Chaetoceros decipiens Cleve 1873
- Dataset
- Diversity in the Globally Distributed Diatom Genus Chaetoceros (Bacillariophyceae): Three New Species from Warm-Temperate Waters
- Rank
- SPECIES
Classification
- kingdom
- Chromista
- phylum
- Ochrophyta
- class
- Bacillariophyceae
- order
- Chaetocerotales
- family
- Chaetocerotaceae
- genus
- Chaetoceros
- species
- Chaetoceros decipiens
description
C. lorenzianus Grunow 1863 p. 157, Pl 14, fig 13 Figs 16 and 20 D Lectotype designated here: A slide in a capsule (Acqu 1901 / 3674) with a coverslip of mica found in Grunow’s accession book under number 501 (Grunow 501). The capsule is glued onto a small paper sheet, and next to the capsule is a sketch of C. lorenzianus made by Grunow similar to fig 13 in Grunow [8] (here illustrated in Fig 20 D). Fig 16 A and 16 B illustrate the lectotype. A holotype was not selected by Grunow.
description
Figs 1 – 3, 20 E and 20 F and S 1 and S 2 Figs. Synonym: Chaetoceros grunowii Schütt 1895 Lectotype designated here. A holotype was not chosen by Cleve. We have chosen slide MIC 5366 in P. T. Cleve’s collection, Stockholm, Sweden as the lectotype. The slide is labelled “ Atlanten ytan 27 / 5 - 71 Lat 60 ˚ 25 Long 19 ˚ 50 ThM Fries ”. Figs 1 A, 1 B and 2 A illustrate the lectotype. Examination of the type material revealed the morphology to be in agreement with Cleve’s description and with our strains identified as C. decipiens. The Cleve material from the North Atlantic and the Davis Strait looked similar. Most prominently some sibling setae were found to fuse for a longer distance; however, in others no fusion was seen. A very delicate striation of the setae was observed, in agreement with Cleve [7]. We did not at first observe the striation in our cultured material, but a closer examination showed a similar and extremely delicate striation. Type locality: North Atlantic 60 ˚ 25 ’ N 19 ˚ 50 ’ W
description
Lectotype designated here: fig 2, plate II in Cleve [18] (shown as Fig 20 C). A holotype does not exist and a lectotype has therefore been selected.
materials_examined
Epitype designated here: Fixed material of strain P 10 A 1, from TromsØ, Norway. Material has been deposited at the Natural History Museum of Denmark, Copenhagen (C-A- 92072). Figs 13 – 15 illustrate the epitype. Sequences of D 1 - D 3 LSU rDNA (Genbank accession number KX 065247) and SSU rDNA (KX 611427) represent the epitype. Type locality: Sea of Kamtschatka Chains are straight (Fig 13 A), or slightly curved (not shown). Several chloroplasts are present in each cell (often 6 – 14). In broad girdle view, cells are usually rectangular, the pervalvar axis often longer than the apical axis (Fig 13 A and 13 B). In valve view, the valves are broadly elliptical to round-oval (Figs 13 C, 14 G and 14 H). The valve face is saddle-shaped, as the central region of the valve face is slightly raised (Figs 13 C and 14 G). The valve face edges are broadly arc shaped and marked by an elevated silica rib (Figs 13 C and 14 G). On the valve surface, costae diverge from a central annulus (Fig 14 H), without distinct poroids between the costae. A constriction is located at the border between the mantle and the girdle bands (Fig 13 B, arrows). The mantle occupies one third to one fifth of the pervalvar axis, but sometimes less – as little as one tenth during resting spore formation (Fig 15 A and 15 C). The mantle is ornamented with narrow parallel rows of costae (Fig 14 G). A furrow is situated above the basal ring of the mantle (Fig 14 F and 14 G, arrows). Apertures are narrow oval to hexagonal, sometimes slightly indented in the middle (Fig 13 A and 13 B). The setae of a chain are diverge from the apical plane (Brunel group II) (Fig 13 A). Setae are soft and more or less curved and protrude from the corners of the cell (Fig 13 A and 13 B). The terminal setae have almost the same orientation as the intercalary setae (Fig 13 A – 13 C) or they are slightly V-shaped in