Fossilized brains of the ancient ancestors of spiders, insects and crustaceans are giving hints about how those creatures evolved from soft- to hard-bodied.
Javier Ortega-Hernández from the University of Cambridge studied 500-million-year-old brain remnants from two types of arthropod ancestors, including the submarine-like Odaraia alata. In these creatures,
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, traces of nerves appear to connect the front of the brain to eyelike features and a hard plate, called the anterior sclerite, Ortega-Hernández reports May 7 in Current Biology.
Modern arthropods don’t have these hard plates. Finding them in arthropod ancestors suggests the plates acted as a transitional element that helped the animals evolve from soft, jellylike organisms to the hard-bodied creatures of today, Ortega-Hernández argues.
Great tits use syntax to compose their tunes,
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.
Japanese great tits (Parus minor) communicate using at least 10 different notes on their own and in combination. Researchers played different calls for Japanese great tits in a forest in Nagano, Japan, to see how the birds responded — an indication of what the call might mean. The birds responded differently to individual notes than they did when played the same note in combination with other notes. And, when researchers reversed the note order, the birds didn’t respond the same way.
By itself, a note means one thing to great tits, but in combination, it means something different, the team argues March 8 in Nature Communications. Similarly, among humans, the order of words in a sentence,
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, its compositional syntax,
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, matters. ?
Some primates combine calls to convey different messages, but individual notes don’t carry unique meaning in these species. Great tits are the first nonhuman species shown to use compositional syntax, the researchers write.?
Listen to recordings from the study:
In this recording, researchers played three types of calls for Japanese great tits: First, a call with three notes — A, B, and C — which signals danger; second, a one-note call (D), which attracts mates; and finally,
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, a combination call,
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, ABC-D,
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, which causes the birds to scan the skies for predators and fly to the source of the sound.?
Credit: Toshitaka Suzuki
Researchers played an ABC-D call for great tits,
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, and then reversed an ABC-D call. Birds responded differently in each case.
Credit: Toshitaka Suzuki
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