1. Review of Eastern Adriatic hydromedusae: unravelling two centuries of recordsIvona Onofri, Davor Lučić, Alenka Malej, Barbara Gangai, 2026, review article Abstract: The Eastern Adriatic Sea is biogeographically complex, yet knowledge of its hydromedusae is fragmented across two centuries of uneven sampling and shifting taxonomy. This review integrates historical faunistic records (pre-1950), mid-century programmes (1950–2000), modern quantitative time series (post-2000), and citizen science observations to compile an updated checklist of 98 non-siphonophoran hydrozoan taxa. Records are synthesised across eight sub-regions, although the most continuous research has focused on the Northern Adriatic and the open South Adriatic. The clearest long-term signal is in the Northern Adriatic, where diversity collapsed by >60% from the 1960s to the 1980s, largely through the loss of meroplanktonic taxa with benthic polyp stages under eutrophication-driven hypoxia. Since 2000, oligotrophication coincides with a partial recovery, marked by the re-emergence of meroplankton and episodic intrusions of oceanic holoplankton (including Trachymedusae) linked to circulation regimes (BiOS). For the open South Adriatic, bathymetric distributions and diel vertical migration patterns are synthesised to characterise a persistent offshore core. Taxonomic updates and information on non-indigenous and bloom-forming taxa are provided. Methodological biases and gaps, especially polyp-stage ecology and spatial sampling voids, are highlighted, and routine DNA barcoding is recommended. The checklist provides a baseline for tracking change in a shifting ecosystem.
Keywords: gelatinous zooplankton, ecological collapse and recovery, citizen science, meroplankton, taxonomic checklist
Published in DiRROS: 02.03.2026; Views: 394; Downloads: 268
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2. A short-term investigation of diel vertical migrations of the calycophoran Siphonophora in the open south Adriatic Sea (July 2003)Davor Lučić, Adam Benović, Mirna Batistić, Mira Morović, Ivona Onofri, Juan Carlos Molinero, Tjaša Kogovšek, Barbara Gangai, Marijana Miloslavić, 2011, original scientific article Abstract: Morning, midday, evening and night repetitive sampling was used to demonstrate calycophoran diel vertical migration (DVM) at a fixed station in the oligotrophic southern Adriatic Sea at 8 depth intervals. Of 20 calycophoran species collected, most of them inhabited layers of specific temperature and light intensity, and migrated during the night. The deep species Kephyes ovata is primarily non-migratory. Typical nocturnal movements to the surface were recorded for Lensia conoidea and sphaeronectes koellikeri. Lensia subtilis and eudoxoides spiralis migrated toward the surface in the evening but sank deeper at night. Lensia meteori and Lensia fowleri reached upper layers at midday. The DVM of sphaeronectes irregularis was irregular and independent of diel light patterns. Though low in numbers, some calycophorans were found above the thermocline at night. For mesopelagic species, however, higher summer surface temperatures proved an effective barrier to migration above 100 m. Thus, certain species could be represented as key species of planktonic cnidarian assemblages found within a certain depth range. Though not homogenous, and while some undertake nocturnal migrations in both directions, all are interrelated by preferences of bathymetric distribution and specific DVM behavior.
Keywords: sea, medusae, biological research, abundance, bathimetric distribution, siphonophora, calycophoran siphonophores, composition, Adriatic Sea
Published in DiRROS: 26.03.2025; Views: 1035; Downloads: 781
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3. Interannual size changes of adult Aurelia sp.5 medusae stage in the Marine protected Area of Mljet Island South AdriaticTjaša Kogovšek, Juan Carlos Molinero, Davor Lučić, Ivona Onofri, Barbara Gangai, Marijana Miloslavić, Delphine Bonnet, Alenka Malej, 2012, original scientific article Abstract: Aurelia aurita s.l. is the most widespread scyphozoan jellyfish that recurrently appear “en mass” and forms large aggregations mainly in coastal waters, embayments and estuaries. Beside anthropogenic factors controlling jellyfish populations climate change may play an important role. The aim of this study was to assess whether climate-related factors in absence of other anthropogenically induced stressor influence medusae size. We investigated seasonal and interannual changes in the size of Aurelia in a “jelly lake” in the National Park of Mljet Island (Croatia) where minimal human impact on the environment makes the Veliko Jezero a natural mesocosm for understanding the impact of climate change on the Aurelia population. The observed changes suggest Aurelia medusa population response to changing environment, in particular to enhanced temperature, by reduced body sizes. Comparison of Aurelia population dynamics from different regions in the Mediterranean Sea revealed the unique feature of the Veliko Jezero population. Despite the similarity of the environmental windows of medusae occurrences in the Veliko Jezero and regions in the Mediterranean Sea, medusae in the Veliko Jezero are present all year round. It seems that the lake bathymetry enables medusae to vertically migrate to deeper and cooler water layer, avoiding the limiting temperatures developed in the upper layer during the summer. These conditions may prolong the Aurelia medusae life span and together with continuous strobilation support the stability of the Aurelia medusae population all year round.
Keywords: Mediterraneum, moon jellyfish, Adriatic Sea, South Adriatic Sea, marine lakes, Aurelia spp, climate-related factor, Mediterranean Sea, marine research, population dynamics
Published in DiRROS: 05.08.2024; Views: 1360; Downloads: 737
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4. The lesser-known medusa Drymonema dalmatinum Haeckel 1880 (Scyphozoa, Discomedusae) in the Adriatic SeaAlenka Malej, Martin Vodopivec, Davor Lučić, Ivona Onofri, Branka Pestorić, 2014, original scientific article Abstract: Authors report historical and recent records of the little-known medusa Drymonema dalmatinum in the Adriatic
Sea. This large scyphomedusa, which may develop a bell diameter of more than 1 m, was fi rst described in 1880 by
Haeckel based on four specimens collected near the Dalmatian island Hvar. The paucity of this species records since
its description confi rms its rarity, however, in the last 15 years sightings of D. dalmatinum have been more frequent.
Keywords: scyphomedusae, historical occurrence, recent observations, Adriatic Sea
Published in DiRROS: 02.08.2024; Views: 1523; Downloads: 787
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