TENTATIVE KEY

FOR THE DETERMINATION OF FRESHWATER DIATOM GENERA


by P. Compère

This key is mainly based on Krammer & Lange Bertalot 1986-1991, Round et al. 1990, Rumeau & Coste 1988 and some other recent papers (see references). The numbers after names of genera not recognized in Krammer & Lange-Bertalot 1986-1991 refer to the notes at the end of the key. For the pennate diatoms the system followed at the family level is that of the "Süßwasserflora" (Krammer & Lange-Bertalot 1986-91). Considering the state of flux of the current taxonomy and nomenclature of diatoms, especially at the rank of genus, this key can only be a provisional one and the author will be thankful for any improvements suggested by users of the key.

This key is also available in French to the following address: http://perso.club-internet.fr/clci/ADLaF_Cle_des_genres.htm
 

Classification:

             Subclasses:


                        Orders:

                  *  Araphideae
                  *  Raphidioideae
                  *  Monoraphideae
                  *  Biraphideae
 

                                    Families:

                              ¤  Naviculaceae
                              ¤  Epithemiaceae
                              ¤  Bacillariaceae
                              ¤  Surirellaceae
 

1. Valve displaying a radial or concentric structure, never provided with a raphe or a pseudoraphe; valve view often circular (centric diatoms 2)
Valve ornamentation displaying a pennate structure, most generally provided with a raphe or a pseudoraphe; valve view very rarely circular (pennate diatoms 18)
(centric diatoms) 2. Frustule in valve view generally circular, rarely broadly elliptic, like a Petri dish, a drum or a more or less elongated cylinder 3
Frustule in valve view elliptic, fusiform or angular, not regularly circular, or weakly silicified frustule normally visible in girdle view only and displaying many girdle bands and imbrication lines 14

3. Cylindrical cells provided with long valve mantles, connected by the valve faces and forming long filaments 4
Cells generally solitary, rarely forming short chains; mantle shorter 8

4. Frustules weakly sillicified; external openings of the marginal strutted processes provided with elongated tubes Skeletonema
Frustules more strongly silicified 5

5. Valve face displaying an ornamentation of the centre different from that of the margin 6
Valve face apparently smooth or with the same kind of ornamentation on the whole surface 7

6. Ornamentation of the valve face made of radiating rows of areolae towards the margin and of a few large circular tube processes in the centre; interlocating spines at the junction of the valve face and the mantle Orthoseira
Valve face ornamented with radiating ribs near the margin and irregular small dots in the centre, without central processes Ellerbeckia

7. Ornamentation on the mantle very faint, often invisible Melosira
Mantle ornamented with distinct rows of areolae Aulacoseira

8.(3) Valve face provided with 2-4 large ocelli Pleurosira
Valve face without ocelli 9

9. A pseudonodulus, sometimes indistinct, on the valve; only labiate processes (rimoportulae) present Actinocyclus
Pseudonodulus lacking; labiate and strutted processes (fultoportulae) present 10

10. Ornamentation of the valve surface in central area clearly different from that of the marginal area; external opening of marginal fultoportulae generally not prolongated in an open tube Cyclotella
Ornamentation of the valve surface in central area not different from that of the marginal area 11

11. Ornamentation of the valve surface made of radial rows of areolae (striae) or of radial ribs (costae), from the centre to the margin 12
Ornamentation of the valve surface divided into radial sectors or made of areolae organized in linear or excentric patterns; cells often united by threads in loose chains or in irregular mucilaginous colonies Thalassiosira

12. Ornamentation of strong radial ribs alternating with rows of areolae; marginal spinae lacking Stephanocostis
No strong radial ribs; marginal spinae often present 13

13. External opening of the rimoportulae provided with an elongated tube; fascicles or rows of areolae not separated by marginal ribs on the internal part of the valve Stephanodiscus
External opening of the rimoportulae without tube; fascicles or rows of areolae separated by internal ribs in the marginal area Cyclostephanos

14. (2) Frustule generally seen in girdle view, rather weakly silicified, provided with many intercalary bands and imbrication lines 15
Frustule normally silicified, without this type of girdle 16

15. Cells provided with a long spine at each end Urosolenia (1)
Cells provided by two spines at each end Acanthoceras

16. Valve view 3- or 6-angular, tropical forms Hydrosera (2)
Valve view elliptical 17

17. Valve provided with long narrow hollow setae projecting laterally from the valve surface Chaetoceros
Valve margin strongly undulate; valve face divided by several internal transversal ribs; tropical forms Terpsinoë (2)

(pennate diatoms) 18. (1) Frustule provided with a raphe at least on one valve; raphe sometimes short and restricted to the poles 19
Both valves of a frustule destitute of raphe; ornamentation often interrupted along the longitudinal median axis by a hyaline area (pseudoraphe) (Araphideae 21)

19. Raphe present on both valves, but short and limited to the poles, often more developped on the mantle (Raphidioideae 37)
Raphe present on one or both valves, extending generally on most of the length of the valve 20

20. One valve of a frustule bearing a true raphe, the other provided with a longitudinal axial hyaline area (pseudoraphe) (Monoraphideae 39)
Both valves of the frustule bearing a true raphe (Biraphideae 48)

(Araphideae) 21. (18) Frustule with inner septa on the girdle bands, best seen in girdle view 22
Frustule without inner septa on the girdle bands 23

22. Valve provided with strong transapical costae Tetracyclus
Valve without transapical costae Tabellaria

23. Valve provided with transapical costae and transapical striae 24
Valve provided with transapical striae only, without costae 25

24. Heteropolar frustules (one pole wider than the other), united in semi-circular or fan-shaped colonies Meridion
Isopolar frustules (both poles more or less equal), united in zig-zag or ribbon colonies Diatoma

25. Valve triangular in face view 26
Valve bipolar in face view 27

26. Valve stellate, provided with long arms Centronella(3)
Valve triangular, provided with short arms or angles Staurosira p.p.(4)

27. Valve heteropolar, one pole wider than the other 28
Valve isopolar, both poles similar or scarcely different 29

28. Elongated cells, united in stellate planktonic colonies Asterionella
Cells solitary, less markedly elongated, never in stellate planktonic colonies Martyana(5)

29. Longitudinal axis curved 30
Longitudinal axis straight 32

30. Striae not interrupted by a pseudoraphe in valve view Semiorbis(6)
Striae interrupted by a pseudoraphe in valve view 31

31. Hyaline central area unilateral, reaching the margin on one side of the valve Hannaea(7)
Hyaline central area otherwise, not unilateral, not reaching the margin of the valve Fragilaria p.p.

