Widespread Passive Accumulation of Alkaloids in Putatively Non-Toxic Frogs Challenges Paradigms of the Origins of Acquired Chemical Defenses

Centrala begrepp

Contrary to previous assumptions, many undefended poison frog species have measurable levels of alkaloids, suggesting the existence of a phenotypic intermediate between toxin consumption and sequestration - passive accumulation - that differs from active sequestration.

Sammanfattning

The study provides new data showing that, in contrast to previous studies, species from each undefended poison frog clade have measurable yet low amounts of alkaloids. The authors confirm that undefended dendrobatids regularly consume mites and ants, which are known sources of alkaloids. They also confirm the presence of alkaloids in two putatively non-toxic frogs from other families.

The data suggest the existence of a phenotypic intermediate between toxin consumption and sequestration - passive accumulation - that differs from active sequestration in that it involves no derived forms of transport and storage mechanisms yet results in low levels of toxin accumulation. The authors discuss the concept of passive accumulation and its potential role in the origin of chemical defenses in poison frogs and other toxin-sequestering organisms.

The authors propose that the ancestral state of poison frogs (and potentially other clades with alkaloid-sequestering species) is alkaloid consumption and low levels of alkaloid resistance, accompanied by passive alkaloid accumulation. Selection then acted on the efficiency of toxin elimination and sequestration to result in toxin accumulation and chemical defense.

Statistik

Defended dendrobatid species had 10-20x higher alkaloid diversity and 75,000x higher total alkaloid quantity compared to undefended species.
Ants and mites composed a large proportion of the stomach contents in both undefended and defended species.

Citat

"Contrary to previous assumptions, many undefended poison frog species have measurable levels of alkaloids, suggesting the existence of a phenotypic intermediate between toxin consumption and sequestration - passive accumulation - that differs from active sequestration."
"The data suggest the existence of a phenotypic intermediate between toxin consumption and sequestration - passive accumulation - that differs from active sequestration in that it involves no derived forms of transport and storage mechanisms yet results in low levels of toxin accumulation."
"The authors propose that the ancestral state of poison frogs (and potentially other clades with alkaloid-sequestering species) is alkaloid consumption and low levels of alkaloid resistance, accompanied by passive alkaloid accumulation."

Viktiga insikter från

Passive accumulation of alkaloids in non-toxic frogs challenges paradigms of the origins of acquired chemical defenses

by Tarvin,R. D.... på www.biorxiv.org 05-15-2024

https://www.biorxiv.org/content/10.1101/2024.05.13.593697v2

Djupare frågor

How do the rates of toxin intake, elimination, and sequestration differ between defended and undefended poison frog species?

In poison frog species, the rates of toxin intake, elimination, and sequestration play crucial roles in determining the level of chemical defense present in the species. Defended poison frog species typically have higher rates of toxin intake, as they actively consume alkaloid-containing prey items. These species have evolved mechanisms to resist the toxic effects of these compounds, allowing them to accumulate higher levels of toxins in their skin for defense against predators. On the other hand, undefended poison frog species also consume alkaloid-containing prey, but they exhibit lower levels of toxin intake compared to defended species. This lower intake may be due to dietary preferences or other factors that limit their exposure to toxins.
In terms of toxin elimination, defended species often have slower rates of elimination, allowing them to retain higher levels of toxins in their bodies for longer periods. This slow elimination rate is advantageous for maintaining a potent chemical defense. In contrast, undefended species are likely to have faster rates of toxin elimination, leading to lower levels of toxin accumulation in their bodies. This difference in elimination rates may contribute to the varying levels of chemical defense observed between defended and undefended species.
Regarding toxin sequestration, defended poison frog species have evolved active mechanisms to transport and store toxins in specific locations, such as their skin glands. These active sequestration mechanisms enable them to concentrate and retain high levels of toxins, enhancing their chemical defense. In contrast, undefended species may exhibit passive accumulation of toxins, where they lack specialized transport and storage mechanisms for toxins. This passive accumulation results in lower levels of toxin accumulation in their bodies compared to actively sequestering species.
Overall, defended poison frog species show higher rates of toxin intake, slower rates of toxin elimination, and active sequestration mechanisms, leading to potent chemical defenses. In contrast, undefended species exhibit lower toxin intake, faster toxin elimination, and may rely on passive accumulation of toxins, resulting in lower levels of chemical defense.

