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Megabenthic soft bottom communities of trawlable grounds have been studied since the first few decades of the last century, thanks to trawl fishing technologies. Despite providing an extensive amount of presence data, trawling cannot be considered reliable from a quantitative point of view, frequently giving only weak information about sessile species density, large and small-scale distribution and main habitat features. The recent development of visual technologies on remotely operated vehicles (ROVs) can give a more accurate approach for the study of mega-epibenthic communities. The present study reports the application of both ROV imaging and trawling approaches for the study of a large aggregation (i.e. field) of the red sea pen Pennatula rubra in the Ionian Sea. Density, biomass and population structure were studied in the same population of P. rubra. The density assessed by ROV was significantly higher than that estimated with a three-year series of trawling surveys. Trawling gear efficiency in the removal of P. rubra was low overall. Incidental mortality can be very high due to damage to those specimens that encounter the trawl net but are not directly captured. However, sampling of several colonies by trawling was necessary to establish biometric correlations to estimates of size and biomass from ROV imaging. Trawling catch abundance/biomass data could be useful to identify areas of higher concentration of sea pens, while ROV imaging can be used to monitor these fields in a non-destructive manner that would be consistent with protection measures.

The sea pens Funiculina quadrangularis, Pennatula aculeata, Pennatula phosphorea, Pteroeides spinosum and Veretillum cynomorium are known to be characteristic species of the habitat ‘pennatulacean communities on circalittoral and upper bathyal soft bottoms’, described recently on the northern Atlantic Spanish shelf under the terms of the EU directives. Distribution, abundance and environmental data collected from 1995 to 2010 in the Northern Spanish Shelf Groundfish Surveys in the Cantabrian Sea and off Galicia (SPNGFS) were analysed. Although low densities of sea pens were commonly found over the years, some aggregations were shown. Multivariate analysis separated the aggregations of F. quadrangularis and of Pennatula spp. found on circalittoral soft bottoms. In addition, evidence of aggregations of F. quadrangularis on upper bathyal sites was also found. Depth and longitude, which were closely related to organic matter and sediment particle size, were key factors in determining the distribution and abundance of these aggregations. However, very little information on distribution and density of the species P. spinosum and V. cynomorium was obtained. Details of community composition of F. quadrangularis and Pennatula spp. were studied and compared with those of the OSPAR habitat “sea pen and burrowing megafauna communities” in other areas. The results improve our knowledge concerning sea pen communities in the southern Bay of Biscay and contribute to a global assessment of the status of these communities in the northeast Atlantic.

Bioluminescence, the ability of living organisms to emit visible light, is an important ecological feature for many marine species. To fulfil the ecological role (defence, offence, or communication), bioluminescence needs to be finely controlled. While many benthic anthozoans are luminous, the physiological control of light emission has only been investigated in the sea pansy, Renilla koellikeri. Through pharmacological investigations, a nervous catecholaminergic bioluminescence control was demonstrated for the common sea pen, Pennatula phosphorea, and the tall sea pen, Funiculina quadrangularis. Results highlight the involvement of adrenaline as the main neuroeffector triggering clusters of luminescent flashes. While noradrenaline and octopamine elicit flashes in P. phosphorea, these two biogenic amines do not trigger significant light production in F. quadrangularis. All these neurotransmitters act on both the endodermal photocytes located at the base and crown of autozooids and specific chambers of water-pumping siphonozooids. Combined with previous data on R. koellikeri, our results suggest that a catecholaminergic control mechanisms of bioluminescence may be conserved in Anthozoans.

Here we describe unusual morphological traits identified on colonies of the deep-water sea pens , and sp. from the Northwest Atlantic, namely the presence of hypertrophied polyps, split polyp leaves, and autozooids budding on the surface of polyp leaves (as opposed to the edges). These observations are not in line with the species diagnoses, but there is no evidence to justify the colonies' identifications as different or new taxa. We also provide DNA sequence data for mitochondrial and nuclear markers and suggest a geographic range extension for into the NW Atlantic. Although we do not know the origin of these peculiarities, we hypothesize that given the rarity of this finding, predation could have resulted in the observed split polyp leaves in and influence the development of hypertrophied polyps. Given that these sea pen taxa are some of the few taxa to display more than three types of polyps (i.e., polymorphism), we also discuss the hypothesis that hypertrophied polyps might differ from autozooids and represent an undescribed type of polyp. Nevertheless, future hypothesis-driving studies are necessary to factually explain these observations.

Colonies of the endangered red sea pen Pennatula rubra (Cnidaria: Pennatulacea) sampled by trawling in the northwestern Mediterranean Sea were analyzed. Biometric parameters, such as total length, peduncle length, number of polyp leaves, fresh weight, and dry weight, were measured and related to each other by means of regression analysis. Ad hoc models for future inferencing of colonies size and biomass through visual techniques were individuated in order to allow a non-invasive study of the population structure and dynamics of P. rubra.

Recent advances in deep-sea exploration technology coupled with an increase in worldwide biotic surveys, biological research, and underwater photography in shallow water marine regions such as coral reefs, has allowed for a relatively rapid expansion of our knowledge in the global diversity of many groups of marine organisms. This paper is part of the PLoS ONE review collection of WoRMS (the Worldwide Register of Marine Species), on the global diversity of marine species, and treats the pennatulacean octocorals, a group of cnidarians commonly referred to as sea pens or sea feathers. This also includes sea pansies, some sea whips, and various vermiform taxa. Pennatulaceans are a morphologically diverse group with an estimated 200 or more valid species, displaying worldwide geographic and bathymetric distributions from polar seas to the equatorial tropics and from intertidal flats to over 6100 m in depth. The paper treats new discoveries and taxa new to science, and provides greater resolution in geographic and bathymetric distributions data than was previously known, as well as descriptions of life appearances in life and in situ observations at diverse depth.

