Current IF 1.5
Latest issue (RSS 2.0)
Contact Editorial Office at
bulletin@geology.cz
Bulletin of Geosciences
Published by ©
Czech Geological Survey,
W. Bohemia Museum Pilsen
Individual sponsors
ISSN: 1802-8225 (online),
1214-1119 (print)

Morphological variability within the mitrate Mitrocystella incipiens (Echinodermata, Stylophora) from the Darriwilian (Middle Ordovician) of high-latitude peri-Gondwanan regions.
Published in: Bulletin of Geosciences, volume 101, issue 1; pages: 93 - 109; Received 9 September 2025; Accepted in revised form 10 April 2026; Online 3 May 2026
Keywords: Mitrocystella incipiens, Echinodermata, Stylophora, Bohemia, Armorican Massif, Iberia,
Abstract
The mitrate Mitrocystella incipiens (Barrande, 1887) is a locally abundant stylophoran echinoderm, with a short stratigraphic range but a wide palaeobiogeographic distribution in the high-latitude peri-Gondwanan regions of the Mediterranean Province: Czech Republic (Prague Basin, Bohemia), France (Armorican Massif, Brittany), northern Portugal and Spain (Iberian Massif). Two regional subspecies were previously identified based on the morphology of their thecal outlines: M. incipiens incipiens (Barrande, 1887) (Prague Basin), and M. incipiens miloni Chauvel, 1937 (Armorican Massif and Iberian Peninsula). A sample of 40 complete and well-preserved individuals from the Armorican Massif, the Iberian Peninsula, and the Prague Basin was selected to assess whether these morphotypes could be distinguished through quantitative analysis. Geometric morphometric analysis of their theca confirmed the existence of morphological differences between the Armorican and Czech populations, but also identified that the Iberian specimens are morphologically intermediate between those from the Armorican Massif and Prague Basin. Furthermore, the antero-lateral margins of the Iberian specimens present a delicate pustulose ornamentation, while the lower thecal surface of the Armorican and Czech individuals is completely smooth. The Iberian specimens are thus assigned to a new subspecies: M. incipiens pustulosa ssp. nov. These results support the idea that all populations of Mitrocystella belong to the same species, M. incipiens, which is characterized by a broad phenotypic variation. Together with geographic isolation, subtle environmental differences between the three regions (e.g. depth) may have contributed to shape these ecophenotypes. Finally, the first example of abnormal thecal plating in Mitrocystella incipiens is described in a specimen from Spain and its possible phylogenetic implications are discussed.References
Adams, C.D. & Otarola-Castillo, E. 2013. Geomorph: An R package for the collection and analysis of geometric morphometric shape data. Methods in Ecology and Evolution 4, 393-399.
Babin, C. 1966. Mollusques bivalves et céphalopodes du Paléozoique armoricain. Etude systématique. Essai sur la phylogénie des Bivalves. Esquisse paléoécologique, 470 pp. Imprimerie commerciale et administrative, Brest.
Babin, C. & Gutiérrez-Marco, J.C. 1991. Middle Ordovician bivalves from Spain and their phyletic and palaeogeographic significance. Palaeontology 34, 109-147.
Babin, C. & Gutiérrez-Marco, J.C. 1992. Intéret paléobiogéographique de la présence du genre Trocholites (Cephalopoda, Nautiloidea) dans le Dobrotivá (Llandeilo) inférieur d’Espagne. Neues Jahrbuch für Geologie und Paläontologie Monashefte 1992, 519-541.
Barrande, J. 1887. Systeme Silurien du centre de la Boheme. 1ere Partie. Recherches Paléontologiques. Volume 7. Classe des Echinodermes. Ordre des Cystidées, 233 pp. Gerhard, Leipzig & Řivnáč, Prague.
Bednaršek, N., Calosi, P., Feely, R.A., Ambrose, R., Byrne, M., Chan, K.Y.K., Dupont, S., Padilla Gamino, J.L., Spicer, J.I., Kessouri, F., Roethler, M., Sutula, M. & Weisberg, S.B. 2021. Synthesis of thresholds of ocean acidification impacts on echinoderms. Frontiers in Marine Science 8, 602601.
Beisswenger, M. 1994. A calcichordate interpretation of the new mitrate Eumitrocystella savilli from the Ordovician of Morocco. Paläontologische Zeitschrift 68, 443-462.
