Since the year 2009, the National Institute of Biological Resources of Korea (NIBR) has been conducting an international cooperative project of “Korean-Cambodian Joint Field Survey and Biodiversity Inventory Project” with the Forestry Administration of Cambodia. Professor Hyosig Won of Daegu University, Korea has engaged in the project, and he thankfully made a zooplankton collection for us in June, 2010. One of the sampling bottles he gave us included enough specimens for confirmation of a new species of
The cyclopoid copepod fauna of Cambodia is very poor, “even when compared to its neighboring countries”, and this country remains as “one of the least explored area in Southeast Asia”; the information on the taxonomic studies of cyclopoid copepods is rather scarce and fragmentary in Cambodia (for details of history of cyclopoid taxonomy in Cambodia, see Chaicharoen et al., 2011). Recently, two reliable studies on the cyclopoid taxonomy have been accomplished in Cambodia: Ishida and Tomikawa (2007) reported a single species,
In this study, we describe a new cyclopoid species of the genus
Samples were taken from a temporary pool (11°13ʹ18.1ʺN, 103°50ʹ30.6ʺE; 197 m in altitude) at a secondary forest along the trail to the newly built hydrodam situated in Mt. Phnum Domnak Dambouk, Koh Kong Province, Cambodia.
Copepods were collected with a hand net of 64 μm mesh aperture, and immediately fixed in the field by adding a few drops of saturated formalin. In the laboratory, the specimens were isolated from the samples under a zoom-stereomicroscope (Olympus SZX 12, Tokyo, Japan) at high magnifications (32-90×) with a micropipette, and transferred to about 80% ethanol for long-term preservation.
Methods for dissection, double-coverglass preparation using H-S slides (see Shirayama et al., 1993), drawings and measurements followed those in the latest paper for cyclopoid copepods of the junior author (Chang, 2012).
Type specimens are deposited in the National Institute of Biological Resources (NIBR), Incheon, Korea, and the specimen room of the Department of Biological Science, Daegu University (DB), Korea.
General terminology for the morphological description of the new species follows Huys and Boxshall (1991). Abbreviations are used in the text and figure legends, following those in Tran and Chang (2013): enp-1 to enp-2 or exp-1 to exp-2, the first to second endopodal or exopodal segments of each leg; P1-P6, first to sixth legs.
Order Cyclopoida Burmeister, 1835
Family Cyclopidae Rafinesque, 1815
Subfamily Cyclopinae Rafinesque, 1815
[Fig. 4.] Metacyclops woni, male (paratype, DB20055): A, Habitus, dorsal; B, Anal somite and caudal rami, dorsal; C, Antennule; D, P5, P6 and genital somite, ventral. Scale bars=100 μm (A), 50 μm (B-D).
Type locality. A small temporary pool (11°13ʹ18.1ʺN, 103°50ʹ30.6ʺE; 197 m in altitude; about 3 m×2 m wide, not more than 30 cm in depth) at a secondary forest near a hydrodam in Mt. Phnum Domnak Dambouk, Koh Kong Province, southwestern Cambodia.
Material examined. Holotype ♀ (NIBRIV0000324248), allotype ♂ (NIBRIV0000324249), both undissected, ethanolpreserved; from the type locality, 24 Jun 2010 (
Description. Female: Body (Fig. 1A) dark gray in ethanol; habitus of holotype 693 μm long (ranging 684-693 μm, mean 687 μm, n=3), length/width ratio 2.62. Prosome-urosome boundary distinctly defined between fourth and fifth pedigerous somites; prosome/urosome length ratio about 1.9; cephalothorax 2.34 times as wide as genital double-somite. Dorsal surfaces of prosomites and urosomites ornamented with innumerable pits and minute hairs.
