Licmophora graphis, 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 : 238-241

Licmophora graphis, Lobban , sp. nov. Figs 18–23

Diagnosis:— Extremely delicate, linear valve with exceedingly fine striae not resolved in LM, 42–44 in 10 µm at base, ca. 60–70 in 10 µm toward apex.

Description:— Multiple plastids ( Fig. 18 ). Valves linear for most of the length, with an abrupt narrowing to the basal pole, extremely weakly silicified ( Figs 19–23 ). Length 44–69 µm; width 7–10 µm; striae 42–44 in 10 µm at base, ca. 60–70 in 10 µm throughout the linear part and lacking vimines except at the basal pole. Sternum very narrow except notably wider near basal pole ( Figs 20, 22 ). Multiscissura with 12–14 slits ( Figs 20, 22 ). Apical rimoportulae on both valves ( Fig. 21 arrows).

Holotypus hic designatus:— Figs 19–21 from stub 718 ( GUAM diatom herbarium, catalog # 700718), 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/102755 .

Type locality:— GUAM: Apra Harbor , GabGab reef, 13.443 N, 144.643 E., depth ca. 8 m, epiphytic on seaweeds in territory of farmer fish Plectroglyphidodon lacrimatus , sample GU44BJ-3. C. Lobban and M. Schefter, 8 Feb. 2015 .

Etymology:— L. graphis (f) = pencil (noun in apposition), from the shape of the frustule.

Additional Records:— GUAM. Apra Harbor, GabGab reef, GU44U-2!, GU44CA-1!, GU68F-1!; Apra Harbor, Outhouse Beach, GU52AA-1!, GU52AA-3!, Agat, Rizal Beach, GU53E-2!, Agat, Pete’s Reef, GU55E-2!, Agat, Anae Caverns, GU80A-3!. MARSHALL ISLANDS. Bakir Atoll, BA-1!, BA-2!.

Comments:— This species dissolves in acid cleaning, and I have been able to observe it only in live preparations and whole-mount SEM. It was commonly seen in small numbers.

Ulnariaceae E.J. Cox (nom. prov.)

Divergita Sabir & Theriot in Sabir et al. 2018: 21

The recent paper by Sabir et al. (2018) helped clarify Hyalosynedra D.M. Williams & Round 1986: 316 and related genera, including two new genera, Divergita and Stricosus Sabir & Theriot in Sabir et al. 2018: 29. Divergita and Hyalosynedra both have asymmetrical rimoportulae, with the apical side small and the other partly curved around it, like a parrot beak, whereas the rimoportulae in Stricosus are symmetrical. Divergita has both straight and curved species and was further defined by Sabir et al. (2018) as “distinguished from similar genera by areolae which form a decussate pattern externally” and having a lanceolate sternum; the striae are visible in LM. However, I have encountered several scarce species of Divergita that have decussate striae only on the margins and edge of valve face, then becoming uniseriate transapical striae. In LM ( Figs 24, 25 ) the straight species were indistinguishable from one another. I present here two straight species, defined on samples from Yap and Guam, and one curved species found so far only from two atolls in the Marshall Islands, but included because the comparison is instructive.

Figures

FIGURES 18–23. Licmophora graphis. SEM except Fig. 18 DIC. Fig. 18. Living cells epiphytic on ectocarpoid phaeophyte filament, showing numerous small elliptical plastids clustered around the nucleus, GU44U-2. Figs 19–21. Holotype specimen whole mount on stub 718, GU44BJ-3: entire frustule and details of base and apex, showing change in stria density and presence of two apical rimoportulae (arrows). Figs 22, 23. Base and apex of specimen from GU80A-3. Scale bars: Figs 18, 19 = 10 µm, Figs 20–23 = 5 µm.

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.