32. Striae made of alveoli partially closed on the inner side (in SEM); marine or brackish diatom Synedra(8)
Striae never formed of partially closed alveoli 33

33. Areolae or alveoli closed by a complex cribrum on the external side 34
Areolae rounded, elliptical or slit-like, generally in simple rows 35

34. Areolae more or less rectangular, in transapical and longitudinal rows; pseudoraphe narrow; conspicuous central area, reaching the margin on both sides Ctenophora(9)
Alveoli transversely elongate; striae short; pseudoraphe generally wide; no central area Tabularia(10)

35. One or two rimoportulae (labiate process) on each valve; areolae simple, rounded or more or less elongated 36
Valve always without rimoportulae Staurosira(11)

36. Two rimoportulae (one near each apex) on each valve, girdle bands closed, cells solitary or united by their poles in fascicles Fragilaria subgen. Alterasynedra(12)
Generally one rimoportula on each valve, near one pole; girdle bands open, cells united by their valve faces in long chains Fragilaria subgen. Fragilaria (13)

(Rhaphidioideae) 37. (19) Cells strongly arched, almost semicircular; terminal nodules and raphe inconspicuous Semiorbis (6)
Cells less strongly arched to straight, terminal nodules and raphe generally more conspicuous 38

38. Cells isopolar (in some populations some individuals may be heteropolar) Eunotia
Cells heteropolar (all the cells of a population) Actinella

(Monoraphideae) 39. (20) Cells heteropolar; raphe rather short, not reaching the central part of the valve Peronia (14)
Cells isopolar; raphe reaching the central nodule 40

40. Longitudinal axis evenly curved or straight; both valves of the same frustule often diversely ornamented; valvocopula of the raphevalve often bearing projections uniting it with the valve surface; cells generally epiphytes and fixed by the raphevalve Cocconeis
Longitudinal axis angularly bent in the middle part; cells often fixed to the substrate by short gelatinous stalks 41

41. Ornamentation rather coarse, areolae occluded by complex cribra; girdle bands bearing one or two rows of large areolae; pseudoraphe often displaced towards a margin; raphe straight Achnanthes
Ornamentation less coarse; striae uniseriate to multiseriate, formed by simple poroids; girdle bands narrow, non punctate; raphe straight or sigmoid 42

42. Raphe and axial area sigmoid Eucocconeis(15)
Raphe and axial area straight 43

43. Raphe valve convex; valve oval-elliptic; cells generally adnate to sand grains by the valve face Psammothidium(16)
Raphe valve concave or plane 44

44. Striae made of 2 to several rows of punctae (SEM); sometimes a horseshoe-shaped area on the rapheless valve 45
Striae made of one row of areolae; no horseshoe-shaped area on the rapheless valve 46

45. Striae made of 2 rows of punctae; no horseshoe-shaped area on the rapheless valve Lemnicola(17)
Striae made of 3 to several rows of striae; rapheless valve often provided with a horseshoe-shaped area Planothidium(18)

46. Valves linear to linear-lanceolate, sometimes lanceolate-elliptic; striae fine, uniseriate Achnanthidium(19)
Valves elliptic to lanceolate; striae coarser 47

47. Areolae elongated and separated, few in each stria Kolbesia(20)
Areolae more rounded, more numerous in the striae, covered by cribra internally Karayevia(20)

(Biraphideae) 48. (20) Raphe, a longitudinal slit in the median part of the valve, formed by two branches extending from the poles to the central nodules (Naviculaceae 52)
Raphe median or, more often, marginal, included in a raphe canal, often provided with a longitudinal keel 49

49. Valves without a keel; no alar canals (Epithemiaceae 120)
Valves provided with a keel 50

50. Canal raphe marginal and circular, all around the valve, in the mantle margin (Surirellaceae 130)
Canal raphe median, in the longitudinal axis or marginal on one side of the valve 51

51. Canal raphe median, sigmoid, on a raised keel forming a wing; central nodule present Entomoneis(21)
Canal raphe marginal, less often median, but then straight, not sigmoid; keel not raised in wings (Bacillariaceae 122)

(Naviculaceae) 52. (48) Valves asymmetrical with regard to the longitudinal or to the transapical axis 53
Valves symmetrical 69

53. Valves asymmetrical with regard to both the longitudinal and transapical axes, heteropolar Gomphocymbella
Valves asymmetrical with regard to only one axis 54

54. Valves heteropolar, wider at the head pole 55
Valves isopolar; ventral side differently shaped than the dorsal one 59

55. Raphe reduced, rudimentary or almost absent on one valve 56
Raphe equally developped on both valves 57

56. Frustule straight in girdle view; raphe branches short on one valve, rudimentary to absent on the other one Peronia (14)
Frustule bent in girdle view; raphe branches well developped on one valve, reduced on the other one Rhoicosphenia (22)

57. Striae made of alveoli, at least partially closed on the inner side so that a longitudinal line crossing the striae can be seen in girdle or valve view Gomphoneis
Striae never made of closed alveoli; no longitudinal lines crossing the striae 58

58. Both poles generally capitate; both terminal fissures of the raphe similarly deflected; striae made of large rectangular areolae Didymosphaenia
Poles generally not capitate or only the head-pole capitate; terminal fissures of the raphe generally different; striae made of smaller rounded or reniform poroids Gomphonema

59. (54) Frustule in girdle view elliptic, showing the raphe system of both valves on the same side; valves strongly arched, with a much more developped mantle on the dorsal side; intercalary bands often numerous 60. Amphora
Frustule in girdle view more or less rectangular; valve face flat, not strongly arched 62

60. Girdle without intercalary bands Amphora subgen. Amphora
Intercalary bands numerous 61

61. Valve poles generally rostrate or capitate Amphora subgen. Halamphora
Valve poles acute, not rostrate; ventral side very narrow (one species in brackish to fresh water) Amphora subgen. Oxyamphora

