Fragilariophyceae: Grammatophoraceae), a New Species with Areolate Valvocopulae, from a Coral Reef

12Diatom 31: 12–17. December 2015 Christopher S. Lobban DOI: 10.11464/diatom.31.12

Grammatophora ornata (Fragilariophyceae: Grammatophoraceae), a new species with areolate valvocopulae, from a coral reef

Christopher S. L

Division of Natural Sciences, University of Guam, Mangilao, GU 96923, USA E-mail: [email protected]

Abstract A new extant species of Grammatophora is distinguished by elaborately areolate valvocopulae. It was collected on blue coral in Apra Harbor, Guam. Valves were narrowly to linear-elliptical, 22–77 µm long by 5–6 µm wide, with transapical striae 19–20 in 10 µm. In these characters valves are very similar to those of G. oceanica and G. marina. e valve is asymmetrical in the apical plane, having a slightly deeper mantle at one end. Valvocopulae were remarkably dierent from other species in having elongate areolae closed by vela, 11–12 in 10 µm, throughout the valvocopula. Septa were planar, inclined towards the center of the cell. Live cells were not observed but spines on both apices suggest that this species may not form the zigzag colonies typical of common Grammatophora species. Key index words: Coral reefs, farmer-sh territories, Guam, Grammatophoraceae, Grammatophora

Introduction damselsh in Guam: G. macilenta W. Smith, G. oceanica (Ehrenberg) Grunow, G. marina (Lyngbye) Kützing Grammatophora Ehrenberg is a marine genus with and G. undulata Ehrenberg oen occur in signicant about 50 extant species and several fossil species (Van- numbers; frustules of G. angulosa Ehrenberg occur spo- Landingham 1971, Round et al. 1990, California Acad- radically (Lobban et al. 2012, Jordan et al. 2009–2015). A emy of Sciences 2011). Several species were extensively species that is distinctive because of the presence of large studied by Sato et al. (2008a, b, 2010). Grammatophora areolae along the length of the valvocopula was recently is commonly recognized by the tabulate frustules joined found in considerable quantity in one sample from my in zigzag chains, and having prominent septa on the main study site. e purpose of this paper is to describe valvocopulae. Although placed in Striatellales: Striatel- this new species. laceae by Round et al. (1990), recent molecular evidence showed that it was unrelated to those and it was placed Methods in a new family, Grammatophoraceae, which cannot yet be placed in an order but is near the Rhabdonemataceae Samples were collected by hand during scuba diving (Lobban & Ashworth 2014b). Valves have porous striae at GabGab reef, Apra Harbor Guam; a detailed descrip- and a narrow sternum and there is an apical pore eld tion of this site was published in Lobban et al. (2012). at each end from which attachment mucilage can be re- e samples were preserved in formalin and later acid leased. ere is also a short pseudoseptum on each valve cleaned by rinsing o excess preservative, then boiling apex. Valvocopulae are closed, with septa lling all but with an equal volume of concentrated nitric acid for a central hole; the septa in dierent species range from 10 min, standing for 24 h, and nally rinsing 10 times nearly at to strongly undulate and are an important tax- with water to reduce the acidity. Drops of the resulting onomic character. Valvocopulae have no pores in most suspension were dried on coverslips for mounting as species, but many have a series of slits around each apex permanent slides in Naphrax (Brunel Microscopes, Ltd., and some have plaques along the abvalvar edge (Round Chippenham, Wilts., U.K.), or onto Whatman cellu- et al. 1990, Lobban & Ashworth 2014b). e other girdle lose nitrate lters and sputter coated with Au–Pd in an bands (pleurae, sensu von Stosch 1975) are porous or SC7620 Mini Sputter Coater (Quorum Technologies, plain, open. East Grinstead, West Sussex, UK). Light microscopy Grammatophora species are common in the epiphytic (LM) observations were made with a Nikon 80i micro- communities of diatoms in algal “farms” of territorial scope with dierential interference contrast illumination and images recorded with a Nikon DS-Fi1 camera and Received 6 April 2015 DS-L2 controller (Nikon Instruments, Redmond, WA, Accepted 7 July 2015 USA). Scanning electron microscopy (SEM) was per- New species of extant Grammatophora 13

