A. Louise Allcock

The thermohaline expressway: the Southern Ocean as a centre of origin for deep-sea octopuses

Understanding how environmental forcing has generated and maintained large‐scale patterns of biodiversity is a key goal of evolutionary research and critical to predicting the impacts of global climate change. We suggest that the initiation of the global thermohaline circulation provided a mechanism for the radiation of Southern Ocean fauna into the deep sea. We test this hypothesis using a relaxed phylogenetic approach to coestimate phylogeny and divergence times for a lineage of octopuses with Antarctic and deep‐sea representatives. We show that the deep‐sea lineage had their evolutionary origins in Antarctica, and estimate that this lineage diverged around 33 million years ago (Ma) and subsequently radiated at 15 Ma. Both of these dates are critical in development of the thermohaline circulation and we suggest that this has acted as an evolutionary driver enabling the Southern Ocean to become a centre of origin for deep‐sea fauna. This is the first unequivocal molecular evidence that deep‐sea fauna from other ocean basins originated from Southern Ocean taxa and this is the first evidence to be dated.

Southern Ocean diversity: new paradigms from molecular ecology

Southern Ocean biodiversity reflects past climate, oceanographic, and tectonic changes. Molecular data from contemporary populations carry signatures of these processes. Here, we review new molecular studies on Southern Ocean benthic fauna. Many of these studies focus on species with extensive geographic or bathymetric distributions, and resolve taxonomic questions. Reviewing all available data, we show that, in addition to reflecting life-history characteristics, the molecular signals found in these studies provide an insight into how species survived the last glacial maximum (LGM). We identify molecular signatures that are characteristic of surviving glacial cycles in small refugia on the continental shelf and distinguish them from molecular signatures that are indicative of surviving glacial cycles in the deep sea.

Ecological Role of Submarine Canyons and Need for Canyon Conservation: A Review

Submarine canyons are major geomorphic features of continental margins around the world. Several recent multidisciplinary projects focused on the study of canyons have considerably increased our understanding of their ecological role, the goods and services they provide to human populations, and the impacts that human activities have on their overall ecological condition. Pressures from human activities include fishing, dumping of land-based mine tailings, and oil and gas extraction. Moreover, hydrodynamic processes of canyons enhance the down-canyon transport of litter. The effects of climate change may modify the intensity of currents. This potential hydrographic change is predicted to impact the structure and functioning of canyon communities as well as affect nutrient supply to the deep-ocean ecosystem. This review not only identifies the ecological status of canyons, and current and future issues for canyon conservation, but also highlights the need for a better understanding of anthropogenic impacts on canyon ecosystems and proposes other research required to inform management measures to protect canyon ecosystems.

Future challenges in cephalopod research

We thank Anto´nio M. de Frias Martins, past President of the Unitas Malacologica and Peter Marko, President of the American Malacological Society for organizing the 2013 World Congress of Malacology, and the Cephalopod International Advisory Committee for endorsing a symposium held in honour of Malcolm R. Clarke. In particular, we would like to thank the many professional staff from the University of the Azores for their hospitality, organization, troubleshooting and warm welcome to the Azores. We also thank Malcolm Clarke’s widow, Dorothy, his daughter Zoe¨, Jose´ N. Gomes-Pereira and numerous colleagues and friends of Malcolm’s from around the world for joining us at Ponta Delgada. We are grateful to Lyndsey Claro (Princeton University Press) for granting copyright permissions.

The contribution of molecular data to our understanding of cephalopod evolution and systematics: a review

The first DNA sequence of a cephalopod was published in 1983 and the first molecular paper focusing on cephalopods was published in 1994. In this review we trace progress in the field. We examine the placement of Cephalopoda with respect to other molluscan classes and we examine relationships within Cephalopoda. We provide a summary tree of the relationships between cephalopod orders and we examine relationships of taxa within each of these orders. Although much knowledge has been gained over the past 20 years, deeper-level relationships are still not well understood and there is still much scope for further research in this field. Genomic studies are likely to contribute significantly to our knowledge in the future.

The ink sac clouds octopod evolutionary history

Difficulties in elucidating the evolutionary history of the octopods have arisen from problems in identifying informative morphological characters. Recent classifications have divided the largest group, the incirrate octopods, into five groups. These include the pelagic superfamily Argonautoidea and three gelatinous pelagic families (Vitreledonellidae, Bolitaenidae, Amphitretidae). All benthic incirrate octopods have been accommodated in the family Octopodidae, itself divided into four subfamilies, Octopodinae, Eledoninae, Bathypolypodinae and Graneledoninae, which are defined by the presence or absence of an ink sac, and uniserial or biserial sucker arrangements on the arms. We used relaxed clock models in a Bayesian framework and maximum likelihood methods to analyse three nuclear and four mitochondrial genes of representatives from each of the previous subfamilies. Strong evidence indicates that the family Octopodidae is paraphyletic and contains the gelatinous pelagic families. The subfamilies of Octopodidae recognised in earlier works do not reflect evolutionary history. The following clades were supported in all analyses: (1) Eledone/Aphrodoctopus, (2) Callistoctopus/Grimpella/Macroctopus/Scaeurgus, (3) Abdopus/Ameloctopus/Amphioctopus/Cistopus/Hapalochlaena/Octopus, (4) Enteroctopus/Muusoctopus/Vulcanoctopus, (5) Vitreledonella/Japetella, (6) Southern Ocean endemic and deep-sea taxa with uniserial suckers. These clades form the basis for a suite of taxa assigned family taxonomic rank: Amphitretidae, Bathypolypodidae, Eledonidae, Enteroctopodidae, Megaleledonidae and Octopodidae sensu nov. They are placed within the superfamily Octopodoidea.

