“In this case, there were fewer receptors than in the octopus, and they looked more like the neurotransmitter binding pocket in that it can bind more hydrophilic molecules,” said Bellono. Again, the team found the major difference between the human neurotransmitter receptor and the squid receptor was in the binding pocket. If a squid senses bitterness, it may interpret it as toxic or undesirable and will release its prey. The team discovered that squid receptors have adapted to sense bitter molecules. “In the second paper, we found that the squid’s chemical receptors are more analogous to our sense of taste,” Bellono said. Rather than using their arms to probe surfaces, they grab prey, reeling it in to eat.
In contrast with their octopus cousins, squid are ambush predators that strike and capture unsuspecting prey with their eight arms and two long tentacles. Octopus use their arms for “taste by touch,” explained senior investigator Nicholas Bellono. This explains how an animal like the octopus can transition from neurotransmission to environmental chemosensation, such as a sense of smell or taste, by subtly changing just part of the protein to create a new receptor and behavioral function. “And we discovered that the binding pocket is under evolutionary selective pressure.” “But the binding pocket of the octopus receptor, although in a similar spot that the ancestral neurotransmitter sticks to, is very different,” Bellono said of the large, sticky surface. The overall architecture of the two receptors looked similar. The team determined the 3D structure of the octopus chemotactile receptor and compared it with the acetylcholine receptor to examine how it transitioned from its ancestral role in neurotransmission. “They use their arms for ‘taste by touch’ contact-dependent aquatic exploration of crevices in the sea floor,” said senior investigator Nicholas Bellono, associate professor in the Department of Molecular and Cellular Biology. Instead of sensing neurotransmitters, however, octopus receptors contain important adaptations to sense relatively insoluble, greasy molecules that stick to surfaces. They discovered that octopus chemotactile receptors evolved from acetylcholine neurotransmitter receptors, the same kind that humans have at our neuromuscular junction. In the first of the papers, the researchers describe how the octopus repurposes ancestral neurotransmitter receptors to sense its external environment. Squid are ambush predators that strike and capture unsuspecting prey with their eight arms and two long tentacles. They describe how the animals evolved using a family of chemotactile receptors within their arms and offer a glimpse into how such functional changes likely took place as adaptations to environment over deep evolutionary time. In two separate studies published in Nature, researchers from the Bellono lab at Harvard and Ryan Hibbs’ lab at UC San Diego discovered some clues, focusing on how cephalopod nervous systems adapt to sense their marine environments. So how did these animals evolve neurologically from the shelled mollusk to a behaviorally sophisticated creature? These animals have elaborate compact nervous systems located within specialized arm appendages, which can perform a surprisingly diverse group of behaviors. Two new studies describe path of divergent sensing capabilities, tracking lineage from common ancestral neurons.Ĭephalopods such as octopus and squid evolutionarily diverged from mollusks like slugs and snails.
0 kommentar(er)
