Gato hyalinus Lobban & J.N. Navarro, 2013

Lobban, Christopher S. & Navarro, J. Nelson, 2013, Gato hyalinus gen. et sp. nov., an unusual araphid tube-dwelling diatom from Western Pacific and Caribbean islands, Phytotaxa 127 (1), pp. 22-31 : 23-28

Gato hyalinus Lobban & J.N. Navarro sp. nov. ( Figs 1–21 )

Cellulae coloniales in tubis brevibus mucilaginis interdum ramosis. Chloroplasti numerosi lenticulares elongati. Valvae ovales parum angustatae versus basem, longitudine 30–40 µm, latitudine 13–15 µm. Striae transapicales tenuissimes, ca. 60–70 in 10 µm, paralleles praeter e extremo apicali sterni radians et prope polum basalem obliquaras. Rimoportula poli basalis in palla valvarum; rimoportula poli apicalis ad vel ultra extremum apicali sterni, prope pallam. Pori marginati non solum 3–5 in quoque lato poli basalis, in exemplum valvae rimoportula basali ferens una cum paribus striarum obliquarum e unusquaque versus sternum extensarum, sed etiam aliquot irregulariter in striis transapicalis prope marginem positis.

Cells colonial in short, sometimes branched mucilage tubes. Plastids numerous, elongate lenticular. Valves oval, slightly tapered toward foot pole, length 30–40 µm, width 13–15 µm. Transapical striae extremely fine, ca. 60–70 in 10 µm, parallel except radiating from head pole of sternum, and oblique at foot pole. Foot pole rimoportula on valve margin; head pole rimoportulae at or beyond end of sternum, near edge of mantle. Rimmed pores 3-5 on each side of the foot pole, on valve with basal rimoportula associated with pairs of oblique striae extending from each toward the sternum, and several others irregularly placed on transapical striae near margin.

Type:— GUAM. Apra Harbor, GabGab reef, 13° 26' 33.63" N, 144° 38' 34.25" E, acid cleaned material of diatoms, epiphytic on algal turf in farmer fish territories, collected 20 June 2009, GU44Z-15, strewn on microscope slide and filtered onto Millipore® filter paper. (Specimen circled on microscope slide marked CAS #223005, accession #627383, holotype, designated here; SEM stub of collection GU44Z-15 [deposited as holotype of the bleakeleyoid diatom Perideraion decipiens Lobban in Lobban et al. (2011)], CAS #627385, isotype, designated here).

Etymology:—hyaline, with reference to the lack of structure visible in LM.

Additional specimens examined: — GUAM: Agana Boat Basin , epiphytic on algal turf just below low water line, 29 November 1988, GU26A; GabGab, Apra Harbor, epiphytic on algal turf in farmer fish territories, 3 August 2008, GU44O-F, 1 September 2008, GU44P-B, 28 March 2009, GU44W- 10 and 10 May 2009, GU44Y-13; Pete’s Reef, Facpi Pt., 7 September 2008, GU55A-C . PALAU. Toachel ra Ngel, Ulebsechel I., 13 April 2009, PW2009-40 . PUERTO RICO: Caja de Muertos Island , 27 December 1985; Enrique Reef, 7 m deep epiphyte on the red alga Amphiroa sp. , 8 April 1994, slide #C94-6 . JAMAICA: Sponge Gardens , St Ann, 27 m deep, 19 November 1995, slide #A96-14 .

Observations:— Colonies ( Figs 1–4 ) are a few cells long, sometimes branched, each cell at the end of a section of tube, from which the next section arose off-center; Fig. 4 suggests at least a temporary septum within the tubes. In Fig. 1 there appear to be cohabitant naviculoids in the tubes; these have not been commonly observed. Gato hyalinus cells are broadly oval, slightly narrower at the basal end, apparently with many elongate-lenticular plastids ( Figs 1–4 ), and the cells arranged in the colonies with the narrower pole toward the base. Frustules are also slightly tapered in girdle view ( Fig. 4 ). In acid-cleaned valves in LM ( Figs 5, 6 ), the rimoportulae can be seen, and sometimes a faint sternum, but the striae are too fine to resolve and the valves appear hyaline.

