Olfactory flow in the sturgeon is externally driven Garwood, Russell J.; Behnsen, Julia; Haysom, Harriet K. ...
Comparative biochemistry and physiology. Part A, Molecular & integrative physiology,
September 2019, 2019-09-00, 20190901, Letnik:
235
Journal Article
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Fluid dynamics plays an important part in olfaction. Using the complementary techniques of dye visualisation and computational fluid dynamics (CFD), we investigated the hydrodynamics of the nasal ...region of the sturgeon Huso dauricus. H. dauricus offers several experimental advantages, including a well-developed, well-supported, radial array (rosette) of visible-by-eye olfactory sensory channels. We represented these features in an anatomically accurate rigid model derived from an X-ray scan of the head of a preserved museum specimen. We validated the results from the CFD simulation by comparing them with data from the dye visualisation experiments. We found that flow through both the nasal chamber and, crucially, the sensory channels could be induced by an external flow (caused by swimming in vivo) at a physiologically relevant Reynolds number. Flow through the nasal chamber arises from the anatomical arrangement of the incurrent and excurrent nostrils, and is assisted by the broad, cartilage-supported, inner wall of the incurrent nostril. Flow through the sensory channels arises when relatively high speed flow passing through the incurrent nostril encounters the circular central support of the olfactory rosette, decelerates, and is dispersed amongst the sensory channels. Vortices within the olfactory flow may assist odorant transport to the sensory surfaces. We conclude that swimming alone is sufficient to drive olfactory flow in H. dauricus, and consider the implications of our results for the three other extant genera of sturgeons (Acipenser, Pseudoscaphirhynchus and Scaphirhynchus), and for other fishes with olfactory rosettes.
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•Investigation of fluid dynamics governing odorant transport in the sturgeon•Swimming alone sufficient to drive olfactory flow•External flow captured very efficiently by sturgeon's nasal anatomy•Impact-based mechanism for dispersing olfactory flow may be similar in other fishes•Flow through the olfactory sensory channels of a fish can be externally induced
Diel vertical migration is a widespread behavioral phenomenon where organisms migrate through the water column and may modify behavior relative to changing environmental conditions based on ...physiological tolerances. Here, we combined a novel suite of biologging technologies to examine the thermal physiology (intramuscular temperature), fine-scale swimming behavior and activity (overall dynamic body acceleration as a proxy for energy expenditure) of bluntnose sixgill sharks (Hexanchus griseus) in response to environmental changes (depth, water temperature, dissolved oxygen) experienced during diel vertical migrations. In the subtropical waters off Hawai'i, sixgill sharks undertook pronounced diel vertical migrations and spent considerable amounts of time in cold (5-7°C), low oxygen conditions (10-25% saturation) during their deeper daytime distribution. Further, sixgill sharks spent the majority of their deeper daytime distribution with intramuscular temperatures warmer than ambient water temperatures, thereby providing them with a significant thermal advantage over non-vertically migrating and smaller-sized prey. Sixgill sharks exhibited relatively high rates of activity during both shallow (night) and deep (day) phases and contrary to our predictions, did not reduce activity levels during their deeper daytime distribution while experiencing low temperature and dissolved oxygen levels. This demonstrates an ability to tolerate the low oxygen conditions occurring within the local oxygen minimum zone. The novel combination of biologging technologies used here enabled innovative in situ deep-sea natural experiments and provided significant insight into the behavioral and physiological ecology of an ecologically important deepwater species.
The Guatemalan Caribbean has a deepwater fishing area close to the shore around the Cayman Trench. This study reports the first record of the bluntnose sixgill shark (Hexanchus griseus) from this ...fishing area. Fishery-independent surveys using longlines at ~430-465 m depth, ~11 km northeast of El Quetzalito fishing village, were conducted in 2022 and 2023. Two bluntnose sixgill sharks were captured during these surveys. The sharks were females with total lengths of 300 and 310 cm, with morphological characteristics consistent with this species. These are the first confirmed records of bluntnose sixgill sharks in the western Caribbean Sea. Expanding coastal fisheries to deeper waters presents an emerging threat to deep-sea chondrichthyans in the region. Therefore, periodic fisheries monitoring is needed to estimate their vulnerability to fishing pressure.