formed with a PhenomWorld G2 Pro “desktop” instru- Type locality. GabGab reef, ca. 9 m deep, on blue coral, ment (PhenomWorld US, Hillsboro, OR, USA). Heliopora coerulea, in a farmer-sh (Plectroglyphidodon Terminology follows Hendey (1964) for cell shape, lacrimatus) territory, collected 2 April 2014 by C. Lob- Anonymous (1975) and Ross et al. (1979) for morpholo- ban & M. Scheer while scuba diving. gy and von Stosch (1975) for girdle band elements. Etymology. Ornate, with reference to the appearance of the valvocopula wall. Results Morphology. Frustules in girdle view rectangular; nei- ther live cells nor colonies were observed. Valves were Grammatophora ornata Lobban, n. sp. Figs 1–18 narrowly to linear elliptical (Figs 1–6). Simple pore-like Diagnosis Valves narrowly to linear-elliptical, length areolae occurred in transapical striae with a very nar- 22–77 µm, width 5–6 µm; transapical striae 19–20 in row sternum discernible only in SEM (Fig. 10). ere 10 µm; striae on valvocopula 11–12 in 10 µm, compris- was a pore eld at each apex, not very apparent in LM, ing single areolae closed by vela. Septa straight, slightly and usually a single spine on each apical eld (in some inclined, thickened at central hole. instances the spine appeared absent; in one valve there Holotype. Specimen at 14.2 mm E and 10.4 mm S from were two at each end). ere was an apical rimoportu- the reference mark, slide #1597 (GU44BD-4); common la at each pole (Figs 2, 16, 17). Pseudosepta were not in the sample. Deposited at California Academy of Sci- apparent in girdle view; SEM (Figs 16, 17) showed that ences, accession # 627422, slide # 223029. Fig. 8 is of there was only a shallow pseudoseptum. ere was a the holotype (UOG Diatom Herbarium catalog number slight asymmetry in the valve in the apical plane, where GUD003698). the mantle was slightly deeper at one pole than the other

Figs 1–9. Grammatophora ornata, LM. Figs 1, 2. Valve in valve view at two focal planes, the lower (Fig. 2) showing the rimoportulae (arrows). Figs 3–6. Two valves with valvocopulae at two focal planes each. Fig. 7–9. Frustules in girdle view, showing the ornate valvocopulae. Fig. 7. Recently divided cell with no valvocopulae on the hypothecae. Fig. 8. Holotype specimen showing the straight but slanted septa and the ta- pering pattern of areolae on the advalvar portion of the valvocopulae. Fig. 9. Frustule of a long cell. Scale bar 10 µm applies to all. 14 Christopher S. Lobban

Figs 10–16. Grammatophora ornata, SEM. Fig. 10. Valve in external view. Fig. 11. Valve and valvocopula in oblique abvalvar view, showing septum and internal interareolar thickenings on valvocopula (arrow). Fig. 12. Advalvar view of valvocopula showing hooked part at apex (arrow). Figs 13–16. ree frustules in girdle view, showing valvocopulae with areolae decreasing in length from the apex to the middle, a spine on each apex (arrows on Fig. 13), and the plain pleurae. Fig. 15 also shows the location of the two measurements of mantle depth (dou- ble-headed arrows). Fig. 16. Close-up of frustule in Fig. 15, showing plaques (arrow) and detail of areolae. Scale bars＝5 µm.

(Fig. 15): averages (N＝14) were 2.13 µm vs. 2.57 µm. apices (Figs 13–16); there were no apical slits. e interi- is gave a slightly steeper slope of the apical pore eld or of the valvocopula was thickened between the areolae at one end. Septa were planar, slightly inclined to the (Fig. 11). Because of the slope of the septa, the areolae advalvar side in the middle (Figs 7–9). Septa were thick- decreased in length from the apices to the center (Figs ened around the central opening (Figs 7–9, 11). ere 13–16). e openings in the valvocopula comprised a was a small hook at the apex of the pars interior of the C-shaped slit at each end and, in the longer ones, one or valvocopula (Fig. 12). e advalvar portion of the valvo- two additional slits along the side (Fig. 16). e abval- copula above the septa was perforated with transapically var portion of the valvocopula had no pores, but there elongate, volate areolae, which continued around the were plaques along its abvalvar edge externally (Fig. 16). New species of extant Grammatophora 15

