Pseudodiaptomus koreanus, Soh & Kwon & Lee & Yoon, 2012

Soh, Ho Young, Kwon, Sun Woo, Lee, Woncheol & Yoon, Yang Ho, 2012, A new Pseudodiaptomus (Copepoda, Calanoida) from Korea supported by molecular data, Zootaxa 3368 (1), pp. 229-244 : 231-238

publication ID	https://doi.org/ 10.11646/zootaxa.3368.1.11
publication LSID	lsid:zoobank.org:pub:277B73ED-7B22-45AC-8B38-CB6A0B2A9A7F
persistent identifier	https://treatment.plazi.org/id/F90487E5-FF88-FFC7-7ABD-F931FE3BF873
treatment provided by	Felipe
scientific name	Pseudodiaptomus koreanus
status	sp. nov.

Treatment

Pseudodiaptomus koreanus sp. nov.

( Figs. 2 View FIGURE 2 , 3A View FIGURE 3 , 4–8 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 )

Type material. Holotype female dissected and mounted on seven glass slides using CMC-10, aqueous mounting medium (Masters Company, Inc., Wood Dale, IL) ( NIBR0000245889 View Materials ); paratypes: one female and two males dissected and mounted on 18 glass slides ( NIBR0000245890 View Materials ) and undissected six females and seven males in alcohol ( NIBR0000245891 View Materials ); all collected from the Hyungsan River estuary (36 o 54’43.21”N 129 o 22’22.48”), eastern Korea by H.Y. Soh on 7 September 1997. Additional paratypes: undissected 20 females and 20 males in alcohol ( NIBR0000245892 View Materials ) from the Seomjin River estuary (35 o 04’45.45”N 127 o 43’22.08”E), southern Korea, collected by H.Y. Soh on 16 October 1999. GoogleMaps

Other materials examined. Undissected 20 females and 20 males in alcohol ( NIBR0000245893 View Materials ) from Beolgyo stream (34 o 50’31.14”N 127 o 21’10.38”E), southern Korea, collected by H. Y. Soh on 15 May 2008 GoogleMaps .

Description. Female. Body length 1.30-1.45 mm (mean±sd=1.36±0.03, n=6), with paired egg sacs. Prosome/ Urosome ca. 1.71. First pediger coalesced with cephalosome; second and third pedigers with row of fine spinules along posterolateral margins; fourth and fifth pedigers completely fused with rounded corners, posterolateral corner on each side with row of spinules and with small bump posteromedially ( Fig. 2A, B View FIGURE 2 ). Urosome of 4 free somites: genital double-somite, 1.1 times wider than long, greatest width anterior in dorsal view with several spinules on each anterolateral projection ( Fig. 2A View FIGURE 2 ). In ventral view posterolateral process of female lateral genital flaps, wide and extend well short of posterior border of genital double-somite ( Fig. 2C View FIGURE 2 ); pair of uncovered gonopores and rounded posteriorcentral projection between those ( Fig. 3A View FIGURE 3 , white arrowhead) located posteroventrally; anal somite shortest. Each somite except anal somite serrated along posterior margin. Caudal rami nearly symmetrical, with six setae; outer terminal seta IV basally swollen ( Fig. 2A View FIGURE 2 ).

Antennules symmetrical, 22-segmented ( Fig. 2D View FIGURE 2 ); ancestral segments II-VI and XXVI-XXVIII completely fused; segment X and XI incompletely fused with suture line; setal formula as follows: I-1+aesthetasc, II-VI- 3+aesthetasc, VII-2+aesthetasc, VIII-1+aesthetasc, IX-2+aesthetasc, X-1 (spinifom element), XI-2+aesthetasc, XII-2 (1 spiniform)+aesthetasc, XIII-2+aesthetasc, XIV-2+aesthetasc, XV-2+aesthetasc, XVI-2+aesthetasc, XVII- 2+aesthetasc, XVIII-2+aesthetasc, XIX-2, XX-2, XXI-2+aesthetasc, XXII-1, XXIII-1, XXIV-1+1, XXV- 1+1+aesthetasc, XXVI-XXVIII-6+aesthetasc.