How do the rates of toxin intake, elimination, and sequestration differ between defended and undefended poison frog species?

In poison frog species, the rates of toxin intake, elimination, and sequestration play crucial roles in determining the level of chemical defense present in the species. Defended poison frog species typically have higher rates of toxin intake, as they actively consume alkaloid-containing prey items. These species have evolved mechanisms to resist the toxic effects of these compounds, allowing them to accumulate higher levels of toxins in their skin for defense against predators. On the other hand, undefended poison frog species also consume alkaloid-containing prey, but they exhibit lower levels of toxin intake compared to defended species. This lower intake may be due to dietary preferences or other factors that limit their exposure to toxins.
In terms of toxin elimination, defended species often have slower rates of elimination, allowing them to retain higher levels of toxins in their bodies for longer periods. This slow elimination rate is advantageous for maintaining a potent chemical defense. In contrast, undefended species are likely to have faster rates of toxin elimination, leading to lower levels of toxin accumulation in their bodies. This difference in elimination rates may contribute to the varying levels of chemical defense observed between defended and undefended species.
Regarding toxin sequestration, defended poison frog species have evolved active mechanisms to transport and store toxins in specific locations, such as their skin glands. These active sequestration mechanisms enable them to concentrate and retain high levels of toxins, enhancing their chemical defense. In contrast, undefended species may exhibit passive accumulation of toxins, where they lack specialized transport and storage mechanisms for toxins. This passive accumulation results in lower levels of toxin accumulation in their bodies compared to actively sequestering species.
Overall, defended poison frog species show higher rates of toxin intake, slower rates of toxin elimination, and active sequestration mechanisms, leading to potent chemical defenses. In contrast, undefended species exhibit lower toxin intake, faster toxin elimination, and may rely on passive accumulation of toxins, resulting in lower levels of chemical defense.

How do the rates of toxin intake, elimination, and sequestration differ between defended and undefended poison frog species?

In poison frog species, the rates of toxin intake, elimination, and sequestration play crucial roles in determining the level of chemical defense present in the species. Defended poison frog species typically have higher rates of toxin intake, as they actively consume alkaloid-containing prey items. These species have evolved mechanisms to resist the toxic effects of these compounds, allowing them to accumulate higher levels of toxins in their skin for defense against predators. On the other hand, undefended poison frog species also consume alkaloid-containing prey, but they exhibit lower levels of toxin intake compared to defended species. This lower intake may be due to dietary preferences or other factors that limit their exposure to toxins.
In terms of toxin elimination, defended species often have slower rates of elimination, allowing them to retain higher levels of toxins in their bodies for longer periods. This slow elimination rate is advantageous for maintaining a potent chemical defense. In contrast, undefended species are likely to have faster rates of toxin elimination, leading to lower levels of toxin accumulation in their bodies. This difference in elimination rates may contribute to the varying levels of chemical defense observed between defended and undefended species.
Regarding toxin sequestration, defended poison frog species have evolved active mechanisms to transport and store toxins in specific locations, such as their skin glands. These active sequestration mechanisms enable them to concentrate and retain high levels of toxins, enhancing their chemical defense. In contrast, undefended species may exhibit passive accumulation of toxins, where they lack specialized transport and storage mechanisms for toxins. This passive accumulation results in lower levels of toxin accumulation in their bodies compared to actively sequestering species.
Overall, defended poison frog species show higher rates of toxin intake, slower rates of toxin elimination, and active sequestration mechanisms, leading to potent chemical defenses. In contrast, undefended species exhibit lower toxin intake, faster toxin elimination, and may rely on passive accumulation of toxins, resulting in lower levels of chemical defense.