Farranula concinna ( Dana, 1849 )

Wi, Jin Hee & Soh, Ho Young, 2013, Two Farranula (Copepoda: Cyclopoida: Corycaeidae) species from Korean waters, Journal of Natural History 47 (5 - 12), pp. 289-312 : 293-300

publication ID	https://doi.org/ 10.1080/00222933.2012.708454
persistent identifier	https://treatment.plazi.org/id/CC1B0862-2A41-8C18-FE1B-FE82FE46FBCC
treatment provided by	Felipe
scientific name	Farranula concinna ( Dana, 1849 )
status

Treatment

Farranula concinna ( Dana, 1849)

( Figures 2–6 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 )

Corycäus concinnus: Giesbrecht 1893 [“1892”], p. 661, 675, fig. f.

Corycella concinna: Farran 1911, p. 286 , rem.; Farran 1936, p.139

Corycaeus concinnus: Mori 1937, p.138 , figsf, m

Corycaeus (Corycella) concinnus: M. Dahl 1912, p.121 , figs f, m; Tanaka 1957, p. 96, figs f, m, rem, 1960, p. 88, figs f, m, rem.; Chen et al. 1974, p.66, figs f, m; Zheng et al. 1982, p.150, fig. F.

Farranula concinna Wilson, 1942, p. 186 , fig. 33.

Material examined

In all, 72 ♀♀ and 19 ♂♂ were collected from off Jeju Island , Korea (in the East China Sea) (32 ◦ 00 ′ N, 126 ◦ 5 ′ E) on 17 June 2009, of which 5 ♀♀ and 5 ♂♂ were dissected and examined in detail; 2 ♀♀ and 2 ♂♂ have been deposited in the National Institute of Biological Resources ( NIBR), Incheon, Korea ( NIBRIV0000245151 ) GoogleMaps .

Description of female

Body cylindrical, tapering posteriorly. Total body length in lateral view 930 µm (average: 885 µm, n = 4), measured from anterior margin of prosome to posterior margin of caudal rami. Urosome distinctly narrower than prosome.

Prosome two-segmented ( Figure 2A,B View Figure 2 ), frontal part rounded, with two large separate cuticular lenses: cephalosome completely fused with first pedigerous somite, second to fourth pedigerous somites forming single compound segment with suture line between second and third pedigerous somites; prosome about 1.8 times as long as urosome including caudal rami, 2.5 times as long as urosome excluding caudal rami; third pedigerous somite dorsally covering fourth pedigerous somite, forming inverted triangular shape; fourth pedigerous somite with extended and pointed posterolateral corners, secretory pore on inner pleural area ( Figure 2A View Figure 2 ).

Urosome ( Figure 2A–C View Figure 2 ) two-segmented: first urosomite bearing P5 ventrolaterally ( Figure 2D View Figure 2 ); genital double-somite and anal somite combined. Proportional lengths (%) of urosomites and caudal rami 7.8: 62.8: 29.4. Genital double-somite ( Figure 2A–C View Figure 2 ) rounded in anterior two-fifths and remaining part almost rectangular, length 2.5 times greater than maximum width; rounded hump-like projection arising from anteroventral margin (visible in lateral view), ornamented with patch of spinules, posteroventral margin fringed with minute spinules from one-third distance from posterior margin almost to distal end, in lateral view; posterior margin finely serrated ventrolaterally ( Figure 2C View Figure 2 ); dorsoposterior surface with two adhering spermatophores ( Figure 2B View Figure 2 ); genital area located dorsolaterally, paired genital apertures approximately one-third distance from anterior margin of dorsal surface, hidden behind opercula. Caudal rami ( Figure 2A,C,E View Figure 2 ) cylindrical, about two-fifths length of genital doublesomite, 3.3 times longer than width at base. Each ramus with triangular process located near insertion armed with four setae: slender anterolateral seta II, outer posterolateral seta III short and robust, spiniform and serrated along medial margin, inner terminal seta IV longest and dorsal seta V almost equal in length to seta III ( Figure 2E View Figure 2 ).

Antennule ( Figure 3A View Figure 3 ) short, six-segmented. Armature formula 1-[2], 2-[8], 3-[2+ae], 4-[3+a], 5-[2+ae], 6-[5+(1+ae)]. Proportional lengths (%) of segments measured along posterior non-setiferous margin 21.8: 10.2: 14.2: 29.5: 11.5: 12.8.

