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1 II L~ 20 BIOLOGICAL REPORT 85(1.23) resistant to 65 mg KCN/L at low temperatures (13° C) than were seedlings from cold-susceptible cultivars (25° C), as judged by respiratory activity of mitochondria (Van De Venter 1985). Results suggest that cyanide-resistant respiration may play a role in cold resistance in maize seedlings, al- though more evidence is needed to demonstrate that cold-resistant plants actually use their greater potential for alternative respiration at ]ow temperatures (Van De Venter 1985). The c}•anogenic system comprising cyano- genic glycosides, cyanohydrins, betaglucosidases, and nitrile ]yases is widespread in plants, but also occurs in several species of arthropods, including the tiger beetle (Megacephala oirginica), leaf bee- tle (Paropsis atomaria ), zygaenid moths, and cer- tain butterflies (Nahrstedt 1988). In Zygaeea trifolii, cyanide compounds seem to function as protection against predators (Nahrstedt 1988). De- fensive secretions of cyanide have also been re- ported in polydesmid millipedes, and these organisms seem to be more tolerant than other species when placed in killing jars containing HCN (Towill et al. 1978). In a millipede (Aphelaria sp.), cyanide is generated in atwo-compartment organ by hydrolysis of mandelonitrile; cyanide genera- tion occurs outside the gland when the components ofthe two compartments are mixed duringejection (Towill et al. 1978). Highly toxic substances, such as c}•anides, are sometimes feeding cues and stimulants for special- ized insects. For example, instar larvae of the southern armyworm (Spodoptera erid¢nia) strongly prefer cyanogenic foods, such as foliage of the lima bean, a plant with comparatively elevated cyanide content-up to 31 mg/kg in some varie- ties-in the form of linamurin (Brattsten et al. 1963). Feeding was stimulated in southern ar- myworms at dietary levels up to 508 mg KCN/kg (208 mg HCN/kg) for first to fourth instar larval stages, and between 1,000 and 10,000 mg IiCN/kg diet for fifth and sixth instar larvae (Brattsten et -al. 1983). Sixth instar larvae preexposed to diets containing 5,000 mg KCN/kg showed no adverse affects at dietary levels of 10,000 mg KCN/kg; how- ever, previously unexposed larvae showed revers- ible signs of poisoning at 10,000 mg/l:g diet, including complete inhibition of oviposition and 8390 reduction in adult emergence (Brattsten et al. 1983). Experimental studies with southern ar- myworm larvae and thiocyanate~ne of the in t~vo cyanide metabolites-showed that 5,000 mg thioc}•anate per kilogram diet reduced pupation by 779e, completely inhibited oviposition, and re- duced adult emergence by 8090 (Brattsten et al. 1983), strongly suggesting that thiocyanate poi- soning isthe primary effect of high dietary cyanide levels in southern arm}tivorms. Resistant species, such as southern ar- myworms, require injected doses up to 800 mg KCN/kg BW (332 mg HCN/kg BW) or diets of 3,600 mg KCN/kg for 5090 mortalit}• (Brattsten et al. 1983), but data are scarce for other terrestrial invertebrates. Exposure to 8 mg HCN/L air inhib- its respiration in the granary weevil (Sitophilus granaries) within 15 min and ki115 509n in 4 h; some weevils recover after cessation of 4-h expo- sure (Towill et al. 1978). Aqu¢tic Organr:sms Numerous accidental spills of sodium cyanide or potassium cyanide into rivers ands streams have resulted in massive kills of fishes, amphibians, aquatic insects, and aquatic vegetation; sources of poisonings were storage reservoirs o(con centrated solutions, overturned rail tank cars, or discharge of substances generating Tree HCN in the water from hydrolysis or decomposition (Leduc 1984). Data on the recovery of poisoned ecosystems are scarce. In one case, a large amount gfc}•anide-con- tainingslag entered a stream from the reservoir of a Japanese gold mine as a result of An earthquake (Yasuno et al. 1981). The slag covered the streambed for about 10 km from the point of rup- ture, killing all stream biota; cyanide was detected in the water column for only 3 days after the spill. Within 1 month flora w•as established on the silt covering the above-water stones, but there was lit- tle underwater growth. After 6-7 months, popula- tions of fish, algae, and invertebrates had recovered, although species compo6ition of algae was altered (Yasuno et al. 1981). Fish were the most sensitive Aquatic organ- isms tested under controlled conditions. Signifi- cant adverse nonlethal effects, including reduced swimming performance and inhibited reproduc- tion, were observed in the range of 5.0-7.2 µg free cyanide per liter; deaths were recorded for most species between 20 and 76 µg/L (Table 3). Among invertebrates, adverse nonlethal effects were documented between 18 and 43 µg/I„ and lethal ef- fects between 30 and 100 µg/I~although some deaths were recorded in the range 3-7 µg/L for the amphipod Gammarua pulcx (Table 3). Algae and macrophytes were comparatively tolerant; adverse effects were reported at >160 µg free cyanide per liter (Table 3).