Leptestheriella simhadrii, Simhachalam, Gullipalli & Timms, Brian V, 2012

Simhachalam, Gullipalli & Timms, Brian V, 2012, Two new species of Spinicaudata (Crustacea: Branchiopoda) in south India with a key to Leptestheriella and Eocyzicus, Zootaxa 3161, pp. 20-36 : 21-28

Leptestheriella simhadrii sp. nov.

( Figs 1–2 )

Etymology. This species is named after Prof. Y.C. Simhadri, former Vice-Chancellor of Acharya Nagarjuna University who is well known for his able administration.

Type locality. INDIA: Racharla Mandal, Prakasam District. Pool at Racharla (15° 28' N, 78° 58' E) approximately 22 km north of Giddaluru. (altitude 224 m asl). Date of collection: 6 August 2002 by G. Simhachalam.

Type material. Holotype. Male length 5.5 mm; height 2.3 mm; accession number NHM 2005.282.

Allotype. Female length 6 mm, height 3 mm; accession number NHM 2005.283.

Paratypes. Male length 5.5 mm, height 2.5 mm and females length 5.5 mm, height 2.5 mm. INDIA: Prakasam District: pools at: 1) Anumalapalli of Racharla Mandal, (altitude 224 m asl, 15° 31'N, 78° 53'E), approximately 25 km north of Giddaluru and 2) Kaluvapalli of Racharla Mandal (altitude 224 m asl, 15° 26 'N,78° 58.'E), approximately 19 km north of Giddaluru, collected 15 October 2003. Accession number NHM 2005.283–285. Remainder of the material is deposited in Museum, Department of Zoology, Acharya Nagarjuna University.

Description. Male. Carapace ( Fig. 1 A) oblong, thin, light yellow to brown, semipellucid, much compressed, umbone not prominent. Growth lines 8 ( Fig. 1 B), thick, rib-like ( Fig. 1 C), and arranged in regular order. All growth lines and free margins of carapace with blunt, peg like, subcylindrical spinules ( Fig. 1 D). Interstices between growth lines rugose. Carapace rounded anteriorly and posteriorly; hinge line ( Fig. 1 B) straight and forming angles in 30° posterior and 20° anterior regions to hinge line. Free ventral margin straight and slightly convex.

Head ( Fig. 1 E) moderately large, about 33.3% of trunk length; eyes small, about 40% of ocellus, ocular protuberance large, double the size of eye, ocellus (oc) large and triangular in lateral view. Fornix (fo) prominent arising from dorsal angle of rostrum; small spine present at fornix apex, about 34% of fornix length, fornix 2.9 times as long as spine. Rostrum (ro) spatulate, occipital region elongated, acute, forming 50° angle to body axis, occipital furrow as deep as length of rostral spine. Mandible crescent shaped.

First antenna ( Fig. 1 E) 1.7 times longer than in females and reaching second antenna sixth flagellomere. 17 sensory lobes on left ramus, 18 on right ramus; each with several sensory aesthetascs.

Second antenna ( Fig. 1 E) peduncle broad, twice as long as broad, with indistinct annulae and heavily fringed with short spines anteriorly. Second antenna biramal; flagellae unequal in size; anterior flagellum of 11 flagellomeres and posterior flagellum of 10 flagellomeres, anterior flagellum 1.1 times as long as posterior flagellum. Each flagellomere armed with 1–5 serrated spines anteriorly (apparently dorsal) and 2–4 thin plumose setae posteriorly (apparently ventral).

Trunk with 24 pairs of thoracopods. Exopod margin of thoracopods ( Fig. 2 A) with digitiform lobes with setae characteristic of the genus ( Hu, 1988).

Thoracopod I and II modified as claspers distally ( Figs 1 F,1G) and composed of a hand bearing an apical club, large and small palp and a moveable finger (terminology following Olesen et al. 1996). Hand (clasper endopod) broad, width 0.8 times length and with a hooked protrusion medially located at about two thirds of its length. Apical projection (endite 4) broad, length 0.7 times width, a digitiform extension of the hand and crowned with numerous scales and bearing the small palp of subequal length as diameter of apical projection. Moveable finger (mf) (endite 5) arcuate, apically acute and bearing setae apically, length subequal to large palp (endite 6). This palp (lp) two segmented, proximal segment 2.7 times as long as distal segment; distal segment widened toward apex, with numerous setae distally, composed of fourth, fifth and sixth endites. Thoracopod II ( Fig. 1 G) with apical projection a little larger than in thoracopod I. Medial projection not as large as in thoracopod I and unhooked. Moveable finger as in thoracopod I. Large palp 1.2 times as long as moveable finger, two segmented with proximal segment 1.2 times as long as distal segment. Moveable finger and large palp with setae distally.

