Natures wonders: Water fleas grow armor (Introduction)

by David Turell @, Thursday, July 07, 2016, 00:00 (1457 days ago) @ David Turell

Water fleas grow exoskeletons shaped to repel specific predators depending on which are present:

"Water fleas prepare for battle by growing armor that's customized to specific enemies, new research finds.

"Tiny Daphnia species develop impressive protective structures as they mature, including pointy tail spines and tough helmets. Now, researcher Linda Weiss of Ruhr-University Bochum in Germany and her colleagues have found the neurotransmitters that help water fleas customize their bodies in response to the chemical cues in their watery environments.

"'Dopamine, in particular, appears to code neuronal signals into endocrine [hormone] signals," Weiss said in a statement.


"When juvenile Daphnia molt and develop a mature exoskeleton, they mold their bodies based on the chemicals they encounter in the water. The water fleas use appendages called antennules to detect scents and chemicals left by predators (fish, for example, or the upside-down swimming insects called backswimmers). They then develop armor defenses in response to the threats they expect to face.

"'These defenses are speculated to act like an anti-lock key system, which means that they somehow interfere with the predator's feeding apparatus," Weiss said. "Many freshwater fish can only eat small prey. So, for example, Daphnia lumholtzi grows head and tail spines to make eating them more difficult."


"Weiss and her colleagues have found the intermediary steps that make this transformation occur. The antennules create brain signals when they detect chemical cues, which in turn cause the release of the neurotransmitter dopamine. Dopamine, in turn, cues the release of juvenile hormones that promote growth in particular body regions.

"The same juvenile hormones promote growth in many other arthropods, Weiss said, which suggests that this developmental pathway is a widely shared way for crustaceans and insects to respond to environmental conditions."

Comment: A complex mechanism involving nerve impulses and the release of dopamine. Saltation?

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