Bacterosira constricta (Garrder) J.S. Park & J.H. Lee, 2016

Park, Joon Sang, Alverson, Andrew J. & Lee, Jin Hwan, 2016, A phylogenetic re-definition of the diatom genus Bacterosira (Thalassiosirales, Bacillariophyta), with the transfer of Thalassiosira constricta based on morphological and molecular characters, Phytotaxa 245 (1), pp. 1-16 : 11-14

Bacterosira constricta (Garrder) J.S. Park & J.H. Lee , comb. nov. et emend.

Basionym: Thalassiosira constricta Garrder , TromsØ Museums Arshefter, Naturhistorisk Avdeling 55: 6. 1938.

Frustules rectangular in girdle view, length of pervalvar axis 13.5–23.0 μm. Chloroplasts many, discoid-shaped in valve view and elliptically shaped in girdle view. Cells sometimes solitary, often in chain-like colonies connected by β- chitin threads extruded from central fultoportulae. Epicingulum composed of five open bands. Valvocopula covered with transverse rows of fine pores on the advalvar edge, abvalvar portion of valvocoupla is hyaline. Copula with 3 or 4 rows of fine pores along the advalvar edge, abvalvar edge is hyaline. A total of 3 pleurae present. Girdle band openings are offset in a dextral pattern. Valves circular with a weakly silicified valve face and a more heavily silicified valve mantle, 9.8–25.7 μm in diameter. Poroid areolae on the valve face, loculate areolae on the valve mantle. Areolae arranged into radially oriented biseriate rows along ribs on the valve face, areolae uniseriate on the valve margin. Areolar density 36–44 per 10 μm on the valve face, 37–46 per 10 μm on the valve margin, and 41–51 per 10 μm on the valve mantle. A cluster of 0–14 fultoportulae in the valve center. Internally, central fultoportulae consist of an internal tube surrounded by three or four satellite pores. Externally, fultoportulae have short, tube-like extensions. A ring single ring of marginal fultoportulae on valve mantle, 5–7 per 10 μm. Internally marginal fultoportulae with internal extensions surrounded by four satellite pores, externally with short tube-like extensions. For central and marginal fultoportulae, satellite pores are positioned in a visible caldera-like depression surrounded by a cowling. One rimoportula in line with and positioned between two marginal fultoportulae, internally with a labium and externally with a vertically elliptic pore.

Emended description of the genus Bacterosira Gran

Cells mostly in colonies, with either directly abutting cells or separated by β- chitin threads extruded from central fultoportulae. Valve structure includes uni- or biseriate poroid areolae between radial ribs on the valve face and loculate areolae on the valve mantle. A central cluster of fultoportulae internally surrounded by 2 to 4 satellite pores and one ring of marginal fultoportulae by 4 satellite pores. Fultoportulae with fully exposed satellite pores, each in a caldera-like depression and surrounded by a defined cowling. A single rimoportula located between two marginal fultoportulae.