broad girdle view. Sibling setae cross over at the chain border, with no basal parts (Figs 13 A, 13 B and 14 F). Silicified wing-like structures are present near the seta base and form a bridge between sibling cells (Fig 14 F, arrowhead). They also form a continuation of the silica rib along the valve face edge on the intercalary valves. On the terminal valve they are replaced by fringes (Fig 14 G, curved arrow). The setae are four-six sided with four to six rows of poroids and spines arranged alternatingly on the setae (Fig 14 B – 14 E). Poroids of the setae are round-oval (Fig 14 B – 14 E), 0.2 ± 0.1 μm in size, 39.8 ± 7.4 poroids in 10 μm (n> 20), the density varying within a single seta. The poroids are barely visible in LM (Fig 14 A) (Table 1). Poroids near the seta bases are slightly smaller and more scattered (Fig 14 F). A single slit-like rimoportula without any external tube is situated slightly excentrically on the terminal valve (Fig 14 G, arrowhead). Processes on intercalary valves are absent (Fig 14 H). Several open bands are present, each with parallel costae (Fig 14 I and 14 J). The apical axis is 16.5 – 23.8 μm, the pervalvar axis 28.1 – 48.2 μm, the length of the aperture in the pervalvar axis 2.9 – 10.0 μm (n> 20). Resting spores are most often situated close to one valve of the mother cell (Fig 15 A and 15 C), sometimes in the middle of the cell (Fig 15 B). The surface of the resting spore is mainly smooth (Fig 15 E – 15 G). The primary valve extends into two elongated elevations with dichotomous branching processes distally (Fig 15 B – 15 G). One or two bulges are present on the secondary valve face (Fig 15 E and 15 G). The elevations are 21.8 – 36.2 μm long, the branching processes 5.7 – 11.4 μm long, the apical axis 14.6 – 21.4 μm (Table 2). The outer slope of the elevation is almost straight (Fig 15 F and 15 G). Length of elevation is 2 – 5 times longer than the branching processes (Table 2). A single circular row of small silica warts is visible along the secondary valve edge (Fig 15 E, arrowheads). The mantle touches the bands of the mother cell (Fig 15 A – 15 C). A ring of puncta is present at the margin of secondary valve mantle (Fig 15 G, arrowheads). Geographical distribution: Greenland (April, present study); Sea of Kamtschatka [17]; Cape Wankarema, east coast of Greenland, Baffin Bay [18]; Narragansett Bay of Rhode Island [10], Gulf of St. Lawrence; Canada (as C. lorenzianus in [11]).
materials_examined
Epitype designated here: Glutaraldehyde-fixed material of strain P 10 E 5 isolated from the Norwegian Sea (67,9050 N, 4.3238 W). The material has been deposited at the Natural History Museum of Denmark, Copenhagen (C-A- 92068). Fig 1 C and 1 D illustrate the epitype. A sequence of D 1 - D 3 LSU rDNA represents the epitype (Genbank accession number KX 065223). Emended description: Chains are usually straight, sometimes slightly arc-shaped curved (Fig 1 A, 1 C, 1 E and 1 F). In broad girdle view, the cells are quadrangular or rectangular (Fig 1 A, 1 B and 1 D – 1 G) sometimes with the apical axis longer than the pervalvar axis (Fig 1 F), sometimes the reverse (Fig 1 B, 1 D, 1 E and 1 G). Solitary cells also occur (Fig 3 A). Several (3 – 12) chloroplasts are present in each cell (Fig 1 E and 1 F). In valve view, valves are broadly elliptical to round-oval; the valve face is saddle-shaped (Figs 2 F and 3 B), the central region slightly raised and higher than the valve face margin. A silica rib along the valve face margin is broadly arcshaped (Figs 2 F and 3 B). On the valve face, the costae diverge while anastomosing from a central annulus, with solitary poroids scattered between the costae (Fig 2 H). The intercalary valve corners touch those of the adjacent cells (Fig 1 B and 1 D – 1 F). The apertures are variable, narrow slit-like oval to hexagonal (Fig 1 B and 1 D – 1 G). Setae are stiff and extend from the corners of the cell (Fig 1 A – 1 F). All setae of a chain