Halicyclops lanceolatus, Chang & Lee, 2012

Chang, Cheon Young & Lee, Jimin, 2012, Two new species of Halicyclops (Copepoda, Cyclopoida) from the estuarine interstitial waters in South Korea *, Zootaxa 3368 (1), pp. 197-210 : 199-205

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https://doi.org/ 10.11646/zootaxa.3368.1.9

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scientific name

Halicyclops lanceolatus

sp. nov.

Halicyclops lanceolatus sp. nov.

( Figs 2 View FIGURE 2 –4)

Type locality. Springs (0.5–1 m deep, sandy bottom on basalt rocks) in Jaeamcheon-gul Cave and a small ditch originating from the cavern springs and discharging into Hyeopjae Beach, Jeju Island, South Korea, 33°23′28.73″N 126°14′19.28″E GoogleMaps .

Type material. Holotype, intact female in alcohol (NIBRINV0000245091). Allotype, intact male in alcohol (NIBRINV0000245092). Paratypes: two dissected females (DB20036, 20037), one dissected male (DB20038); nine females in alcohol. All collected at the type locality, 2 March 2010, leg. J.M. Lee.

Additional material examined. Three females from a sandy dune at the estuary of Wangpicheon River, Uljin, South Korea, 36°58′10″N 129°24′40″E, 26 July 2010, legs. C.Y. Chang & J.M. Lee GoogleMaps .

Etymology. The specific name is a Latin adjective lanceolatus , meaning lanceolate, spear-like, which refers to the stout, lanceolate spines with broad blades of P1–P5, especially the inner apical on P5 exopod.

Description. Female. Body ( Fig. 2A View FIGURE 2 ) relatively small, about 580 µm long, measured from anterior margin of cephalothorax to posterior margin of Fu, excluding caudal setae; maximum width at posterior end of cephalothorax, about 210 µm; L/ W 2.8. Body slightly flattened dorsoventrally. Prosome comprising cephalothorax incorporating first pedigerous somite and 3 free pedigerous somites; posterior margins of prosomites nearly smooth, except for serrated outer posterior margins of second and third prosomites. Cephalothorax not strongly protruded anteriorly; nearly as long as wide; ovoid integumental window (or median depression) present middorsally; about 40 or more sensilla scattered on dorsal and lateral surfaces. Rostrum completely fused to cephalothorax; rostral expansion rarely visible from dorsal view. Fifth pedigerous somite incorporating basis and endopod of P5, bearing an outer basal seta on posterior corner of dorsal surface. Genital double-somite ( Fig. 2B View FIGURE 2 ) slightly wider than long (L/ W 0.96, at level of lateral expansion); lateral sides weakly expanded laterally, with its tip only pointed posteriorly; in dorsal view, sclerotized wrinkles ahead lateral expansion, armed with 3 appendages representing P6; genital area simple, with a big median copulatory pore; paired spermatophores attached on copulatory pore small, ovoid; with paired cuticular recesses ventrolaterally at posterior half of genital doublesomite. Pseudoperculum of preanal somite ( Fig. 2B View FIGURE 2 ) protruding posteriorly, with 11–12 strong teeth along posterior margin, extending slightly over anal operculum ( Fig. 2B View FIGURE 2 ).

Fu ( Fig. 2B View FIGURE 2 ) about 1.1 times longer than wide; nearly parallel to each other; armed with spinules at outer distal margin of ramus and near base of outer caudal seta; with 6 caudal setae, lacking seta I. Lateral caudal seta arising from proximal quarter a little dorsally. Inner caudal seta minute, 0.5 times as long as ramus. Outer caudal seta about 1.6 times longer than ramus. Dorsal caudal seta arising from shallow protuberance, 2.6 times longer than ramus. Small cuticular tube with a minute pore present outside the protuberance. Both inner and outer terminal caudal setae with breaking planes; outer terminal caudal seta ornamented heterogeneously on its outer margin: distal half of outer margin setulose, distal half of inner margin plumose.