62. Ventral margin undulate, with a more or less prominent central swelling devoid of striae; central raphe endings straight Reimeria (23)
Ventral margin different; central raphe endings deflected ventrally or dorsally 63

63. Central raphe endings deflected dorsally; stigmoid(s) on the dorsal side when presents 64
Central raphe endings deflected ventrally; stigma(s) on the ventral side when present 68

64. Terminal raphe endings also dorsally deflected; striae made of lineolae, opening externally by narrow slits Navicella(24)
Terminal raphe endings ventrally deflected 65

65. Cells forming " developed chains, provided with linking spines at the margin of the valve faces, hardly dorsiventral Pseudencyonema(24)
Cells solitary, in colonial mucus or in mucilaginous tubes 66

66. Cells generally dorsiventral, often colonial in mucus or in mucilagenous tubes; stigmoid(s) often present Encyonema(25)
Cells solitary, without stigma or stigmoid 67

67. Cells clearly dorsiventral Cymbellopsis(24)
Cells naviculoid or hardly dorsiventral Encyonopsis(24)

68. Cells generally dorsiventral, provided with mucilaginous stalk and apical pore field; one or several stigma(s) on the ventral side Cymbella(25)
Cells solitary, naviculoid or hardly dorsiventral; no stigma Cymbopleura(25)

69. (52) Girdle-bands provided with conspicuous septa 70
Girdle without septa (pseudosepta sometimes present on the valve) 71

70. Girdle provided with one or several marginal chambers (loculi) Mastogloia
Girdle bearing a massive septum provided with three lobes, one in the middle and one at each pole Diatomella

71. Valves or central area and raphe sigmoid 72
Neither valves nor central area and raphe sigmoid 75

72. Valves non sigmoid; raphe oblique and sigmoid 73
Valves and raphe sigmoid 74

73. Raphe raised on a keel; cell strongly twisted, 8-shaped in girdle view Entomomeis (21)
Raphe not raised on a keel Scoliopleura (26)

74. Areolae arranged in two striae systems perpendicular to each other (transapical and longitudinal striae) Gyrosigma
Areolae arranged in three striae systems (one transapical and two oblique systems of striae) Pleurosigma

75. Raphe raised on a keel which becomes lower in the middle of the valve Plagiotropis
Raphe not raised on a keel 76

76. Raphe reduced to a short slit near the poles, often only visible in the SEM; often chain-forming, provided with marginal spines Frankophila(27)
Raphe normally developped (but see also Diadesmis and Nupela) 77

77. One or several prominent siliceous longitudinal ribs on the valve, dividing the striae in two or several segments Oestrupia
No prominent siliceous longitudinal ribs on the valve 78

78. Striae made of alveoli, closed or open on the inner side, closed on the outer side by a porous plate bearing rows of small poroids; striae appearing solid and structureless in LM 79
Striae otherwise 88

79. Alveoli closed on the inner side of the valve face, with 1-2 small marginal apertures at the junction between valve face and mantle; apertures appearing like marginal longitudinal lines crossing the striae in LM Caloneis (28)
Alveoli open on the inner side of the valve, or closed with more or less wide apertures appearing in LM as longitudinal bands crossing the striae 80

80. Central nodule elongated; striae biseriate; areolae in the form of small slits Brebissonia
Central nodule not markedly elongated; areolae generally in the form of rounded poroids 81

81. Valves elliptical-lanceolate Pinnunavis (29)
Valves linear, linear-lanceolate to oblong, never typically elliptical-lanceolate 82. Pinnularia

82. Transapical striae broad, widely separated from each other Pinnularia sect. Distantes
Transapical striae not widely separated from each other 83

83. Transapical striae short; axial area broad, to half the valve width Pinnularia sect. Brevistriatae
Transapical striae longer; axial area narrower, to 1/3 the valve width 84

84. Striae robust, crossed by two longitudinal lines (LM) formed by the inner apertures of the partially closed alveolae 85
Striae generally not so strong, not crossed by longitudinal lines 86

85. Raphe appearing as a broad longitudinal band, not twisted Pinnularia sect. Majores
Raphe branches twisted and more or less complex Pinnularia sect. Pinnularia (30)

86. Striae fine, parallel or only slightly radiate; frustule small Pinnularia sect. Parallelistriatae
Striae generally stronger, not parallel 87

87. Length of the valve generally less than 75 m m; pole usually capitate; axial area generally narrow Pinnularia sect. Capitatae
Valves usually larger; poles typically not capitate, but sometimes rostrate; striae more or less strongly radiate in the middle of the valve, often convergent near the poles Pinnularia sect. Divergentes (31)

88. (78) Central nodule a thickened siliceous rib extending to the margin of the valve on both sides; striae interrupted on the central nodule 89
Central nodule not reaching the margins of the valve 90

89. Central nodule a " wide thickened silica rib, perpendicular to the longitudinal axis Stauroneis (32)
Central nodule x-shaped, formed of two oblique silica strips crossing one another in the middle of the valve; tropical forms Capartogramma(33)

90. Central nodule provided with horn-like appendages; a longitudinal canal in the valve structure on each side of the raphe Diploneis
Central nodule rounded, elliptic, lanceolate or rectangular, sometimes very small 91

91. Polar raphe endings forked externally; areolae of the striae arranged in longitudinal lines near the margin; generally 4 chloroplasts per cell Neidium
Polar raphe endings not forked 92

92. Raphe lying between two longitudinal silica ribs developped internally 93
No longitudinal silica ribs on each side of the raphe 96

93. Polar nodule with a very long helictoglossa which is not fused to the longitudinal ribs enclosing the raphe; valves broadly linear, rounded at the poles Vanheurckia (34)
Helictoglossae not very long, fused to the ends of the longitudinal ribs enclosing the raphe 94

94. Valves narrowly fusiform; central nodule elongated and proximal ends of the raphe branches widely separated Amphipleura(35)
Valves lanceolate or linear; central nodule not markedly elongated; proximal ends of the raphe branches not widely separated 95

95. Raphe straight, with outer fissures not reflexed in the central and terminal areas Frustulia
Raphe more or less curved, with the outer fissures reflexed in the central and terminal areas Berkella(36)

