ABSTRACT. The seasonal variability of gelatinous zooplankton (siphonophores, medusae, and thaliaceans) abundance was investigated at Cabo Pulmo National Park (CPNP) from weekly zooplankton samples collected throughout 2014. The Gulf of California had prolonged warming during 2009-2019, with 2014 as the anomalously warm year preceding El Niño 2015-2016 compared to the 2003-2020 SST time series. Gelatinous zooplankton accounted <1% of the entire zooplankton community abundance at CPNP during 2014, suggesting a low influence of predation pressure upon their zooplanktonic and micronekton preys. Siphonophores (57%), thaliaceans (42%), and medusae (1%) were present throughout the year. The abundance of gelatinous zooplankton had a significant negative association with sea surface temperature and a positive association with sea surface chlorophyll-a concentration and velocity and direction of the wind, increasing their abundance during October after the hurricane season. The gelatinous zooplankton species assemblage at the coastal CPNP was similar but less abundant than the gelatinous zooplankton species assemblage observed in the oceanic region of the southern Gulf of California during summer 2014. Tropical species Diphyes dispar, Abylopsis tetragona, Chelophyes contorta, and Thalia spp. numerically dominated the gelatinous zooplankton community associated with a regional heatwave period recorded during 2014. A high proportion of tropical zooplankton indicates that mesotrophic conditions sustain the current high biomass and diversity of nektonic and benthonic planktophagous fauna inhabiting CPNP. However, prolonged warming events might decrease zooplankton biomass in the southern region of the Gulf of California in the future.

Abstract Medusae are mainly a marine group belonged to cnidarians, which are characterized by specialized stinging cells, cnidocyts. Although all medusae are potentially poisonous, their toxicity depends on the species and the effects on humans vary- ing from mild local reactions to severe atopic-anaphylactic reactions, even the death of the victim. Numerous species of cnidar ians are known worldwide to affect humans, such as the sea wasp {Chironex fleckeri), the siphonophore portuguese man-of-war (Physaliaphysalis) or the fire-coral (Millepora spp.). In Argentina, three species of medusae are known with clinical epidemiological importance due to their stinging power: the hydromedusae Liriopetetraphylla and Olindias sambaquiensis, as well as the scypho- medusae Chrysaora lactea. These species have their highest abundances in the summer on Buenos Aires coasts, coinciding with the presence of tourists during the summer vacations. Its affectations vary from mild to moderate, registering from paresthesias and burning with dermatitis, itching, edemas, and erythema. An infinity of “home remedies” are known formedusae stings, how- ever, most of them have proven ineffective and harmful. It is best to avoid rubbing and washing the affected area with fresh water or applying ice to try to counteract the burning in the region and to go the health center as soon as possible.

Resumen Las medusas son organismos mayoritariamente marinos pertenecientes al grupo de los cnidarios, los cuales se caracterizan por presentar células urticantes especializadas, los cnidocitos. Si bien, todas las medusas son potencialmente venenosas y el grado de toxicidad depende de la especie, sus efectos sobre los humanos varían desde reacciones locales leves hasta reacciones atópicas-anafilácticas graves, llegando incluso a la muerte de la víctima. Mundialmente se conocen numerosas especies de medusas causantes de envenenamiento a humanos, tales como la avispa de mar (Chironex fleckeri), el sifonóforo carabela portuguesa (Physalia physalis) o el hidrocoral de fuego (Millepora spp.). En Argentina, tres especies de medusas revisten de im portancia clínica epidemiológica debido a su poder urticante: las hidromedusas Liriope tetraphylla y Olindias sambaquiensis, así como la escifomedusa Chrysaora lactea. Estas especies presentan sus mayores abundancias en el verano en las costas bonae renses, coincidiendo con la presencia de turistas durante el periodo vacacional. Sus afectaciones varían de leves a moderadas, registrándose desde parestesias y ardor con dermatitis, prurito, edemas y eritemas. Una infinidad de “remedios caseros” se conocen para remediar los efectos de las picaduras de medusas, sin embargo, la mayoría han resultado ineficaces y perjudiciales. Lo más recomendable es evitar frotar y lavar la zona afectada con agua dulce o aplicar hielo para tratar de contrarrestar el ardor y acudir lo antes posible al centro de salud más cercano.

ABSTRACT In this study, we reported the species composition and spatial distribution of Scyphomedusae and Cubomedusae from the southwestern Atlantic and Subantarctic region and reviewed the available knowledge of life history traits of these species. We gathered the literature records and presented new information collected from oceanographic and fishery surveys carried out between 1981 and 2017, encompassing an area of approximately 6,7 million km2 (32-60°S, 34-70°W). We confirmed the occurrence of 15 scyphozoans and 1 cubozoan species previously reported in the region. Lychnorhiza lucerna and Chrysaora lactea were the most numerous species, reaching the highest abundances/biomasses during summer/autumn period. Desmonema gaudichaudi, Chrysaora plocamia, and Periphylla periphylla were frequently observed in low abundances, reaching high numbers only occasionally. Phacellophora camtschatica, Aurelia sp., Drymonema gorgo, Atolla chuni, Stygiomedusa gigantea and Pelagia cf. noctiluca were observed always in low numbers. Atolla wyvillei, Stomolophus meleagris, Desmonema comatum and Tamoya haplonema were reported just a few times and mostly individually. Although new species/reports can be found as surveys are undertaken, these results are considered to be the reliable baseline for further ecological studies seeking to understand the ecological role that these jellyfish play in marine ecosystems.

We report the association between the jellyfish Lychnorhiza lucerna and the crab Cyrtograpsus affinis. Numerous examples of associations between medusae and brachyurans have been observed in the field and noted in the literature. All of these cases involve medusae of the Class Scyphozoa and crabs belonging to the families Majidae and Portunidae. The presence of three individuals of C. affinis within the subgenital space of L. lucerna constitutes a striking finding since none species of this brachyuran family (Varunidae) has been previously reported associated to scyphomedusae.

Se reporta la asociación entre la medusa Lychnorhiza lucerna y el cangrejo Cyrtograpsus affinis. Existen numerosos ejemplos de asociaciones entre medusas y brachiuros mencionados en la literatura. Todos ellos involucran a las medusas de la Clase Scyphozoa y a cangrejos pertenecientes a las familias Majidae y Portunidae. La presencia de tres individuos de C. affinis dentro de la cavidad subgenital de L. lucerna es un hecho llamativo dado que, hasta el momento, no se habia reportado a ninguna especie de esta familia de brachiuros (Varunidae) asociada con medusas de la Clase Scyphozoa.