687 research outputs found
Lateral Line Analogue Aids Vision in Successful Predator Evasion for the Brief Squid, Lolliguncula Brevis
Cephalopods have visual and mechanoreception systems that may be employed to sense and respond to an approaching predator. While vision presumably plays the dominant role, the importance of the lateral line analogue for predator evasion has not been examined in cephalopods. To test the respective roles of vision and the lateral line analogue, brief squid, Lolliguncula brevis, were observed in the presence of summer flounder, Paralichthys dentatus, under light and dark conditions with their lateral line analogue intact and ablated. Hair cell ablation was achieved through a pharmacological technique used for the first time on a cephalopod. The proportion of predator-prey interactions survived was significantly higher in the light non-ablated and light ablated groups compared with the dark ablated group. The mean number of interactions survived varied across treatment groups with the light non-ablated group having significantly more success than the light ablated, dark non-ablated and dark ablated groups. These findings demonstrate that although vision is the primary sense, the lateral line analogue also contributes to predator evasion in squid
Multiple Sensory Modalities Used by Squid in Successful Predator Evasion Throughout Ontogeny
Squid rely on multiple sensory systems for predator detection. In this study we examine the role of two sensory systems, the lateral line analogue and vision, in successful predator evasion throughout ontogeny. Squid Doryteuthis pealeii and Lolliguncula brevis were recorded using high-speed videography in the presence of natural predators under light and dark conditions with their lateral line analogue intact or ablated via a pharmacological technique. Paralarval squid showed reduced escape responses when ablated; however, no differences were found between light and dark conditions in non-ablated paralarvae, as was previously shown in juveniles and adults, indicating that the lateral line analogue is integral for predator detection early in life. However, vision does play a role in survival because ablated squid in dark conditions had lower levels of survival than all other treatments. Throughout ontogeny, squid oriented themselves anteriorly towards the oncoming predator, maximizing sensory input to the lateral line analogue system and providing better positioning for tail-first escape jetting, the preferred escape mode. Ablated juveniles and adults had lower response times, escape velocities and peak acceleration than non-ablated individuals, indicating that the lateral line analogue enables squid to respond quicker and with more powerful jets to a predator and maximize escape success. Our findings reveal that the lateral line analogue plays a role in predator detection and successful escape response at the earliest life stages, and continues to contribute to successful evasion by aiding visual cues in juvenile and adult squid
Squids Use Multiple Escape Jet Patterns Throughout Ontogeny
Throughout their lives, squids are both predators and prey for a multitude of animals, many of which are at the top of ocean food webs, making them an integral component of the trophic structure of marine ecosystems. The escape jet, which is produced by the rapid expulsion of water from the mantle cavity through a funnel, is central to a cephalopod\u27s ability to avoid predation throughout its life. Although squid undergo morphological and behavioral changes and experience remarkably different Reynolds number regimes throughout their development, little is known about the dynamics and propulsive efficiency of escape jets throughout ontogeny. We examine the hydrodynamics and kinematics of escape jets in squid throughout ontogeny using 2D/3D velocimetry and high-speed videography. All life stages of squid produced two escape jet patterns: (1) escape jet I characterized by short rapid pulses resulting in vortex ring formation and (2) escape jet II characterized by long high-volume jets, often with a leading-edge vortex ring. Paralarvae exhibited higher propulsive efficiency than adult squid during escape jet ejection, and propulsive efficiency was higher for escape jet I than escape jet II in adults. These results indicate that although squid undergo major ecological transitions and morphology changes from paralarvae to adults, all life stages demonstrate flexibility in escape jet responses and produce escape jets of surprisingly high propulsive efficiency
