Proserpinicaris imjin, Karanovic & Cho & Lee, 2012

Karanovic, Tomislav, Cho, Joo-Lae & Lee, Wonchoel, 2012, Redefinition of the parastenocaridid genus Proserpinicaris (Copepoda: Harpacticoida), with description of three new species from Korea, Journal of Natural History 46 (25 - 26), pp. 1573-1613 : 1597-1602

Proserpinicaris imjin sp. nov.

( Figures 10 , 11 )

Type locality

South Korea, Gyeonggido region , Paju city, Jeokseong town, Imjin river, interstitial water from sandy beaches, 37 ◦ 59 ′ 04.4 ′′ N, 126 ◦ 55 ′ 41.2 ′′ E .

Specimens examined

Types only: holotype male and allotype female together on one scanning electron microscopy stub (collection number NIBRIV0000232626); one paratype male in alcohol (NIBRIV0000232627); four paratypes from a different sample (two males and two females) dissected on one slide each (collection numbers NIBRIV0000232628 to 0000232631); six paratypes from a different sample (four males and two females) together in alcohol (NIBRIV0000232632); all collected from the type locality, 14 July 2010, leg. J.L. Cho, all deposited in the National Institute of Biological Resources , South Korea .

Etymology

The species name refers to its type locality, Imjin river, and should be treated as a noun in apposition to the generic name.

Description

Male (based on holotype and several paratypes). Total body length from 342 to 350 µm (342 µm in holotype). Colour, body segmentation, arthrodial membranes and sensilla pattern as in P. young sp. nov. (see above). Habitus ( Figure 10A ) cylindrical but not very slender, without any demarcation between prosome and urosome; prosome / urosome ratio 0.7; greatest width in dorsal view hard to establish. Body length / width ratio only about 7.2; cephalothorax about as wide as genital somite; free prosomites in lateral view about as wide as cephalothorax and not narrower than urosome, without any expansions laterally or dorsally. Hyaline fringe of all somites smooth, very narrow and hard to distinguish from arthrodial membranes, except in preanal somite dorsally and partly laterally. Integument very weakly sclerotized, much softer than in P. young or in P. wangpi sp. nov., without any spinules or cuticular pits (except several spinules on caudal rami), but with slightly wrinkled surface, ornamentated as in P. young and P. wangpi with 45 pairs of sensilla and four pairs pores (three on anal somite, and one on caudal rami), dorsally with round cuticular window on cephalothorax and oval cuticular windows on genital and three postgenital somites, all in same position and of similar size to those in P. young but not as well defined because of thin integument. Pleural areas of cephalothorax ( Figure 10A,B ) and free pedigerous somites ( Figure 10C,D ) not well developed, cephalic appendages and coxae of swimming legs clearly exposed in lateral view; rostrum and cuticular sutures of free pedigerous prosomites as in P. young .

Cephalothorax ( Figure 10A,B ) about 1.5 times as long as wide in dorsal view; representing 18 % of total body length.

Urosomites ( Figure 10A ) proportionately shorter and wider than in P. young or even P. wangpi , but without any difference in ornamentation. Anal somite ( Figures 10A , 11A,B ) about as long as preanal somite, i.e. proportionately shorter than in P. young and P. wangpi ; anal operculum clearly concave in dorsal view.

Spermatophore ( Figure 11C ) more slender than in P. young , about 2.4 times as long as wide.

Caudal rami ( Figures 10A , 11A,B ) from 3.2 to 3.6 times as long as greatest width and only about as long as anal somite, cylindrical in anterior part but slightly inflated in posterior part in lateral view (arrowed in Figure 11A ), nearly parallel, with space between them about 1.5 times one ramus width; armed with seven armature elements (three lateral, one dorsal and three apical). Ornamentation consists of large lateral cuticular pore near posterior margin, and posterior ventral row of two small spinules. Dorsal seta slender and smooth, inserted closer to inner margin at about fourfifths, about as long as caudal ramus, triarticulate. Lateral setae slender and smooth, inserted very close to each other at two-fifths of ramus length, minute one between two larger ones and slightly posterior to them. Anterior lateral seta inserted more dorsally, longest, 0.6 times as long as ramus, 1.3 times as long as other anterior seta, and about seven times as long as minute seta. Inner apical seta smooth, inserted close to ventral margin, about 0.6 times as long as ramus. Middle apical seta strongest, without breaking plane, unipinnate, about 1.5 times as long as ramus, pointing distally, with slightly curled tip. Outer apical seta also without breaking plane and unipinnate, relatively strong basally but much shorter, about 0.8 times as long as ramus, inserted close to dorsal surface and pointing laterally.

Antennula ( Figure 10B ) relatively large, seven-segmented, prehensile and digeniculate, with distal part not clasped (probably random post-mortem effect), fifth segment more robust than in P. young , armature and ornamentation without any difference, except aesthetasc on fifth segment narrower and slightly shorter.

Antenna ( Figure 10B ) more slender than in P. young and P. wangpi , with allobasis slightly more than four times as long as wide. Armature and ornamentation as in P. young .

Labrum ( Figure 10B ), paragnaths (10A), mandibula ( Figure 10B ), maxillula ( Figure 10A ), maxilla ( Figure 10A ), maxilliped ( Figure 10A ) and first swimming leg ( Figure 10A ) as in P. young .

Second swimming leg ( Figures 10A , 11D ) as in P. young , except endopod not inflated in proximal half and about five times as long as wide and reaching three-fifths of first exopodal segment; apical seta 0.5 times as long as segment and pointing distally.

