Ceratium fusus, from Phyto’pedia.

Belongs within: Peridiniphycidae.
Contains: Ceratium horridum, Ceratium tripos.

Ceratium is a diverse genus of flagellates, including both freshwater and marine species, with three or four horns radiating from the theca.

Ceratium… er… Neoceratium… er… Tripos humilis
Published 30 July 2013
The dinoflagellate formerly known as Ceratium humile, from here.

Ceratium has long been a popular choice as a representative dinoflagellate genus for textbooks, because as micro-organisms go, they’re fairly specky. The theca of Ceratium is characterised by protruding horns, with an elongate anterior horn and one to three posterior horns. The posterior horns may be directed back from the theca, or they may curve around towards the front to produce an anchor-like shape. These horns increase the cell’s buoyancy, though they do make them fairly slow swimmers. The concept of Ceratium has been fairly stable since the early 1800s, but Gómez et al. (2010) found when conducting a molecular analysis of a number of ‘Ceratium‘ species that there was a deep divide between freshwater and marine Ceratium species. As well as the molecular divide, there is also a morphological difference: freshwater species have six plates around the cingulum (the groove around the theca body in which sits one of the flagella), while marine species have five cingular plates. As a result, Gómez et al. proposed dividing the two clades between two genera, with the name Ceratium being restricted to the freshwater species. The marine species were all transferred into a new genus Neoceratium. However, Gómez (2013) later recognised that there were a number of older generic names floating about that had been given to marine taxa, and the marine species were moved again into a resurrected genus Tripos. Among the taxa affected by this double transfer was the species shown in the photo above, now known as Tripos humilis.

There are a large number of anchor-shaped Tripos species, and distinguishing them is apparently a difficult process. Tripos humilis has the anterior part of the theca in front of the cingulum (excluding the anterior horn) fairly low, the upper surface of the theca (i.e. the side away from the origin of the flagella) strongly convex, and the right-hand posterior horn much longer than the left, with the right horn tending to converge towards the anterior horn while the left horn diverges (Subrahmanyan 1968). The cingulum is also distinctly angled relative to the posterior margin of the theca. While other Tripos species are found in a range of habitats, T. humilis appears to be a more specifically tropical species. It is found pantropically, though seemingly nowhere abundantly.

Chain of Tripos, from here.

Dinoflagellates can sometimes form long chains when dividing individuals don’t fully separate but continue to multiply. In Ceratium and Tripos species, the members of a chain remain connected through the apical horns. Chaining individuals may be somewhat morphologically distinct from isolated individuals; in T. humilis, the horns of chained individuals are relatively much shorter. Chains are apparently commoner when dinoflagellates form ‘red tides’ or algal blooms, and one suggested function is that a chain is able to swim faster overall than an individual, improving the dinoflagellates’ ability to compete when moving to occupy suitable places in the water column for light or food.

Systematics of Ceratium

Characters (from Steidinger & Williams 1970): Theca with 3–4 horns, 1 apical, 2 to 3 antapical, 1 sometimes rudimentary. Some species with spatula-like epitheca and no apical horn. Plate formula: 4′, 5”, 5”’ and 2””. Chloroplasts present. Obvious thecate ventral area composed of 4 plates occupying at least 2/3rds of midbody’s ventral surface.

