Regulation of the mTOR signaling pathway: from laboratory bench to bedside and back again

Recent publications have moved us significantly closer to a complete understanding of the mammalian target of rapamycin (mTOR) signaling pathway, which plays a central role in the control of growth and metabolism and is dysregulated in a broad spectrum of human diseases, including cancer, tuberous sclerosis, diabetes, and cardiovascular and neurodegenerative diseases. Rapamycin-related mTOR inhibitors have shown clinical efficacy in several of these diseases, and novel inhibitors currently in development will be valuable tools for further dissections of the mTOR signaling network in human health and disease

Cephalopod fauna of subantarctic islands: new information from predators

Using top predators as biological samplers, we collected information on the poorly known‹but ecologically important‹cephalopod fauna of the Southern Ocean. A total of 4527 cephalopod beaks were identified from stomach contents of Patagonian toothfish caught in slope waters at Crozet and Kerguelen Islands (Indian Ocean). Main prey were the squid Gonatus antarcticus and Kondakovia longimana at both localities, Taonius sp. B (Voss) and Slosarczykovia circumantarctica at Crozet, and Chiroteuthis veranyi and Mastigoteuthis psychrophila at Kerguelen. Fish diet together with the feeding habits of sharks and seabirds show that at least 36 and 38 different cephalopod species inhabit Crozet and Kerguelen waters, respectively. Oegopsid squid dominate the assemblages (29 and 32 taxa at Crozet and Kerguelen, respectively) over octopods (7 and 5 taxa), 1 species of sepiolid occurring at Kerguelen. These rich communities include pelagic squid, bentho-pelagic cirrate octopods and a few endemic benthic octopodids. The results emphasize the importance of onychoteuthids and gonatids in the nutrition of top consumers in the Southern Ocean and they shed new light on the role of chiroteuthids, mastigoteuthids and cirrate octopods in the trophic web of the marine ecosystems

Antarctic jaws: cephalopod prey of sharks in Kerguelen waters

Only five species of sharks have been recorded in the Southern Ocean, where their biology is essentially unknown. We investigated the feeding habits of the three commonest species from stomach content analysis of specimens taken as bycatches of the fishery targeting the Patagonian toothfish (Dissostichus eleginoides) in upper slope waters of the Kerguelen Archipelago. The three species prey upon a diversity of fishes and cephalopods. They segregate by feeding on different species of squids of different sizes. The small lanternsharks (Etmopterus cf. granulosus; 0.3 m on average) feed on small-sized Mastigoteuthis psychrophila, while the large porbeagles (Lamna nasus; 1.9 m) feed on small-sized histioteuthids (Histioteuthis atlantica and H. eltaninae) and on medium-sized juvenile ommastrephids of the genus Todarodes. Finally, the huge sleeper sharks (Somniosus cf. microcephalus; 3.9 m) prey upon large-sized cephalopods (Kondakovia longimana and Taningia danae) and giant squids (Mesonychoteuthis hamiltoni and Architeuthis dux). Thus sleeper shark is a fish with sperm whale-like feeding habits and, hence, the second top predator known to science to rely significantly on giant squids. Prey species and biology indicate that porbeagles are pelagic predators in the entire water column, while sleeper sharks are mainly benthic top predators and scavengers. The present study also underlines the diversity and biomass of the poorly known cephalopod fauna, including giant squids, occurring in outer shelf and upper slope waters surrounding subantarctic islands

Diet of the squid Moroteuthis ingens (Teuthoidea: Onychoteuthidae) in the upper slope waters of the Kerguelen Islands

The diet of the onychoteuthid squid Moroteuthis ingens was investigated through stomach content analyses of 72 individuals collected aboard a trawler targeting Patagonian toothfish Dissostichus eleginoides in the upper slope waters of the Kerguelen Archipelago. M. ingens is primarily piscivorous (67% by number and 87% by reconstituted mass), although the diet also includes squids (12 and 12%, respectively) and crustaceans (21 and <1%, respectively). The main fish prey were the paralepidid Arctozenus risso (28% by reconstituted mass), the gempylid Paradiplospinus gracilis (24%) and various myctophids. M. ingens preyed also upon conspecifics (cannibalism, 6%), and the euphausiid Euphausia triacantha was the main crustacean item. Most of the prey are pelagic organisms performing diurnal migration, suggesting that the benthopelagic M. ingens catch them when they are near the bottom during the day. In turn, M. ingens is a prey for several species of top predators, including D. eleginoides and air-breathing vertebrates. M. ingens thus contributes to carbon export from the pelagic environment to the benthos and from the ocean to the atmosphere as carbon dioxide expired by birds and mammals

Interactions between longline vessels and seabirds in Kerguelen waters and a method to reduce seabird mortality

