Analysis of morphogenetic mutants of hydra

Abstract

Non-budding mutants ofChlorohydra viridissima regenerate heads 6 h faster thanHydra attenuata and the number of tentacles per head is higher. The polarity in pieces from the gastric region is the more labile, the smaller the pieces are. In regenerates heads and tentacles form much more frequently than feet, giving rise to bipolar or multiheaded structures. Buds very seldom form under normal conditions, but they occasionally occur in regenerating animals with two cut surfaces.The higher head-forming potential in the mutant is paralleled by a higher head-activator concentration (20-fold in head, 4-fold in body), than inHydra attenuata, which is not accompanied by an equivalent increase in head-inhibitor concentration (1.4-fold in head, 2-fold in body). The foot-activator concentration is slightly reduced (1.3-fold), the foot-inhibitor concentration is higher (1.6-fold) than inH. attenuata. The mutant is extremely insensitive to head activator, relatively insensitive to head inhibitor and foot inhibitor, but sensitive to foot activator.

The polymorphism of Hydra microsatellite sequences provides strain-specific signatures

“…The importance of identifying the various Hydra strains/species relies on the fact that they can exhibit (i) different developmental behaviors, especially the morphogenetic variants that show distinct budding rate or size features in homeostatic context [20][21][22][23], (ii) lower regeneration potential such as the reg-16 strain that was obtained through inbreeding of the Japanese H. magnipapillata strain [24], (iii) abnormal apical patterning such as multiheaded strains [25,26], (iv) specific cellular properties such as the nf-1 strain that contains neither interstitial stem cells nor interstitial derivatives [27] or the sf-1 thermo-sensitive strain that loses its cycling interstitial cells upon transient heat-shock exposure [28]. Importantly, strains that do not show obvious differences at the morphological or cellular levels actually exhibit variable responses to gene silencing upon RNA interference [29], to drug treatment [30][31][32] or to environmental stresses [32].…”

The head and the foot inhibitor from hydra are not dowex artefacts

“…1 were performed during the same period of time by the same group of people in hydra in a gradient from foot to head with maximal concentration in the foot; it does inhibit foot regeneration preferentially and it has no major effect on head formation and/or on head-specific release or differentiation events. (Berking 1974(Berking , 1977(Berking , 1979a(Berking , b, 1983Berking and Gierer 1977;Kemmner and Schaller 1983;Schaller 1976;Schaller et al 1977Schaller et al , 1979Schaller 1976, 1980). From these correlations and from experiments such as those presented in Fig.…”