Prosome comprising cephalothorax incorporating first pedigerous somite and 3 free pedigerous somites; elongate, oval, slightly protruding anteriorly; greatest width at posterior end of cephalothorax. Cephalothorax nearly as long as wide, or slightly longer than wide (length/width ratio 1.05), representing about 40.5% of total body length; posterior lateral angle not strongly produced; 2 pairs of sensilla present dorsally on posterior margin. Nauplius eye not discernible. Pedigerous somites 2-4 with narrow and elongate posterior lateral angle. Posterior margins of prosomites nearly smooth, except for second pedigerous somite with minute undulating fringe; paired minute sensilla situated middorsally on posterior margin of fourth pedigerous somite.
Urosomites ornamented with irregularly crenate hyaline fringe along posterior margin both dorsally and ventrally, except for nearly smooth one of fifth pedigerous somite and anal somite with spinule row. On fifth pedigerous somite, lateral basal seta of P5 issuing subdorsally; paired sensilla present middorsally. Genital double-somite slightly wider than long (about 1.1 times as wide as long); anterior third swollen laterally, with dorsolateral cuticular wrinkles bearing one seta and one small cuticular projection, representing P6; posterior margin with serrated hyaline fringe both dorsally and ventrally. Seminal receptacle showing typical shape of
Caudal rami (Fig. 1B) cylindrical, nearly parallel, stout, about 2.5 times as long as wide (ranging 2.45-2.53, n=3); greatest width at base of caudal ramus, slightly narrowing posteriorly. Coarse pits scattered on dorsal surface; 4 transverse rows of pits on ventral surface. Inner margins smooth; outer margin interrupted by 3 spinule groups, comprising 3 spinules on anterior third of lateral margin, 2-3 spinules at base of lateral caudal seta and 7-8 spinules at base of outer caudal seta. Lateral seta II short, plumose, inserted slightly dorsally near anterior two-thirds (65.5%) of caudal ramus. Outer seta III homogeneously plumose (not spiniform nor pinnate). Terminal setae IV and V well developed, plumose, with breaking plane; outer terminal seta IV about 2/3 times as long as inner terminal seta V, about 6 times as long as caudal ramus. Inner seta VI plumose, 0.84 times as long as caudal rami, about 0.83 times as long as outer seta III. Dorsal seta VII short, plumose distally, about 0.6 times as long as caudal ramus, issuing from inner distal corner of caudal ramus.
Antennule (Figs. 1A, 2A) short, not reaching to halfway of cephalothorax, 11-segmented; numerous pits scattered on surface. Segments 1, 3, 7 and 8 stout and long; segments 2, 4, 5 and 9 relatively short; relative length ratio of antennular segments 11.7 : 2.7 : 4.7 : 2.3 : 1.0 : 3.3 : 6.2 : 5.7 : 3.3 : 4.0 : 5.0. Segments 1, 3, 7 and segments 9-11 bearing both plumose and naked setae. Segment 1 armed with 1 oblique spinule row anteroproximally. Segment 5 with short, robust, spiniform seta anterodistally. Segment 8 with 1 long, slender aesthetasc, slightly extending over middle of next segment. Segment 11 with 1 long aesthetasc apically. Setal formula: 1-, 2-, 3-, 4-, 5-[1+1 spine], 6-, 7-, 8-[2+1 aesthetasc], 9-, 10-, 11-[7+1 aesthetasc].
Antenna (Fig. 2B) 4-segmented, comprising coxobasis and 3-segmented endopod. Coxobasis about twice as long as wide, about 15-16 spinules longitudinally along lateral margin; with 1 long pinnate seta outer distally, representing exopod. Enp-1 about 1.4 times as long as wide; with 1 inner naked seta; outer margin swollen, with 1 spinule row; enp- 2 about 1.4 times as long as wide, with spinule row outer distally, armed with 6 naked setae along inner margin, and 1 stout geniculate and 1 naked setae distally; enp-3 about 2.4 times as long as wide, bearing 7 geniculate setae apically, armed with spinule row along outer margin.
