a whitish colour, although the posterior half of some (e.g. Pilargis ) is reddish with darker spots.

Acoetidae are large annelids with many segments and are unusual among scale-worms in being tubiculous (Fig. 8.1a).

Nephtyidae have a well-deserved difficult reputation among workers involved in benthic monitoring who try to identify them. They can be very abundant in shallow water sediments and there are often several different nephtyids in the same sample.

Named for their strange anatomy, Aberranta is a small, rare, and morphologically homogenous and characteristic group of free-living annelids, with adult length up to near 7 mm for about 40 chaetigers.

Fauveliopsidae is a small group of only around 30 species, best known for some Fauveliopsis taxa living in the empty shells of gastropods or scaphopods.

The first members of Annelida were named by Linnaeus (1758) and in the intervening period there have been thousands of others added. We estimate that the current number of accepted species level taxa is just under 21,000, though several thousand more have been named and are considered invalid. This is based on a count of the estimates presented in...

Hesionidae is named after the mythical Hesione, princess of Troy, who was rescued from a sea monster by Hercules. This group of beautiful worms are not uncommon in the sublittoral, especially on rocky and mixed bottoms, and they also seem to thrive in deep-sea environments with many species described from hydrothermal vents (Fig. 15.2c), whalefalls...

Ampharetidae are tubicolous, as are most members of Terebelliformia , and share with Alvinellidae and Melinnidae the feature that their multiple grooved palps, usually called tentacles, can be retracted into the mouth. Typically, Ampharetidae are 10 to 60 mm long, though some adults are only a few millimetres long.

The name Chrysopetalidae , from the Latin for ‘golden petals’, refers to the shape and the colour of the shiny, flattened notochaetae which cover the dorsum in one of the three major clades in the group, Chrysopetalinae (Pl. 3c).

Alvinellidae (‘Pompeii worms’ or ‘palm worms’), are a relatively recently discovered group known only from sites associated with deep-sea hydrothermal vents in the Pacific and Indian Oceans.

Aeolosomatidae is a group of minute worms living almost exclusively in freshwater habitats.

Melinnidae (Pl. 12c, d) is a small taxon of tubicolous Terebelliformia , containing only around 50 accepted species that are generally found in deeper waters. The group’s name is seemingly derived from an ancient Greek women’s name, Melinna, and this was the first genus name for the group (Read and Fauchald, 2021).

Trichobranchidae have multiple grooved palps (‘tentacles’), often of two kinds, and resemble their close relatives Terebellidae in several ways, though Melinnidae is actually closer to Terebellidae. Historically, they have often been included within the latter taxon.

Sphaerodoridae is a relatively small annelid group, with around 138 nominal species. The animals can be easily recognized by the conspicuous spherical macro- and microtubercles that give sphaerodorids their name (Figs. 19.1b, c).

Polynoidae is the largest group of Aphroditiformia , and one of the more species-rich of annelid clades covered in a chapter here. The body is dorso-ventrally flattened and often has an oval shape, but some can be long and slender (e.g. Polynoe scolopendrina ; Pl. 2e).

Members of Sabellidae (feather-duster worms) are among the most easily recognizable of annelid groups due to their possession of an often spectacularly colourful radiolar crown and by the mucus/ parchment/ sediment tubes that they generally inhabit (Pl. 8a–d).

Eunicidae is a well-known group of annelids, mainly for being one of the few groups that are regularly eaten by humans. Their exposed complex and intimidating jaws can often be observed in some giant Eunicidae waiting for their prey in Indonesia. This has resulted in the common name ‘sand striker worms’ for these majestic, avid predators.

The multiple grooved palps (‘tentacles’) of Terebellidae gives rise to their common name, spaghetti worms. These tentacles are a common sight extending out over the substrate in shallow marine waters worldwide. When disturbed the tentacles, often brightly coloured, can be seen coiling and looping as they are retracted back towards the worm.

Amphinomida includes two major groups: Amphinomidae and Euphrosinidae . Amphinomidae occur mainly in littoral warm waters. Some are called fireworms and are known for their brittle chaetae that easily break when touched and produce a burning sensation.

Capitellidae are commonly found, and it is a bit surprising there is no common name for the group. They are easily recognized, for the most part, by the division of the body into an anterior region with capillary chaetae only and a posterior region with long-handled hooks.

Members of Sternaspidae (from the Greek words for breast and shield) are instantly recognizable in their remarkable yellow, reddish, violet, or even black shield that lies ventro-posteriorly, and the posterior veil of branchiae.

Acrocirridae is a small taxonomic group comprising around 40 accepted species that are generally found in intertidal or shallow coarse sediments and muds. They often will also be found attached to the undersurface of stones or rubble. Some extraordinary holopelagic members of Acrocirridae ( Swima and Teuthidodrilus ) have also been described in rec...

Heterospio is a small group with only nine named species and no common name. Usually placed under the redundant names Longosomatidae or Heterospionidae , the systematic position of Heterospio is uncertain, though a relationship with Cirratulida is now apparent.

Chaetopteridae is a clade with small membership of around 75 valid species and nearly all are tubicolous. The taxon name is derived from the Greek for ‘chaetae’ and ‘wing’ and refers to the long aliform notopodia with aciculae in some taxa.

Paraonidae (no common name, but jesting students often call them ‘paranoids’) is a relatively small group in taxonomic terms and, because they tend to be found in deeper waters, there is little known about them.

Flabelligeridae, with a common name of bristle-cage worms, are generally recognizable by their papillose body, often coated with thick covering of sediment and the fact that the head is retractable between anterior segments which may project forward a ‘cage’ of chaetae (Pl. 14b–d).

Apistobranchus has small membership and has had a long period of uncertain affinity, though it is now apparent it is part of Chaetopteriformia .

Opheliidae are commonly found in sandy or muddy substrates from intertidal regions down to more than 7000 m. They are often noticed when disturbed by rapidly swimming in an energetic way and some

Lobatocerebrum is a small, exclusively meiofaunal clade with only three known species. The placement of these enigmatic animals has long been problematic, but recent molecular work establishes their placement within Annelida . The animals have an unsegmented, slender, and elongate body with a length of 1–3 mm.

Sabellariidae (known as honeycomb worms or sandcastle worms) build distinctive hard tubes from glued sand or other coarse particles and are commonly seen forming colonies on rocky surfaces in intertidal marine environments (Pl. 9a).

Dinophilus was erected by Schmidt (1848) and the name refers to the whirling motion these worms can show owing to their ciliary movement. Dinophilidae are all small, at less than 3 mm long as adults, and lack chaetae and obvious segmentation.

Syllidae constitutes a large and variable, but nevertheless highly characteristic group of polychaetes. The name comes from Syllis , a nymph in Greek mythology, who was the lover of the god Apollo and the mother of king Zeuxippos of Sikyon.

Serpulidae (fanworms), like Sabellidae , are very well-known owing to their colourful radiolar crown (Pl. 8e–g). Serpulidae are usually easily distinguished from Fabriciidae and Sabellidae in that they live in a calcareous tube, though this is sometimes embedded in coral.