Antenna four-segmented ( Figure 3B,C View Figure 3 ), with coxa and basis fused and bearing three endopodal segments. Coxobasis 2.4 times longer than wide, with strong bipinnate seta at inner distal margin. Endopod three-segmented, unequal in length; first endopodal segment robust, much longer than the rest of endopodal segments, about 2.7 times as long as wide, bearing bipinnate seta on inner proximal margin, slightly shorter than coxobasal seta; inner distal margin roughly serrated from two-thirds of margin, with long, curved spinous process at three-quarters of serrated part outer lateral margin ornamented row of denticles; naked seta on distolateral margin (indicated by arrow in Figure 3C View Figure 3 ); second endopodal segment short, bearing three elements: curved stout spine arising from outer distal margin, with lateral branch; slender, pinnate spine located near its base and reaching almost middle of distal spine; and short curved spine arising from inner margin. Third endopodal segment cylindrical, as long as wide and armed with curved terminal claw plus two elements, short spine arising from inner margin and strong seta on outer margin of segment, extending to two-thirds of terminal claw.

Mandible ( Figure 3D,E View Figure 3 ) with two elements on gnathobase: one spine and one blade. Spine broad and robust, with two naked slender setae on medial area and two basal setae. Blade forming spinuos processes, surrounded by patch of spinules around base.

Maxillule ( Figure 3F View Figure 3 ) reduced, bearing four articulated spinous elements: innermost one A at some distance from other elements and distal margin serrated, element B longest and stout, and distal margin with spinous process, element C short and serrated, and element D short and naked.

Maxilla ( Figure 3G View Figure 3 ) two-segmented, allobasis shorter than syncoxa: syncoxa unarmed; allobasis produced distally into strong spine, carrying two naked setae proximally, inner margin bearing three spines of different lengths: two naked spines and longest, unipinnate innermost spine with slender naked seta at base of spine.

Maxilliped ( Figure 3H View Figure 3 ) three-segmented: syncoxa unarmed; basis robust and expanded, with two elements along margin: proximal one short, located at base of distal one, distal one with two to four spinules along inner margin, located at two-thirds distance of inner margin, three times shorter than basis; endopodal segment drawn out into long curved claw, unornamented and slightly shorter than basis, accessory armature consisting of slender long, unipinnate seta on inner proximal margin, and short unipectinate spine laterally on outer proximal margin of claw.

Swimming legs 1–3 ( Figure 4A–C View Figure 4 ) comprising coxa, basis and three-segmented rami. Intercoxal sclerites well developed; basis of P1and P3 with naked outer seta, whereas that of P2 with vestigial coxal seta (indicated by arrows in Figure 4B View Figure 4 ), basis of P1 to P3 with round process between insertions of endopod and exopod; exopods distinctly longer than endopods.

Exopods of P1 to P3: inner margin of proximal segments with long setules, first segments of P1and P3 without spine, and relative length ratio of terminal spine to distal outer spine of P1 to P3 different: P1 smallest (about 2: 1), in P2 2.6: 1, and P3 largest (3.8: 1); terminal spines longer than distal segments: in P1 1.3 times longer, in P2 about 1.7 times longer, and in P3 2.4 times longer.

Endopods of P1 to P3: outer margins of segments with fringe of long setules; relative lengths of distal segments of P1–P3 different, relatively: P1 longest, and P3 shortest; each segment of P3 equal in length; outer margins of segments fringed with setules in P1 to P3; terminal seta of distal segment shortest in P2 and longest in P3; relative length ratio of distal segments to terminal setae of P1–P3 different: in P1 1: 2.6, and in P2, 1: 2.2, and in P3 1: 7.8.

P4 ( Figure 4D View Figure 4 ): with transversely extended intercoxal sclerite narrow, coxa unarmed, and basis with outer basal seta arising from posterior surface, fringed with row of setules along inner margin; exopod well developed, three-segmented, bearing spinules along inner margin of first segment; proportional length ratio of each segment, 37.5: 21.9: 40.6; distal segment about 1.8 times as long as terminal spine. Endopod absent. Armature formula of P1 to P4 as shown in Table 2.

P5 ( Figure 2D View Figure 2 ) consisting of two unequal simple setae, located ventrolaterally. P6 ( Figure 2A–C View Figure 2 ) represented by operculum closing off each genital aperture.

Male

Total body length in lateral view 845 µm (average: 820 µm, n = 7), measured from anterior margin of prosome to posterior margin of urosome. Urosome distinctly narrower than prosome ( Figure 5A,B View Figure 5 ).

Prosome two-segmented, cephalosome fused with first pedigerous somite, and second to fourth pedigerous somites fused into compound segment, prosomal length about 1.8 times as long as urosome including caudal rami, 2.5 times urosome length excluding caudal rami ( Figure 5A,B View Figure 5 ). Suture line present between second and third pedigerous somites dorsolaterally on surface; paired epimeral extensions of third pedigerous somite largely covering fourth pedigerous somite, forming inverted triangle-shape on each side; fourth pedigerous somite with extended and pointed posterolateral corners, reaching midway along genital somite. Frontal part of prosome rounded, with two large contiguous cuticular lenses ( Figure 5A View Figure 5 ).

