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SPICATICRIBRA KINGSTONII, GEN.NOV. ET SP. NOV. (THALASSIOSIRALES,BACILLARIOPHYTA) FROM GREAT SMOKYMOUNTAINS NATIONAL PARK, U.S.A.Jeffrey Johansen a , Patrick Kociolek b & Rex Lowe ca Department of Biology, John Carroll University, University Heights,OH, 44118, U.S.A.b California Academy of Sciences, 875 Howard Street, San Francisco,CA, 94103, U.S.A.c Department of Biological Sciences, Bowling Green State University,Bowling Green, OH, 43403, U.S.A.Published online: 31 Oct 2011.

To cite this article: Jeffrey Johansen , Patrick Kociolek & Rex Lowe (2008) SPICATICRIBRA KINGSTONII,GEN. NOV. ET SP. NOV. (THALASSIOSIRALES, BACILLARIOPHYTA) FROM GREAT SMOKY MOUNTAINSNATIONAL PARK, U.S.A., Diatom Research, 23:2, 367-375, DOI: 10.1080/0269249X.2008.9705763

To link to this article: http://dx.doi.org/10.1080/0269249X.2008.9705763

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Diatom Research (2008), Volume 23 (2), 367-375

SPICATICRIBRA KINGSTONII, GEN. NOV. ET SP. NOV. (THALASSIOSIRALES, BACILLARIOPHYTA) FROM

GREAT SMOKY MOUNTAINS NATIONAL PARK, U.S.A.

Jeffrey dohansen' Department of Biology, John Carroll University,

University Heights, OH 44118, U.S.A.

Patrick Kociolek' Diatom Collection, California Academy of Sciences, 875 HowardStreet, San Francisco, CA 94103, U.S.A.

Rex Lowe Department of Biological Sciences, Bowling Green State University,

Bowling Green, OH 43403, U.S.A.

A new genus and species in the Thalassiosiraceae, Thalassiosirales is described from Fontana Lake, a reservoir in the Tennessee River drainage, North Carolina, which makes up much of the southern boundary of Great Smoky Mountains National Park. The newly described taxon, Spicaticribra kingstonii, most closely resembles Thalassiosira, but differs in several key aspects. The newly proposed genus is based upon the presence of spicate cribra that do not match up to the external openings of the areolae and the absence of fultoportulae on the valve face. The internal cribra of Spicaticribru are superficially similar to the cribral patterns of T. pseudonunu and T. guillardii, but these species are lightly silicified forms that do not have round or hexagonal areolae visible in external views. Additionally, Spicuticribru lacks external extensions on the marginal fultoportulae, a condition which is unusual for Thalassiosira.

INTRODUCTION The diatom order Thalassiosirales Glezer et Makarova is well defined morphologically,

being comprised of those radially symmetrical forms with fultoportulae and internal cribra (Fryxell 1974, 1977, Hasle & Fryxell 1977). The order has been dissected recently to recognize the diversity of forms within it (e.g. Round et al. 1990, Nikolaev & Hanvood 2002, Kaczmarska et al. 2005).

Our understanding of forms closely allied within the freshwater Thalassiosirales has increased greatly in the last two decades, as new genera from fossil and recent habitats have been described. In fossil deposits, the genera Mesodictyon Theriot & Bradbury (1987) Plioceanicus Round & HAkansson (1 992), Tertiarius Hikansson & Khursevich (1997), Tertiariopsis Khursevich et al. (2002), Mesodictyopsis Khursevich et al. (2004), and Stephanopsis Khursevich & Fedenya in Khursevich et al. (2000) have been differentiated based on the organization and structure of the fultoportulae and rimoportulae, and a large

' Each co-author contributed equally to this publication; order of authorship was determined by alphabetical order of family names. All authors will accept correspondence: johansen@jcu.edu, pkociolek@calacademy.org, lowe@bgsu.edu ' Present address: J. Patrick Kociolek, Director, Museum of Natural History, 21 8 UCB, University of Colorado, Boulder, CO 80309, U.S.A.

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368 J. JOHANSEN, P. KOCIOLEK & R. LOWE

number of new species have expanded or refined our concepts of existing genera (Kociolek & Khursevich 2001, Serieyssol 1993, Serieyssol et al. 1998). In recent habitats, genera such as Thalassiocyclus Hikansson & Mahood 1993, Stephanocostis Genkal & Kuzmina 1985, and Crateriportula Flower & Hikansson 1994 have been established based on features relating to areolae, portulae and rib structure. The genus Cyclotubicoalitus Stoermer et ul. was established based on the unique structure of external processes (Stoermer et al. 1990). Other recent species in established genera (e.g. Stephanodiscus, Cyclotella, Cyclostephanos, Thalassiosira) have also been described (e.g. Hikansson 1990, Pienaar & Pieterse 1990, Tanaka 2000, Tuji & Kociolek 2000, Guerrero & Echenique 2002), providing further expansion of our knowledge on the valve morphology and distributions of these ecologically important taxa.

