Native amphibian toxin reduces invasive crayfish feeding with potential benefits to stream biodiversity.

BACKGROUND: Biodiversity is generally reduced when non-native species invade an ecosystem. Invasive crayfish, Procambarus clarkii, populate California freshwater streams, and in the Santa Monica Mountains (Los Angeles, USA), their introduction has led to trophic cascades due to omnivorous feeding behavior and a rapid rate of population growth. The native California newt, Taricha torosa, possesses a neurotoxin, tetrodotoxin (TTX), that affects freshwater animal behavior. Given P. clarkii has a limited evolutionary history with TTX, we hypothesized that TTX may affect crayfish feeding behaviors. To determine if TTX affects P. clarkii behavior, we measured cumulative movement and various feeding behaviors of P. clarkii exposed to (i) waterborne, ecologically realistic concentrations of TTX (~ 3.0 × 10- 8 moles/L), (ii) an anuran chemical cue to account for intraguild cues, or (iii) a T. torosa chemical cue with quantitated TTX in it (~ 6.2 × 10- 8 moles/L). RESULTS: We found that the presence of TTX in any form significantly reduced crayfish movement and decreased the amount of food consumed over time. Crayfish responses to the anuran treatment did not significantly differ from controls. CONCLUSION: Our laboratory results show that naturally occurring neurotoxin from native California newts limits invasive crayfish foraging and feeding rates, which may play a role in preserving local stream ecosystems by limiting invasive crayfish behaviors that are detrimental to biodiversity.

A Genetic Interaction Map of Insulin Production Identifies Mfi as an Inhibitor of Mitochondrial Fission.

Insulin production by the pancreatic ß cell is critical for the glucose homeostasis of the whole organism. Although the transcription factors required for insulin production are known, the upstream pathways that control insulin production are less clear. To further elucidate this regulatory network, we created a genetic interaction map of insulin production by performing ∼20,000 pairwise RNA interference knockdowns of insulin promoter regulators. Our map correctly predicted known physical complexes in the electron transport chain and a role for Spry2 in the unfolded protein response. To further validate our map, we used it to predict the function of an unannotated gene encoding a 37-kDa protein with no identifiable domains we have termed mitochondrial fission factor interactor (Mfi). We have shown that Mfi is a binding partner of the mitochondrial fission factor and that Mfi inhibits dynamin-like protein 1 recruitment to mitochondria. Our data provide a resource to understand the regulatory network of insulin promoter activity.