Correction: New Approaches for Assessing Squid Fin Motions: Coupling Proper Orthogonal Decomposition With Volumetric Particle Tracking Velocimetry (doi:10.1242/jeb.176750)
Squid, which swim using a coupled fin/jet system powered by muscular hydrostats, pose unique challenges for the study of locomotion. The high flexibility of the fins and complex flow fields generated by distinct propulsion systems require innovative techniques for locomotive assessment. For this study, we used proper orthogonal decomposition (POD) to decouple components of the fin motions and defocusing digital particle tracking velocimetry (DDPTV) to quantify the resultant 3D flow fields. Kinematic footage and DDPTV data were collected from brief squid, Lolliguncula brevis [3.1ā6.5 cm dorsal mantle length (DML)], swimming freely in a water tunnel at speeds of 0.39ā7.20 DML sā1. Both flap and wave components were present in all fin motions, but the relative importance of the wave components was higher for arms-first swimming than for tail-first swimming and for slower versus higher speed swimming. When prominent wave components were present, more complex interconnected vortex ring wakes were observed, while fin movements dominated by flapping resulted in more spatially separated vortex ring patterns. Although the jet often produced the majority of the thrust for steady rectilinear swimming, our results demonstrated that the fins can contribute more thrust than the jet at times, consistently produce comparable levels of lift to the jet during arms-first swimming, and can boost overall propulsive efficiency. By producing significant drag signatures, the fins can also aid in stabilization and maneuvering. Clearly, fins play multiple roles in squid locomotion, and when coupled with the jet, allow squid to perform a range of swimming behaviors integral to their ecological success
Supplementation of H1N1pdm09 Split Vaccine with Heterologous Tandem Repeat M2e5x Virus-like Particles Confers Improved Cross-Protection in Ferrets
Current inļ¬uenza vaccines induce strain-speciļ¬c immunity to the highly variable hemagglutinin (HA) protein. It is therefore a high priority to develop vaccines that induce broadly cross-protective immunity to different strains of inļ¬uenza. Since inļ¬uenza A M2 proteins are highly conserved among different strains, ļ¬ve tandem repeats of the extracellular peptide of M2 in a membrane-anchored form on virus- like particles (VLPs) have been suggested to be a promising candidate for universal inļ¬uenza vaccine. In this study, ferrets were intramuscularly immunized with 2009 H1N1 split HA vaccine (āSplitā) alone, inļ¬uenza split vaccine supplemented with M2e5x VLP (āSplit+M2e5xā), M2e5x VLP alone (āM2e5xā), or mock immunized. Vaccine efļ¬cacy was measured serologically and by protection against a sero- logically distinct viral challenge. Ferrets immunized with Split+M2e5x induced HA strain speciļ¬c and conserved M2e immunity. Supplementation of M2e5x VLP to split vaccination signiļ¬cantly increased the immunogenicity of split vaccine compared to split alone. The Split+M2e5x ferret group showed evidence of cross-reactive protection, including faster recovery from weight loss, and reduced inļ¬ammation, as inferred from changes in peripheral leukocyte subsets, compared to mock-immunized animals. In addi- tion, ferrets immunized with Split+M2e5x shed lower viral nasal-wash titers than the other groups. Ferrets immunized with M2e5x alone also show some protective effects, while those immunized with split vaccine alone induced no protective effects compared to mock-immunized ferrets. These stud- ies suggest that supplementation of split vaccine with M2e5x-VLP may provide broader and improved cross-protection than split vaccine alone
The Evolution of Patient-Based Outcome Assessment Instruments in Acupuncture Research: Choosing Patient-Based Outcomes
Binary black hole evolutions of approximate puncture initial data
Approximate solutions to the Einstein field equations are a valuable tool to
investigate gravitational phenomena. An important aspect of any approximation
is to investigate and quantify its regime of validity. We present a study that
evaluates the effects that approximate puncture initial data, based on
"skeleton" solutions to the Einstein constraints as proposed by Faye et al.
