Chaetoceros dadayi Pavillard (1913: 131)

Bosak, Sunčica & Sarno, Diana, 2017, The planktonic diatom genus Chaetoceros Ehrenberg (Bacillariophyta) from the Adriatic Sea, Phytotaxa 314 (1), pp. 1-44 : 7

Chaetoceros dadayi Pavillard (1913: 131) ( Fig. 4 )

References:— Hustedt (1930), Cupp (1943), Hernández-Becerril (1992).

Morphometry: —a.a.: 7–17 μm; p.a.: 7–26 μm.

LM: —Heteropolar and short chains, composed of only three cells ( Fig. 4 ), are typically attached to the lorica of the ciliate tintinnid Eutintinnus sp. In girdle view cells are rectangular with round valve corners, valve mantle is not visibly constricted. Numerous chloroplasts are present in the cell body and the setae ( Fig. 4 ). The apertures are either very narrow or absent, and the sibling valve faces are closely pressed on each other. After the crossing point, the setae strongly curve becoming almost parallel with the chain axis, but they differ in their orientation and morphology. Some setae are shorter and oriented towards the posterior end of the chain to embrace the lorica of the tintinnid, whereas two intercalary setae are directed to the anterior chain end ( Fig. 4 ).

Distinctive features:—Two setae of the neighbouring cells on the same side directed towards the anterior side of the chain while all other setae are oriented towards posterior side. Lorica of the symbiotic ciliate Eutintinnus sp. attached to the chain.

Figures

FIGURES 2–12. Chaetoceros coarctatus, Chaetoceros dadayi, Chaetoceros danicus. Figs 2–6: LM. Figs 7, 9–12: TEM. Fig. 8: SEM. Figs 2–3: Chaetoceros coarctatus field material. 2) Middle part of a chain, note the narrow apertures and attached ciliate cells. 3) Terminal part of a chain showing the orientation of the setae. Arrows indicate plastids within the setae. Fig. 4: Chaetoceros dadayi field material. Complete chain with the attached tininnid lorica. Note the characteristic orientation of intercalary setae. Figs 5–12: Chaetoceros danicus culture material, strain PMFDA1. 5) Cell in valve view, note the cross orientation of the setae. 6) Chain of two cells in girdle view. 7) Valve view showing the fine structure. 8) Internal view of the valve. 9) Fine structure of the two overlaid valves with the siliceous thickenings on the valve margin (arrow) 10) Detail of a seta. 11) Single side of the seta with arrowhead spines and poroids arranged in a grid pattern. 12) Detail of a girdle band. Scale bars: 3=50 μm; 2, 4, 5=20 μm; 6=10 μm; 7, 9=5 μm; 8=2 μm; 10–12=1 μm.