Streptocephalus sahyadriensis, Rogers, D. Christopher & Padhye, Sameer, 2014

Rogers, D. Christopher & Padhye, Sameer, 2014, A new species of Streptocephalus (Crustacea: Anostraca: Streptocephalidae) from the Western Ghats, India, with a key to the Asian species, Zootaxa 3802 (1), pp. 75-84 : 76-81

Streptocephalus sahyadriensis sp. nov.

( Figures 1 and 2 )

Etymology. The specific epithet “ sahyadriensis ” refers to ‘Sahyadri’ which is the Sanskrit name for the Western Ghats.

Type locality. ( Figure 1 ) A pool in laterite with a mud covered, rocky substrate on the Panchgani Tableland. Pool depth was 6-8 cm at the time of collection, with turbid water and no aquatic vegetation. Two other species of large branchiopods ( Triops granarius (Lucas, 1864) and Leptestheria nobilis Sars, 1900 ) were seen to co-occur with this species.

Type material. Holotype. Male, data: INDIA: Maharashtra: Panchgani: Tableland, 17° 55' 22.79"N, 73° 48' 18"E, 21 August 2012, S. Padhye, Y. Shinde, A. Vanjare, collectors, Deposited: Zoological Survey of India: ZSI- C.1172.

Allotype. Female, same data: ZSI-C.1173.

Material examined. INDIA: Maharashtra: Chalkewadi Plateau: 17° 28' 44.39"N 73° 50' 9.59"E, 11 July 2012, five males, four females, S. Jakhalekar, collector. Mhavshi Plateau: 17° 24' 42.99"N 73° 56' 22.99"E, 31 August 2013, two males, two females, S. Kulkarni, M. Kulkarni, S. Paripatyadar, and S. Sheth, collectors.

Description. Male.( Figure 2 ) Head rounded, sub cylindrical. Frontal appendage short, dorsoventrally elongate, width uniform, 0.13 times the length of the first antennae.

First antennae subequal in length to second antenna proximal antennomere ( Figure 2 A), apex truncated, bearing four to six setae.

Second antennae including antennal appendages extending posteriorly to tenth thoracic segment. Second antenna proximal antennomere subcylindrical, approximately 2.5 times as long as broad. Medial surface smooth, lacking a pulvinus or pulvillus (sensu Maeda-Martínez et al. 1995). Second antennal distal antennomere subequal in length to proximal antennomere, laterally directed, subcylindrical, arcing medially, curving evenly along its length, broadening slightly distally. Antennal appendage peduncle ( Figure 2 A) 1.25 times as long as second antenna proximal antennomere, subcylindrical, subgeniculate at each third its length. Proximal geniculation directed posteriorly, distal geniculation directed anteriorly. Peduncle at proximal geniculation with an anteriomedial, oblique row of elongate, conical papillae subequal in length. Papilla length twice peduncle width. Each papilla armed with a ventrolateral, longitudinal row of spines. Spines bearing a tumid base, apex recurved, directed distally. Spines decreasing in size and increasing in distance distally, with proximal spines separated by 0.25 the spine length, distal spines separated by four times their length. Antennal appendage peduncle distal geniculation, bearing a lateral longitudinal row of 8 to 12 anteriorly directed spines. Spines smooth, apically acute and length subequal to peduncle width. Antennal appendage apical cheliform structure (so called “hand” see Maeda-Martínez et al. 1995) bearing a lateral, triangular spine on lateral surface between bases of anterior and posterior primary rami. Cheliform structure with posterior ramus (so called “finger” see Maeda-Martínez et al. 1995) subequal in length to second antenna plus antennal appendage peduncle. Posterior ramus (“finger”) ( Figure 2 D) bearing a single anterior “tooth” and a single posterior “tooth” (ventral protuberance of Maeda-Martínez et al. 1995). Anterior “tooth” broadly rounded, width subequal to height. Posterior “tooth” triangular, apex directed distally. Posterior ramus (“finger”) with a posteriolateral sickle shaped ramus (“lower finger” of Sanoamuang et al. 2000a) originating just distad to posterior “tooth” ( Figure 2 A and C), broadly arcing anteriorly approximately 270°, with apical tenth arcing laterally, nearly attaining the apex of the primary ramus (“finger”). Posteriolateral branch crenulate along distal half of anterior margin ( Figure 2 C, E). Posterior ramus (“finger”) proximal two thirds straight, directed distally ( Figure 2 A, C, and E). Distal third proximally with a broad 90° arc directed laterally ( Figure 2 A and F). Distal third with apical fourth with a broad 90° arc anteriorly, with apex arcing 90° distally and armed anteriorly with a row of 4–5 small spines ( Figure 2 A, C, and F). Posterior ramus anterior margin with a double, longitudinal row of spines extending from a point even with the posteriolateral branch to the first distal arc ( Figure 2 A, C, E, and F). Spines in row not entirely in series (some spines out of line). Spines of medial row increasing in size and separation distally, distal most spines with bases directed medially with apices arcing anteriorly. Medial row spines greatly tumid proximally, aciculate distally. Aciculate portion becoming more arcuate in the more distad spines of the medial row. Lateral row with spines aciculate, arcing laterally, rarely longer than medial row spine tumid bases. Anterior primary ramus ( Figure 2 B)(the so called “thumb” see Maeda-Martínez et al. 1995) with an anterior, longitudinal, chitinized carina, ending distally as a rounded, lamellar projection. Anterior ramus (“thumb”) posterior branch (“spur”) smooth, arcuate, recurving posteriorly about 80°. Triangular gap, becoming a narrow, deep cleft between “spur” and anterior ramus (“thumb”), at least as long as opening width. Anterior ramus (“thumb”) gently arcuate, curving anteriorly approximately 20°.