<==Ceratium Schrank 1793 (see below for synonymy)FT93
    |--C. fususLO03
    |    |--C. f. var. fusus [=C. f. ssp. boreale Pavillard 1931]S73
    |    `--C. f. var. seta (Ehrenberg) Sournia 1966 [=Peridinium seta]S73
    `--+--C. lineatumLO03
       `--C. triposLO03
Ceratium incertae sedis:
  *C. pleuroceras Schrank 1793SW70
  C. angustum Campbell 1934 [=C. angusta (l. c.), C. angustua (l. c.), C. angustula (l. c.)]S73
  C. arcticumS73
    |--C. a. var. arcticumS73
    |--C. a. var. longipes (Bailey) Graham & Bronikovsky 1944 [=Peridinium longipes, C. longipes]S73
    `--C. a. var. ventricosum (Ostenfeld) Graham & Bronikovsky 1944 [=C. longipes var. ventricosum]S73
  C. arcuatumS73
  C. arietinumS73
    |--C. a. var. arietinumS73
    |--C. a. var. bucephalum (Cleve) Sournia 1966 (see below for synonymy)S73
    |--C. a. var. gracilentum (Jörgensen) Sournia 1966 (see below for synonymy)S73
    `--C. ‘bucephalum’ var. heterocamptumS73
  C. aultii Graham & Bronikovsky 1944S73
  C. azoricumSW70
  C. balticum (Möbius) Balech 1944 [=C. furca var. balticum]S73
  C. beloneSW70
  C. bigelowiiSW70
  C. boehmii Graham & Bronikovsky 1944S73
  C. brachycerosSW70 [=C. hirundinella f. brachycerosTP87]
  C. breve [=C. brave (l. c.)]S73
    |--C. b. var. breveS73
    |--C. b. var. curvulumS73
    `--C. b. var. schmidtii (Jörgensen) Sournia 1966 [=C. schmidtii]S73
  C. brunellii Rampi 1942S73
  C. californiense [=C. gallicum f. californiense, C. macroceros f. californiense (Kofoid) Silva 1952]S73
  C. candelabrumS73
    |  i. s.: C. c. f. commune Böhm 1931S73
    |--C. c. var. candelabrum [=C. c. var. genuinum Pavillard 1931 non C. tripos ssp. genuinum Pavillard 1931]S73
    |    |--C. c. var. c. f. candelabrumS73
    |    `--C. c. var. c. f. subcandelabrum Lopez 1966S73
    |--C. c. var. depressum [=C. furca var. depressum]S73
    |    |--C. c. var. d. f. depressumS73
    |    `--C. c. var. d. f. hiemale Böhm 1931S73
    `--C. c. var. subrotundum Pavillard 1930 [=C. c. f. subrotundum (Pavillard) Sournia 1968]S73
  C. carnegiei Graham & Bronikovsky 1944S73
  C. carolinianumSW70
  C. carrienseS73
    |--C. c. var. carriense [=C. c. f. eucarriense Böhm 1931]S73
    `--C. c. var. volansS73
  C. conciliansS73
    |--C. c. var. conciliansS73
    `--C. c. var. subaequale Graham & Bronikovsky 1944S73
  C. contortumS73
    |  i. s.: C. c. f. subcontortum (Schröder) Steemann Nielsen 1934 [=C. subcontortum]S73
    |--C. c. var. contortumS73
    |--C. c. var. karstenii (Pavillard) Sournia 1966 (see below for synonymy)S73
    |--C. c. var. longinum (Karsten) Sournia 1966 (see below for synonymy)S73
    `--C. c. var. robustum (Karsten) Sournia 1966 (see below for synonymy)S73
  C. contrariumS73 [=C. contrarium f. typicum Böhm 1931S73, C. trichoceros var. contrariumSW70]
  C. cornutum (Ehrenberg 1838) Claparède & Lachmann 1859FT93
  C. declinatumSW70
    |--C. d. f. declinatumSW70
    `--C. d. f. normaleSW70
  C. deflexumSW70
  C. densT87b
  C. denticulatum (Jörgensen) Paulsen 1931 (see below for synonymy)S73
  C. digitatumS73
  C. divaricatumTP87
  C. divergensG84
  C. egyptiacum Halim 1963S73
    |--C. e. f. egyptiacumS73
    `--C. e. f. suezense Halim 1965S73
  C. euarcuatumSW70
  C. extensumS73
    |--C. e. f. extensumS73
    |--C. e. f. strictoides Böhm 1931S73
    `--C. e. f. strictum (Okamura & Nishikawa) Steemann Nielsen 1934 [=C. fusus var. strictum]S73
  C. falcatiforme [=C. inflatum ssp. falcatiforme (Jörgensen) Peters 1934]S73
  C. falcatum [=C. pennatum f. falcatum, C. inflatum ssp. falcatum (Kofoid) Peters 1934]S73
  C. filicorne Steemann Nielsen 1934S73
  C. furcaLO03
    |  i. s.: C. f. var. hircus (Schröder) Margalef ex Sournia 1973 [=C. hircus Schröder 1909]S73
    |         C. ‘hircus’ var. sinicum Nie 1936S73
    |--C. f. ssp. furca (see below for synonymy)S73
    `--C. f. ssp. eugrammumS73
  C. furcoidesTP87
  C. gibberumS73
    |--C. g. var. gibberumS73
    `--C. g. var. dispar (Pouchet) Sournia 1966 (see below for synonymy)S73
  C. gracileS73
  C. hexacanthumS73
    |--C. h. f. hexacanthumS73
    |--C. h. f. hiemale non C. candelabrum var. depressum f. hiemale Böhm 1931S73
    |--C. h. f. pavillardii (Rampi) Sournia 1968 [=C. aestuarium var. pavillardii Rampi 1939]S73
    `--C. h. f. spirale [=C. reticulatum ssp. spirale]S73
  C. hirundinella (Müller) Bergh 1882FT93 (see below for synonymy)
  C. horridumS73
  C. humileSW70
