Monchenkocyclops changi, Karanovic & Yoo & Lee, 2012

Karanovic, Tomislav, Yoo, Hyunsu & Lee, Wonchoel, 2012, A new cyclopoid copepod from Korean subterranean waters reveals an interesting connection with the Central Asian fauna (Crustacea: Copepoda: Cyclopoida), Journal of Species Research 1 (2), pp. 156-174 : 158-170

Monchenkocyclops changi sp. nov.

( Figs. 1-8 )

Type locality. South Korea, Gangwondo region , Pyeongchang city, Jinbu town, Odae stream, 37̊36′43.5′′N 128̊ 33′09.2′′E, 516 m a.s.l., interstitial water from sandy bank .

Type material. Holotype female dissected on two slides ( NIBRIV0000232646 ) . Allotype male also dissected on two slides ( NIBRIV0000232647 ). Other paratypes are one male and two females on one SEM stub ( NIBRIV 00 00232648), one female dissected on one slide ( NIBRIV 0000232649 ); all collected at type locality; leg. J.-L. Cho, 24 April 2010 .

Etymology. The new species is named in honour of Prof.

Cheon Young Chang (Daegu University, Korea), in recognition of his enormous contribution to our knowledge of freshwater copepods in Korea. The name is a noun in the genitive singular.

Description. Female (based on holotype and three paratypes). Total body length, measured from tip of rostrum to posterior margin of caudal rami (excluding caudal setae), from 789 to 796 µm (792 µm in holotype). Preserved specimens colourless; no live specimens observed. Integument weakly sclerotized, smooth, without cuticular pits or cuticular windows. Surface ornamentation of somites consisting of 111 pairs and 12 unpaired (mid-dorsal) pores and sensilla (numbered with Arabic numerals consecutively from anterior to posterior end of body, and from dorsal to ventral side in Figs. 1A , 2 A-E, 3A, B, 4A); no spinules except on anal somite, caudal rami, and appendages. Habitus ( Fig. 1A ) relatively robust, not dorso-ventrally compressed, with prosome/urosome ratio 1.5 and greatest width in dorsal view at posterior end of cephalothorax. Body length/width ratio about three (dorsal view); cephalothorax 2.3 times as wide as genital double-somite. Free pedigerous somites without lateral or dorsal expansions, all connected with well developed arthrodial membranes, and with narrow and smooth hyaline fringes. Pleural areas of cephalothorax and free pedigerous somites relatively well developed, covering insertions of cephalic appendages and praecoxae and partly coxae of swimming legs in lateral view.

Rostrum ( Fig. 2D ) well developed, membranous, not demarcated at base, broadly rounded and furnished with single central sensilla frontally (no. 1) and one pair of sensilla (no. 2) and pores (no. 3) at its base; latter probably marking boundary between cephalothorax and rostrum.

Cephalothorax ( Figs. 1A , 2A, B ) as long as its greatest width (dorsal view), much narrower at anterior part and nicely oval; representing 34% of total body length. Surface of cephalic shield ornamented with six unpaired dorsal sensilla (nos. 4, 12, 18, 29, 43, 56) and 66 pairs of long sensilla and small cuticular pores (nos. 4-11, 13-17, 19- 28, 30-42, 44-55, 57-75); pores and sensilla 56-75 belong to first pedigerous somite, incorporated into cephalothorax.

Second pedigerous (first free) somite ( Figs. 1A , 2C ) relatively short, ornamented with four pairs of large sensilla (nos. 76, 78, 80, 81) and three pairs of cuticular pores pores (nos. 77, 79, 82); dorsal pair of sensilla no. 76 probably serially homologous to pair no. 67 on first pedigerous somite, and perhaps pairs no. 78 and no. 70 also serially homologous; others serially homologous pairs much more difficult to reconise.

Third pedigerous somite ( Figs. 1A , 2C, E ) slightly longer than second and significantly narrower in dorsal view, ornamented with two dorsal unpaired pores (nos. 83, 89), eight pairs of large sensilla (nos. 84-86, 88, 90-93), and one pair of lateral pores (no. 87); recognising serially homologous pairs not easy, but probably sensilla pair no. 84 serially homologous to pair no. 76 on second pedigerous somite.

