Differentiation of the sum of all significantly regulated transcripts for each gill and day of Carcinus maenas upon short-term exposure to hypercapnia. For each of the experimental blocks of the short-term hypercapnia experiment (gill7day3, gill7day7, gill9day3 and gill9day7), up- and down- regulated transcripts were counted and represented as bars. Additionally, a matrix was generated for all significantly regulated transcripts (sign test) for each block with 1 = significantly up-regulated, 0 = not significantly regulated, -1 = significantly down-regulated. Statistical comparison of the four experimental blocks was done applying Wilcoxon's matched pairs test on the matrices. No significant difference was found in gill 7 comparing the two sampling points, while gill 9 on day 3 differed significantly compared to gill 9 on day 7 (p < 0.05). Additionally, gill 9 in general differed significantly in comparison to gill 7 on both days (p < 0.05). Different letters a, b, c denote these significant difference.