Thoracopod III ( Fig. 2 A) fifth endital palp (as interpreted by McLaughlin, 1980) 2-segmented, proximal segment 1.1 times as long as distal segment; both segments combined 1.5 times as long as sixth endite, numerous setae distally. Margin of exopods (“flabellum”) of thoracopods with numerous unbranched digitiform exites. A triangular lamina (“epipodital lamina”, Barnard 1929) ( Fig. 2 A) with margin lobate, present on exopod, equal to epipodital lamina of fourth pair.

Remaining thoracopods of typical form, having six endites and numerous digitiform exites on exopods. Epipodite gradually increasing in length till eighth thoracopod. Here it is twice the length of third, fourth and eleventh thoracopods and 1.2 and 1.7 times as long as epipodite of ninth and tenth thoracopods respectively.

Nineteen posterior body segments with dorsal armature ( Fig. 2 B). Armature on each segment from anterior to posterior consists 0,2,3,5,5,5,7,9,12,14,14,14,14,13,13,12,12,11, and 10 small acutely pointed spines of varying lengths. Spines denticulate and slightly curved apically. These spines extend laterally on each segment.

Telson ( Fig. 2 C) asymmetrical and with about 40 (actually 43 and 41 in holotype) unequal denticles and with a short spinular outgrowth terminally. Telsonic filaments located anterior to the denticles. Ventral margin of telson shorter than dorsal margin and with a pair of furcal claws (=cercopods). Furcal claws as long as dorsal margin of telson ( Fig. 2 D) elongated, triangular in cross section with two dorsal edges, medial edge fringed with about 35 pointed spines, lateral surface glabrous.

Description. Female.

Carapace hinge line straight, not forming angles in anterior and posterior regions on carapace. Growth lines 11. Otherwise carapace similar to that of male ( Figs 1 B–D).

Head ( Fig. 2 E) oval; rostrum triangular, fornix prominent arising from dorsal angle of rostrum; small spine present at fornix apex about half the length of fornix.

First antenna ( Fig. 2 E) smaller than in males and reaching second antenna second flagellomere. First antenna with 12 sensory lobes on left and right ramus; each with several sensory aesthetascs

Second antenna ( Fig. 2 E) flagellae unequal in size; anterior flagellum of 11 flagellomeres and posterior flagellum of 12 flagellomeres. Each flagellomere armed with 2–5 serrated spines anteriorly (apparently dorsal) and 2–4 thin plumose setae posteriorly (apparently ventral).

Trunk with 24 pairs of thoracopods. Gross structure of thoracopods similar to that of male. Thoracopod I with fifth endital palp unsegmented, 84% of sixth endite length ( Fig. 2 F). Thoracopod II with length of palp on fifth endite equal to that of sixth endite. Palps with numerous setae distally. Thoracopod X and XI dorsal lobes of exopods (d-ex, Fig. 2 G) modified as elongated cylindrical structures to hold egg masses.

Seventeen posterior body segments with dorsal armature. Armature on each segment from anterior to posterior consists 1,2,2,2,3,5,7,9,11,13,13,14,14,14,13,13 and 11. In other characters female dorsal armature resembles that of male.

Telson assymetrical; 38 unequal serrated denticles with short spinular outgrowth terminally. Furcal claws with two dorsal edges, medial edge fringed with pointed spines, 42 in number. In other characters, female telson resembles that of male.

Egg morphology ( Fig. 2 H). Egg diameter 105.52 ± 8.45 mm (N = 25). Egg spherical and light brown; surface with irregular markings.

Differential diagnosis. Lepthestheriella simhadrii sp. nov. has similar numbers for many numeric features as L. nobilis s.l. so that numbers of growth lines, first antennae sensory lobes, flagellomeres, thoracopods, telsonic spines and furcal claw spines overlap in the two species, though the number of growth lines are generally fewer in L. simhadrii sp. nov. The other valid Indian species, L. sarsi , has different body parameters, with 28–30 growth lines, 13–14 first antenna sensory lobes, 16–17 second antenna flagellomeres, and 26 thoracopods. Absolute diagnostic features of L. simhadrii include a fringe of blunt, peg like, subcylindrical spinules on the growth lines, rugose carapace surface between the growth lines, lateral surface of furcal claws glabrous, though medial margin with a row of spinules, and in females the endopodital palp on the fifth endite of the third thoracopod is slightly longer than the sixth endite.

