Philippiphonte aspidosoma, Huys, Rony & Lee, Jimin, 2018

Huys, Rony & Lee, Jimin, 2018, Philippiphonteaspidosoma gen. et sp. n., a radically divergent member of the Laophontidae from shell gravel in the East Sea, South Korea, including a review of Folioquinpes Fiers & Rutledge, 1990 (Copepoda, Harpacticoida), ZooKeys 775, pp. 15-46 : 15

Philippiphonte aspidosoma sp. n. Figs 2, 3, 4, 5, 6, 7

Type locality.

South Korea, East Sea (Sea of Japan), Gajaebawi, Dokdo island (Liancourt Rocks), 37°14'49.37"N, 131°51'48.24"E, shell gravel, 22 m depth (Figure 1).

Type material. Holotype ♀ dissected on 11 slides (reg. no NIBRIV0000816435), allotype ♂ dissected on 11 slides (reg. no NIBRIV0000816434), remaining paratypes (9 ♀♀, 1 ♂) preserved in formalin (reg. no NIBRIV0000816433). All type specimens were collected on 23 April 2015 from the type locality and are deposited in the National Biological Resources Center (NIBR), Incheon.

Additional material examined.

1 ♂ from Mulgol, Dokdo island, 37°14'35.16"N, 131°51'51.37"E, 15 m depth, 27 June 2015 (reg. no MInRB-Hr15-L001); 1 ♂ from the old harbour of Dokdo island, 37°14'27.31"N, 131°52'16.69"E, 12 m depth, 27 June 2015 (reg. no MInRB-Hr15-L002); 2 ♀♀, 4 ♂♂, 24 August 2016 from type locality (Figure 1) (reg. no MInRB-Hr15-L003). All specimens are deposited in the collections of the Korea Institute of Ocean Science and Technology (KIOST), Busan.

Description of female.

Body length from anterior margin of rostrum to posterior margin of caudal rami 536-612 μm (mean = 574 μm; n = 12; holotype = 552 μm); maximum width measured at level of leg 3-bearing somite: 338 μm (in holotype). Body (Figure 2A) extremely dorsoventrally flattened, porcellidiid-like; except for digestive tract and ovaries completely transparent; dorsal surface of all somites covered with minute setules and denticles (not illustrated); ventral surface of urosomites without surface ornamentation (except for spinule rows around posterior margin). Rostrum large, prominent in dorsal aspect, inverted trapezoid; anterior margin slightly convex, anterolateral corners each with sensillum. Cephalothoracic shield broadly bell-shaped, about 1.5 times wider than long; lateral margins fringed with closely set spinules; dorsal surface with symmetrical pattern of sensilla; posterior margin with setules and spinules. Pedigerous somites bearing legs 2-4 with strongly developed pleurotergites, those of leg 4-bearing somite backwardly produced and embracing leg 5-bearing somite and anterior half of genital double-somite; each provided with strong spinules along lateral margins and shorter spinules along posterior margin; sensillar pattern as illustrated. Leg 5-bearing somite reduced, without marked pleurotergites; posterior margin with spinules dorsally and setules dorsolaterally. Genital double-somite completely fused; original segmentation marked by sensillar pattern, faint dorsal suture and paired arrangement of backwardly directed pleurotergites, each fringed with long spinules laterally and shorter spinules or setules posteriorly; anterior pair larger than posterior pair; ventral posterior margin with paired rows of tiny spinules (Figure 3A). Second and third abdominal somites with lobate pleurotergites, those of penultimate somite embracing anal somite and anterior half of caudal rami; dorsal and lateral ornamentation as in previous somites; ventral posterior margin with paired rows of tiny spinules (Figure 3A). Anal somite without expanded pleurotergites (Figs 2A; 4 A–B); dorsal surface with paired tube-pores and sensilla flanking rounded, naked anal operculum; ventral surface with two pairs of tube-pores and tiny spinules near bases of caudal rami; anal frill triradiate, well developed, provided with long setular extensions.

