Effect of insecticides (Dimiline WP 25, Torak EC 24 and Gamacide 20) on hydra (Hydra vulgaris Pallas).

Investigations showed that the three insecticides used had the most damaging effect upon hydra immediately after treatment. The tentacles and the hypostome are the parts most often damaged. Inse the affected cells, lesions appear in the intracellular membranes, the nucleus shell and the membranes of the mitochondria, Golgi complex and the endoplasmic reticulum, while the cell membrane is preserved.

Regeneration of hydra damaged by zolone PM insecticide.

The zolone PM (phosalone) insecticide in the suspensions used destroys parts of the hypostome, ruins many buds and budless hydras. In the insecticide suspension a hydra shrinks and assumes the smallest surface. It is due to this that the surface mucous layer thickens and epidermal and gastrodermal cells become highly squeezed together.

Effects of ultraviolet light (2535 A) and dactinomycin upon hydra (Pelmatohydra oligactis).

Hydras exposed to ultraviolet light (2535 A, 12 erg/mm-2/s-2) for 15 minutes suffer a depression immediately, individuals that survived recover quickly and lastingly. Hydras treated with dactinomycin of specific concentrations do not suffer a depression until several days later, do not recover and die eventually. The results are also comparable when hydras are exposed to light and treated with cytostatic of such concentration.

Elimination of zymogen cells and their derivates in Hydra.

Budles and one-budded hydras were exposed to action of antimite (N-methyl-bis-chlorethylamine hydrochloride, Pliva, Zagreb) in 7 mg/150, 7 mg/200 and 7 mg/250 ml concentrations. All these concentrations caused exterior morphological and cytological changes of the hydra body. In the ectodermal layer interstitial cells gradually disappeared, and then followed enidoblasts and enids.

Regeneration of proximal and distal part of hydra body cut in the middle of gastral cavity and treated with dactinomycine.

Hydras were cut in the middle of the gastral part of the body. The part with the hypostome is marked as H, and the one with the foot as P. Both parts were treated with actinomycine D in 0,5 mg : 200 ml water solution.