Mandible (Fig. 2C) with well developed coxal gnathobase; cutting edge armed with 10-11 strong teeth along distal margin, including 2 bidentate teeth, flanking 1 row of 5 sharp spinules and 1 outer subapical pinnate seta. Mandibular palp reduced to small protuberance, bearing 2 long plumose and 1 small naked setae distally or subdistally.
Maxillule (Fig. 2D) comprising well developed praecoxa and 2-segmented palp. Praecoxa bearing 7 elements along inner face, consisting of 3 small and 1 long naked setae, 1 strong pinnate seta, 1 spine and 1 posteriormost small spinous projection. Praecoxal arthrite armed with 4 strong dentate spines inner distally, consisting of 3 dentate spines basally fused together and 1 separated posteriormost spinous spine; 7 elements along inner margin, proximal pinnate seta longest, others naked. Palp consisting of coxobasis and endopod; coxobasis armed with 3 setae distally on basal endite (2 slender pinnate setae and 1 strong spinous seta); endopod 1-segmented with 2 apical and 1 inner setae; exopod represented by 1 long pinnate seta on outer margin of coxobasis.
Maxilla (Fig. 2E) 5-segmented (praecoxa and coxa partly fused in frontal view). Praecoxa with small proximal endite bearing 1 pinnate and 1 plumose setae apically; distal endite reduced to rounded protuberance, unarmed. Coxa with 2 coxal endites; proximal endite represented by 1 naked seta; distal endite highly mobile, armed with 1 apical spinous element with 3-4 secondary setules along its posterior margin and 1 shorter, unipinnate seta. Basis forming a claw with 5 strong spinules on posterior margin, flanking 1 slender, naked seta basally; 1 curved, pectinate, spinous element inserted at base of distal claw, slightly shorter than claw. Enp-1 with 2 strong, spinous seta on inner margin. Enp-2 small, narrowing distally, with 1 unipectinate apical and 2 naked subapical setae.
Maxilliped (Fig. 2F) 4-segmented, composed of syncoxa, basis and 2-segmented endopod. Syncoxal endite with 2 pinnate and 1 naked setae inner distally; frontal face ornamented with 5-6 oblique rows of minute spinules. Basis bearing 2 pinnate setae inner distally, with curved array of spinules near inner proximal margin and 1 group of sharp spinules at outer distal corner. Enp-1 armed with 1 long and stout seta, pinnate proximally and unipectinate distally. Enp-2 small, with 3 setae (1 lateral and 2 apical).
P1-P4 (Fig. 3A-D), both rami 2-segmented, with pits scattered irregularly on surfaces of enp-2 and exp-2. Setal formula (setal arrangement of exp-2 of P1-P4) 5,5,5,5. Spine formula (arrangement of spines on exp-2 of P1-P4) 3,4,4,3. Seta/spine armature of P1-P4 as follows:
P1 (Fig. 3A), intercoxal sclerite with paired lateral lobes produced posteriorly, with 5-6 spinules on inner distal margin; both frontal and caudal surfaces smooth without transverse spinule or setule row. Coxa with transverse row of 7-8 spinules on outer posterior margin; 1 plumose seta present inner distally. Basis armed with 1 pinnate seta distomedially, its tip nearly reaching to middle of enp-2; lateral seta well developed, plumose. Inner seta present on both enp-1 and exp-1; enp-2 bearing 4 plumose setae along inner margin, not modified to pinnate or spinous form.
P2-P3 (Fig. 3B, C), paired lateral lobes of intercoxal sclerite with 5-6 spinules along posterior margin; lateral seta on basis very short, plumose distally; inner seta present on both enp-1 and exp-1; enp-2 bearing 5 plumose setae along inner margin, not modified to pinnate or spinous form.
