Ulnaria acuscypriacus Lange-Bertalot et Cantonati, 2018

Cantonati, Marco, Lange-Bertalot, Horst, Kelly, Martyn G. & Angeli, Nicola, 2018, Taxonomic and ecological characterization of two Ulnaria species (Bacillariophyta) from streams in Cyprus, Phytotaxa 346 (1), pp. 78-92 : 83-88

Ulnaria acuscypriacus Lange-Bertalot et Cantonati sp. nov. ( Figs 37–56 )

Light microscopy ( Figs 37–46 ): —Frustules rectangular in girdle view. Cells sometimes connected by the valve face to form short chains. Valves linear-lanceolate with almost parallel margins for about half of the length, then tapering gradually towards a protracted, slightly subcapitate end. Length 140–300 μm, breadth 6–6.8 μm at the centre, 2.6–2.8 μm at the ends. Length-to-breadth ratio ca. 23–45. Axial area moderately narrow, becoming broader towards the centre. Central area distinct, roughly rectangular, square, typically with some short marginal striae on one side. Striae 8.5– 10 in 10 μm, slightly denser towards the ends, generally opposite and perpendicular to the apical axis. Areolae not discernible (see SEM view). One rimoportula at each end just below the pole.

Scanning electron microscopy ( Figs 47, 49–54 external views, Figs 48, 55–56 internal views): —Striae regularly biseriate, often with a zig-zag appearance with the exception of one or a few reduced ones adjacent to the central area ( Fig. 54 ) and near the ends ( Figs 49–52 ). The virgae in combination with the troughs of the striae have a moderately high profile, just apparent over the central area too ( Fig. 54 ). The junctions between valve face and mantle are hyaline, free from regular perforations and any spines ( Figs. 52–53 ). The biseriate striae continue onto the mantle ( Fig. 52–53 ). The density of areolae in one of the two series of a stria is 35 in 10 μm or ca. 63 if all areolae are counted in 10 μm respectively. Rimoportula foramen lying in a funnel–like depression ( Figs. 49–53 ). Ocellolimbus large, covering almost the entire pole, with ca. 11–14 transapical and 16–17 pervalvar series of porelli ( Figs. 52–53 ). The advalvar margin of the ocellolimbus is consistently weakly crenulated ( Fig. 52 ). Horns are absent, in contrast to several similar Ulnaria species. Internally, the pattern of fine structures is similar to that found in many Ulnaria species. SEM girdle elements see Figs. 52–53 . At least two closed copulae per valve, each with a single row of poroids on the advalvar side

Etymology: —The specific epithet refers to the fact that the species resembles U. acus and was found in Cyprus. With this epithet we also acknowledge that the new species could be discovered thanks to an in-depth study of materials collected as part of a comprehensive study of the streams of Cyprus.

Holotype:—cLIM004 DIAT 2136 ( Sampling site WDD11, stones, Diatom collection of the Museo delle Scienze - MUSE, Trento, Italy). Collected by David Armanini on the 18 th of February 2010 . Holotype designated here: Figs 37–41 .

Isotypes: — Diatom Collection of the Academy of Natural Sciences of Drexel University, Philadelphia, PA, USA: ANSP GC14461 (slide), ANSP GCM15147 (cleaned material), ANSP GCM15148 (raw material) ; - Botanical Museum of the University of Berlin, Germany: B 40 0041532 (slide), B 40 0041533 (cleaned material), B 40 0041534 (raw material) .

Type locality: —Stream sampling site WDD11 (River Garyllis, site u/s Polemidia Dam, Monitoring Code r9- 4-3-80). Coordinates: GPS EAST _UTM_Zone36, North_WGS84: 497670, NORTH _UTM_Zone36North_WGS84: 3844820. Catchment Area (Km 2): 66.8. Source distance (Km): 15.2.

Distribution: —Not yet known because the species has previously not been distinguished from other Ulnaria taxa. There are many potential observations of the new species beyond Cyprus; however, these still need to be confirmed.

Moderately frequent (13 sites) in Cypriot streams (much less frequent than U. monodii comb. nov.) but usually not abundant. Observed qualitatively (i.e., relative abundance <0.2%) on 2 slides and counted on 11 (relative abundances: 0.2–11%).