Labrum smooth, rounded, and directed posteriorly, apex triangular. Mandibles and maxillae typical for the members of the genus.

Thoracopods serially homologous, increasing in size from the anterior pair to the fifth pair, then decreasing in size posteriorly to the eleventh pair. Praeepipodites and epipodites typical for genus. Thoracopod I with exopodite narrowly oval margined with elongate plumose setae; endopodite broadly triangular, margined with plumose setae; endites margined with elongated, close set, plumose setae, extending posteriorly between the thoracopods to Thoracopod III. Thoracopod V with exopodite oval, but arcing laterally, with apex rounded and margined with plumose setae; endopodite broad, angular, margined with spiniform setae; endites margined with elongated, close set, plumose setae, extending posteriorly between the thoracopods to Thoracopod VIII; thoracopod XI with exopodite oval, lacking setae; endopodite broadly oval, margined with stout spines; endites reduced, with short filiform setae.

Genital segments smooth and typical for the genus. Gonopods each with basalolateral linguiform outgrowth. Gonopods each with a proximomedial spur. Everted gonopod of typical form for genus. Everted gonopods elongated, extending to abdominal segment V. Gonopod proximal half smooth, unarmed, distal half bearing a lateral, longitudinal row of spines. Gonopod distal third with scattered spines on medial and ventral surfaces. Gonopod with spines absent from apical tenth. Everted gonopod apex bearing a single medially directed spine. Testes uniramal, extending from genital segments (thoracic segments XII and XIII) posteriorly to abdominal segment VI.

Abdomen as typical for the genus.

Cercopods, straight, parallel sided, margined with plumose setate.

Female. First antennae 1.25 times length of the eye plus peduncle and 0.75 times the length of second antennae. Second antennae broad, oval, flattened, smooth, without any protrusions. Apex acute, triangular. Labrum, mandibles and maxillae as in male. Thorax smooth. Thoracopods as in male.

Brood pouch fusiform and smooth. Brood pouch extending to abdominal segment V or VI. Ovaries uniramal, extending posteriorly into abdominal segment V or VI.

Cercopods as in male.

Egg. ( Figure 2 G). Spherical. Approximately 250 µm in diameter, with large, subcircular, flat areas 0.25-0.30 times the diameter of the egg. The flat areas are separated by narrow ridges that have longitudinal folds.

Size. Male average length (from anterior margin of head to posterior margin of telson, not including cercopods) of preserved material 1.96 ± 0.15 cm. Female average length of preserved material (from anterior margin of head to posterior margin of telson, not including cercopods) 1.69 ± 0.071 cm.

