Primary cilia may help turtle embryos sense nest temperatures that determine sex

Researchers at Iowa State University have identified a potential role for primary cilia — tiny, antenna-like protrusions on most animal cells — in the way turtle embryos sense the nest temperatures that decide their sex. The study, published in PLOS One, compared gene regulatory networks in two turtle species that use different sex-determination systems.

Painted turtles rely on temperature-dependent sex determination, where warmer nests produce females and cooler nests produce males. Spiny softshell turtles, by contrast, have evolved sex chromosomes. By modeling the transcription factor hubs that control gonad development in both species, the team found 89 shared hubs, 50 of which were unchanged, suggesting a core genetic toolkit for building turtle gonads.

The remaining hubs that differed most between the two species were unexpectedly enriched for genes associated with primary cilia. In painted turtles, these genes were linked to ciliary function, while in spiny softshells they were tied to cilia structure and formation. Multiple analytical approaches converged on the same signal, and a forthcoming histone study from the same lab points in a similar direction.

Primary cilia are known to detect environmental cues such as temperature and to regulate major signaling pathways, some of which have been implicated in mammalian sexual development. The researchers hypothesize that these cellular antennas may directly mediate the temperature signal that directs sex differentiation in painted turtles, though experimental validation is still needed.

The discovery connects a long-standing question in evolutionary biology — how temperature translates into a developmental decision — to a rapidly growing area of biomedical research. Dysfunctional primary cilia are implicated in a range of human disorders, including certain cancers, brain diseases and lung conditions.

Nicole Valenzuela, the lead author and a professor of ecology, evolution and organismal biology, said the work opens a new research avenue to characterize primary cilia in turtles, understand their composition and test how they respond to temperature and other signals. She noted that turtles' remarkable tolerance of extreme cold might also be illuminated by studying their thermal sensory mechanisms.

The study was led by Thea B. Gessler and colleagues and appears in PLOS One (2026). Funding and institutional support were provided by Iowa State University.