are located more or less in the apical plane (Brunel group I) [34] (Fig 1 A – 1 D), sometimes diverging very slightly from the apical plane (Fig 1 E). Sibling setae cross over just outside the chain border and may fuse for a shorter or longer distance (Figs 1 A – 1 D, 3 B and 3 C). The setae lack a basal part (Figs 1 B, 1 D and 3 C). The extent of fusion varies even within a single chain and between the two sides of adjacent cells (Fig 1 D, arrowheads, Fig 3 B). The terminal setae diverge, forming an open U (Figs 1 A, 1 C, 1 F and 3 A). On the intercalary valve, a silica membrane of variable size is present at the margin of the apertures, forming a continuation of the marginal silica rib. The membranes of sibling cells may overlap to form a junction between the cells (Fig 3 B, arrow, Fig 3 C). Silica fringes are present on the mantle below the membranes (Fig 3 C, arrowhead) and are more distinct on the terminal valves, sometimes with long protuberances (Fig 2 F, arrowheads, Fig 3 A). Four to six rows of poroids and spines are arranged in longitudinal rows along the setae (Fig 2 C – 2 E). The poroids are round-oval (Fig 2 C – 2 E), 0.3 ± 0.1 μm long in size and with a density of 19.0 ± 6.7 poroids in 10 μm (n> 50). Sometimes a striation is visible under LM (Fig 2 A), sometimes not (Fig 2 B), not reflecting poroid density, but more or less similar to the density of the spines (Table 1). All setae have the same structure. A single rimoportula without an external tube is situated centrally on the terminal valve (Fig 2 I, arrowhead). No processes were observed on the intercalary valves (Fig 2 H). Sometimes, V-shaped non-silicified protrusions can be seen in LM centrally on the terminal valves (Fig 1 G, arrowhead). In LM, a constriction is visible at the border between the mantle and the girdle bands (Fig 1 B and 1 D, arrows), and the mantle occupies approximately one third of the pervalvar axis. The mantle has narrow parallel rows of costae separated by single rows of poroids (Fig 3 D). Silica warts are present on the basal ring of the mantle (Fig 2 G). The girdle bands have parallel costae separated by single rows of scattered poroids (Fig 2 J). The apical axis of the valve is 7.8 – 64.3 μm long, the pervalvar axis 7.8 – 78.9 μm long, the length of the aperture in the pervalvar axis 3.3 – 15.1 μm (n> 100). No resting spores were found. Sexual reproduction was observed, and was thus homothallic (S 1 and S 2 Figs). Auxospores adhered to the girdle of the mother cell (S 1 and S 2 Figs, arrows). New daughter cells achieved a larger apical axis of the valves (S 2 Fig). Geographical distribution: Davis Strait, North Atlantic [7]; Disko Bay, Greenland (April, present study); Denmark Strait; Beaufort Sea; Norwegian Sea; Denmark (April, present study; most of the year with a maximum in spring [9]); Narragansett Bay of Rhode Island [10]; Gulf of Naples, Italy ([35], present study); Peter the Great Bay, Sea of Japan [13]; Japanese coast [36]; Pacific coast of Mexico [12]; southern Gulf of Mexico [15]; Daya Bay, south China (December, present study). Chaetoceros elegans Li, Boonprakob, Moestrup & Lundholm sp. nov. Figs 4 – 7 Formal diagnosis: Straight chains or solitary cells. Four to ten chloroplasts typically present in each cell. Apical axis 11.7 – 39.7 μm. Pervalvar axis 8.9 – 42.2 μm. Aperture in pervalvar axis 4.4 – 14.5 μm. Cells quadrangular in girdle view. Saddle-shaped valve face. Central annulus, diverging costae and scattered poroids on valve face, continuing onto mantle. Silica rib on the valve face edge. A rimoportula present on the terminal valve. Furrow above the basal ring of mantle. Large and rounded, quadrangular-rectangular apertures. Setae in the apical plane. Basal part of setae extend in the pervalvar direction. Sibling setae cross over outside chain border without fusing. Terminal setae diverge in direction of chain. Silica ear-like structures present on base of setae. Four to six rows