Trimethylamine induces migration of waterfleas

Abstract

diameter) per treatment. The tubes were then placed in a water bath with a temperature gradient from top to bottom of 20 to 10 °C. We used a spectrophometric assay procedure 10 to establish the TMA concentration in 10 litres of the medium that had previously contained four fish (ides, Leuciscus idus, 10 cm long), and recorded the resulting vertical migration behaviour of daphnids exposed to this medium. TMA concentration in this 'fish' water was between 10 and 25 ȖM.We found that even low concentrations of TMA induce Daphnia to migrate to deeper waters during the day in our test system. At night, they migrate back to the surface when exposed to small amounts of TMA, and stay near the bottom when TMA levels are high (more than 100 ȖM). When the lowest TMA concentration that induces vertical migration is compared with the activity in the fish water, it is clear that the reaction of Daphnia to fish water is stronger than just to TMA alone. This indicates that, although TMA is an active component of the 'fish factor', it is likely to be part of a cocktail of substances that deter Daphnia. The other substances probably help to reduce the chemical threshold that induces migration. It is not clear whether the TMA concentrations used in this study represent realistic values for aquatic systems, as we could find no published details of TMA concentrations in aquatic systems.It has been shown 9 that the fish kairomone is broken down by bacteria. We therefore compared the average day depth of daphnids exposed to 75 ȖM TMA in autoclaved water, and with the antibiotic ampicillin added and the TMA dissolved in non-autoclaved lake water. The migration activity of the Daphnia in non-sterile water slowly decreased over time (Fig. 2). After 72 hours, the average day depth of the animals in non-sterile conditions was no longer significantly different from the average day depth of animals in sterile control medium.To investigate whether simply adding any substance to the water induces vertical migration, we added the same amount of TMAO and triethylamine to sterile water (both at 75 ȖM). As with the control Daphnia, there was no significant increase in day depth. We therefore conclude that the reaction to TMA is a specific one, and not simply a response to a change in conductivity or ionic strength of the medium.

Surface Sensing and Settlement Strategies of Marine Biofouling Organisms

“…A reliable operation is required at least for 1 week, the test setup needs to be easy to handle with less than 3 h of maintenance per week, and it should automatically detect alarm situations [6]. Daphnia (water fleas) respond to toxins by changing their activity which is manifested in a change in motility [7,8]. Such dynamical Daphnia tests were successfully applied at the Rhine river and seem to be especially useful to detect low concentrations of insecticides [9].…”

Plasticity in Pigmentation Induced by Conflicting Threats From Predation and Uv Radiation

“…Inducible defenses allow organisms to reap the benefits of a defense, while saving potential costs associated with investment in the defense. The cue transferring information of a predation risk is generally thought to be a chemical substance released by the predator, al- 1 E-mail: Lars-Anders.Hansson@limnol.lu.se though few such chemicals have actually been identified (Boriss et al 1999, Brö nmark and Hansson 2000, von Elert and Pohnert 2000. These cues, and others like them, can be considered a ''chemical information network'' (Hansson 2000a), and their possible existence may have a profound impact on our understanding of ecological systems.…”

Trimethylamine does not trigger antipredatory life history shifts in Daphnia

“…A recent paper by Boriss et al (1999) reported that trimethylamine (TMA) induces diel vertical migration in Daphnia and it is a biologically active component of the fish-exuded kairomone. If indeed TMA were an ecologically relevant cue, it should also induce characteristic antipredator life history shifts.…”

“…The concentrations used in this study were based on the results of Boriss et al (1999), so that the lower level was chosen to represent TMA concentration in naturally produced fish exudate and the higher to match that which was reported to induce pronounced migration behavior. The lower concentrations used (10-20 M) produced rather weak effects, but these effects were in the same direction as the effects of higher TMA concentrations.…”