Fourth pedigerous somite ( Figs. 1A , 2C ) significantly shorter and narrower than third, ornamented only with four pairs of large sensilla (nos. 94-97); recognising serially homologous pairs much easier than with two previous prosomites (94=90, 95=91, 96=92, 97=93).

Fifth pedigerous (first urosomal) somite ( Figs. 3A, B , 4A ) short, significantly narrower than fourth pedigerous somite and only slightly wider than genital double-somite in dorsal view, ornamented with one pair of pores (no. 98) and two pairs of large dorsal sensilla (nos. 99, 100); recognising serially homologous pairs not as easy as with two previous somites, but probably 99=94 and 100=96; hyaline fringe smooth and very narrow.

Genital double-somite ( Figs. 3A, B , 4A ) large, with deep lateral recesses at level of sixth legs and swollen antero-ventrally, widest at first third of its length and gradually tapering posteriorly, about 1.2 times as wide as long (dorsal view), ornamented with one unpaired central dorsal pore (no. 101), two pairs of central dorsal sensilla (nos. 102, 103), one pair of ventro-lateral central pores (no. 104), one unpaired posterior dorsal pore (no. 105), two pairs of posterior sensilla (nos. 106, 108), and two pairs of vento-lateral posterior pores (nos. 107, 109); dorsal sensilla probably serially homologous to those on fifth pedigerous somite (i.e. 102=99, 103=100), but recognising serial homologies of posterior sensilla and pores much harder (perhaps 105=101, 106=103); hyaline fringe deeply and irregularly serrated. Copulatory pore very small, ovoid, situated at about midlength of double-somite ventrally; copulatory duct narrow, siphon-shaped, weakly sclerotized. Seminal receptacle with relatively large anterior expansion and much smaller posterior expansion, representing 49% of double-somite’s length; oviducts broad and weakly sclerotized. Ovipores situated dorsolaterally at 2/5 of double-somite length, covered by reduced sixth legs.

Third (ancestral fourth) urosomite ( Figs. 3A, B , 4A ) relatively short, about 1.7 times as wide as long and only 0.4 times as long as genital double-somite in dorsal view, with also deeply and irregularly serrated hyaline fringe, ornamented with unpaired dorsal posterior pore (no. 110), two pairs of dorso-lateral large sensilla (nos. 111, 112), and two pairs of vento-lateral posterior pores (nos. 113, 114); serially homologous pores and sensilla relatively easy to recognize on genital double-somite (110=105, 111=106, 112=108, 113=107 (?), 114=109).

Fourth (preanal) urosomite ( Figs. 3A, B , 4A , 8A ) narrower and shorter than third, with also deeply and irregularly serrated hyaline fringe, ornamented only with pair of lateral pores (no. 115) of uncertain serial homology.

Anal somite ( Figs. 3A, B , 4A , 8A ) slightly narrower and shorter than preanal, with short medial cleft, ornamented with one pair of large dorsal sensilla (no. 117), two pairs of small dorsal pores (nos. 116, 118), one pair of small ventral pores (no. 119), and continous posterior row of large spinules. Anal sinus smooth. Anal operculum small, short, slightly convex, not reaching posterior margin of anal somite, representing 47% of anal somite’s width.

Caudal rami ( Figs. 3A, B , 4A , 8A ) cylindrical, parallel, inserted close to each other, approximately 2.6 times as long as wide (ventral view) and twice as long as anal somite; armed with six setae (one dorsal, one lateral, and four terminal); ornamented with one dorsal pore in ante-

A B

rior part (no. 120), two lateral cuticular pores (nos. 121, 122), one pore on tip of protuberance on distal margin ventrally between two terminal setae (no. 123), rows of small spinules at base of lateral setae, and short row of minute spinules partly covering proximal lateral pore. Dorsal seta about 1.14 times as long as ramus, inserted at 5/6 of ramus’ length, biarticulate at base (inserted on small pseudo-joint) and pinnate at distal part. Lateral seta insert- ed at 2/3 of ramus’ length, 0.3 times as long as dorsal seta, unipinnate laterally and uniarticulate at base. Outermost terminal seta stout, spiniform, 0.6 times as long as ramus, densely bipinnate. Innermost terminal (accessory) seta short and slender, sparsely bipinnate, 0.75 times as long as outermost terminal seta. Principal terminal setae with breaking planes, bipinnate; inner principal terminal seta about 1.5 times as long as outer one and nearly seven times as long as caudal rami.