of poroids and spines on the four-six sided setae. Tear-shaped to elongate poroids on setae, ca. 0.5 ± 0.2 μm in size and 17.8 ± 5.4 poroids in 10 μm. Several bands, each band with parallel costae and scattered poroids. Resting spore with smooth surface. The primary valve extends into two elongated elevations with dichotomous branching processes. The secondary valve with one or two bulges. The angle of the outer slope of the elevation is acute. Length of elevation is 1 – 2 times longer than the branching processes. Holotype: Glutaraldehyde-fixed material of strain YL 7 deposited at the Natural History Museum of Denmark, Copenhagen (C-A- 92069). Figs 4 A – 4 D, 5 D – 5 G and 6 A – 6 C, H illustrate the holotype. A sequence of D 1 - D 3 LSU rDNA represents the holotype (Genbank accession number KX 065232). Type locality: Dapeng Bay, Guangdong Province, P. R. China. Etymology: referring to the characteristic very elegant overall look of the chains and the resting spores. The chains are straight and stiff (Fig 4 A). Cells are quadrangular in broad girdle view (Fig 4 A – 4 D). Solitary cells also occur (Fig 4 B). Typically four to ten chloroplasts are present within each cell (Fig 4 C). The valves are broadly elliptical to round-oval (Fig 5 A) with a saddle-shaped valve face, as the central region is slightly raised (Fig 5 B – 5 E). The valve face edge is broadly arc shaped and marked by an elevated silica rib (Fig 5 B – 5 E). On the valve face, costae diverge from a central annulus, with poroids scattered in between (Fig 5 F). A constriction is visible at the border between the mantle and the girdle bands (Fig 4 D, arrows). The mantle occupies nearly one third of the pervalvar axis, and is ornamented with narrow parallel rows of costae interspersed by single rows of poroids (Fig 5 G). A ring-shaped furrow is present above the basal ring of the mantle (Fig 5 B – 5 E and 5 G arrowhead). Apertures are large and rounded quadrangular-rectangular (Figs 4 C, 5 B and 5 C). All setae of a chain are located in the apical plane (Brunel group I) (Fig 4 A) [34]. The setae protrude from the elongated corners of the cell (Figs 4 C, 5 B and 5 C). The basal parts of the setae extend initially in approximately the direction of the pervalvar axis, before curving and crossing over (Fig 5 B and 5 C). Sibling setae diverge at an acute angle to each other, and cross over just outside the chain border without fusing (Figs 4 C, 5 B and 5 C). Intercalary setae near the ends of the chain are directed slightly more in the direction of the chain ends (Fig 4 A). The two terminal setae diverge slightly, continuing more or less in the direction of the chain (Fig 4 A and 4 B). On the terminal valve, two silicified, ear-like structures project from the base of the setae, one on each side (Fig 5 D, arrows), forming a continuation of the narrow silica rib on the valve edge. On the intercalary valves, these ‘ ears’ of sibling cells overlap and form a junction between the cells, in some cases fusing (Figs 5 B, 5 C, 6 A and 6 B, arrows). A small gap is sometimes seen between the crossing bases of sibling setae and the overlapping, ear-like structures (Fig 6 A and 6 B). The setae are four to six-sided, with four to six longitudinal rows of poroids and spines arranged alternatingly on the setae (Fig 6 D – 6 G). The seta poroids are tear shaped (Fig 6 D – 6 G), 0.5 ± 0.2 μm long with a density of 17.8 ± 5.4 poroids in 10 μm (n> 70) (Table 1). The poroids are visible in LM (Fig 6 C). Poroids are smaller, oval and less numerous near the base of the setae (Fig 6 A and 6 B). All setae have the same structure. A single rimoportula with a short external tube is situated centrally on the terminal valve (Fig 5 A, 5 D and 5 E), while processes are absent on the intercalary valves (Fig 5 B, 5 C and 5 F). In LM, a V-shaped non-silicified protrusion is visible centrally on the terminal valve (Fig 4 D, arrowhead). Several open girdle bands are