The role of temperature in controlling diel activity in upstream migrant sea lampreys (Petromyzon marinus)

Abstract

This study used controlled laboratory conditions to directly assess the role of temperature in controlling diel activity in sexually immature, upstream migrant sea lampreys ( Petromyzon marinus ). Our results identified three separate temperature-induced changes to the normal nocturnal activity pattern of lampreys: (i) at low temperature (7 °C), lampreys became inactive; (ii) at high temperatures (≥20 °C), the normal nocturnal peak in activity was reduced and lampreys became active during the day; and (iii) rapid increases in temperature (7 or 8 °C over 4 h) stimulated transient daytime activity that subsided once temperature stabilized. In addition, we found evidence that temperature directly influences other aspects of sea lampreys behaviour, specifically light avoidance and rheotaxis. We propose that temperature-induced changes in diel activity represent adaptive behaviour, increasing the probability of lampreys reaching the spawning grounds within the narrow thermal range for successful embryonic development.