Researchers from University of Pittsburgh revealed that Manatees lack a protein that breaks down organophosphates
Manatees, also known as sea cows, are herbivorous marine mammals that have lost working versions of certain genes millions of years ago. One of those genes protects land mammals against some harmful fertilizers and pesticides. The gene breaks down certain toxic chemicals. However, the gene in these marine mammals appears to be faulty that potentially leaves manatees, dolphins and other warm-blooded water dwellers more sensitive to dangerous chemicals from pesticides.
PON1, the gene in discussion, carries instructions for production of a protein that interacts with fatty acids ingested with food. However, researchers found that PON1 has taken on another role in recent decades. The protein breaks down toxic chemicals found in a popular class of pesticides called organophosphates. The pesticides can poison waterways and coastal areas and harm wildlife, when the chemicals drain from agricultural fields. The researchers inspected genetic instructions of 53 land mammal species and found the gene intact. However, PON1 was riddled with mutations that made it useless in five marine mammal species. According to the researchers, PON1 became defunct around 64 to 21 million years ago, owing to possible changes in diet. Moreover, behavioral changes in marine ancestors due to movement from land to sea could be another factor for the defunct gene.
Furthermore, the researchers measured the rate of breakdown of two organophosphate chemicals — chlorpyrifos oxon and diazoxon in blood samples from five land mammal species and six marine or semiaquatic mammal species. A decrease in toxic molecules over time was observed in the blood from the terrestrial species such as sheep, goats and ferrets. However, no change was observed in the blood samples of marine species. The researchers genetically modified mice with absence of the gene and found that the animal could not breakdown the chemicals. The research was published in Science on August 10, 2018.