Venom Variation during Prey Capture by the Cone Snail, <i>Conus textile</i>

<div><p>Observations of the mollusc-hunting cone snail <i>Conus textile</i> during feeding reveal that prey are often stung multiple times in succession. While studies on the venom peptides injected by fish-hunting cone snails have become common, these approaches have not been widely applied to the analysis of the injected venoms from mollusc-hunters. We have successfully obtained multiple injected venom samples from <i>C. textile</i> individuals, allowing us to investigate venom compositional variation during prey capture. Our studies indicate that <i>C. textile</i> individuals alter the composition of prey-injected venom peptides during single feeding events. The qualitative results obtained by MALDI-ToF mass spectrometry are mirrored by quantitative changes in venom composition observed by reverse-phase high performance liquid chromatography. While it is unclear why mollusc-hunting cone snails inject prey multiple times prior to engulfment, our study establishes for the first time a link between this behavior and compositional changes of the venom during prey capture. Changes in venom composition during hunting may represent a multi-step strategy utilized by these venomous animals to slow and incapacitate prey prior to engulfment.</p></div

Mass spectra of the 1^st, 2^nd, and 3^rd injections from <i>C. textile i</i> for two prey capture events.

<p>In both sets, venom peptide variation was observed in subsequent injections and increased in complexity. Comparisons between the two prey capture events revealed variation between Sets 1 and 2 within the same individual (<i>i</i>). Sets 1 and 2 were collected 53 days apart. * match made to calculated average mass from sequence data as described in the methods section. ♦ mass similar to a peptide mass observed in a previous study [29].</p

Analysis of intraspecific variation in 1^st injections from <i>C. textile</i>.

<p>(A) MALDI-ToF fingerprinting of 1^st injections from <i>C. textile i-iii</i> reveal a common profile of venom peptides marked by instances of variation between individuals. (B) Quantitative differences in venom composition shown by RP-HPLC. Chromatograms indicate more dramatic variation in quantitative differences between <i>C. textile</i> specimens. Peaks common to all three specimens are marked with asterisks. Chromatograms were normalized to maximum peak height.</p

Comparison of injected venom samples from separate feeding events in <i>C. textile</i>.

<p>(A) Spectra from two separate prey capture events 243 days apart, including a 4^th injection from <i>C. textile</i> individual <i>ii.</i> (B) Corresponding RP-HPLC chromatograms illustrate quantitative differences observed within single prey capture events and between separate prey capture events in <i>C. textile ii.</i> Refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098991#pone-0098991-g002" target="_blank">figure 2</a> for symbol legend. Absorbance monitored at 214 nm. Chromatograms were normalized to maximum peak height.</p

RP-HPLC chromatograms of 1^st and 3^rd injections from <i>C. textile i</i>.

<p>Quantitative differences were observed after multiple injections during a single prey capture event. Upper trace 1^st injection, lower trace 3^rd injection. Refer to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098991#pone-0098991-g002" target="_blank">figure 2</a> for symbol legend. Absorbance monitored at 214 nm. Chromatograms were normalized to the threshold peak (retention time 19.9 min.) utilized for the analysis presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0098991#pone.0098991.s002" target="_blank">table S1</a>.</p