Las medusas en los balnearios de la provincia de Buenos Aires / The jellyfish species in the coastal waters of Buenos Aires province

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 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.

Spatial Distribution of Medusa Cunina octonaria and Frequency of Parasitic Association with Liriope tetraphylla (Cnidaria: Hydrozoa: Trachylina) in Temperate Southwestern Atlantic Waters.

This study examined the spatial distribution of the medusae phase of Cunina octonaria (Narcomedusae) in temperate Southwestern Atlantic waters using a total of 3,288 zooplankton lots collected along the Uruguayan and Argentine waters (34-56°S), which were placed in the Medusae collection of the Universidad Nacional de Mar del Plata, Argentina. In addition, we reported the peculiar parasitic association between two hydrozoan species: the polypoid phase (stolon and medusoid buds) of C. octonaria (parasite) and the free-swimming medusa of Liriope tetraphylla (Limnomedusae) (host) over a one-year sampling period (February 2014 to March 2015) in the coasts of Mar del Plata, Argentina. We examined the seasonality, prevalence, and intensity of parasitic infection. Metadata associated with the medusa collection was also used to map areas of seasonality where such association was observed. Cunina octonaria was found from southern Uruguay to the coast of Mar del Plata (34.8-38.2°S, 57.2-54.0°W), with the highest abundances and frequency of occurrence in the Río de la Plata estuary. The parasitic association was identified from the austral warm period (spring-summer season) until mid-autumn. Out of the 21,734 L. tetraphylla specimens that were examined, 316 were parasitized (prevalence = 1.5%) exclusively in the manubrium and gastric peduncle, with an infection intensity of 1 to 2 stolons per host. Furthermore, the medusoid buds per stolon ranged from 11 and 29 at different stages of development. No significant differences were observed between the umbrella diameter of parasitized and non-parasitized L. tetraphylla specimens, nor was any significant correlation identified between umbrella diameter and prevalence, and intensity of infection. According to the aggregation coefficient, C. octonaria had an overdispersed distribution in the host population. All parasitized hosts showed stomach vacuity due to the location of the stolon, which blocked the mouth of the host. We identified the parasitic association in the coasts of Mar del Plata, as well as in both coasts of the Río de la Plata Estuary (Uruguayan-Argentinean coasts). In the Southwestern Atlantic, several biological interactions between medusae and other groups have been identified; however, the specific host selectivity of C. octonaria for L. tetraphylla was not previously identified. Here we discuss the ecological importance of this association during the holoplanktonic life history of the narcomedusae. Additionally, we report the southern limit of the spatial distribution of this particular parasitic association in the Southwestern Atlantic, thus increasing the knowledge of biological associations of gelatinous zooplankton (Cnidaria and Ctenophora) on Uruguayan and Argentinean coasts.