Caudal rami (Figure 4 A–B) flattened, about 2.2 times longer than maximum width, with straight outer and markedly convex inner margin; with elaborate ornamentation consisting of strong, medially directed spinules along inner margin, finer spinules along outer margin, and two spinule rows in anterior half of ventral surface. Armature consisting of seven setae, all of which located near posterior margin of ramus; seta I minute, positioned dorsally near naked seta II; seta III located at outer distal corner, naked; setae IV–V with fracture planes and fused at base; seta IV sparsely pinnate, about 18% of body length; seta V very long, about 3.5 times length of seta IV (Figure 2A), with minute spinules in middle third and sparse setules in distal quarter; seta VI located at inner distal corner; seta VII located near posterior margin of ramus, tri-articulate at base and sparsely plumose in distal third.

Antennule (Figure 2B) 5-segmented, slender; without spinous processes on segments 1-2; segment 1 with setules along anterior and ventral distal margin, those on the latter being particularly long; anterior margin of segments 2 and 3 (proximal half only) with short setules; segment 3 longest, about 2.4 times as long as segment 1 (measured along anterior margin), with aesthetasc (114 μm) arising from socle and fused at base to long naked seta. Armature formula 1-[1 plumose], 2-[4 + 4 plumose], 3-[5 + 2 plumose + (1 + ae)], 4-[1], 5-[8 + acrothek]; apical acrothek consisting of two basally fused setae, aesthetasc not observed.

Antenna (Figure 2C) with allobasis, bearing two spinule rows and slender unipinnate seta along abexopodal margin. Exopod 1-segmented, with two lateral and two apical bipinnate setae (outer one slightly spiniform). Free endopod with two spines and one seta laterally, and distal armature consisting of two geniculate setae, one long (fused at base to vestigial seta) and two short pinnate spines.

Mandible (Figure 3B) with slender gnathobase bearing several multicuspidate teeth and one unipinnate seta. Palp small, comprising basis with incorporated rami; armature of basis represented by one plumose seta originating from small articulating socle; endopod represented by one short and two long plumose setae; exopod represented by one sparsely pinnate seta.

Maxillule (Figure 3C) with well-developed syncoxal arthrite bearing two spinule rows on posterior surface and total of eight elements along distal margin. Coxal endite with one naked seta and one unipinnate spine. Basis without defined rami; armature represented by one lateral and three distal setae (innermost of which spiniform and unipinnate).

Maxilla (Figure 3D). Syncoxa with spinules along distal outer margin and two coxal endites; proximal endite with naked seta and basally fused unipinnate spine, distal endite with two setae of which innermost one fused at base. Allobasis produced into distally unipinnate claw, with accessory armature consisting of small naked seta and unipinnate spiniform element. Endopod represented by a minute segment with two basally fused setae.

Maxilliped (Figure 3E) elongate and slender. Syncoxa with one sparsely plumose seta and tuft of long setules near distal inner corner and additional inner setules around base. Basis without ornamentation except for few spinules near outer distal corner. Endopod represented by acutely recurved claw with minute accessory seta at its base.

Leg 1 (Figure 3F) with very wide and narrow intercoxal sclerite. Basis with sparsely plumose inner (anterior) and outer seta. Exopod 3-segmented, all segments of about equal size; exp-1 with long outer spine, extending beyond distal margin of exp-3 and bearing stiff spinules (gradually increasing in size distally) along its outer margin; exp-2 and -3 wider than long, with tuft of setules along inner margin; exp-2 with outer spine being unipinnate in its distal half; exp-3 with two unipinnate spines and two geniculate setae (pinnules restricted to apical parts of elements). Endopod 2-segmented, prehensile; enp-1 elongate, about five times as long as wide, unarmed, with long spinules along proximal half of inner margin; enp-2 with short, acutely recurved claw, outer distal corner with few spinules but accessory seta not discernible.

