Greener Synthesis of Pristane by Flow Dehydrative Hydrogenation of Allylic Alcohol Using a Packed-Bed Reactor Charged by Pd/C as a Single Catalyst

Our previous work established a continuous-flow synthesis of pristane, which is a saturated branched alkane obtained from a Basking Shark. The dehydration of an allylic alcohol that is the key to a tetraene was carried out using a packed-bed reactor charged by an acid–silica catalyst (HO-SAS) and flow hydrogenation using molecular hydrogen via a Pd/C catalyst followed. The present work relies on the additional propensity of Pd/C to serve as an acid catalyst, which allows us to perform a flow synthesis of pristane from the aforementioned key allylic alcohol in the presence of molecular hydrogen using Pd/C as a single catalyst, which is applied to both dehydration and hydrogenation. The present one-column-two-reaction-flow system could eliminate the use of an acid catalyst such as HO-SAS and lead to a significant simplification of the production process.

Basking shark sub-surface behaviour revealed by animal-towed cameras

While biologging tags have answered a wealth of ecological questions, the drivers and consequences of movement and activity often remain difficult to ascertain, particularly marine vertebrates which are difficult to observe directly. Basking sharks, the second largest shark species in the world, aggregate in the summer in key foraging sites but despite advances in biologging technologies, little is known about their breeding ecology and sub-surface behaviour. Advances in camera technologies holds potential for filling in these knowledge gaps by providing environmental context and validating behaviours recorded with conventional telemetry. Six basking sharks were tagged at their feeding site in the Sea of Hebrides, Scotland, with towed cameras combined with time-depth recorders and satellite telemetry. Cameras recorded a cumulative 123 hours of video data over an average 64-hour deployment and confirmed the position of the sharks within the water column. Feeding events only occurred within a metre depth and made up ¾ of the time spent swimming near the surface. Sharks maintained similar tail beat frequencies regardless of whether feeding, swimming near the surface or the seabed, where they spent surprisingly up to 88% of daylight hours. This study reported the first complete breaching event and the first sub-surface putative courtship display, with nose-to-tail chasing, parallel swimming as well as the first observation of grouping behaviour near the seabed. Social groups of sharks are thought to be very short term and sporadic, and may play a role in finding breeding partners, particularly in solitary sharks which may use aggregations as an opportunity to breed. In situ observation of basking sharks at their seasonal aggregation site through animal borne cameras revealed unprecedented insight into the social and environmental context of basking shark behaviour which were previously limited to surface observations.

Drivers of Spatial Distributions of Basking Shark (Cetorhinus maximus) in the Southwest Pacific

Basking sharks (Cetorhinus maximus) were widely reported throughout New Zealand waters. Once commonly observed, and sometimes in large numbers, basking sharks are now infrequently reported. Basking shark observations are known to be highly variable across years, and their distribution and occurrence have been shown to be influenced by environmental predictors such as thermal fronts, chl-a concentration, and the abundance of prey (zooplankton). Little is known of basking sharks in the South Pacific and more information on distribution, habitat use, and migratory patterns is required to better understand the species’ regional ecology. Here, we used bootstrapped Habitat Suitability Models [HSM, ensembled from Boosted Regression Tree (BRT) and Random Forest (RF) models] to determine the drivers of basking shark distribution, predict habitat suitability and estimated uncertainty in the South Pacific for the first time. High−resolution environmental (1 km2 grid resolution) and biotic data, including inferred prey species, and all available basking shark records across New Zealand’s Exclusive Economic Zone (EEZ) were included in the ensemble HSMs. The most influential driver of modeled basking shark distribution was vertical flux of particulate organic matter at the seabed, which may indicate higher levels of primary production in the surface ocean and higher prey density in the mesopelagic zone and at the seafloor. The BRT and RF models had good predictive power (AUC and TSS > 0.7) and both models performed similarly with low variability in the model fit metrics. Areas of high basking shark habitat suitability included the east and west coasts of the South Island, Puysegur Ridge, and Auckland Island slope. The outputs produced here could be incorporated into future management framework for assessing threat and conservation needs (e.g., spatially explicit risk assessment) for this regionally protected species, as well as providing guidance for future research efforts (e.g., areas of interest for sampling).

A new species of the enigmatic shark genus Nanocetorhinus (Chondrichthyes) from the Oligocene of Austria with palaeoceanographic implications

Deep-neritic sediments of the Eferding Formation (Egerian, Upper Oligocene) of Upper Austria from the Kamig kaolinite quarry revealed minute teeth of the putatively planktivorous shark genus Nanocetorhinus. This is the oldest unambiguous record of this rarely documented genus, which was known so far only from Miocene deposits of Europe, North America and Japan. Based on previous studies, which showed a positive correlation between sediments of nutrient rich waters and plankton blooms with a majority of ichthyoliths of Keasius and Nanocetorhinus, we argue for a filter-feeding and migratory lifestyle of the latter. Thus, it is supposed that Nanocetorhinus migrated seasonally for foraging, in a similar way to the extant basking shark Cetorhinus maximus. This mode of life and the wide paleogeographic distribution of the open marine genus Nanocetorhinus requires a deep and fully marine connection between the Paratethys and the Proto-Mediterranean Sea during late Oligocene times, which might have been established via the Slovenian Corridor.

