Tammy Horton

Does Presence of a Mid-Ocean Ridge Enhance Biomass and Biodiversity?

In contrast to generally sparse biological communities in open-ocean settings, seamounts and ridges are perceived as areas of elevated productivity and biodiversity capable of supporting commercial fisheries. We investigated the origin of this apparent biological enhancement over a segment of the North Mid-Atlantic Ridge (MAR) using sonar, corers, trawls, traps, and a remotely operated vehicle to survey habitat, biomass, and biodiversity. Satellite remote sensing provided information on flow patterns, thermal fronts, and primary production, while sediment traps measured export flux during 2007–2010. The MAR, 3,704,404 km2 in area, accounts for 44.7% lower bathyal habitat (800–3500 m depth) in the North Atlantic and is dominated by fine soft sediment substrate (95% of area) on a series of flat terraces with intervening slopes either side of the ridge axis contributing to habitat heterogeneity. The MAR fauna comprises mainly species known from continental margins with no evidence of greater biodiversity. Primary production and export flux over the MAR were not enhanced compared with a nearby reference station over the Porcupine Abyssal Plain. Biomasses of benthic macrofauna and megafauna were similar to global averages at the same depths totalling an estimated 258.9 kt C over the entire lower bathyal north MAR. A hypothetical flat plain at 3500 m depth in place of the MAR would contain 85.6 kt C, implying an increase of 173.3 kt C attributable to the presence of the Ridge. This is approximately equal to 167 kt C of estimated pelagic biomass displaced by the volume of the MAR. There is no enhancement of biological productivity over the MAR; oceanic bathypelagic species are replaced by benthic fauna otherwise unable to survive in the mid ocean. We propose that globally sea floor elevation has no effect on deep sea biomass; pelagic plus benthic biomass is constant within a given surface productivity regime.

Ceratothoa steindachneri (Isopoda: Cymothoidae) new to British waters with a key to north-east Atlantic and Mediterranean Ceratothoa

This paper presents the first record of Ceratothoa steindachneri from Cornwall, making it the first resident species of the fish-parasitic isopod family Cymothoidae in Britain. The host is Echiichthys vipera (Trachinidae) the lesser weever fish, the isopod attaching to the host tongue. A complete redescription and reillustration for C. steindachneri is given, and a neotype is selected for the species Ceratothoa parallela. A key to the north-east Atlantic and Mediterranean species of Ceratothoa is included, with a brief illustrated account for each species.

Adaptive Evolution of Deep-Sea Amphipods from the Superfamily Lysiassanoidea in the North Atlantic

In this study we reconstruct phylogenies for deep sea amphipods from the North Atlantic in order to test hypotheses about the evolutionary mechanisms driving speciation in the deep sea. We sequenced five genes for specimens representing 21 families. Phylogenetic analyses showed incongruence between the molecular data and morphological taxonomy, with some morphologically distinct taxa showing close molecular similarity. Approximate dating of nodes based on available calibration suggested adaptation to the deep sea around the Cretaceous-Palaeogene boundary, with three identified lineages within the deep-sea radiation dating to the Eocene–Oligocene transition. Two of those lineages contained species currently classified in multiple families. We reconstructed ancestral nodes based on the mouthpart characters that define trophic guilds (also used to establish the current taxonomy), and show a consistent transition at the earliest node defining the deep-sea lineage, together with increasing diversification at more recent nodes within the deep-sea lineage. The data suggest that the divergence of species was adaptive, with successive diversification from a non-scavenging ancestor to ‘opportunistic’, ‘obligate’ and ‘specialised’ scavengers. We propose that the North Atlantic species studied provide a strong case for adaptive evolution promoted by ecological opportunity in the deep sea.

Multiple processes generate productivity-diversity relationships in experimental wood-fall communities.

Energy availability has long been recognized as a predictor of community structure, and changes in both terrestrial and marine productivity under climate change necessitate a deeper understanding of this relationship. The productivity-diversity relationship (PDR) is well explored in both empirical and theoretical work in ecology, but numerous questions remain. Here, we test four different theories for PDRs (More-Individuals Hypothesis, Resource-Ratio Theory, More Specialization Theory, and the Connectivity-Diversity Hypothesis) with experimental deep-sea wood falls. We manipulated productivity by altering wood-fall sizes and measured responses after 5 and 7 years. In November 2006, 32 Acacia sp. logs were deployed at 3203 m in the Northeast Pacific Ocean (Station Deadwood: 36.154098 degrees N, 122.40852 degrees W). Overall, we found a significant increase in diversity with increased wood-fall size for these communities. Increases in diversity with wood-fall size occurred because of the addition of rare species and increases of overall abundance, although individual species responses varied. We also found that limited dispersal helped maintain the positive PDR relationship. Our experiment suggests that multiple interacting mechanisms influence PDRs.