[PRD 69, 124029 (2004)], have on numerical evolutions. Using data analysis
tools, we assess the effectiveness of these constraint-violating initial data
and show that the matches of waveforms from skeleton data with the
corresponding waveforms from constraint-satisfying initial data are > 0.97 when
the total mass of the binary is > 40M(solar). In addition, we demonstrate that
the differences between the skeleton and the constraint-satisfying initial data
evolutions, and thus waveforms, are due to negative Hamiltonian constraint
violations present in the skeleton initial data located in the vicinity of the
punctures. During the evolution, the skeleton data develops both Hamiltonian
and momentum constraint violations that decay with time, with the binary system
relaxing to a constraint-satisfying solution with black holes of smaller mass
and thus different dynamics
SDSS J094604.90+183541.8: A Gravitationally Lensed Quasar at z=4.8
We report the discovery of a gravitationally lensed quasar identified
serendipitously in the Sloan Digital Sky Survey (SDSS). The object, SDSS
J094604.90+183541.8, was initially targeted for spectroscopy as a luminous red
galaxy, but the SDSS spectrum has the features of both a z=0.388 galaxy and a
z=4.8 quasar. We have obtained additional imaging that resolves the system into
two quasar images separated by 3.06 arcsec and a bright galaxy that is strongly
blended with one of the quasar images. We confirm spectroscopically that the
two quasar images represent a single lensed source at z=4.8 with a total
magnification of 3.2, and we derive a model for the lensing galaxy. This is the
highest redshift lensed quasar currently known. We examine the issues
surrounding the selection of such an unusual object from existing data and
briefly discuss implications for lensed quasar surveys.Comment: AJ accepted, 9 pages, 6 figures, referee suggestions include
An Empirical Characterization of Extended Cool Gas Around Galaxies Using MgII Absorption Features
We report results from a survey of MgII absorbers in the spectra of
background QSOs that are within close angular distances to a foreground galaxy
at z<0.5, using the Magellan Echellette Spectrograph. We have established a
spectroscopic sample of 94 galaxies at a median redshift of = 0.24 in
fields around 70 distant background QSOs (z_QSO>0.6), 71 of which are in an
'isolated' environment with no known companions and located at rho <~ 120 h^-1
kpc from the line of sight of a background QSO. The rest-frame absolute B-band
magnitudes span a range from M_B-5log h=-16.4 to M_B-5log h=-21.4 and
rest-frame B_AB-R_AB colors range from B_AB-R_AB~0 to B_AB-R_AB~1.5. Of these
'isolated' galaxies, we find that 47 have corresponding MgII absorbers in the
spectra of background QSOs and rest-frame absorption equivalent width
W_r(2796)=0.1-2.34 A, and 24 do not give rise to MgII absorption to sensitive
upper limits. Our analysis shows that (1) Wr(2796) declines with increasing
distance from 'isolated' galaxies but shows no clear trend in 'group'
environments; (2) more luminous galaxies possess more extended MgII absorbing
halos with the gaseous radius scaled by B-band luminosity according to
R_gas=75x(L_B/L_B*)^(0.35+/-0.03) h^{-1} kpc; (3) there is little dependence
between the observed absorber strength and galaxy intrinsic colors; and (4)
within R_gas, we find a mean covering fraction of ~70% for absorbers
of Wr(2796)>=0.3 A and ~80% for absorbers of Wr(2796)>=0.1 A. The
lack of correlation between Wr(2796) and galaxy colors suggests a lack of
physical connection between the origin of extended MgII halos and recent star
formation history of the galaxies. Finally, we discuss the total gas mass in
galactic halos as traced by MgII absorbers. We also compare our results with
previous studies.Comment: 20 pages, 13 figures; to appear in the Astrophysical Journal 2010 May
10 issue; a version with higher resolution figures can be found at
http://lambda.uchicago.edu/public/tmp/mage_apj.pd
Think Outside the Color Box: Probabilistic Target Selection and the SDSS-XDQSO Quasar Targeting Catalog
We present the SDSS-XDQSO quasar targeting catalog for efficient flux-based
quasar target selection down to the faint limit of the Sloan Digital Sky Survey
(SDSS) catalog, even at medium redshifts (2.5 <~ z <~ 3) where the stellar
contamination is significant. We build models of the distributions of stars and
quasars in flux space down to the flux limit by applying the
extreme-deconvolution method to estimate the underlying density. We convolve
this density with the flux uncertainties when evaluating the probability that
an object is a quasar. This approach results in a targeting algorithm that is
more principled, more efficient, and faster than other similar methods. We
apply the algorithm to derive low-redshift (z < 2.2), medium-redshift (2.2 <= z
3.5) quasar probabilities for all 160,904,060
point sources with dereddened i-band magnitude between 17.75 and 22.45 mag in
the 14,555 deg^2 of imaging from SDSS Data Release 8. The catalog can be used
to define a uniformly selected and efficient low- or medium-redshift quasar
survey, such as that needed for the SDSS-III's Baryon Oscillation Spectroscopic
Survey project. We show that the XDQSO technique performs as well as the
current best photometric quasar-selection technique at low redshift, and
outperforms all other flux-based methods for selecting the medium-redshift
quasars of our primary interest. We make code to reproduce the XDQSO quasar
target selection publicly available
- ā¦