Eulimnadia chaperi ( Simon, 1886 )

Padhye, Sameer M. & Rabet, Nicolas, 2017, Re-description of two spiny clam shrimps (Crustacea: Branchiopoda: Spinicaudata) of the Indian subcontinent from Daday de Dees's collection at MNHN with new insights on the validity of Eulimnadia compressa (Baird, 1860) and Eulimnadia chaperi (Simon, 1886), Zootaxa 4294 (3), pp. 349-360 : 355-357

Eulimnadia chaperi ( Simon, 1886)

Fig. 5 (A–C) Fig.6 (A, D, G)

Limnadia chaperi Simon, 1886 ; Rabet, 2010 (pg.)

Eulimnadia compressa Daday, 1927 ; Rogers & Padhye, 2015

Material examined. MNHN-IU-2007-595 (= MNHN-Bp 326): Four hermaphrodites studied (2 complete specimens; two with a few body parts missing)

Locality. Vajra Korau (Vajrakarur, Andhra Pradesh, India) (wrongly reported as ' Karnataka' in Rabet (2010)) Description. Hermaphrodite. Head broadly rectangular with marked anteroventral notch; ocular tubercle prominent; compound eye about 0.8 times the size of ocular tubercle; ocellus not visible; rostrum short, acute, rostral tip upturned; dorsal organ pedunculate, about thrice as long as broad at the base and as high as the ocular tubercle ( Fig. 5 A & B)

First antenna not clearly seen in the specimens

Second antenna peduncle cylindrical lined with long and fine setae; antennal exopod and endopod with 8 flagellomeres, each flagellomere elongated and rectangular in shape with 4–6 spines lined on the anterior side and with a row of plumose setae arranged on posterior side. ( Fig. 5 B)

Carapace transparent and oval, faint yellow in coloration; carapace surface smooth; dorsal margin smooth; maximum height at about one third distance from the anterior region of the carapace; ventral margin evenly convex and smooth, umbone absent ( Fig.5 A); carapace growth lines indistinct and at the margin.

Eighteen to twenty pairs of thoracopods, all similar in structure and reducing in size posteriorly ( Fig.5 A).

Abdomen. Dorsal armature as a group of 4–8 long setiferous setae of varying length; size and number of setae diminishes towards the posterior end.

Telson rectangular in shape; dorsal margin lined with 13–15 spines of similar length, spines of distal 2/3rd straight while the rest (near the mound) slightly re-curved, distalmost pair of spines at least three times longer than spines on dorsum and serrated on its dorsal margin; caudal filaments attached in between 3rd and 5th spines on a low convex mound; prominent spiniform projection present ventrally at the cercopod base and half its length ( Fig.5 C). Cercopods completely broken in one specimen, half broken in other and apex broken in other; about 9–10 setiferous setae on the basal half (till the small spine), setae as long as the distal most spine of telson, small spine present immediately posterior to these setae about as long as the width of the cercopod at the point of attachment, ( Fig. 5 C).

Eggs. Rabet (2010) examined the egg morphology of the same specimens in detail (See table 1) ( Fig. 6 A). Internal structure of egg shell consisting in a heterogeneous layer with large vesicle in the middle and smaller vesicle in the internal and in the external part. Larger vesicles are localized under the crest ( Fig. 6 D & G).

Size. Length: 5.8–6.1 mm; height: 3.4–3.6 mm.

Remarks. The Indian population from Vajrakarur was described as E. chaperi by Simon in 1886 and synonymized to E. compressa Baird by Daday (1927) using Simon's collection, but, without any comparison with the Baird's types. Under this name Daday identified one more population from Cambodia (see later E. magdalenensis ). Both populations have spherical eggs ornamented with polygons which could have been indiscernible during Daday's time. Eulimnadia chaperi egg is distinctly marked with very narrow furrows of various shapes at the base of every polygon while the polygon base in Cambodian population is smooth; the internal egg structure of both populations is also clearly different ( Table 1; Fig.6 A, D, G and B, E, H). Given the distinct differences in the egg morphology, we do not support the synonymy of E. chaperi types with E. compressa (Daday, 1927; Rogers & Padhye, 2015) and re-instate its species status. The diagnostic characters of egg surface of E. chaperi also closely match with the recently described Indian species, E. azisi Babu and Nandan, 2010 from Kerala, South India ( Babu & Nandan, 2010). The number of polygons and presence of very small and narrow furrows at the base of each polygon in these two species are very similar. Eulimnadia azisi could thus be a junior synonym of E. chaperi but this can only be confirmed by studying the types of the former species.

Figures

FIGURE 5. Eulimnadia chaperi (Simon, 1886). A, habitus. B, head with second sntenna. C, telson. Scale bars: A: 1 mm; B: 0.5 mm; C: 0.2 mm.

FIGURE 6. Comparison of Egg of Eulimnadia chaperi (Simon, 1886) and Eulimnadia magdalenensis Roessler, 1990. A, D & G, egg morphology and internal egg morphology of E. chaperi. B, E & H, E. magdalenensis from Angkor, Cambodia. C, F & I, E. magdalenensis from Cabo Branco, Brazil. Scale bars: A, B, C: 100 µm; D, E, F: 10 µm; G, H, I: 5 µm.