present, each band ornamented with parallel costae, which are separated by single rows of scattered poroids (Fig 6 H). The apical axis is 11.7 – 39.7 μm long, the pervalvar axis 8.9 – 42.2 μm long, the pervalvar axis including basal parts 17.1 – 31.9 μm long, the length of the aperture in the pervalvar axis 4.4 – 14.5 μm (n> 80). The resting spores are located centrally in the mother cells, touching the bands and sometimes the valves of the mother cell (Fig 7 A and 7 B). The surface of the resting spore is mainly smooth (Fig 7 C and 7 D). The primary valve extends into two elongated elevations with dichotomous branching processes, and one or two bulges are present on the secondary valve face (Fig 7 A – 7 D). The elevations are 32.5 – 48.0 μm long, the branching processes 5.5 – 14.2 μm long, and the apical axis 32.5 – 48.0 μm. The angle of the outer slope of the elevation is acute (Fig 7 C and 7 D). Length of elevation is 1 – 2 times longer than the branching processes (Table 2). Sometimes, several silica bulges are located at the bases of the two processes (Fig 7 C and 7 D). Each process branches into a tree-like structure with the distal tips pointed and possessing one or several hooks (Fig 7 F). A single ring of puncta is located near the margin of the secondary valve mantle (Fig 7 E). Geographical distribution: Japanese coast (as C. decipiens in [36]); Gulf of California (as C. lorenzianus in [12]); New Brunswick Canada (present study); Concepción, Chile (October, present study); Dapeng Bay, south China (August, present study); Mannai Island, Thailand (June, present study). Chaetoceros laevisporus Li, Boonprakob, Moestrup & Lundholm sp. nov. Figs 8 – 10 Formal diagnosis: Straight chains. Several chloroplasts in each cell. Apical axis 22.4 – 46.3 μm. Pervalvar axis 13.2 – 42.5 μm. Aperture in pervalvar axis 6.3 – 12.0 μm. Cells rectangular in girdle view. Saddle-shaped valve face. Costae diverge from a central annulus on the valve face, continuing on to the mantle. Silica rib on the valve edge. A rimoportula present on the terminal valve. A furrow located above the basal ring of the mantle. Oval-peanut shaped apertures. Setae in the apical plane. Valve corners on sibling valves touch each other. Sibling setae cross over just outside the chain border. Terminal setae diverge in the direction of the chain. Silica ear-like structures and fringes present on the base of setae. Four to six rows of poroids and spines on the setae. Round-oval setae poroids, 0.6 ± 0.1 μm in size, with 13.8 ± 1.9 poroids in 10 μm. Several bands with parallel costae and separated poroids. Smooth resting spores with two conical elevations on the primary valve and one or two on the secondary valve. Holotype: Glutaraldehyde-fixed material of strain N 7 deposited at the Natural History Museum of Denmark, Copenhagen (C-A- 92070). Figs 8 A, 8 D – 8 F and 9 A – 9 G illustrate the holotype. A sequence of D 1 - D 3 LSU rDNA represents the holotype (Genbank accession number KX 065240). Type locality: Mannai Island, Rayong Province, Thailand. Etymology: laevis (Lat.): smooth, the resting spores are smooth without extensions. The chains are straight and stiff (Fig 8 A, 8 B and 8 D). In broad girdle view, cells are rectangular, the apical axis usually longer than the pervalvar axis (Fig 8 A and 8 B). Several chloroplasts (more than ten) are present within each cell (Fig 8 A). The valves are broadly elliptical to round-oval (Fig 8 F). The valve face is saddle shaped, as the central region is slightly raised (Fig 8 D). The valve face edge is broadly arc shaped and marked by an elevated silica rib (Fig 8 D). On the valve face, costae diverge from a central annulus, without poroids between the costae (Figs 8 F and 9 C). In LM, a constriction is visible at the border between the mantle and the girdle bands, and the mantle occupies approximately one third of the pervalvar axis (Fig 8 A, arrows). The mantle is ornamented with narrow, parallel rows