Pineal gland involved in many photoperiodic responses:-initiation of migration- initiation of reproduction- changes in pelage color- molting / growth of winter coat

Photoperiodic initiation of migration limiting flycatchers ability to respond to long term climate change

Pineal gland converts signals of light perception into an endocrine signal

Many hormones in photoperiodic response – melatonin often important

Melatonin synthesis: High during day Low at night

Long photoperiod = increased melatonin = increase in gonadal activity or maintenance of high activity

Short photoperiod = decreased melatonin = decrease in gonadal activity or maintenance of low activity

Steinlechner and Niklowitz (1992)

Djungarian hampster (Siberia/Mongolia)

Syrian hampster (Syria/Turkey)

Critical photoperiod: threshold that divides long-day from short-day response

Critical photoperiod differs by species often due to latitude of range

Photoperiodic responses often less pronounced in equatorial vs northern species

Southern latitudeCritical photoperiod ~ 12.5 hours

Northern latitudeCritical photoperiod ~ 13 hours

Ambient temperature can interact with photoperiod to alter response

Hampsters at room temp (22C) had a critical photoperiod ~ 13 hours Hampsters in cold temp (5C) had a critical photoperiod ~15 hours

2 hour change represents a 4 week shift in seasonal acclimations due to photoperiod

22 °C

5 °C

Djungarian hampster (Winter/Summer pelage)

Steinlechner and Niklowitz (1992)

Conservation implications

Some physiological mechanisms that govern species biology may be maladaptive in the face of rapid climate change

The signal for a hare to shift coat color comes from the pineal gland in the brain that senses changes in daylight length.

Shortening days of autumn trigger the coat color change from brown to white.

Earlier winters and springs may be resulting in hares that change color at the wrong time (white hairs on brown dirt or brown hares on snow)

The Tatra mountain ibex (Capra ibex ibex) in Czechoslovakia had gone extinct

Subsequent reintroduction of ibex from nearby Austria was successful.

However, later supplementation of the Tatra herd with individuals fromTurkey and Sinai resulted in fertile hybrids which rutted in autumn rather than in winter as the native ibex did.