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Sexual reproduction in jellyfish species (Scyphozoa, Cnidaria) of Southeast Brazilian coast

Grant number: 17/12970-5
Support type:Scholarships in Brazil - Doctorate
Effective date (Start): December 01, 2017
Effective date (End): April 30, 2021
Field of knowledge:Biological Sciences - Zoology - Morphology of Recent Groups
Principal Investigator:André Carrara Morandini
Grantee:Gisele Rodrigues Tiseo
Home Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

For Scyphozoa-class jellyfishes there is little information describing the formation and morphology of the gonad, as well as few studies assessing gonadal growth compared to somatic growth. The present project aims to fill gaps within the knowledge of the sexual reproduction of Scyphozoa species, focusing on two aspects: an ecological approach (determination of somatic and gonadal growth) and the morphological approach (description of morphogenesis and origin of the gonad). To this end, eight species belonging to different orders of scyphomedusae will be used: Coronatae (Nausithoe aurea, N. eumedusoides), Semaeostomeae (Chrysaora lactea, C. plocamia, Aurelia coerulea) and Rhizostomeae (Lychnorhiza lucerna, Cassiopea andromeda, Stomolophus cf. meleagris). These species will be cultivated in the laboratory and the growth from ephyra to mature adult jellyfish will be monitored weekly. The laboratory data will be combined with observations of specimens of the nature that will be collected monthly, in the region of Praia do Jabaquara, municipality of São Sebastião, for two years to obtain individuals of all size classes of the species L. lucerna and C. Lactea. Measurements of the umbrella diameter, wet weight, dry weight and ash-free dry weight of both the individual and the gonad will be taken for later calculations of somatic and gonadal growth. For the description of gonadal morphogenesis, samples for light microscopy will be fixed in 4% paraformaldehyde prepared with seawater in 0.2M sodium phosphate buffer for 24 hours. After fixation, the samples will be buffered in 0.2M sodium phosphate buffer and processed according to histology protocol in Leica® historesin and paraffin. For transmission electron microscopy (MET) gonadal fragments will be fixed in Karnovsky's solution 2.5% glutaraldehyde, 2% paraformaldehyde in 0.1M sodium cacodylate buffer (pH 7.4) with 2.5mM CaCl2 for four hours at 4 ° C, and subsequently processed according to MET protocol for Spurr® resin. For the analysis of the macroscopic morphology of the gonad in Micro-CT, whole individuals of the species Nausithoe aurea and Nausithoe eumedusoides will be fixed in Trumps solution (4% paraformaldehyde, 1% glutaraldehyde in 0.2M sodium cacodylate buffer and sucrose) for 24 hours and processed according to the protocol for observation of resin blocks in Micro-CT. In order to identify the origin of the gonad from interstitial cells of the gastrodermis, individuals of the species Nausithoe aurea and Aurelia aurita will be fixed in 4% paraformaldehyde for one hour, washed four times in 3% Triton sodium phosphate buffer and blocked in sodium phosphate buffer Triton With 2% bovine serum albumin for 30 minutes. Subsequently, an antibody specific for BrdU labeling, conjugated to a fluorochrome, will be applied to the sections, which will then be analysed using the Leica® confocal microscope. (AU)