« Comment peut-on être cochon ? » : darwinisme et conscience chez Darrieussecq

The confluence of cognitive science and Darwinian theory has produced a wealth of fascinating research in recent decades, often enthusiastically embraced by the humanities, and given rise to the new disciplines of evolutionary psychology and neurophenomenology. Darrieussecq’s interest in human and non-human cognition makes her work a site of exploration for several issues related to these fields of research. Her characters speculate on the inner lives and perceptual worlds of dogs, cats and insects. The narrative focalization of her story will leap unexpectedly from a human consciousness into that of a sea-lion or a basking shark. And, most famously, in Darrieussecq’s debut novel we follow the narrator’s subjectivity as she metamorphoses between human and pig form and states undecidably in-between, during which process, we gradually realize, it is not only her physical form that is shifting but her mentality as well. This article examines how Darrieussecq’s exploration of animal consciousness and its relation to the human not only serves as a metaphor for intersubjectivity and the unknowable mind of the other, but also offers a meditation on the nature of humanity and of its place within an evolutionary spectrum of differently adapted minds.

Assessing the importance of Isle of Man waters for the basking shark Cetorhinus maximus

Satellite tracking of endangered or threatened animals can facilitate informed conservation by revealing priority areas for their protection. Basking sharks Cetorhinus maximus (n = 11) were tagged during the summers of 2013, 2015, 2016 and 2017 in the Isle of Man (IoM; median tracking duration 378 d, range: 89-804 d; median minimum straight-line distance travelled 541 km, range: 170-10406 km). Tracking revealed 3 movement patterns: (1) coastal movements within IoM and Irish waters, (2) summer northward movements to Scotland and (3) international movements to Morocco and Norway. One tagged shark was bycaught and released alive in the Celtic Sea. Basking sharks displayed inter-annual site fidelity to the Irish Sea (n = 3), a Marine Nature Reserve (MNR) in IoM waters (n = 1), and Moroccan waters (n = 1). Core distribution areas (50% kernel density estimation) of 5 satellite tracked sharks in IoM waters were compared with 3902 public sightings between 2005 and 2017, highlighting west and south coast hotspots. Location data gathered from satellite tagging broadly correspond to the current boundaries of MNRs in IoM waters. However, minor modifications of some MNR boundaries would incorporate ~20% more satellite tracking location data from this study, and protective measures for basking sharks in IoM waters could further aid conservation of the species at local, regional and international scales. We also show the first documented movement of a basking shark from the British Isles to Norway, and the longest ever track for a tagged basking shark (2 yr and 2 mo, 804 d).

Negative allometric growth during ontogeny in the large pelagic filter-feeding basking shark

Many pelagic shark species change body and fin shape isometrically or by positive allometry during ontogeny. But some large apex predators such as the white shark Carcharodon carcharias or the tiger shark Galeocerdo cuvier show distinct negative allometry, especially in traits related to feeding (head) or propulsion (caudal fin). In particular, changes in propulsion are attributed to a shift in swimming mode. The more heterocercal caudal fin of younger individuals with its large caudal fin span seemingly aids in hunting small, agile prey. In contrast, the less heterocercal caudal fin with a larger fin area in larger individuals aids a long-distance slow swimming mode. We were interested if negative allometric effects can be observed in a planktivorous shark, the basking shark Cetorhinus maximus, a large species adapted to long-distance slow swimming. To address this question, we compared three size classes, specifically < 260 cm (juveniles), 299–490 cm (subadults), and from adults > 541 cm total length. Comparing literature data, we found negative allometric growth of the head and of the caudal fin, but a more rapid decrease of relative caudal fin size than of relative head length. Hereby, we provide the first evidence for early negative allometric growth of the caudal fin in a large pelagic filter-feeding shark. Our study further demonstrates that ecomorphological approaches may add valuable insight into the life history of animals that are challenging to study in their natural habitat, including large roving sharks such as the basking shark.

Latent power of basking sharks revealed by exceptional breaching events

The fast swimming and associated breaching behaviour of endothermic mackerel sharks is well suited to the capture of agile prey. In contrast, the observed but rarely documented breaching capability of basking sharks is incongruous to their famously languid lifestyle as filter-feeding planktivores. Indeed, by analysing video footage and an animal-instrumented data logger, we found that basking sharks exhibit the same vertical velocity (approx. 5 m s −1 ) during breach events as the famously powerful predatory great white shark. We estimate that an 8-m, 2700-kg basking shark, recorded breaching at 5 m s −1 and accelerating at 0.4 m s −2 , expended mechanical energy at a rate of 5.5 W kg −1 ; a mass-specific energetic cost comparable to that of the great white shark. The energy cost of such a breach is equivalent to around 1/17th of the daily standard metabolic cost for a basking shark, while the ratio is about half this for a great white shark. While breaches by basking sharks must serve a different function to white shark breaches, their similar breaching speeds questions our perception of the physiology of large filter-feeding fish.