Boisset, T., Lefebvre, B., Mooi, R., Kroh, A., Winkler, V., Adrien, J. & Martin, M.J. 2024. Insights into stylophoran anatomy and taphonomy based on an exceptionally preserved mitrate from the Lorraine Group (Upper Ordovician) of New York, USA. Cahiers de Biologie Marine 65, 511-516.
Bookstein, F.L. 1997. Landmark methods for forms without landmarks: Morphometrics of group differences in outline shape. Medical Image Analysis 1, 225-243.
Brenchley, P.J., Romano, M. & Gutiérrez-Marco, J.C. 1986. Proximal and distal Hummocky cross-stratified facies on a wide Ordovician Shelf in Iberia, 241-255. In Knight, R.J. & McLean, J.R. (eds) Shelf Sands and Sandstones. Canadian Society of Petroleum Geologists, Calgary, Memoir 11.
Caster, K.E. 1952. Concerning Enoploura of the Upper Ordovician and its relation to other carpoid Echinodermata. Bulletins of American Paleontology 34, 1-47.
Chauvel, J. 1937. Les hétérostélées armoricaines. Compte-Rendu Sommaire des Séances de la Société Géologique et Minéralogique de Bretagne 3(2), 1-3.
Chauvel, J. 1941. Recherches sur les cystoides et les carpoides armoricains. Mémoires de la Société Géologique et Minéralogique de Bretagne 5, 1-286.
Chauvel, J. 1981. Étude critique de quelques échinodermes stylophores du Massif armoricain. Bulletin de la Société Géologique et Minéralogique de Bretagne 13, 67-101.
Chauvel, J. & Meléndez, B. 1978. Les échinodermes (cystoides, astérozoaires, homalozoaires) de l’Ordovicien moyen des Monts de Tolede (Espagne). Estudios Geológicos 34, 75-87.
Couto, H. & Gutiérrez-Marco, J.C. 2000. Alguns fósseis raros ou pouco conhecidos da Formaçao de Valongo (Ordovícico Médio, Norte de Portugal), 191-192. In Diez, J.B. & Balbino, A.C. (eds) I Congresso Ibérico de Paleontología. XVI Jornadas de la Sociedad Espanola de Paleontología. Universidade de Évora, Évora.
David, B., Lefebvre, B., Mooi, R. & Parsley, R.L. 2000. Are homalozoans echinoderms? An answer from the extraxial-axial theory. Paleobiology 26, 529-555.
Fortey, R.A. & Owens, R.M. 1987. The Arenig Series in South Wales. Bulletin of the British Museum (Natural History), Geology 41, 69-307.
Gendry, D., Courville, P., Saucede, T., Laffont, R. & Paris, F. 2013. Contribution of morphometrics to the systematics of the Ordovician genus Neseuretus (Calymenidae, Trilobita) from the Armorican Massif, France. Journal of Paleontology 87, 456-471.
Gill, E.D. & Caster, K.E. 1960. Carpoid echinoderms from the Silurian and Devonian of Australia. Bulletins of American Paleontology 41, 5-71.
Gutiérrez-Marco, J.C. & Meléndez, B. 1987. Nuevos hallazgos de Estilóforos (Homalozoos) en los materiales ordovícicos de la zona Centroibérica. Coloquios de Paleontología 41, 41-50.
Gutiérrez-Marco, J.C., Rábano, I., Prieto, M. & Martín, J. 1984a. Estudio bioestratigráfico del Llanvirn y Llandeilo (Dobrotiviense) en la parte meridional de la zona Centroibérica (Espana). Cuadernos de Geología Ibérica 9, 287-319.
Gutiérrez-Marco, J.C., Chauvel, J., Meléndez, B. & Smith, A.B. 1984b. Los equinodermos (Cystoidea, Homalozoa, Stelleroidea, Crinoidea) del Paleozoico inferior de los Montes de Toledo y Sierra Morena (Espana). Estudios Geológicos 40, 421-453.
Gutiérrez-Marco, J.C., Sá, A.A., García-Bellido, D.C., Rábano, I. & Valério, M. 2009. Giant trilobites and trilobite clusters from the Ordovician of Portugal. Geology 37(5), 443-446.
