Eocyzicus hutchinsoni Bond, 1934

Padhye, Sameer M. & Lazo-Wasem, Eric A., 2018, An updated and detailed taxonomical account of the large Branchiopoda (Crustacea: Branchiopoda: Anostraca, Notostraca, Spinicaudata) from the Yale North India Expedition deposited in the Yale Peabody Natural History Museum, Zootaxa 4394 (2), pp. 207-218 : 212-213

Eocyzicus hutchinsoni Bond, 1934

( Fig. 4 & 5 )

Material examined. YPM IZ 003589.CR: One male (holotype) and one female (syntype). Eocyzicus deterrana Bond 1934 sensu Rogers & Padhye (2015) YPM IZ 003590.CR: 4 syntypes in 70% alcohol; YPM IZ 008752.CR: 15 additional specimens in 70% alcohol. Fig. (6)

Locality. Punjab: Tahsil of Kushab , Dam between Naushara and Mardwal, 12 III 32. (as per Bond (1934)). Original label data: P12 Muddy dam between Naushara and Mardwal, 12 March 1932 (Khushab, Punjab, Pakistan) .

Description. Male. Head: Grossly quadrangular, ocular tubercle conspicuous, eyes circular and nearly 0.3 times the size of ocular tubercle, naupliar eye not visible, rostrum spatulate with a blunt apex, occipital condyle slightly projecting nearly perpendicular to the body axis ( Fig.5A ).

First antenna. Pedunculate with 16 irregular lobes; each lobe bearing a patch of sub-terminal and terminal sensory setae.

Second antenna. Peduncle cylindrical about 0.5 times the head length, oblique rows of plumose setae present anteriorly. Antennal flagella exopod and endopod with 11 and 12 flagellomeres respectively. Each flagellomere cylindrical with 5–8 long anteriorly directed spines and 5–8 longitudinal row of setae on posterior side.

Carapace. Length: 10.68 mm; Height: 6.92 mm. Broadly ovate laterally, dorsal margin almost straight with prominent umbone, 13–14 visible carapace growth lines clearly seen, ventral margin evenly convex without any setation ( Fig.4B )

Thoracopods. Twenty two pairs of thoracopods present,

First two thoracopods modified into claspers in males. Clasper broad, movable finger (endopod) broad anteriorly but narrowing and hook shaped posteriorly ( Fig. 4C ); large palp (endite V), two segmented in both claspers, length of both segments nearly equal in first clasper; distal palpomere (endite V outgrowth) slightly elongated than proximal segment, in second clasper, small palp (endite IV outgrowth) cylindrical in both claspers, nearly 3 times as long as broad, directed almost perpendicular to the body axis, palm (endite IV) broadly rectangular, about 1.2 times as longer than broad, medial protrusion at base of palm broadly convex on both claspers and more acute in first ( Fig.4 D & E ), gripping area of the palm lined with small spines increasing in size posteriorly, spines roughly conical with acute apex ( Fig.6E ).

Other thoracopods similar in structure but reducing in size posteriorly.

Abdomen. Dorsal margin of the posterior body segments (last 11–12) with a dorsomedial projection lined with 4–5 long posteriorly directed and curved spines, last 4 segments with single or bifurcated stout apices ( Fig. 4G )

Telson broadly rectangular, postero-lateral edge armed with 12–15 conical and bilaterally serrated pairs of spines of unequal sizes (serrations seen only on some spines); longest spines nearly equal to the width of cercopod base in length. Postero-lateral edge ending in an arched and acute spiniform projection and nearly 0.7 times the length of the cercopod. Caudal filaments originating between the third and fourth pair of spines of the telson ( Fig.4F ).

Cercopod slightly longer (about 1.1 times) than the postero-medial edge of telson, tapering distally, a few (exact number indeterminable, 6–7 seen) plumose setae present till about proximal 1/3rd, anterior 1/3rd of the cercopod lined with pecten distally, a single small spine present adjacent to the plumose setae, length about 0.25 times the thickness of the cercopod at point of attachment, apex gently arched.

Female. Carapace length: 8.84 mm; carapace height: 5.56 mm. Slightly smaller than male. Rostral tip of female with a pointed apex. Ocular tubercle distinct. Occipital crest similar to male ( Fig.4A ). About 22 pairs of trunk limbs present. Dorsal armature like in male. Number of spines on the postero-lateral edge of telson more than in male (22–23) while size of the spines smaller; 2 spines in the middle nearly twice the size of the other spines. Cercopod length almost equal to the postero medial edge of telson male ( Fig.5B ).

Comments. Bond stated that this species closely resembled E. orientalis and E. bouvieri in the overall morphology, although the female rostral tip of this species is acute unlike that in E. orientalis . The two larger medial spines on the telsonic margin, size of the longest spine of the telsonic margin and shape of the male head of E. orientalis (Daday, 1930) are similar to what is seen in E. hutchinsoni . E. hutchinsoni is distinct from E. bouvieri with respect to a conspicuous occipital condyle seen in the former species. We cannot synonymize E. hutchinsoni with E. orientalis in this study as we have not studied the type specimens of the latter species.

Rogers & Padhye (2015) synonymized E. deterrana ( Fig. 6 A–D ) with E. hutchinsoni . The major difference observed between E. deterrana and E. hutchinsoni was the difference in the shape of the rostrum of the male with the former having a triangular shape ( Fig.6A ) and the latter having a broad spatulate one. Very recently, the shape of the rostrum has also been shown to vary in an Eocyzicus species depending on the stage of development along with other known variable characters ( Rogers et al., 2017). Given the smaller size of the specimens, they could very well be sexually immature forms of E. hutchinsoni with differences in other morphological traits being variations within the same species. Rogers et al. (2017) have further suggested to take a very conservative approach in Eocyzicus taxonomy due to the plasticity of distinct taxonomic characters. Given this information, we maintain the synonymy of this species with E. hutchinsoni as proposed in Rogers & Padhye (2015) and Rogers et al. (2017) until additional information is obtained.

Figures

FIGURE 4. Eocyzicus hutchinsoni. A, head (female). B, carapace (male). C, claspers.D & E, first clasper.F, telson (male). G, dorsal armature. (Scale bars: A & B: 1mm; C–E:0.2 mm; F: 1 mm; G: 0.2 mm).

FIGURE 5. Eocyzicus hutchinsoni. A, head (male). B,telson (female). (Scale bars: A: 1 mm; B: 0.5 mm).

FIGURE 6. Eocyzicus hutchinsoni (described as Eocyzicus deterrana sensu Bond (1934)). A. head (male). B. head (female). C, second clasper. D, telson (male).(Scale bars:A & B: 1 mm; C: 0.2mm; D: 0.5 mm).