P4 (Fig. 3D), intercoxal sclerite with paired lateral lobes weakly produced posteriorly, with 5-6 spinules on inner distal margin; caudal surface with undulating row of 18-20 spinules along posterior margin. Coxa with transverse row of 14-16 sharp spinules along posterior margin; 1 inner distal seta well developed, plumose. Basis, lateral seta very short, plumose. Enp-1 with 1 inner distal seta; exp-1 lacking inner seta. P4 enp-2 elongate, 1.62 times as long as wide; armed with single spine apically, slightly shorter than enp-2 (about 0.8 times as long as enp-2); outer distal seta far exceeding beyond tip of apical spine.
P5 (Fig. 1C), protopodal segment completely incorporated into fifth pedigerous somite, with outer basal seta, situated rather dorsolaterally and flanking 6-7 spinules at its base; free exopodal segment very small, subquadrate, about 1.3 times as long as wide, bearing 1 spine inner subapically and 1 outer apical plumose seta; spine slightly shorter than exopod; outer apical seta about 5.6 times longer than inner spine.
Male: Body (Fig. 4A) 641 μm in length (ranging 632-641 μm, n=2), shorter and slenderer than females (length/width ratio 3.28), greatest width at posterior end of cephalothorax; length ratio of prosome to urosome 1.65. Prosome elongateoval. Cephalothorax slightly longer than wide, 0.3 times as long as body.
Genital somite (Fig. 4D) slightly swollen laterally, 1.42 times wider than long; genital pore located midventrally, large, transversely elongate. Paired genital opercula well developed, ornamented with numerous pits; distolateral corner produced to small protuberance, armed with 1 stout inner spine and 1 short plumose seta, representing P6.
Caudal rami (Fig. 4B) nearly parallel, slightly shorter than those of female, about 2.2 times as long as wide. Coarse pits scattered on dorsal surface; 4 transverse rows of pits on ventral surface. Longitudinal cuticular ridge running along lateral margin from just inside lateral seta II to basis of outer seta III. Inner margins smooth; 1 transverse spinule row situated at anterior quarter of lateral margin. Lateral seta II plumose, inserted slightly dorsally near anterior two-thirds (63%) of caudal ramus. Outer seta III plumose, about 1.2 times as long as ramus. Terminal setae IV and V well developed, plumose, with breaking plane. Inner seta VI plumose, slightly longer than ramus. Dorsal seta VII short, about 0.87 times as long as ramus.
Antennule (Fig. 4C) 16-segmented, relatively longer than in female; dorsal surface ornamented with numerous pits; geniculate between segments 8-10, and between segments 14 and 15; segments 4, 5, 6 and 9 relatively short; segments 14, 15 and 16 elongate; segment 11 large and swollen; segment 1 bearing 3 long aesthetascs, segments 4, 9, 13 and 16 each bearing 1 slender aesthetasc; segment 9 armed with strong cuspid-like spine anterodistally; segments 11 and 12 each with 1 pinnate seta anteriorly. Setal formula: 1-[8+3 aesthetascs], 2-, 3-, 4-[2+1 aesthetasc], 5-, 6-, 7-, 8-, 9-[1+1 aesthetasc], 10-, 11-, 12-, 13- [1+1 aesthetasc], 14-, 15-, 16-[12+1 aesthetasc].
Other characters of mouthparts and P1-P5 nearly same as those of female.
Etymology. The specific name
Remarks. This new species is manifestly assigned as a member of the genus
Members of the genus are classified into four groups, based on the spine formula, that is, the spine armature on the terminal exopodal segments of P1-P4 (see Herbst, 1988; Reid, 1991; Karanovic, 2004). Among the groups, the absolute majority of members (54 of 62 species recognized in this genus) belong to the group with 3,4,4,3 formula, as well as the new species does.
The new species is distinguishable from the most species of the species group with spine formula 3,4,4,3 by the character combination of 11-segmented antennule and a single apical spine on P4 enp-2, sharing the characters with 12 species of the group:
Among the members of the species group with the combination of characters of 11-segmented antennule and a single apical spine on P4 enp-2,
In Asia, eight species of