Aulacoseira newjerseyana

Aulacoseira newjerseyana Enache, Potapova, Polaskey & Spaulding sp. nov. (Figs 1–27)

Description. Frustules cylindrical, with moderately thick silica walls, forming straight colonies. Outer and inner mantle walls straight and parallel with a slight curvature towards the collum and valve face. Valve face flat to slightly convex. Mantle height varies between 5.4–9.2 μm, and valve diameter 8.5–12.5 μm, based on measurements of 35 and 30 valves, respectively. Collum about a quarter of the mantle height (Figs 1–9). Mantle areolae sparse, oval to oval-elongated or with oval-irregular outline, aligned into incomplete rows (Figs 1, 3, 5, 6, 8, 9). A transverse row of smaller areolae with a density of 10–14 areolae in 10 μm present near the top of the collum, and a row of larger mantle areolae present near the valve face. Mantle areolae become more elongated near the valve face/mantle junction, sometimes with two areolae fused together (Figs 1, 3, 5, 6, 8, 9). Areolae oval or elongated and irregularly placed inside wall depressions that are straight or slightly undulate and parallel to the pervalvar axis. The areolae located between the mantle and collum form a transverse row with droplike, occasionally irregular or comma shape openings (Figs 16–18, 25, 26). The collum displays a ring of striations on its bottom half (Figs 18, 25, 26). The ringleist is solid, relatively shallow, and bell-shaped in cross-section (Figs 20, 21, 23, 24, 27). The mantle is covered externally by thin, porous, and finely reticulated copulae (Figs 16, 17, 26).

Internally, the mantle wall is straight and parallel to the outer wall, with areolae covered by a reticulated velum (Figs 20–24). There are multiple rimoportulae per valve with two to three openings observed on the half portion of valve perimeter (Figs 18, 20, 21, 25). The internal openings of the rimoportulae are positioned on a gently elevated portion of the wall, slightly above the row of areolae adjacent to collum (Figs 20, 21), while the external openings are positioned below the same row (Figs 18, 25, 26). A sinusoidal channel links the internal and external openings (Figs 20, 21, 27).

Valve face entirely covered with rounded areolae, 12–14 in 10 μm. A row of more prominent areolae marks the valve face/mantle interface (Figs 10–15). Short, anchor-like linking spines (1–2 μm) are present at the valve face/mantle junction originating between two areolae (Figs 10, 11). They display anchor-like branching with secondary branching sometimes visible, providing a strong interlocking system between sibling valves, occurring every second row of areolae (Figs 16–18, 25, 26). Separation spines not observed.

Holotype. Encircled specimen on slide ANSP GC 59350, Academy of Natural Sciences, Philadelphia. The holotype specimen is illustrated in Figs 1–2, core depth interval 31–33 cm, collected 19 June 2013, by B. Taylor and J. Franken, NJDEP.

Etymology. The specific epithet refers to New Jersey, the state where the new species was found.

Ecology and distribution. So far, A. newjerseyana has only been found in two lakes, both located in the New Jersey Highlands. Surprise Lake is an acidic, soft-water, low nutrient lake, with a maximum depth of 3.4 m, located within a forested, undisturbed watershed. The lake water pH was 4.8, conductivity 18 μS cm−1, total phosphorus (TP) concentration 21 μg/L and total nitrogen (TN) 0.49 mg/L at the time of sample collection in June 2013. Cedar Lake, at the time of core collection in October 2011, had pH 7.6, conductivity 271 μS cm−1, TP 10 μg/L, and TN 0.42 mg/L.

• Length Range
  8.5–12.5 µm
• Width
  5.4–9.2 µm