This study reports the first records of cowsharks (Hexanchidae) in the Galápagos Islands, in particular Notorynchus cepedianus and Hexanchus griseus, observed between depths of 210 and 418 m on ...footage from free‐falling autonomous deep‐ocean cameras. These sightings provide new information on the habitat preferences and range distribution for N. cepedianus and the first records of H. griseus in Ecuadorian waters. The findings support the formulation of regional conservation strategies for these large apex predator species and highlight the limited biological knowledge of Galápagos' deep‐water ecosystems.
The vital parameter data for 62 stocks, covering 38 species, collected from the literature, including parameters of age, growth, and reproduction, were log-transformed and analyzed using multivariate ...analyses. Three groups were identified and empirical equations were developed for each to describe the relationships between the predicted finite rates of population increase (λ') and the vital parameters, maximum age (Tmax), age at maturity (Tm), annual fecundity (f/Rc)), size at birth (Lb), size at maturity (Lm), and asymptotic length (L∞). Group (1) included species with slow growth rates (0.034 yr(-1) < k < 0.103 yr(-1)) and extended longevity (26 yr < Tmax < 81 yr), e.g., shortfin mako Isurus oxyrinchus, dusky shark Carcharhinus obscurus, etc.; Group (2) included species with fast growth rates (0.103 yr(-1) < k < 0.358 yr(-1)) and short longevity (9 yr < Tmax < 26 yr), e.g., starspotted smoothhound Mustelus manazo, gray smoothhound M. californicus, etc.; Group (3) included late maturing species (Lm/L∞ ≧ 0.75) with moderate longevity (Tmax < 29 yr), e.g., pelagic thresher Alopias pelagicus, sevengill shark Notorynchus cepedianus. The empirical equation for all data pooled was also developed. The λ' values estimated by these empirical equations showed good agreement with those calculated using conventional demographic analysis. The predictability was further validated by an independent data set of three species. The empirical equations developed in this study not only reduce the uncertainties in estimation but also account for the difference in life history among groups. This method therefore provides an efficient and effective approach to the implementation of precautionary shark management measures.
Broadnose sevengill sharks (Notorynchus cepedianus) show great interest for bait and display a repertoire of movements while engaging with it. A novel back‐thrust mechanism is described in wild ...sevengill sharks by which individuals back up from a negative stimulus while interacting with baited video stations. This mechanism initiates upon head contact with the device that functions as a negative stimulus eliciting a startle escape‐like response. By heavily flipping pectoral fins and curving the body, sharks increase hydrodynamic resistance, backing up from the negative stimulus. Once backed up, sharks performed the common C‐shaped double‐bend escape maneuver described for sharks. Sharks also used the same back‐thrust mechanism as a repositioning maneuver, but not as part of a startle response. The quantification of the turning rate indicated context‐dependent variation in velocity and confirmed that the majority of withdrawals corresponded to slow escape‐like motions. In general, an elongated body and individual flipping control of pectoral fins allowed for great maneuverability and lateral flexure. Sharks exhibited great tolerance to one another during double and triple encounters. The implications for grouping and social hunting of the species are briefly discussed based on past evidence and the movement behavior, gregarious interactions, and body markings observed in the present study. This work highlights the importance of studies in the natural environment and the use of complementary approaches to investigate the broader range of locomotor aspects of different shark species.
A novel back‐thrust mechanism is described in wild sevengill sharks by which individuals back up from negative stimuli while interacting with BRUVS. This mechanism initiates upon head contact with the device that functions as a negative stimulus and elicits a startle response. By heavily flipping pectoral fins and curving the body, sharks increase hydrodynamic resistance, backing up from the device. Once backed up, sharks performed the common C‐shaped double‐bend escape‐like maneuver described for sharks.