of costae (Fig 9 C). A circular furrow is present above a basal ring of the mantle (Fig 9 C, arrowhead). Valve corners on intercalary valves are elevated and almost touch those of adjacent cells (Fig 8 A and 8 D). Apertures are oval-peanut shaped (Fig 8 A, 8 B and 8 D). Setae of a chain are situated more or less in the apical plane (Brunel group I) (Fig 8 B), sometimes diverging very slightly from the apical plane (Fig 8 A). The intercalary setae are straight or slightly curved, those near the ends curving more towards the ends (Fig 8 B). The setae vary greatly in length (Fig 8 B). They protrude from the corners of the cell, and sibling setae cross over just outside the chain border, without any fusion (Fig 8 A and 8 D). An ear-like structure is present at the seta base of intercalary valves near the marginal border of the aperture (Fig 9 A, arrows). The ‘ ears’ sometimes form a junction between sibling cells (Fig 9 B, arrow). The two terminal setae diverge slightly, continuing more or less in the direction of the chain (Fig 8 A and 8 B). The setae are four to six-sided, and four to six longitudinal rows of poroids and spines are arranged alternatingly on the setae (Fig 9 G). The seta poroids are round-oval (Fig 9 G), 0.6 ± 0.1 μm μm long, with 13.8 ± 1.9 poroids in 10 μm (n> 25), visible in LM (Fig 8 C) (Table 1). Poroids near the seta bases are smaller and more scattered (Fig 9 B). All setae have the same structure. A single rimoportula, which lacks an external tube, is situated centrally on the terminal valve (Fig 8 E, arrowhead, Fig 8 F, lower valve). In LM, a V-shaped non-silicified protrusion is visible centrally on the terminal valves (Fig 8 A, arrowhead). Processes are absent on the intercalary valves (Fig 8 F, upper valve). Siliceous fringes are present near the terminal seta base (Fig 9 C, arrows). Several open girdle bands are present (Fig 9 D), each with parallel costae separated by two, occasionally three, rows of scattered pores, in addition to larger poroids (Fig 9 E and 9 F). The apical axis is 27.7 – 34.2 μm long, the pervalvar axis 13.2 – 42.5 μm long, and the length of the aperture in the pervalvar axis measures 6.3 – 12.0 μm (n> 80). The resting spores are located centrally in the mother cells, touching both valves and bands of the mother cell (Fig 10 A). The spore surface is smooth with two conical elevations on the primary valve and one or two on the secondary valve (Fig 10 A and 10 B). Geographical distribution: Daya Bay, south China (December, present study); Mannai Island, Thailand (December, present study), Gulf of Panama (as C. cf. lorenzianus in [35]). Chaetoceros mannaii Boonprakob, Li, Moestrup & Lundholm sp. nov. Figs 11 and 12 Formal diagnosis: Short straight chains or solitary cells. Several chloroplasts in each cell. Apical axis 5.7 – 12.9 μm. Pervalvar axis 8.4 – 29.6 μm. Aperture in pervalvar axis 4.6 – 5.6 μm. Cells rectangular in girdle view. Saddle-shaped valve face. Heavily silicified frustule. Robust diverging costae on the valve face, continuing onto the mantle. Silica rib on the valve face edge. A rimoportula, with long external process on the terminal valve. The mantle occupies one fourth of the pervalvar axis. A furrow is present above the basal ring of the mantle. Hexagonal apertures. Setae in or slightly diverging from the apical plane. Short basal part present, sibling setae cross over outside chain border. Terminal setae diverge in the direction of the chain. Silica ear-like structures present on the base of setae. Four to six rows of poroids and spines on the setae. Large oval setae poroids, 0.7 ± 0.2 μm in size, 12.3 ± 1.6 poroids in 10 μm. Several bands with parallel costae and scattered pores. Holotype: Glutaraldehyde-fixed material of strain N 1 deposited at Natural History Museum of Denmark, Copenhagen (C-A- 92071). Figs 11 and 12 illustrate the holotype. A sequence of D 1 - D 3 LSU rDNA represents the holotype (Genbank accession number