Recently, a large number of researchers have been involved in the All Taxa Biodiversity Inventory (ATBI) in Great Smoky Mountains National Park, an effort to document the diversity of all life in the park (Pedersen 1999, Sharkey 2001). We have been involved in documenting the algae of the park (Gomez et al. 2003, Johansen et al. 2004,2005, Casamatta et al. 2006). In the present report, we describe a new genus and species of Thalassiosiraceae based on valve ultrastructure.

MATERIALS AND METHODS

Samples were collected from Fontana Lake, a reservoir created in 1944 on the Tennessee River. The samples containing Spicaticribru were: 1 ) middle of Lake, between Noland and Fomey Creek inlets, plankton tow, pH 4.7, GSM10/22/04-6a, 35" 26.861' North latitude 83" 30.667' West longitude; collected 22 October 2004; 2 ) Open water plankton tow, pH 5.0, GSM10/22/0411, 35" 26.01 1' North latitude; 83" 35.599' West longitude, collected 22 October 2004; 3) drippy rock scrape, middle of Noland Creek as it opens into Fontana Lake, GSM3/7/0&5, 35.26.632 North latitude; 83.3 1.690 West longitude, collected 7 March 2004.

The samples were cleaned in boiling nitric acid (Patrick & Reimer 1966) and a subsample was mounted in Naphrax for examination in an Olympus BX5 1 photomicroscope at 1 OOOx magnification with high-resolution differential interference contrast microscopy (DIC, n.a. of objective = 1.35). Images were captured using a Spot Insight digital camera at a magnification of 2 5 0 0 ~ .

A second portion of the cleaned sample was transferred to cover glasses attached to aluminum specimen stubs with silver paint and then sputter coated with 10 nm of gold- palladium alloy for scanning electron microscopy (SEM) examination using an Hitachi S2700-SEM microscope.

We followed the guidelines established in Stearn (1983) for writing diagnoses and descriptions for new taxa, as well as rules for botanical Latin.

RESULTS Spicaticribra gen. nov. Diagnosis: Differt a generibus ceteris in Thalassiosiraceis Lebour emend Hasle combinatione

ordinationis cribratae spicatae anastomosantis in pagina interna valvae et absentia fultoportularum in superficie valvae.

Descriptio: Frustulae cylidricae. Valvae planae, annulo fultoportularum marginalium prominentium et rimoportularum marginalium. Fultoportulae marginales prominentiis prominulis externis et extensionibus internis elongatis, unusquisque pork tribus. Fultoportulae centrales absentes. Rimoportulae differentiis externis deficientes. Striae rectae ordinatione radiali nonfasciculata.

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SPICATICRIBRA KINGSTONII, GEN. NOV. ET SP. NOV. 369

Areolae extra rotundatae, interne a cribris spicatis anastomosantibus velatae. Areolae centrales rotundatae ad irregulares, orificiis areolis ceteris 3-6plo magnioribus.

Generitypus: Spicaticribra kingstonii. Diagnosis: Differs from all other genera in the Thalassisosiraceae Lebour emend Hasle by the

combination of spicate, anastomosing cribral pattern on the interior valve surface, absence of central fultoportulae on the valve face and absence of external extensions of marginal strutted processes.

Description: Frustules cylindrical. Valves flat, with a ring of prominent marginal fultoportulae and marginal rimoportulae. Marginal fultoportulae with slightly raised external projections and elongated internal extensions, each with three satellite pores. Central fultoportulae absent. Rimoportulae lacking differentiated external expressions. Striae straight, with radial, nonfasciculate pattern. Areolae round externally, covered by long, spicate, anastomosing cribra internally. Central areolae round to irregular in shape, with external openings three to six times larger than other areolae.

Generitype: Spicaticribra kingstonii.

Spicaticribra kingstonii, sp. nov. Figs 1-24. Descriptio: Frustulae 9-25 pm diametro. Valvae primae hemisphaericae, absque portulis manifestis in

pagina externa vel portulis visibilibus in LM, licet portulis visibilibus in pagina interna, 22-25 pm diametro. Valvae vegetativae planae, limbo declivi margini. Fultoportulae marginales 7-27 in quoque valva, 2-3 pm distantes. Rimoportulae 1-3 in quoque valva, intra annulum fultoportularum. Striae radiales, rectae, aliquandro centro extensae, aliquandro prae centro terminantes, 1 6 1 9 in 10 pm. Areolae 18-21 in 10 pm intra strias, saepe cum areolis centralibus areolis ceteris 3 4 ~ 1 0 magnioribus.

