Cyzicus annandalei sensu Rogers & Padhye, 2015

Padhye, Sameer M., Ingale, Prashant Arun & Vanjare, Avinash Isaac, 2020, Taxonomical account of the Indian Cyzicid Ozestheria annandalei (Daday, 1913) (Branchiopoda: Spinicaudata) from peninsular India, Zootaxa 4852 (2), pp. 246-250 : 247-250

Cyzicus annandalei sensu Rogers & Padhye, 2015 ( Figs. 1 , 2 )

Material examined: Three males from Pune; three males from Ahmednagar; two females from Pune; three females from Ahmednagar

Description. Male. Head: Ocular tubercle conspicuous, eyes circular and about 0.25–0.3 times the size of ocular tubercle, naupliar eye elongated with varying shapes, rostrum elongated with an acute rostral tip, occipital condyle noticeable, projecting, as long or slightly longer than its width at base ( Fig.2A & 2B ).

First antenna pedunculate with 10–19 irregular lobes; each lobe lined with aesthetascs.

Second antenna. Peduncle cylindrical, about twice as long as wide, lined with rows of plumose setae anteriorly. Antennal flagella exopod and endopod with 13–15 and 16–19 flagellomeres respectively. Each flagellomere cylindrical with 5–8 long anteriorly directed spines and 5–9 longitudinal rows of setae on posterior side.

Carapace oval, dorsal margin nearly straight with a distinct umbone; about 20 visible carapace growth lines; ventral margin evenly convex with dense setation. Pune—length: 5.6 ± 0.3 mm, height: 3.1 ± 0.4 mm; Ahmednagar—length: 5.8 ± 0.4 mm; height: 3.0 ± 0.4 mm.

Thoracopods. Twenty two pairs of thoracopods present ( Fig.1A )

First two thoracopods modified into claspers. Clasper movable finger (endopod) tapering posteriorly and hookshaped ( Fig.1C & 1E ); apex lined with 4 distinctly curved scales on the ventral side, longest located in the center, ~2.5 times as long as broad at the base ( Fig. 1F ); both claspers with a two-segmented large palp (endite V), on the first clasper both segments similar in length, on the second clasper distal palpomere (endite V outgrowth) about 1.05–1.1 times the proximal segment ( Fig.1C & 1E ); small palp (endite IV outgrowth) tubular-shaped in both claspers, about 2.5 times as long as broad; palm (endite IV) broadly rectangular, about 1.3 times longer than broad; gripping area of palm lined with conical and slightly recurved spines which increase in size posteriorly ( Fig.1C & 1E ).

Other thoracopods similar in structure (except for the two claspers) but decreasing in size posteriorly (thoracopod number observed in Fig.1A ).

Abdomen. Dorsal margin of the posteriormost 14–15 body segments lined with a dorsomedial posteriorly directed spine, increasing in size anteriorly; maximum length about 2.5 times as long as wide; bigger spines further lined with 4–10 posteriorly directed and curved spinules; longest spinule ~ 0.5 times the length of the main spine; last 2–3 segments without such spinules but with single or bifurcated stout apices.

Telson broadly rectangular; dorsal margin highly arched, lined with 12–30 bilaterally serrated and unequally sized pairs of spines; longest spines almost equal in length to the width of cercopod at base. Dorsal edge ending in a curved and blunt (pointed in Ahmednagar population) spiniform projection and nearly 0.5–0.7 times the length of the cercopod. Caudal filaments originating between the last and fourth pair of spines of the telson ( Fig. 2E ).

Cercopod long, about 1.7–1.8 times the dorsal margin of telson, narrowing distally; a few plumose setae (exact number indeterminable, 3–6 observed) present at about proximal half; lined with pecten from apex to about middle of cercopod; a single small spine present adjacent to the plumose setae, length about 0.6–0.8 times the thickness of the cercopod at point of attachment ( Fig. 2E ).

Description. Female. Marginally smaller than male; rostrum shorter; rostral tip distinctly upturned; occipital condyle similar to male ( Fig. 2C & 2D ); posteriorly directed projection on the abdominal segments same as in male ( Fig.1D ); telson marginal edge less arched as compared to male; telson marginal spines increasing in size posteriorly ( Fig.1D ); spiniform projection of telson with acute apex lined with small spinules; cercopod size, shape and rest of the characters similar to male.

Carapace size. Pune—length: 4.0 ± 0.8 mm; height: 2.4 ± 0.4 mm; Ahmednagar—length: 4.3 ± 0.5 mm; height: 2.5 ± 0.5 mm.

Representatives of Cyzicus have been shifted to the genus Ozestheria (a genus earlier known to be restricted to Australia and now known to occur in other parts of the world) based on the presence of characteristic scales on the endital tip of the male claspers ( Schwentner et al. 2020). This trait was observed in the males of both populations of O. annandalei . Some morphological features such as ocular tubercle, first and second antenna, carapace lines, telson spiniform projection with the dorsal marginal spine numbers varying between the two populations, which is commonly known in other spinicaudatans ( Rogers et al. 2017). However, a few features were consistent in both the populations viz, the elongated rostrum in males and distinct upturned rostral tip in females ( Fig.2 A–D and Fig.1B ) and unequal lengths of telson marginal spines in males. The female head did not match the original illustrations and description provided by Daday (1915), whereas the male head was similar except for the rostral tip which is much more acute in the original description. The consistent rostrum and telson characters separate this species from O. indica . Ozestheria annandalei is relatively rare in occurrence compared to some of the other spinicaudatan species in Western Maharashtra. It is currently known only from the two sampling sites from the Western Maharashtra.

Daday (1915) mentioned that this species is restricted to longitudes 74– 80° N and latitudes 25– 30° E, though, he cited ‘Tanjore’ (now Thanjavur, 10° 47’ 0” N, 79° 8’ 10” E) as a location. This city is in the South Indian state of Tamil Nadu nearly 1200 km from the sampled locations, therefore making this species widely distributed in India (other localities being in Uttar Pradesh, Rajasthan and Bihar) (sensu Daday, 1915; Rogers & Padhye, 2015).

Molecular phylogenetic studies have clearly shown the limitation of use of morphological traits like the occipital condyle in species separation in Spinicaudata ( Schwentner et al. 2015) . Yet, it is pertinent to designate species accurately using the existing knowledge to lower the taxonomical burden, which is still prevalent in the Indian spinicaudatan taxonomy ( Rogers & Padhye, 2015; Rogers et al. 2017).

Figures

FIGURE 1. Ozestheria annandalei (Daday, 1913). A, male habitus (Ahmednagar). B, female habitus (Ahmednagar). C, male clasper 1 (Pune). D, female telson along with dorsal armature (Pune). E, male clasper 2 (Pune). F, male clasper endopod tip with scales (Pune). Scale bars: 1 mm for A & B; 0.5 mm for D; 0.2 mm for C & E; 0.05 mm for F)

FIGURE 2. Ozestheria annandalei (Daday,1913). A, male head (Ahmednagar). B, male head (Pune). C, female head (Ahmednagar). D, female head (Pune). E, male telson (Pune). Scale bars: 0.5 mm for A to E.