Legs 2-4 (P2-P4) (Figs 4 C–D; 5A) with widely separated members connected by narrow intercoxal sclerites. Praecoxae represented by small U-shaped sclerite. Coxae with spinular ornamentation on anterior surface as figured. Bases transversally elongate, becoming progressively longer from P2 to P4; outer margin with setules (P2) or multiple rows of spinules (P3-P4); with long (P2-P3) or short (P4) outer seta, bipinnate in P2 only; anterior surface with tube-pore. Exopods 3-segmented; exp-1 without inner seta; inner margin of exp-1 and -2 with few long setules; outer margin of all segments with spinular ornamentation as figured; P3 exp-3 with tube-pore on anterior surface; outer exopodal spines typically unipinnate in distal half only (except for outer spine of exp-1 and proximal outer spine on exp-3 of P4 being bipinnate); inner setae very long and plumose. Endopods 2-segmented; enp-1 unarmed, shorter than enp-2, with setules along both inner and outer margins; outer margin of enp-2 with double row of flimsy setular extensions; outer distal spine of P3 enp-2 bipinnate. Spine and setal formulae of swimming legs as for genus.

Leg 5 (Figure 3A) consisting of baseoendopod and 1-segmented exopod. Baseoendopod subcylindrical and elongate (about 8.5 times as long as average width), backwardly recurved and fused at base to pleural wall of somite; bearing outer basal seta arising from short setophore (located dorsally); endopodal armature consisting of long seta located at about two-thirds the segment length, and two closely set, minute setae originating near boundary with exopod; all setae naked; proximal third with tube-pore on ventral surface. Exopod about one third the size of baseoendopod; inner margin with one bipinnate and one unipinnate seta, distal margin with long plumose and short naked seta.

Genital field (Figure 3A) located in anterior third of genital double-somite, near border with leg 5-bearing somite. Genital apertures closed off by opercula derived from vestigial sixth legs, each bearing two minute, naked setae. Copulatory pore median, of moderate size. Egg-sac not observed.

Description of male.

Slightly smaller than female; body length from anterior margin of rostrum to posterior margin of caudal rami 461-527 μm (mean = 489 μm; n = 8; allotype = 523 μm); maximum width measured near posterior margin of cephalothorax: 315 μm (in allotype). Body (Figure 6A) of similar shape, transparency and with virtually identical ornamentation as in female. Rostrum comparatively narrower than in female and with virtually straight anterior margin. Genital and first abdominal somites completely free; posterior margin of former with continuous row of short spinules or setules posteriorly; lobate pleurotergites of genital somite more slender than in female. Anal somite and caudal rami (Figure 5 B–D) as in female.

Antennule (Figure 6B) 8-segmented, subchirocerate, with geniculation between segments 5 and 6; without spinous processes on segments 1-2. Segment 1 as in female; anterior margin of segments 2 and 3 (proximal half only) with setules; segment 4 represented by an incomplete U-shaped sclerite; segment 5 swollen, with large aesthetasc (125 μm) arising from socle and fused at base to long naked seta; segments 5 and 6 with setae modified into basally fused spinous processes. Armature formula 1-[1 plumose], 2-[4 + 5 plumose], 3-[7 + 1 plumose], 4-[2], 5-[8 + 2 spinulose + 2 spinous processes + (1 + ae)], 6-[2 spinous processes], 7-[1], 8-[7 + acrothek]; apical acrothek consisting of two basally fused setae, aesthetasc not observed.

Leg 3 (Figure 6C) with 3-segmented endopod. Enp-1 shortest, with few setules on both outer and inner margins. Enp-2 forming slender, outwardly recurved, spinous apophysis (homologue of outer distal spine of enp-2 in female) provided with barb along inner margin and minute projections near apex; setules present on both outer and inner margins. Enp-3 with one inner and two apical plumose setae.

Leg 5 (Figure 5E) consisting of baseoendopod and 1-segmented exopod. Baseoendopod elongate, backwardly recurved and fused to pleural wall of somite; bearing outer basal seta arising from short setophore (located dorsally); endopodal armature consisting of two closely set, vestigial setae near boundary with exopod; proximal third with tube-pore on ventral surface. Exopod about one third the size of baseoendopod; inner margin with one strong, bipinnate seta, distal margin with one long and one short naked seta.

Sixth legs (P6) (Figure 5B) asymmetrical with functional right member articulating at base and closing off genital aperture and left member fused at base to genital somite; each vestigial sixth leg with minute naked seta. Spermatophore oval, relatively small (65 μm).

Etymology.

The specific epithet is derived from the Greek άσπίς, meaning shield, and σῶμα, meaning body, and alludes to the dorsoventrally flattened shield-shaped body form.