Forty-four species of insects were assayed for the presence of rhodanese, an enzyme generally considered to be responsible for the detoxification of cyanide. Rhodanese was found to be widely distributed in both adults and larvae and was not restricted to those species which encounter exogenous cyanide through feeding on cyanogenic plants. These results indicate that cyanide detoxification is unlikely to be the primary role for rhodanese in insects.

Spermatozoa of the freeze-tolerant wood frog (Rana sylvatica) were used to develop a general protocol for the frozen storage of amphibian spermatozoa. Tolerance of spermatozoa to cryoprotective agents and freezing in suspension (Ϫ80°C) was determined from rates of sperm lysis and dual-fluorochrome vital dye assays. We tested the efficacy of four cryoprotectants (Me 2 SO, methanol, glycerol, and ethylene glycol), two supplements (fetal bovine serum or glutathione), and combinations of these cryoprotectants and supplements. Me 2 SO and fetal bovine serum were the most effective cryoprotectant and supplement, respectively, in reducing sperm lysis. Vital dye assays showed that viability was greatest for spermatozoa treated with both Me 2 SO and fetal bovine serum. Thus, this combination was used to cryopreserve spermatozoa from the freeze-intolerant anurans, Rana pipiens and Bufo americanus. Recovery of viable spermatozoa was significantly greater for R. sylvatica (mean Ϯ SE ϭ 81.2 Ϯ 9.6%) than for R. pipiens (59.0 Ϯ 2.8%) and B. americanus (47.8 Ϯ 4.1%), perhaps owing to inherent factors promoting its freeze tolerance. Nonetheless, our results support the feasibility of using gamete cryopreservation techniques in programs aimed at the captive propagation of amphibians.

SUMMARYThe L. corniculatus populations at Porthdafarch are polymorphic for the characters of leaf cyanogenesis, petal cyanogenesis and keel petal colour. Plants with cyanogenic leaves and petals occur less frequently on the sea cliffs than inland and previous studies have obtained circumstantial evidence of a link between the dine in leaf cyanogenesis and the distribution of selectively grazing molluscs.Counts of leaf and petal damage have confirmed that plants on the cliffs are grazed less heavily than those growing inland and have demonstrated that individuals with acyanogenic leaves or petals are liable to be chewed more heavily than their cyanogenic neighbours. Most of the damage was attributable to feeding by molluscs and it is concluded that herbivorous insects have only a minor role in the maintenance of the dines.

Using individual plants of Lotus corniculatus as the focus of 1 m2 sampling units the plant species associated with L. corniculatus of known phenotype for the colour of their keel petals have been recorded in the chalk quarry at Wharram, North Yorkshire. Multivariate analyses revealed that there was a negative association between the frequency of dark-keeled plants and the percentage of bare ground within each sampling unit and almost no association with any particular plant species. Thus dark-keeled plants were commoner than the light-keeled form in the denser, more mature grassland vegetation. An increase in the frequency of dark-keeled plants in the more mature vegetation was observed between 1980 and 1984. This was not associated with any selective damage by herbivores to petals, buds, pods or leaves nor were there any differences between the morphs for infestation by seed herbivores. While there was more damage to pods in the areas with less mature vegetation there was no evidence of any differences between the morphs in the production of good, viable seed.

No abstract