Aggregative behavior in Subulina octona (Bruguiere) (Mollusca, Subulinidae)

The current study aimed to verify the existence of aggregative behavior in Subulina octona (Bruguiere, 1789) and to obtain behavioral evidence of chemical mediation of this behavior. We Used 150 adult animals allocated in IS boxes with humus (10 animals per box). In each box we placed four identified plastic disks in an equidistant position. These disks worked as shelters for the animals. In experiment 1, 10 animals were put in the middle of each box. After 24, 48, 96, 120, 144, and 168 hours we observed the number of formed aggregations, as well as the position of the aggregates (in each shelter), the number of individual per aggregation and the number of isolated individuals. In order to test the hypothesis of conditioning of disks by chemicals compounds, the experiment 11 was carried out. All the individuals were transferred to other boxes with humus, three new disks and the disk containing the larger aggregate after the 168 hours of the experiment I (denominated conditioned disk). We verified, after 24 and 48 hours, the number of individuals below the conditioned disk. In experiment 1, aggregations were observed in every used box and in every time intervals. In all boxes, there was a significant increase in the number of individuals per aggregation and a reduction in the number of isolated individuals until the end of the experiment (ANOVA, p < 0.005). In experiment 11, after 24 hours, six from IS boxes presented aggregations under the conditioned disk, and after 48 hours, seven boxes presented aggregations under conditioned disk. These were the aggregations with a larger quantity of individuals, which suggests the conditioning of the Used AM disks by some factor, possibly a chemical compound.