High temperatures may halve the lifespan of the Japanese flying squid, Todarodes pacificus

Abstract

ABSTRACTThe lifespan of cephalopods is known to be influenced by the environment, with faster growth and earlier spawning induced by higher than normal water temperatures. However, it is unknown if the Ommastrephid squid, Todarodes pacificus, also exhibits such plasticity, because of difficulties in rearing them. In this study, we reared juveniles of T. pacificus obtained from the wild (Wakasa Bay in the southern Sea of Japan) to adulthood at three different temperatures (13°C, 17°C and 20°C) to understand the impact of water temperature on its lifespan. Mantle lengths of these juveniles ranged from 57.2 to 103.0 mm (about 4–5 months after hatching) at the beginning of the experiment. They were fed a diet of anchovy and saury once or twice daily, and the day/night cycle was set to 12 hours each. Males reared at 17°C and 20°C began to show signs of sexual maturation after 20 days, whereas those reared at 13°C began to mature only after 40 days, and mating behaviour was observed after 30 days at 20°C. Females reared at 20°C began to show signs of sexual maturation after 30 days. The mantle length of mature individuals ranged from 113 to 147 mm, a mantle length this low at maturity being rarely observed in the field. These results demonstrate that just as in the case of other cephalopods, the lifespan of T. pacificus is also influenced by the environment, and may be halved under conditions of higher than normal temperatures.