Hippodonta fujiannensis Zhao, Chen & Gao, 2017

Zhao, Long, Sun, Jiandong, Gao, Yahui, Liang, Junrong, Sun, Lin, Li, Xuesong & Chen, Changping, 2017, Hippodonta fujiannensis sp. nov. (Bacillariophyceae), a new epipsammic diatom from the low intertidal zone, Fujian Province, China, Phytotaxa 295 (1), pp. 77-85 : 79-80

Hippodonta fujiannensis Zhao, Chen & Gao sp. nov. ( Figs 2–36 )

Frustules rectangular, valves elliptic-lanceolate to rhombic-lanceolate, 11–44 μm long, 4–8 μm broad. Raphe filiform, weakly pronounced. Central area rectangular to panduriform. Striae uniseriate, dissymmetrical on the valve face, 12–20 in 10 μm. Girdle band broad and unornamented.

Type:— China, Fujian Province, Haitan Island, Longfengtou Beach, 25°31’18.41’’N, 119°48’16.26’’E, sand grain samples, 1 cm deep, collected by Long Zhao on April 18, 2015, School of Life Sciences, Xiamen University, Xiamen (holotype EMDPT1504 ! = Fig. 8 , 17.8 mm south by 41.6 mm west from the benchmark spot on the slide; isotype EMDPT1504 ! = Fig. 9 , 15.4 mm south by 40.0 mm west from the benchmark spot on the slide). Holotype and isotype slides are housed at Diatom Laboratory, School of Life Sciences , Xiamen University, China .

LM ( Figs 2–13 ): Frustules rectangular with gently concave central nodule in girdle view. Cells solitary, valves elliptic-lanceolate to rhombic-lanceolate with broadly rounded ends in smaller frustules and acutely rounded ends in bigger frustules. Valve ends not protracted. Valve length 11–44 μm, width 4–8 μm. Axial area narrow-linear throughout, weakly expanding into a rectangular to panduriform central area. Central area well defined by continuous stria shortening, at both valve sides. Terminal areas clearly distinguishable in LM, lunate to semicircular and cap-like. Raphe filiform, weakly pronounced, with teardrop-shaped and closely spaced central endings. Terminal pores of raphe clearly discernible in LM, equally pronounced as the central endings, teardrop-shaped. Striae coarse, strongly radiate throughout valve length, or becoming moderately radiate at valve ends, evenly spaced throughout, 12–20 in 10 μm. Interstriae width equal to, or wider than, striae. Lineolae densely spaced within each stria, discernible in LM in longer valves.

SEM ( Figs 14–32 ): Externally, valve face gently curved in transapical section merging gradually into valve mantle ( Figs 14, 18 ). Raphe slits quite fine. Terminal endings of raphe distinct, strongly pronounced, teardrop-shaped depressions, positioned before terminal area, or weakly advancing into it, and slightly curved towards one valve side in smaller valves, or strongly curved in bigger valves ( Figs 15, 18 ). Central endings of raphe small, teardrop-shaped, closely positioned depressions ( Fig. 20 ). Central nodule clearly visible in girdle view ( Fig. 23 ). Central area asymmetrical in bigger valves, with one side much bigger than the other ( Figs 16, 20 ). Striae uniseriate throughout valve face and mantle ( Figs 14, 17, 18 ). On one valve side, one column of lineolae, nearest to the raphe, is positioned perpendicular to remaining lineolae of the striae ( Fig. 17 ). One the other valve side this column not as pronounced. Lineolae linear, 25–40 in 10 μm. Single rows of areolae surround valve apices. Prominent hyaline area present throughout valve mantle ( Figs 21, 25 ). Internally, striae positioned on shallow linear depressions; thus, valve face not flat. Lineolae covered by hymens ( Fig. 32 ). Central endings of raphe linear, closely positioned and gradually disappearing. Semicircular to rectangular hyaline area clearly developed in central area. Linear raphe slits distally terminated by weak, crescentshaped helictoglossae, weakly advancing into the terminal area. Terminal area strongly pronounced internally. Girdle band quite broad and unornamented ( Fig. 24 ). Since the girdle is relatively broad, the frustules of H. fijiannensis often lie in girdle view or at an angle in valve view.

Etymology: The species name “ fujiannensis ” refers to Fujian Province.

Distribution and ecology: In our 25 sampling sites along the coast line of Fujian Province, H. fujiannensis was only found in the low intertidal zone of Haitan Island. The specimens of H. fujiannensis are infrequent in all of the samples from the Haitan Island; it is epipsammic ( Figs 33–36 ) and inhabits the marine environment.

Figures

FIGURES 2–13. LM images of Hippodonta fujiannensis. Fig. 8. Holotype. Scale bar = 10 μm.

FIGURES 14–20. SEM images of Hippodonta fujiannensis. Figs 14, 17, 18. External view of entire valve. Striae uniseriate throughout the valve face and mantle. On one valve side, one column of lineolae closest to the raphe is positioned perpendicular towards remaining lineolae of the striae. Figs 15, 19. Close up of valve apices. Terminal endings of raphe distinct, strongly pronounced, teardrop-shaped depressions, positioned before terminal area or weakly advancing into it, slightly curved towards one valve side. Figs 16, 20. Close up of the central area. Central endings of the raphe small, teardrop-shaped depressions; central endings are positioned close together. Central area dissymmetrical. Scale bars in Figs 14, 18 = 5 μm; Fig. 17 = 2 μm; Figs 15, 16, 19, 20 = 1 μm.

FIGURES 21–26. SEM images of Hippodonta fujiannensis. Figs 21, 24.External view of complete frustules showing broad,unornamented girdle. Fig. 25. External girdle view of entire valve. The edge of the valve has no ornamentation. Figs 22, 26. Detail of one apex in girdle view, showing one row of apical areolae and the hyaline area. Fig. 23. Detail of the central area in girdle view, showing the central raphe endings and the central nodule. Scale bars in Fig. 25 = 10 μm; Figs 21, 23 = 5 μm; Figs 22, 24, 26 = 1 μm.

FIGURES 27–32. SEM images of Hippodonta fujiannensis. Figs 27, 30. Internal view of entire valve. Striae positioned on shallow linear depressions; thus, valve face not flat. Figs 28, 31. Internal view, detail of valve apex. Linear raphe slits distally terminated by weak, crescent-shaped helictoglossae, weakly advancing into the terminal area. Terminal area strongly pronounced. One row of lineolae around the valve apex. Figs 29, 32. Internal view, detail of central area. Central endings of the raphe linear, closely positioned, and gradually disappearing. Semicircular to rectangular hyaline area clearly developed in central area. Lineolae covered by hymens. Scale bars in Figs 27, 30 = 5 μm; Figs 31, 32 = 2 μm; Figs 28, 29 = 1 μm.

FIGURES 33–36. SEM images of sand from Longfengtou Beach. Figs 33, 35. Sand grains showing H. fujiannensis attached in grooves (arrows). Figs 34, 36. External girdle view of H. fujiannensis. Scale bars in Fig. 35 = 100 μm, Fig. 33 = 50 μm; Figs 34, 36 = 10 μm.