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(3060) Proposal to conserve the names Dinopyxis compressa , Exuviaella compressa , and Prorocentrum compressum ( Dinophyceae ) with a conserved type

2025; Wiley; Linguagem: Inglês

10.1002/tax.13301

1996-8175

Fernando Gómez,

Marine and coastal plant biology

(3060) Prorocentrum compressum (F. Stein) T.H. Abé ex J.D. Dodge in Bot. J. Linn. Soc. 71: 110. Sep 1975 ≡ Exuviaella compressa (F. Stein) Lauterborn (in Wiss. Meeresuntersuch. 1(1): 208. 1896 ≡ Dinopyxis compressa F. Stein, Organism. Infusionsthiere 3(2): expl. t. 1, fig. 34–38. Nov 1883, nom. cons. prop. Typus: [icon in] Stein, Organism. Infusionsthiere 3(2): t. 1, fig. 37. Nov 1883, typ. cons. prop. Epitypus (hic designatus): preserved material from L. Rhodes (dep. 2 Oct 1997 as CCMP1786) gathered at Ninety Mile Beach, Northland, New Zealand, 34°43′15″S, 172°55′20″E, 1995, Rhodes [specimen ex strain CCMP1786] (National Center for Marine Algae and Microbiota, East Boothbay, Maine, U.S.A.). Stein proposed the new combination Dinopyxis compressa (Bailey) F. Stein in Organism. Infusionsthiere 3(2): expl. t. 1, fig. 34–38. 1883, ≡ Exuviaella compressa (Bailey) Lauterborn (in Wiss. Meeresuntersuch. 1(1): 208. 1896), ≡ Prorocentrum compressum (Bailey) T.H. Abé ex J.D. Dodge (in Bot. J. Linn. Soc. 71: 110. 1975). Stein (l.c.) cited as basionym Pyxidicula compressa Bailey (in Smithsonian Contr. Knowl. 2(8): 40, t. 2: fig. 13, 14. 1851). Stein (l.c.: 18) interpreted Bailey's Pyxidicula compressa as a planktonic dinoflagellate rather than a benthic diatom. As explained by Cowan & Huisman (in Taxon 64: 809–810. 2015), Pyxidicula compressa is considered to be a diatom (currently known as Tryblionella compressa (Bailey) M. Poulin), while Stein (l.c.) illustrated dinoflagellates. Cowan & Huisman reported "The dinoflagellate presently known as Prorocentrum compressum therefore requires a new name", and they concluded: "Three of these (Prorocentrum bidens, Prorocentrum lebouriae, Exuviaella oblonga) were described by Schiller in 1928 from the Adriatic and represent the earliest available names. Since these are of equal priority, we propose adopting the name P. bidens for this taxon, as Schiller himself later regarded his P. bidens as conspecific with P. compressum (noted by Dodge, 1975: 111)." Most authors continue to use Prorocentrum compressum for the dinoflagellate illustrated by Stein. For example, Alabarces Álvarez & al. (Harmful Algae 118: 102318. 2022) reported "It should be noted that P. compressum has been renamed for nomenclatural reasons and therefore the name Prorocentrum bidens J. Schiller should be adopted (Cowan and Huisman, 2015). As this has not yet widely been recognized, the more familiar name has been retained herein." The placement of a species of the dinoflagellate genus Prorocentrum as a diatom causes confusion. For example, DNA sequences of the dinoflagellate P. compressum are classified as a diatom in GenBank (accession numbers AY259169, EU196417, EU927558, KU999989, MK050528). The identity of the dinoflagellate P. compressum has been recently re-investigated (Gómez & al. in J. Eukaryot. Microbiol. 71: e13039. 2024; Tillmann & al. in Phycologia 63: 431–452. 2024). Gómez & al. (l.c.) used Prorocentrum compressum auct. mult. because they do not consider P. bidens as a synonym. Tillmann & al. (l.c.: 446) reported "The length of P. bidens described in the protologue (Schiller, 1928) is distinctly smaller (i.e. 20 μm) than the c. 30–40 μm otherwise reported for P. compressum (Dodge, 1982). Notably, the small size did not matter anymore at all when Schiller synonymized P. bidens under E. compressa, for which a length of 34–46 μm but not shorter was provided (Schiller, 1933). Moreover, P. bidens is asymmetrically compressed laterally (i.e. less apically and more antapically; Schiller, 1928), which has never been reported for cells of P. compressum. Material from the type locality of P. bidens (Adriatic Sea) should be studied for an ultimate taxonomic clarification but until this time, we follow Cowan & Huisman (2015) to adopt the name P. bidens for the species formerly known as P. compressum." From the Adriatic Sea, Schiller illustrated Exuviaella compressa, and he described the new species Prorocentrum bidens (in Arch. Protistenk. 