The ipsilateral retinothalamic projection in Xenopus laevis normally first appears at about stage 54, at a time when a number of other changes known to be dependent on a rise in circulating levels of thyroxine begin to occur. We have investigated the role of thyroxine in the development of the ipsilateral retinothalamic projection by studying retinal projections and patterns of retinal histogen...

The acute toxicity of technical-grade glyphosate acid, glyphosate isopropylamine, and three glyphosate formulations was determined for adults of one species and tadpoles of four species of southwestern Australian frogs in 48-h static/renewal tests. The 48-h LC50 values for Roundup(R) Herbicide (MON 2139) tested against tadpoles of Crinia insignifera, Heleioporus eyrei, Limnodynastes dorsalis, a...

We investigated the effects of corticotropin-releasing factor (CRF) and corticosterone (CORT) on foraging and locomotion in Western spadefoot toad (Spea hammondii) tadpoles and juveniles to assess the behavioral functions of these hormones throughout development. We administered intracerebroventricular injections of ovine CRF or CRF receptor antagonist alphahelical CRF((9-41)) to tadpoles and j...

The kinematics of swimming in tadpoles from four species of anurans (Rana catesbeiana Shaw, Rana septentrionalis Baird, Rana clamitans Latreille and Bufo americanus Holbrook) was studied using computerassisted analysis of high speed (^200 frames s") cine" records. 1. Tadpoles exhibit the same positive, linear relationship between tail beat frequency and specific swimming speed commonly reported...

The rapid induction of a defensive morphology by a prey species in face of a predation risk is an intriguing in ecological context; however, the physiological mechanisms that underlie this phenotypic plasticity remain uncertain. Here we investigated the phenotypic changes shown by Rana pirica tadpoles in response to a predation threat by larvae of the salamander Hynobius retardatus. One such re...

This investigation reports the effect of corticosterone on the growth of Bufo melanostictus tadpoles. Test tadpoles of experiment I (T-I), maintained in 1μg/ml solution of corticosterone, were 2.39mm shorter than controls by day 11. Test tadpoles of experiment II (T-II), maintained in 5μg/ml solution were 4.32mm shorter than their counterparts. Growth inhibition was dose related and became sign...

Kin discrimination in cannibalistic tadpoles of the Green Poison Frog, Dendrobates auratus (Anura, Dendrobatidae). Cannibalizing a related individual can reduce the inclusive fitness of the cannibal. Hence, mechanisms that allow a tadpole to recognize and modify its behavior toward kin may reduce the inclusive fitness costs of cannibalism. Alternatively, ecological factors may cause preferentia...

Bullfrog (Rana catesbeiana) tadpoles were exposed to malathion in water in a 28-d static renewal test. The effects of malathion on survival, growth, development, and loss of equilibrium posture were determined. Survival was significantly decreased at malathion concentrations of 2,500 micrograms/L and higher. Development of tadpoles was delayed significantly by malathion exposure as indicated by...

This year we have had both frogspawn and toadspawn in the pond. The tadpoles emerged first and very quickly started to eat the toadspawn. Since the toad tadpoles are poisonous to many creatures it is not clear whether the tadpoles were eating the developing toad tadpoles or just the jelly, but whichever combination they were eating, the carefully roped toadspawn was rapidly destroyed. It is pos...

1. Despite the increasing occurrence of global environmental changes, including increases in ultraviolet-B radiation (UV-B; 280–320 nm), little is known about how factors such as UV-B affect animals physiologically. Amphibians provide a good model for examining physiological effects of UV-B exposure because studies documenting both lethal and sub-lethal effects have been completed on many speci...