A1 ( Fig. 3A View FIGURE 3 ) slightly not reaching to halfway of cephalothorax; 6-segmented. Fourth segment twice longer than wide; last segment about 2.9 times longer than wide. Aesthetasc each arising from fourth and last segment distally. Setal formula: 8, 12, 5 (+ 1 spine), 6 (+ 1 aesthetasc), 2, 10 (+ 1 aesthetasc).

A2 ( Fig. 3B View FIGURE 3 ) 3-segmented, comprising coxobasis and 2-segmented endopod. Coxobasis armed with 2 inner distal setae, and 1 outer distal seta representing exopod. First endopodal segment bearing 1 pinnate inner seta, with smooth margins lacking spinules. Second endopodal segment elongate, 2.9 times as long as wide, about 1.6 times longer than first endopodal segment; ornamented with 1 setule row along outer edge; armed with 5 lateral and 7 apical setae.

Mandible ( Fig. 3C View FIGURE 3 ) with well-developed coxal gnathobase, armed with 10–11 teeth including outermost pinnate spine, flanking 1 outer distal pinnate seta. Palp very reduced, represented by 2 naked setae on small protuberance, of which shorter one small, about 1/3 times as long as longer one.

Maxillule ( Fig. 3D View FIGURE 3 ), praecoxal arthrite bearing 4 strong tooth-like spines distally; 7 elements with various shapes present along inner margin, including 1 proximalmost fanglike projection. Palp 2-segmented; coxobasis bearing 1 pinnate, 1 spiniform and 1 naked setae inner distally, plus 1 outer pinnate seta representing exopod; distal segment, representing endopod, armed with 3 stout setae.

Maxilla ( Fig. 3E View FIGURE 3 ) 4-segmented, comprising praecoxa, coxa, basis and 1-segmented endopod. Praecoxal endite with 1 pinnate and 1 plumose setae. Coxa with 1 naked seta representing proximal endite; distal endite movable, forming 1 bisetose lobe completely fused with naked seta proximally. Basis forming 2 strong claw-like spines with 1 naked seta between them basally. Endopod carrying 5 elements of 2 claw-like spines, 1 naked spiniform setae and 2 minute slender setae.

Maxilliped ( Fig. 3F View FIGURE 3 ) 2-segmented, comprising protopod and completely defined endopod; protopod about 2.3 times longer than endopod. Protopod with 2 spiniform setae proximally and 1 bisetose seta distally, representing endites; 1 setule row present on outer distal corner of protopod. Endopod bearing 5 setae in total, comprising 2 inner setae, 1 apical, 2 outer subapical pinnate setae.

P1–P4 (Figs. 4A–D) biramous, both rami 3-segmented. Coxal setae pinnate. Spine formula of 3,4,4,3. Seta/ spine armature of P1–P4 as follows:

P1 coxa 0-1 basis 1-1 exp I-1; I-1; III,1,4 enp 0-1; 0-2; II,1,3

P2 coxa 0-1 basis 1-0 exp I-1; I-1; IV,1,4 enp 0-1; 0-2; II,I,3

P3 coxa 0-1 basis 1-0 exp I-1; I-1; IV,1,4 enp 0-1; 0-2; II,I,3

P4 coxa 0-1 basis 1-0 exp I-1; I-1; III,1,4 enp 0-1; 0-2; II,I,2

P1 (Fig. 4A), intercoxal sclerite with 1 row of long hairs and 1 setule row along distal margin of both lateral lobes; medial seta on P1 basis stout, ornamented with long setules proximally and secondary spinules distally, not reaching to poseterior end of enp2; two distal spines on exp3 not strikingly elongate, about 1.4 times longer than proximal one. P2–P4, intercoxal sclerites of P2–P3 with setules along distal margin of both lateral lobes, while lateral lobes of P4 lacking hairs or setules; enp2 with 2 inner setae; proximalmost seta on P2–P3 enp3 modified to spiniform; spines on enp3 and exp3 lanceolate with broad blades. P4 (Fig. 4D), enp3 about 1.4–1.5 times longer than wide; both inner setae spiniform; apical spine nearly same in length with enp3, and about 1.2 times longer than outer apical spine.