broad transapically elongated areolae as found here. However, G. arctica Cleve has short punctate striae ap- parently along the advalvar portion of the valvocopula (Grunow in van Heurck 1881, pl. 53Bis, g. 3; Hustedt 1931, g. 563; Poulin et al. 1984, gs 16–18). Although Hustedt (1931:38) describes them as traversing the di- viding line between the valve mantle and girdle band (“an der Trennungslinie zwischen Schalenmantel und Gürtelband mit einer durchlaufenden Reihe kurzer, punktierter Striche”), they are clearly on the valvocopula in Grunow in van Heurck (1881). None of the images cited suggest the pattern seen in G. ornata. e septa of G. arctica are at, but the pseudoseptum is notably long, and the valve shape inated in the middle, unlike G. ornata. In G. muellerii Grunow (Grunow in van Heurck 1881, pl. 53, g. 19) and G. arnottii Grunow (Grunow in van Heurck 1881, pl. 53Bis, g. 4) (which Grunow suggested might be a variety of G. muelleri) there is also a line of striae along the advalvar portion of the valvocopula, but again, the pattern does not suggest those of G. ornata, and the septa in both species are markedly wavy. ere are unfortunately no SEM images of the three species compared here (Gaul et al. 1993, Henderson & Re- imer 2003), except for one in Poulin et al. (1984), which does not illuminate the valvocopular striae. On the basis of the valve structure, Grammatophora ornata is dicult to distinguish from G. oceanica and G. marina (Table 1), which are themselves dicult to distinguish, and each has a wealth of varieties and syn- onymies (VanLandingham 1971, CAS Catalog 2011). e morphology and life history of G. marina were studied by Sato et al. (2008a, b). As described and keyed by Hustedt (1931), G. oceanica is narrowly linear, not inated in the center, and has 20–24 striae in 10 µm, whereas G. marina is “mostly” inated in the center and has 15–20 (rarely 20–22) striae in 10 µm. Except in very short cells (Sato et al. 2010), both species have a distinct wave at a short distance from the apex and the rest of the Figs 17, 18. Grammatophora ornata, SEM. Fig. 17. Valve, valvo- septum is at (Hustedt 1931). I have reported G. oceani- copula and pleurae from a short cell. Fig. 18. Detail of valve apex showing rimoportula (arrow) and pseudoseptum (arrowhead). ca from Guam (Lobban et al. 2012, Lobban & Ashworth Scale bars＝5 µm. 2014b) and my illustrations published are consistent with Hustedt’s concept, but G. marina is also present (Jordan et al. 2009–2015, taxa_id/232512). Valves of G. ere were at least two open, unperforated pleurae (Figs ornata have a stria density on the borderline between G. 13–18), one of which had a prominent ligula (Figs 17, marina and G. oceanica. e shape of G. ornata is more 18). smoothly elliptical than either of the others, whereas G. oceanica is linear to linear-lanceolate, and G. marina is Discussion more or less linear and oen somewhat inated at the center. e apical pore elds are also less prominent than On the basis of valvocopula structure, G. ornata ap- Hustedt (1931) shows for those two species. G. marina pears to be a new species. Many species of Grammato- and G. oceanica were absent from GU44BD-4 and valves phora have a series of slits around the apex of the val- of G. ornata could be condently identied; it is so far vocopula, on the advalvar side of the septum, but I have the only sample with it, among more than 100 examined been unable to nd any species, recent or fossil, with from this site over a period of 6 years. Besides the pop- 16 Christopher S. Lobban

