Brevicyclops brevisetosus

Totakura, Venkateswara Rao & Reddy, Yenumula Ranga, 2015, Groundwater cyclopoid copepods of peninsular India, with description of eight new species, Zootaxa 3945 (1), pp. 1-93 : 41-43

Brevicyclops brevisetosus n. g., n. sp.

( Figs. 24–29 )

Type locality. Farm bore (water temperature 28ºC, pH 7.0) at Kunchanapalli village (16º23′42.1″N, 80º32′28.2″E, elevation 26 m) in Guntur District, Andhra Pradesh, South India ( Fig. 1 ).

Type material examined. Holotype male (MNHN-IU-2013-11865) and allotype female (MNHN-IU-2013- 11866), dissected on 3 slides; 3 paratypes: 1 male, dissected on 3 slides (MNHN-IU-2013-11867), 1 male, wholemounted on 1 slide, and 1 male in alcohol in senior author’s personal collection; 0 4 January 2010; Coll. V. R. Totakura.

Diagnosis. Small cyclopinae; total body length of females 352 µm; of males 348–361 µm. Body robust. Female double-genital somite 0.7 times as long as wide; anal operculum bowl-shaped, reaching distal margin of anal somite. Caudal rami 1.6 times as long as wide, with principal outer apical seta greatly reduced. Antennule 11- segmented in female, and 17-segmented in male. Spine formula of second exopodal segment of legs 1–4: 2.2.2.2; setal formula: 5.5.5.4; leg 4 with 2-segmented rami in both sexes; coxa of all legs ornamented with spinular row near outer margin. Leg 1 inner basal spine absent. Coxal seta absent only on leg 4. Intercoxal plates of legs 1–4 with small, rounded and smooth prominences. Leg 5 reduced to 3 setae, 1 outer and 2 inner; the latter inserted close to each other. Leg 6 reduced to 2 very small elements.

Description of adult male. Total body length, measured from base of rostrum to posterior margin of caudal rami (excluding caudal setae), 351 Μm. Naupliar eye absent. Body ( Fig. 24 a) somewhat robust, with prosome/ urosome ratio 1.6 and greatest width at posterior end of cephalothorax. Body length/width ratio 2.8. Cephalothorax ( Fig. 24 a) as long as wide, not produced postero-laterally, 41.8% of total body length. Rostral projection ( Fig. 26 a) well developed, broadly triangular, linguiform, and with 2 short sensilla on dorsal surface subdistally. Free pedigerous somites 2 and 3 with unproduced, straight postero-lateral margins; second pedigerous somite as wide as cephalothorax; fourth pedigerous somite with only slightly produced postero-lateral angles. Arthrodial membranes between free pedigerous somites well developed and hyaline frill slightly developed mid-dorsally, smooth on all segments; all somites slightly chitinised, imperforated, no spinules and cuticular windows discernible; sensilla as illustrated; somites 3 and 4 gradually narrowing. Pseudosomite between prosome and urosome absent. Posterior part of fifth pedigerous somite about as wide as genital somite, lateral margins oblique, and ornamented with 4 sensilla. Genital somite ( Figs. 24 a, 25a, b) 0.7 times as long as wide, ornamented with 2 dorsal sensilla; hyaline fringe of genital somite as well as next 2 somites narrow and smooth. Spermatophore ( Fig. 24 a) small, oval, 2.3 times as long as wide. Anal somite ( Fig. 25 a, b) 0.6 times as long as wide, ornamented with transverse row of spinules latero-ventrally on posterior margin. Anal operculum ( Fig. 24 a) moderately developed, smooth, 73% of somite’s width, slightly overreaching posterior margin of somite, and with nearly straight posterior margin. Anal sinus without apparent ornamentation.

Caudal rami ( Figs. 24 a, 25a, b) parallel, close to each other and 17% longer than anal somite; each ramus 1.7 times as long as sub-proximal maximum width; ornamented with a row of tiny spinules disto-ventrally; spinules also occurring at base of outermost apical setae ( Fig. 25 b); dorsal seta inserted at 4/5 of ramus length and uniarticulate at base, about half as long as principal inner apical seta; lateral seta arising from dorsal surface close to outer margin at 3/5 of ramus length and 0.6 times as long as maximum width of ramus; outermost apical seta 0.7 times as long as ramus, inserted subapically; innermost apical seta slender and about as long as outermost apical seta; principal apical setae without breaking planes; outer seta greatly reduced in size, bipinnate, only slightly shorter than innermost apical seta; inner seta 2.2 times as long as dorsal seta; outermost apical seta unipinnate; all other setae bipinnate.

