Orthoseira johansenii R.L.Lowe & Kociolek, 2013

Lowe, Rex L., Kociolek, J. Patrick & Vijver, Bart Van De, 2013, Two new Orthoseira species (Bacillariophyceae) from lava tubes on Île Amsterdam and Big Island (Hawai ΄ i), Phytotaxa 111 (1), pp. 39-52 : 46-48

Orthoseira johansenii R.L.Lowe & Kociolek sp. nov. ( Figs 34–52 )

Frustules cylindrical in girdle view, usually occurring singly or in short chains of 2–4 cells. Valves disc-shaped, 24–65 µm in diameter, mantle 11–13 µm deep. Valve surface flat, forming a nearly right angle with the mantle. Mantle striae uniseriate, 18–21/ 10 µm. Areolae on the valve face small, round, irregularly-scattered and rarely forming straight continuous striae restricted to the outer 2/3 of the valve face with the remaining surface forming an hyaline area pitted and containing carinoportulae. Carinoportulae relatively large, numbering 1–3. Marginal spines are usually straight but can but forked. Spines number 2–4/ 10 µm. No caverns or internal undulations present. Internal valves wanting. Copulae open, numbering 5–7/cell.

Type: — Pua Po’o lave tube, Volcanoes National Park, Hawai’i, slide no. BISH-755092 (Holotype, Bishop Museum of Natural History, Honolulu ), ANSP-20040 ( Isotype Academy of Natural Sciences , JPK-COLO 4195 ( Isotype Kociolek Collection , University of Colorado, Boulder ).

Etymology:— the specific epithet johansenii refers to our friend and colleague Dr. Jeffrey Johansen, John Carroll University (Cleveland, USA).

Observations:— In the SEM, the valve face is flat ( Fig. 42 ) to weakly domed/concave ( Fig. 43 ). Hyaline central area smooth ( Figs 42, 43 ) and may be reduced due to irregularly-placed areolae ( Fig. 42 ). Areolae in defined striae near the margin becoming irregularly spaced towards the valve centre ( Figs 42, 45 ), small and poroid, sometimes surrounded by a slightly raised rim ( Figs 44, 45 ). No difference in areolae structure or size between valve face and mantle ( Fig. 42 ). Areolae on the mantle always arranged in parallel striae ( Figs 45, 46 ). External marginal pore fields between spines absent ( Fig. 45 ). Carinoportulae distinct in the central area, often surrounded by raised rosettes or fine ridges ( Fig. 44 ), each with a pronounced (sometimes even conical) silica collar ( Fig. 44 ). Valve face/mantle junction abrupt with rounded edge ( Fig. 45 ). Ring of large linking spines may be present ( Figs 45, 46 ), but in this species more frequently encountered are stout siliceous thickenings ( Figs 45, 46 ). Linked spines plate-like, bifurcated or with a quite complex shape ( Figs 45, 46 ). On the mantle small, irregular thickenings visible between the areolae ( Fig. 45 ). Internally, valve face flat, smooth ( Figs 48, 49 ). Areolae appearing as small rounded poroids ( Fig. 48 ), with a velum ( Figs 50, 51 ). Carinoportulae unoccluded, with small, simple and rounded internal openings ( Figs48, 49, 52 ). No other processes are present on the valve interior. Copulae open, with very small poroids scattered or organized into one straight row and others scattered, parallel to the pervalvar axis ( Figs 47 ). Sometimes copulae ornamentation is but a few poroids ( Fig. 47 ).

Ecology:— The internal surface of this lava tube was damp, with soil, bryophytes and exposed lava representing the primary microhabitats. Present along with O. johansenii were Nupela sp. , Melosira sp. Kobayasiella sp. Diadesmis biceps G.A.Arnott ex Grunow in Van Heurck 1880: 14 /31b, Nitzschia hantzschiana Rabenh. (1860: 40) and Pinnularia divergentissima (Grunow in Van Heurck 1880: 6 /32) Cleve 1895: 77. Of these diatoms, O. johansenii was the least abundant taxon.

Figures

FIGURES 34–41. Orthoseira johansenii R.L.Lowe & Kociolek sp. nov. Light Microscopical views. Figs 34–39 Valve views showing the variability in the extent of the hyaline central area and the number of carinoportulae. Figs 40–41. Girdle views with focus on the bifurcating spines and the girdle bands. Scale bar represents 10 µm.

FIGURES 42–47. Orthoseira johansenii R.L.Lowe & Kociolek sp. nov. Scanning Electron Micrographs. Fig. 42. External view of an entire valve showing two carinoportulae, the small hyaline central area and the rows of areolae and the (eroded) regularly placed linking spines. Fig. 43. External view of an entire valve showing two carinoportulae, a more irregular pattern of areolae, a larger hyaline central area and regularly placed linking spines. Fig. 44. Detail of the carinoportulae with a raised rim. Note also the raised areolae. Fig. 45. Detail of the valve face/mantle junction with big spines and silica outgrowths on the mantle. Fig. 46. Detail of two valves linked by bifurcating linking spines and one open girdle band with small perforations. Fig. 47. Detail of the perforated, open girdle bands. Scale bar represents 10 µm in Figs 42, 43, 46 & 47 and 1 µm in figs 44 & 45.

FIGURES 48–52. Orthoseira johansenii R.L.Lowe & Kociolek sp. nov. Scanning Electron Micrographs. Fig. 48. Internal view of an entire valve showing three carinoportulae. Fig. 49. Internal view of a valve linked to a second valve. Note the rather shallow mantle and hyaline area around the two carinportulae. Fig. 50. Detail of a broken valve edge showing the structure of the areolar canal closed by a velum. Fig. 51. Detail of a few areola in cross-section. Fig. 52. Detail of the carinoportulae. Note the absence of small slits between the carinoportulae. Scale bar represents 10 µm in Figs 48 & 49, 2 µm in Figs 50 & 52 and 1 µm in Fig. 51.