We determined the acute toxicity of field‐grade formulations of atrazine, alachlor, and a 50:50 mixture of the chemicals to early and late larval stages of northern leopard frogs (Rana pipiens) and American toads (Bufo americanus). We conducted identical tests with rainbow trout (Onchorhynchus mykiss) and channel catfish (Ictalurus punctatus) to compare their sensitivity as bioindicators. The acute toxicity (96‐h median lethal concentrations [LC50s]) of herbicides to amphibian larvae ranged from 47.6 mg/L for early‐stage R. pipiens exposed to atrazine to 3.3 mg/L for late‐stage B. americanus exposed to alachlor. The toxicity of a 50:50 mixture of atrazine and alachlor after a 96‐h exposure was greater than additive (chemical synergy present) for most species and life stages tested, with 96‐h LC50s as low as 1.5 mg/L for late‐stage B. americanus larvae. Older amphibian larvae appeared to be more sensitive than younger larvae for both species and chemicals tested. Overall, rainbow trout and channel catfish appeared to be less sensitive than amphibian larvae. The 96‐h LC50s ranged from 23.8 mg/L for channel catfish exposed to atrazine to 9.1 mg/L for rainbow trout exposed to alachlor. A noteworthy sublethal effect observed in amphibian larvae exposed to atrazine was edema, probably caused by renal disfunction. Chronic predicted no‐observed‐effect concentrations (PNOECs) for lethality after a 30‐d exposure were estimated from mortality data at 3, 6, 24, 48, 72, and 96 h and found to be approximately 10‐ to 20‐fold lower than 96‐h LC50s. The calculated PNOECs are close enough to concentrations actually found in the environment to warrant concern and further tests. Additional research on environmental concentrations, chronic effects, and the effects of chemical synergy is needed before definitive conclusions can be drawn. Chemical synergy and life‐stage sensitivity should be addressed to properly assess the toxicity of herbicides to nontarget organisms.

Abstract-We determined the acute toxicity of field-grade formulations of atrazine, alachlor, and a 50:50 mixture of the chemicals to early and late larval stages of northern leopard frogs (Rana pipiens) and American toads (Bufo americanus). We conducted identical tests with rainbow trout (Onchorhynchus mykiss) and channel catfish (Ictalurus punctatus) to compare their sensitivity as bioindicators. The acute toxicity (96-h median lethal concentrations [LC50s]) of herbicides to amphibian larvae ranged from 47.6 mg/L for early-stage R. pipiens exposed to atrazine to 3.3 mg/L for late-stage B. americanus exposed to alachlor. The toxicity of a 50:50 mixture of atrazine and alachlor after a 96-h exposure was greater than additive (chemical synergy present) for most species and life stages tested, with 96-h LC50s as low as 1.5 mg/L for late-stage B. americanus larvae. Older amphibian larvae appeared to be more sensitive than younger larvae for both species and chemicals tested. Overall, rainbow trout and channel catfish appeared to be less sensitive than amphibian larvae. The 96-h LC50s ranged from 23.8 mg/L for channel catfish exposed to atrazine to 9.1 mg/L for rainbow trout exposed to alachlor. A noteworthy sublethal effect observed in amphibian larvae exposed to atrazine was edema, probably caused by renal disfunction. Chronic predicted no-observed-effect concentrations (PNOECs) for lethality after a 30-d exposure were estimated from mortality data at 3, 6, 24, 48, 72, and 96 h and found to be approximately 10-to 20-fold lower than 96-h LC50s. The calculated PNOECs are close enough to concentrations actually found in the environment to warrant concern and further tests. Additional research on environmental concentrations, chronic effects, and the effects of chemical synergy is needed before definitive conclusions can be drawn. Chemical synergy and life-stage sensitivity should be addressed to properly assess the toxicity of herbicides to nontarget organisms.

We have studied an autosomal dominant hypohidrotic ectodermal dysplasia in 38 individuals over six generations in one family. Thirty-two affected individuals in four generations are still living. Questionnaire responses were received from 21 of the affected relatives and some of the individuals were examined by one of the authors. Smooth, dry, thin skin is seen in most affected individuals. Nearly all have fine, slow-growing scalp and body hair and all have sparse eyebrows and short eyelashes. Nearly all show a decrease in sweating, with some only sweating under the arms and/or on the palms and soles. All affected individuals lacked some deciduous teeth and some permanent teeth. Some teeth are abnormally shaped. Nail abnormalities are more variable and may occur more frequently with increasing age. No other abnormalities are seen in affected individuals in this family. We reviewed 40 autosomal dominant ectodermal dysplasia syndromes. This family bears some resemblance to a family described by Jorgensen et al. [1987]; however, it appears to represent a disorder that has not been described previously.

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The physiological aspects of sperm-egg interactions have been studied extensively by many investigators (see Metz and Monroy, 1967 for review). These studies include such topics as the effects of egg substances on specificity of attachment, activation of the sperm acrosomal reaction, and release of lytic substances from the acrosome. Many, if not all, of these processes evidently involve INTERACTIONS IN SELECTED DECAPODS (CRUSTACEA) AND LIMULUS