Morphological Characteristics of Four Species in the Genus Skeletonema in Coastal Waters of South Korea

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  • ABSTRACT

    Most Skeletonema species have been identified under the name of S. costatum. To assess the morphological species diversity in the genus Skeletonema, we surveyed the nine localities in the coastal waters of South Korea. The light microscopy (LM) and scanning electron microscopy (SEM) observations in this study showed that ultrastructural features of genus Skeletonema discriminated among four species: S. dohrnii Sarno & Kooistra, S. marinoi Sarno & Zingone, S. subsalsum (Cleve) Bethge, and S. tropicum Cleve. In S. dohrnii, cell diameters were 3-6 μm and the pervalvar axes were 13-19 μm. One or two partial chloroplasts were visible in a cell. Cells of S. marinoi were 4-10 μm and the pervalvar axes were 8-18 μm. Each cell contained one chloroplast. Cells of S. subsalsum which contained 1-2 chloroplasts were 8-13 μm and the pervalvar axes were 11-20 μm. Cells of S. tropicum were 10-18 μm and the pervalvar axes were 4-9 μm. 2-4 chloroplasts were seen in each cell. Tip width of fultoportula in S. dohrnii and S. marioni was flared and flat, but that in S. subsalsum and S. tropicum was narrow. Morphological groups among them, S. dohrnii and S. marinoi were the most widely distributed in all seasons, while S. tropicum was only occurred in a summer season.


  • KEYWORD

    Korean coastal waters , morphological characteristics , Skeletonema dohrnii , S. marioni , S. subsalsum , S. tropicum

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  • [Table 1.] Collection information of Skeletonema species used in the analyses
    Collection information of Skeletonema species used in the analyses
  • [Table 2.] Morphological characteristics of four species in genus Skeletonema in this study and comparison with Sarno et al.’s observation(2005)
    Morphological characteristics of four species in genus Skeletonema in this study and comparison with Sarno et al.’s observation(2005)
  • [Fig. 1.] Skeletonema dohrnii. Light microscopy (A); Scanning electron microscopy (B-G). (A) Colony in girdle view. (B) Colony in girdleview connected with the the intercalary FPs (IFPs) (arrow). (C) Scale-covered the IFPs. (D) Intercalary valves with IFPs joined ina 1 : 1 or 1 : 2 fashion (arrow). (E) Convex valve view with loculate areolae. Note the IFPs entirely split and open at their base(arrow). (F) Terminal valve with the long and tubular terminal rimoportula process (arrow). (G) Short IFPP (arrow) and theflared tips and jagged margins of IFPs (arrowhead). Scale bars: A = 20 μm; B = 5 μm; C, D, E, G = 1 μm; F = 2 μm.
    Skeletonema dohrnii. Light microscopy (A); Scanning electron microscopy (B-G). (A) Colony in girdle view. (B) Colony in girdleview connected with the the intercalary FPs (IFPs) (arrow). (C) Scale-covered the IFPs. (D) Intercalary valves with IFPs joined ina 1 : 1 or 1 : 2 fashion (arrow). (E) Convex valve view with loculate areolae. Note the IFPs entirely split and open at their base(arrow). (F) Terminal valve with the long and tubular terminal rimoportula process (arrow). (G) Short IFPP (arrow) and theflared tips and jagged margins of IFPs (arrowhead). Scale bars: A = 20 μm; B = 5 μm; C, D, E, G = 1 μm; F = 2 μm.
  • [Fig. 2.] Skeletonema marinoi. Light microscopy (A); Scanning electron microscopy (B-H). (A) Colony in girdle view. (B) Colony in girdleview connected with the intercalary FPs (IFPs) and the terminal rimoportula process (TRP) (arrow). (C) The TRP (arrow) and flatand flared tips of the terminal FPs (arrowhead) in convex valve view. (D, F) Intercalary valves with 1 : 1 (arrow in Fig. D) or 1 : 2(Fig. F) IFP junctions and short the intercalary RP (arrowhead in Figs D, F). (E) Cingular band with rows of pores. (F) The tetragonalareolae distributed from the valve center. (G, H) Two IFP junctions of different forms. Scale bars: A , B = 10 μm; C, E, G, H =1 μm; D, F = 2 μm.
    Skeletonema marinoi. Light microscopy (A); Scanning electron microscopy (B-H). (A) Colony in girdle view. (B) Colony in girdleview connected with the intercalary FPs (IFPs) and the terminal rimoportula process (TRP) (arrow). (C) The TRP (arrow) and flatand flared tips of the terminal FPs (arrowhead) in convex valve view. (D, F) Intercalary valves with 1 : 1 (arrow in Fig. D) or 1 : 2(Fig. F) IFP junctions and short the intercalary RP (arrowhead in Figs D, F). (E) Cingular band with rows of pores. (F) The tetragonalareolae distributed from the valve center. (G, H) Two IFP junctions of different forms. Scale bars: A , B = 10 μm; C, E, G, H =1 μm; D, F = 2 μm.
  • [Fig. 3.] Skeletonema subsalsum. Light microscopy (A); Scanning electron microscopy (B-G). (A) Colony in girdle view. (B) Scale-coveredcolony in convex valve view connected with the intercalary FPs (IFPs). (C) The marginal long intercalary RP (IRP) (arrow) in theintercalary valve. (D) The pointed terminal FPs in convex valve view. (E) the marginal IRP (arrow) in the flat valve view. (F)Terminal valve with the subcentral hook-shaped terminal rimoportula process (arrow). (G) The intercalary valve with 1 : 1 shortIFP junctions. Scale bars: A = 20 μm, B, E, G = 2 μm, C, D, F = 1 μm.
    Skeletonema subsalsum. Light microscopy (A); Scanning electron microscopy (B-G). (A) Colony in girdle view. (B) Scale-coveredcolony in convex valve view connected with the intercalary FPs (IFPs). (C) The marginal long intercalary RP (IRP) (arrow) in theintercalary valve. (D) The pointed terminal FPs in convex valve view. (E) the marginal IRP (arrow) in the flat valve view. (F)Terminal valve with the subcentral hook-shaped terminal rimoportula process (arrow). (G) The intercalary valve with 1 : 1 shortIFP junctions. Scale bars: A = 20 μm, B, E, G = 2 μm, C, D, F = 1 μm.
  • [Fig. 4.] Skeletonema tropicum. Light microscopy (A, B); Scanning electron microscopy (C-H). (A, B) Colony in girdle view with slightlycurved joint (A) and straight joint (B). (C) Colony in girdle view connected with the intercalary FPs (IFPs). (D, F) The trumpetshapedterminal rimoportula process (arrowhead) and claw-shaped terminal FPs (arrow). (E, G) The intercalary valve with 1 : 1IFP interdigitated junctions. (H) The short marginal intercalary RP (arrow) and the tetragonal areolae distributed from the valvecenter. Scale bars: A , C = 20 μm; B = 10 μm; D = 2 μm; E, F = 5 μm; G, H = 1 μm.
    Skeletonema tropicum. Light microscopy (A, B); Scanning electron microscopy (C-H). (A, B) Colony in girdle view with slightlycurved joint (A) and straight joint (B). (C) Colony in girdle view connected with the intercalary FPs (IFPs). (D, F) The trumpetshapedterminal rimoportula process (arrowhead) and claw-shaped terminal FPs (arrow). (E, G) The intercalary valve with 1 : 1IFP interdigitated junctions. (H) The short marginal intercalary RP (arrow) and the tetragonal areolae distributed from the valvecenter. Scale bars: A , C = 20 μm; B = 10 μm; D = 2 μm; E, F = 5 μm; G, H = 1 μm.