Substrate type and palaeodepth do not affect the Middle Jurassic taxonomic diversity of crinoids

Crinoids are largely considered as good indicators for determining environmental conditions. They are robust proxies for inferring changes in salinity and sedimentation rate and for inferring substrate type. Some crinoid groups (e.g., certain comatulids, cyrtocrinids, millericrinids) have a depth preference, thus, making them useful for palaeodepth estimation. The hypotheses that crinoid distribution is substrate-dependent (rock type) or palaeodepth-dependent is tested here based on (a) archival Bathonian-Callovian (Middle Jurassic) crinoid occurrences from Poland and (b) newer finds from five boreholes from eastern Poland. Qualitative data suggests that isocrinids and cyclocrinids occur in both carbonate and siliciclastic rocks. The cyrtocrinids and roveacrinids occur within carbonate rocks, whereas the comatulids are exclusive to siliciclastics. In terms of palaeodepth, most crinoid groups dominate in shallow environments with the sole exception of cyrtocrinids, that are ubiquitous and occur in both shallow (near shore and shallow marine) and slightly deeper (deeper sublittoral to open shelf) settings. The occurrences of the cosmopolitan taxa, Chariocrinus andreae and Balanocrinus subteres (isocrinids), is independent of both substrate type and palaeodepth. Quantitative analyses (Analysis Of Variance; ANOVA) based on substrate type, i.e., substrate-dependency (claystones, sandstones and limestones), and palaeodepth i.e., palaeodepth-dependency (near shore, shallow-marine, mid-ramp and offshore), corroborate qualitative results. Statistical analysis suggest that the distribution of crinoids shows a strong substrate-dependency but not for palaeodepth, although very weak significance (low p value) is noted for near shore and shallow marine settings and crinoid distribution.

Making the best of lousy circumstances: the impact of salmon louse Lepeophtheirus salmonis on depth preference of sea trout Salmo trutta

Sea trout are known for seeking out sources of freshwater to rid themselves of salmon lice. However, the effect of natural haloclines in fjords on parasite dynamics is not well understood. We tagged 48 naturally infested wild sea trout with acoustic depth sensors. The fish were kept inside a small net-pen (4 × 4 × 5 m), 12 at a time, in western Norway during 4 separate time periods in spring 2017. The sea trout were relatively highly infested with sea lice (prevalence: 100%, mean ± SD: 68 ± 58 lice fish-1), and a relatively large proportion of the individuals did not survive the trials (25% mortality). The results show that temperature and light were the 2 most important factors explaining the vertical behaviour of the surviving trout. Mobile lice also had a significant effect on depth distribution, where fish with higher abundances of lice were observed at shallower depths. During the 7 d periods in the net-pen, total sea louse abundance decreased from a mean of 68 to 35 fish-1. Surface salinity explained this reduction better than the experienced salinity of the individual fish, suggesting that short-time exposure to very low salinities, rather than long-term exposure to moderate salinities, is the driving force behind the effect of haloclines on reduction in sea lice numbers.

Differences in stress reactivity between zebrafish with alternative stress coping styles

Animals experience stress in a variety of contexts and the behavioural and neuroendocrine responses to stress can vary among conspecifics. The responses across stressors often covary within an individual and are consistently different between individuals, which represent distinct stress coping styles (e.g. proactive and reactive). While studies have identified differences in peak glucocorticoid levels, less is known about how cortisol levels differ between stress coping styles at other time points of the glucocorticoid stress response. Here we quantified whole-body cortisol levels and stress-related behaviours (e.g. depth preference, movement) at time points representing the rise and recovery periods of the stress response in zebrafish lines selectively bred to display the proactive and reactive coping style. We found that cortisol levels and stress behaviours are significantly different between the lines, sexes and time points. Further, individuals from the reactive line showed significantly higher cortisol levels during the rising phase of the stress response compared with those from the proactive line. We also observed a significant correlation between individual variation of cortisol levels and depth preference but only in the reactive line. Our results show that differences in cortisol levels between the alternative stress coping styles extend to the rising phase of the endocrine stress response and that cortisol levels may explain variation in depth preferences in the reactive line. Differences in the timing and duration of cortisol levels may influence immediate behavioural displays and longer lasting neuromolecular mechanisms that modulate future responses.

