Abstract
The pea crab Pinnotheres bicristatus lives in symbiosis with the saddle oyster Anomia ephippium. The first record in the Adriatic Sea dates to 2021, when one male specimen was observed in the Gulf of Trieste. This study reports additional findings from fouling samples collected in the port of Trieste as part of the Marine Strategy Framework Directive monitoring program. Seven specimens were identified based on morphological features, confirmed through CoxI DNA marker analysis, showing 100% similarity with GenBank reference sequences. This record represents the fourth occurrence of the species in the Mediterranean Sea and confirms its continued
presence in the Adriatic. Due to the identification challenges in pinnotherids, its small sizes and the fact that its host, the saddle oyster, has no commercial value, P. bicristatus presence could have gone unnoticed in the past and its real distribution could be more widespread, resembling those of its host.
References
Becker, C. (2010): European Pea Crabs – Taxonomy, Morphology and Host Ecology (Crustacea: Brachyura: Pinnotheridae). Johann Wolfgang Goethe Universität, Frankfurt, Germany, 180 pp.
Becker, C. & M. Türkay (2010): Taxonomy and morphology of European pea crabs (Crustacea: Brachyura: Pinnotheridae). J. Nat. Hist., 44(25-26), 1555-1575.
Cuesta, J.A., J.E. García Raso, P. Abelló, E. Marco-Herrero, L. Silva & P. Drake (2019): A new species of pea crab from southwestern Europe (Crustacea, Decapoda, Brachyura): Species distribution, geographic distribution and population structure with an identification key to European Pinnotheridae. J. Mar. Biol. Assoc. U.K., 99, 1141-1152.
Cuesta, J.A., S. Román, I. Muñoz, A. Rodríguez de la Rúa, C. Farías, L. Silva & M. Delgado (2024): Updated and corrected list of hosts of European pinnotherids (Crustacea, Decapoda, Pinnotheridae): Relationship between number of hosts and distribution. Diversity, 16, 470.
de Wulfen, F.X.L.B. (1791): Descriptiones zoologicae ad Adriatici littora maris concinnatae. Nova Acta Physico-Medica Academiae Caesareae Leopoldino-Carolinae Naturae Curiosorum, 8, 235-359.
Folmer, O., M. Black, W. Hoeh, R. Lutz & R. Vrijenhoek (1994): DNA primers for amplification of mitochondrial cytochrome c oxidase subunit I from diverse metazoan invertebrates. Mol. Mar. Biol. Biotechnol., 3(5), 294-299.
Marco-Herrero, E., E. Galimany, P. Abelló, J.A. Cuesta, P. Drake & M. Ramón (2020): Updating the hosts and distribution range of the pea crab Pinnotheres bicristatus (Brachyura: Pinnotheridae). Mediterr. Mar. Sci., 21(3), 499-505.
Mavrič, B. & A. Vrezec (2024): First record of Pinnotheres bicristatus García Raso & Cuesta, 2019 from the Adriatic Sea (Decapoda, Pinnotheridae). Spixiana, 47(1), 34.
MolluscaBase eds. (2025): MolluscaBase. Anomia ephippium Linnaeus, 1758. Available through the World Register of Marine Species at: https://www.marinespecies.org/aphia.php?p=taxdetails&id=138748 [Accessed 2 April 2025].
Ng, P.K.L., D. Guinot & P.J.F. Davie (2008): Systema Brachyurorum. Part I. An Annotated Checklist of Extant Brachyuran Crabs of the World. Raffles Bull. Zool., Suppl. 17, 286 pp.
Perez-Miguel, M., P. Drake, J.E. García Raso, L. Maman Menéndez, J.I. Navas & J.A. Cuesta (2019): European Pinnotheridae (Crustacea, Decapoda, Brachyura): Species, distribution, host use and DNA barcodes. Mar. Biodivers., 49, 57-68.
Schmitt, W.L., J.C. McCain & E.S. Davidson (1973): Decapoda I. Brachyura I, Pinnotheridae. Crustaceorum Catalogus, Pars 3. Junk, Den Haag, 160 pp.
Scopoli, J.A. (1763): Entomologia Carniolica Exhibens Insecta Carnioliae Indigena et Distributa in Ordines, Genera, Species, Varietates. Methodo Linnaeana. Typis Joannis Thomae Trattner, Vindobonae, 420 pp., 43 plates. https://doi.org/10.5962/bhl.title.34434.
Subida, M.D., A.M. Arias, P. Drake, J.E. García Raso, A. Rodríguez & J.A. Cuesta (2011): On the occurrence of Afropinnotheres monodi Manning, 1993 (Decapoda: Pinnotheridae) in European waters. J. Crustac. Biol., 31(2), 367-369.

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