Hammann, W. & Schmincke, S. 1986. Depositional environment and systematics of a new ophiuroid, Taeniaster ibericus n. sp. from the Middle Ordovician of Spain. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen 173(1), 47-74.
Havlíček, V. 1982. Ordovician of Bohemia: development of the Prague Basin and its benthic communities. Sborník geologických věd, Geologie 37, 103-136.
Havlíček, V. & Vaněk, J. 1966. The biostratigraphy of the Ordovician of Bohemia. Sborník geologických věd, Paleontologie 8, 7-69.
Havlíček, V. & Vaněk, J. 1990. Ordovician invertebrate communities in black shale lithofacies (Prague Basin, Czechoslovakia). Věstník Ústředního ústavu geologického 65, 223-236.
Henry, J.-L. 1980. Trilobites ordoviciens du Massif armoricain. Mémoires de la Société Géologique et Minéralogique de Bretagne 22, 1-250.
Henry, J.-L. 1989. Paléoenvironnements et dynamique de faunes de trilobites dans l’Ordovicien (Llanvirn supérieur - Caradoc basal) du Massif armoricain (France). Palaeogeography, Palaeoclimatology, Palaeoecology 73, 139-153.
Henry, J.-L., Lefebvre, B. & Chauvin, D. 1997. Stratification thermique probable des eaux marines sur la marge gondwanienne (Massif Armoricain) pendant l’Ordovicien (Llanvirn): implications paléogéographiques. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 205, 373-392.
Hunter, A.W., Lefebvre, B., Régnault, S., Roussel, P. & Claverie, R. 2007. A mixed ophiuroid-stylophoran assemblage (Echinodermata) from the Middle Ordovician (Llandeilian) of western Brittany, France, 71-86. In Álvaro, J.J., Aretz, M., Boulvain, F., Munnecke, A., Vachard, D. & Vennin, E. (eds) Palaeozoic Reefs and Bioaccumulations: Climatic and Evolutionary Controls. Geological Society London, Special Publication 275.
Jaekel, O. 1901. Ueber Carpoideen, eine neue Klasse von Pelmatozoen. Zeitschrift der Deutschen geologischen Gesellschaft 52, 661-677.
Jaekel, O. 1918. Phylogenie und System der Pelmatozoen. Paläontologische Zeitschrift 3, 1-124.
Jacinto, A.F.M., Gutiérrez-Marco, J.C. & Zamora, S. 2015. Situación actual de las investigaciones sobre equinodermos del Ordovícico portugués, 163-167. In Domingo, L., Domingo, S., Fesharaki, O., García Yelo, B., Gómez Cano, A.R., Hernández-Ballarin, V., Hontecillas, D., Cantalapiedra, J.L., López Guerrero, P., Oliver, A., Pelegrín, J., Pérez de los Ríos, M., Ríos, M., Sanisidro, O. & Valenciano, A. (eds) Current Trends in Paleontology and Evolution. XIII EJIP. Conference Proceedings. Universidad Complutense de Madrid, Madrid.
Jefferies, R.P.S. 1968. The subphylum Calcichordata (Jefferies 1967) primitive fossil chordates with echinoderm affinities. Bulletin of the British Museum (Natural History) (Geology) 16, 243-339.
Jefferies, R.P.S. 1975. Fossil evidence concerning the origin of the chordates. Symposia of the Zoological Society of London 36, 253-318.
Jefferies, R.P.S. 1981. In defence of the calcichordates. Zoological Journal of the Linnean Society 73, 351-396.
Jefferies, R.P.S. 1984. Locomotion, shape, ornament, and external ontogeny in some mitrate calcichordates. Journal of Vertebrate Paleontology 4, 292-319.
Jefferies, R.P.S. 1986. The Ancestry of the Vertebrates. 376 pp. British Museum (Natural History), London.
Jefferies, R.P.S. & Lewis, D.N. 1978. The English Silurian fossil Placocystites forbesianus and the ancestry of the vertebrates. Philosophical Transactions of the Royal Society, B 282, 205-323.
Klein, J.T. 1778. Naturalis Dispositio Echinodermatum. Accesserunt Lucubratiuncula de Aculeis Echinorum Marinorum et Specilegium de Belemnitis. Edita et Descriptionibus Novisque Inventis et Synonymis Auctorum Auca a Nathanaele Godofredo Leske. 278 pp. Officina Gleditschiana, Lipsiae (Leipzig).
