Chaetoceros peruvianus Brightwell (1856: 107)

Bosak, Sunčica & Sarno, Diana, 2017, The planktonic diatom genus Chaetoceros Ehrenberg (Bacillariophyta) from the Adriatic Sea, Phytotaxa 314 (1), pp. 1-44 : 11

Chaetoceros peruvianus Brightwell (1856: 107) ( Figs 24–26 )

References:— Hustedt (1930), Cupp (1943), Rines & Hargraves (1988), Hernández-Becerril (1996), Shevchenko et al. (2006), Sunesen et al. (2008), Kooistra et al. (2010).

Synonyms: — Chaetoceros convexicornis Mangin , Chaetoceros peruvianus var. currens Peragallo , Chaetoceros peruvioatlanticus Karsten , Chaetoceros chilensis Krasske.

Morphometry: —a.a.: 15–39 μm; p.a.: 16–33 μm

LM: —Cells are solitary, containing numerous small plastids located in the cell body and in the setae ( Figs 24–26 ). The frustules are heterovalvate with a convex anterior valve and a concave posterior valve. The mantle of both valves is usually high, with a distinct constriction near the mantle edge, and the girdle is small. All setae lie in the apical plane and are oriented towards the same (posterior) end of the cell ( Fig. 24 ). The setae of the anterior valve emerge very close to the valve centre and are drawn up in the pervalvar direction touching each other with a groove between them, and fuse in the valve centre ( Fig. 25 ). The setae then sharply bend back in a curve toward the posterior end of the cell. The posterior setae originate close to the valve margins and then curve from the cell in the same direction as the anterior ones becoming almost parallel to the pervalvar axis. Setae are thick, coarse, long and ornamented with spines visible in LM ( Fig. 26 ).

Distinctive features: —Solitary, heterovalvar cells, all setae curved towards the posterior cell end. Basal parts of anterior setae touching each other with a groove between them.

Figures

FIGURES 24–32. Chaetoceros peruvianus, Chaetoceros pseudodichaeta. Figs 24–28: LM.Figs 29–30: SEM.Figs 31–32: TEM. Figs 24– 26: Chaetoceros peruvianus field material. 24) Single cell showing setae orientation. 25) Cell in girdle view. Note the tooth-like structure between the setae on the anterior valve (arrow). 26) Detail of seta with spines and chloroplasts. Figs 27–29: Chaetoceros pseudodichaeta field material. 27) Complete chain showing the typical three-dimensional setae orientation. Note the orientation of the terminal setae. 28) Terminal cell of the chain with the long tubular process. 29) Two sibling valves showing the fusion point of the setae which afterwards diverge in various directions. Note the hyaline rim on the valve edge (arrow). Figs 30–32: Chaetoceros pseudodichaeta, culture material strain PMFED1. 30) Valve with silica projections and rimoportula (arrow). 31) Valve face with the annulus, branching costae and few capilli (arrow). 32) Detail of a seta with large poroid marked with an arrow. Scale bars: 24=50 μm; 25, 27=20 μm; 28=10 μm; 29–31=2 μm; 26, 32= 1 μm.