With the increasingly imperilled status of shark populations, there is a pressing need to evaluate management solutions. Given the threats posed by fishing, marine reserves (MRs) present a promising ...option.
Ata Whenua (Fiordland) in the South Island of Aotearoa/New Zealand is an ideal location to investigate this phenomenon owing to the presence of several shark species in coastal MRs.
One‐hundred and sixty‐seven baited remote underwater video deployments were made in five MRs. A multi‐model inference approach using generalized linear modelling was used to assess the combined effect of the MRs on two trophic groups of coastal sharks.
Generalized linear modelling was used to assess the effect of protection on, firstly, the presence of broadnose sevengill sharks (Notorynchus cepedianus), while accounting for variations in environmental variables, and secondly, the combined relative abundance of mesopredatory sharks detected (spiny dogfish, Squalus acanthias; school shark, Galeorhinus galeus; and carpet shark, Cephaloscyllium isabellum).
Mesopredators had a higher relative abundance in MRs by a factor of 2.5 and there was a strong significant effect of protection, suggesting that MRs have led to an increase in their abundance or a change in distribution. In contrast, there was no effect of protection detected for sevengill sharks.
It is concluded that the relatively small (<40 km2) MRs sampled do not provide conservation benefits for a large, mobile shark, but that they are potentially large enough to offer protection for mesopredatory sharks with smaller home ranges.
To be effective for shark conservation, we therefore recommend that MRs need to be appropriately sized for the ranging behaviour of the target species for protection.
We do not expect non air-breathing aquatic animals to exhibit positive buoyancy. Sharks, for example, rely on oil-filled livers instead of gas-filled swim bladders to increase their buoyancy, but are ...nonetheless ubiquitously regarded as either negatively or neutrally buoyant. Deep-sea sharks have particularly large, oil-filled livers, and are believed to be neutrally buoyant in their natural habitat, but this has never been confirmed. To empirically determine the buoyancy status of two species of deep-sea sharks (bluntnose sixgill sharks, Hexanchus griseus, and a prickly shark, Echinorhinus cookei) in their natural habitat, we used accelerometer-magnetometer data loggers to measure their swimming performance. Both species of deep-sea sharks showed similar diel vertical migrations: they swam at depths of 200-300 m at night and deeper than 500 m during the day. Ambient water temperature was around 15°C at 200-300 m but below 7°C at depths greater than 500 m. During vertical movements, all deep-sea sharks showed higher swimming efforts during descent than ascent to maintain a given swimming speed, and were able to glide uphill for extended periods (several minutes), indicating that these deep-sea sharks are in fact positively buoyant in their natural habitats. This positive buoyancy may adaptive for stealthy hunting (i.e. upward gliding to surprise prey from underneath) or may facilitate evening upward migrations when muscle temperatures are coolest, and swimming most sluggish, after spending the day in deep, cold water. Positive buoyancy could potentially be widespread in fish conducting daily vertical migration in deep-sea habitats.
Fifty-one fossil shark teeth, including Hexanchiformes, Echinorhiniformes, Squaliformes and Lamniformes, are described from two localities in Nishichirashinai and Omagari formations of the Yezo Group ...in Nakagawa Town, Hokkaido, Japan. They include the first occurrence of Protosqualus from the northwestern Pacific and suggest the onset of the adaptation to deep-water environments of the Squaliformes in this region by early Campanian. Different sedimentary settings of the two localities may have caused different taxonomic compositions. The co-existence of Hexanchiformes and Lamniformes is also known in a contemporaneous Japanese fauna and those of southern high latitudes and suggests effects of paleogeographic settings on the global distribution of Upper Cretaceous neoselachian taxa.
•Cretaceous shark fossils from the understudied North Pacific area were reported.•Shark fossils from Nakagawa include Protosqualus, Xampylodon and Cretalamna spp.•Palaeo-geological settings of the localities suggest yields of deep-sea shark.•Deep-water adaptation of Squaliformes possibly occurred by early Campanian.•Japanese Cretaceous faunas show regionality in neoselachian global distribution.
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