Kraft, P., Linnemann, U., Mergl, M., Bruthansová, J., Laibl, L. & Geyer, G. 2023. Ordovician of the Bohemian Massif, 433-464. In Harper, D.A.T., Lefebvre, B., Percival, I.G. & Servais, T. (eds) A Global Synthesis of the Ordovician System Part 1. Geological Society London, Special Publication 532.
Lefebvre, B. 2000a. A new mitrate (Echinodermata, Stylophora) from the Tremadoc of Shropshire (England) and the origin of the Mitrocystitida. Journal of Paleontology 74, 890-906.
Lefebvre, B. 2000b. Les échinodermes stylophores du Massif armoricain. Bulletin de la Société des Sciences Naturelles de l’Ouest de la France 22, 101-122.
Lefebvre, B. 2001. A critical comment on ’ankyroids’ (Echinodermata, Stylophora). Geobios 34, 597-627.
Lefebvre, B. 2003. Stephen J. Gould, les mitrates et les monstres. Comptes Rendus Palevol 2, 509-522.
Lefebvre, B. 2005. Stylophoran supertrees revisited. Acta Palaeontologica Polonica 50, 477-486.
Lefebvre, B. 2007. Early Palaeozoic palaeobiogeography and palaeoecology of stylophoran echinoderms. Palaeogeography, Palaeoclimatology, Palaeoecology 245, 156-199.
Lefebvre, B. & Ausich, W.I. 2021. New Siluro-Devonian anomalocystitids (Echinodermata, Stylophora) from Bolivia and Canada, and a reevaluation of skeletal homologies in mitrates. Paleontological Journal 55, 932-965.
Lefebvre, B. & Fatka, O. 2003. Palaeogeographical and palaeoecological aspects of the Cambro-Ordovician radiation of echinoderms in Gondwanan Africa and peri-Gondwanan Europe. Palaeogeography, Palaeoclimatology, Palaeoecology 195, 73-97.
Lefebvre, B. & Gutiérrez-Marco, J.C. 2007. Echinoderms from the Middle Ordovician of Ossa Morena (SW Iberian Peninsula): Palaeobiogeographic and palaeoenvironmental implications, 15. In Álvaro, J.J. & Villas, E. (eds) IGCP Project 503. Regional Meeting and Field-trip Zaragoza 2007. Publicaciones Universidad de Zaragoza.
Lefebvre, B. & Régnault, S. 2009. Les stylophores, fossiles énigmatiques du Paléozoique: échinodermes, crustacés ou vertébrés? Penn ar Bed 207, 35-41.
Lefebvre, B., Régnault, S., Lardeux, H., Kundura, J.P. & Roussel, P. 2010. New Ordovician mitrates (Echinodermata, Stylophora) from the Ancenis Basin (South Armorican Domain, France): palaeogeographic and palaeoenvironmental implications, 37-44. In Harris, L.G., Böttger, S.A., Walker, C.W. & Lesser, M.P. (eds) Echinoderms: Durham. Balkema, Rotterdam.
Lefebvre, B., Sumrall, C.D., Shroat-Lewis, Reich, M., Webster, G.D., Hunter, A.W., Nardin, E., Rozhnov, S.V., Guensburg, T.E., Touzeau, A., Noailles, F. & Sprinkle, J. 2013. Palaeobiogeography of Ordovician echinoderms, 173-198. In Harper, D.A.T. & Servais, T. (eds) Early Palaeozoic Biogeography and Palaeogeography. Geological Society London, Memoir 38.
Lefebvre, B., Allaire, N., Guensburg, T.E., Hunter, A.W., Kouraiss, K., Martin, E.L.O., Nardin, E., Noailles, F., Pittet, B., Sumrall, C.D. & Zamora, S. 2016. Palaeoecological aspects of the diversification of echinoderms in the Lower Ordovician of central Anti-Atlas, Morocco. Palaeogeography, Palaeoclimatology, Palaeoecology 460, 97-121.
