Scyphozoa Pelagia noctiluca (Forsskal, 1775): blooming on the coast of Gujarat, India and its predation by Anemonia viridis (Forsskal, 1775)

The jellyfish bloom, i.e. the aggregation of Pelagia noctiluca, which occurred in January 2016 along the Shivrajpur coast facing the Arabian Sea, is reported. The jellyfish population was studied based on the Pelagia noctiluca individuals that were stranded in low tide pools and those that were washed ashore. Transects were laid to collect data on the jellyfish density. The oceanographic and physicochemical parameters at the time of bloom were studied. The probability of correlation between the time of bloom and the movement of P. noctiluca was considered. Additionally, mating and predation on the species were documented. We assume that the jellyfish bloom might have drifted to this coast due to the landlocked characteristics of the Arabian Sea and northward movements of sea currents. So far, jellyfish has been known to be the dietary preference of several vertebrate predators. Here, we report an interesting event of Anemonia viridis feeding on Pelagia noctiluca during their blooms in several intertidal pools on the coast.

Seasonal variability of the fatty acid composition in Aurelia aurita (Cnidaria: Scyphozoa): implications for gelativore food web studies

Jellyfish population play an important role in aquatic food chains, and many animals predate on this ‘mostly water containing’ organisms. However, what gelativores predators could gain from their prey is still poorly understood. This study provides insight into the nutritional value of the moon jelly (Aurelia aurita) by means of its fatty acid (FA) composition, while investigating seasonal variability and differences between its free-swimming life stages. A biweekly sampling was carried out in a temperate coastal ecosystem, the Kiel Fjord, Germany and during two consecutive years. FA profile of A. aurita showed significant seasonal variability, while mature medusae (due to reproductive tissues) possessed highest FA content. In addition, moon jelly contained several essential FAs (i.e. arachidonic acid, 20:4ω6; eicosapentaenoic acid, 20:5ω3; docosahexaenoic acid, 22:6ω3), which likely support predator’s vital physiological functions. Even though total FA contents proved to be low (7 × 10−3–34 × 10−3% per g dry weight), evidence supporting A. aurita’s capability to meet the dietary requirements of predators such as fish and crustaceans is provided. Finally, implications for gelativore and future food web configurations are discussed, while proposing that jellyfish are likely to be, and become, more than an opportunistic prey to many organisms.

Inclusion of jellyfish in 30+ years of Ecopath with Ecosim models

A review of the functional role of jellyfish in Ecopath with Ecosim (EwE) models by Pauly et al. [Pauly, D., Graham, W., Libralato, S., Morissette, L., and Deng Palomares, M. L. 2009. Jellyfish in ecosystems, online databases, and ecosystem models. Hydrobiologia, 616: 67–85.] a decade ago concluded that recreation of jellyfish population dynamics in models required additional ecological research and the careful consideration of their unique biology during model construction. Here, amidst calls for ecosystem-based management and the growing recognition of jellyfishes' role in foodwebs, we investigate how jellyfish are implemented in EwE models and identify areas requiring improvement. Over time, an increasing percentage of models have included jellyfish. Jellyfish were often linked to the wider ecosystem, with many predators and prey included in models. However, ecotrophic efficiency, a measure of the extent to which they are used by higher trophic levels, was frequently set at low values, suggesting that jellyfish are still perceived as under-utilized components of the ecosystem. Moving forward, greater care should be taken to differentiate the functional roles played by ctenophores, cnidarians, and pelagic tunicates. Additionally, when feasible, early life stages should be incorporated as multi-stanza groups to more accurately depict jellyfishes' complex life cycle.

Bacteria associated with jellyfish during bloom and post-bloom periods

This study is the first to investigate bacterial community associated with live medusaAurelia sp. in the Gulf of Trieste (northern Adriatic Sea) using both culture independent and culture-based methods. We have analysed bacterial community composition of different body parts of medusa: exumbrella surface, oral arms (‘outer’ body parts) and of gastric cavity (‘inner’ body part) and investigated possible differences in medusa associated bacterial community structure at the time of jellyfish population peak and during senescent phase at the end of bloom, when jellyfish start to decay. Based on 16S rRNA clone libraries and denaturing gradient gel electrophoresis (DGGE) analysis, we demonstrated significant difference between bacterial community associated withAureliaand the ambient seawater bacterial assemblage. Comparing bacterial community composition between differentAureliamedusa body parts, communities differed significantly, especially the one within the gastral cavity. The pronounced difference is dominance ofBetaproteobacteria(Burkholderia, CupriavidusandAchromobacter) in gastral cavity of medusa andAlpha- (Phaeobacter, Ruegeria) andGamma-proteobacteria(Stenotrophomonas, Alteromonas, PseudoalteromonasandVibrio) on ‘outer’ body parts. This suggests that body-part specific bacterial association might have an important functional roles for the host. The results of bacterial isolates showed the dominance ofGammaproeteobacteria, especiallyVibrioandPseudoalteromonasin all body parts. Finally, comparison of medusa associated bacterial community structure, at the time of jellyfish population peak and during senescent phase at the end of bloom showed increased abundance ofGammaproteobacteria, especiallyVibrio. Our results suggest members ofVibriogroup are possible commensal opportunistic visitors, later becoming consumer of moribund jellyfish biomass and that the structure of jellyfish bacterial community might be affected by anthropogenic pollution in the marine environment.

Of jellyfish, fish, and humans

This paper follows my journey from childhood in Missouri, where I saw my first jellyfish, to the oceans of the world. Pelagic cnidarians and ctenophores (“jellies”) have been the focus of my career. I think my work has been relevant to the broader scientific community because jellies are predators and potential competitors of fish. In my early research, I quantitatively estimated the predation effects of jellies on zooplankton and ichthyoplankton. I found that most jellies are selective predators, with a few species having diets of only fish larvae or soft-bodied prey. As I learned more about the physical environment that jellies encounter, my early reductionist approach evolved into a more holistic approach. I thought the asexual multiplication from the attached polyp stage would be fundamental in determining jellyfish population size and that the effects of environmental variables could be tested experimentally. It also seemed that humans have changed the natural environment in ways favoring jellies over fish and jelly populations may have increased in developed, eutrophic, hypoxic, overfished, and warming coastal waters. Many opportunities were available that gave me a global perspective. I have persisted despite some difficulties because I love to learn and I am still having fun!

The hydroid and early medusa stage ofOlindias formosus(Cnidaria, Hydrozoa, Limnomedusae)

Olindiasspp. medusae are found worldwide in sublittoral tropical and sub-tropical coastal regions; their occurrence near shore can result in human envenomation events. While behaviour of medusae and human contact with medusae has been documented for the genus, the hydroid (polyp) phase of theOlindiaslife cycle has eluded investigators for over a century. Given the recent debate among public media and scientific communities that jellyfish blooms are increasing worldwide, there is a growing urgency to understand how and why jellyfish populations bloom. In order to understand jellyfish population dynamics, the asexual benthic phase must be studied to determine when, where, and how juvenile medusae are produced. In this study, husbandry management strategies, including the creation of artificial habitat forOlindias formosusmedusae in aquaria were developed to encourage spawning and larval settlement. The resultant hydroid colony ofOlindias formosuswas discovered in November of 2012, utilizing the natural fluorescence of the medusa as a detection method. A description of the hydroid and early medusa stage is presented. These techniques provide a basis for locatingin situthe benthic hydroid phases within this genus and other fluorescent medusae, the discovery of which may lead to a better understanding of the causative factors for jellyfish blooms.