Antennula ( Fig. 1B ) 11-segmented, slightly curved along caudal margin, directed postero-laterally, not reaching posterior margin of cephalothoracic shield, ornament- ed just with arched proximo-ventral row of spinules on first segment (no pits or other integumental structures), with armature formula as follows (ae=aesthetasc): 8.4.8. 4.2.2.3.2+ae.2.3.7+ae. Only one terminal seta on ultimate segment biarticulating on basal part and most setae sparsely pinnate at distal end; both aesthetascs very slen- der; aesthetasc on eight segment reaching posterior margin in length. One seta on fifth segment spiniform and short; all other setae slender; one apical seta on eleventh segment fused basally to aesthetasc; second, fourth, and eleventh segments with one short seta, all other setae well developed. Length ratio of antennular segments, from proximal end and along caudal margin, 1: 0.4: 0.7: 0.4: 0.3: 0.5: 0.9: 0.8: 0.5: 0.7: 0.8.

Antenna ( Fig. 4B ) five-segmented, strongly curved along caudal margin, comprising very short coxa, much longer basis and three-segmented endopod. Coxa without armature or ornamentation, about half as long as wide. Basis cylindrical, 2.1 times as long as wide, ornamented with two short, diagonal rows of spinules on ventral surface, armed with two subequal pinnate setae close on distal inner corner (exopodal seta absent). First endopodal segment narrower at basal part but also generally cyclindrical, 1.8 times as long as wide and 0.8 times as long as basis, with inner smooth seta at 2/3 and patch of spinules along caudal margin. Second endopodal segment also with narrow basal part and twice as long as wide, about as long as first endopodal, bearing nine smooth setae along inner margin (which progressively longer from proximal to distal part), ornamented with one row of spinules along caudal margin. Third endopodal segment cylindrical, 2.4 times as long as wide and as long as second endopodal segment, ornamented with two rows of slender spinules along caudal margin, armed with seven smooth apical setae (four of them strong and geniculate).

Labrum ( Fig. 4C, F ) relatively large trapezoidal plate, with mascular base and strongly sclerotised distal margin (cutting edge), ornamented with two arched, short rows of eight long and slender spinules each on anterior surface, and central row of minute spinules between them. Cutting edge almost straight, with ten to 12 large and sharp teeth between produced and sharply and inwardly pointed lateral corners.

Mandibula ( Fig. 3E, F ) composed of coxa and small palp. Coxal gnathobase cutting edge with five slender spinules on anterior surface, eight apical teeth, and dorsalmost bipinnate seta; ventralmost tooth strongest and quadricuspidate, second and fourth teeth from ventral side bicuspidate, all other teeth unicuspidate; three dorsalmost simple teeth partly fused basally and progressively longer from ventral to dorsal. Palp twice as wide as long, unornamented, armed with three apical setae: two long and plumose and one short and smooth; plumose setae subequal in length, directed posteriorly, nearly reaching posterior margin of cephalic shield.

Maxillula ( Fig. 4D ) composed of praecoxa and two-segmented palp, unornamented. Praecoxal arthrite bearing four very strong distal spines (three smooth, blunt and fused at base; one distinct at base, sharp and with single proximal spinule) and six medial elements (proximalmost one longest and plumose, two distal-most ones with large and strong, three in middle small and slender). Palp composed of coxobasis and one-segmented endopod. Coxobasis with slender proximal seta (probably representing exopod) and three medial setae (two slender and smooth, one strong and bipinnate). Endopod with three slender and pinnate setae.

