Fragilaria odeloucaensis E.Morales, Novais, C.E.Wetzel, Ector & Morais, 2022

Morales, Eduardo A., Novais, Maria Helena, Wetzel, Carlos E., Ector, Luc & Morais, Maria Manuela, 2022, Fragilaria odeloucaensis sp. nov. (Bacillariophyta, Fragilariaceae) a diatom from temporary streams in southern Portugal, Phytotaxa 555 (3), pp. 217-230 : 220-223

Fragilaria odeloucaensis E.Morales, Novais, C.E.Wetzel, Ector & Morais sp. nov. (LM: Figs 2–19 , SEM: Figs 20–31)

Description:—Frustules rectangular in girdle view, frequently heterovalvar with respect to striation ( Figs 17–19 ). Valves lanceolate with capitate apices ( Figs 2–16 ). Length: 17.9–28.3µm, width: 3.6–4.3 µm (n = 40). Axial area narrow and straight under LM ( Figs 2–16 ), zig-zagged under SEM ( Figs 20–25 ), delimited by elevated virgae that barely extend over sternum and by depressed striae ( Figs 20, 21, 24 ). Axial area depressed in outer view ( Figs 20–25 ), but raised in inner view ( Figs 27–29 ), though this latter feature is less noticeable in valves with sparser striation ( Fig. 26 ). Striae uniseriate, alternate and parallel in the middle of the valve ( Figs 20, 21, 24 ), becoming slightly curved and radiate toward the apices ( Figs 22, 23, 25 ). Stria density 11–16 in 10 µm. Each stria continues up to 1/2–2/3 of the valve mantle ( Figs 27–29, 30, 31 ). Striae clearly depressed in outer and inner views ( Figs 20–25 , 27–29 ), though less depressed in internal views of valves with sparser striation ( Fig. 26 ). Areolae round to elliptic ( Figs 20–29 ), 6–7 in 1 µm. Volae small, growing from the internal contour of the areola ( Figs 24 , 31 , black arrow heads). Spines absent. Virgae raised with respect to axial area and striae in outer view ( Figs 20–25 ), also raised in internal view ( Figs 27–29 ), although this feature is less prominent in inner view in valves with sparser striation. Central area with clear one-sided, square-shaped fascia infrequent, ghost striae faint, but clearer on valve face edges of the fascia (e.g. Figs 2, 5, 6, 8, 14 ). Blister-like depositions present along the abvalvar edge of mantle, irregular in shape and larger at the apices ( Figs 30, 31 , black wavy arrows). A single rimoportula present at one apex, oblique to apical axis of valve, with elliptic to squarish outer opening, aligned with a stria ( Figs 20–22 , white arrows), and parallel, raised, convex labia attenuated at the ends ( Figs 26–28 , white arrows). Apical pore fields well-developed, of the ocellulimbus type, composed of several rows of round pores entirely located on the apical valve mantle, externally framed by bulged borders (apical pore field is sunken) ( Figs 20–23, 25 , 31 ). Cingulum composed of several open elements ( Figs 23 , 30, 31 , black arrows), perforated by a single row of round pores ( Figs 22, 23 , white arrow heads). Plastids unknown.

Type:— PORTUGAL. Algarve region , Monchique Council : Odelouca Stream, epilithon, sampling point in the stream, 37º 21’ 19.87” N, 8º 26’ 27.80” W, Josué Figueira, 20th March 2017 (holotype BR-4723 = Fig. 2 ) .

Etymology:—The species epithet makes reference to the stream where the new taxon was found, the Odelouca (“ode” Arabic fem. for river, Portuguese “louca” and Arabic “lawqa” fem. for mad, insane).

Ecology and distribution:—The sampling site is located in a deep vee valley without natural terraces. The 500 m stretch was characterized by earth (crumbly) and bedrock in the banks, the channel substrate was mainly composed by cobble, gravel/pebble, the flow types were rippled, smooth and unbroken standing waves, there were some special features in the channel as exposed boulders, one unvegetated and two vegetated mid-channel bars, and the vegetation in the channel was composed by submerged broad-leaved plants, liverworts/moss/lichens, emergent reeds/sedges/ rushes/grasses/horsetails and filamentous algae. The land-use within 5 m of the banktops included broadleaf/mixed plantations and scrub & shrubs, and within 50 m of the banktop consisted of Eucalyptus plantation mixed with shrubs and herbaceous plants, the vegetation structure within 1 m of the banktops and in the bank faces was composed of two or three vegetation types, there was a semi-continuous extent of trees in the margins, the reach is also located 100 m downhill from a main road. The stretch was characterized by a banktop 1.5 m in height, a bank to bank width of 8 m, a 10 m wide bankfull channel, and a 7 m wide water cover in the channel.

