IMIS

Four individuals of the large scyphozoan jellyfish Stygiomedusa gigantea were observed in the northern Gulf of Mexico over 2005 – 2009 by industrial remotely operated vehicles as part of the SERPENT Project. One of these observations included the symbiotic Bythitid fish Thalassobathia pelagica. Prior to these observations, neither S. gigantea nor T. pelagica had been observed in, or collected from the Gulf of Mexico. In order to summarize the available information on S. gigantea, we located 110 observations obtained over 110 years (1899 – 2009) representing 118 individual specimens of this species from around the world. The resulting dataset confirms that this species is cosmopolitan occurring with records from all Oceans except the Arctic. While the depth range of the four Gulf of Mexico specimens was bathypelagic, there appears to be a pattern of S. gigantea occurring in mesopelagic and epipelagic depth zones at high latitudes, particularly in the Southern Ocean and mesopelagic and bathypelagic depths at mid- and low-latitudes. This pattern may be related to the meridional vertical distribution of temperature or perhaps avoidance of light levels that could degrade porphyrin pigments. There was no evidence that this species migrates vertically. Two of the individuals in the Gulf of Mexico appeared to be actively clinging to subsea structures and we speculate that this is a consequence of its normal mode of feeding which may entail using its large oral lobes to hold on to, and trap prey.