Third swimming leg ( Figures 10C , 11E ) with tubular pore on posterior surface of first exopodal segment as in P. wangpi but general shape much more similar to that in P. young , except outer spine on first exopodal segment less robust and distal outer corner of proximal exopodal segment smooth (spinule missing). Leaf-like seta on apophysis smaller than in P. young and P. wangpi .

Fourth swimming leg ( Figure 10C ) as in P. young , except apical seta on third exopodal segment somewhat shorter (about twice as long as third exopodal segment and 0.6 times as long as entire exopod); endopod and large basal spiniform process as in P. young , except also slightly short in proportion to first exopodal segment.

Fifth leg ( Figure 10D ) simple triangular cuticular plate, inner distal corner produced into distally serrate spiniform process (longer than in P. young ), ornamented with four to six large spinules on inner margin, one arched proximal row of 14 minute spinules on posterior surface, and large cuticular pore on anterior surface; armature as in P. young , except inner endopodal seta only half as long as outer endopodal seta, and not reaching tip of distal spiniform process.

Sixth legs ( Figure 10D ) smooth, unarmed and unornamented, forming simple operculum covering gonopore, slightly smaller than in P. young .

Female (based on allotype and several paratypes). Body length from 345 to 349 µm (345 µm in allotype). Habitus ( Figure 10E ), ornamentation of prosomites, colour and nauplius eye similar to male; genital and first abdominal somite fused into double somite and habitus less slender; free prosomites slightly narrower than urosomites in lateral view.

Genital double somite ( Figure 11F ) slightly wider than long in dorsal view, without any trace of subdivision, with oval dorsal cuticular window in anterior half, much larger than that in male (originating from fused windows of two ancestral somites). Genital complex occupying anterior ventral half of genital double somite; genital apertures covered by vestigial sixth legs; median copulatory pores also covered by fused sixth legs; seminal receptacles small, hard to distinguish from internal tissue and gut content; copulatory duct very short and weakly sclerotized. All posterior sensilla homologous to those on male third urosomite, while two sensilla from male second urosomite missing (nos. 32 and 34).

Third ( Figure 11F ), fourth (preanal) ( Figure 11F ) and fifth (anal) ( Figures 10F , 11F ) urosomites similar to male.

Caudal rami ( Figures 10F , 11F ) laterally compressed but inflated in lateral view (arrowed in Figure 11F ), shorter in proportion to anal somite than in male, only about twice as long as wide. Apical armature in allotype much reduced in length, all less than half as long as caudal rami, but in paratypes not much different to those in male (except outer apical seta slightly shorter). Lateral armature and ornamentation as in male.

Antennula ( Figures 10E , 11G ) segmentation, ornamentation and armature as in P. young , with both aesthetascs very slender (i.e. much more slender than in P. wangpi ).

Antenna ( Figure 10E ), mandibula ( Figure 10E ), maxillula ( Figure 10E ), maxilla ( Figure 10E ), maxilliped ( Figure 10E ), first swimming leg ( Figure 10E ), second swimming leg ( Figures 10E , 11H ), and exopod of fourth swimming leg ( Figure 10E ) similar to male.

Third swimming leg ( Figure 11I,J ) as in P. young , but with shorter apical element (even shorter than in P. wangpi ) on second exopodal segment.

Fourth swimming leg ( Figures 10E , 11K ) without spiniform process on basis. Endopod one-segmented, straight, ornamented with apical row of two spinules at base of apical spine and three spinules on inner margin; apical spine not distinct at base, finely serrated (or bipinnate) distally, and about 0.8 times as long as endopod.

Fifth leg ( Figure 11F ) also simple cuticular plate, but without any spinules along inner margin and with shorter distal spiniform process. Armature similar to male.

Sixth legs ( Figure 11F ) vestigial, simple cuticular plates, covering gonopores, unornamented and unarmed, completely fused, forming simple flap.

Distribution

This species is only known from the type locality, Imjin river near Jeokseong town in South Korea ( Figure 12 ) .

Ecology

Specimens were obtained from interstitial habitats on the river banks, but no data are available on the water chemistry or sediment size.

Figures

Figure 10. Proserpinicaris imjin sp. nov., scanning electron micrographs, (A–D) holotype male; (E and F) allotype female. (A) Habitus, lateral view; (B) antennulae and antennae, lateral view; (C) third and fourth swimming legs, lateral view; (D) fifth and sixth legs, lateral view; (E) prosome, lateral view; (F) anal somite and caudal rami, dorsal view. Scale bars 20 µm for (A), 10 µm for all others.

Figure 11. Proserpinicaris imjin sp. nov., line drawings, (A–E) paratype male; (F–K) paratype female. (A) Anal somite and right caudal ramus, lateral view; (B) anal somite and caudal rami, ventral view; (C) spermatophore; (D) endopod of second swimming leg, anterior view; (E) third swimming leg, posterior view; (F) urosome, lateral view; (G) last four antennular segments with incomplete armature, ventral view; (H) endopod of second swimming leg, anterior view; (I) third swimming leg, anterior view; (J) endopod of third swimming leg, anterior view; (K) endopod of fourth swimming leg, anterior view. Scale bars 50 µm for all. Arrows indicate features different from previous two species.

Figure 12. Distribution of the Proserpinicaris Jakobi, 1972 species in Korea: 1, P. imjin sp. nov.; 2, P. ondali (Lee and Chang, 2009); 3, P. wangpi sp. nov.; 4, P. young sp. nov.; 5, P. sp. See text for more explanation.