The Odelouca Stream is a temporary river that dries out completely at the end of the summer and is classified within the Mountainous Rivers in the South, according to the Water Framework Directive typology. At the time of sampling, there was flowing water with a velocity of 0.46 m ∙ s-1 at the riffle where the scrubbed cobbles were collected. Depth of the transparent flowing water was 8 cm, water temperature was 14.1 ºC (at 12:00 AM), pH 7.2, electrical conductivity 161.1 μS∙ cm-1, and dissolved oxygen 90.1 % sat., 9.2 mg O ∙L- 1. At this site, the stream was classified as 2 Excellent (IPS = 17.8, EQR = 0.96 since the reference value for this typology is 18.5).

Thus far, the presence of the new species was confirmed at Odelouca Stream (in this manuscript) and in epilithon of St. Pedro Stream (St. Pedro de Muel locality in the Ribeiras do Oeste hydrographic basin in the Center Region of Portugal), where it was collected in June 10th 2007 (Novais 2011, reported as Fragilaria sp. 2 .). St. Pedro Stream is a permanent watercourse in a small watershed (ca. 38 km 2). The sampling site is located 13.1 km from the source, and at the sampling time the water temperature was 16.4 ºC, conductivity was 495.0 µS/cm, pH 7.5, dissolved oxygen 61.7 % sat, 6.13 mg ∙L- 1, alkalinity 73.0 mg CaCO 3 ∙L- 1, ammonium 0.003 mg N∙L- 1, chlorides 45 mg Cl- ∙L- 1, total organic carbon 20.8 mg C∙L- 1, phosphates 0.006 mg P∙L- 1, total phosphorus 0.025 mg P∙L- 1, nitrates 1.5 mg N∙L- 1, nitrites 0.015 mg N∙L- 1, sulphates 60.1 mg SO 4 ∙L- 1, total suspended solids 2.2 mg ∙L- 1, and a turbidity of 1.1 NTU.

Accompanying flora:—The new taxon reached a relative abundance of 5.2 % in the type slide. The most abundant accompanying species were Achnanthidium minutissimum (Kützing) Czarnecki (1994: 157 ; 36.4 % relative abundance), Fragilaria gracilis Østrup (1910: 190 ; 18.8 %), Gomphonema truncatum Ehrenberg (1832: 88 ; 6.8 %), Brachysira microcephala (Grunow) Compère (1986: 26 , 28; 5.9 %), Gomphonema tergestinum (Grunow) Fricke in A.W.F. Schmidt (1902: pl. 234: figs 39–43; 4.9 %) and several additional taxa with abundances <2 %.

Figures

FIGURES 2–19. LM images of F. odeloucaensis sp. nov. from the type (BR-4723) from Odelouca Stream southern Portugal. Figure 2 corresponds to the holotype, while figures 17–19 are girdle views of the new taxon. Scale bar = 10 µm.

FIGURES 20–25. SEM images of F. odeloucaensis sp. nov. from type material from Odelouca Stream southern Portugal. 20, 21. Valve views of two different valves showing striation pattern, axial area and position of rimoportulae (white arrows). 22, 23. Details of apices of valve in figure 21. Notice outer opening of rimoportula (white arrow in 22), single row of areolae on cingulum elements (white arrow heads in 22 and 23) and open copula (black arrow in 23). 24. Detail of valve center of figure 20. Notice zigzag pattern of axial area and delicate volae (black arrow heads). 25. Detail of apex showing apical pore fields completely located on valve mantle and surrounded by a bulged frame. Scale bars = 5 µm (Figs 20, 21), 2 µm (Figs 22–25).

FIGURES 26–31. SEM images of F. odeloucaensis sp. nov. from type material from Odelouca Stream southern Portugal. 26, 27. Internal views of two valves showing details of striation, narrow axial area and position of rimoportulae (white arrows). 28, 29. Internal view of apices of a single valve. Rimoportula is denoted by white arrow in 28. Notice raised costae and raised zigzag axial area, and depressed striae in 29. 30, 31. Collapsed frustule in side view (30) and detail of apex (31). Elements of cingulum are indicated by black arrows, blister-like depositions by wavy black arrows and volae in 31 by black arrow heads. Scale bars = 5 µm (Figs 26, 27, 30), 2 µm (Figs 28, 29), 3 µm (31).