Hirondellea namarensis (Crustacea: Amphipoda: Lysianassoidea: Hirondelleidae), a new deep-water scavenger species from the Mid-Atlantic Ridge

Abstract A new species of the deep-sea scavenging genus Hirondellea (Crustacea: Amphipoda) is described from bathyal depths in the Azores region and on the Mid-Atlantic Ridge. The new species belongs to a group of Hirondellea species which possess an incised inner ramus of uropod 2 and an anteriorly directed spine on epimeron 1. It can be distinguished from other members of this group by a combination of characters: the gnathopod 1 and 2 palm shape; the broadly rounded epimeron 3; the longer telson and broadly rounded head lobe; and the broadly rounded epistome. The species most closely resembles H. wolfendeni, from which it can be distinguished by the shape of the propod of gnathopod 2 and the length of the pereopod 7 propodus. An updated key to the genus Hirondellea is provided.

Amphipoda from marine caves of Hong Kong Island

A collection of 32 amphipod species from submarine cave habitats and control sites to the east of Hong Kong Island was made during a joint NHM/SWIMS expedition in October 2002. Three families (Caprellidae, Endevouridae and Kamakidae), nine genera (Monoliropus, Caprella, Paraloiloi, Leptocheirus, Microjassa, Cerapus, Listriella, Ensayara and Birubius) and 12 species (Monoliropus concavimanus sp. nov.; Caprella aff. penantis; Elasmopus sp. A; Ptilohyale aff. barbicornis; Cerapus sp. A; Paraloiloi sp. A; Ensayara bifurcata sp. nov.; Birubius nauarchuncus sp. nov.; Podocerus cluspiclunis sp. nov.; Megaluropus sp. A; Urothoe sp. A (aff. cuspis); and Urothoe aff. spinidigitus) can be added to the amphipod checklist for the South China Sea area.

The distribution of Ceratothoa steindachneri (Crustacea: Isopoda: Cymothoidae) parasitic in Echiichthys vipera in the north-east Atlantic

The distribution of the recently discovered association of the parasitic isopod Ceratothoa steindachneri (Isopoda: Cymothoidae) with the lesser weever fish (Echiichthys vipera) is reported. Ceratothoa steindachneri appears to have colonized the south-west coast of the UK between the 1960s and the 1980s, possibly as a result of range expansion due to climate change. The occurrence of C. steindachneri in E. vipera from Arcachon, France, indicates that this association has been occurring for over 100 years. Our data confirm that C. steindachneri is able to parasitize a broad range of fish hosts.

Abyssal scavenging demersal fauna at two areas of contrasting productivity on the Subantarctic Crozet Plateau, southern Indian Ocean

The Crozet Plateau is situated below typical high-nutrient, low-chlorophyll (HNLC) waters of the southern Indian Ocean. The area to the east of the Crozet Islands experiences high levels of surface productivity during the austral summer due to natural iron enrichment from terrestrial sources and favourable light conditions. The demersal scavenging fauna at two areas of contrasting productivity, to the east and south of the islands, were investigated using two landers equipped with baited cameras and traps. Five species of scavenging fish were observed along with five groups of invertebrates during a single deployment of the RObust BIOdiversity (ROBIO) lander. Further deployments of the Fish RESPirometry (FRESP) video lander yielded no additional scavenging fish species. A modelled arrival and departure curve for the abyssal grenadier Coryphaenoides armatus suggests a region of low food availability compared to other regions worldwide. The ROBIO-derived abundance estimate for C. armatus of 187 ind. km–2 is comparable with published trawl-derived estimates. Significantly more amphipods were collected to the south of the islands, which was subject to lower organic matter supply. Reasons for this are unknown but may be due to differing current direction/velocities, or increased fish predation at the enriched site. The numerically dominant amphipod species present was Paralicella caperesca, followed by Eurythenes gryllus and Orchomenella gerulicorbis. A further five species were observed in low numbers, some occurring only once. One, Paracallisoma sp. nov, was a new species.

Revision of the amphipod genus Valettiopsis Holmes, 1908 (Crustacea: Lysianassoidea), with the addition of three new species

The amphipod genus Valettiopsis Holmes, 1908 currently comprises four species. Valettiopsis macrodactyla Chevreux, 1909 is redescribed from new material. Two new species, Valettiopsis longidactyla and Valettiopsis minuta, are described and illustrated, and Valettiopsis macrodactyla (sensu Lincoln and Thurston, 1983) is renamed Valettiopsis lincolni sp. nov. General information is provided for the remaining species in the genus (Valettiopsis dentata Holmes, 1908, Valettiopsis multidentata Barnard, 1961 and Valettiopsis ruffoi Serejo and Wakabara, 2003) and a key to the seven species is provided.

A revision of the genus Paracallisoma Chevreux, 1903 (Crustacea: Amphipoda: Scopelocheiridae: Paracallisominae) with a redescription of the type species of the genus Paracallisoma and the description of two new genera and two new species from the Atlantic Ocean

The genus Paracallisoma (Crustacea: Amphipoda) is revised and the type species, Paracallisoma alberti is redescribed based on holotype material supplemented with new material from the region of the type locality. This revision results in the establishment of two new genera, Pseudocallisoma gen. nov. and Haptocallisoma gen. nov., and the description of a new species of Haptocallisoma and a new species of Paracallisoma from the North Atlantic Ocean. An account of all known species within the three genera is given and updated keys to the genera and species are provided.