VISUAL PIGMENT CHANGES IN JUVENILE KOKANEE SALMON IN RESPONSE TO THYROID HORMONES

Tetraiodothyronine (T4) or triiodothyronine (T3) injected intraperitioneally into juvenile kokanee (landlocked sockeye salmon), Oncorhynchus nerka, results in a marked increase in the percentage of the retinene2 based visual pigment when compared to sham injected controls. Controls have predominately retinine1 based visual pigment. Doses of 100 μg of T4 cause nearly a complete conversion from retinene1 to retinene2 visual pigment i.e. from VP5031 to VP5272. These results are contrary to what has been reported when thyroid hormone is injected into bullfrog tadpoles. Tadpoles have shown an increase in the amount of vitamin A1 and presumably of the retinene1 visual pigment when injected with thyroid hormone. The possible implications of the results are discussed in relation to visual pigment conversions that occur in a number of paired pigment species. © 1969.