P5 ( Fig. 2C View FIGURE 2 ), basis and endopod completely incorporated to fifth pedigerous somite; basal seta inserted on small protuberance arising from dorsolateral corner of somite. Exopod not elongate, about 1.3 times longer than wide; inner margin nearly straight, ornamented with spinule rows; inner apical spine apparently long, its tip generally extending to posterior one-fifth of genital double-somite, 1.15 times longer than exopod, and 1.2 times longer than apical plumose seta; apical seta slightly shorter than exopod. P6 indistinct, represented by small genital operculum armed with 3 elements of 2 toothlike spines and 1 long seta.

Male. Body ( Fig. 2D View FIGURE 2 ) small, about 450 µm long. Fu ( Fig. 2D View FIGURE 2 ) nearly as long as wide, armed with spinules on outer distal corner and ahead of base of dorsal caudal seta. Small cuticular tube present outside the longitudinal protuberance, with a pore on its tip. Mid-dorsal hyaline fringe of preanal somite not heavily protruding posteriorly, with about 10 strong teeth along posterior margin, extending slightly over anal operculum. A1 13-segmented, strongly geniculate, with geniculation between segment 11 and segment 12. Setal formula: 8, 4, 4, 4, 4, 1, 1, 2, 2, 3, 1, 1, 11. Aesthetasc formula: 3, 0, 1, 0, 0, 1, 0, 1, 0, 1, 0, 1, 2. Segment 6 with 1 short, spiniform seta; segments 9–11 each bearing 1 short, strong, pinnate seta anterodistally.

Shape and armature of P1–P4 nearly same as in female, except for inner distal seta on P1 basis far exceeding over posterior end of enp2. P5 exopod ( Fig. 2E View FIGURE 2 ) not elongate, about 1.3 times longer than wide; medial margin straight and smooth, with 1 slender seta subdistally; inner apical spine strongly lanceolate, about 1.3 times longer than exopod, its tip reaching to middle of third urosomite (first abdominal somite). P6 ( Fig. 2D View FIGURE 2 ), innermost spine stout and long, its tip reaching to middle of fourth urosomite.

FIGURE 4. Halicyclops lanceolatus sp. nov., female. A, P1; B, P2; C, P3; D, P4. Scale: 50 µm.

Ecology. Type specimens were collected from two cavern springs near the exit of Jaeamcheon-gul Cave, a small cave belonging to the Hyeopjae lava tube system in Jeju Island, and from a small canal connecting the cave with Hyeopjae Beach. Both the springs and canal showed low salinity of 0.2–7.3 ‰, varying depending on tide and distance from the coast. This species was also collected from the estuary of Wangpicheon River, Uljin, about 3.5 km away from Seongryu Cave. Considering the environments of both collection sites, the minute body size, and small number (usually only four) of eggs in an egg sac, this species is supposedly related with cavern environment and/or genuine interstitial species.

Remarks. The genus Halicyclops is classified into seven morphological groups according to the spine formula of P1–P4 exp3 (see Pesce 2011). Among them, group B showing the spine formula of 3,4,4,3 is the most predominant, which currently comprises 68 species or subspecies ( Boxshall 2011). The thermophilus group is a subgroup of group B, which is characterized by the presence of a well developed chitinous spiniform process on each side of the genital double-somite ( Herbst 1983). In Korea, only one species is recorded as a member of the thermophilus group: H. japonicus Ito, 1965 (see Chang 2012).

As well summarized in Ueda & Nagai (2009), Karanovic (2008) considered H. spinifer Kiefer, 1935 from India as a junior synonym of H. thermophilus Kiefer, 1929 from Java, Indonesia, both of which had been insufficiently and inadequately described. Karanovic regarded the main morphological discrepancies between the two species, that is, the relative lengths of the lateral process on the genital double-somite and of the inner apical spine on the female P5, as an intraspecific variation among different geographical populations. His proposition extended to other species belonging to the thermophilus group, “which were generally created only by a difference in a single character, that is, the shape (spiniform or plumose) of the setae on the P4 enp 3 in H. japonicus and H. dedeckeri Brownell, 1983 , and the length of the inner apical spine on the P 5 in H. latus Shen & Tai, 1964 ” ( Ueda & Nagai 2009). However, Ueda & Nagai (2009) refuted Karanovic’s synonymization by arguing that the characters above as well as pseudoperculum (mid-dorsal hyaline membrane on the posterior margin of preanal somite) should be regarded as interspecific. Accordingly, the East Asian species should be recognized as valid species in the thermophilus group.