Ecology & co-occurring diatom species:—Environmental conditions at the type locality (seasonal averages): Discharge (m 3 s-1): 0.22, Temperature (°C): 12.45, conductivity (μS cm-1): 1506, pH: 8.1, dissolved-oxygen saturation (%): 79, nitrate nitrogen (mg L- 1): 7.4, TP (μg L- 1): 236, SRP (μg L- 1): 5.

Species most common (> 20%) on slides where U. acuscypriacus was recorded: Achnanthidium cf. jackii narrow, Achnanthidium minutissimum (Kützing 1833: 578) Czarnecki (1994: 157) , Cocconeis euglypta , Diatoma moniliformis , Gomphonema pumilum var. rigidum , Ulnaria monodii comb. nov., and Ulnaria vitrea .

Ecological preferences of the two Ulnaria species treated herein ( Figs 57–60 )

A total of 12 different Ulnaria forms were found in the 174 samples investigated from Cyprus, of which four could be confidently assigned binomials (the two species considered here along with U. vitrea and U. ungeriana ) whilst a further form corresponded to U. acus sensu lato. 21% of samples had no Ulnaria species present whilst a further 44% had a single Ulnaria species but, interestingly, the remaining 36% contained two or more (up to a maximum of five) distinct Ulnaria forms, suggesting considerable overlap in their niches. Ulnaria monodii comb. nov. was found with U. acuscypriacus sp. nov. in 10 samples (four where both formed> 1% of the total count), with U. vitrea in 11 samples (five where both formed> 1%). Similarly, U. acuscypriacus sp. nov. is found in one sample with U. vitrea (both present at>1%).

Ulnaria monodii comb. nov. could, on occasion, dominate the assemblage in a sample, constituting over half of all diatoms in a few cases. Ulnaria acuscypriacus sp. nov., by contrast, rarely formed more than ten percent of the total. Both had a clear preference for circumneutral water ( Fig. 56 ). U. monodii was most abundant when conductivity was <1000 μS cm-1 whilst the conductivity range within which U. acuscypriacus sp. nov. lived was large, with several readings> 1000 μS cm-1 and a maximum of 2843 μS cm-1 ( Fig. 57 ), suggesting that this species may be more tolerant of brackish conditions than U. monodii comb. nov. The latter was generally associated with low concentrations (weighted averages in Table 1) of total nitrogen ( Fig. 58 ) and total phosphorus ( Fig. 59 ), although exceptions did occur. One of us (MC) has also seen U. monodii comb. nov. in samples from a very slightly enriched stream in Puerto Rico, that was studied in detail and compared with a more near-natural stream where U. monodii was replaced by Ulnaria lanceolata ( Kützing 1844: 66) Compère (2001: 100) . By contrast, probably due to the low number of occurrences, U. acuscypriacus showed no clear preference for nutrients. In this dataset, TN was correlated with ammonium-N, nitrite-N and nitrate-N, whilst TP was also correlated with soluble reactive P. TN was also correlated with conductivity (Pearson rank correlation, r = 0.435).

Figures

FIGURES 37–46. LM views of Ulnaria acuscypriacus sp. nov. Figs. 37–41. Whole valves. Scale bar, 10 μm. Figs. 42–46. Variability of the apices in the populations sampled in Cyprus. Scale bars, 10 μm. Note the central area, and the apical rimoportula.

FIGURES 47–56. SEM outside (Figs. 47, 49–54) and inside views (Figs. 48, 55–56) of Ulnaria acuscypriacus sp. nov. Figs. 47–48. Complete thecas: note the central area. Figs. 49–51. Details of the endings: Note the rimoportula and the biseriate striae. Figs. 52–53. Details of the apices of frustules in oblique position: Note the apical pore fields (number and arrangement of porelli) and the copulae with a single row of poroids at the advalvar side. Fig. 54. Central part of the valve: Note the central area, some ghost striae, and the striae closest to the central area becoming biseriate towards the valve margin. Fig. 55. Central part of the valve. Fig. 56. Apex: Rimoportula and ocellolimbus. Scale bars: Fig. 47 = 50 μm; Fig. 48 = 40 μm; Figs. 49, 52, 54–56 = 3 μm; Figs. 50–51 = 2 μm; Fig. 53 = 4 μm.

FIGURES 57–60. Scatter plots of four parameters defining the ecological niches of the two Ulnaria species studied, and allowing a comparison between the two. Fig. 57. pH. Fig. 58. Conductivity (EC). Fig. 59. Total nitrogen (TN). Fig. 60. Total phosphorus (TP).