KX 065246). Type locality: Mannai Island, Rayong Province, Thailand. Etymology: from Mannai Island, Thailand. Short straight chains are typical (Fig 11 A), but solitary cells also occur. Several chloroplasts (4 – 10) are present within each cell (Fig 11 A). In broad girdle view, cells are rectangular (Fig 11 A). In valve view, valves are broadly elliptical to round-oval (Fig 11 B). The valve face is saddle shaped, as the central region of the valve face is slightly raised (Fig 11 C and 11 D). The valve face edge is broadly arc shaped and marked by an elevated silica rib (Fig 11 C – 11 E). Robust costae diverge from the centre of the valve face, without poroids between the costae (Figs 11 F and 12 C), and continue onto the mantle as robust parallel longitudinal ribs (Fig 12 D). In LM, a constriction is visible at the border between the mantle and the girdle bands (Fig 11 A, arrows), and the mantle occupies ca. one fourth of the pervalvar axis. The basal ring of the mantle is heavily silicified, with a distinct furrow above the ring (Figs 11 F and 12 D, arrowheads). The apertures are hexagonal (Fig 11 A, 11 C and 11 D). Setae of a chain seem to be located more or less in the apical plane (Brunel group I), or sometimes slightly diverging from the apical plane (Fig 11 B). The intercalary setae are straight or slightly curved (Fig 11 B). The setae protrude from the elevated corners of the cell (Fig 11 C). Sibling setae cross over just outside the chain border, with short basal parts present (Fig 11 C and 11 D). Terminal setae diverge in an acute to 90 degrees angle (Fig 11 A, 11 E and 11 F). Silicified ear-shaped structures are located at the base of the setae on both the intercalary and terminal valves (Fig 11 D and 11 E, arrowheads). The ‘ ears’ form a continuation of the narrow silica rib on the valve face edge (Fig 11 E). In the intercalary valves, the ears of sibling setae do not appear to overlap (Fig 11 C and 11 D). Setae are four-six sided with four to six longitudinal rows of poroids and spines arranged alternatingly on the setae (Fig 12 B). The seta poroids are oval (Fig 12 B), 0.7 ± 0.2 μm long and with 12.3 ± 1.6 poroids in 10 μm (n = 20), readily visible in LM (Figs 11 A and 12 A) (Table 1). Those near the seta base are slightly smaller and more scattered (Fig 12 B). All setae have the same structure. A single rimoportula with a long external tube is situated centrally on the terminal valve (Figs 11 E, 11 F and 12 C). Processes are absent on the intercalary valves (Fig 11 C and 11 D). Several open girdle bands are present (Fig 12 E), each with parallel costae separated by one row of scattered pores (Fig 12 F). The apical axis is 6.7 – 12.9 μm long, the pervalvar axis 8.4 – 29.6 μm long, the length of the aperture in the pervalvar axis 4.6 – 5.6 μm (n = 20). No resting spores were found. Geographical distribution: Peter the Great Bay, Sea of Japan (as C. lorenzianus in [13]; Gulf of California (as C. lorenzianus in [12]; Sinaloa, Mexico (present study); near Mannai Island, Thailand (present study).
materials_examined
Type locality: Adriatic Sea Original description: Rectangular or quadrangular cells in girdle view, setae bend out, setae long, delicate with punctuation. Apical axis 20 – 43 μm. Examination of the lectotype material: only a few frustules were found on the slide. (The mica was observed using a 40 X objective without oil to avoid destroying it): The aperture was quadrangular-hexagonal (Fig 16 A). The setae protruded from the elevated corners of the cell and were located more or less in the apical plane. Sibling setae crossed over just outside the chain border, with some fusion of the basal parts of the setae and with short basal parts present (Fig 16 A and 16 B). Seta poroids were large and visible in LM as punctuations (Fig 16 B), with a density of 7.2 ± 1.7 poroids in 10 μm.
Name
- Synonyms
- Chaetoceros mitra (Bailey) Cleve 1896
- Homonyms
- Chaetoceros decipiens Cleve 1873