In SEM, the valve surface is smooth, with rounded margins, striae 60–70 in 10 µm consisting of uniseriate rows of simple circular pores ( Fig. 19 ) that extend to the valve border ( Figs 7, 8, 10, 11 , 20 ). In places, the pattern could be described as quincunx (e.g., Fig. 13 ) but the spacing between pores in the striae is generally insufficiently consistent. There is a narrow, irregular break in the striae along the centerline, barely constituting a sternum ( Figs 7–16 , 20 ). Striae are parallel except at the head pole, where they radiate from the end of the sternum ( Figs 16 , 20 ), and in association with the rimmed pores ( Figs 8, 10 ). Both valves have a small rimoportula at the head pole near the valve apex, at or beyond the end of the sternum ( Figs 9 , 12, 13, 16 , 20 ), but the two valves are different at the foot pole. There, only one valve of the frustule has a rimoportula and more strongly oblique striae —the “cat’s whiskers” for which the genus is named ( Figs 8, 10 ), the other valve lacks a rimoportula at the foot pole ( Figs 12–20 ). Both foot poles have several large rimmed pores, i.e., that have slightly thickened rims internally ( Figs 7, 8, 10, 11 , 15, 17 ). There are two series of rimmed pores, typically 4–5 on each side of the foot pole on the valve with a rimoportula; there are only 3 on those without a foot-pole rimoportula. In addition several irregularly placed pores occurred near the foot pole on both valves, interrupting 2 or more striae ( Fig. 15, 18 ), but are not observed near the head pole. On valves with a basal rimoportula there are pairs of oblique striae extending from the sternum to the basal set of rimmed ( Figs 7, 8, 10, 11 ); these are not obvious on valves without a basal rimoportula, where only some irregularity in the striae was observed ( Figs 14, 15, 17 ). We have little information on girdle bands, but they appear to be finely punctate ( Fig. 21 ), similar to the valve surface.

Genera morphologically most similar to Gato are Florella and Licmophora . We do not suggest that either of these is related to Gato . Besides Navarro’s (1982, 1996, 2002) descriptions, we have observed Florella portoricensis Navarro (1982: 248 , 258, emend Navarro 1996: 304) ( Fig. 22 ) and Florella pascuensis Navarro (2002: 284) ( Fig. 23 ) from the Republic of the Marshall Islands; this is the first confirmed report of these species from that country, and the first confirmed record of F. portoricensis from the Pacific Ocean. In addition Lobban et al. (2012) observed and cultured samples of F. pascuensis from Guam. The valves of Florella spp. are isopolar with parallel striae of cribrate areolae continuing unbroken to the valve border from an indistinct sternum; there are no pore fields. F. portoricensis has a series of rudimentary rimoportulae at each apex, indistinguishable from areolae except in internal SEM views, whereas F. pascuensis has two labiate rimoportulae, one at each end of the sternum, visible even in LM ( Navarro 1996, 2002). F. pascuensis also has a unique pattern of slit-like areolae at each end.

Frustules of Licmophora spp. , on the other hand, are heteropolar and heterovalvar. A series of (5 to>30) simple slits at the foot pole is developed into a distinctive multiscissura ( Figs 24, 25 ). The areolae ( Fig. 24 ) are separated by virgae and viminae (Honeywill 1988). Although the rimoportulae of most Licmophora species are labiate rimoportulae ( Fig. 25 ), in L. flabellata (Carmichael mscr. 1826, according to Agardh) C. Agardh (1831: 41, emend Sar & Ferrario 1990: 404) the head pole rimoportula and the unique series of extra rimoportulae along the sternum lack labia ( Fig. 26 ). These have been characterized by Sar & Ferrario (1990) as “sessile rimoportulae” and are perhaps similar in structure (though not position) to the rimmed pores in Gato .