Octocorals have proven to be a prolific source of bioactive natural products, exhibiting a wide spectrum of pharmacological activities. Among octocorals, Pennatulaceans, commonly known as sea pens, are among the most dominant soft coral species living in benthic communities. Nonetheless, reports on bioactivity and chemical investigations of this genus are scarce. This prompted us to shed light on the pharmacological potential of the extracts of the sea pen Pennatula phosphorea, Linneus 1758, and gain an overview of its metabolome. Crude octocoral extracts, obtained with a modified Kupchan extraction protocol, were assessed for their bioactivity potential, revealing the hexanic extract to exert anti-inflammatory effects and interesting protective properties in an in vitro model of sarcopenia and in auditory HEI-OC1 cisplatin-treated cells, while the chloroformic extract was active in reducing A375 melanoma cell viability in a concentration-dependent manner. An untargeted metabolomic analysis unveiled that P. phosphorea collects a wide array of glycerophospholipids and phosphosphingolipids belonging to the ceramide phosphoinositol class, which were exclusive or more abundant in the hexanic extract. Their proven anti-inflammatory and cytoprotective effects could demonstrate the activity shown by the P. phosphorea hexanic extract. In addition, a group of prostaglandins, eluted mainly in the chloroformic extract, were putatively annotated. Since prostanoids from marine origin have been demonstrated to exert cytotoxic and anti-proliferative properties against various cancer cell lines, the presence of PGs in the P. phosphorea chloroform extract could justify its anti-melanoma activity. This is the first report on the presence of glycerophospholipids, phosphosphingolipids, and prostaglandins, along with the identification of novel congeners, in sea pens.

Sea pen communities are United Nations General Assembly-designated Vulnerable Marine Ecosystems which occur worldwide in soft-bottom sediments where trawling often occurs. However, the ability of marine managers to assess, monitor and mitigate impacts to sea pens at national scales has been constrained by a limited understanding of their environmental requirements, geographical distribution and responses to trawling. In this study, we used random forest species distribution modelling (SDM) to predict the distribution of suitable habitat for 3 sea pen species (tall sea pen Funiculina quadrangularis, slender sea pen Virgularia mirabilis and phosphorescent sea pen Pennatula phosphorea) on the UK continental shelf, exploring the results relative to the distribution of fishing activity. Occurrence of all 3 species corresponded to areas of low current and wave velocity, where suspended matter in the water column was also low. However, for F. quadrangularis, the largest species, the models indicated substantially different drivers of distribution between the Greater North Sea and Celtic Seas ICES Ecoregions. This disparity appears to reflect modification to the range and realised niche of this species in the Greater North Sea, due to trawling impacts. P. phosphorea and V. mirabilis appear to be more resilient to trawling, with no clear negative relationships observed. Our findings illustrate the value of broadscale qualitative comparisons between SDMs and human activity data for insights on pressure–state relationships. When combined with robust distribution maps, this improved understanding of vulnerability will enable marine managers to make ecologically sound, defensible decisions and deliver tangible conservation outcomes for sea pen communities.

Comparisons between plants and sessile modular colonial invertebrates offer interesting parallelisms between plant and animal body plans after millions of years of divergent evolution. Among these parallelisms might be the existence and distribution of intraindividual heterogeneity in organ traits, also named subindividual variability. Subindividual variability is quantitatively important and has many consequences for plant individuals, populations and communities, and for animal consumers as well. However, could a similar process of subindividual variability occur in sea pens, which have a modular architecture similar to that of plants? In the literature of marine invertebrates very little is known about the presence and magnitude of subindividual variability in modular organisms. This study provides for the first time a quantitative assessment of subindividual variability in sea pens, analysing certain biometric features of reiterated structures that presumably have some ecological function, and offers an initial comparison of quantitative levels of subindividual variation between plants and sea pens.

Deep-sea corals are fragile and long-lived species that provide important habitat for a variety of taxa. The rarity ofin situobservations in deep waters off Newfoundland, Canada, motivated the first extensive deep-sea research cruise to that region in 2007. We conducted 7 dives in 3 canyons (Haddock Channel, Halibut Channel, and Desbarres Canyon) with ROPOS (Remotely Operated Platform for Ocean Science). Over 160 000 coral colonies were enumerated and, of the 28 species found,Acanella arbuscula,Pennatulaspp., andFlabellumspp. were most frequently observed. The largest coral observed wasKeratoisis grayiat over 2 m in height. Corals spanned the entire depth range sampled (351 to 2245 m) and inhabited all bottom types surveyed, but boulder and cobble habitats were most species-rich. Assemblages differed significantly with depth class and bottom type. The unique assemblage at outcrops was strongly driven by the presence ofDesmophyllum dianthus.Keratoisis grayi,D. dianthus, andAnthomastusspp. were largely absent in mud-sand habitats. Sea pen meadows covered large tracts of muddy seafloor spanning >1 km.Acanella arbusculaandFlabellumspp. characterised large coral fields with abundant corals but relatively low species richness. These results highlight not only the importance of hard structure in determining patterns of coral distributions, abundances, and assemblages, but also the need to focus conservation efforts on a variety of habitats to ensure protection for the full suite of deep-sea coral species.