  C. hundhausenii [=C. carriense f. hundhausenii (Schröder) Wood 1954 (nom. inv.)]S73
  C. incisumSW70
  C. inflatumS73
    |--C. i. f. inflatumS73
    `--C. i. f. concavum (Gourret) Böhm 1931S73
  C. kofoidiiSW70
  C. lamellicorne [=C. platycorne var. lamellicorne (Kofoid) Peters 1934]S73
  C. lanceolatumSW70
  C. longirostrum [=C. inflatum ssp. longirostrum (Gourret) Peters 1934]S73
  C. lunulaSW70
  C. macroceras Schrank 1793T87a [=C. tripos var. macrocerosS73]
    |  i. s.: C. m. f. claviceps (see below for synonymy)S73
    |--C. m. var. macrocerosS73
    |--C. m. var. gallicum (Kofoid) Sournia 1966 [=C. gallicum]S73
    `--C. m. var. hainanense Nie 1936S73
  C. massilienseSW70
  C. minutumSW70
  C. obesum Pavillard 1930S73
  C. ‘pacificum’ Wood 1963 (preoc.)S73
  C. paradoxidesSW70
  C. pentagonumS73
    |  i. s.: C. p. f. grandeTP87
    |         C. p. f. subpentagonum Lopez 1966S73
    |         C. p. f. turgidusTP87
    |--C. p. ssp. pentagonumS73
    |--C. p. ssp. pacificum Graham & Bronikovsky 1944S73
    |--C. p. ssp. robustum (Cleve) Graham & Bronikovsky 1944 (see below for synonymy)S73
    |--C. p. ssp. subrobustum (Jörgensen) Peters 1934 [=C. subrobustum (Jörgensen) Steemann Nielsen 1934]S73
    `--C. p. ssp. tenerum (Jörgensen) Graham & Bronikovsky 1944S73
  C. petersii Steemann Nielsen 1934S73
  C. platycorneS73
    |--C. p. ssp. platycorneS73
    `--C. p. ssp. dilatatum (Kofoid) Steemann Nielsen 1939 [=C. tripos f. dilatatum]S73
  C. protuberans (Karsten) Kofoid 1908 [=C. tripos ssp. protuberans]S73
  C. pulchellum Schröder 1906 (see below for synonymy)S73
    |--C. p. var. pulchellumS73
    |--C. p. var. indicum Böhm 1931S73
    `--C. p. var. joergensenii Wang 1936S73
  C. ramakrishnii Subrahmanyan 1968S73
  C. ranipesS73
    |--C. r. var. ranipesS73
    |--C. r. var. furcellatum (Lemmermann) Böhm 1931 [=C. tripos var. furcellatum]S73
    `--C. r. var. palmatumT87b
  C. reticulatumD01
  C. schroederi Nie 1936S73
  C. schroeteriS73
  C. semipulchellum (Jörgensen) Steemann Nielsen 1934 (see below for synonymy)S73
  C. setaceumS73
    |--C. s. ssp. setaceumS73
    `--C. s. ssp. robustum Peters 1934 non C. arcuatum f. robustum (Karsten) Böhm 1931S73
  C. symmetricum [=C. gracile var. symmetricum]S73
    |--C. s. var. symmetricumS73
    |--C. s. var. coarctatum (Pavillard) Graham & Bronikovsky 1944S73
    `--C. s. var. orthoceras (Jörgensen) Graham & Bronikovsky 1944 (see below for synonymy)S73
  C. tasmaniae Wood 1963S73
  C. teresSW70
  C. trichocerosS73
  C. tripodioides (Jörgensen) Steemann Nielsen 1934 (see below for synonymy)S73
  C. uteri Campbell 1934S73
  C. vulturS73
    |  i. s.: C. v. f. japonicum (Schröder) Wood ex Sournia 1973 [=C. japonicum Schröder 1906]S73
    |--C. v. var. vulturS73
    |--C. v. var. pavillardii (Jörgensen) Graham & Bronikovsky 1944 non C. aestuarium var. pavillardii Rampi 1939S73
    |--C. v. var. productum Wood 1963S73
    |--C. v. var. recurvum (Jörgensen) Steemann Nielsen 1934S73 (see below for synonymy)
    |--C. v. var. regulare Graham & Bronikovsky 1944S73
    |--C. v. var. reversum Graham & Bronikovsky 1944S73
    `--C. v. var. sumatranum (Karsten) Steemann Nielsen 1934 (see below for synonymy)S73
  C. sect. ArchaeceratiumT87b
    |--C. cephalotumT87b
    |--C. gravidumT87b
    |    |--C. g. var. gravidumS73
    |    |--C. g. var. angustum non C. angustum Campbell 1934S73
    |    `--C. g. var. elongatum Wood 1963S73
    `--C. praelongumT87b
Nomina invalida: Ceratium arietinum f. centertum Jörgensen in Halim 1960S73
                 C. azoricum f. nordicum Balech 1962S73
                 C. brachyspinum Athanassopoulos 1931 [=C. tripos var. brachyspinum Athanassopoulos 1931, C. tripos var. brevispinum Athanassopoulos 1931]S73
                 C. candelabrum f. eucandelabrum Böhm 1931S73
                 C. concilians f. contortum Böhm 1931S73
                 C. declinatum ssp. angusticorne Peters 1934 [=C. d. var. angusticorne (Peters) Graham & Bronikovsky 1944]S73
                 C. declinatum ssp. laticorne Peters 1934 [=C. d. var. laticorne (Peters) Graham & Bronikovsky 1944]S73
                 C. declinatum f. orthoceras Böhm 1931S73
                 C. furca var. berghii f. subberghii Lopez 1966S73
                 C. hexacanthum var. reflexum Steidinger & Williams 1970S73
                 C. massiliense f. ellipticum Böhm 1931S73
                 C. pulchellum f. tenuicorne Böhm 1931S73