Ecology. L.simhadrii sp. nov. was collected from temporary pool and ditches of clear water, devoid of vegetation. Water temperature 31.2o C; dissolved oxygen 7.5 mg. L -1; pH 7.6; conductivity 168µS.cm -1, turbidity 5.85 NTU.

Remarks. This species is assigned to the genus Leptestheriella based on the following characters: rostrum bearing a spine, occipital angle acutely produced, occipital groove moderately deep, and exopod margins of the thoracopods carry digitiform processes. The validity of this genus has been questioned by Brtek (1997), with the suggestion that it be synonymised into Lepthestheria Sars. However, this proposal has been ignored ( Dumont & Negrea, 2002; Garcia & Pereira, 2003), probably either because the evidence is thought by some to be weak or because the proposal was not formalized. Nevertheless the concept may well have merit (D.C. Rogers, pers. comm.), but until there is a generic revision within the family Leptestheriidae , we regard Leptestheriella as valid.

Five species of Leptestheriella have been recorded from India: Leptestheriella nobilis (Sars 1900) , L. hendersoni (Sars 1900) , L. sarsi Daday1923 , L. gigas Karande & Inamdar1960 and L. maduraensis Nayar & Nair 1968 . All these species are recorded from South India, except L. gigas which is known from Panchagani of Bombay.

Leptestheriella nobilis and L. hendersoni were initially described by Sars (1900) on limited material from south India. Daday (1923) used the same material to redescribe these species and to add L. sarsi . He distinguished the three species by: 1) presence or absence of acute angles on the anterior and posterior ends of the carapace, 2) carapace sculpture, and 3) nature of the occipital angles of the head, rostrum and telson. However, study of many populations of these species in Andhra Pradesh over many years have shown these and other characters to be highly variable (for L. nobilis see Table 1).

Females of Leptestheriella hendersoni (no males are known) with their 24–31 growth lines, triangular rostrum, 25 thoracopods, 10–12 first antenna sensory lobes, 13–15 second antenna fagellomeres, and 24 telsonic spines fall within the range of variation of L. nobilis and therefore this species is considered synonymous with L. nobilis .

For L. gigas, Karande & Inamdar 1960 claim this species can be recognized based on the shape of the carapace, acute posterodorsal corner of the carapace in adult females, carapace sculpture as described in L. nobilis , strongly produced occipital angle and shape of rostrum, 13–14 first antenna sensory lobes, 14 second antenna antennomeres, 24–26 thoracopods and 31 telsonic spines. However all these characters are highly variable and fall within the range of variation in L. nobilis collected from Andhra Pradesh. Hence this species is treated as a synonym of L. nobilis (Sars 1900) .

L. maduraensis Nayar & Nair 1968 described from Madurai, South India, differs from L. nobilis in the number of sensory lobes (males 21, females 15–16), second antenna flagellomeres (16) and thoracopods (male 20, female 24). However in all other characters this species agrees with the description of L. nobilis . Furthermore carapace sculpture of L. maduraensis studied under SEM by Samyiah et al. 1985 agrees in all details with that of L. nobilis ( Figs 3 A, B). The apparent differences from L. nobilis are probably just evidence of further variation in these characters and there are no diagnostic characters shown unique for L. maduraensis to distinguish it from L. nobilis . This species is also regarded as a synonym of L. nobilis .

Similar observations of variability in leptestheriids and other spinicaudatans of diagnostic characters have been noted by Straškraba (1966) and recently by Timms (2009) on Euleptestheria. Efforts to study leptestheriid shrimps in detail based on large number of specimens will possibly reduce the number of valid species and clear present ambiguity.

Despite its variability L. nobilis is regarded as a valid species. Other useful characters for its delineation include: 1) growth lines and margins of carapace with small delicate setae ( Fig. 3 A), 2) carapace sculpture with areolate ( Fig. 3 B) or round markings of various sizes, and 3) minute serrated spines ( Fig. 3 C) present on the two dorsomedial edges of the furcal claw.