Table 1. Comparison of characters of G. ornata and similar species.a

Character G. ornata n. sp. G. oceanica G. marina G. macilenta

Length 22–77 µm 15–150 µm [H]; 32–50 µm 18–100 µm [H]; 32–45 µm 30–150 µm [W]; 66–72 µm Width 5–6 µm 4–8 µm [H]; 3–7 µm 8–15 µm [H]; 4–6 µm 3–4 µm [W]; 4–7 µm Valve shape Narrowly to linear-elliptical Narrowly linear Lanceolate, mostly inated Linear with inated apices at center and center [H] Stria density 19–20 in 10 µm, transapical 20–24 in 10 µm, quincunx “usually 15–20, rarely more 25–31 in 10 µm, regularly and puncta pattern [H]; 24 in 10 µm, predom- than 20–22” in 10 µm, quin- quincunx [H, W] inantly transverse cunx [H]; 18–19 in 10 µm, ±quincunx Pseudoseptum Very shallow Shallow Shallow Deep [H] Septum Planar, slanted One wave in the septum- One wave in the septum- One wave in the sep- body body (except in v. small cells) tum-body [H] Areolae Large, velate areolae through- Apical slits Apical slits Apical slits [H, N] on valvocopula out; striae 11–12 in 10 µm Apical spines Both apices One apex One apex One apex a I give here values from Hustedt (1931) [H], except for G. macilenta (from Witkowski et al. 2000 [W], Navarro 1982 [N]), and my own observations (Lobban et al. 2012, Jordan et al. 2009–2015). Many additional literature records are summarized by Álvarez-Blanco & Blanco (2014) for G. marina and G. oceanica. In addition, Sato et al. (2008a) noted dierences between their materials of G. marina and those of Magne-Simon (1962) that suggested cryptic speciation. ulation in GU44BD-4, where specimens were common, spines in G. marina occur only on the apex not covered I observed single valves in two additional samples from with a mucilage pad, and hypothesized that the spine GabGab that most closely t G. ornata (posted at http:// disturbs the adhesion of sibling valves. Other species www.protistcentral.org/Photo/get/photo_id/4739 and that have been observed to form zigzag chains also /4736), but could nd no girdle views to conrm the have spines at only one end (G. macilenta [Lobban et al. identity. 2012], G. undulata [Jordan et al. 2009–2015]). G. arcuata e pseudoseptum is narrow, but similar to that of G. has no apical spines and forms straight chains (Sato et al. angulosa shown by Sato et al. (2010, gs 22, 29, 30, 32), 2010). G. ornata has spines on both apices, so if Sato’s essentially being a rim that interlocks with a hooked part hypothesis is generally valid for the genus, one predicts of the valvocopula. Sato et al. (2010, gs 99–101) also in- that G. ornata does not form colonies at all. Many of troduced the terms septum-base and septum-body, with the extant and fossil Grammatophora species in the lit- a characteristic angle, θ, between the parts, in species erature were described on the basis of isolated valves or where the septum is “well developed” (i.e., wavy). e frustules, with no indication of colony formation, and apical slits present in some species perforate the valvo- it may turn out that zigzag chain formation is not the copula around the septum-base. In G. ornata, the areolae predominant habit among Grammatophora species, al- continue all along the valvocopula, the septum is planar, though it is the habit of the most common species. and there is no distinction between septum-base and septum-body. Acknowledgements Although the specimens came from a collection of Heliopora coerulea (an octocoral rather than a scleractin- e microscopes used at U. Guam were funded by ian coral), it is not clear whether the cells were attached NIGMS RISE award GM063682 and US Dept. Education directly to the animal or associated with a biolm. I MSEIP award P120A040092. I thank María Scheer for have recently observed a layer of Cocconeis borbonica continuous support and encouragement with the diatom Riaux-Gobin & Compère on this species of coral, with research, Shinya Sato for helpful discussions about this many other diatoms attached to the biolm (Jordan et species, and the Commanding Ocers of Naval Base al. 2009–2015, taxa_id/586031), and Lucanicum concate- Guam for access to study sites there. Special thanks to natum Lobban & Ashworth (2014a) and other taxa have Moses Francisco at U. Guam R.F. Kennedy Library for been seen directly attached to the coral. his persistence in acquiring old papers for this project A nal aspect of interest is the question of colony and many others. formation. While some species of Grammatophora form zigzag chains̶indeed Round et al. (1990) give this as a character of the genus, Sato et al. (2008b) showed that New species of extant Grammatophora 17

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