Parlibellus paschalis Lobban, 2021

Lobban, Christopher S., 2021, New species of benthic marine diatoms (Bacillariophyta) from the Western Pacific islands of Guam and Yap, Phytotaxa 508 (3), pp. 235-265 : 251-252

Parlibellus paschalis Lobban , sp. nov. Figs 70–78 .

Diagnosis:— Differing from P. delognei ( Van Heurck 1880: pl. 11) E.J. Cox 1988: 19 in lacking the cuniculus and pores in the central area and smaller size, and from P. berkeleyi ( Kützing 1849: 106) E.J. Cox 1988: 21 in width and stria density.

Description:— Tube-dwelling cells with plastids reminiscent of a hot cross bun in valve view, a butterfly in girdle view ( Figs 70–72 ). Frustules, often remaining together after acid cleaning ( Fig. 73 ), with numerous copulae ( Fig. 74 ). Valves elliptico-lanceolate, 28–35 µm long, 10.5–12.5 µm wide ( Figs 75–78 ). Striae 25–26 in 10 µm except slightly more distant (21 in 10 µm) in those adjacent to central area, weakly radiate in the central area, otherwise parallel, continuing around the apices ( Figs 75–78 ). Striae punctate, the external areolae openings circular to transapically elongate, internally circular. Areolae closest to the raphe sternum somewhat more prominent ( Fig. 77 , arrow). Central area lacking isolated pores. External central raphe endings 4–6 striae apart, straight, extending into the narrowly oval central area, which as defined by the line of areolae is 11–12 striae long. External terminal raphe endings subapical (ca. 5 striae short of apex) with a small hook into a small hyaline area 1–2 striae wide. Internal raphe endings straight, a small helictoglossa at each terminus; no cuniculi at the central endings.

Holotype hic designatus:— specimen at 16.1 mm E and 9.7 mm S of the mark on slide 192, deposited at ANSP, accession # ANSP-GC20094 . Fig. 75 . Registration: http://phycobank.org/102762.

Type locality:— GUAM: Apra Harbor , GabGab reef, 13.443 N, 144.643 E, farmer fish ( Plectroglyphidodon lacrimatus ) territory 7–8 m depth, sample GU44L-C. C.S. Lobban and M. Schefter, 2 March 2008 .

Etymology:— paschalis , L. adjective referring to Easter, with reference to the resemblance of the live cells in valve view to the Eastertime bakery item, hot cross buns.

Additional Records:— GUAM: GabGab reef, Apra Harbor, GU44I-2!, GU44K-6!.

Comments:— This species is most like P. delognei f. elliptica ( Lobban 1983: 287) Cox 1988: 21 but differs in lacking the cuniculus that is characteristic of both forms of delognei , along with associated pores in the central area. [A cuniculus ( Ross et al. 1979, Cox 1978) “comprises a simple pore in the external central area connecting with an elongate perforate raised structure terminating the internal raphe fissures in the central area.”] It is also shorter and narrower than that form, though wider than P. berkeleyi . The colony structure is similar to the narrow threads of the nominate variety of P. delognei but much different from the large, cold-water colonies of var. elliptica ( Cox 1988, Lobban 1983). The stria density is higher than other similar species ( Table 2), including P. berkeleyi (16–18 in 10 µm).

Figures

FIGURES 70–78. Parlibellus paschalis. LM DIC except SEM Figs 77, 78. Figs 70–72. Live cells in different orientations showing plastids resembling hot cross buns in valve view (Fig. 70), butterflies in girdle view (Fig. 71), and obliquely, GU44L. Fig. 73. Several cells still attached in colonies, tube material not visible, GU44K-6. Fig. 74. Single frustule in girdle view, GU44K-6. Fig. 75. Holotype valve, GU44L-C. Fig 76. Valve from GU44K-6. Figs 77, 78. SEM of valves in exterior aspect, showing line of prominent pores along each side of sternum (arrow), and interior aspect showing lack of cuniculi in central nodule; GU44L-C. Scale bars: Figs 70–72 = 20 µm, Figs 73–78 = 10 µm.