Scientific American - USA (2020-08)

August 2020, ScientificAmerican.com 19

ROGER DE LA HARPE

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B I O L O G Y

Safer Turtle

Sexing

A new blood test tells scientists whether hatchlings are male or female

Determining turtle hatchlings’ sexes is a challenging but critical task. For many species the embryo’s sex development depends on environmental temperatures, and rising heat is producing overabun dances of females and shortages of males. Unchecked, this mismatch could push some species toward extinction. To save them, “you have to really un derstand where the problems lie,” says Jeanette Wyneken, a biologist at Florida Atlantic University and senior author on a new study on the topic, published in March in Scientific Reports. Monitoring turtles’ sex ratios as hatchlings can help—but species with temperaturedependent sex determi nation lack sex chromosomes and mature relatively late, making their sexes hard to discover noninvasively. Wyneken’s team developed a blood test that determined the sexes of logger head and redeared slider hatchlings up to two days old with 100 percent accuracy. In older juvenile loggerheads, the results

were 90 percent accurate. The test checked a tiny blood sample for a hormone that prevents young males from develop ing oviducts. (The hormone takes on addi tional roles as the turtles grow, Wyneken says, which can complicate results for old er females.) The researchers then used two stan dard techniques to verify results for the turtles they tested. They analyzed tissue samples from gonads of their 10 redeared sliders, which were sacrificed as hatch lings, and five loggerheads, which were found dead in their nest boxes. They also raised 54 loggerhead juveniles to between 83 and 177 days old before performing laparoscopic surgeries on the live animals. These surgeries cannot be safely per formed on hatchlings, Wyneken says. The group is working to make the blood test field-ready. The researchers hope to use it to monitor sex ratios in easy to-catch wild hatchlings and perhaps find ways to intervene in the field, such as pro viding shade or cooling sprinklers when eggs are incubating. Unlike current meth ods, which require killing hatchlings or esti mating sex ratios based on incubation temperature, the new technique “is a non lethal and reliable method to determine hatchling sex,” says Camryn Allen, a wild life endocrinologist at the Pacific Island Fisheries Science Center, who was not involved with the study. — Rachel Crowell

Loggerhead sea turtle hatchlings

ROGER DE LA HARPE

Getty Images

B I O L O G Y

Safer Turtle

Sexing

Determiningturtlehatchlings’sexesis a challenging but critical task. For many species the embryo’s sex development depends on environmental temperatures, and rising heat is producing overabun dances of females and shortages of males. Unchecked, this mismatch could push some species toward extinction. To save them, “you have to really un derstand where the problems lie,” says Jeanette Wyneken, a biologist at Florida Atlantic University and senior author on a new study on the topic, published in March inScientific Reports.Monitoring turtles’ sex ratios as hatchlings can help—but species with temperaturedependent sex determi nation lack sex chromosomes and mature relatively late, making their sexes hard to discover noninvasively. Wyneken’s team developed a blood test that determined the sexes of logger head and redeared slider hatchlings up to two days old with 100 percent accuracy. In older juvenile loggerheads, the results

were 90percent accurate. The test checked a tiny blood sample for a hormone that prevents young males from develop ing oviducts. (The hormone takes on addi tional roles as the turtles grow, Wyneken says, which can complicate results for old er females.) The researchers then used two stan dard techniques to verify results for the turtles they tested. They analyzed tissue samples from gonads of their 10 redeared sliders, which were sacrificed as hatch lings, and five loggerheads, which were found dead in their nest boxes. They also raised 54 loggerhead juveniles to between 83 and 177 days old before performing laparoscopic surgeries on the live animals. These surgeries cannot be safely per formed on hatchlings, Wyneken says. The group is working to make the blood test fieldready. The researchers hope to use it to monitor sex ratios in easy to catch wild hatchlings and perhaps find ways to intervene in the field, such as pro viding shade or cooling sprinklers when eggs are incubating. Unlike current meth ods, which require killing hatchlings or esti mating sex ratios based on incubation temperature, the new technique “is a non lethal and reliable method to determine hatchling sex,” says Camryn Allen, a wild life endocrinologist at the Pacific Island Fisheries Science Center, who was not involved with the study. —RachelCrowell

ROGER DE LA HARPE

Getty Images

B I O L O G Y

Safer Turtle

Sexing

Determiningturtlehatchlings’sexesis a challenging but critical task. For many species the embryo’s sex development depends on environmental temperatures, and rising heat is producing overabun dances of females and shortages of males. Unchecked, this mismatch could push some species toward extinction. To save them, “you have to really un derstand where the problems lie,” says Jeanette Wyneken, a biologist at Florida Atlantic University and senior author on a new study on the topic, published in March inScientific Reports.Monitoring turtles’ sex ratios as hatchlings can help—but species with temperaturedependent sex determi nation lack sex chromosomes and mature relatively late, making their sexes hard to discover noninvasively. Wyneken’s team developed a blood test that determined the sexes of logger head and redeared slider hatchlings up to two days old with 100 percent accuracy. In older juvenile loggerheads, the results

were 90percent accurate. The test checked a tiny blood sample for a hormone that prevents young males from develop ing oviducts. (The hormone takes on addi tional roles as the turtles grow, Wyneken says, which can complicate results for old er females.) The researchers then used two stan dard techniques to verify results for the turtles they tested. They analyzed tissue samples from gonads of their 10 redeared sliders, which were sacrificed as hatch lings, and five loggerheads, which were found dead in their nest boxes. They also raised 54 loggerhead juveniles to between 83 and 177 days old before performing laparoscopic surgeries on the live animals. These surgeries cannot be safely per formed on hatchlings, Wyneken says. The group is working to make the blood test field-ready. The researchers hope to use it to monitor sex ratios in easy to-catch wild hatchlings and perhaps find ways to intervene in the field, such as pro viding shade or cooling sprinklers when eggs are incubating. Unlike current meth ods, which require killing hatchlings or esti mating sex ratios based on incubation temperature, the new technique “is a non lethal and reliable method to determine hatchling sex,” says Camryn Allen, a wild life endocrinologist at the Pacific Island Fisheries Science Center, who was not involved with the study. —RachelCrowell

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Scientific American - USA (2020-08)

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