Relationship of age at eye opening to first optokinetic response in deermice (Peromyscus)

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Abstract
The relationship between visual development and age at eyelid separation was studied in three stocks of Peromyscus maniculatus bairdi, two stocks of P.m. gracilis, P. polionotus, and P. eremicus. The maniculatus subspecies had each been selectively bred for early and late age at eye opening. Mice were tested in a transparent chamber suspended within a rotating drum, which was lined with alternating 3/4‐in. black and white vertical stripes. Beginning within 8 hr of eye opening, each mouse was given 5, 15 sec trials daily, until it responded. Criterion of vision was an optokinetic response in 2 of the 5 trials. Of 75 mice tested, only the early eye opening selected line of P. m. bairdi failed to respond on the day of eye opening. The results indicate that Peromyscus can see conspicuous environmental features at the age of eyelid separation. The delayed optokinetic response in the early selected bairdi line, requiring an average of 2.4 additional days of maturation, indicates the genetic independence of eyelid separation and visual development. The same line did not respond significantly earlier than wild type bairdi, indicating that the extra visual experience afforded by early eye opening did not increase the rate of maturation of the system (s) governing the optokinetic response.