Limnadiidae Baird, 1849

Padhye, Sameer M. & Kulkarni, Mihir R., 2017, A new Indian record and morphological variation for Eulimnadia khoratensis Rogers et al., 2016 (Crustacea: Branchiopoda: Spinicaudata), Zootaxa 4268 (1), pp. 147-150 : 147-150

Limnadiidae Baird, 1849

Eulimnadia Packard 1874 .

Eulimnadia khoratensis Rogers, Dadseepai & Sanoamuang, 2016 Material examined. Four presumed hermaphrodites.

Locality. A small ditch (30 cm X 10 cm) located on the roadside of Belhe-Ahmednagar road, Ahmednagar district , Maharashtra, India. The depth was just 3–4 cm. Few Eulimnadia nauplii were observed. No other large branchiopod species were seen with the Eulimnadia .

Morphological observations. Some of the head, telson and cercopod characters showed distinct variation in size, shape and morphometry between the studied specimens (details in Table 1; Fig. 1 ). Characters such as nuchal organ, second antenna flagellomere number (exopod and endopod with seven each) were similar for all four specimens but the first antenna lobes varied from 5 to 7. Dorsal armature remained same and was typical for the genus. Number of paired thoracopods varied from 15–17.

Egg morphology: Diameter: 160–190µm; subspherical in shape, with 22–24 polygons. Polygons of variable size, each polygon with obtusely angled ridges and central narrow slit like grooves about 10–30µm in length, base of ridges thick, ridgelines smooth, ridge junctions with blunt protrusion on some polygons. Egg surface lined with pores of different sizes with largest being of about 1µm in diameter ( Fig. 2 A–E).

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 one having a diameter of about 1µm, large vesicles seem to be concentrated under the ridges ( Fig. 2 F).

TABLE I. Comparative account of the variation seen in đifferent morphological characters of the four ađult hermaphrođites reaređ via seđiment rehyđration along with the

original đescription of the species from Thailanđ (Characters for Thailanđ population taken from Rogers et al. 2016; actual specimens not seen; ‘-̓ đetails not given in the paper) Specimen N o I 2 3 4 E. khoratensis Thailanđ Head Ocular tubercle with an anterior Ocular tubercle with an Smooth Smooth Smooth

spine anterior tubercle Remarks. Neither the head nor the telson characters matched with the E. khoratensis description provided by Rogers et al. (2016) (Table 1) but the egg surface morphology was very similar.

Our results underscore the fact that adult Eulimnadia characters are generally too variable to be diagnostic (Table 1); such variation has been attributed to age, predator response, food quality and many other variables ( Rogers et al. 2012).

The Asian Eulimnadia need a major revision since most species were described using adult morphological characters without describing egg morphology ( Rogers et al. 2016). Of the seven Eulimnadia species currently known from India ( Rogers & Padhye, 2015), egg morphology of only two species is known, making egg identification of remainder species impossible. Durga Prasad and Simhachalam (2004) have provided a brief comparative account of all egg Indian species in which almost all species are reported to have round eggs. This observation combined with the discovery of this species from peninsular India suggests this species may be conspecific with E. michaeli , E. gunturensis or E. ovata (as discussed in Rogers et al. 2016).

Most of the Indian region remains unexplored for large branchiopods. Use of Sars’ Method in such cases would certainly help, as the method itself is simple, cost-effective and efficient, especially for diversity assessments (see Garcia-Roger et al. 2008). Furthermore, this method can be used for producing cultures for DNA sequencing work and obtaining clean eggs for diagnoses (Ex. Weeks et al. 2014).

Figures

FIGURE 1. Eulimnadia khoratensis (hermaphrodite). A – B, variation in head shape (scale bars: 0.2 mm) (arrows highlighting the variation in the spiniform projection)

FIGURE 2. Eulimnadia khoratensis (hermaphrodite). A, details of egg directly taken from the sediment showing debris attached to the polygons. B – C, detailed view of the eggs obtained from animals reared from sediment rehydration. D, egg surface. E, single polygon of the egg. F, internal structure of the egg shell (Scale bars A, E & F: 0.01 mm; B: 0.05 mm; D: 0.05 mm)