Leptestheriella simhadrii sp. nov. is variable between sites ( Table 2 ). In summary: males have 6–19 growth lines (7–18 in females) closely spaced towards ventral margin in older specimens; rostrum broad or spatulate; ocellus position variable; 13– 17 male first antenna sensory lobes (11–14 in females), 10–13/11– 14 male second antenna flagellomeres (11–12/ 12–14 in females), 23– 25 male pairs of thoracopods (23–24 pairs in female), 26– 47 male telsonic denticles (30–45 in female) and 31– 47 male furcal claw spines (25–42 in female).

Figures

FIGURE 1. Leptestheriella simhadrii sp. nov. Male A – G, A, entire; B, carapace growth lines (gl = growth lines; hl = hinge line); C, rib-like growth lines (r = rib); D, carapace sculpture at high magnification (bps = blunt, peg like, sub cylindrical spinules); E, head with first and second antenna (a 1 = first antenna; a 2 = second antenna; fo = fornix; h = head; oc = ocellus; ro = rostrum; s = spine); F, first thoracopod clasper (ap = apical projection; hn = hand; lp = large palp; mf = movable finger; sp = small palp); G, second thoracopod clasper. Scale bars A, B- 1 mm. E – G 0.5 mm.

FIGURE 2. Leptestheriella simhadrii sp. nov. Male A – D, Female E – G. A, third thoracopod showing exopod and endopod separately (en 1 = endite 1; en 2 = endite 2; en 3 = endite 3; en 4 = endite 4; en 5 = endite 5; en 6 = endite 6; epl = epipodal lamina; ex = exopod; pa = palp); B, Lateral view of dorsal armature (da = dorsal armature) showing one on few post abdominal segments; C, telson (t = telson); D, furcal claw (fc = furcal claw); E, head with first and second antenna (a 1 = first antenna; a 2 = second antenna; h = head); F, first thoracopod fifth and sixth endites (en 5 = endite 5; en 6 = endite 6; pa = palp); G, tenth thoracopod (d-ex = dorsal lobe of exopod); H, egg. Scale bars 0.5 mm. H, 0.1 mm. B, 0.25 mm.

FIGURE 3. Leptestheriella nobilis (Sars 1900). Male A – C, A, carapace growth lines and setae (se = setae); B, carapace markings (ar = areolate); C, furcal claw showing spines on two edges (s = spine).

Tables

TABLE 2. Morphological variability in some features of Leptestheriella simhadrii sp. nov.

Characters	Racharla (Pool)	Mean	Anumalapalli (Ditches)	Mean	Kaluvapalli Mean (Puddles)
Specimens exam- 3 ined Ƥ	26 30		25 30		14 30
3L Carapace size(mm) 3H	2.3 – 5.5 1.5 – 3.0	3.9 2.25	3.0 – 5 2 – 3	4 2.5	2 – 5 3.5 1.5 – 3.2 2.35
ƤL	3.0 – 6.0	4.5	1.5 – 5	3.25	2.5 – 6 4.25
ƤH	1.0 – 3.5	2.25	2.0 – 3.5	2.75	1.5 – 3 2.25
Growth lines 3	6 – 10	8	6 – 19	12.5	6 – 19 12.5
Ƥ	7 – 14	10.5	7 – 18	12.5	7 – 18 12.5
First antenna sen- 3 sory lobes Ƥ	13 – 17 11 – 14	15 12.5	15 – 16 11 – 13	15.5 12	14 – 16 15 13 – 14 13.5
Second antenna 3 flagellomeres Ƥ	10–13/13–13 11–12/13–13	11.5 / 13 11.5 / 13	12–13/13–14 12–12/13–14	12.5 /13.5 12 / 13.5	13–13/11–14 13 / 12.5 12–13/12–14 12.5 / 13
Thoracopods 3	23 – 24	23.5	23 – 25	24	23 – 24 23.5
Ƥ	23 – 24	23.5	23 – 24	23.5	23 – 24 23.5
Telsonic denticles 3	26 – 43	34.5	38 – 40	39	35 – 47 41
Ƥ	30 – 44	37	30 – 42	36	37 – 45 41
Spinulose spines on 3 furcal claw inner Ƥ edge	33 – 43 25 – 42	38 33.5	37 – 47 35 – 40	42 37.5	31 – 45 38 35 – 39 37