Green fluorescence from non‐aequorea hydrozoa Gonionemus vertens (Clinging Jellyfish)

We have examined the green fluorescence of the Clinging Jellyfish, Gonionemus vertens (GV), a species that first appeared in New Jersey coastal estuaries in June, 2016. Intact specimens (0.30–0.35 g wet weight) were homogenized in 3 mL of pure water using a Kontes Glass homogenizer (Co 23; Vineland, NJ) with 10 rotational strokes and centrifuged at 16,100 × g for 10 min at 4°C (Eppendorf 5415D microcentrifuge). Two mL of the supernatant was placed in a standard 1 cm methacrylate cuvette and fluorescence was measured with a Hitachi F‐7000 spectrofluorometer at 25°C. In vitro excitation and emission maxima were λ ExMax = 501.4±0.2 (nm) (n=4) and λ EmMax = 512.9±0.2 (nm) (n=3), respectively for the 4 individuals measured. Adult medusa of GV are relatively small and fit in a standard 1 cm spectroscopic cuvette, so we measured in vivo fluorescence of the intact individuals in sterile artificial seawater (20 ppm). When first placed in the cuvette, actively swimming GV cannot be measured; but after some time, individuals use their tentacles to cling to the inner cuvette wall and remain stationary permitting measurements. Multiple spectral scans from 450 nm to 510 nm (excitation scan) or from 510 to 570 nm (emission scan) at 240 nm/min (15 seconds per scan) were performed. In five individuals successfully measured without movements, excitation and emission maxima were λ ExMax = 503.9±0.4 (nm) (n=5) and λ EmMax = 515.4±0.2 (nm) (n=5), respectively. t ‐tests between in vitro and in vivo measurements showed a significant difference between both excitation maxima (p<0.001) and emission maxima (p<0.0001), indicating that the green fluorescence of GV is sensitive to environmental parameters. A search of the literature of green fluorescent proteins suggests that the particular excitation/emission pattern we have recorded in GV is unique and represents the shortest Stokes shift seen in nature. We plan to continue our studies on the green fluorescence of GV with a goal of isolating both the gene and protein responsible for this fluorescence through transcriptome analysis. Support or Funding Information Sokol grant to JG, VS, and EP