Maxilla ( Figs. 5A ) five-segmented but praecoxa partly fused to coxa on anterior surface, unornamented. Proximal endite of praecoxa robust, armed with two subequal, sparsely bipinnate setae; distal endite small, unarmed. Proximal endite of coxa with one bipinnate seta; distal endite highly mobile, elongated and armed apically with two pinnate setae, proximal one somewhat longer and much stronger. Basis expanded into robust claw, and claw furnished with longitudinal row of four strong spinules at midlength, armed with two setae; strong seta about as long as claw, pinnate. Endopod two-segmented, but segmentation not easily discernable; proximal segment armed with two robust, unipinnate setae; distal segment with one robust, unipinnate apical seta and two slender and much shorter subapical setae. Longest seta on distal endopodal segment as long as longer seta on proximal endopodal segment. All strong setae on basis and endopod, as well as basal claw, unguiculate.

Maxilliped ( Fig. 5B ) four-segmented, composed of syncoxa, basis and two-segmented endopod. Ornamentation consisting of three rows of long and slender spinules on basis (two on posterior surface close to outer margin and one on anterior surface close to inner margin), as well as one row of two smaller spinules on anterior surface of first endopodal segment. Armature formula: 2.2.1.3. All setae, except two on second endopodal segment, pinnate, and most very strong and unguiculate.

All swimming legs ( Figs. 5C, D , 6 A-C) relatively large, composed of minute and triangular praecoxa, large and rectangular coxa, short basis, three-segmented exopod and two-segmented endopod. Endopods slightly shorter than exopods. Third exopodal segment spine formula 2. 3.3.3 and setal formula 4.4.4.4. All setae on endopods and exopods slender and plumose, except apical seta on exopod of first leg, which pinnate along outer margin and plumose along inner ( Fig. 5C ); no modified setae observ- ed. All spines strong and bipinnate. Intercoxal sclerite of all swimming legs with slightly concave distal margin and without any surface ornamentation, except on posterior surface of fourth leg.

First swimming leg ( Fig. 5C ) slightly shorter than other swimming legs; praecoxa unarmed, ornamented with distal row of small spinules on anterior surface; coxa 2.3 times as wide as long, ornamented with short transverse row of spinules on posterior surface close to outer margin, distal row of minute spinules on anterior surface, and small pore on anterior surface close to inner margin, arm- ed with long and plumose seta on inner-distal corner; basis almost pentagonal in shape, 0.8 times as long as coxa, armed with outer long and slender seta, and inner-distal strong and bipinnate element (latter not reaching distal margin of first endopodal segment in length), ornamented with row of slender spinules along inner margin, two posterior rows of shorter and stronger spinules on anterior surface (one at base of inner seta, other at base of endopod), and one cuticular pore on anterior surface close to outer margin; exopod with single outer spine and single inner seta on first and second segment, with two outer spines and four setae (two inner, two apical) on third segment, ornamented with distal rows of spinules on posterior surface of first segment, row of slender inner spinules on first and second segment, single small pore on anterior surface of second and third segments, and extremely minute spinules as base of almost all setae and spines on anterior surface; endopod armed only with inner seta on first segment, second segment with four inner setae, one apical spine, and one outer seta, ornamented with slender spinules along inner margins of both segments, single pore on anterior surface of second segment, with shorter and stronger spinules along distal margins of first segment on anterior surface, and minute spinules at base of most setae and apical spine on anterior surface; apical spine on second endopodal segment outwardly unguiculate, 0.9 times as long as segment and only slightly shorter than inner setae; second endopodal segment about 1.4 times as long as wide and 1.3 times as long as first endopodal segment, with small inner notch showing ancestral segmentation.

Second swimming leg ( Fig. 5D ) slightly larger than first swimming leg; coxa 2.3 times as wide as long, armed with plumose inner seta (shorter than in first leg), ornamented with short row of strong spinules on posterior surface, in addition to distal row of spinules and small pore on anterior surface; basis with much shorter outer seta than in first leg, and without inner seta, with very small spiniform process instaed; exopod with longer third segment than in first leg, with three outer spines; endopod with longer second segment than in first leg; apical spine on second endopodal segment 0.8 times as long as segment or distal inner seta; second endopodal segment about 1.7 times as long as wide and 1.5 times as long as first endopodal segment.

Third swimming leg ( Fig. 6A ) extremely similar to second leg, except second endopodal segment with five inner setae and apical spine proportionately shorter; apical spine on second endopodal segment 0.7 times as long as segment and 0.5 times as long as apical seta; second endopodal segment about 1.9 times as long as wide and 1.6 times as long as first endopodal segment.

