D-Methionine and gold chloride alleviate adverse eects of glutamate on motility of ephyrae of Aurelia aurita (Linnaeus, 1758) (Scyphozoa: Semaeostomeae)

Glutamate (MSG) causes low pulse numbers and swimming cessation in Aurelia jellyfish ephyrae. Ephyrae given MSG for 1 h and subsequently maintained in artificial sea water (ASW) were observed at 1, 3, 24, and 48 h intervals. Abnormality of motility was found at all post-treatment periods but some ephyrae resumed swimming and normal pulsing within 48 h. Swimming and pulsing were impaired in a significant number of ephyrae within 15 min of MSG treatment. The mechanism of MSG action on ephyrae motility is unknown, but glutamate damage to neurons and hair cells of higher animals is partly attributed to the formation of reactive oxygen species (ROS). Laser confocal fluorescent microscopy of ephyrae following MSG treatment indicated an increase of calcium and free radicals in the ephyrae as early as 5 min following MSG exposure. To determine whether antioxidants could alleviate MSG effects, we exposed ephyrae to gold chloride before, during, and after treatment with MSG. Ephyrae given gold chloride pre-treatment for 1 h and then transferred into gold chloride plus MSG for 1 h showed statistically significant recovery from MSG impairment of pulsing at the 3, 24, and 48 h post-glutamate time periods and higher numbers of swimmers at 3 h and 24 h. Ephyrae groups given gold plus MSG but without gold pretreatment showed recovery of swimming at 24 h and pulsing at 48 h. D-methionine given simultaneously with MSG significantly improved the pulse numbers and swimming of ephyrae at the 3, 24, and 48 h post-glutamate time periods compared to those receiving MSG alone. Both D-methionine and gold chloride accelerated the time of recovery from glutamate-induced motility impairment, possibly through their antioxidant activities.

Key words: jellyfish, pulsing, swimming