A vertical wall dominated by Acesta excavata and Neopycnodonte zibrowii, part of an undersampled group of deep-sea habitats.

We describe a novel biotope at 633 to 762 m depth on a vertical wall in the Whittard Canyon, an extensive canyon system reaching from the shelf to the deep sea on Ireland’s continental margin. We explored this wall with an ROV and compiled a photomosaic of the habitat. The assemblage contributing to the biotope was dominated by large limid bivalves, Acesta excavata (mean shell height 10.4 cm), and deep-sea oysters, Neopycnodonte zibrowii, at high densities, particularly at overhangs. Mean density of N. zibrowii increased with depth, with densities of the most closely packed areas of A. excavata also increasing with depth. Other taxa associated with the assemblage included the solitary coral Desmophyllum dianthus, cerianthid anemones, comatulid crinoids, the trochid gastropod Margarites sp., the portunid crab Bathynectes longispina and small fish of the family Bythitidae. The scleractinian coral Madrepora oculata, the pencil urchin Cidaris cidaris and a species of Epizoanthus were also common. Prominent but less abundant species included the flytrap anemone Actinoscyphia saginata, the carrier crab Paramola cuvieri, and the fishes Lepidion eques and Conger conger. Observations of the hydrography of the canyon system identified that the upper 500 m was dominated by Eastern North Atlantic Water, with Mediterranean Outflow Water beneath it. The permanent thermocline is found between 600 and 1000 m depth, i.e., in the depth range of the vertical wall and the dense assemblage of filter feeders. Beam attenuation indicated nepheloid layers present in the canyon system with the greatest amounts of suspended material at the ROV dive site between 500 and 750 m. A cross-canyon CTD transect indicated the presence of internal waves between these depths. We hypothesise that internal waves concentrate suspended sediment at high concentrations at the foot of the vertical wall, possibly explaining the large size and high density of filter-feeding molluscs.

Molecular Phylogenies Support Homoplasy of Multiple Morphological Characters Used in the Taxonomy of Heteroscleromorpha (Porifera: Demospongiae)

Sponge classification has long been based mainly on morphocladistic analyses but is now being greatly challenged by more than 12 years of accumulated analyses of molecular data analyses. The current study used phylogenetic hypotheses based on sequence data from 18S rRNA, 28S rRNA, and the CO1 barcoding fragment, combined with morphology to justify the resurrection of the order Axinellida Lévi, 1953. Axinellida occupies a key position in different morphologically derived topologies. The abandonment of Axinellida and the establishment of Halichondrida Vosmaer, 1887 sensu lato to contain Halichondriidae Gray, 1867, Axinellidae Carter, 1875, Bubaridae Topsent, 1894, Heteroxyidae Dendy, 1905, and a new family Dictyonellidae van Soest et al., 1990 was based on the conclusion that an axially condensed skeleton evolved independently in separate lineages in preference to the less parsimonious assumption that asters (star-shaped spicules), acanthostyles (club-shaped spicules with spines), and sigmata (C-shaped spicules) each evolved more than once. Our new molecular trees are congruent and contrast with the earlier, morphologically based, trees. The results show that axially condensed skeletons, asters, acanthostyles, and sigmata are all homoplasious characters. The unrecognized homoplasious nature of these characters explains much of the incongruence between molecular-based and morphology-based phylogenies. We use the molecular trees presented here as a basis for re-interpreting the morphological characters within Heteroscleromorpha. The implications for the classification of Heteroscleromorpha are discussed and a new order Biemnida ord. nov. is erected.

Divergence of nematocysts in two colour morphs of the intertidal beadlet anemone Actinia equina

In the common intertidal sea anemone Actinia equina (Cnidaria: Actiniaria) the morphological plasticity and lack of hard parts has caused considerable debate as to what constitutes a species. Over the last several years genetic studies have indicated that this ‘species’ consists of various separate gene-pools which appear to function as cryptic biological species. Conventional taxonomy has often concentrated on the use of a cnidome, the type, structure and number of nematocysts (stinging’ cells). However, the usefulness of nematocysts to distinguish among various morphs of A. equina and other anthozoan species has recently been questioned. Here we describe the first detailed study of nematocyst differences between two well characterized genetically differentiated morphs with different coloured pedal discs. Measurements were taken from each type of nematocyst in five different tissues. Contrary to expectations, clear and significant nematocyst differences were found between Actinia with red or pink pedal discs and others with green to grey pedal discs. These findings support previous electrophoretic studies and suggest that quantitative descriptions of the cnidome may accurately identify separate species within other genera of Anthozoa.

Characterization of polymorphic microsatellites for the rough periwinkle gastropod, Littorina saxatilis (Olivi, 1792) and their cross-amplification in four congeners

Eight new microsatellite loci were characterized for Littorina saxatilis (Olivi, 1792) and tested for their cross-hybridization in congeners. All loci were polymorphic in Irish and Celtic Sea samples, with an average number of alleles per locus of 15 (range, 6–31). Observed and expected locus heterozygosities ranged from 26 to 85% and from 53 to 92%, respectively. Three loci showed excess homozygosity and significant departures from Hardy–Weinberg expectations in one sample, possibly due to null alleles, population structuring or inbreeding. No linkage disequilibrium was detected among loci within samples. A high degree of cross-hybridization was observed in closely related congeners and most loci were polymorphic. These markers will be useful for investigating population genetic diversity and connectivity in coastal populations, especially for marine reserve design.