Leptestheria dumonti, Babu, K Subhash & Nandan, Bijoy, 2010

Babu, K Subhash & Nandan, Bijoy, 2010, Two new clam shrimp species (Crustacea: Branchiopoda: Spinicaudata) from Kerala, India, Zootaxa 2713, pp. 55-64 : 56-59

Leptestheria dumonti sp. nov.

(Figs. 1–3)

Etymology. The species is named in honour of Prof. Dr. H. J. Dumont, the former Director, Institute of Animal Ecology, University of Ghent, Belgium, for his contributions to limnology and taxonomy of freshwater zooplankton.

Type locality. An inundated paddy field at Parapukara, Kerala, 10° 23′ N, 76° 15′ E, part of Vembanad- Kol wetland ecosystem, a Ramsar site. Samples collected by K. K. Subhash Babu on 27 July 2007. 12 males and 6 females.

Holotype. Male fixed in 4% formalin (disarticulated: reg. no, MBM/Ch/22/09).

Paratypes, 2 females with eggs and 2 males fixed in 4% formalin were deposited in the Zoological Survey of India, Western Ghats station, Calicut, Kerala- State, India.

Allotype. Female fixed in 4% formalin (disarticulated; reg. no. MBM/Ch/23/09).

Diagnosis. Carapace oblong with straight dorsal hinge line. In adults, carapace pigmented on dorsal area and transparent in lower margin; growth lines are numerous usually 20–23 in mature adults. Each growth line fringed with small setae. Occipital notch is deep with long backwardly directed pointed occipital crest. Second antenna having 12–14 antennomers. Sixth endite of the male clasper curved and sickle shaped with a nail like protuberance at its tip. In male, palp of the third non clasping thoracopod is cylindrical and spinulated. Eggs are spherical without any ornamentation.

Description. Male. Length 6.02 mm; height 3.59 mm

Carapace bivalved, oblong with straight dorsal hinge line forming an obtuse angle at the junction with posterior margin (Fig. 1 B). Lower margin transparent; central and dorsal side pigmented. Umbone small but prominent and projecting beyond the hinge line. 21 growth lines, ornamented with faint reticulations. Ventral margin convex and fringed with small setae. Growth lines ornamented with small setae. Maximum width in the middle.

Rostrum spatulate bearing a terminal spine (Fig. 1D, 3F). Eye larger than ocellus and eye capsule protruded above the dorsal alignment of the head.

Occipital notch deep and crest prominent, sharp and directed posteriorly.

First antenna immovable with 8 lobes and extending to the second antenna seventh antennomere (Fig. 1F), each lobe with tufts of sensory setae.

FIGURE 1. Leptestheria dumonti sp. nov. (A–O) A. Carapace growth lines (female), B. Carapace (male), C. Head of female (lateral view), D. Head of male (lateral view), E. Second antenna (female), F. First antenna of male, G. First thoracopod with clasper (lateral view), H. Second thoracopod with clasper (lateral view), I. Terminal portion of the 5th endite (enlarged), J. Third thoracopod (male), K. 10th thoracopod with flabellum, L. First thoracopod (female), M. Telson (female), N, Telson (male), O. Eggs.

Second antenna biramous, with 12 antennomeres, each antennomere bearing spiniform projections and plumose setae on opposite sides.

Trunk slightly arched with 20 pairs of thoracopods. First two pairs of thoracopods similar in structure and modified into claspers (Fig.1G–H, 3F) but the second pair slightly larger than first. Clasper endite 4 broad with elongated palp. Endite 5 arcuate, apically acute (Fig. 1I, 3G). Endite 6 sickle shaped with a terminal protuberances (Fig.1G,I). Palp elongate, club shaped; distal portion fringed with fine setae. Third thoracopod endite 5 palp elongated, about twice the length of endite 6 (Fig.1J). Each body segment with dorsal slender, rigid, long setae.

Telson rectangular, with 18 spines on its dorsal margin (Fig.1N, 3C), unequal in shape and serrated (visible only under higher magnification) (Fig. 3D). Telsonic spines smaller anteriorly, becoming larger and sharper posteriorly (Fig. 3I). Telson terminal setae originating from the anterodorsal corner of the telson in lateral view. Cercopod robust, curved and armed with 24 non serrated spines on its concave margin (Fig. 3E).

Female. Length 6.57 mm; height 4.0 mm.