Ceratium Schrank 1793 [incl. Amphiceratium Vanhöffen 1896, Biceratium Vanhöffen 1896, Ceratophorus Diesing 1850 non Schuckard 1837 (ICZN), Dimastigoaulax Diesing 1866, Hirundinella Bory de Saint-Vincent 1826, Poroceratium Vanhöffen 1896, Tripos Bory de Saint-Vincent 1823]FT93

Ceratium arietinum var. bucephalum (Cleve) Sournia 1966 [=C. tripos var. bucephalum, C. arietinum ssp. bucephalum (Cleve) Graham & Bronikovsky 1944]S73

Ceratium arietinum var. gracilentum (Jörgensen) Sournia 1966 [=C. arietinum ssp. gracilentum (Jörgensen) Peters 1934, C. gracilentum (Jörgensen) Rampi 1952]S73

Ceratium contortum var. karstenii (Pavillard) Sournia 1966 [=C. hexacanthum var. karstenii Pavillard 1930, C. arcuatum f. karstenii (Pavillard) Peters 1934]S73

Ceratium contortum var. longinum (Karsten) Sournia 1966 [=C. arcuatum f. longinum (Karsten) Peters 1934, C. tripos ssp. longinum]S73

Ceratium contortum var. robustum (Karsten) Sournia 1966 [=C. arcuatum f. robustum (Karsten) Böhm 1931, C. tripos ssp. arcuatum var. robustum]S73

Ceratium denticulatum (Jörgensen) Paulsen 1931 [=C. horridum ssp. buceros var. denticulatum, C. horridum ssp. buceros var. tenue f. denticulatum]S73

Ceratium furca ssp. furca [=C. f. f. berghii (Lemmermann) Halim 1968, C. f. var. berghii f. berghii (Lemmermann) Lopez 1966]S73

Ceratium gibberum var. dispar (Pouchet) Sournia 1966 [=C. tripos var. dispar, C. concilians var. dispar Böhm 1931 (nom. inv.)]S73

Ceratium hirundinella (Müller) Bergh 1882FT93 [=Bursaria hirundinella Müller 1773FT93, Hirundinella quadricuspis Bory de St Vincent 1824T87a]

Ceratium macroceros f. claviceps [=C. contrarium var. claviceps (Schröder) Graham & Bronikovsky 1944, C. trichoceros f. claviceps Wood 1954 (nom. inv.)]S73

Ceratium pentagonum ssp. robustum (Cleve) Graham & Bronikovsky 1944 nec C. tripos ssp. arcuatum var. robustum nec C. setaceum ssp. robustum Peters 1934 [=C. lineatum var. robustum]S73

