Compression force (N) for first and second breaks of Thiara scabra and Haita acuta snail shells
Description
Compression force (N) for first and second breaks (defined as a sudden 20% drop or more in the measured force) of Thiara scabra and Haita acuta snail shells, using a single-partical compression test.
Files
Steps to reproduce
In the current study, the tested particle is a snail, which is gently placed on the lower contact surface made of alumina 995. The upper punch, also made of alumina 995, is operated by a hydro-pneumatic piston. The upper punch first moves rapidly to a predefined height (typically ~125% of the particle size) without contacting the specimen; then it descends slowly until gentle contact with the snail is detected, avoiding any initial impact. From this point onwards, the punch compresses the particle at a constant compression force rate of 1 N/s until breakage (sudden 20% drop or more in the measured force) occurs. The applied force is measured (with an accuracy of ±0.01% of full scale) by a load cell connected to the lower contact surface, and displacement is simultaneously recorded (with an accuracy of ±5 μm) by using a linear variable differential transformer (LVDT) sensor. The curve displays a typical response in which the force increases with the displacement up to a clear breakage point. The number of snails for each species to be tested was calculated as follows: the median breakage force calculated for the first 5 snails, then for the first 10 snails, and so on, was plotted against the number of measured individuals. The minimum number of snails required for reproducible results was defined as the point at which the median force values converged to stable levels within a ±5% error margin. See also previous literature (Portnikov et al., 2013; Portnikov & Kalman, 2014, 2018). A total of 50 live H. acuta and 70 live Thiara scabra snails of size grade 4-6 mm (graded with a set of sieves and vigorous washing) were tested in a LabVIEW program-controlled compression tester (Portnikov et al., 2013; Portnikov & Kalman, 2018). Each compression test was conducted independently for a first and a second breakage event, with a breakage point identified by a sudden drop of more than 20% in the measured force. The first and second breakage points were measured to investigate whether a predator requires less or similar force to prey on a previously encountered snail. Before testing, all snails were euthanized in ice water. Snails were collected from fishponds in Emek HaMa’ayanot, Northern Israel, namely, from the Tirat Zvi farm (N 32.400784, E 35.530227), the Ein HaNaziv farm (N 32.471151, E 35.507449), and a drainage trench near Kibbutz Shlukhot (N 32.476060, E 35.486404), based on mapping from a previous study (Moscovitz et al., 2024). A uniform shell width of 4-6 mm at the snail widest point in the shell was determined by using a set of sieves, one with holes of 6 mm and the second of 4 mm, thus snails which were trapped between them after rigorous washing were used for the experiment, as previously described (Savaya-Alkalay et al., 2018; Savaya et al., 2020).
Institutions
- Ben-Gurion University of the NegevSouthern District, Beersheba