Fourth swimming leg ( Fig. 6B, C ), generally similar to third swimming leg, but slightly shorter and more slender, with longer and more plumose setae, with transverse row of long spinules on posterior surface of intercoxal sclerite and another one on posterior margin of coxa, and with second enopodal segment armed with three or four inner setae, two apical spines and one outer seta; second endopodal segment without notch on inner margin, with two pores on anterior surface, about 1.6 times as long as wide, and also 1.6 times as long as first endopodal segment; inner apical spine on second endopodal segment 1.4 times as long as outer apical spine, 0.65 times as long as segment, and less than 0.4 times as long as distal inner seta.

Fifth leg ( Figs. 3A, B , 6D ) inserted ventro-laterally, relatively small, two-segmented. First segment (possibly protopod) broad and short, almost rhomboidal in shape, half as long as greatest width, ornamented with single pore on anterior surface close to proximal margin, armed with single outer slender seta (probably ancestral outer basal), which inserted on short setophore and unipinnate distally. Second segment (probably exopod) irregularly cylindrical, widest at midlength, 1.2 times as long as first segment and 1.7 times as long as wide, unornamented, armed with apical long seta and subapical inner spine; apical exopodal seta bipinnate distally, 1.4 times as long as basal seta, 4.6 times as long as exopod, and nearly ten times as long as subapical spine, but only reaching midlength of genital double-somite in length; subapical exopodal spine small and slender, smooth, half as long as exopod and 0.8 times as long as exopod’s greatest width.

Sixth leg ( Figs. 6E ) small, short and broad semicircular cuticular plate, armed with two short and smooth spines and outermost much longer and distally unipinnate seta; inner spine fused to plate, outer articulated basally; outermost seta directed postero-dorsally.

Male (based on allotype and one paratype). Total body length from 640 to 663 µm. Urosome with free genital somite. Habitus ( Figs. 7A ) much more slender than in female, with prosome/urosome ratio about 1.35 and greatest width in dorsal view at second pedigerous somite. Body length/width ratio 3.3; cephalothorax about 1.9 times as wide as genital somite. Cephalothorax 1.1 times as long as wide (dorsal view); representing 32% of total body length. Ornamentation of cephalothorax and free prosomites ( Fig. 7A ) and most urosomites ( Figs. 7A, B ) with same number and distribution of sensilla and pores as in female. Unpaired dorsal pore on genital somite (no. 101) situated more posteriorly than dorsal pair of sensilla no. 102 (more anteriorly in female); ventral pair of pores on fourth urosomite (no. 114) situated closer to each other.

Genital somite ( Fig. 7A, B ) 1.75 times as wide as long in dorsal view, with finely serrated hyaline fringe dorsally, ornamented with one unpaired dorsal pore (no. 101) and two pairs of dorsal sensilla (nos. 102, 103); no spermatophores visible inside; pair of pores on sixth legs probably homologous to lateral central pores on female genital double-somite (no. 104). Third urosomite homologous to posterior part of female genital double-somite, also ornamented with two pairs of posterior sensilla (nos. 106, 108) and two pairs of posterior ventral pores (nos. 107, 109). Fourth and fifth urosomite as in female. Anal somite ( Fig. 7A, B ) as in female, except anal operculum slightly narrower and more convex.

Caudal rami ( Fig. 7 B-D) slightly more slender than in female and with proportionately longer outermost terminal setae, but with very similar ornamentation and armature as in female; outermost terminal seta about nearly twice as long as innermost terminal seta, and only slightly shorter than ramus.

Antennula ( Figs. 6F , 8 B-D) strongly prehensile and digeniculate, 17-segmented (but sixteenth and seventeenth segments partly fused on ventral side), ornamented with spinules only on first segment (as in female), with anvilshaped structures on anterior margin of fourteenth and fifteenth segments (distal geniculation). Armature formula as follows: 8+3ae.4.2.2+ae.2.2.2.2.2+ae.2.2.2.2+ae. 2.1+ae.4.8+ae. All aesthetascs linguiform and most relatively long and broad, apical one on seventeenth segment fused basally to one seta; most setae slender and smooth; short smooth setae on eighth (one), ninth (one), tenth (one), twelfth (two), and thirteenth (two) segments; shot pinnate elements on eleventh (one) and fourteenth (one) segments; several seta on seventeenth segment biarticulate distally or with breaking plane.

