In Situ Observations of Stygiomedusa Gigantea in the Gulf of Mexico with a Review of Its Global Distribution and Habitat Mark C

Journal of the Marine Biological Association of the United Kingdom, 2010, 90(6), 1079–1093. # Marine Biological Association of the United Kingdom, 2010 doi:10.1017/S0025315410000536 In situ observations of Stygiomedusa gigantea in the Gulf of Mexico with a review of its global distribution and habitat mark c. benfield1 and william m. graham2 1Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA 70803, USA, 2Dauphin Island Sea Laboratory and University of South Alabama, Dauphin Island, AL 36528, USA 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. Keywords: Scyphozoa, Stygiomedusa gigantea, Thalassobathia pelagica, behaviour, SERPENT, remotely operated vehicle, distribution, abundance Submitted 15 October 2009; accepted 4 February 2010; first published online 30 June 2010 INTRODUCTION industrial remotely operated vehicles (ROVs) and other industry resources. Technological advances in deep-sea dril- Gelatinous macroplankton including cnidarian medusae, cte- ling combined with an increasing demand for petroleum has nophores and pelagic tunicates are widely recognized as key stimulated exploration and production in the Gulf of ecosystem consumers of energy and nutrients in coastal eco- Mexico (Gulf), USA beyond the continental shelf. Moreover, systems (Pauly et al., 2009; Purcell, 2009), and recent evidence the presence of large numbers of drillships, rigs and other of increasing occurrence and magnitude of these ‘jellies’ has structures, equipped with ROVs capable of working to generated considerable concern (e.g. Graham, 2001; Brodeur 3000–4000 m, has provided a unique opportunity to study et al., 2008; Richardson et al., 2009). This, however, is a marine life in the mesopelagic and upper bathypelagic zones product of human interactions with largely bloom-forming of the Gulf without the additional cost of operating expensive nuisance species around populated shallow coastal seas. In equipment and ships simply for observational purposes. fact, these animals occupy all regions of the world’s In 2005 SERPENT began a regional programme (Gulf oceans—Arctic to Antarctic, surface to abyss—and are SERPENT) to study planktonic and nektonic marine organ- among the most conspicuous organisms of the deep mesope- isms in the Gulf. In addition to conducting dedicated lagic and bathypelagic realms (e.g. Robison, 2004). surveys for marine life with the ROVs, operators were encour- Observational information on these comparatively inaccess- aged to document any chance encounters with potentially ible animals is limited by technology and cost, thus basic dis- interesting marine organisms. tributional data are lacking from the largest habitable space (in In this paper we report four observations of the primarily terms of volume) on Earth due solely to absence of coverage. deep-distributed medusa Stygiomedusa gigantea (Browne, The SERPENT Project (www.serpentproject.com) is a 1910; Cnidaria: Scyphozoa: Semaeostomeae) conducted from global collaboration between academia and the petroleum industrial ROVs participating in the Gulf SERPENT project. industry designed to facilitate scientific research using Collectively these four observations constitute the first records of S. gigantea from the Gulf. In addition to our data on the distributions and behaviour of S. gigantea in the Corresponding author: Gulf, we have attempted to summarize all worldwide available M.C. Benfield records of the distribution of this large medusa in order to Email: mbenfi[email protected] synthesize what is currently known of its habitat and ecology. 1079 Downloaded from https://www.cambridge.org/core. University of Athens, on 30 Sep 2021 at 12:26:31, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0025315410000536 1080 mark c. benfield and william m. graham The class Semaeostomeae contains the largest known Species specimen search and search engines linked to individ- scyphomedusan genera including the genus Stygiomedusa. ual collections. On-line cruise reports from the Mar-Eco Members of this genus are characterized by a large disc surveys of the Mid-Atlantic Ridge, Discovery 2010 and shaped bell with four oral-arms and dark red-brown color- GLOBEC Southern Ocean Program were also searched for ation (Kramp, 1961). One species S. gigantea Browne, 1910 references to S. gigantea. Larson (1986) was used to locate is currently recognized in this genus (Matsumoto et al., collections or observations from early expeditions to the 2003), and earlier descriptions of S. fabulosa Russell 1959 Southern Ocean, including the cruises of the USNS ‘Eltanin’. and S. stauchi Repelin, 1967 are considered synonyms. Additional metadata from the ‘Eltanin’ cruise stations were Stygiomedusa is one of, if not the largest, invertebrate pred- obtained from the University of Southern California (1965). ator in many deep-sea ecosystems, yet very little is known Video libraries at the Monterey Bay Aquarium Research about its distribution, diet, environmental tolerances, or Institute (MBARI) were searched using the Video behaviour. The majority of published S. gigantea records are Annotation and Reference System (VARS) for S. gigantea. from trawl or net samples. Direct observations of this large For every record we attempted to determine the collection jellyfish from submersibles and ROVs are infrequent depth, geographical coordinates, dates and times. All times (Vinogradov & Shushkina, 2002; Drazen & Robison, 2004; recorded as GMT were converted to local times using Kitamura et al., 2008). Specimens have been collected from, the US Naval Observatory website (http://www.usno.navy. or observed in, the North Atlantic Ocean (Harbison et al., mil/USNO/astronomical-applications/data-services/rs-one-day- 1973), South Atlantic Ocean (Repelin, 1967), Southern world). In cases where the collection depth was a range, the Ocean (Larson, 1986; Piatkowski et al., 1994; Torres et al., mean was used as an estimate of collection depth. The 2002; EGS-SCAR, 2006), the Gulf of California (Drazen & entire dataset was submitted to OBIS. Robison, 2004) and the North Pacific (Burd & Thompson To evaluate evidence of S. gigantea vertical migration, we 2000; and possibly Vinogradov & Shushkina, 2002). There calculated the time elapsed since local sunrise or sunset for do not appear to be any published records of its existence in each observation and used this to assign observations to the Gulf of Mexico. Given the connection between the Gulf either day or night. In cases where there was continuous day- and the Atlantic, it is reasonable to suppose that S. gigantea light, observations were assigned to daytime irrespective of is present within the mesopelagic and upper bathypelagic their time of day. To compare the vertical distributions over regions of the Gulf. the entire latitudinal range of the observations in the dataset, we normalized the depths by dividing the observed depth (or mean of a depth-range) by the bottom depth. If MATERIALS AND METHODS an observation included the bottom depth we used the original data, otherwise we estimated the bottom depth using Observations of Stygiomedusa gigantea were provided by GeoMapApp software (www.geomapapp.org), which accesses industrial ROV teams participating in the Gulf SERPENT global bathymetry data with 30 × 30 arcsec resolution (Becker project. Each observation was the result of an opportunistic et al., 2009). In the few cases where the predicted bottom encounter where S. gigantea was observed during the course depth was less than the recorded maximum sampling depth, of routine industrial work. Participating ROVs were each we used the maximum sampling depth as an estimate of the equipped with an analogue colour video camera capable of bottom depth. In order to examine the temperature and sal- transmitting NTSC video with a resolution of approximately inity ranges of S. gigantea, we used a subset of the dataset 480 horizontal scan lines by 640 vertical scan lines. Video that included the temperature and salinity associated with was transmitted to the

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