Hormonal control of apolysis in barnacle mantle tissue epidermis, in vitro

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Abstract
Ecdysterone (5–20 μg/ml) stimulated apolysis in inner mantle tissue explants of the barnacle, Balanus amphitrite, maintained under in vitro conditions. Apolysis was noticeable after 12 to 15 hours while complete apolysis was reached by 24 hours. Enlargement of the epidermal cells was also observed in ecdysterone‐stimulated tissues. Ecdysone (10–20 μg/ml) was equally as effective as ecdysterone in stimulating apolysis. In some tissues, which had been cultured with 20 μg/ml ecdysterone for 24 hours, new cuticle formation had occurred following apolysis. The initiation of apolysis by ecdysterone was dependent on RNA and protein synthesis, as indicated by the inhibition of ecdysterone‐promoted apolysis by actinomycin D and cycloheximide. Aqueous extracts of shrimp eyestalks (MIH) (10 es eq/ml), either as a crude extract, or as a low molecular weight fraction from a Sephadex G‐25 column, were active in repressing the apolysis‐stimulating action of ecdysterone. The MIH activity could be overridden by increased levels of ecdysterone. Protease treatment of the MIH from crude and partially purified fractions abolished the inhibitory activity. Molt‐inhibiting hormone did not bind 3H‐ecdysterone. The results demonstrate that the early premolt integumental activities are under the control of ecdysterone and molt‐inhibiting hormone.