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Epidermal lamellae (scutes) of the Texas tortoise, Gopherus berlandieri, from southern Texas (USA) were observed to be in various stages of necrosis, ranging from localized whitish blemishes to complete degradation of the external portion of the scute. Fusarium semitectum was consistently isolated from slivers of infected scute from tortoises. The fungus was not isolated from tortoises exhibiting no lesions. Confocal microscopy confirmed the presence of septate mycelia inside the scutes, and isolates of F. semitectum grown in the laboratory were successfully transferred to non-infected tortoises. Twenty-four tortoises maintained by two rehabilitators in southern Texas exhibited lesions; however, only one of 27 tortoises from Dimmit and Zavala counties was infected.

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Spontaneous mastocytomas studied in 18 axolotls (Ambystoma mexicanum) and six tiger salamanders (Ambystoma tigrinum) were gray-white, uni- to multilobular cutaneous protrusions from 2 mm to 2 cm in diameter. Tumors were moderately cellular unencapsulated masses that usually infiltrated the dermis and hypodermis with the destruction of intervening tissues. Some tumors were invading superficial bundles of the underlying skeletal muscle. Tumors consisted of mitotically active cells derived from a single lineage but showing a range of differentiation. Immature cells had nearly smooth to lightly cleft or folded basophilic nuclei bordered by a band of cytoplasm with few cytoplasmic processes and containing a few small uniform eccentric granules. Mature cells had basophilic nuclei with deep clefts or folds and abundant eosinophilic cytoplasm with multiple long intertwining cytoplasmic extensions packed with metachromatic granules. The axolotls were old individuals from an inbred laboratory colony. The tiger salamanders were wild animals from a single polluted pond. They could have been old and inbred. Both groups were neotenic. These are the first mastocytomas discovered in cold-blooded animals.

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Hexamethylmelamine (HEMLA) is a metabolism-dependent formaldehyde-releasing agent related in structure to hexamethylphosphoramide (HMPA). Both compounds are known to be mutagenic to Drosophila. HMPA, in common with the other formaldehyde-releasing agents studied, is non-mutagenic to Salmonella. The present paper describes the mutagenicity of HEMLA to strain TA100 of Salmonella typhimurium. Activity is dependent upon both the use of a pre-incubation assay protocol and on high concentrations of Aroclor-induced rat liver in the S9 mix. HMPA was inactive under similar conditions of test.

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A number of carcinogenic aromatic amines when activated by liver microsomes from a salamander, Ambystoma tigrinum, are mutagenic for Salmonella tester strains sensitive to frameshift mutagens. However, 2 polycyclic aromatic hydrocarbons (PAH) (benzo[alpha]pyrene (BaP) and perylene) that are rendered mutagenic by mammalian microsomes are not activated by Ambystoma mixed-function oxidases. BaP was chosen for study because it is a well-known environmental carcinogen; perylene, an isomer of BaP, has been implicated as a etiological agent in cutaneous neoplasia in Ambystoma. These results support the observation that amphibians are quite resistant to PAH carcinogenesis and suggest that aromatic amines may be more appropriate model carcinogens.

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Earlier observations that substitution of the aromatic nucleus of an arylamino/nitro carcinogen with either a sulphonic acid substituent or two methyl groups placed ortho to the nitrogen substituent renders the molecule non-carcinogenic have been extended via studies conducted in vitro. 4-Aminobiphenyl-4'-sulphonic acid has been synthesized and found to be non-mutagenic in the Salmonella mutation assay when tested under conditions where 4-aminobiphenyl was mutagenic. It is concluded that this sulphonic acid derivative may prove non-carcinogenic to rodents. In contrast to the non-carcinogenicity and non-mutagenicity reported for 3,3',5,5'-tetramethylbenzidine, 3,5-dimethyl-4-aminobiphenyl is approximately as mutagenic as 4-aminobiphenyl. It is therefore concluded that this material is potentially carcinogenic and that the loss of mutagenic activity observed for tetramethylbenzidine may be a structurally specific rather than a general phenomenon. In contrast, 3,5-dimethyl-4-nitrobiphenyl was much less mutagenic than 4-nitrobiphenyl. 9,9'-Bijulolidyl, a derivative of 3,3',5,5'-tetramethylbenzidine, was also found to be non-mutagenic. The general significance of these findings to the employment of structure-activity relationships in the design of non-mutagenic/non-carcinogenic molecules is discussed.

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A population of facultative neotenous tiger salamanders (A. tigrinum) inhabiting a sewage lagoon at Reese AFB, Hurlwood, Texas, was found to have an exceptionally high rate of spontaneous tissue lesions. The population is composed of an estimated 28,000 large, reproductively mature larvae that are restricted to the lagoon. Only about 17% of the population metamorphoses normally. In contrast, tiger salamanders from uncontaminated lagoons in the same general vicinity metamorphose normally; however, no neoplasms were discovered in larvae sampled from the nonsewage lagoosn. N-nitrosamine analyses of water and tissue samples of larvae were negative. Polycyclic aromatic hydrocarbon analyses revealed traces of benzo[a]pyrene in the sludge; however, perylene, a constituent of jet fuel, was found in high concentration (300 ppb). These results indicate tat preylene, which was previously found not be tumorigenic to mice and rats, should be retested as a possible agent for nonmammalian species.

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Ambystoma tigrinum found in a sewage polluted pond had high levels of aryl hydrocarbon hydroxylase (AHH) activity that decreased to the basal level of control animals after being held several months in clean water. The qualitative formation of benzo(a)pyrene (BP) metabolites by salamander hepatic microsomes was similar to those seen for other species. Inhibition of epoxide hydrase activity did not alter the total metabolite production but did change the ratio of metabolites. A correlation appears to exist between high AHH induction, the presence of polycyclic hydrocarbon pollutants, and the high rate of spontaneous cancer in salamanders.

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Tiger salamanders (Ambystoma tigrinum) inhabiting a sewage sedimentation lagoon become neotenic, and approximately one-third develop neoplastic skin lesions including cancer. Circumstances suggest a chemical etiology for the neoplasms.

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The major site of sorption of zinc-65 in natural, matlike periphyton is on the upper surface of the community. There is a diffusion gradient within the community. Expression of results from short-term spiking experiments should thus be presented on an areal rather than gravimetric basis.

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