Antenna ( Fig. 4A View FIGURE 4 ): coxa with single seta; basis and first endopod fused into allobasis, each having 2 setae, respectively; second endopod with 9 and 7 setae on subterminal and terminal lobes, respectively; exopod 6- segmented, with setation of 1, 5 1, 1, 1, 3.

Mandible ( Fig. 4B View FIGURE 4 ): basis with 4 setae; endopod 2-segmented, first segment with 4 setae, second having 9 setae armed with two lows of setules; exopod 5-segmented, first to fourth segments each with single seta, fifth segment with 2 setae.

Maxillule ( Fig. 4C View FIGURE 4 ): praecoxal arthrite with 15 elements; coxa with 4 setae on endite and 9 setae on epipodite; basis with 4 and 5 setae on proximal and distal endite, respectively, with single seta on exite; endopod 3- segmented, with setal formula 4, 4, 7; exopod unisegmented, with 11 setae.

Maxilla ( Fig. 4D View FIGURE 4 ): praecoxa elongated, proximal endite with 4 setae, distal endite with 3 setae; two coxal endites with 3 setae each; basis with sclerotized stout seta in addition to single short and 2 long setae; endopod 4- segmented with 2, 3, 2, 2, respectively.

Maxilliped ( Fig. 4E View FIGURE 4 ): syncoxa with setal fornular of 0, 2, 3, 4 on endites; basis bearing 3 setae, with first endopodal segment separated; endopod 6-segmented, with setal formula of 2, 3 (including 2 bifurcate setae), 2 (both bifurcate setae), 2, 2+1, 4.

Legs 1–4 ( Fig. 5 View FIGURE 5 , Fig.6A View FIGURE 6 ) each with 3-segmented endopodal segments; first and second endopodal segments of legs 1 to 4 with spinules on outer distal corner; terminal spines on third exopodal segment of legs 1 to 4 with row of hairs on inner margin and teeth on other border along distal 3/4 of medial margin.

Seta and spine formula as follows:

Coxa Basis Exopodal segmentEndopodal segment

Leg 1 0-1 0-0 I-1; 0-1; II, I, 3 0-1; 0-1; 1, 2, 3

Leg 2 0-1 0-0 I-1; I-1; II, I, 5 0-1; 0-2; 2, 2, 4

Leg 3 0-1 0-0 I-1; I-1; II, I, 5 0-1; 0-2; 2, 2, 4

Leg 4 0-1 1-0 I-1; I-1; II, I, 5 0-1; 0-2; 2, 2, 3

Fifth leg symmetrical, uniramous ( Fig. 6B View FIGURE 6 ): intercoxal sclerite completely incorporated into both coxae; basis with small posterior outer seta; exopod 3-segmented, first segment furnished with spinules on inner margin, with outer spine and mediodistal blunt projection; second and third segments incompletely fused, second segment with short outer spine and larger serrate inner spines, third segment with long terminal spine and smaller inner spine.

Male. Body length 1.09–1.19 mm (mean±sd=1.10±0.01, n=10). Cephalosome and first pediger, and fourth and fifth pedigers completely fused; first to fifth pediger with row of posterolateral spinules ( Fig. 7A, B View FIGURE 7 ). Urosome of 5 free somites: genital somite with genital opening on left; second urosomite with ventral transverse row of spinules ( Fig. 7C View FIGURE 7 ); genital and anal somites naked, second to fourth somites armed with posterodorsal spinules.

Left antennule same as in female. Right antennule 21-segmented, geniculated ( Fig. 8A View FIGURE 8 ); ancestral segments II to IV, XXII and XXIII, and XXIV and XXVIII completely fused; segments VIII and IX incompletely separated. Setation and segmentation as follows: I-1+aesthetasc, II-IV-3+aesthetasc, V-2+aesthetasc, VI-1, VII-2+aesthetasc, VIII-1, IX- 2+aesthetasc, X-1 (spiniform), XI-2+aesthetasc, XII-2 (1 spine)+aesthetasc, XIII-2+aesthetasc, XIV-2+aesthetasc, XV-2+aesthetasc, XVI-2+aesthetasc, XVII-2+aesthetasc, XVIII-2+aesthetasc, XIX-1+process+aesthetasc, XX- 1+process, XXI-1, XXII-XXIII-2+process, XXIV-XXVIII-9+2aesthetasc. Other appendages except for fifth leg nearly similar to those of female.