Carapace oblong with straight dorsal hinge line forming an obtuse angle at posterodorsal margin (Fig.1A). Lower ventral margin transparent; mid and dorsal areas pigmented. 20 growth lines. Umbone small, prominent and situated near to anterodorsal margin of carapace (Fig. 3A). Ventral margin convex and fringed with small setae. Growth lines fringed with small setae (visible under higher magnification). Surface ornamented with faint reticulations. Maximum width in the middle.

Rostrum pointed with a terminal spine (Fig.1C, 3H). Eye larger than ocellus; eye capsule protruded above the dorsal alignment of the head.

Occipital notch strongly produced, acute and directed posteriorly.

First antenna immovable with 9 lobes, each lobe fringed with tufts of sensillae. First antenna extending to second antenna third antennomere.

Second antenna biramous, each ramus having 14 antennomeres, each antennomere bearing spines on the side opposite that of the brush-like setae (Fig. 1E).

Thoracopods. Twenty four pairs, reducing in size posteriorly. First thoracopod foliaceous, fringed with plumose setae and bearing a palp on its 5th endite. (Fig 1L). 10th and 11th thoracopods with modified exopod to carry eggs; flabellum cylindrical (Fig. 1K).

Eggs spherical, without ornamentation (Fig. I O). Egg size 100 Μm, with clutch size of 300–350 Μm.

Body. Dorsal margin almost straight having large head and telson (Fig. 3B). Dorsal portion of the 12th body segment armed with a transverse ridge, fringed with strong setae. Dorsally, body segments bear stiff setae, longer on anterior segments and stouter on posterior segments.

Telson somewhat rectangular in lateral view, with 22 unequal serrated spines on the dorsal margins (Fig. 1M– 3I). Serrations more prominent on posterior spines (Fig. 3I). Cercopod robust, with 28 nonserrated spinules linearly arranged on its concave margin (Fig. 3J). Terminal telsonic setae originating from the anterodorsal corner of the telson in lateral view.

Ecology. Leptestheria dumonti sp. nov. was collected from an inundated paddy field just few weeks after the monsoon season. The water was turbid and brownish in colour which maybe due to the decaying vegetation. Copepods, Allodiaptomus mirabilipes Kiefer, 1936 (Calanoida) , Mesocyclops sp. ( Cyclopoida ) and large number of colonial rotifers were observed. Cladocerans including, Moina micrura Kurz, 1874 , Macrothrix triserialis (Brady, 1886) and Simocephalus serrulatus (Koch, 1841) co-occurred with L. dumonti sp. nov.

Remarks. So far, only two species of Leptestheria have been reported from India ( Leptestheria jaisalmerensis Tiwari, 1962 and Leptestheria longispinosa Nayar, 1965 ). Leptestheria dumonti sp. nov. somewhat similar to the L. jaisalmerensis , reported by Tiwari from Rajasthan in 1962. The number of the growth lines is almost same in both species but they differ in the shape of rostral spine, shape of the supraorbital margin, nature of the occipital crest and ornamentation of the carapace. In L longispinosa the dorsal margin of the head is almost straight and the occipital crest is reduced. In L. dumonti sp. nov. the rostral spine is ¼ the length of the rostrum and is directed to upward. In L. jaisalmerensis the carapace ornamentation is polygonal and unique, whereas in L. dumonti sp. nov. the carapace is ornamented with very faint reticulations, and also each growth line is fringed with unequal small setae. L. dumonti sp. nov. differs from L. longispinosa , by its higher number of growth lines on the carapace; supraorbital margin is not straight and the eye capsule protruded beyond the dorsal alignment of the head; structure and shape of the endite 6th of the male second thoracopod. Moreover, in L. longispinosa , dorsal margin of the telson is armed with 55–60 spines where as in L. dumonti sp. nov. the spines are few, numbering only 18–20. In both cases the telsonic spines are serrated. Cercopod has18–21 non serrated spines in L. dumonti sp. nov. whereas in L. longispinosa the cercopod armed with 20 serrated spines.

Based on the above comparative account of the features used for identifying the species of the family Leptestheriidae , the present species can be distinguished as a new species by the following characters: (1) smooth nature of the egg shell; (2) faint reticulations on the carapace (3) terminal protrusion on the 6th endite of first male thoracopod; (4) backwardly directed long, pointed occipital crest (occipital condyle); (5) deep occipital notch (6) eye capsule protruded above the dorsal alignment of the head, and (7) cylindrical and spiniform papillae on the 5th endite of the first thoracopod in female.