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Yeti crabs (Kiwaidae) are deep-sea hydrothermal vent and methane seep dwelling crustaceans that farm chemosynthetic microbes on their bodies. Sexual dimorphism is a common feature of decapod crustaceans, but little is known about its prevalence in species from deep-sea habitats. We address this knowledge deficit by investigating claw sexual dimorphism and symmetry in the hydrothermal-vent endemic ’Hoff crab’, Kiwa tyleri . A total of 135 specimens from the East Scotia Ridge were examined, revealing mean asymmetry indices close to zero with respect to propodus length and height, albeit with a significantly larger number of marginally left-dominant individuals with respect to propodus length, possibly indicative of some task specialisation between claws, or a vestigial ancestral trait. Both male and female claws exhibit positive allometry with increasing carapace length, but males possess significantly larger claws compared with females when accounting for carapace size, exhibiting faster growing propodus length, and broader propodus heights throughout the size distribution. This marked difference is indicative of either male-male competition for mate access, sexual selection, or differential energy allocation (growth vs reproduction) between males and females, as observed in other decapod crustaceans. In contrast, a reanalysis of data for the methane seep inhabiting yeti crab Kiwa puravida revealed no significant difference in claw allometry, indicating a possible lack of similar sexual selection pressures, and highlighting potential key differences in the ecological and reproductive strategies of K . tyleri and K . puravida relating to claw function, microbial productivity and population density. Whether sex differences in claw allometry represents the norm or the exception in Kiwaidae will require the examination of other species in the family. This research enhances our understanding of the behaviour, ecology and evolution of yeti crabs, providing a basis for future studies.

Chemosynthetic ecosystems have long been acknowledged as key areas of enrichment for deep-sea life, supporting hundreds of endemic species. Echinoderms are among the most common taxa inhabiting the periphery of chemosynthetic environments, and of these, chiridotid holothurians are often the most frequently observed. Yet, published records of chiridotids in these habitats are often noted only as supplemental information to larger ecological studies and several remain taxonomically unverified. This study therefore aimed to collate and review all known records attributed to Chiridota Eschscholtz, 1829 , and to conduct the first phylogenetic analysis into the relationship of these chiridotid holothurians across global chemosynthetic habitats. We show that Chiridota heheva Pawson & Vance, 2004 is a globally widespread, cosmopolitan holothurian that occupies all three types of deep-sea chemosynthetic ecosystem—hydrothermal vents, cold seeps and organic falls—as an organic-enrichment opportunist. Furthermore, we hypothesise that C. heheva may be synonymous with another vent-endemic chiridotid, Chiridota hydrothermica Smirnov et al., 2000 , owing to the strong morphological, ecological and biogeographical parallels between the two species, and predict that any chiridotid holothurians subsequently discovered at global reducing environments will belong to this novel species complex. This study highlights the importance of understudied, peripheral taxa, such as holothurians, to provide insights to biogeography, connectivity and speciation at insular deep-sea habitats.

In the austral summer of 2011 we undertook an investigation of three volcanic highs in the Central Bransfield Basin, Antarctica, in search of hydrothermal activity and associated fauna to assess changes since previous surveys and to evaluate the extent of hydrothermalism in this basin. At Hook Ridge, a submarine volcanic edifice at the eastern end of the basin, anomalies in water column redox potential (E(h)) were detected close to the seafloor, unaccompanied by temperature or turbidity anomalies, indicating low-temperature hydrothermal discharge. Seepage was manifested as shimmering water emanating from the sediment and from mineralised structures on the seafloor; recognisable vent endemic fauna were not observed. Pore fluids extracted from Hook Ridge sediment were depleted in chloride, sulfate and magnesium by up to 8% relative to seawater, enriched in lithium, boron and calcium, and had a distinct strontium isotope composition ((87)Sr/(86)Sr = 0.708776 at core base) compared with modern seawater ((87)Sr/(86)Sr ≈ 0.70918), indicating advection of hydrothermal fluid through sediment at this site. Biogeochemical zonation of redox active species implies significant moderation of the hydrothermal fluid with in situ diagenetic processes. At Middle Sister, the central ridge of the Three Sisters complex located about 100 km southwest of Hook Ridge, small water column E(h) anomalies were detected but visual observations of the seafloor and pore fluid profiles provided no evidence of active hydrothermal circulation. At The Axe, located about 50 km southwest of Three Sisters, no water column anomalies in E(h), temperature or turbidity were detected. These observations demonstrate that the temperature anomalies observed in previous surveys are episodic features, and suggest that hydrothermal circulation in the Bransfield Strait is ephemeral in nature and therefore may not support vent biota.