Lefebvre, B., Guensburg, T.E., Martin, E.L.O., Mooi, R., Nardin, E., Nohejlová, M., Saleh, F., Kouraiss, K., El Hariri, K. & David, B. 2019. Exceptionally preserved soft parts in fossils from the Lower Ordovician of Morocco clarify stylophoran affinities within basal deuterostomes. Geobios 52, 27-36.
Lefebvre, B., Nohejlová, M., Martin, E.L.O., Kašička, L., Zicha, O. & Gutiérrez-Marco, J.C. 2022. New Middle and Late Ordovician cornute stylophorans (Echinodermata) from Morocco and other peri-Gondwanan areas, 345-522. In Hunter, A.W., Álvaro, J.J., Lefebvre, B., Van Roy, P. & Zamora, S. (eds) The Great Ordovician Biodiversification Event: Insights from the Tafilalt Biota, Morocco. The Geological Society London, Special Publication 485.
Lefebvre, B., Álvaro, J.J., Casas, J.M., Ghienne, J.-F., Herbosch, A., Loi, A., Monceret, E., Verniers, J., Vidal, M., Vizcaino, D. & Servais, T. 2023. The Ordovician of France and neighbouring areas of Belgium and Germany, 375-408. In Harper, D.A.T., Lefebvre, B., Percival, I.G. & Servais, T. (eds) A Global Synthesis of the Ordovician System Part 1. Geological Society London, Special Publication 532.
Lefebvre, B., Noirit, F., De Oliveira Santos, V. & Nohejlová, M. 2025. Mitrates paranacystidés (Echinodermata, Stylophora) dans le Dévonien moyen de la rade de Brest (Finistere): affinités et implications paléobiogéographiques. Bulletin de la Société Géologique et Minéralogique de Bretagne Série D 23, 19-34.
Mélou, M. 1973. Le genre Aegiromena (brachiopode - Strophomenida) dans l’Ordovicien du Massif armoricain (France). Annales de la Société Géologique du Nord 93, 253-264.
Mélou, M. 1975. Le genre Heterorthina (Brachiopoda, Orthida) dans la Formation des Schistes de Postolonnec (Ordovicien), Finistere, France. Geobios 8, 191-208.
Parsley, R.L. 1994. Mitrocystitid functional morphology, evolution and their relationships with other primitive echinoderm classes, 167-172. In David, B., Guille, A., Féral, J.-P. & Roux, M. (eds) Echinoderms Through Time. Balkema, Rotterdam.
Parsley, R.L. 1997. The echinoderm classes Stylophora and Homoiostelea: non Calcichordata, 225-248. In Waters, J.A. & Maples, C.G. (eds) Geobiology of Echinoderms. Paleontological Society Papers 3.
Parsley, R.L., Lawson, M.H. & Pojeta, J. Jr. 2018. A practical and historical perspective on the how and why of whitening fossil specimens and casts as a precursor to their photography. Fossil Imprint 74(3-4), 237-244.
Paul, C.R.C. & Gutiérrez-Marco, J.C. 2022. Pentaradiate diploporites (Echinodermata) from the Spanish Middle Ordovician and their taxonomic significance. Spanish Journal of Palaeontology 37(2), 153-176.
Prokop, R.J. & Petr, V. 1999. Echinoderms in the Bohemian Ordovician. Journal of the Czech Geological Society 44, 63-68.
R Core Team. 2018. R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna.
Rábano, I. 1990. Trilobites del Ordovícico Medio del sector meridional de la zona Centroibérica espanola. Publicaciones Especiales del Boletín Geológico y Minero 1990, 1-233.
Rahman, I.A. & Zamora, S. 2024. Origin and early evolution of echinoderms. Annual Review of Earth and Planetary Sciences 52, 295-320.
Renaud, M., Lefebvre, B., Bailliot, D., Bailliot, M.-N., Coat, S., Gaudu, C. & Vidal, M. 2023. First report of the mitrate Mitrocystella (Echinodermata, Stylophora) in the Middle Ordovician of the Crozon Peninsula, Brittany (France). Estonian Journal of Earth Sciences 72(1), 86-89.
Reyes-Abril, J., Gutiérrez-Marco, J.C. & Villas, E. 2011. Biostratigraphy of the Middle Ordovician brachiopods from Central Spain. Cuadernos del Museo Geominero 14, 463-472.