Antenna, labrum, mandibula, maxillula, maxilla, first swimming leg, second swimming leg, and third swimming leg as in female.

Fourth swimming leg ( Fig. 7E ) also with similar armature and ornamentation as in female, as well as with similar proportions of spines and setae, except second endopodal segment with four inner setae (instead of three), and two proximal ones shorter, more slender and more sparsely plumose; second endopodal segment more slen- der than in female, about twice as long as wide.

Fifth leg ( Fig. 7B ) similar to female, but with slightly shorter apical exopodal seta.

Sixth leg ( Fig. 7F ) large cuticular plate, ornamented with single pore (probably no. 104) on anterior surface, armed with inner spine and two setae on outer distal corner; outermost seta 2.7 times as long as inner seta and 5.5 times as long as innermost spine.

Figures

Fig. 1. Monchenkocyclops changi gen. et sp. nov., holotype female: A. habitus, dorsal view. B. antennula, dorsal view. Arabic numerals indicating sensilla and pores consecutively from anterior to posterior end of body, and from dorsal to ventral side (excluding appendages; those on cephalothorax not presented). Scale bars 100 µm.

Fig. 2. Monchenkocyclops changi gen. et sp. nov., holotype female: A. cephalothoracic shield, lateral view. B. cephalothorax, dorsal view. C. pleurons of free prosomites, lateral view. D. rostrum, dissected and flattened, original anterior view. E. pleuron of second free prosomite (third pedigerous somite), dissected and flattened. Arabic numerals indicating sensilla and pores consecutively from anterior to posterior end of body, and from dorsal to ventral side (excluding appendages). Scale bars 100 µm.

Fig. 3. Monchenkocyclops changi gen. et sp. nov., holotype female: A. urosome, ventral view. B. urosome, lateral view. Arabic numerals indicating sensilla and pores consecutively from anterior to posterior end of body, and from dorsal to ventral side (excluding appendages). Scale bars 100 µm.

Fig. 4. Monchenkocyclops changi gen. et sp. nov., A-E. holotype female. F. paratype female. A. urosome, dorsal view. B. antenna, dorsal view. C. labrum, anterior view. D. maxillula, posterior view. E. mandibula, anterior view. F. cutting edge of labrum, anterior view. Arabic numerals indicating sensilla and pores consecutively from anterior to posterior end of body, and from dorsal to ventral side (excluding appendages). Scale bars 100 µm.

Fig. 5. Monchenkocyclops changi gen. et sp. nov., holotype female: A. maxilla, anterior view. B. maxilliped, posterior view. C. first swimming leg, anterior view. D. second swimming leg, anterior view. Scale bar 100 µm.

Fig. 6. Monchenkocyclops changi gen. et sp. nov., A-E. holotype female. F. allotype male. A. second endopodal segment of third swimming leg, anterior view. B. left fourth swimming leg, anterior view. C. second endopodal segment of right fourth swimming leg, anterior view. D. fifth leg, anterior view. E. sixth leg, lateral view. Scale bar 100 µm.

Fig. 7. Monchenkocyclops changi gen. et sp. nov., allotype male. A. habitus, dorsal view. B. urosome, ventral view. C. right caudal ramus, dorsal view. D. right caudal ramus, lateral view. E. second endopodal segment of fourth swimming leg, anterior view. F. sixth leg, ventrolateral view. Arabic numerals indicating sensilla and pores consecutively from anterior to posterior end of body, and from dorsal to ventral side(excluding appendages). Scale bars 100 µm.

Fig. 8. Scanning electron micrographs of Monchenkocyclops changi gen. et sp. nov., A. paratype female. B-D. paratype male: A. anal somite and caudal rami, dorsal view (most caudal setae broken off). B. proximal part of antennula, dorsal view. C. middle part of antennula, dorsal view. D. distal part of antennula, dorsal view. Scale bars 40 µm (A-C) and 20 µm(D).