Streptocephalus dichotomus Baird, 1859

Padhye, Sameer, Timms, Brian & Ghate, Hemant V., 2016, Large branchiopod (Crustacea: Branchiopoda) egg morphology of Western Ghats, Maharashtra, India, Zootaxa 4079 (2), pp. 246-254 : 248-249

Streptocephalus dichotomus Baird, 1859

Ramshej site (20° 6' 29.16" N 73° 45' 50.3994" E). Size: 175–186 µm (n= 4); polygon number= 22 wh: dw ratio = ~1–1.5. Egg shell with either numerous irregular and complex depressions (polygons) or with regular, well defined polygons, each with 5–7 angles; angles either rounded or distinct. Polygon walls thick in cross section with margins rounded. Margins of polygon walls mostly straight but indented in few places. Polygon floors flat or slightly concave with small dimples; area of each polygon variable. Variation includes a few eggs with regular polygons having acute angles ( Fig. 2 A & 2B).

Visapur site (18° 44' 31.2" N 73° 28' 44.76" E). Size: 200µm and 189 µm (n=2); polygon number = 21 and 22; wh: dw ratio = 0.3. Eggs with irregular polygons, each polygon with 4–6 angles. Polygonal walls broadly triangular in cross section and with distinct upper edges. Floors of the polygons nearly flat ( Fig. 2 F).

Dighi site (18° 38' 9.2394" N 73° 52' 28.1994" E). Size: 177–190µm (n=4); polygon number = 23; wh: dw = 0.3– 0.4. Eggs with either regular or irregular polygons, that have 4–6 angles each. Walls thick, largely triangular in cross section or sometimes rounded. Polygonal floors uneven ( Fig. 2 G & 2H).

Sinhagad site (18° 25' 14.8794" N 73° 45' 44.6394" E). Size: 185µm, 178µm and 182µm (n=3); polygon number = 22, wh: dw = 0.4 – 0.6 Egg with narrow and irregular polygons each bearing 5–7 rounded angles. Walls thick with rounded margins, with a distinct upper edge. Polygonal floor weakly concave in most polygons with a weakly dimpled surface ( Fig. 2 D & 2E).

Masai site (16° 49' 7.6794" N 74° 5' 35.5194" E). Size: 180 and 187µm (n=2); polygon number = 22; wh: dw = 0.3–0.4. Eggs with regular as well as irregular polygons with 4–6 angles each. Polygon walls thick, rounded in cross section with straight margins for almost all polygons. Margins of few polygons slightly arched. Polygon floor flat, about third to half of total polygon area ( Fig. 2 C).

Figures

FIGURE 2. Eggs of Streptocephalus dichotomus (Baird, 1860) populations. A – B, Ramshej. C, Masai. D – E, Sinhagad. F, Visapur. G & H, Dighi. Scale bars: A, H = 100 µm; C – G = 50 µm).