Description: Frustules 9-25 pm in diameter. Initial valves hemispherical, without evident processes on the exterior surface or visible processes in LM (Figs 1 , 2, 17), but marginal fultoportulae and rimportula visible in internal view (Figs 21-24), 22-25 pm in diameter. Vegetative valve face flat, with mantle sloping to the margin (Figs 19, 20). Marginal fultoportulae 7-27 per valve, with 2-3 pm between adjacent fultoportulae (Figs 4, 7, 9, 1 I , 15). Rimoportulae number 1 to 3 per valve (Figs 4, 7, 9, 1 I , 15), with internal extensions at the same height as the fultoportulae (Figs 18, 2 1- 24). Striae radial, straight, some extending from the margin to the center, others extending only partially to center (Figs 3-16), 16-19 in 10 pm. Areolae 18-21 in10 pm within striae, with central areolae often 3-6 times the size of other areolae (Figs 3, 13, 19,20).

Holotype here designated CAS slide number 222041, with circled holotype shown in Figs 3 4 in this paper.

Type Locality: Great Smoky Mountains National Park, Lake Fontana, Swain County, North Carolina, USA.

Distribution: Known at present only from the type locality. Etymology: Spicaticribra refers to the spicate cribral pattern on the interior surface of the valve. The

species is named in honor of our friend and colleague John Kingston.

SEM Observations: Externally, the valve face is flat. Striae are straight and of varying lengths. Areolae are of

different sizes, with the central ones much larger than others. Along the sloping mantle, a reticulated array of areolae and ribs can be seen (Figs 19, 20). The external expressions of marginal fultoportulae are rounded pores slightly elevated from the valve (Fig. 20), present on the valve mantle. The central areolae, for the most part, have openings larger than the others. External expressions of the rimoportulae are not evident. A rim defines the edge of the valve mantle. This rim is scored by narrow vertical lines (Figs 19,20).

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370 J. JOHANSEN, P. KOCIOLEK & R. LOWE

Initial valves are hemispherical or broadly bell-shaped (Fig. 17). Areolae are present across the valve face and mantle, not organized into distinct striae or sectors. A ring of larger openings around the valve near the mantle are suggestive of marginal fultoportulae openings. They lack distinct elevated rims seen in the external openings of fultoportulae'of typical vegetative valves. Presence of fultoportulae and rimoportulae is evident in internal views (Fig. 21-24), although the processes are not visible in LM due to the highly arched valve face (Figs I , 2). Internal structure of the initial valves is similar to that of vegetative cells.

Figs 1-16. Spicaticribra kingstonii in LM. Figs 1, 2. Domed initial cell valves. Figs 3, 4. Holotype specimen. Figs 516 . Size reduction series. All figures to same scale, scale bar = 10 ym, arrows indicate position of rimoportulae.

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SPICATICMBRA KINGSTONII, GEN. NOV. E r SP. NOV. 371

Figs 17-20. Spicaticribra kingstonii in SEM. Fig. 17. Domed initial cell valve, external view. Fig. 18. Domed initial cell valve, note presence of processes. Figs 19, 20. External views of vegetative valves, arrows indicate position of raised external pores of the fultoportulae.

Figs 21-24. Spicaticribra kingstonii in SEM, internal views. Fig. 21. Valve with pore fields radiating from valve center. Fig. 22. Valve with pore fields radiating from off-center. Fig. 23. Valve showing radial rows of pores as well as structure of fultoportulae. Fig. 24. Tilted valve showing three pores evident on each fultoportula.

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372 J . JOHANSEN, P. KOCIOLEK & R. LOWE

Internally, prominent marginal fultoportulae are present (Figs 2 1-24). Each fultoportula is subtended by three satellite pores (Fig. 24). Labiate processes are stalked, with the terminus swollen (Figs 22, 24). Anastomosing criba cover the face and mantle areolae, separated by ribs that are thicker in the center and taper to the margins (Figs 21-24). The cribra are composed of small, rounded holes, most visible near the valve margin. Though an annulus is wanting, it appears the center of ornamentation is not necessarily lined up with the center of the round valve. Central fultoportulae are absent.

DISCUSSION

Spicaticribra most resembles the genus Thalassiosira in lacking many of the specialized structures seen in both well-established and newly erected genera of the order Thalassiosirales. For example, it lacks two different areas of ornamentation on the valve face, seen in Cyclotella and its close allies (e.g. Discostella Houk & Klee 2004, Puncticulata HHkansson 2002, Pliocaenicus Round & HIkansson 1992, Tertiarius HAkansson & Khursevich 1997, Khursevich & Kociolek 2002) and it lacks the chambers seen in Puncticulata (HIkansson 2002). Spicaticribra lacks distinct, well-ordered ribshnterstriae separating the fascicles of striae seen in Stephanodiscus and Cyclostephanos (e.g. Theriot & Stoermer 1984, Theriot & Kociolek 1986). Spicaticribra differs from almost all other Thalassiosira species, no matter what subgroup within Thalassiosira they might be allied, by having no central strutted processes (e.g. Stoermer & Julius 2003).

