02369nas a2200253   4500008004100000245010900041210006900150300001400219490000800233520154400241653002001785653002001805653001401825653002201839100001701861700001201878700001401890700001101904700001501915700001201930700001801942700001301960856014201973       2011                        eng d00aPhototransduction and clock gene expression in the troglobiont beetle Ptomaphagus hirtus of Mammoth cave0 aPhototransduction and clock gene expression in the troglobiont b  a3532-35410 v2143 aObligatory cave species exhibit dramatic trait modifications such as eye reduction, loss of pigmentation and an increase in touch receptors. As molecular studies of cave adaptation have largely concentrated on vertebrate models, it is not yet possible to probe for genetic universalities underlying cave adaptation. We have therefore begun to study the strongly cave-adapted small carrion beetle Ptomaphagus hirtus. For over 100 years, this flightless signature inhabitant of Mammoth Cave, the world's largest known cave system, has been considered blind despite the presence of residual lens structures. By deep sequencing of the adult head transcriptome, we discovered the transcripts of all core members of the phototransduction protein machinery. Combined with the absence of transcripts of select structural photoreceptor and eye pigmentation genes, these data suggest a reduced but functional visual system in P. hirtus. This conclusion was corroborated by a negative phototactic response of P. hirtus in light/dark choice tests. We further detected the expression of the complete circadian clock gene network in P. hirtus, raising the possibility of a role of light sensation in the regulation of oscillating processes. We speculate that P. hirtus is representative of a large number of animal species with highly reduced but persisting visual capacities in the twilight zone of the subterranean realm. These can now be studied on a broad comparative scale given the efficiency of transcript discovery by next-generation sequencing.10acave adaptation10acircadian clock10aevolution10aphototransduction1 aFriedrich, M1 aChen, R1 aDaines, B1 aBao, R1 aCaravas, J1 aRai, PK1 aZagmajster, M1 aPECK, SB  uhttps://cholevidae.myspecies.info/en/content/phototransduction-and-clock-gene-expression-troglobiont-beetle-ptomaphagus-hirtus-mammoth-ca