page 02 1. The veined squid, Loligo forbesii, is a mollusc species found off the west coast of Scotland. This species undergoes a daily vertical migration in the water, coming up to the surface to feed at night, and diving to deeper depths during the day. Figure 1 shows the anatomical structure of a squid. Figure 1 tail fins eyes mantle head arms and tentacles The relationship between size and age of squid was investigated. The size was determined by measuring the length of the mantle. As the squid migrate up and down in the water, the changes in pressure affect the formation of crystals in the squid balance organs, known as statoliths. These crystals show up as rings that can be counted to show the age of the squid in days. Researchers collected data from squid caught off the west coast of Scotland over a number of weeks. The researchers measured mantle length and counted statolith growth rings for 29 squid. Figure 2 shows age plotted against mantle length. Figure 2 100 120 140 160 180 200 220 240 260 280 300 100 150 200 250 300 mantle length (mm) age (days) 350 400 450