Abstract
Fishes from 12 species (a minimum of three fish of each species), representing nine families were examined for ovarian contraction. An ovary from each fish was removed, placed in a muscle bath and assessed for contractions using a force‐displacement transducer. After at least 30 min of observation for spontaneous contractions, acetylcholine (ACh) was added to the muscle bath to assess the ovary’s capacity for contraction. At least one third of the ovaries from each species contracted spontaneously or in response to 10 −5 M ACh. Mean ± s . e . frequencies of spontaneous contractions ranged from 7·5 ± 2·0 h −1 in the Atlantic silverside Menidia menidia to 380·3 ± 101·5 h −1 in the sheepshead minnow Cyprinodon variegatus . Simultaneously tested ovaries from a single white perch Morone americana contracted at rates of 31·4 and 81·9 h −1 . This is consistent with independent generation of the contractile rhythm in the two ovaries. In three species (goldfish Carassius auratus , mummichog Fundulus heteroclitus and white perch), the tunica albuginea was removed from the ovary and found to be capable of independent contraction. This suggests that this membrane contributes to the observed contractions. The presence of ovarian contractions in this varied group of fish species indicates that the contractions play an important role in reproduction.