The Lucky Strike hydrothermal vent field, situated on the Mid-Atlantic Ridge (MAR), has been visited on a regular basis since 1992. The video imagery analyzed in this study originated from 10 cruises and was acquired either with the Nautile submersible or with the Remotely Operated Vehicle Victor 6000 between 1994 and 2008. Four faunal assemblages and two substratum types were identified on a large mussel-dominated sulfide edifice named “Eiffel Tower.” Their dynamics over 14 yr were investigated both at the scale of the entire edifice, between the edifice sides, and at small patch scales, making this the first high-time-resolution long-term variations study on the MAR. Overall percentage of biological colonization and overall mussel coverage were stable on a decadal scale. However, on shorter time scales as well as on smaller spatial scales, significant differences in microbial cover and in individual assemblage coverage and distribution were observed. The small fluctuations in the rather constant overall percentage of colonization (~ 50%) were explained by subtle changes in hydrothermal activity, which showed a significant negative correlation. However, not all variations occurring in the community structure could be explained by the hydrothermal activity, whereas the orientation of the edifice appeared to play an important role. We proposed a succession model for the shallower MAR fields, in addition to the first quantification of the rate of change in community dynamics at this slow-spreading ridge. This rate of change appeared to be about 15% slower than that observed on sulfide edifices from faster-spreading ridges in the Northeast Pacific.

Societal benefits of public engagement were recognized as 'impact' from research in the UK's recent Research Excellence Framework (REF), which determines an allocation of central government funding for universities and shapes the landscape for university researchers undertaking such activities. This paper shares experience from a successful REF Impact Case Study based on a programme of informing/inspiring-type public engagement, illustrating how engagement goals can match definitions of impact for the REF, and summarizing types of evidence used to demonstrate 'reach' and 'significance' of impact in media engagement, face-to-face engagement and online engagement, which represent common activities undertaken by many researchers.

Rimicaris hybisae sp. nov. is described from hydrothermal vent fields on the world's deepest seafloor spreading centre, the Mid-Cayman Spreading Centre (MCSC), Caribbean, at depths of 2300–4960 m. The new species is described and illustrated on the basis of 17 specimens. Brief notes on the distribution and habitat of the new species are provided. Molecular phylogenetic data from mitochondrial COI (460 base pair (bp)), 16S ribosomal RNA (549 bp) and nuclear 18S ribosomal RNA (576 bp) regions is used to complement the description. Morphological variation within R. hybisae sp. nov. and morphological affinities with previously described species are discussed. Based on morphological and molecular evidence, the new species is provisionally assigned to the genus Rimicaris, and differs from all known species in the genus by a distinctive pair of ‘pores' on the posterior lobes of its four-lobed dorsal organ. An emended diagnosis for Rimicaris is provided. Rimicaris hybisae sp. nov. is the first taxon to be described from MCSC vent fields. This record extends the known geographical range of Rimicaris into the Caribbean Sea and constitutes the deepest documented occurrence of alvinocaridid shrimp.

The functioning of terrestrial ecosystems seems to depend heavily on soil biodiversity. But what controls this diversity, and how will it fare in the global greenhouse? Jon Copley digs for some answers.

The United Nations Decade of Ocean Science for Sustainable Development presents an exceptional opportunity to effect positive change in ocean use. We outline what is required of the deep-sea research community to achieve these ambitious objectives.

A new species of the hippolytid shrimp genus Lebbeus White, 1847 is described from the Von Damm Vent Field (VDVF) on the Mid-Cayman Spreading Centre, Caribbean Sea, at 2294 m water depth. Lebbeus virentova sp. nov. is defined and illustrated from seven specimens, with brief notes on its distribution and habitat. Molecular phylogenetic data from the COI mDNA region are used to analyse the species’ phylogenetic position, and its morphology is compared with previously described species. This new species represents the second family of caridean shrimp to be reported from the VDVF. Lebbeus virentova sp. nov. is the eighth member of the genus to be described from hydrothermal vents and appears to be the first hippolytid shrimp at a vent field known from outside the Pacific Ocean.