Spatial distribution of medusa Cunina octonaria and frequency of parasitic association with Liriope tetraphylla (Cnidaria: Hydrozoa: Trachylina) in temperate SW Atlantic waters

PUENTE TAPIA F; CASTIGLIONE; FAILHA; GENZANO

Zoological studies

Taiwan

Año: 2020 vol. 59 p. 57 - 60

1810-522X

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 alongthe Uruguayan and Argentine waters (34–56°S), which were placed in the Medusae collection ofthe Universidad Nacional de Mar del Plata, Argentina. In addition, we reported the peculiar parasiticassociation 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 aone-year sampling period (February 2014 to March 2015) in the coasts of Mar del Plata, Argentina. Weexamined the seasonality, prevalence, and intensity of parasitic infection. Metadata associated with themedusa 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. Theparasitic association was identified from the austral warm period (spring-summer season) until midautumn. 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 stolonsper host. Furthermore, the medusoid buds per stolon ranged from 11 and 29 at different stages ofdevelopment. No significant differences were observed between the umbrella diameter of parasitized andnon-parasitized L. tetraphylla specimens, nor was any significant correlation identified between umbrelladiameter and prevalence, and intensity of infection. According to the aggregation coefficient, C. octonariahad an overdispersed distribution in the host population. All parasitized hosts showed stomach vacuity dueto the location of the stolon, which blocked the mouth of the host. We identified the parasitic associationin the coasts of Mar del Plata, as well as in both coasts of the Río de la Plata Estuary (UruguayanArgentinean coasts). In the Southwestern Atlantic, several biological interactions between medusae andother groups have been identified; however, the specific host selectivity of C. octonaria for L. tetraphyllawas 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 spatialdistribution of this particular parasitic association in the Southwestern Atlantic, thus increasing theknowledge of biological associations of gelatinous zooplankton (Cnidaria and Ctenophora) on Uruguayanand Argentinean coasts.