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ABSTRACT: Rhizostoma pulmo is one of the most abundant scyphomedusae along the Mediterranean coasts. To understand changes in the population densities
of the medusa stage and its relationship with the benthic stage, we describe all developmental stages from the life cycle
of R. pulmo, from the scyphistoma stage to young medusae reared in the laboratory. Mature scyphistomae showed a mean total body length
of 1.7mm and the average tentacle number was 16. Asexual reproduction occurred by lateral budding, podocyst and pedalocyst
production. Each strobila released up to 8 ephyrae that had a mean total body diameter of 3.5mm. Moreover, we also present
data on the temporal and spatial distribution of the species in the Catalan Sea and the coastal lagoon on Mar Menor (NW Mediterranean)
during the years 2007–2009. In the Catalan Sea, the presence of adult R. pulmo was recorded as extended along the whole coast, but most of the observation was concentrated in the central area; the highest
abundances were recorded during the months of July and August. The highest number of observations was detected in 2008 in
coincidence with the inter-annual variation observed in the Mar Menor lagoon.
Marine Biology 04/2012; 158(10):2247-2266. · 2.28 Impact Factor
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ABSTRACT: One of the main objectives of research on jellyfish is to determine their effects on the food web. They are voracious consumers
that have similar diets to those of zooplanktivorous fish, as well as eating microplankton and ichthyoplankton. Respiration
rates (RRs) can be used to estimate the amount of food needed to balance metabolism, and thereby estimate minimum ingestion.
We compiled RRs for scyphozoan medusae in three suborders (Semeaostomeae, Rhizostomeae, and Coronatae) to determine if a single
regression could relate RRs to mass for diverse scyphomedusan species. Temperature (7–30°C) was not a significant factor.
RRs versus wet weight (WW) regressions differed significantly for semeaostome and rhizostome medusae; however, RRs versus
carbon mass over five-orders of magnitude did not differ significantly among suborders. RRs were isometric against medusa
carbon mass, with data for all species scaling to the power 0.94. The scyphomedusa respiration rate (SRR) regression enables
estimation of RR for any scyphomedusa from its carbon mass. The error of the SRR regression was ±72%, which is small in comparison
with the 1,000-fold variation in field sampling. This predictive equation (RR in ml O2 d−1=83.37*gC0.940) can be used to estimate minimum ingestion by scyphomedusae without exhaustive collection of feeding data. In addition, effects
of confinement on RRs during incubation of medusae were tested. Large medusae incubated in small container volumes (CV) relative
to their size (ratios of CV:WW<50) had RRs ~one-tenth those of medusae in relatively larger containers. Depleted oxygen
during incubation did not depress RRs of the medusae; however, swimming may have been restricted and respiration reduced in
consequence. We briefly review other problems with RR experiments and suggest protocols and limitations for estimating ingestion
rates of jellyfish from metabolic rates.
KeywordsJellyfish-Metabolism-Zooplankton-Methods-Review-Aurelia-Rhizostoma-ETS
Hydrobiologia 04/2012; 645(1):135-152. · 1.78 Impact Factor
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ABSTRACT: Pelagic cnidarians are important consumers of zooplankton and ichthyoplankton in the world’s oceans, and thus harm fisheries
as competitors and predators of fish. This study examined the inshore-offshore distribution of pelagic cnidarians and the
trophic ecology of Pelagia noctiluca ephyrae (<12mm diameter) and larger medusae in late spring 1995 in the NW Mediterranean Sea. The distribution of pelagic
cnidarians was closely related to the presence of the shelf-slope front with most species mainly concentrated close to the
front. Meroplanktonic antho- and leptomedusae predominated in coastal waters and more holoplanktonic trachy- and narcomedusae
occurred both in shelf and open sea waters. P. noctiluca was more abundant than other medusae, including hydromedusae. Siphonophores, particularly Muggiaea atlantica, outnumbered medusae at most stations. The diet of P. noctiluca ephyrae contained mainly copepods, but ~12% of the prey were fish larvae. P. noctiluca exhibited positive prey selection for chaetognaths and mollusc larvae in day and night samples, but fish larvae were positively
selected only at night. These differences may be related to the diel vertical distributions of P. noctiluca and their prey. Most of the ingested fish larvae belonged to the family Myctophidae, but anchovy and sparid larvae also were
found in the gastric pouches. The size of ingested fish larvae increased as ephyra diameter increased; however, in the larger
medusae (>12mm) the number of prey increased with medusa size rather than the size of the larvae. The temporal and spatial
co-occurrence of P. noctiluca with early life stages of fish suggests that P. noctiluca may be an important predator on summer ichthyoplankton.