A longline fishery for Dissostichus eleginoides has recently developed in the vicinity of South Georgia and Kerguelen islands, two internationally important breeding areas for procellariiform birds. The number of hooked birds and a method to reduce mortality were investigated during 13 days of fishing activity in Kerguelen waters in February 1994. Between 100 and 600 seabirds were always observed behind the longline vessel during daytime. The main ship-following species were the white-chinned petrel Procellaria aequinoctialis (67% of counts), giant petrels Macronectes spp. (8%) and the wandering albatross Diomedea exulans (11%), black-browed albatross D. melanophris (6%) and grey-headed albatross D. chrysostoma (2%). Only diving species were caught on the lines, i.e. the white-chinned petrel (n = 36) and the grey-headed albatross (n = 2). Marked differences in the mortality rate were observed between day and night (1·00 versus 0·38 birds per 1000 hooks), and at night when the decklights were on or off (0·59 versus 0·15 birds per 1000 hooks). Dumping of homogenized offal during line settings greatly reduced incidental capture of seabirds, mainly because birds were more attracted by offal than by hooked baits. We therefore propose that the dumping of offal during line settings should be included in the regulations of the longline fishery for Dissostichus in order to minimize seabird mortality

Fatty acid signature analysis documents the diet of five myctophid fish from the Southern Ocean

International audienceFatty acid (FA) and fatty alcohol (FAlc) compositions of both total lipid and neutral lipid fractions were studied for five myctophid species sampled in Kerguelen waters. Both qualitative and quantitative FA signature analyses were then performed to investigate their diet over longer time scales than the conventional stomach content analysis. Regarding their lipid class, FA and FAlc compositions, the five species could be discriminated into two groups: wax-ester-rich species (Electrona antarctica, Krefftichthys anderssoni) characterised by large amounts of monounsaturated FAs ([73% of total FAs) and triacylglycerol- rich species (Electrona carlsbergi, Gymnoscopelus nicholsi, Protomyctophum bolini) with major amounts of saturated and monounsaturated FAs ([29 and[46% of total FAs, respectively). Qualitative and quantitative FA analyses showed that K. anderssoni mainly preyed upon copepods, E. antarctica upon copepods and more euphausiids and P. bolini and E. carlsbergi mainly upon euphausiids with some copepods, while G. nicholsi had a more diverse diet. This study shows the usefulness of quantitative statistical analysis to determine the diet of Antarctic and sub-Antarctic predators and stresses the need of increasing the lipid and FA analyses of more zooplanktonic and micro-nektonic marine species

Coelenterazine detection in five myctophid species from the Kerguelen Plateau

Myctophidae comprise the largest biomass of mesopelagic fishes in the Southern Ocean. This family has the ability to emit light – bioluminescence – via specific organs called photophores, and from the head and caudal organs. Through biochemical analyses, this study reveals that coelenterazine is the substrate for light reaction in the five most common myctophid species from the Southern Ocean. The results also support the hypothesis of the acquisition of this molecule via the food chain and reveal the presence of two stabilised storage forms of coelenterazine (enol-sulfate and dehydrocoelenterazine) within various tissues of the studied species. Finally, detection of coelenterazine in the gonads also suggests the potential maternal transfer of the bioluminescence capability to the offspring.Les Myctophidae représentent la plus grande biomasse de poissons mésopelagiques de l’océan Austral. Cette famille possède la capacité d’émettre de la lumière – bioluminescence – via des organes spécifiques appelés photophores, ainsi que de la tête et des organes caudaux. A travers des analyses biochimiques, cette étude révèle que la coelentérazine serait le substrat utilisé pour la réaction lumineuse chez cinq espèces de Myctophidae les plus communes de l’océan Austral. Les résultats soutiennent également l’hypothèse de l’acquisition de cette molécule via la chaîne alimentaire ainsi que le stockage de la coelentérazine sous deux formes stabilisées (énol-sulfate et déhydrocoelentérazine) au sein de plusieurs tissus des espèces étudiées. Finalement la présence de coelentérazine dans les gonades suggère également un potentiel transfert maternel des capacités lumineuses à la descendance

Détection de la coelentérazine chez cinq espèces de Myctophidae du plateau des Iles Kerguelen

International audienceMyctophidae comprise the largest biomass of mesopelagic fishes in the Southern Ocean. This family has the ability to emit light – bioluminescence – via specific organs called photophores, and from the head and caudal organs. Through biochemical analyses, this study reveals that coelenterazine is the substrate for light reaction in the five most common myctophid species from the Southern Ocean. The results also support the hypothesis of the acquisition of this molecule via the food chain and reveal the presence of two stabilised storage forms of coelenterazine (enol-sulfate and dehydrocoelenterazine) within various tissues of the studied species. Finally, detection of coelenterazine in the gonads also suggests the potential maternal transfer of the bioluminescence capability to the offspring.Les Myctophidae représentent la plus grande biomasse de poissons mésopelagiques de l’océan Austral. Cette famille possède la capacité d’émettre de la lumière – bioluminescence – via des organes spécifiques appelés photophores, ainsi que de la tête et des organes caudaux. A travers des analyses biochimiques, cette étude révèle que la coelentérazine serait le substrat utilisé pour la réaction lumineuse chez cinq espèces de Myctophidae les plus communes de l’océan Austral. Les résultats soutiennent également l’hypothèse de l’acquisition de cette molécule via la chaîne alimentaire ainsi que le stockage de la coelentérazine sous deux formes stabilisées (énol-sulfate et déhydrocoelentérazine) au sein de plusieurs tissus des espèces étudiées. Finalement la présence de coelentérazine dans les gonades suggère également un potentiel transfert maternel des capacités lumineuses à la descendance

New developments with the INSU/Météo VHF radar at CNRM/Toulouse — RASS, FDI and upgraded processing techniques

International audienc