96. Valves narrowly linear; central nodule elongated; striae made of one elongated areola on the valve face and of rounded areolae on the mantle Krasskella(37)
Central nodule not elongated; striae otherwise 97

97. Small forms, less than 25 m m long and 4 m m wide; striae made of transversally elongated alveoli, open on the inside, uniseriate and closed by hymenes outside. Chamaepinnularia (38)
Striae otherwise 98

98. Striae made of transversally elongated areolae, sometimes arranged in more or less sinuous longitudinal lines 99
Striae made of rounded or longitudinally elongated (sometimes slit-like) areolae 103

99. Striae interrupted in the middle of the valve, on each side of the raphe, by more or less developped hyaline areas Anomoeoneis
No such hyaline areas 100

100.Large diatom with coarse ornamentation; central area transversally elongated, more or less rectangular; raphe branches sinuous Aneumastus(39)
Smaller diatom with finer ornamentation; central area rounded, elliptical or indistinct, rarely transversally elongated; raphe branches straight 101

101.Cell united by the valve faces in more or less long chains Diadesmis(40)
Cells not united in chains 102

102. Outer raphe slit between two longitudinal ribs; areolae often separated by warts or by sinuous longitudinal ribs Brachysira (41)
Outer raphe slit without longitudinal ribs; areolae elliptic, provided with a entrally perforated hymen on the inner side (SEM) Nupela (42)

103.(98) Valve with a broad hyaline area, sometimes lyre-shaped, on each side of the axial area; often with one or several rows of areolae on one or both sides of the axial area Fallacia (43)
No such broad hyaline areas 104

104.A few striae interrupted near the poles by curved hyaline lines; separating a few more developped areolae on both sides of the raphe Geissleria (44)
No curved hyaline lines interrupting the striae near the poles 105

105.Striae arranged in three systems crossing each other; two oblique and a transversal one Navicula sect. Decussatae (45)
Striae not arranged in three systems 106

106.Raphe in a siliceous thickening of the valve; polar nodules thickened, often transversally expanded Sellaphora (46)
Raphe not in a siliceous thickening of the valve 107

107. Raphe branches ending in fissures deflected on the same side in the central nodule Muelleria (47)
Raphe branches not terminating in deflected fissures 108

108. Striae lineolate, made of areolae opening in short longitudinal slits (perpendicular to the stria) 109
Striae punctate, made of more or less rounded areolae or fine structure indictinct 112

109. Areolae also aligned longitudinally, forming two systems of striae, crossing each other at 90E 110
Striae radiate in the middle of the valve, not in two systems crossing each other at 90E 111

110. Central area narrow, stauroid; valves fusiform; marine taxa sometimes found in inland saline waters Haslea (48)
Central area small, rounded, sometimes indistinct; valves lanceolate to linear lanceolate, not markedly fusiform Craticula (49)

111. Terminal nodules transversally developped; striae sometimes made of double rows of areolae Hippodonta (50)
Terminal nodules not transversally developped . Navicula sect. Navicula (51)

113. Numerous girdle-bands visible in girdle view; punctae often indistinct Navicula sect. Microstigmaticae (52)
Girdle-bands less numerous, not markedly conspicuous 114

114. Central area transversally elongated, irregularly rectangular; one stigma on one side of the central nodule Luticola (53)
Central area rounded or elliptical, rarely transversally expanded and then without stigma 115

115. Valves broadly elliptical to almost circular, widely rounded at the ends; striae strongly radiate, those in the middle often alternatively shorter and longer; terminal fissures of the raphe bent in opposite direction at both poles Cavinula (54)
Valves clearly longer than broad 116

116. Generally more than 24 areolae in 10 m m; sometimes one or several stigma in the central area Placoneis (55)
Generally less than 24 areolae in 10 m m 117

117. Big areolae closed by complex volae; marin or brackish species Petroneis (55)
Small round areolae close by hymenes; freshwater and brackish species Cosmioneis (55)

118. Numerous girdle-bands conspicuous in girdle view Navicula sect. Microstigmaticeae (52)
Girdle-bands less numerous, less conspicuous in girdle view 119

119. Small narrow valves, linear to lanceolate, with rostrate or capitate poles; striae generally very fine, more than 30 in 10 m m, often not visible in LM Kobayasiella (56)
Valve often small, generally broader; striae variable, sometimes not visible in LM Navicula sect. Minusculae (57)

(Epithemiaceae) 121. Raphe system generally on the ventral margin of the valve, except in the centre where it is V-shaped, with the angle of the V reaching the middle, rarely higher towards the dorsal margin; central raphe endings simple Epithemia
Raphe system eccentric, closer to the dorsal margin; central raphe endings expanded, sometimes deflected towards the ventral side Rhopalodia
(Bacillariaceae) 122. (51) Cells elongated, linear, forming tabular colonies where the individual cells can move along the valve face of one another; raphe system in the median axis of the valve Bacillaria
Cells not in tabular colonies 123

123. Cells asymmetrical with regard to the apical or the transapical axis, Gomphonema- or Cymbella-shaped 124
Cells generally symmetrical, sometimes sigmoid or curved 125

124. Cells strongly dorsiventral, Cymbella-shaped Cymbellonitzschia
Cells heteropolar, Gomphonema-shaped Gomphonitzschia

125. Cells fusiform, circular in cross section in the median part, often twisted around the apical axis so that the two raphes are helicoidally twisted and cross each other several times, but sometimes only scarcely twisted in the elongated rostra Cylindrotheca (59)
Cells not circular in cross section in the middle, but rectangular or diamond-shaped 126

126. Both raphes on the same side of the cell in all cells of a population; cross section rectangular Hantzschia
Raphes on opposite sides of the frustule in at least half the cells of a population; cross section often diamond-shaped 127

127. Canal raphe in a keel, without fibulae Simonsenia
Fibulae always present, sometimes indistinct in LM 128

128. Valve face undulate 129
Valve face flat Nitzschia

129. Striae interrupted by longitudinal hyaline areas or by undulation of the valve face; often with warts or ridges on the valve face externally; striae uni- to multiseriate, made of small poroids Tryblionella (60)
Stria not interrupted, uniseriate, made of big loculate areolae; valves often panduriform; marine or brackish Psammodictyon (61)

