17The early ontogeny of scyphomedusae involves morphological and functional 18 transitions in body plans that affect the predators' propulsive and feeding strategies. We lucerna's feeding current speeds, copepods often fail to detect the predator's feeding 34 currents or inadvertently jump into medusan capture surfaces during failed escape 35 attempts. Consequently, the comparatively weak predator feeding currents successfully 36 capture a portion of the copepods encountered by swimming medusae. These results 37clarify the processes that enable rhizostome medusae to play key roles as consumers in 38 tropical and subtropical coastal environments.

We have compiled available records in the literature for medusozoan cnidarians and ctenophores of South America. New records of species are also included. Each entry (i.e., identified species or still as yet not determined species referred to as "sp." in the literature) includes a synonymy list for South America, taxonomical remarks, notes on habit, and information on geographical occurrence. We have listed 800 unique determined species, in 958 morphotype entries: 5 cubozoans, 905 hydrozoans, 25 scyphozoans, 3 staurozoans, and 20 ctenophores. Concerning nomenclatural and taxonomical decisions, two authors of this census (Miranda, T.P. & Marques, A.C.) propose Podocoryna quitus as a nomen novum for the junior homonym Hydractinia reticulata (Fraser, 1938a); Euphysa monotentaculata Zamponi, 1983b as a new junior synonym of Euphysa aurata Forbes, 1848; and Plumularia spiralis Milstein, 1976 as a new junior synonym of Plumularia setacea (Linnaeus, 1758). Finally, we also reassign Plumularia oligopyxis Kirchenpauer, 1876 as Kirchenpaueria oligopyxis (Kirchenpauer, 1876) and Sertularella margaritacea Allman, 1885 as Symplectoscyphus margaritaceus (Allman, 1885).

Human-induced stresses on the marine environment seem to favor some jellyfish species to the detriment of other competitors such as planktivorous fishes. In pristine ecosystems, trophic relationships among these consumers are poorly understood. We determined stable carbon and nitrogen isotope signatures of representative consumers in the relatively pristine ecosystem of the Cananéia Estuary, Brazil, in order to understand the food web structure. We described isotopic niche breadth, position, and overlaps between fish and jellyfish (including comb jelly) species. Most of the δ 13 C values suggest that phytoplankton is the major carbon source, especially for pelagic consumers. Sessile benthic invertebrates had enriched δ 13 C values, suggesting a contribution of microphytobenthic algae. Seasonal variation of values was significant only for 13 C, with different patterns for pelagic and benthic organisms. Isotopic niche breadth of some jellyfishes was wider than those of fish species of the same trophic group, possibly as a consequence of their broad diets. Isotopic niche overlaps of fish and jellyfish species were related to: (1) trophic diversity, since planktivorous species occupied niches distinct from macroinvertebrate/fish feeders; and (2) life stages, since isotopic niche partitioning pattern can change during species ontogeny. Replacement of declining populations of fish by jellyfish competitors probably depends on the pool of other compensatory species, as well as on reproductive, growth, and feeding performance of other consumers. Description of isotopic niches provides a general picture of trophic roles, interactions and the degree of functional redundancy among species, allowing an evaluation of possible directions of community shifts resulting from the removal or proliferation of keystone consumers.

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This study is the first faunistic inventory of hydromedusae from the inner continental shelf of Paraná State. We describe the composition of hydromedusae species, collected with bottom-trawl and Hensen nets, in campaigns carried out from 1997 to 2006. We analyzed 17,797 specimens from 578 samples, and provide descriptions, photographs, and information about the biology of the 22 species found. All species had previous records from the Brazilian coast; however, this is the first record of Bougainvillia frondosa, Ectopleura dumortieri, Cirrholovenia tetranema, Eucheilota maculata, Gossea brachymera, Solmaris corona, and Amphogona apsteini for the coast of Paraná. Most species are typical of tropical and subtropical coastal waters from the South Brazilian Bight. However, Turritopsis nutricula, Niobia dendrotentaculata, Solmaris corona, and Aglaura hemistoma are abundant in oceanic waters, and Olindias sambaquiensis and Solmaris corona are associated with colder waters (<20°C). The current number of species known for the state is 26. Additional collection effort is needed in regions not sampled in this work, such as bays and offshore waters.

The spatial and temporal variations of planktonic cnidarians were studied across the inner continental shelf (≤40 m) off the State of Paraná in southern Brazil. Monthly zooplankton samples were taken between November 1997 and March 1999 at five stations. The holoplanktonic Liriope tetraphylla and Muggiaea kochi dominated during the entire period, comprising .80% of the specimens. The coast-ocean gradient became evident due to a near-coastal (≤20 m) assemblage formed by L. tetraphylla, Solmaris corona and meroplanktonic medusae, and a distinct outer (25-40 m) assemblage formed by the medusae Corymorpha gracilis and Aglaura hemistoma and siphonophores. The estuarine runoff during warm rainy periods lowered the salinity (~30) at the inner stations (1, 2 and 3), providing appropriate conditions for the estuarine/ coastal species. Wind-driven onshore advection of outer-shelf species to the inner isobaths occurred from late autumn to winter, when the rainfall decreased and salinity increased (.35). Population peaks occurred in both summer and winter at the inner stations. For most species, the seasonal patterns were inconsistent with other studies conducted in the Southern Brazilian Bight, suggesting irregular and unpredictable seasonal distributions of abundance. Whereas in highlatitude ecosystems the dynamics of cnidarian populations follows the seasonal productivity cycle, here, complex hydrographic processes seem to be more important in determining the structure and seasonal dynamics of this community.

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