Cyclotella iranica Nejadsattari, Kheiri, Spauld., & Edlund, 2013

Kheiri, Somayyeh, Nejadsattari, Taher, Asri, Younes, Hamdi, Seyed Mohammad Mehdi, Spaulding, Sarah & Edlund, Mark B., 2013, Cyclotella iranica sp. nov. (Bacillariophyta: Coscinodiscophyceae), a new diatom from the Karaj River, Iran, Phytotaxa 104 (1), pp. 35-42 : 37-41

Cyclotella iranica Nejadsattari, Kheiri, Spauld., & Edlund sp. nov. ( Figs 2–14 )

Frustules cylindrical, valves disc-shaped, valve face smooth, flat with alveolate multiseriate striae on margin; 5.5–15.8 µm in diameter. Striae vary in length, extending to mantle, 18–23 in 10 µm. Mantle fultoportulae located every 3-6 costae, central fultoportula(e) (1–3) mostly at proximal end of shorter striae. One rimoportula located on a costa, in larger valves within striae, in smaller valves near valve face-mantle junction.

Type:— IRAN. Albourz , Karaj , Karaj River , downstream of the Amir Kabir Dam, near the village of Aderan, elevation 1555 m, 35°53´N, 51°4´E, epipelon, collected 17 October 2011, M. M. Hamdi ( ANSP GC38094 , circled specimen, holotype! designated here (= Fig. 4 ), prepared from material ANSP GCM 22001; IAUGH slide 5892, ANSP GC38095 , prepared from material ANSP GCM 22002, isotypes! designated here) .

Valve face ornamented with two distinct parts: a hyaline central area and a marginal striated region; central area roughly 1/4–1/7 of total valve diameter. Striae alveolate and multiseriate, with 3–4 rows of fine porelli (not readily seen in LM); alveolar openings very short and small in relation to striae length ( Figs 13–14 ). Stria density 18–23 in 10 µm; valve diameter varies from 5.5–15.8 µm ( Figs 2–10 ). Striae differ in length, arranged in pseudo-sectored groups of branching striae around whole valve ( Figs 11–12 ). 1–3 central fultoportulae present, arranged randomly, mostly at proximal end of shorter striae ( Fig. 4 ) or rarely at central end of a longer stria ( Figs 10, 5, 9 ). Central fultoportulae have two satellite pores and no ornamentation on external opening of central tube. Marginal fultoportulae present on every third to sixth costae, near junction of valve face/ mantle ( Figs 13–14 ). Marginal fultoportulae have two satellite pores, open to valve exterior through unornamented central pore. One rimoportula situated on a costa between two adjacent foramina or, in larger valves, slightly advalvar to a foramen (within the striated valve part); rimoportula observed only under SEM, it is a sessile labium internally and variously oriented from radially to tangentially; external opening is a simple unornamented pore ( Figs 12–14 ).

Observations:— Among the many known species of Cyclotella , C. iranica is most similar to C. delicatula (see Scheffler et al. 2003, Houk et al. 2010). Like C. iranica , C. delicatula has an irregular central area with a similar valve diameter size range ( Table 1). However, the central area in C. delicatula is more or less transversally undulate and colliculate with pori or hollows. In contrast, C. iranica has a flat central area without colliculae, pori or hollows (when seen in SEM). Moreover, granules are concentrically arranged in rows on the costae of the valve view in C. delicatula , a feature that differentiates it from C. iranica (also in SEM). The most distinctive difference between C. delicatula and C. iranica is that C. delicatula possesses 1-2 fultoportulae near the valve center, opposite the rimoportula ( Houk et al. 2010, Scheffler et al. 2003, Kiss et al. 2012). In C. iranica , there is one, or in larger valves, up to three, central fultoportulae situated near the central end of a stria along the edge of the central area. Furthermore, the central area/valve diameter ratio in C. iranica is less than that of C. delicatula .

Cyclotella iranica shares a similar stria pattern, central area and approximately similar central area/ diameter ratio with C. fottii (as in Levkov et al. 2007 and Houk et al. 2010) but Cyclotella iranica differs in having a smaller, flat central area, stria density (in 10 µm), valve diameter range and the presence of a central fultoportula. C. iranica does not have marginal spines and its marginal fultoportulae are not visible in LM, both of which are characters of C. fottii ( Houk et al. 2010) .

Cyclotella iranica can be compared to some Miocene fossil species such as C. andancensis , C. andancensis var. bauzilensis and C. andancensis var. bipolaira ( Ehrlich 1966, Serieyssol 1981). All of these taxa share features with C. iranica , such as the unequal striated pattern of the valve, the presence of one rimoportula, and its orientation, and the nearly similar central area/diameter. However, they all differ from C. iranica by the absence of a central fultoportula and the colliculate ornamentation of central area. The alveolar openings in C. andancensis var. andancensis are the same size as those found in C. iranica , but are different in size when C. andancensis var. bauzilensis and C. andancensis var. bipolaira are compared with C. iranica .

Cyclotella krammeri ( Håkansson 1990) is also similar to C. iranica in having an unequal striation to the valve face, the presence of central fultoportulae and the size of alveolar openings. However, it has a larger central area than C. iranica , with pori and papillae, and more central fultoportulae, which are located in the center of the valve in contrast to C. iranica where the central fultoportulae are located at central end of striae.

Ecology and biogeography:— Habitat, Epipelic or epilithic. There is limited ecological and biogeographical information on Cyclotella iranica as it is described here for the first time. From a biogeographical standpoint, the distribution of Cyclotella iranica currently limited to the Karaj River basin in Iran, its type locality. No other illustrations of this taxon have been located in the literature. Further efforts are needed to determine if this taxon is indeed limited to just the Karaj Basin or if additional populations are to be found throughout the Middle East.

ND: No diatoms present, high amount of inorganic sediment

Rare: Abundance very low, with 1– 2 specimens from among c. 100 valves

-: Absent

*: Present at>2% relative abundance

Physicochemical factors taken in the field and laboratory ( Table 3) suggest that Cyclotella iranica is found in epipelic and epilithic collections from alkaline rivers, and that it is tolerant of nutrient and organic enrichment as evidenced from the low dissolved oxygen and high BOD and COD of the type locality ( Table 3). Among the sampling sites, C. iranica was found commonly only at Karaj River Sites 1 and 2 ( Table 2). There was no strong seasonality in the abundance of C. iranica as it was found at any time of the year; it was most prevalent during the summer and fall months.

Figures

FIGURES 2–10. Cyclotella iranica, ANSP GC38094, Fig. 4 is holotype specimen. All images are LM and in valve view. Scale bar: 5 µm.

FIGURES 11–14. SEM images of Cyclotella iranica, Karaj River, Iran. Figs 11–12, 14. Isotype material IAUGH. Fig. 13. Holotype material ANSP GCM22001. Fig. 11. External view showing central fultoportulae (black arrowheads) and the single rimoportula on the valve face (white arrowhead). Fig. 12. External view showing areolae within striae and the marginal fultoportulae (white arrowhead). Fig. 13. Internal view of the valve face. The single rimoportula on the valve face has an oblique orientation (white arrowhead. Numerous marginal fultoportulae are present). Fig. 14. Internal view of a small valve with a single central fultoportula and two satellite pores. Scale bars = 5 µm (Figs 11–13); 2 µm (Fig. 14).