We demonstrate that the probability of the crayfish, P. clarkii, to tail flip in response to a touch on the dorsal tail fan is dependent on both the size and the behavioral state of the animal. Alterations in the animal's internal physical state, such as when the animal autotomizes its chelipeds, will cause larger-sized animals to tail flip; if they were not autotomized, then no tail flip respo...

Rapid transitions in ecosystem structure, or regime shifts, are a hallmark of alternative stable states (ASS). However, regime shifts can occur even when feedbacks are not strong enough to cause ASS. We investigated the potential for ASS to explain transitions between dominance of an invasive species, rusty crayfish (Orconectes rusticus), and native sunfishes (Lepomis spp.) in northern Wisconsi...

The specific binding of concanavalin A (Con A) to semigranular (SG) and granular (G) cells of the crayfishes Pacifastacus lelliusculus and Astacus astacus was shown by in vitro agglutination of fixed haemocytes and by direct labelling with fluorescein isothiocyanate-conjugated Con A (FITCCon A). When non-fixed cell monolayers from both species of crayf~sh were treated with FITC-Con A, capping o...

Three endemic species of the aquatic-breeding frog genus Leptodactylus are recognized from the West Indies: Leptodactylus albilabris (Puerto Rico and the Virgin Islands), Leptodactylus dominicensis (Hispaniola), and Leptodactylus fallax (Lesser Antilles). DNA sequences were obtained from several mitochondrial genes to resolve taxonomic questions involving these species and to provide insights i...

The biogenic amine serotonin is thought to play an important role in aggression in many species, including man. This paper summarizes experimental approaches which attempt to link this neuromodulator with ®ghting in a cray®sh model for which the complex agonistic behavior is well characterized. Based on a quantitative analysis of ®ghting we demonstrate that the infusion of small amounts of sero...