Fig. 8
In vivo injection of asterotocin triggers cardiac stomach eversion in A. rubens. a Dose-dependent effect of asterotocin in inducing cardiac stomach eversion. The graph shows the percentage of animals (n = 5 per group) that exhibit cardiac stomach eversion when injected with 10 μl asterotocin at concentrations ranging from 10−6 M to 10−3 M, by comparison with 10 μl of the starfish neuropeptide S2 (10−3 M) or 10 μl of water. Stomach eversion occurred in 100%, 100% and 80% of the animals injected with 10−5 M, 10−4 M and 10−3 M asterotocin, respectively, but stomach eversion was not observed in any of the animals injected with 10−6 M asterotocin, 10−3 M S2 or water. b Temporal dynamics of asterotocin-induced (10 μl of 10−3 M) cardiac stomach eversion. The graph shows mean area (± SEM; n = 13) of the cardiac stomach everted expressed as the percentage of the area of the central disc region at 30-s intervals over a 10-min period following injection of asterotocin. c Images from video recordings of the experiment in b showing a representative water-injected (control) starfish (i–iii) and a representative asterotocin-injected starfish (iv–vi) at 0 min (immediately after injection), after 5 min and after 10 min. The area of the cardiac stomach everted is shown with a dashed line in v and vi. The representative video recordings used to generate the images in c are in Additional file 7