(Surirellaceae) 130. (50) Cells saddle-shaped, almost circular and somewhat angular in valve view Campylodiscus
Cells not saddle-shaped, linear to broadly ellptical or ovate in valve view 131

131. Valve surface marked with several transapical undulations best seen in girdle view; striae and undulations not interrupted in the median axis Cymatopleura
Valve surface not transapically undulate or with marginal undulations interrupted in the axial area 132

132. Valve narrow, elongated, linear, straight or sigmoid, always isopolar; hyalin axial area narrow, always clearly delimited Stenopterobia
Valve generally wider, broadly linear, elliptical or ovate, sometimes heteropolar, never sigmoid but sometimes more or less twisted on the apical axis 133

133. Valve surface almost flat; ornamentation made of narrow transapical silica ribs alterning with uniseriate striae; large, more or less quadrate poroids, closed by a complex cribrum Petrodictyon (62)
Valve surface transversally undulate, at least at the margins; ornamentation made of uniseriate or multiseriate striae, without true silica ribs; small poroids occluded by volae Surirella

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Notes

(1) This genus was erected by Crawford & Round, in Round et al. (1990) for freshwater species formerly allotted to the marine genus Rhizosolenia.

(2) Tropical genus, not treated in Krammer & Lange-Bertalot (1991)

(3) Centronella Voigt is classified under Fragilaria by Krammer & Lange-Bertalot (1991: 132, 167).

(4) Including Staurosirella Williams & Round.

(5) For Krammer & Lange-Bertalot (1991 : 160, 165) Opephora Petit is restricted to the marine and brackish species around O. pacifica (Grunow) Petit and O. olsenii Moeller, whereas the freshwater species O. martyi Héribaud is classified under Fragilaria; this species becomes the type of the new genus Martyana Round in Round et al. (1990: 362, 673).

(6) Semiorbis Patrick was originally described in the Fragilariaceae; since then it has been shown that short raphe slits are present at the poles; therefore the genus is included in the Eunotiaceae by Round et al. (1990: 456) or even merged into the genus Eunotia (Krammer & Lange-Bertalot 1991: 227). It is called Amphicampa in Rumeau & Coste (1988).

(7) Hannaea Patrick is included in Fragilaria by Krammer & Lange-Bertalot (1991: 134, 167); it is often incorrectly called Ceratoneis Ehrenb.

(8) The genus Synedra Ehr. (1830) is here restricted to the type species S. balthica Ehr. (cf. Krammer & Lange-Bertalot 1991: 111); it corresponds with "Catacombas" Williams & Round (1986), nom. illeg. (Round et al. 1990: 378) but not with "Synedra" sensu Round et al. (1990: 370) which is included in Fragilaria by Krammer & Lange-Bertalot (1991: 143) as subgenus Alterasynedra.

(9) Treated as subgenus Cnetophora (Grun.) Lange-Bertalot in Krammer & Lange-Bertalot 1991.

(10) Treated as subgenus Tabularia (Kütz.) Lange-Bertalot in Krammer & Lange-Bertalot 1991.

(11) Includes Staurosira Ehr., Staurosirella William & Round and Punctastriata William & Round, all considered as separate genera in Round et al. (1990) but included in Fragilaria subgen. Staurosira in Krammer & Lange-Bertalot (1991) and in Lange-Bertalot (1993).

(12) subgenus Alterasynedra Lange-Bertalot (1993) includes Synedra sensu Williams (1986), non Ehrenberg (see note 8).

(13) Including Fragilariforma (Ralfs) William & Round. For Krammer & Lange-Bertalot (1991), subgenus Fragilaria also includes Centronella Voigt and Hannaea Patrick, considered as separate genera in Round et al. (1990).

(14) A rudimentary raphe has sometimes been observed on the "rapheless" valve and thus the genus is sometimes included in the Eunotiaceae (Krammer & Lange-Bertalot 1991: 229).

(15) Included in Achnanthes Ag. by Krammer & Lange-Bertalot (1991: 16) but considered as a separate genus in Round et al. (1990: 514).

(16) Genus recently segregated from Achnanthes Ag. by Round & Bukhtiyarova (1996: 3) for a group of species around A. marginulata Grun.

(17) Genus established by Round & Basson (1997: 77), based on Achnanthes hungarica (Grun.) Grun.

(18) Genus segregated from Achnanthes by Round & Bukhtiyarova (1996: 351) for the group of species around A. lanceolata (Bréb.) Grun.; Achnantheiopsis Lange-Bertalot (1997b: 200) has the same type and is thus an illegitimate synonym.

(19) Treated as a subgenus of Achnanthes Ag. in Krammer & Lange-Bertalot (1991: 2, 6) but as a good genus by Round et al. (1990: 512); includes here Rossithidium Round & Bukhtiyarova (1996), nom. inval., sine typo.

(20) Both Karayevia and Kolbesia Round & Bukhtiyarova (1996) ex Round (1998), proposed for species formerly allotted to Achnanthes sensu lato, were originally invalid names, published without indication of a type; they have been validated by Round (1998: 181).

(21) Formerly called Amphiprora Ehrenberg.

(22) Rhoicosphenia is sometimes included in the Achnanthaceae, owing to the reduction of the raphe system on one of the valves (Patrick & Reimer 1966, Rumeau & Coste 1988).

(23) Reimeria Kociolek & Stoermer (1987) was previously included in Cymbella Ag. (Krammer & Lange-Bertalot 1986, Rumeau & Coste 1988).

(24) Genera separated from Cymbella and Encyonema by Krammer in his recent revision of the cymbelloid diatoms (1997); these new genera are validly described but their taxonomic treatment should appear in the following volumes of his revision; the lack of a key makes their correct interpretation difficult.

(25) Encyonema Kützing and Cymbopleura (Krammer) Krammer have been considered as subgenera of Cymbella Ag. (Krammer & Lange-Bertalot 1986); they are treated as genera in the recent revision of Krammer (1997), with a circumscription somewhat different from that of the Süßwasserflora (1986). Encyonema is also recognized as a genus in Round et al (1990); Cymbopleura was only recently validated by Krammer (1999). See also note 24.