Rogacheva, V., Mironov, A.N., Minin, K. & Gebruk, A.V. 2013. Morphological evidence of depth-related speciation in deep-sea Arctic echinoderms. Invertebrate Zoology 10(1), 143-166.
Rohlf, F.J. 2010. TPSdig2, Digitize Landmarks and Outlines. Department of Ecology and Evolution, State University of New York, Stony Brook, NY.
Rohlf, F.J. & Slice, D. 1990. Extensions of the Procrustes method for the optimal superimposition of landmarks. Systematic Zoology 39, 40-59.
Romano, M. 1976. The trilobite genus Placoparia from the Ordovician of Valongo area, north Portugal. Geological Magazine 113, 11-28.
Romano, M. 1991. Trilobites from the Ordovician of Portugal. Palaeontology 34, 329-355.
Ruta, M. 1998. An abnormal specimen of the Silurian anomalocystitid mitrate Placocystites forbesianus. Palaeontology 41(1), 173-182.
Ruta, M. 2003. A species-level supertree for stylophoran echinoderms. Acta Palaeontologica Polonica 48, 559-568.
Ruta, M. & Jell, P.A. 1999. Adoketocarpus gen. nov., a mitrate from the Ludlovian Kilmore Formation and Lochkovian Humevale Formation of central Victoria. Memoirs of the Queensland Museum 43, 377-398.
Sá, A.A. & Gutiérrez-Marco, J.C. 2006. Trilobites gigantes das ardósias de Canelas (Arouca). 207 pp. Ardosias Valério & Figueiredo, Madrid.
Sá, A.A., Gutiérrez-Marco, J.C., Rábano, I. & Valério, M. 2007. Palaeontology and Stratigraphy of the Ordovician in the Arouca Region (Central Portugal). Acta Paleontologica Sinica 46(Suppl.), 434-439.
Sá, A.A., Pereira, S., Rábano, I. & Gutiérrez-Marco, J.C. 2021. Giant trilobites and other Middle Ordovician invertebrate fossils from the Arouca UNESCO Global Geopark, Portugal. Geoconservation Research 4(1), 121-130.
Scotese, C.R. 2001. Computer Animations on CD-ROM, PALEOMAP Project. Arlington, Texas.
Sprinkle, J. 1973. Morphology and Evolution of Blastozoan Echinoderms. 283 pp. Museum of Comparative Zoology Harvard University, Cambridge (Massachusetts).
Sprinkle, J. & Guensburg, T.E. 2004. Crinozoan, blastozoan, echinozoan, asterozoan, and homalozoan echinoderms,
266-280. In Webby, B.D., Paris, F., Droser, M.L. & Percival, I.G. (eds) The Great Ordovician Biodiversification Event. Columbia University Press, New York.
Sumrall, C.D., Sprinkle, J. & Guensburg, T.E. 1997. Systematics and paleoecology of Late Cambrian echinoderms from the western United States. Journal of Paleontology 71, 1091-1109.
Tauber, E.H., Romano, M. & Reis, J.M. 1997. The trilobite Actinopeltis (Valongia) wattisoni Curtis, 1961 from the Valongo Formation (Ordovician) of North Portugal. Comunicaçoes de Instituto Geológico e Mineiro 83, 3-16.
Ubaghs, G. 1968. Stylophora, S495-S565. In Moore, R.C (ed.) Treatise on Invertebrate Paleontology, Echinodermata 1(2). Geological Society of America, Lawrence & University of Kansas Press, Boulder.
Ubaghs, G. 1970. Les échinodermes « carpoides » de l’Ordovicien inférieur de la Montagne Noire (France). 110 pp. Éditions du CNRS, Cahiers de Paléontologie, Paris.
Ubaghs, G. 1998. Echinodermes nouveaux du Cambrien supérieur de la Montagne Noire (France méridionale). Geobios 31, 809-829.
Ware, D. & Lefebvre, B. 2007. Abnormalities in the Lower Ordovician cornute Phyllocystis Thoral (Echinodermata: Stylophora) of Montagne Noire (southern France): implications for plate homology and phylogeny. Journal of Paleontology 81, 779-787.
Zamora, S., Zhu, X.J. & Lefebvre, B. 2013. A new Furongian (Cambrian) Echinoderm-Lagerstätte from the Sandu Formation (South China). Cahiers de Biologie Marine 54, 565-569.
