Divergita biformis, 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 : 242

Divergita biformis, Lobban , sp. nov. Figs. 26–28 .

Diagnosis:— Valves straight, lanceolate with weakly capitate apices. Striae biseriate and decussate only on the mantle, striae on valve face mostly uniseriate with quadrangular areolae; sternum linear, very narrow.

Description:— Live cells not observed. Valves seen in LM ( Figs 24, 25 ) were from different samples from the SEM holotypes and could not be identified to D. divergita vs. D. decipiens (see below). Valves straight, 76 µm long, 4 µm wide, lanceolate with weakly capitate apices ( Fig. 26 ). Striae 26–28 in 10 µm, biseriate on the margin with triangular areolae alternating and thus forming a decussate pattern, becoming largely uniseriate on the valve face with up to four quadrate areolae ( Figs 27, 28 ). Sternum linear and very narrow. A hyaline area at each apex with a rimoportula in each. Apical pore field apparently with three rows of pores and not sunken.

Holotype hic designatus:— Figs 26–28 from stub 1116 ( GUAM diatom herbarium, catalog # 701116), according to Article 40.5 of the International Code of Nomenclature for algae, fungi, and plants (Shenzhen Code) ( Turland et al. 2018). Registration: http://phycobank.org/102756.

Type locality: — F.S. M. Yap: reef flat near channel to Colonia , 13.464 N, 144.656 E, dense farmer fish turf scraped from Acropora coral, ca. 1 m deep, sample Y45-5. C.S. Lobban and M. Schefter, 31 May 2014 .

Etymology:— named for the two patterns of areolae in the striae.

Additional Records:— F.S.M. Yap: Nimpal MPA, Y36-2!, Y36-4!; GUAM: GU52Q-1a!, GU44AP-8!

Comments:— Similar specimens occurred in several samples from each of Guam and Yap but were always rare. There was considerable variation among these specimens and some clear differences, so I have chosen to define two species on the basis of ultrastructural details. For this species, defined on the specimen from Y45-5, I found no internal aspect but for D. decipiens the internal view shows the characteristics of Divergita , which do not vary between species.

Figures

FIGURES 24–32. Divergita straight species. Figs 24, 25. LM images of Divergita spp. Fig. 24. Divergita sp., Yap specimen is a possible example of D. biformis, but is from a different location (Y36) from the SEM holotype. Fig. 25. Divergita sp., Guam specimen, possibly D. decipiens, from the same location (GU52) as the holotype, but a different collection date. D. biformis has also been seen in SEM of samples from GU52, it is not possible to tell which species is shown here. Figs 26–28. Divergita biformis, sp. nov., SEM. Holotype specimen whole mount on stub 1116, Y45-5, whole valve and details of apex and center, showing narrow, linear sternum and areola pattern. Figs. 29–33. Divergita decipiens, sp. nov. SEM. Figs 29–31. Holotype specimen whole mount on stub 566, GU52R-2, external views, showing broad, lanceolate sternum. Fig. 32. Disassociated frustule from same sample, showing interior features of rimoportula (arrow) and foramina, along with external view showing that this is not Hyalosynedra. Scale bars: Figs 24–26, 29 = 10 µm, Figs 27, 28, 30–32 = 2 µm.