Ceratium pulchellum Schröder 1906 [=C. tripos ssp. pulchellum (Schröder) Peters 1934, C. tripos var. pulchellum (Schröder) Margalef ex Sournia 1973]S73

Ceratium semipulchellum (Jörgensen) Steemann Nielsen 1934 [=C. pulchellum f. semipulchellum, C. tripos ssp. semipulchellum (Jörgensen) Peters 1934]S73

Ceratium symmetricum var. orthoceras (Jörgensen) Graham & Bronikovsky 1944 [=C. gracile f. orthoceras, C. orthoceras (Jörgensen) Pavillard 1931]S73

Ceratium tripodioides (Jörgensen) Steemann Nielsen 1934 [=C. pulchellum f. tripodioides, C. tripos var. tripodioides (Jörgensen) Paulsen 1931]S73

Ceratium vultur var. recurvum (Jörgensen) Steemann Nielsen 1934S73 [=C. sumatranum var. recurvumS73, C. vultur var. vultur f. recurvumT87b]

Ceratium vultur var. sumatranum (Karsten) Steemann Nielsen 1934 [=C. tripos ssp. vultur var. sumatranum, C. vultur f. sumatranum (Karsten) Sournia 1968]S73

*Type species of generic name indicated


[D01] Daday, E. 1901. Édesvizi mikroszkópi állatok [Mikroskopische Süsswasserthiere]. In: Horváth, G. (ed.) Zichy Jenő Gróf Harmadik Ázsiai Utazása [Dritte Asiatische Forschungsreise des Grafen Eugen Zichy] vol. 2. Zichy Jenő Gróf Harmadik Ázsiai Utazásának Állattani Eredményei [Zoologische Ergebnisse der Dritten Asiatischen Forschungsreise des Grafen Eugen Zichy] pp. 375–470. Victor Hornyánszky: Budapest, and Karl W. Hierseman: Leipzig.

[FT93] Fensome, R. A., F. J. R. Taylor, G. Norris, W. A. S. Sarjeant, D. I. Wharton & G. L. Williams. 1993. A classification of living and fossil dinoflagellates. Micropaleontology Special Publication 7: i–viii, 1–351.

Gómez, F. 2013. Reinstatement of the dinoflagellate genus Tripos to replace Neoceratium, marine species of Ceratium (Dinophyceae, Alveolata). CICIMAR Oceánides 28(1): 1–22.

Gómez, F., D. Moreira & P. López-García. 2010. Neoceratium gen. nov., a new genus for all marine species currently assigned to Ceratium (Dinophyceae). Protist 161: 35–54.

[G84] Gruber, A. 1884. Die Protozoen des Hafens von Genua. Verhandlungen der Kaiserlichen Leopoldinisch-Carolinischen Deutschen Akademie der Naturforscher [Nova Acta Academiae Caesareae Leopoldino-Carolinae Germanicae Naturae Curiosorum] 46 (4): 473–539, pls 7–11.

[LO03] Lee, J. J., R. Olea, M. Cevasco, X. Pochon, M. Correia, M. Shpigel & J. Pawlowski. 2003. A marine dinoflagellate, Amphidinium eilatiensis n. sp., from the benthos of a mariculture sedimentation pond in Eilat, Israel. Journal of Eukaryotic Microbiology 50 (6): 439–448.

[S73] Sournia, A. 1973. Catalogue des espèces et taxons infraspécifiques de Dinoflagellés marins actuels publiés depuis la révision de J. Schiller. I. Dinoflagellés libres. Beihefte zur Nova Hedwigia 48: 1–92.

[SW70] Steidinger, K. A., & J. Williams. 1970. Dinoflagellates. Memoirs of the Hourglass Cruises 2: 1–251.

Subrahmanyan, R. 1968. The Dinophyceae of the Indian Seas. Part I. Genus Ceratium Schrank. Marine Biological Association of India, Memoir 2: 1–129.

[T87a] Taylor, F. J. R. 1987a. General group characteristics; special features of interest; short history of dinoflagellate study. In: Taylor, F. J. R. (ed.) The Biology of Dinoflagellates pp. 1–23. Blackwell Scientific.

[T87b] Taylor, F. J. R. 1987b. Dinoflagellate morphology. In: Taylor, F. J. R. (ed.) The Biology of Dinoflagellates pp. 24–91. Blackwell Scientific.

[TP87] Taylor, F. J. R., & U. Pollingher. 1987. Ecology of dinoflagellates. In: Taylor, F. J. R. (ed.) The Biology of Dinoflagellates pp. 398–529. Blackwell Scientific.

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