61: 61, text-fig. 21. 1928). Both species have a distinct size and shape, and Schiller placed them in separate genera. The type locality, the northern and central Adriatic Sea, has a long tradition of phytoplankton taxonomic studies, and species of the genus Prorocentrum, which contain harmful species, receive especial interest in monitoring surveys. To my knowledge, after almost a century, no study has reported P. bidens. There are polymorphic species that commonly proliferate in the Adriatic Sea, such as P. cordatum or even P. shikokuense, with a shape and size similar to P. bidens. The dinoflagellate Prorocentrum compressum is widely distributed worldwide. Molecular and morphological data from different oceanic regions (North and South Atlantic, Black Sea, Tasmania, New Zealand) showed similar DNA sequences, and these documented sequences reported cells around 40 μm long, with a broad oval shape and characteristic reticulate-foveate thecal surface, while P. bidens is 20 μm long with a narrow oval shape and without any especial thecal ornamentation. Unambiguously, P. compressum and P. bidens are independent species. Stein's figure 37 of Dinopyxis compressa represents the concept of the dinoflagellate known as P. compressum. Selecting this figure as the conserved type will avoid discussions. Epitypification from material collected at the type locality is recommendable. Stein (l.c.) reported that the individuals were collected from an undetermined location in either the Mediterranean Sea or the Pacific Ocean, an area representing approximately one-third of the Earth's surface. The dinoflagellate Prorocentrum compressum is commonly reported in the Mediterranean Sea (Gómez in Bot. Mar. 46: 231. 2003) and the Black Sea (Gómez & Boicenco in Hydrobiologia 517: 50. 2004). The strain CCMP1786 of P. compressum available at the National Center for Marine Algae and Microbiota (https://ncma.bigelow.org/CCMP1786) was isolated by Dr. L. Rhodes in New Zealand, Pacific Ocean, in 1995. The strain is barcoded in GenBank (EU927558, EU916911). The nuclear ribosomal internal transcribed spacer (ITS) region is one of the preferred genetic markers for barcoding dinoflagellate species. The ITS region sequence of the strain CCMP1786 (EU927558) and the strain BS4-A6 (OQ518920) from Bulgaria in the Black Sea, near the connection with the Mediterranean Sea, are 100% identical. This demonstrates that the same species inhabits distant regions. Molecular data from other P. compressum strains reveal that the species is distributed worldwide, as reported in Gómez & al. (l.c.) and Tillmann & al. (l.c.). The morphology of the strain CCMP1786 is illustrated in Gómez & al. (l.c.: fig. 4, 8b). The shape and thecal ornamentation in Stein's figure 37 fit well with the strain CCMP1786. This strain is publicly available (https://ncma.bigelow.org/CCMP1786), and preserved material has been deposited in that institution. Therefore, the strain CCMP1786 is proposed as epitype of Dinopyxis compressa F. Stein. In the current taxonomic schemes, Exuviaella Cienk. 1881 and Dinopyxis F. Stein 1883 are considered junior synonyms of Prorocentrum Ehrenb. 1834. All subsequent references consider that Ostenfeld (in Knudsen & Ostenfeld, Iagtt. Overflad. Temp. Salthold. og Plankton 1898: 59. 