Eulimnadia michaeli Nayar and Nair, 1968

Padhye, Sameer M., 2020, Taxonomical account of the Indian spiny clam shrimps (Crustacea: Branchiopoda Spinicaudata) from the Smithsonian National Museum of Natural History, USA., Zootaxa 4801 (2), pp. 374-382 : 377-380

Eulimnadia michaeli Nayar and Nair, 1968

( Fig.3C , 4 & 5 )

Locality. Small man made dug hole in ditch beside road, 41 miles west of Madurai Kamaraj University on the Madurai-Teni Road , Tamil Nadu, India (as per the data in USNM collection) (GIS data of Madurai Kamraj University: 9.941 N, 78.011 E)

Material examined. Four supposed hermaphrodites ( USNM 1097909, Date of collection: 18 th Oct 1980. Deposited as Eulimnadia sp.)

Description. Hermaphrodite. Head rectangular, ocular tubercle prominent, rostrum short, dorsal organ pedunculate, almost 2.5 times long as broad at the base ( Fig.3C )

First antenna: Two times the length of second antennal peduncle with 6–9 lobes, each lobe lined with aesthetascs.

Second antenna. Peduncle cylindrical, twice as long as broad, lined with long and fine setae; exopod with 7, and endopod with 8 flagellomeres, each flagellomere with 2–8 spines lined anteriorly and plumose setae arranged posteriorly (2–9 in number).

Carapace length 5.6 to 6 mm; height: 3.5 to 4 mm. Oval and transparent, faint yellow in coloration; carapace surface smooth, umbone absent ( Fig.4A ), 4–6 visible carapace lines.

Thoracopods. Fifteen to seventeen pairs of thoracopods (for thoracopod number please see Fig. 4A ); all thoracopods similar in structure and reducing in size posteriorly.

Abdomen. Dorsal margin of the last 6–8 posterior body segments with a group of 4–8 long setose setae of varying lengths, both size and number of setae reduces towards the posterior end; last 1–2 segments without any setae.

Telson rectangular; postero-lateral edge lined with 15–18 spines of unequal size; postero-lateral edge ending in a pointed spiniform projection and nearly 1/3 rd the length of the cercopod. Caudal filaments originating between the sixth and eight pair of spines of the telson ( Fig. 4B )

Cercopod long, about 1.2 times than the medial edge of telson ( Fig. 4B ), tapering distally. Many setose setae on the basal 2/3rd (reaching to the small spine), small spine present adjacent to the setae about 0.4 to 0.5 times the width of the cercopod at the point of attachment in length. Apical 1/3rd margin serrated ( Fig. 4C ).

Egg morphology. Diameter: 150–200μm. Spherical in shape with 26–32 polygons of variable size, each polygon with obtuse angle ridges and narrow slit like grooves about 10–25 μm in length. Thick base of ridges, ridgelines smooth, ridge intersections with blunt protrusions in most eggs ( Fig.5 A–C). Egg surface lined with pores of different size ( Fig.5D ).

Internal structure of the egg shell. Heterogeneously layered, larger vesicles concentrated in the internal and middle part while small vesicles present externally, largest vesicle with diameter of about 5µm while smallest having a diameter of about 1µm, large vesicles observed under the ridges ( Fig. 5E & F ).

Remarks. Eulimnadia michaeli was recently reported from Western Maharashtra as Eulimnadia khoratensis Rogers, Dadseepai and Sanoamuang, 2016 ( Padhye & Kulkarni, 2017). The latter species described from Thailand was in turn synonymized with Eulimnadia michaeli very recently (Rogers et al. in press) based on the egg morphology. A high intra population morphological diversity is known in this species ( Padhye & Kulkarni, 2017). Interpopulational differences between the Maharashtra population and the Smithsonian specimens from South India were evident in certain characters such as a) telson shape and spines and b) the vesicles seen in the inner layers of the eggs. The size of large vesicles was slightly smaller in the studied specimens and appeared to be ‘sandwiched’ between the small vesicles in the studied population. This species currently has a very wide distribution from India to Thailand.

Figures

FIGURE 3. Ozestheria indica. A, male head. B, female head. C, Eulimnadia michaeli hermaphrodite head. Scale bars: A & B—1 mm; C—0.5 mm.

FIGURE 4. Eulimnadia michaeli. A, habitus (hermaphrodite). B, telson. C, cercopod tip. Scale bars: A—1 mm; B—0.5 mm; C—0.2 mm.

FIGURE 5. Eulimnadia michaeli. A & B, egg (overall shape and minor variation). C, single polygon of the egg. D, egg porous surface. E & F, inner layers of the egg. Scale bars: A—0.1 mm; B—0.05 mm; C & E—0.02mm; D & F—0.005 mm.