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Jellyfish are economically important organisms in diverse countries, carnivorous organisms that consume various prey (crustaceans, mollusks, bivalves, etc .) and dissolved carbohydrates in marine waters. This study was focused on detecting and quantifying the activity of digestive glycosidases from the cannonball jellyfish ( Stomolophus sp. 2) to understand carbohydrate digestion and its temporal-spatial variation. Twenty-three jellyfish gastric pouches were collected in 2015 and 2016 in the Gulf of California in three localities (Las Guásimas, Hermosillo, and Caborca). Nine samples were in intra-localities from Las Guásimas. Chitinase (Ch), β -glucosidase ( β -glu), and β - N -acetylhexosaminidase ( β -NAHA) were detected in the gastric pouches. However, cellulase, exoglucanase, α -amylase, polygalacturonase, xylanase, and κ -carrageenase were undetected. Detected enzymes showed halotolerant glycolytic activity ( i = 0-4 M NaCl), optimal pH, and temperature at 5.0 and 30-50 °C, respectively. At least five β -glucosidase and two β -N-acetylhexosaminidase were detected using zymograms; however, the number of proteins with chitinase activity is not precise. The annual variation of cannonball jellyfish digestive glycosidases from Las Guásimas between 2015-2016 does not show significant differences despite the difference in phytoplankton measured as chlorophyll α (1.9 and 3.4 mg/m 3 , respectively). In the inter-localities, the glycosidase activity was statistically different in all localities, except for β - N -acetylhexosaminidase activity between Caborca and Hermosillo (3,009.08 ± 87.95 and 3,101.81 ± 281.11 mU/g of the gastric pouch, respectively), with chlorophyll α concentrations of 2.6, 3.4 mg/m 3 , respectively. For intra-localities, the glycosidase activity did not show significant differences, with a mean chlorophyll α of 1.3 ± 0.1 mg/m 3 . These results suggest that digestive glycosidases from Stomolophus sp. 2 can hydrolyze several carbohydrates that may belong to their prey or carbohydrates dissolved in marine waters, with salinity over ≥ 0.6 M NaCl and diverse temperature (4-80 °C) conditions. Also, chlorophyll α is related to glycosidase activity in both seasons and inter-localities, except for chitinase activity in an intra-locality (Las Guásimas)., Competing Interests: The authors declare there are no competing interests., (©2023 Martinez-Perez et al.)

The digestive system and metabolism of the cannonball jellyfish Stomolophus sp. 2 are not well-known. The digestion study was critical to explain its ecology and bloom success. Different enzymes are involved in food digestion, which hydrolyze carbohydrates, proteins, and lipids. This study detected lipolytic activity in enzymatic extracts from gastric pouches of Stomolophus sp. 2 collected in the summer of 2013 at Bahía de Kino, Sonora, México (28°47'47″N 111°57'25″W). Lipase/esterase activity showed optimal pH at 11.0 and 50-60 °C with a half-life (t 1/2 ) of 33 min at 55 °C, whereas halotolerance of this activity was recorded from 0-4 M NaCl. Metal ions Ca 2+ and Mn 2+ did not affect the activity, but Mg 2+ decreased it 14.2% ± 3.15, while chelating agents as ethylenediaminetetraacetic acid reduced the activity 8.55% ± 2.13. Inhibition of lipase/esterase activity with tetrahydrolipstatin and paraoxon-ethyl decreased the activity 18.2% ± 2.3, and 62.80% ± 0.74, respectively, whereas phenylmethanesulfonyl fluoride (a protease inhibitor) did not affect it. The enzyme displayed a higher specificity for short-chain triglycerides, but triolein, coconut oil, olive oil, and fish oil were hydrolyzed. For the first time, phospholipase activity from the gastric pouch of Stomolophus sp. 2 was detected using L-α-phosphatidylethanolamine from chicken egg yolk as a substrate. These results suggest that Stomolophus sp. 2 hydrolyze several kinds of lipids, and lipolytic enzymes are active at alkaline pH under different saline conditions, which may be essential to digest different preys., Competing Interests: The authors declare there are no competing interests., (©2020 Martínez-Pérez et al.)

The Cannonball jellyfish (Stomolophus sp.) is a species of jellyfish with high relevance in artisanal fishing. Studies of their populations do not extend beyond the morphological descriptions knowing that presents a great morphological variability. However, there are no genetic studies to determine the number of independent populations, so microsatellite markers become a suitable option. Since there are no species-specific microsatellite loci, in this paper, 14 new microsatellite loci are characterized. Microsatellite loci were isolated de novo through next generation sequencing, by two runs on Illumina MiSeq. A total of 506,771,269 base pair were obtained, from which 142,616 were microsatellite loci, and 1546 of them could design primers. We tested 14 primer pairs on 32 individuals from Bahía de La Paz, Gulf of California. We observed low genetic variation among loci (mean number of alleles per locus = 4.33, mean observed heterozygosity 0.381, mean expected heterozygosity 0.501). These loci are the first ones described for the species and will be helpful to carry out genetic diversity and population genetics studies.