(26) For Krammer & Lange-Bertalot (1986), includes the brackish and marine genus Scoliotropis Cleve; another brackish water genus, Scolioneis D.G. Mann has a similar shape but differs in ultrastructural characters.

(27) Small genus recently described by Lange-Bertalot (1997: 66) for some chain-forming, Fragilaria-like diatoms, characterized by a reduced raphe system near the poles of the valves.

(28) Caloneis is merged in Pinnularia by Round et al. (1990).

(29) Genus not accepted by Krammer & Lange-Bertalot (1986), who classify it in Navicula in spite of the alveolate striae; Krammer (1992) includes the type species in Pinnularia, as P. elegans, without any comment on Pinnunavis.

(30) Often called sect. Complexae; as it includes P. viridis, the type of the genus, its correct name is sect. Pinnularia.

(31) Includes also the group "Tabellariae" of Cleve.

(32) The species showing polar pseudosepta (internal thickenings of the valve margin, near the poles) are sometimes separated in subgenus Pleurastrum (Rumeau & Coste 1980); some brackish and marine species, with central stauros not exactly reaching the valve margin and differently shaped chloroplasts are separated in the genus Staurophora Mereschowsky (Round et al. (1990).

(33) Tropical genus, not treated in Krammer & Lange-Bertalot (1986), sometimes included in Stauroneis.

(34) This monospecific genus seems to be restricted to northern America; it is not treated in Krammer & Lange-Bertalot 1986; its correct name is Vanheurckia Bréb. (1868), the lectotype of which, V. lewisiana (Grev.) Bréb., is also the only species and thus holotype of the later synonym Frickea Heiden (1906).

(35) According to Krammer & Lange-Bertalot (1986) also includesKrasskella Ross & Sims and the marine genus Berkeleya Grev.

(36) Genus included in Frustulia Rabenh. by Krammer & Lange-Bertalot (1986: 258, 260) and by Round et al. (1990: 538).

(37) Genus included in Amphipleura by Krammer & Lange-Bertalot (1986: 264).

(38) This genus was introduced by Lange-Bertalot & Metzeltin (1996) for species previously included in Navicula or in Pinnularia.

(39) The genus Aneumastus Mann & Stickle was formerly included in Navicula (Krammer & Lange-Bertalot 1986), sometimes as subgenus Tuscula (Hust.) Patrick (Patrick & Reimer 1966).

(40) Diadesmis Kütz. is included in Navicula sensu lato by Krammer & Lange-Bertalot (1986, Untergruppe Nc) but considered as a good genus by Round et al. (1990: 534).

(41) The freshwater species of Brachysira Kützing were previously included in Anomoeoneis Pfitzer (Patrick & Reimer 1966; Krammer & Lange-Bertalot 1986). They are allotted to Brachysira (Round & Mann 1981, Round et al. 1990) though the type species (B. aponina Kütz.) is a marine species.

(42) Genus recently described from Papua New Guinea (Vyverman & Compère 1991) and accepted by Lange-Bertalot (1993, Lange-Bertalot & Moser 1994) who adds several new species and new combinations.

(43) Fallacia Stickle & Mann includes species formerly classified in Navicula subgen. Lyraneis and subgen. Auricula (Patrick & Reimer 1966). The marine species around Navicula lyra Ehr. allotted to the genus Lyrella Karajeva (Round et al. 1990), show the same lyre-shaped area on the valve face.

(44) This new genus, proposed by Lange-Bertalot & Metzeltin (1996), agrees with section Annulatae Hustedt (Schlüsselgruppe K in Krammer & Lange-Bertalot 1986).

(45) These sections are neither treated by Round et al. (1990) nor by subsequent authors; however they are generically different from Navicula sensu stricto and should be considered as separate genera.

(46) Sellaphora Mereschk. was formerly included in Navicula as sect. Bacillares (Krammer & Lange-Bertalot 1986, Rumeau & Coste 1988) or subgenus Bacillum (Patrick & Reimer 1966); it is recognized as a separate genus in Round et al. (1990).

(47) Muelleria (Frenguelli) Frenguelli was recently resurrected by Spaulding & Stoermer (1997) as a genus name for the group of species formerly allotted to Navicula sect. Fistulatae; however this name could be considered as an orthographic variant and later homonym of Muellera L. f. 1782 (Code, art. 53.3)

(48) Haslea Simonsen is included in Navicula, as sect. Fusiformes by Krammer & Lange-Bertalot (1986).

(49) Craticula Grun. was formerly treated as sect. Orthostichae (Krammer & Lange-Bertalot 1986, Rumeau & Coste 1988) or subgen. Cuspidata and Halophila (Patrick & Reimer 1966) of Navicula.

(50) Hippodonta Lange-Bertalot et al. (1996) was erected for the group of species around N. capitata Ehrenb. The type and most of the species have lineolate areolae, but some have the striae made of double rows of puncta.

(51) For Round et al. (1990), and most subsequent authors (e.g. Lange-Bertalot 1993, 1994, etc.) Navicula is restricted to sect. Lineolatae of former authors (= subgen. Navicula in Patrick & Reimer 1966).

(52) Some of the fresh and brackish water species allotted to sect. Microstigmaticae by Krammer & Lange-Bertalot (1986) are now classified in the separate genera Parlibellus Cox or Proschkinia Karajeva (Round et al. 1990); for other species it is not clear to which new genus they should be allotted, since they are not treated by Round et al. (1990). Several species included in sect. Microstigmaticae are treated in subgen. Decipientes by Patrick & Reimer (1966).

(53) Luticola D.G. Mann includes the group of species around Navicula mutica, previously allotted to Navicula sect. Punctatae, already distinguished as a special group (Schlüsselgruppe E) in Krammer & Lange-Bertalot (1988) and Rumeau & Coste (1988).

(54) Cavinula Mann & Stickle includes the species around Navicula pseudoscutiformis formerly included in sect. Punctatae and also recognized as a special group (Schlüsselgruppe F) by Krammer & Lange-Bertalot (1986).

(55) The new genera Cosmioneis Mann & Stickle and Petroneis Stickle & Mann. as well as Placoneis Meresch., Cavinula and Luticola include species formerly allotted to Navicula sect. Punctatae (Krammer & Lange-Bertalot 1986) or to Navicula subgen. Punctulata (Patrick & Reimer 1966). It is not always easy to allot to the correct genus species of this group not treated in Round et al. (1990) or in other recent revisions.

