The climate-induced changes in the life history of the common cuttlefish in the English Channel

The population of common cuttlefish Sepia officinalis in the English Channel recently developed two life cycles: annual (spawning 1 y.o.) and biennial (spawning 2 y.o.) instead of the biennial strategy known before, associated with increasing environmental temperatures in recent decades because of climate changes. Both groups differ in the size of mature animals (110–196 mm mantle length vs. 140–262 mm) and the number of chambers in the cuttlebone (60–97 in annual vs. 93–152 in biennial). The annual group represented some 15%–20% of the population, and the proportion of early spawners increased during the reproductive period, from 3%–5% in February/March to 50%–70% in June/July. Among spawning cuttlefish males predominated as ~2:1. Such environmentally driven changes in historical ecology as exemplified by the cuttlefish might be a critical link in the adaptation of the cephalopod life cycles to changing ecosystems.