A preliminary study on the distribution of spiny lobster (Panulirus spp.) in Labuan Island, Malaysia

Limited info regarding on the global distribution and fisheries data on the spiny lobster Panulirus spp. had placed the IUCN redlist in a dilemmatic position in determining the concrete status for proper conservation. The present survey was carried out in the western region of the main island which consists of seven random stations along the west coast of Labuan during day dive. An extreme low density of the spiny lobsters from the genus Panulirus was determined throughout the present study. Only four individuals of two spiny lobsters species were recorded. Two individuals of P. versicolor were observed in station 2 while the other two (P. ornatus) were spotted in station 4. Low numbers of the Panulirus spp. were spotted during the present preliminary survey was probably due to day dive sampling. Spiny lobster from the genus Panulirus tend to have a wide range of depth preference. Two adults P. versicolor were spotted in least turbid environment. In the previous studies, Panulirus spp. such as P. homarus, P. ornatus, and P. polyphagus tend to prefer slightly turbid environment. The results of the present preliminary daytime survey indicated only two species of Panulirus spp. recorded with two individual numbers per species in Labuan coastal waters. However, due to the little numbers of catchment during the preliminary survey, further studies need to be carried out to provide more concrete evidences on the depth preference of Panulirus spp. in Malaysian waters.

Diel Vertical Migration of Aquatic Crustaceans—Adaptive Role, Underlying Mechanisms, and Ecosystem Consequences

The phenomenon of diel vertical migration (DVM) of planktonic crustaceans, recognized by biologists for at least 2 centuries, is a special case of habitat selection behavior by pelagic animals, with their depth preference changing over a diel cycle in a way that prevents encounters with visually oriented predators (mostly fish). Migrating populations usually move toward cold, dark deep-water strata deprived of algal food when there is sufficient ambient light and move back to food-rich and warm surface waters after dusk. DVM has been recognized in pelagic representatives of all aquatic phyla of the animal kingdom and is considered the most massive diel biomass displacement on Earth. DVM can be observed in nearly all lentic freshwater and marine environments. As zooplankton occupy the central position in pelagic food webs, their massive migrations dramatically affect ecological functioning of offshore biota, particularly the efficiency of primary production utilization, energy flow, and biogeochemical pathways of essential nutrients such as carbon fluxes. The phenomenon of DVM is perhaps the most suitable for quantitative description and the major environmental factors underlying the fitness consequences of DVM, including vertical gradients of light intensity (predation risk), temperature related metabolic rates, food concentration (growth and fecundity), and others, are easy to monitor track in the field and to manipulate in laboratory systems. DVM, as inducible behavior, can be experimentally manipulated, both in the field and in the laboratory, which, in turn, makes it possible to design experiments convenient for testing specific hypotheses on various proximate and ultimate factors underlying this behavior. These characteristics make DVM suitable for investigating the evolution of animal behavior, its adaptive value, and ecosystem consequences. In the fondest memory of our friend Konrad Ciechomski with whom we made, years ago, our first steps into the world of plankton migrations.

Protecting Privacy in Shared Photos via Adversarial Examples Based Stealth

Online image sharing in social platforms can lead to undesired privacy disclosure. For example, some enterprises may detect these large volumes of uploaded images to do users’ in-depth preference analysis for commercial purposes. And their technology might be today’s most powerful learning model, deep neural network (DNN). To just elude these automatic DNN detectors without affecting visual quality of human eyes, we design and implement a novel Stealth algorithm, which makes the automatic detector blind to the existence of objects in an image, by crafting a kind of adversarial examples. It is just like all objects disappear after wearing an “invisible cloak” from the view of the detector. Then we evaluate the effectiveness of Stealth algorithm through our newly defined measurement, named privacy insurance. The results indicate that our scheme has considerable success rate to guarantee privacy compared with other methods, such as mosaic, blur, and noise. Better still, Stealth algorithm has the smallest impact on image visual quality. Meanwhile, we set a user adjustable parameter called cloak thickness for regulating the perturbation intensity. Furthermore, we find that the processed images have transferability property; that is, the adversarial images generated for one particular DNN will influence the others as well.

Ecological and morphological traits predict depth-generalist fishes on coral reefs

Ecological communities that occupy similar habitats may exhibit functional convergence despite significant geographical distances and taxonomic dissimilarity. On coral reefs, steep gradients in key environmental variables (e.g. light and wave energy) restrict some species to shallow depths. We show that depth-generalist reef fishes are correlated with two species-level traits: caudal fin aspect ratio and diet. Fishes with high aspect ratio (lunate) caudal fins produce weaker vortices in the water column while swimming, and we propose that ‘silent swimming’ reduces the likelihood of detection and provides an advantage on deeper reefs with lower light irradiance and water motion. Significant differences in depth preference among trophic guilds reflect variations in the availability of different food sources along a depth gradient. The significance of these two traits across three geographically and taxonomically distinct assemblages suggests that deep-water habitats exert a strong environmental filter on coral reef-fish assemblages.