ONTOGENIC VARIATION IN TOXICITY OF TADPOLES OF THE INTRODUCED TOAD BUFO-MARINUS TO NATIVE-AUSTRALIAN AQUATIC INVERTEBRATE PREDATORS

This study investigated. ontogenetic variation in toxicity of tadpoles of the introduced tod Bufo marinus to three species of native Austral ian aquatic invertebrate predators. Crayfish (Cherax quadricarinatus) and dytiscid beetles (Hydaticus vittatus) consumed. early mid, and lat e developmental stages of larval Bufo without apparent ill effect. Bel ostomatids (Lethocerus insulanus) also preyed upon early developmental stages of Bufo without apparent ill effect, but they experienced sign ificant mortality after preying upon mid and late developmental stages of these tadpoles. There was intraspecific variation in the toxic eff ects of mid and late developmental stages of tadpoles on L. insulanus: consumption of these stages was fatal to some individuals but not to others. The observed inter- and intraspecific variation in tonicity wa s not related to the number of tadpoles consumed. Such variability may reflect variation in toxicity among individual tadpoles, or variation in susceptibility to toxins of Bufo within and among predatory specie s. The results demonstrate that the toxicity of larval B, marinus incr eases ontogenetically However, not all native aquatic invertebrate pre dators are adversely affected by this increase in toxicity.