1899) proposed the new combination Exuviaella compressa, citing as synonyms Pyxidicula compressa Bailey and "Dinopyxis compressa Stein". However, the combination was actually first mentioned by Bütschli (Bronn's Kl. Ordn. Thier-Reichs 1: 1029. 1885) in stating his disagreement with Stein's (l.c.: 18) suggestion that Pyxidicula compressa Bailey and P. prisca Ehrenb. might be the same species but (mistakenly?) representing Bailey's taxon as "Exuviaella compressa Bailey (= Dinopyxis compressa Stein)". From this it is neither clear whether this was an unintentional error or that he was accepting this name as valid. Later the combination was clearly validly published by Lauterborn (in Wiss. Meeresuntersuch. 1(1): 208. 1896), listing it as "Exuviaella (Dinopyxis) compressa Stein spec. (Stein Taf. I Fig. 34–38.)" under Exuviaella Cienk., but without explicit exclusion of Stein's type, Pyxidicula compressa. Paulsen (in Brandt & Apstein, Nordisches Plankton. Botanischer Teil 8(18): 6. 1908) questioned Pyxidicula compressa as a synonym of the dinoflagellate Exuviaella compressa. Schiller (in Rabenh. Krypt.-Fl., ed. 2, 10(3), Dinoflagellatae (Peridineae) 1: 17. 1933) reported the dinoflagellate as "Exuviaella compressa Ostenfeld", and he also questioned the synonymy with Pyxidicula compressa. Abé (in Publ. Seto Mar. Biol. Lab. 14: 372. 1967), employing zoological nomenclature, used the new combination "Prorocentrum compressum (Ostenfeld)", citing as synonyms "Exuviaella compressa Ostenfeld 1889" and "Dinopyxis compressa Stein 1883, Pl. 1, Fig. 34". Although Abé (l.c.) did not cite the figure 37 by Stein (l.c.), his illustrations of P. compressum fit well with that figure. However, under the International Code of Zoological Nomenclature (Ride & al., ICZN, ed. 4. 1999), for which the concept of a new combination has no standing as an independent name, what Abé published was a subsequent usage of Bailey's original concept, to be cited as "Prorocentrum compressum (Bailey, 1851)", not a stand-alone name and not a name that Abé (l.c.) made available, as his was not the original publication in the sense of ICZN Art. 10.5. It seems best to consider that Abé's "name" would not have status under the ICZN necessary to be considered validly published under ICN Art. 45.1 (Turland & al. in Regnum Veg. 159. 2018), nor would it be validly published either as a new combination, lacking a full and direct reference to the basionym, Pyxidicula compressa, of both names Abé cited (Art. 41.5), or as the name of a new taxon, lacking both a type indication and a Latin description/diagnosis or reference to one (Art. 40.1, 44.1), all of which would make it ineligible for conservation. The first unequivocal validation of the name Prorocentrum compressum under ICN rules was therefore Dodge (in Bot. J. Linn. Soc. 71: 110. 1975), citing as synonyms Pyxidicula compressa Bailey and 'Exuviaella compressa Ostenfeld 1899' with page references to full citations in the bibliography, although not citing Dinopyxis compressa. Stein (l.c.) often cited basionyms that were unrelated to his descriptions, and in one case this has been solved by selecting one of his illustrations as a conserved type (Proposal 2608; Carbonell-Moore in Taxon 67: 633–635. 2018). Therefore, to avoid further confusion, I propose to conserve the name Dinopyxis compressa (Dinophyceae) with Stein's t. 1, fig. 37 as a conserved type and as basionym for the homotypic combinations Exuviaella compressa (F. Stein) Lauterborn and Prorocentrum compressum (F. Stein) T.H. Abé ex J.D. Dodge. I thank Dr. John Wiersema and Prof. John McNeill for improving the manuscript, Dr. Francisco Welter-Schultes for comments on zoological nomenclature, and Mark Hurd (Bigelow Laboratory for Ocean Sciences) for epitype conservation.