(56) This small group agrees with Navicula sect. Subtilissimae; it is quite different from Navicula sensu stricto but had not been treated by Round et al. (1990). It has been raised to genus and named Kobayasia by Lange-Bertalot (1996); however, the name Kobayasia Lange-Bertalot is a later homonym of Kobayasia Imai & Kawam. (Basidiomycetes) and Lange-Bertalot (1999) renamed this genus Kobayasiella.

(57) This group remains very heterogenous; in Krammer & Lange-Bertalot (1986) it was divided into six subgroups, one of which ("Untergruppe Nc", p. 219) clearly corresponding to the genus Diadesmis Kütz. sensu Round et al. 1990; some of the other subgroups could also be recognized as separate genera, like Mayamaea Lange-Bertalot based on Navicula atomus (Kütz.) Grun. or Fistulifera Lange-Bertalot based on Navicula saprophila Lange-Bertalot & Bonik. Both these genera were recently erected by Lange-Bertalot (1997a) but their circumscription does not match that of the corresponding subgroups in the Süßwasserflora (1986). Naviculadicta Lange-Bertalot (1994) also includes species currently allotted to sect. Minusculae together with species from other groups or sections; the use of this catch-all genus intended as a substitute for Navicula sensu lato (for species not yet allotted to one of the numerous smaller genera recently segregated from Navicula) is not recommended (see Kociolek 1996).

(58) Denticula Kützing is allotted to the Bacillariaceae by Round et al. (1990).

(59) Cylindrotheca as revised by Reimann & Lewin (1964) also includes the brackish water species generally called Nitzschia closterium; the genus is characterized by the fusiform body of the cell, circular in cross section whereas in typical Nitzchia it is rectangular to diamond-shaped in cross-section.

(60) Tryblionella W. Smith was revived by Round et al. (1990) as a genus including the former sect. Tryblionella, Circumscutae, Apiculatae and Pseudotryblionella of Nitzschia.

(61) Psammodictyon D.G. Mann in Round et al. (1990) is a rather small marine genus, with a few species also in brackish water, including the species formerly classified in Nitzschia sect. Panduriformes.

(62) Petrodictyon D.G. Mann in Round et al. (1990) was erected for a small group of marine and brackish species formerly included in Surirella, around S. gemma Ehrenb.
 
 
 




 
 

References

Bukhtiyarova L. & Round F., 1996. - Revision of the genus Achnanthes sensu lato. Psammothidium, a new genus based on A. marginulatum. Diatom Research 11 (1): 1-30.

Cox E.J., 1996. - Identification of freshwater diatoms from live material: IX+158 p. London, Chapman & Hall.

Kociolek J.P., 1996. - Comment: Taxonomic instability and the creation of Naviculadicta Lange Bertalot in Lange-Bertalot & Moser, a new catch-all genus of Diatoms. Diatom Research 11: 219-222.

Krammer K., 1992. - Pinnularia, eine Monographie der europäischen Taxa. Biblioth. Diatom. 26: 1-353

Krammer K., 1997. - Die cymbelloiden Diatomeen, eine Monographie der weltweit bekannten Taxa. Teil 1. Allgemeines und Encyonema Part. Biblioth. Diatom. 36: 1-382.

Krammer K., 1999. - Validierung von Cymbopleura nov. gen. Iconogr. Diatom. 6: 292.

Lange-Bertalot H., 1993. - 85 Neue Taxa und über 100 weitere neu definierte Taxa ergänzend zur Süsswasserflora von Mitteleuropa vol. 2/1-4. Biblioth. Diatom. 27: XXIII+454 p.

Lange-Bertalot H., 1994.- Brachysira, Monographie der Gattung. Biblioth. Diatom. 29: 1-212.

Lange-Bertalot H., 1996. - Kobayasia bicuneus gen. et spec. nov. Iconogr. Diatom. 4: 277-287.

Lange-Bertalot H., 1997a. - Frankophila, Mayamaea and Fistulifera : drei neue Gattungen der Klasse Bacillariophyceae. Arch. Protistenk.148: 65-76.

Lange-Bertalot H., 1997b. - Zur Revision der Gattung Achnanthes sensu lato (Bacillariophyceae): Achnantheiopsis, eine neue Gattung mit dem Typus generis A. lanceolata. Arch. Protistenk. 148: 199-208.

Lange-Bertalot H., 1999. - Kobayasiella nom. nov. ein neuer Gattungsname für Kobayasia Lange-Bertalot 1996. Iconogr. Diatom.6: 272-275.

Lange-Bertalot H. & Metzeltin D., 1996. - Oligotrophie-Indikatoren, 800 Taxa repräsentativ für drei diverse Seen-Typen. Iconogr. Diatom. 2: 1-390.

Lange-Bertalot H., Metzeltin D. & Witkowski A., 1996. - Hippodonta gen. nov. Umschreibung und Begründung einer neuen Gattung der Naviculaceae. Iconogr. Diatom. 4: 247-275.

Patrick R. & Reimer C.W., 1966-1975. - The diatoms of the United States. Monogr. Acad. Nat. Sc. Philadelphia13 (1): XI + 688 p. (1966); (2/1): IX + 213 p. (1975).

Reimann B.E.F. & Lewin J.C., 1964. - The diatom genus Cylindrotheca Rabh. Journ. Roy. Microsc. Soc. 83 (3): 283-296).

Round F.E. & Basson P.W., 1997. - A new monoraphid diatom genus (Pogoneis) from Bahrain and the transfer of previously described species A. hungarica and A. taeniata to new genera. Diatom Research 12: 71-81.

Round F.E. & Bukhtiyarova L., 1996. - Four new genera based on Achnanthes (Achnanthidium) together with a re-definition of Achnanthidium. Diatom Research 11 (2): 345-361.

Round F.E. & Mann D.G., 1981. - The diatom genus Brachysira. I. Typification and separation from Anomoeoneis. Arch. Protistenk.124: 221-231.

Round F.E., Crawford R.M. & Mann D.G., 1990. - The diatoms. Biology and morphology of the genera : 747 p. Cambridge University Press.

