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Biological, Biochemical and Elemental Traits of Clavelina oblonga, an Invasive Tunicate in the Adriatic Sea
by
, , , , , , , , , and
Natalija Topić Popović
1
,
Bojan Hamer
2,*,
Ivančica Strunjak-Perović
1,
Tibor Janči
3,
Željka Fiket
4,
Matilda Mali
5,
Luca Privileggio
2,
Kristina Grozić
2,
Dijana Pavičić-Hamer
2,
Lucija Vranjković
1,
Tamara Vujović
1,
Marija Miloš
1,
Maria Michela Dell’Anna
5
,
Darya Nefedova
5 and
Rozelindra Čož-Rakovac
1 
1
Laboratory for Aquaculture Biotechnology, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia
2
Laboratory for Marine Nanotechnology and Biotechnology, Center for Marine Research, Ruđer Bošković Institute, Giordano Paliaga 5, 52210 Rovinj, Croatia
3
Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, 10000 Zagreb, Croatia
4
Laboratory for Inorganic Environmental Geochemistry and Chemodynamics of Nanoparticles, Ruđer Bošković Institute, Bijenička 54, 10000 Zagreb, Croatia
5
Department of Civil, Environmental, Land, Building Engineering and Chemistry, Polytechnic University of Bari, Via E. Orabona 4, 70126 Bari, Italy
*
Author to whom correspondence should be addressed.
Animals 2025, 15(10), 1371; https://doi.org/10.3390/ani15101371
Submission received: 21 January 2025
/
Revised: 23 April 2025
/
Accepted: 7 May 2025
/
Published: 9 May 2025
Simple Summary
Clavelina oblonga is a non-native marine organism that was recently introduced into the Adriatic Sea. The spread of this species, which belongs to a group of animals called ascidian tunicates, in new areas is likely related to human activities and climate change. C. oblonga proliferates and grows rapidly in mariculture areas where mussels are cultivated on culture ropes. In such areas, it has become one of the most common biofouling species, attaching itself to mussels and other man-made surfaces. This study examined its biological and biochemical properties by analyzing its moisture content, fatty acids, minerals, and some less common elements. The results of this study showed that C. oblonga contains different levels of certain toxic metals, such as arsenic and lead, when compared to mussels that it overgrows. On-site observations indicate that C. oblonga has adapted to the colder temperatures of the northern Adriatic Sea and may continue to spread, potentially disrupting shellfish farming, reducing plankton populations, and altering marine ecosystems. The large quantities of biomass produced by this species could be used in various industries, making it essential to understand the overall characteristics of C. oblonga for that purpose.
Abstract
Clavelina oblonga is an invasive tropical tunicate recently introduced into the Adriatic Sea as a consequence of globalization and climate change. Mussel aquaculture sites provide an ideal environment for this colonial ascidian, where it has recently become the dominant fouling species. This study represents the first investigation of its biological and physical characteristics, as well as its proximal, fatty acid, macroelement, trace element, and toxic metal composition. The entire-tissue chemical composition of C. oblonga resulted in 95.44% moisture. Its composite structure revealed several strong peaks, attributed to O-H, C-H, C-N, and C=O stretching, along with cellulose components overlapping with proteins and carbohydrates. The major fatty acids were palmitic, stearic, and docosahexaenoic acid, followed by docosanoic, elaidic, linoleic, and myristic acid. The saturated fatty acids, polyunsaturated fatty acids, and monounsaturated fatty acids comprised 51.37, 26.96, and 15.41% of the total fatty acids, respectively. Among the analysed trace and macroelements, aluminium and sodium were predominant. C. oblonga exhibited different concentrations of toxic metals, such as arsenic and lead, compared to fouled mussels in the Istria region. It appears that the tunicate has adapted to the environmental conditions of the Adriatic, reaching its maximum spread and biomass in mid-autumn. There is a strong possibility that C. oblonga could colonize and establish itself permanently in the Adriatic. This would have a strong negative impact on shellfish farming, the structure of the ecosystem, plankton biomass, and the distribution of other marine species. However, it also represents a biomass resource with high potential of utilization in different industries.
