Sexually Mature Hydra

The left photo shows a living hydra with at least 15 mature gonads. Most of the gonads in mid-body and basal positions are probably ovaries; some may contain a fertilized egg or developing embryo. Some gonads nearest the tentacles may be testes. The right photo shows a close-up of the same specimen which is from a lab-reared culture of hydra that is maintained year-round and fed with living cladocerans (daphnids). In a fully extended state, tentacle lengths in some of these specimens exceeds 6 cm.