Hyalosynedra prasadii Theriot and Ashworth

Sabir, J. S. M., Theriot, E. C., Lobban, C. S., Alhebshi, A. M., Al-Malki, A. L., Hajrah, N. H., Khiyami, M. A., Obaid, A. Y., Jansen, R. K. & Ashworth, M. A., 2018, Systematics of araphid diatoms with asymmetric rimoportulae or densely packed virgae, with particular attention to Hyalosynedra (Ulnariaceae, Bacillariophyta), Phytotaxa 347 (1), pp. 1-49 : 18-19

Hyalosynedra prasadii Theriot and Ashworth ( Figs 37–43 )

Holotype: — ANSP G. C. 59325

Isotypes: — ECT 4118 in the Theriot collection at the UT Austin.

Type locality: —Epiphyte on Anadyomene spp. thalli from Rabbit Key Basin, Florida, USA (24 o 58.60’ N, 80 o 50.41’ W).

Material studied: —Wild material and cultured (21IV14-4D “araphid-31”) material isolated from the type locality: ECT 4118, epiphyte samples taken from Anadyomene spp. thalli from Rabbit Key Basin, Florida, USA (24 o 58.60’ N, 80 o 50.41’ W).

Description: —Valves observed were 43.1–109.3 μm long and 3.6–6.9 μm wide ( Figs 37–40 ). Outlines were lanceolate, with sides being convex to near the apex where there was often a slight reversal in curve, producing slightly protracted apices. The sternum was strongly lanceolate, about twice as wide in the middle as at the apices. Virga densities were 42–48 in 10 μm. Pore densities in the ocellulimbus were 5.5–8.0 in 10 μm ( Figs 41–43 ). Ocellulimbi were about 10–14 pores wide and 3 pores tall and overhung with 1–4 small spines. Each asymmetric rimoportula was positioned inside a slight depression at each apex. The rimoportula, however, was often very close to the valve end compared to other species of Hyalosynedra . Girdle bands were without pores and open ( Fig. 41 ).

Remarks: — Hyalosynedra prasadii was isolated from Rabbit Key Basin along with H. laevigata , and was recovered as sister to all other nominal Hyalosynedra species of this study in the molecular analysis ( Fig. 1 ). The sternum of H. laevigata was linear, that of H. prasadii was lanceolate, and the former was observed to be much larger than the latter.

Etymology: —This species was named for A.K.S.K. Prasad, in honor of his many contributions to our understanding of diatom diversity, especially that of the Florida coast.

Figures

FIGURES 1. Maximum likelihood tree of smallest clade containing all ocellulimboid taxa and hyalosynedroid taxa from concatenated nuclear SSU and chloroplast rbcL and psbC sequences. Bootstrap support values less than 50% are omitted. Bars indicate distribution of characters discussed in text: symmetric versus asymmetric rimoportulae, bilayered structure, densely packed fascicles and ocellulimbi. Presumed derived state in black background with white letters. The question mark indicates that while Thalassionema has symmetric, rather than asymmetric rimoportulae, that highly similar genera Lioloma and Thalassiothrix have species with asymmetric rimoportulae, but their phylogenetic affinities have not yet been studied with morphological or molecular data. Names in bold are new taxa described in this paper.

FIGURES 37–39. Hyalosynedra prasadii from ECT4118. 37. LM of larger specimen. 38. LM of smaller specimen. 39. SEM of valve and partially disassociated girdle bands.

FIGURES 40–43. Hyalosynedra prasadii from ECT4118. 40. Interior of whole valve. 41. Apex of partially disassociated valve, showing unornamented girdle bands and sunken ocellulimbi of two valves. 42. Detail of apex interior. 43. Detail of apex of tilted valve showing fascicle morphology.