KeywordsJellyfish-Ichythyoplankton-Fish-Front-Siphonophore-Hydromedusae
Hydrobiologia 04/2012; 645(1):153-165. · 1.78 Impact Factor
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04/2011;
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ABSTRACT: Una medusa invasora Els estius del 2008 i el 2009 es va produir una pro-liferació sobtada de la cubomedusa Carybdea mar-supialis en algunes platges de la costa d'Alacant, especialment a la zona de Dénia. Les meduses petites (d'1 a 3 cm) van produir picades a més de 2.500 persones que es banyaven a les platges als mesos d'estiu. Alguns dies es van recollir fi ns a 260 individus per m 3 , una densitat mai conegu-da a la Mediterrània, on fi ns ara havia estat con-siderada una espècie ocasional. Carybdea marsupialis és una cubomedusa, del grup de meduses més tòxiques, d'uns 3 cm de mida màxima, en forma quadrada i amb quatre tentacles armats amb cnidoblasts, que una vegada desplegats arriben als 2 m de llargada. És una excel·lent nedadora, que busca la llum, mitjançant un sistema de fototaxi molt desenvolupat; a més, pot tenir un sistema visual sofisticat en forma d'ocels. Són excel·lents capturadores de preses del zooplàncton, entre les quals s'inclouen misida-cis i petits peixos. La seva picada és molt dolorosa per als humans, raó per la qual en algunes zones se la coneix com a vespa marina. L'espècie té un cicle de vida amb dues fases: la de medusa, pelàgica, i la de pòlip, sèssil. El pòlip es reprodueix asexualment i es transforma en una larva que ja té forma de petita medusa. Els pòlips romanen adherits al substrat tot l'any, mentre que les meduses apareixen a la columna d'aigua durant els mesos d'estiu, coincidint amb la pujada de la temperatura. La causa de la proliferació de Carybdea marsu-pialis és encara desconeguda, però es plantegen dues hipòtesis per a explicar-la. Una és l'arribada d'exemplars de pòlips amb les aigües de llast dels vaixells que vénen d'aigües tropicals atlàntiques, que és la zona geogràfi ca on predomina aquesta espècie. Una altra possibilitat és el transport pas-siu amb els corrents que pugen prop de la costa mediterrània de la península Ibèrica des de l'es-tret de Gibraltar. El fet que s'hagin establert a les platges de Dénia pot ser degut tant a factors cli-màtics i oceanogràfi cs locals com a la presència d'unes condicions del substrat que van permetre l'assentament de caràcter oportunista dels pòlips, que un cop fi xats es mengen les larves d'altres es-pècies de meduses i obtenen així un avantatge competitiu.
04/2010;
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ABSTRACT: L as analogías permiten comparar fenómenos en aparien-cia tan distintos como los que suceden en el medio terres-tre y el marino. Suele decirse que si no sentimos la necesidad de conservar los océanos es, en parte, porque no los conoce-mos. Si bien resulta difícil comprender un ambiente en el que no podemos vivir o habitar, sí podemos, mediante analogías, aproximarnos a lo desconocido. Sirva de ejemplo la siguiente comparación de procesos y fenómenos resultantes. La metamorfosis es un proceso singular en la vida animal. Corresponde al desarrollo del organismo, desde el nacimiento hasta la madurez, que se desarrolla a través de importantes cam-bios morfológicos, estructurales y fi siológicos. La metamorfosis confi ere a las especies una gran ventaja ecológica, puesto que les permite medrar en distintos hábitats a lo largo de su ciclo bioló-gico. Esa versatilidad favorece la exploración de hábitats más idóneos para la alimentación o la protección de los individuos. Curiosamente, los animales que han desarrollado procesos de metamorfosis son algunos de los que han tenido mayor éxito ecológico y evolutivo, lo mismo en ecosistemas terrestres (insec-tos) que en ecosistemas marinos (cnidarios).
04/2010;