Antennule ( Fig. 24 b): 17-segmented, digeniculate, geniculation between segments 9 and 10, and 15 and 16. Armature formula as follows: 7+aes.3.0.1+aes.1aes.1.1.0.1.0.0.1aes.2.0.1aes.0.8; all aesthetascs slender and elongate; most setae slender and smooth; setae on segments 9 and 13 short unipinnate; segments 1, 13 and 17 with 1, 1 and 4 long pinnate setae, respectively. Length ratios of antennular segments along medial axis 1.0: 0.3: 0.2: 0.2: 0.2: 0.1: 0.2: 0.1: 0.4: 0.1: 0.3: 0.4: 0.1: 0.2: 0.6: 0.5: 0.9; concave sclerotized structures present on segments 15 and 16.

Antenna ( Fig. 26 c): 4-segmented, consisting of coxobasis and 3-segmented endopod. Setal formula of endopod: 1.5.7. Coxobasis about twice as long as wide, armed with 1 seta at inner distal corner and unornamented; exopodal seta absent. First endopodal segment 1.3 times as long as wide, ornamented with 1 row of spinules at outer distal corner and armed with 1 seta on subdistal inner margin. Second segment 1.9 times as long as maximum width, ornamented with 1 row of spinules at outer distal corner and armed with 5 unequal setae (1 inner marginal, 2 subapical, 2 disto-marginal); third segment cylindrical, 2.3 times as long as wide, ornamented with 1 row of spinules along outer distal margin and armed with 7 unequal simple setae.

Labrum ( Fig. 26 c): small, trapezoidal, anterior cutting edge almost straight, with small, acute teeth between slightly produced triangular lateral corners; no ornamentation discernible.

Mandible ( Fig. 26 d): coxal gnathobase cutting edge with 2 large teeth on anterior surface; ventralmost tooth stronger and complex; a row of 6 teeth on apical margin between large teeth and unipinnate seta and also a row of small spinular teeth on ventral subapical surface. Palp absent.

Paragnaths ( Fig. 26 e): conical, apparently separate; ornamented with hair-like spinules on lateral margins.

Maxillule ( Fig. 26 f): composed of praecoxa and 2-segmented palp. Praecoxal arthrite bearing 3 strong clawlike spinous processes and 1 stout, pinnate seta and 6 medial elements (proximal one longest and pinnate, others naked). Palp composed of coxobasis and endopod. Coxobasis with 1 smooth proximal (exopodal) seta and 1 strong apical, bipinnate spine, 2 apical simple setae distally; endopod with 2 apical and 1 subapical plumose setae.

Maxilla ( Fig. 26 g): 4-segmented; praecoxa fused to coxa. Proximal endite of praecoxa small and armed with 1 short, simple seta and 1 long pinnate seta; distal endite much reduced, unarmed. Proximal endite of coxa with 1 smooth seta; distal endite elongate and armed apically with 2 equal pinnate setae, which are not distinct at base; no ornamentation discernible on posterior surface of coxa. Basis expanded into robust, prehensile claw with serrulate inner margin, and armed with 2 setae: 1 smooth, weak seta at base of claw and 1 very strong bipinnate seta, slightly longer than claw. Endopod 2-segmented; proximal segment armed with 2 pinnate claws, proximal claw with serrulate inner margin and 2.1 times as long as distal one; distal segment smallest, with 1 robust, unipinnate, apical claw and 2 slender, smooth, subapical setae.

Maxilliped ( Fig. 26 h): 4-segmented, consisting of syncoxa, basis and 2-segmented endopod. Syncoxa 1.8 times as long as wide, armed with 2 subdistal setae on small protrusion, and ornamented with 1 row of spinules on outer margin. Basis 1.6 times as long as wide, armed with 1 seta at inner distal corner and 1 seta on distal margin, and ornamented with 1 row of spinules on outer distal margin. First endopodal segment armed with 1 seta; second one with 2 unequal setae. All segments with bipinnate setae.

