title: Phototransduction and clock gene expression in the troglobiont beetle Ptomaphagus hirtus of Mammoth cave.
abstract: Obligatory 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.
authors: Department of Biological Sciences, Wayne State University, 5047 Gullen Mall, Detroit, MI 48202, USA. friedrichm@wayne.edu
authors: Markus
authors: M
authors: Friedrich
authors: Rui
authors: R
authors: Chen
authors: Bryce
authors: B
authors: Daines
authors: Riyue
authors: R
authors: Bao
authors: Jason
authors: J
authors: Caravas
authors: Puneet K
authors: PK
authors: Rai
authors: Maja
authors: M
authors: Zagmajster
authors: Stewart B
authors: SB
authors: Peck
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics / Q000502:physiology*; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D059552:Caves; D056925:Circadian Rhythm Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D001517:Coleoptera / Q000502:physiology*; D019295:Computational Biology; D003710:Demography; D007629:Kentucky; D055537:Light Signal Transduction / Q000235:genetics*; D016013:Likelihood Functions; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010775:Photic Stimulation; D010802:Phylogeny; D010858:Pigmentation / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D056925:Circadian Rhythm Signaling Peptides and Proteins