Cleve (1873), Hasle & Heimdal (1970) and Stoermer & Julius (2003) all define Thalassiosira as having central strutted processes. Such processes can be solitary, clustered in the center of the valve face (Fryxell & Hasle 1979a, 1979b), in a modified ring on the valve face (Fryxell & Hasle 1977), scattered over the valve face (e.g. T. lentiginosa, Fryxell 1977), or in clusters arranged in a ring on the valve face (e.g. T. australis, Fryxell 1977). A few species ascribed to Thalassiosira lack central fultoportulae. Hasle & Fryxell(l977) noted one species, T. leptopus that consistently lacks strutted processes on the face of the valve. They noted, however, that the marine species, T. leptopus, and the estuarine species, T. pseudonana, which may possess 0 or 1 central strutted process, are quite distinct from other members of the genus. They both have anastomosing internal ribs separating groups of cribra (similar to Spicaticribra) and have a well-defined annulus. T. guillardii Hasle (1978) and T. rudolfi (Bachman) Hasle (1 978) also can lack central processes in the smallest specimens, although they usually have 1-3 fultoportulae on the face of the valve. While S. kingstonii has small borders around the external openings of the marginal fultoportulae, and many Thalassiosira species have long extensions, other Thalassiosira species may have small borders (e.g. T. poro-irregulata Hasle & Heimdal), indistinct borders (T. lineata Jouse) or no rims or borders (T. subtilis [Ostenfeld] Gran emend Hasle) (Rivera 1981).

The most distinctive feature of Spicaticribra is the presence of spicate cribra that do not match up to the external openings of the areolae. Cribral patterns of T. pseudonana and T. guillardii are similar to the internal cribra of Spicaticribra, but these species are lightly silicified forms that do not have external areolar openings that are round or hexagonal. T. leptopus is the only taxon in the genus with continuous rows of cribra subtending well defined circular external openings. However, the pattern is very different, with more extensive coverage of poroids in T. leptopus than in Spicaticribra. Furthermore, all of these morphologically similar taxa have different striae patterns and external extensions on the fultoportulae.

Thalassiosira is beginning to appear as a residue of species, remaining after derived member of the Thalassiosirales have been removed (e.g. Kaczmarska et al. 2006). A number of studies have attempted to resolve phylogenetic relationships within freshwater members of

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SPICATlCRIBR.4 KINGSTONII, GEN. NOV. ET SP. NOV. 373

the Thalassiosirales. For example, Theriot & Kociolek (1986) examined relationships of some fossil species of Cyclostephanos relative to Stephanodiscus, and a similar appraoch was used to recognize Mesodictyon as a distinct genus (Theriot & Bradbury 1987). Theriot (1992) and Julius et al. (2006) examined relationships among species of Stephanodiscus, and Julius & Tanimura (200 1) examined relationships of the plicated species of Thalassiosira. With molecular data, future researchers may be able to resolve the evolutionary relationships among the Thalassiosirales and consequently revise the order to have more systematically informative classification. Many genera and species are being described, and Spicaticribra is certainly as distinct as many of these new taxa. It is defined by a unique combination of characters and at present we cannot with confidence determine which group of Thalassiosira species is evolutionarily closest. We prefer to describe this unusual species within its own genus rather than contribute to the taxonomic confusion surrounding Thalassiosira.

Of the 10 species of Thalassiosira previously reported from inland environments of the US . (Kociolek 2005), Spicaticribra kingstonii is differentiated by its total lack of central strutted processes, the enlarged central areolae, and an anastornosing cribral pattern that differs markedly from the pattern of external openings of the areolae. This is the second genus of freshwater Thalassiosiraceae described from a man-made habitat in the Southeastern United States. Discovery of Cyclotubicoalitus (Stoermer et al. 1990) from cooling ponds near a nuclear power plant was substantiated with the report of the taxon from Siberia (Genkal et al. 1998). It appears the recent freshwater diatom flora of the United States still has many undescribed taxa, even at the taxonomic level of genus (e.g. Spaulding et al. 2002)

ACKNOWLEDGEMENTS

This article is based on work supported by the National Science Foundation under grant number 0206360. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. We thank Discover Life in America for providing housing while we collected samples in Great Smoky Mountains National Park.

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Received for publication: December 2007

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