Differential diagnosis. Streptocephalus sahyadriensis sp. nov. belongs to the Streptocephalus dichotomus group (Maeda-Martínez et al. 1995). This group includes S. dichotomus , S. echinus , S. longimanus , S. simplex , and S. sirindhornae . The group is defined as have a long peduncle, lacking a pulvinus, antennal appendage posterior ramus (“finger”) with a sickle shaped ramus and lacking a ventral protuberance, gonopods with linguiform outgrowths, proximal portion of gonopods ending at the middle of abdominal segment I, ovaries uniramus, and having setose cercopods (Maeda-Martínez et al. 1995). Streptocephalus sahyadriensis sp. nov. is the only species in this group that possesses a ventral protuberance on the antennal appendage posterior ramus (“finger”).

Streptocephalus sahyadriensis sp. nov. is most similar to S. simplex and S. dichotomus . Streptocephalus sahyadriensis sp. nov. and S. simplex species are separated from all other members of the S. dichotomus group by the form of the major spines in the medial anterior longitudinal row on the antennal appendage posterior ramus (“finger”). These spines are strongly tumid basally, with aciculate distal halves. The two species are separated by the form of the antennal appendage posterior ramus (“finger”) sickle shaped ramus, which is strongly crenulate in S. sahyadriensis sp. nov. and smooth in S. simplex . Additionally, S. simplex has a single longitudinal row of spines on the antennal appendage posterior ramus (“finger”) that continue nearly to the end of the ramus, whereas S. sahyadriensis sp. nov. has two rows of spines, which end at the first distal geniculation, with crenulations at the very tip. The antennal appendage posterior ramus (“finger”) has only one distal bend in S. simplex , but two in S. sahyadriensis sp. nov.

The overall form of the antennal appendage posterior ramus (“finger”) is the same in S. sahyadriensis sp. nov. and S. dichotomus . As stated above, the form of the spines are different between the two species, however, the last spine on S. sahyadriensis sp. nov. is strongly arcuate, whereas in S. dichotomus it is straight, continuing nearly in the same plane as the proximal three fourths of the ramus. The anterior ramus (“thumb”) posterior branch (“spur”) is only proportionally half as long in S. dichotomus as in S. sahyadriensis sp. nov. Furthermore, the antennal appendage peduncle oblique row of papillae at the proximal geniculation bear proximally tumid, recurved spines in S. sahyadriensis sp. nov. and straight spines in S. dichotomus .

The egg of S. sahyadriensis sp. nov. appears to be unique in the genus (and possibly among all anostraca ) with its large, subcircular, flat areas separated by narrow, ridges with serial folds. All other Indian Streptocephalus species have deep, polygonal depressions separated by angular (subangular in S. longimanus ) ridges.

Conservation status. Species loss due to anthropogenic activities in developing countries is poorly quantified (Brendonck et al., 2008), thus species such as S. sahyadriensis sp. nov. may be eliminated without being discovered. Lateritic outcrops from northern Western Ghats are known to harbor unique flora and fauna ( Watve 2008, 2013). To date, S. sahyadriensis sp. nov. is known from only three locations in the northern Western Ghats, and additional surveys in the region have yielded no new localities. The type locality had domestic refuse (garbage) dumped into and around the habitats. The other two sites are located in wind farms. Because of ongoing development and pollution in this region, we believe that this species is in need of conservation. Following the IUCN (2000) categories, we would designate this species as CR B2ab: critically endangered, geographic range estimated to be less than 10km 2, habitat severely fragmented and populations inferred to be declining in extent and habitat quality.

Figures

FIGURE 1. Distribution of Streptocephalus sahyadriensis sp. nov. Shaded (grey) region represents northern part of the Western Ghat range, Maharashtra state, India. Black dots represent the collection localities.

FIGURE 2. Streptocephalus sahyadriensis sp. nov. Male. A, Head, left lateral view. B – F, left second antenna. B, “ thumb ”. C, “ finger ”. D, “ finger ” basal portion, detail. E, “ finger ” middle portion, detail. F, ‘ finger ” distal portion, detail. G, Egg. (scale bar = 50 µm).