Fifth leg asymmetrical ( Fig.8B, C View FIGURE 8 ); coxa with spinule patch on both surfaces, left basis and endopod completely fused, produced into 2 large medial processes. In finger-shaped morph ( Fig. 8C View FIGURE 8 ) larger medial process of left basoendopodal segment curved, with patch of minute spinules at mid-length; proximal endopodal segment having inner seta proximally widest on central part; distal segment with 5 setae and serrated outer spine covered with hairs; right basis with outer seta and two unequal inner knobs; first exopodal segment with long stout distal outer spine and medial seta; second segment medially swollen with medial inner seta and spine; third segment elongate, with stout terminal spine, medial seta, and distal seta. In paddle-shape morph ( Fig. 8B View FIGURE 8 ) patch of minute spinules absence at mid-length of medial process of left basoendopodal segment; proximal exopodal segment with inner seta proximally widest on proximal part; distal segment covered with hairs with 3 setae and serrated outer spine; two unequal inner lobes absence on right basis; width of second exopodal segment nearly equal.

Remarks. Pseudodiaptomus koreanus sp. nov. is very closely related to P. inopinus Burckhardt, 1913 and P. nansei Sakaguchi and Ueda, 2010 . However, this new species differs from P. inopinus in having broad, short posterior processes of the female lateral genital flaps, a rounded posteriocentral projection between genital flaps (see Fig. 3A View FIGURE 3 ), the separation of ancestral segments XXI and XX–XXIII of the male right antennules, patch of minute spinules on medial process of basoendopodal segment of male left fifth leg, and longer proximal endopodal segment of male left fifth leg. Pseudodiaptomus koreanus has generally single inner seta on the fifth exopodal segment of its antenna, but the inner seta is absent in some specimens. Also, in finger-shaped morph of male left leg ( Fig. 8C View FIGURE 8 ) a larger medial process of male left basoendopodal segment has a patch of minute spinules at the midlength, but it is absent in some specimens. Pseudodiaptomus koreanus is distinguishable from P. nansei Sakaguchi and Ueda, 2010 by the presence of a row of fine spinules along the posterior margins of the second and third pedigers in both sexes, rounded posteromedial projection between both gonopores, the separation of ancestral segments XXI and XXII–XXIII of the male right antennule, and a row of fine ventral spinules on male second urosomite.

Pseudodiaptomus koreanus is a dominant species in salinity between 5 and 15, in estuarine waters of southeastern Korea in spring and autumn ( Park et al. 2005), while P. inopinus is restricted to western estuarine waters of Korea occurring at salinities <30 with P. popesia (Park 2005) . However, Chang (2009) showed that P. inopinus occurs widely in the inland waters of Korea.

Etymology. The specific name koreanus refers to the apparent centre of distribution for this species.

Molecular diversity. A 266 base pair region of the ITS1 was obtained for three individuals of Pseudodiaptomus inopinus collected from the western estuary and eight individuals of P. koreanus from the southeastern estuary of Korea. The ITS1 sequences differed by 12–14% between P. inopinus and P. koreanus sp. nov. ( Table 1), by 5–6% between the southern and eastern individuals of the new species, and by 1.2% between two morphs of the male fifth legs, respectively.

A 624 base pair region of the mtCOI gene was obtained for 19 individuals of P. koreanus from the southeastern estuaries of Korea including two male morphs (GenBank Accession No. JQ714036 View Materials - JQ714054 View Materials ), one individual of P. inopinus from the western estuary of Korea (GenBank Accession No. JQ714057 View Materials ), and two individuals of P. inopinus from the western Japan (GenBank Accession No. JQ714055 View Materials , JQ714056 View Materials ). The mtCOI sequences differed by 0.6–3.8% between individuals of P. koreanus including two male morphs. Meanwhile, the mtCOI sequences differed by 14.3–22.0% between P. koreanus and P. inopinus and by 19.6–20.7% between Korean and Japan populations of P. inopinus . The mtCOI tree shows that P. koreanus is clearly separated from P. inopinus ( Fig. 9 View FIGURE 9 ). The MtCOI reference sequences were selected to represent the new species from the southeastern estuaries of Korea (GenBank Accession No. JQ714037 View Materials ) and P. inopinus from the Mankyung River estuary (GenBank Accession No. AF536520 View Materials ).