photo by Lorenzo Blangiardi
As any fan of Steven Spielberg’s “Jurassic Park” knows, life, uh, finds a way.
Granted, most of us won’t encounter the deadly consequences of applying this theory to dinosaurs in any way more personal than buying a ticket to the latest installment of the film franchise this weekend. But scientists are discovering that the fictional Ian Malcolm (played by Jeff Goldblum) may have been on to something after all.
A new study in the journal “Current Biology” details the discovery of seven smalltooth sawfish conceived through a process called facultative parthenogenesis, according to the Miami Herald. What makes this noteworthy is that parthenogenesis, the production of offspring without male sperm in a species that typically relies on sexual reproduction, is a process researchers had never before verified occurring in the wild.
Parthenogenesis occurs when an unfertilized egg absorbs a genetically identical cell that splits off during meiosis, called a “polar body.” The result is an offspring with two sets of identical chromosomes in each cell, a half-clone of the mother. Warren Booth, an evolutionary biologist at the University of Tulsa, characterized the process as “a very extreme form of inbreeding.”
While birds, sharks and reptiles have occasionally demonstrated parthenogenesis in captivity, the discovery of the sawfish broke new ground. The scientists said it was the first solid evidence of viable asexual reproduction in the wild for a vertebrate species. While scientists did observe facultative parthenogenesis in wild pit vipers in 2012, the snakes gave birth in a lab, and scientists were uncertain whether the offspring would have survived outside lab conditions.
The Stony Brook University researchers and the Florida scientists with whom they partnered were engaged in DNA fingerprinting when they discovered the fish in the Caloosahatchee and Peace rivers. While the cause of the phenomenon is not clear, the process may be the fish’s way of fighting back against dangerously shrinking populations caused by commercial fishing and loss of habitat. Andrew Fields, a Stony Brook doctoral student who was the lead author of the study, thinks that if scientists could identify what caused these unusual offspring, it might help in prioritizing endangered species.
The scientists were surprised to discover that the seven sawfish appeared to be in perfect health. They tagged the fish before releasing them back into the wild. Researchers hope to gather more data to see how the seven sawfish fare over time and, crucially, whether they will successfully reproduce. It had been previously assumed that parthenogenesis was a reproductive dead end. However, scientists are questioning this assumption; it was also widely accepted that parthenogenetic offspring arrived one at a time, but five of the seven sawfish appear to be siblings.
The authors of the study noted that parthenogenesis alone won’t preserve the sawfish if the destruction of their habitat and commercial fishing patterns continue. And asexual reproduction necessarily sacrifices a population’s genetic diversity, leaving the species more vulnerable to hostile environmental changes. But it may buy the species more time. And looking for wild animals who have hatched from unfertilized eggs may also serve as an early warning system for naturalists that wild populations have reached critically low levels. What is clear is that nature defying our expectations is very real, not simply the stuff of science fiction.
Maybe this is a case of life imitating art, or the other way around. Maybe Spielberg’s publicists are way, way better than we think. Or maybe the sawfish have been hatching this scheme (not to mention their babies) ever since the first flick came out in 1993.
In any case, Ian Malcolm was right: We know a lot less about nature than we think. Life finds a way.