Figures

FIGURES 1–6: Gato hyalinus light microscopy. Figs 1–4: Live colonies and cells showing mucilage tubes and plastids. Fig. 1. Colony showing branching. A Striatella unipunctata cell (S.u.) has attached to the end of one tube and there appear to be naviculoid cells inside the tubes (some indicated by arrows). Top part of colony partially overlain by a ribbon of Hyalosira interrupta (H.i.) (GU44O-F). Fig. 2: Dividing cell in near-girdle view at apex of colony, at two focal planes. A Licmophora sp. cell (L.) is attached to the outside of the tube (GU44O-F). Fig. 3. Cell in valve view (GU44O-F). Fig. 4: Cells in valve and girdle view with some evidence of a septum (arrow) within the mucilage tube (GU44W-10). Figs 5–6: Acid cleaned valves in LM, oriented with basal pole to left. Fig. 5: Valve at two focal planes showing rimoportulae at both poles (arrows) and faint sternum (GU44Z-15). Fig. 6: Valve with two rimoportulae (arrows), sternum not visible (GU44Z-15). Scale bars: Figs 1–4 = 20 µm; Figs 5, 6 = 10 µm.

FIGURES 7–11: Gato hyalinus, SEM of valves with rimoportula at foot pole. Figs 7, 8: External view of valve and detail of basal pole showing external opening of rimoportula (arrow Fig. 8, also showing apical rimoportula opening, arrow in Fig. 7) and the two rows of rimmed pores with associated oblique striae (“cat’s whiskers”). Fig. 9: Internal view of valve with rimoportulae at both poles (GU44P-B). Figs 10, 11: Details of basal pole with rimoportula in external and internal views (Puerto Rico sample). Scale bars: 7, 9 = 10 µm; 8 = 5 µm; 10, 11 = 2 µm.

FIGURES 12–19: Gato hyalinus, SEM of valves without rimoportula at foot pole. Figs 12–14: Internal view of valve with rimoportula only at apical pole and detail of basal and apical poles (GU55A-C). Apical detail shows rimoportula at end of sternum. Basal detail shows irregular striae and rimmed pores. Figs 15, 16: External details of basal and apical poles of a valve with no basal rimoportula (GU44Z-15). Fig. 15. Basal pole shows three additional rimmed pores (arrows) interrupting transapical striae. Fig. 16: Apical pole shows rimoportula beyond the end of the sternum within the radiating striae. Figs 17, 18: Internal details of basal and apical poles of a valve with no basal rimoportula (GU44Z-15). Fig. 17: Detail of rimmed pores at the basal pole. Fig. 18: Detail of additional rimmed pore. Fig. 19: Detail of areolae along a fracture through the valve (Puerto Rico sample). Scale bars: Fig. 12 = 10 µm; Figs 13–16 = 5 µm; Figs 17, 18 = 1 µm; Fig. 19 = 500 nm.

FIGURES 20–26: Figs 20, 21: Gato hyalinus, SEM. Fig. 20: Head pole showing end of sternum (arrow), radiating striae, and rimoportula (GU44Z-15). Fig. 21: Portion of girdle bands (internal aspect) (Puerto Rico sample). Fig. 22: Florella portoricensis, LM, acid cleaned valve (RMI-M1: 5 m deep, Mile 28, Laura, Majuro Atoll, Marshall Islands). Fig. 23: Florella pascuensis LM, acid cleaned valve, showing a rimoportula (arrow) and one of the rows of transapical slits (arrowhead) (RMI-J5: 1 m deep reef on Kabbenbock Islet, Jaluit Atoll, Marshall Islands). Figs 24–26: Licmophora spp., SEM. Fig. 24: Foot pole of Licmophora proboscidea?, external view showing areolae, rimoportula opening, and multiscissura with 5 slits (GU41D-A1). Fig. 25: Foot pole of Licmophora sp. showing internal and external details of multiscissura (11 slits) and rimoportula. Note absence of rimoportula on the valve in external view. (Palau specimen.) Fig. 26: Licmophora flabellata, internal view of apex showing an apical rimoportula at end of sternum (arrow), plus 2 additional rimoportulae along the sternum (Puerto Rico specimen). Scale bars: Fig. 22, 23 = 10 µm; Fig. 24 = 5 µm; Figs 21, 26 = 2 µm; Figs 20, 25 = 1 µm.