Rumeau A. & Coste M., 1988. - Initiation à la systématique des diatomées d'eau douce. Bull. Fr. Pêche Piscic.309 : 1-69.

Spaulding S.A. & Stoermer E.F., 1997. - Taxonomy and distribution of the genus Muelleria Frenguelli. Diatom Research 12: 95-115.

Vyverman W. & Compère P., 1991. - Nupela giluwensis gen. et spec. nov. A new genus of naviculoid diatoms. Diatom Research6: 175-179.

Williams D.M., 1986. - Comparative morphology of some species of Synedra Ehrenb. with a new definition of the genus. Diatom Research 1: 131-152.

Williams D.M. & Round F.E., 1986. - Revision of the genus Synedra Ehrenb. Diatom Research 1: 313-339.
 
 

INDEX OF GENERA


The number(s) after each name refer(s) to the corresponding entry of the key; numbers between ( ) refer to the notes following the key.

Acanthoceras 15

Achnantheiopsis (18)

Achnanthes 41

Achnanthidium 46, (19)

Actinella 38

Actinocyclus 9

Amphicampa (6)

Amphipleura 94, (35)

Amphiprora (21)

Amphora 59, 60

Amphora subg. Halamphora 61

Amphora subg. Oxyamphora 61

Aneumastus 100, (39)

Anomoeoneis 99

Asterionella 28

Aulacoseira 7

Bacillaria 122

Berkeleya (35)

Berkella 95, (36)

Brachysira 102, 41

Brebissonia 80

Caloneis 79, (28)

Campylodiscus 130

Capartogramma 89, (33)

Catacombas (8)

Cavinula 115, (54)

Centronella 26, (3)

Ceratoneis (7)

Chaetoceros 17

Chamaepinnularia 97, (38)

Cocconeis 40

Cosmioneis 117, (55)

Craticula 110, (49)

Ctenophora 34, (9)

Cyclotella 13

Cyclostephanos 10

Cylindrotheca 125, (59)

Cymatopleura 131

Cymbella 68, (24, 25)

Cymbellonitzschia 124

Cymbellopsis 67, (24)

Cymbopleura 68, (25)

Denticula 120, (58)

Diadesmis 76, 101, (40)

Diatoma 24

Diatomella 70

Didymosphaenia 58

Diploneis 90

Ellerbeckia 6

Encyonema 66, (25)

Encyonopsis 67, (24)

Entomoneis 51, 73, (21)

Epithemia 121

Eucocconeis 42, (15)

Eunotia 38

Fallacia 103, (43)

Fistulifera (57)

Fragilaria 36, (13)

Fragilaria subg. Alterasynedra 36, (12)

Fragilariforma (13)

Frankophila 76, 27

Frickea (34)

Frustulia 95

Geissleria 104, (44)

Gomphocymbella 53

Gomphoneis 57

Gomphonema 58

Gomphonitzschia 124

Gyrosigma 74

Hannaea 31, (7)

Hantzschia 126

Haslea 118, (48)

Hippodonta 111, (50)

Hydrosera 16, (2)

Karayevia 47, (20)

Kobayasia (56)

Kobayasiella 119, (56)

Kolbesia 47, (20)

Krasskella 96, (37)

Lemnicola 45, (17)

Luticola 114, (53)

Lyrella (43)

Martyana 28, (5)

Mastogloia 70

Mayamaea (57)

Melosira 7

Meridion 24

Muelleria 107, (47)

Navicella 64, (24)

Navicula 111, (51, 57)

Navicula subg. Auricula (43)

Navicula subg. Bacillum (46)

Navicula subg. Cuspidata (49)

Navicula subg. Decipientes (52)

Navicula subg. Halophila (49)

Navicula subg. Lyraneis (43)

Navicula subg. Punctulata (55)

Navicula sect. Annulatae (44)

Navicula sect. Bacillares (46)

Navicula sect. Decussatae 105, (45)

Navicula sect. Fistulatae (47)

Navicula sect. Fusiformes (48)

Navicula sect. Lineolatae (51)

Navicula sect. Microstigmaticae 113, 118, (52)

Navicula sect. Minusculae 119, (57)

Navicula sect. Orthostichae (49)

Navicula sect. Punctatae (53, 54, 55)

Navicula sect. Subtilissimae (56)

Naviculadicta (57)

Neidium 91

Nitzschia 128, (59, 60, 61)

Nupela 77, 102, (42)

Oestrupia 77

Opephora (5)

Orthoseira 6

Parlibellus (52)

Peronia 39, 56, (14)

Petrodictyon 133, (62)

Petroneis 117, (55)

Pinnularia 82, 85, (28, 29, 30)

Pinnularia sect. Brevistriatae 83

Pinnularia sect. Capitatae 87

Pinnularia sect. Complexae (30)

Pinnularia sect. Distantes 82

Pinnularia sect. Divergentes 87, (31)

Pinnularia sect. Majores 85

Pinnularia sect. Parallelistriatae 86

Pinnunavis 81, (29)

Placoneis 116, (55)

Plagiotropis 75

Planothidium 45, (18)

Pleurastrum (32)

Pleurosigma 74

Pleurosira 8

Proschkinia (52)

Psammodictyon 127, (61)

Psammothidium 43, (16)

Pseudencyonema 65, (24)

Punctastriata (11)

Reimeria 62, (23)

Rhizosolenia (1)

Rhoicosphenia 56, (22)

Rhopalodia 121

Rossithidium (19)

Scolioneis (26)

Scoliopleura 73, (26)

Scoliotropis (26)

Sellaphora 106, (46)

Semiorbis 30, 37, (6)

Simonsenia 127

Skeletonema 4

Stauroneis 89, (32)

Stauroneis subgen. Pleurastrum (32)

Staurophora (32)

Staurosira 35, (11)

Staurosirella (4, 11)

Stenopterobia 132

Stephanocostis 12

Stephanodiscus 13

Surirella 133, (62)

Synedra 32, (8)

Tabellaria 22

Tabularia 34, (10)

Terpsinoe 17, (2)

Tetracyclus 22

Thalassiosira 11

Tryblionella 127, (60)

Urosolenia 15, (1)

Vanheurckia 93, (34)