Slacker fish, carnivorous pitfalls, a dinosaur gap and more in this week’s news

‘Gap’ dino supports sudden crash
A dinosaur horn found in Montana supports the idea that dinos died after a fatal thud. The fossil turned up within a much-discussed three meters of ground below what’s called the K-T boundary marking the end of remains from dinosaur days. A supposed absence of dinosaur fossils three meters below (and older than) the boundary has been invoked in arguments that dinosaurs had died out gradually, possibly from climate change, before an asteroid walloped Earth. Pollen analysis and other evidence, however, place the horn 13 centimeters below the boundary, supporting the idea that dinos hung on until a sudden event at the boundary, Tyler Lyson of Yale and colleagues report in an upcoming Biology Letters. —Susan Milius

Slacker fish
Personality, or consistent behavioral types, can have a lot to do with whether fish pitch in and help around the home. In debates about the evolution of helpful behavior, theories predict that relatives should benefit from aiding each other. In an experiment with cichlid fish, however, individual personality tendencies such as aggressiveness and risk aversion were better predictors than kinship of whether a fish pitched in to help defend or maintain a shared territory. Arguments about altruism need to account for differences in behavior, researchers in Europe contend in an upcoming Animal Behaviour. Susan Milius

Doubts about bee decline and Iridovirus
One suggested cause for the sudden collapse of bee colonies in North America has failed to gain support from a new study. Last year researchers proposed that an unidentified Iridovirus may combine with the well-known Nosema parasite as a deadly combo for honeybees. Now researchers from Columbia University and Penn State University in University Park have analyzed both healthy and collapsing colonies and also have re-examined older samples of bees. No connection with Iridovirus and colony collapse disorder has shown up in either case, the team reports online June 30 in PLoS ONE. —Susan Milius

Rethinking carnivorous pitfalls
A key aspect of the killing potential of Nepenthes pitcher plants has been underestimated, say researchers in France. Biologists have long described the carnivorous plants’ pitcher-shaped leaves as pitfall traps that lure insects down a slippery, wax-covered throat they can’t climb out of. A study of one Nepenthes species, however, identified liquid that pools in pitchers as viscous enough to trap insects in its own right. Now a new analysis of 23 kinds of pitchers finds other cases of dangerous liquid and suggests that plants may make tradeoffs in how much they invest in waxy walls — great for catching ants — versus gooey liquid that better traps flies, researchers report in the July New Phytologist. —Susan Milius

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