Lauderia excentrica Lobban, 2015

Lobban, Christopher S., 2015, Benthic marine diatom flora of Guam: new records, redescription of Psammodictyon pustulatum n. comb., n. stat., and three new species (Colliculoamphora gabgabensis, Lauderia excentrica, and Rhoiconeis pagoensis), Micronesica 2015 (2), pp. 1-49 : 6-7

Lauderia excentrica Lobban , n. sp. Figs 43–48

THALASSIOSIRALES Glezer & Makarova : Lauderiaceae (Schütt) Lemmermann , emend. F.E. Round & R.M. Crawford

Samples: GU44I-1, GU44Y-13, GU55B-4, GU66A-3

Dimensions: Diameter 23–26 µm.

Diagnosis: Differing from L. annulata in the larger, reniform, excentric annulus, in the more numerous fultoportulae over the valve face and mantle, and in lacking a ring of longer spines.

Holotype: GU44I-1, slide 494, deposited at California Academy of Sciences , accession # 627427, slide # 220343. Fig. 43.

Type location: GabGab reef, Apra Harbor Guam, 13°26′ 33.63′′ N 144° 38′ 34.25′′ E, associated with filamentous algal turf in a farmer-fish territory, collected by C. Lobban & M. Schefter, 29 Oct. 2007 .

Etymology: with reference to the excentric annulus.

Description: An asymmetrically placed reniform central area is defined by a hyaline ring from which radiate numerous hyaline veins (“costae”); on the wider side some of these branch dichotomously ( Figs 43, 44). Punctae scattered in the central area and usually biseriate between the veins ( Figs 44, 45). Fultoportulae scattered in the central area and occurring along the veins over much of the valve face although less frequent in a zone around the central area ( Figs 44, 45). Spines absent. Numerous fultoportulae on the margin, where anastomosing costae form a “loculate” pattern, as in L. annulata ( Figs 44, 47). One large rimoportula at the edge of the valve furthest from the central area, with a simple circular opening externally ( Fig. 44) and a large labiate process internally ( Figs 46, 48). Fultoportulae in the outer zone are mostly on the veins, whereas those in the zone around the central area are mostly between veins. Fultoportulae consist of a slightly flared external tube 0.5 µm high and a much shorter internal tube (visible on the mantle in

Fig. 48); fultoportulae within the annulus generally had no 5 satellite pores, those in the striae had 2–4 ( Fig. 48). Valves do not appear to be delicate.

Comments: All previously reported taxa were synonymized by Hasle (1974) into L. annulata Cleve, and Round et al. (1990) placed it in its own family. It forms delicate chains in the plankton ( Ricard 1987, figs 140, 147). The ultrastructure of the valve was shown by Hasle (1974, figs 1–3, 6–12), Syvertsen & Hasle (1982), Round et al. (1990, pp. 150–151) Güttinger (1994), and Al-Kandari et al. (2009, pl. 5A, B). Hasle (1974) gives the range of valve diameters as 24–75 µm; the new species is at the lowest end of this range. The present species has not been seen alive, and is represented so far only by a few valves from sites both inside the harbor and on the outer coast. It was perhaps deposited from the water column but the valves seem relatively sturdy, unlike L. annulata , and it may be benthic [cf. Roundia cardiophora (Round) Makarova in our flora]. This species is significant in adding a second taxon to this family.

Mastogloia affirmata (Leuduger-Fortmorel) Cleve Figs 49, 50 Section: Undulatae

Ref. illus.: Hustedt 1931 –1959, fig. 962.

Samples: GU44AX-1

Dimensions: Length 39 µm; width 22 µm; transapical striae 14 in 10 µm, longitudinal striae 10 in 10 µm except for the wider row adjacent to axial area; partecta 3.3 µm wide, 13 in 10 µm.

Diagnostics: Coarsely areolate, those along the raphe notably elongated; apices produced; longitudinal ribs almost straight; partectae very narrowly rectangular.

Comments: Distinguished from the very similar M. bahamensis Cleve ( Hustedt 1931 –1957, fig 963, Hein et al. 2008, pl. 34, fig. 6 and pl. 36, fig. 10), which has irregularly wavy longitudinal ribs, according to Hustedt, and from M. subaffirmata Hustedt (see below) by the much coarser striae. Record based on a single specimen from Guam, but also seen in samples from Yap (unpublished).