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Photo- and termo-reception systems in the blue crab, Callinectes sapidus (Crustacea Brachyura), and their relationship with the molt cycle

Grant number: 18/23043-0
Support type:Scholarships in Brazil - Doctorate
Effective date (Start): September 01, 2019
Effective date (End): June 30, 2022
Field of knowledge:Biological Sciences - Physiology
Principal Investigator:Ana Maria de Lauro Castrucci
Grantee:Daniela Dantas David
Home Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Environmental signals synchronize endogenous rhythms to external clues, mainly light-dark and temperature cycles, through clock genes transcription and translation along 24 hours. The clock machinery is present in the mammalian central oscillator and in peripheral tissues of all vertebrates studied to date. In crustaceans, a central oscillator has not been yet identified, and photoreceptors containing long- and short-wavelength opsins are distributed throughout the central nervous system. In addition to being light sensors, opsins such as the mammalian melanopsin and Drosophila rhodopsin, which share the same signaling pathway, were also characterized as thermoreceptors. These photopigments ultimately trigger the opening of transient receptor potential channels (TRP) and membrane depolarization. TRP channels may directly respond to stimuli, such as temperature. In crustaceans a few have been sequenced, however their functionality remains unknown. In addition to light and temperature, hormonal factors from X-organ/sinus gland (XO/SG) complex in association with Y-organ, also regulate rhythmic functions such as the molt cycle. Having this in mind, we propose to determine, along the molt cycle of Callinectes sapidus: 1) the influence of photoperiod and temperature on clock genes, opsins and TRP channels in XO/SG complex, Y-organ, cerebral ganglion and hepatopancreas in vivo; 2) the autonomy of photo- and thermo-reception of these organs and the role of opsins and TRP channels in vitro. For that, our experimental approaches will be quantitative PCR for clock genes, opsins, TRP channels and molt-inhibiting hormone (CasMIH); immunohistochemistry of the hepatopancreas; quantification of ecdysteroids and melatonin by ELISA and radioimmunoassay, and serotonin by HPLC in vivo and in organ explants of Callinectes sapidus subject to 8:16 LD, 12:12 LD and 16:8 LD, combined with 17oC, 22oC and 27oC.