In comparison with the detailed redescription of H. thermophilus , the nominotypical species of the species group, by Karanovic (2008), H. lanceolatus sp. nov. resembles it with regards to a remarkably large inner apical spine on P5. Besides the shape and size of the lateral process on the genital double-somite (very short and laterally produced with strongly chitinized, tooth-like tip in H. lanceolatus , while very long and claw-like expansion produced posteriorly in H. thermophilus ), H. lanceolatus differs from H. thermophilus in the following: (1) cephalic window (or integumental depression) is present; (2) pseudoperculum comprises about 12 thick, serrate protrusions (versus 14–15 thin and sharp, spiniform protrusions in H. thermophilus ); (3) P4 enp3 is about 1.2 times longer than wide, with thick, lanceolate apical spines, of which the inner one is shorter than enp3 (versus more than 1.5 times as long as wide, with normal apical spines, of which the inner one is much longer than enp 3 in H. thermophilus ); (4) inner apical spine of P5 is apparently lanceolate, and longer than apical seta (versus the inner apical spine shorter than apical seta in H. thermophilus ); (5) A1 is armed with an aesthetasc on fifth segment (versus lacking in H. thermophilus ). Considering that the characters above are very important in meeting the species criteria in the cyclopoid classification, the discrepancies are significant enough for the two species to be regarded as distinct and valid ones. Thus, this new species reinforces Ueda & Nagai’s argument (2009) that the morphological differences (especially, in the lateral process on genital double-somite and inner apical spine of P5 exopod) between H. thermophilus and the species from East Asia are not resulted from intraspecific variations but from interspecific characters, and therefore, the East Asian species are distinct species. To summarize, the two species H. thermophilus Kiefer, 1929 and H. spinifer Kiefer, 1935 should be regarded as species inquirendae, and other subsequent records under the name of ‘ H. thermophilus ’ might be other distinct species.

Halicyclops lanceolatus is characteristic in having a stout, lanceolate inner apical spine on P5 exopod, as the specific name suggests. Besides this, H. lanceolatus differs from two Japanese species belonging to the thermophilus group, that is, H. japonicus Ito, 1956 and H. uncus Ueda & Nagai, 2009 , by the very short lateral process of genital double-somite, which produces laterally with strongly chitinized, tooth-like tip (versus short process with spiny tip in H. japonicus , and long and claw-like expansion produced posteriorly in H. uncus ), short caudal rami (about 1.2 times as long as wide, versus 1.8–2.0 in H. japonicus , and 1.5–1.7 in H. uncus ), short inner apical spine on P4 enp3 (shorter than enp3, versus much longer than enp 3 in H. japonicus and H. uncus ), and large inner apical spine of P5 (apparently lanceolate, and longer than P5 exopod as well as apical seta, versus much shorter than P5 exopod and apical seta in H. japonicus and H. uncus ) ( Ito 1956; Ueda & Nagai 2009).

Halicyclops lanceolatus resembles H. latus Shen & Tai, 1964 from China in possessing short lateral processes on genital double-somite ( Shen & Tai 1964). However, H. lanceolatus clearly differs from it by short Fu (about 1.2 times as long as wide, versus 1.7 in H. latus ), long and stout inner apical spine of P5 (apparently lanceolate, and much longer than P5 exopod, versus much shorter, less than half the length of P5 exopod in H. latus ), short inner apical spine on P4 enp3 (shorter than enp3, versus much longer than enp 3 in H. latus ), and well developed pseudoperculum (while lacking in H. latus ).

Halicyclops soqotranus Baribwegure & Dumont, 2000 from the Indian Ocean is similar to H. lanceolatus in having short lateral processes on genital double-somite and short Fu ( Baribwegure & Dumont 2000). However, it is distinguished from this new species by the seta/spine armature of P1–P4, that is, absence of inner seta on P1 basis, only 3 inner setae on P1 enp3, unmodified proximalmost inner seta on P2–P3, and unmodified inner setae on P4 enp3.

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