Legs 1–4 ( Fig. 27 a–d): relatively short, with 2-segmented exopod and endopod. Hairs present on rounded inner margin of basis; lateral margins of exopod and endopod ornamented hair-like spinules, as illustrated. Endopod nearly as long as exopod on legs 1–3, but distinctly shorter on leg 4. Second exopodal segment spine formula of legs 1–4: 2.2.2.2; setal formula: 5.5.5.4. Coxae of all legs ornamented with a row of spinules near sub-proximal outer corner. Intercoxal plate with 2 small, smooth, rounded prominences each on all legs. Inner basal spine absent on leg 1. Coxal seta present on legs 1–3 only. Spine and setal formulae (legend: same as that of Paracyclopina orientalis ):

Coxa Basis Exopod Endopod

1 2 1 2

Leg 1 1-0 0-1 0- I 4, 1+I, I 1 -0 1, 1+I, 1 Leg 2 1-0 0-1 0- I 4, 1+I, I 1 -0 1, 1+I, 1 Leg 3 1-0 0-1 0- I 4, 1+I, I 1 -0 1, 1+I, 1 Leg 4 0-0 0-1 0- I 3, 1+I, I 1 -0 1, 1+I+0 Leg 5 ( Figs. 24 a, 25a, b): completely fused to somite and represented by 3 plumose setae; basal seta longest and lying on small protuberance; other 2 setae small, unequal and located on short prominence, representing ancestral distal segment.

Leg 6 ( Fig. 25 a, b): both legs partly fused proximally; each leg large, cuticular plate-like, with distinct septum medially, and armed with 2 small, equal setae on distal margin.

Description of adult female. Total body length 357 Μm. Prosome/urosome ratio about 1.7 and greatest width at posterior end of cephalothorax. Body length/width ratio 3.1. Cephalothorax about as long as wide, representing 43% of total body length. Hyaline fringe of fifth pedigerous somite smooth and ornamented with 4 dorsal sensilla, as in male. Genital double-somite ( Figs. 28 a, 29a, b) about as long as wide, with smooth, narrow hyaline fringe dorsally and ornamented with 2 large sensilla; seminal receptacle small, consisting of anterior posterior parts; anterior part relatively large and concave; a small internal cuticular thickening visible, but not copulatory duct; next 2 urosomites without any sensilla and hyaline fringe narrow. Anal somite and caudal rami same as in male.

Antennule ( Fig. 28 b): 11-segmented, ornamented with proximo-ventral row of spinules on first segment (no pits or other integumental structures), with armature formula as follows: 7.2.5.2.1.2.2.3.5.3.7+aes. Segments 1, 3, 9, 10 and 11 with 1, 2, 2, 1 and 3 long bipinnate setae, respectively; all other setae smooth; no aesthetascs. Length ratios of antennular segments along medial axis 1.0: 0.2: 0.6: 0.3: 0.2: 0.4: 0.6: 0.5: 0.3: 0.5: 0.6.

Antenna, labrum, mandible, paragnaths, maxillule, maxilla, maxilliped, and legs 1–5 similar to male.

Leg 6 ( Fig. 29 a, b): large, unornamented cuticular plate, with 2 short spinous projections.

Etymology. The specific epithet is derived from the Latin adjective setosus (= bristle-bearing) to which the Latin brev i- (= short) is prefixed, alluding to the greatly reduced principal outer apical caudal seta; gender masculine.

Variation. Body length of males ranges from 323 Μm to 356 Μm; inner medial apical seta is 1.8–2.2 times as long as dorsal seta.

Distribution and ecology. The new species was collected only from type locality, and it was accompanied by Nitocrella sp., and a new parastenocaridid sp.

Figures

FIGURE 1. Map showing the type localities of the cyclopoid species on the Indian peninsula.

FIGURE 24. Brevicyclops brevisetosus n. g., n. sp. (a) paratype male, habitus, dorsal; (b) holotype male, antennule, lateral.

FIGURE 25. Brevicyclops brevisetosus n. g., n. sp., paratype male (a, c); holotype male (b). (a) urosome, lateral; (b) same, ventral (arrow pointing to reduced seta); (c) leg 5, latero-ventral.

FIGURE 26. Brevicyclops brevisetosus n. g., n. sp., holotype male. (a) rostrum, ventral; (b) antenna, lateral; (c) labrum, ventral; (d) mandible, lateral; (e) paragnaths, ventral; (f) maxillule, lateral; (g) maxilla, lateral; (h) maxilliped, lateral.

FIGURE 27. Brevicyclops brevisetosus n. g., n. sp., holotype male. (a) leg 1, posterior; (b) leg 2, posterior; (c) leg 3, posterior; (d) leg 4, posterior.

FIGURE 28. Brevicyclops brevisetosus n. g., n. sp., allotype female. (a) urosome, dorsal; (b) antennule, lateral.

FIGURE 29. Brevicyclops brevisetosus n. g., n. sp., allotype female. (a) urosome, lateral; (b) same, ventral (arrow pointing to reduced seta).