Distance at which <i>Calanus finmarchicus</i> initiated an escape reaction from the siphon in the dark and light.

<p>Data tested with a Mann-Whitney ranked sum test. U Statistic  = 1230.5 (p = 0.019).</p

Median distance from the siphon at which <i>Calanus finmarchicus</i> initiated an escape reaction in the dark (solid circles) and in the light (open circles).

<p>Lower and upper whiskers represent the 25% and 75% distribution. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039594#pone-0039594-t001" target="_blank">table 1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039594#pone-0039594-t002" target="_blank">2</a> for data and statistics for light and dark treatments, respectively.</p

Average escape speed of <i>Calanus finmarchicus</i> from a siphon flow (± standard error of the mean).

<p>Mean values are significantly different (p = 0.01; n = 66 for the dark and n = 50 in the light).</p

Escape distributions of <i>Calanus finmarchicus</i> from a siphon flow.

<p>Frequency has been normalized to total number of escapes for each treatment; n = 66 for the dark and n = 50 in the light. Distribution were tested on raw data using a Mann-Whitney ranked sum test and found to be significantly different. U Statistic  = 1230.5 (P = 0.019).</p

Escape distance of <i>Calanus finmarchicus</i> from the siphon in the dark and light.

<p>Data tested with a Mann-Whitney ranked sum test. U Statistic  = 1644.5 (p = 0.98).</p

Distance from the siphon at which <i>Calanus finmarchicus</i> initiated an escape reaction in the light as a function of angle.

<p>Data was tested using Kruskal-Wallis One Way Analysis of Variance on Ranks. H = 1.100 with 2 degrees of freedom. (P = 0.577).</p

Hypothetical predatory interaction between a planktivorous fish and their copepod prey.

<p>Shaded region represents the maximum volume of water entrained during a single strike. The dark shaded area represents the region where the fluid mechanical threshold evokes an escape reaction by the copepod in the dark. The light shaded region represents the location where the escape reaction is initiated in the light. In both cases, the distance traveled during the escape is sufficient to remove the copepod from the capture volume.</p

Filming apparatus used to examine the escape reaction of <i>Calanus finmarchicus</i> in response to a suction flow.

<p>The tank volume was 37 L (25×25×60 cm). The total volume viewed using this optical setup was ∼2.5 L surrounding the siphon (10×10×25 cm). Red dot in the center of the animal indicates the data point taken from the video frame just prior to the initiation of the escape reaction. The distance of copepod from the siphon at the initiation of the escape response represents the detection threshold. Once the animal initiated the escape reaction (retracts its antennae), the total distance traveled and the speed of the escape were measured.</p

Daily irradiance of UVB, UVA and PAR provided to <i>Thalassiosira weissflogii</i> cultures used as food for <i>Calanus finmarchicus</i>.

<p>Algal cultures received one of three treatments: PAR-only (PAR), PAR plus ambient UVR levels and PAR plus enhanced UVR (UVR+).</p

The number of cells (left axis) and volume of cells ingested by <i>Calanus finmarchicus</i> feeding on <i>Thalassiosira weissflogii</i>.

<p>Algae were cultured under one of 3 different light treatments: PAR only (PAR; Treatment 1), PAR plus ambient UVR (UV; Treatment 2), or PAR plus enhanced UVR (UV+; Treatment 3). Grazing rates were measured over a 48 h feeding cycle. Ingestion rates were significantly higher in the UV+ treatment. No significant difference was found in the grazing rates between the PAR- and ambient-UV-treated cells. Lower case letters indicate homogeneous groups after the ANOVA and post-hoc test (see methods for details).</p