Adaptations to in situ feeding: novel nutrient acquisition pathways in an ancient vertebrate.

Abstract in brief

• Hagfish, which often feed on decaying carcasses, can absorb amino acids like alanine and glycine directly through their skin and gills, marking the first evidence of direct organic nutrient uptake in vertebrates.
• This nutrient absorption occurs via different mechanisms depending on factors like concentration and inhibitors, with notable differences between juvenile and adult hagfish, suggesting an adaptive strategy to their scavenging lifestyle.
• From an evolutionary perspective, hagfish show a transitional stage between invertebrates that absorb nutrients broadly and more advanced vertebrates with specialized digestive systems.]