Genital somite ( Figure 5A,B View Figure 5 ) with four secretory pores on dorsomedial surface; posterior part between sharply narrowing region (indicated by arrows in Figure 5A View Figure 5 ) and rear margin about 2.1 times shorter than rest of genital somite, and 1.2 times as long as caudal ramus.

Caudal rami seven times longer than wide at base ( Figure 5A,B View Figure 5 ), about 2.3 times shorter than urosome. Armature of rami similar to that of female, except for longer caudal seta III.

Antennule (not figured) with segmentation and armature similar to that of female.

Antenna ( Figure 6A View Figure 6 ) sexually dimorphic, four-segmented, with coxa and basis fused and endopod three-segmented. Coxobasis 2.2 times as long as wide, with long, bipinnate strong seta on inner distal margin, reaching to tip of first endopodal segment, fringed with patch of spinules along inner margin. First endopodal segment about 2.5 times as long as maximum width, bearing bipinnate seta on ventral proximal margin, almost as long as coxobasal seta, outer lateral margin ornamented with row of denticles. Second endopodal segment short, bearing three elements: curved stout spine arising from outer distal margin, with lateral branch, short, plumose spine located near base, and short curved spine arising from inner distal margin. Third endopodal segment drawn out into long claw, extending to two thirds of coxobasis and armed with four elements: short spine arising from proximal inner margin, long naked seta and two slender, naked setae inserted on outer proximal margin.

Maxilliped ( Figure 6B View Figure 6 ) sexually dimorphic, four-segmented, comprising syncoxa, basis and two-segmented subchela. Syncoxa without surface ornamentation, unarmed. Basis robust, oval-shaped, particularly swollen in proximal half, inner margin with spiniform seta ornamented with two to four short spinules along inner margin, with slender spinules between proximal third and seta of basis. Subchela comprising unarmed proximal endopodal segment and distal enopodal segment drawn out into long curved claw, with accessory armature consisted of minute, unipinnate spine on outer proximal margin and long, unipinnate spine delimited basally to inner proximal corner of claw.

Swimming legs 1–3 ( Figure 6C–E View Figure 6 ) segmentation and armature similar to female, except relative length ratio of terminal spine to outer distal spine larger (4.3 times) than that of female (3.8 times).

P4 ( Figure 6F View Figure 6 ) similar to that of female, except length ratio of distal segment to terminal spine (1.9: 1) larger than that of female (1.1: 1).

P5 similar to that of female.

P6 ( Figure 5B,C View Figure 5 ) represented by genital flap closing off each genital aperture, armed with long seta; surface ornamented with unique pattern of denticles and two small secretory pores: anterior part with curved line of denticles, outer part fringed with minute denticles and distal margin with comparatively large denticles (indicated by arrow in Figure 5C View Figure 5 ).

Remarks

This species is consistent with the typical morphology of the genus Farranula as characterized by the ventral cephalothoracic process in the female and leg 4 lacking an endopod in both sexes, which distinguishes Farranula from the genus Corycaeus ( Farran, 1911) . The morphological features, such as the combination of proportional lengths of urosomites and caudal ramus, the shape of the genital somite, and the location of the spermatophore attached distally on the genital somite, show this species to be F. concinna . Earlier records of F. concinna have typically been limited to simple and ambiguous descriptions based on habitus, genital double-somite, antenna and / or maxilliped, with P4. In this study, mouthparts including mandible, maxillule, maxilla, and all legs are newly described and revealed as important morphological characteristics: in female 1) anteroventral protrusion of genital double-somite bearing patches of setules, 2) posteroventral margin of genital double-somite fringed with spinules from one-third distance along posterior margin to almost distal end in lateral view, 3) second element of the maxillule ( Figure 3F View Figure 3 ) robust and longest, with spinous process on top of it, and remaining elements about equal in length, 4) allobasis of maxilla drawn out distally into strong spine plus three spines of different lengths, 5) basis of P4 fringed with row of spinules along inner margin (arrowed in Figure 4D View Figure 4 ); in male 6) maxilliped four-segmented, ornamented with row of spinules between seta and about middle of proximal inner margin, 7) relative lengths of spines of P1 to P3 exp-3 different from those of female: in P2-3 exp-3, relative length ratio of terminal spine to distal spine larger than that of female, and that in P1 smaller than in female, 8) distance between sharply narrowing part and distal margin 1.2 times almost same or slightly longer than length of caudal ramus.