Parameiropsis tetraspinosa, Cho, Dae Hyun, Wi, Jin Hee & Suh, Hae-Lip, 2016

Cho, Dae Hyun, Wi, Jin Hee & Suh, Hae-Lip, 2016, Two new species of the deep-sea genus Parameiropsis (Copepoda: Harpacticoida) from the eastern central Pacific, Zootaxa 4132 (4), pp. 521-539 : 529-536

Parameiropsis tetraspinosa n. sp.

( Figs. 5–8 )

Type locality. Eastern central Pacific Ocean, 10˚30.11'N 131˚19.987'W, at a depth of 5036 m.

Material examined. Female holotype dissected and mounted on nine slides ( MABIK CR00235060).

Etymology. The specific name tetraspinosa is taken from the four spines of the endopodal lobe of P5.

Description of female. Body ( Figs. 5 A, B). Length 2 mm, almost cylindrical, maximum width at middle of second pedigerous somite, gradually tapered, with slight demarcation. Cephalothorax and second to fifth urosomites with distal hyaline membrane. Prosome 0.8 times as long as urosome excluding caudal rami, 0.7 times length including caudal rami.

Prosome ( Figs. 5 A, B) comprising cephalothorax completely fused to first pedigerous somite and three free pedigerous somites. Third and fourth pedigerous somites with pointed posterolateral corners in dorsal view. Second pedigerous somite with one pair of sensilla near mid- and posterolateral margins and mid region of posterodorsal margin. Third pedigerous somite with two pairs of sensilla near posterodorsal margin and one pair near posterolateral margin. Fourth pedigerous somite each with one pair of sensilla near posterodorsal and posterolateral margin.

Urosome ( Figs. 5 A, B) 5-segmented, comprising fifth pedigerous somite, genital double–somite (genital somite fused to first abdominal somite) and three free abdominal somites. Genital double–somite as long as wide; fusion line marked only by short lateral subcuticular rib.

Anal somite ( Figs. 5 A, B) elongate, tapered posteriorly, approximately 1.5 times as long as preceding somite, anal operculum not reaching distal margin of anal somite.

Caudal rami ( Figs. 5 A, C) with almost straight inner and outer margins, approximately half length of anal somite, almost 3.9 times longer than wide, inner margin unornamented, with 6 setae; setae II and VII of similar length, seta III lost in preparation, seta IV ( Fig. 5 C’) longest, seta V ( Fig. 5 C”) approximately 3.7 times as long as caudal rami, seta VI longer than setae II and VII.

Rostrum ( Fig. 5 A) not fused to cephalothorax, sub-rectangular, with trifid tip and two sensilla apically inserted ( Fig. 5 D).

Antennule ( Fig. 6 A) 8-segmented, about half length of cephalothorax. Relative lengths (%) of segments measured from proximal end along caudal margin 18.6:20.5:23.6:9.1:8.4:4.6:3.8:11.4; first segment short, bearing 2 spinules on outer margin, 1 seta on outer distal margin, and 4 spinules on posterior surface; second segment with 3 naked setae (2 long and 1 short) on anterior surface, 3 setae (1 pinnate and 2 naked) on outer margin, and 4 naked setae on posterior surface; third segment longest, with 4 setae (1 proximal, 2 middle, and 1 distal) along outer margin, each 1 long naked seta on anterior and posterior surface, long slender distal aesthetasc basally fused to 1 distal seta; proximal 3 segments more robust and longer than distal 5 segments; fourth segment each with 1 naked seta medially and distally on outer margin; fifth segment each with 1 long naked seta on mid- and disto-outer margins and 1 long pinnate seta on distal margin; sixth segment with 1 distal seta and 1 inner seta; seventh segment with 1 long naked distal seta; eighth segment with 3 simple setae on inner margin,1 long simple apical seta, and 1 narrow aesthetasc fused to 2 long setae apically. Armature formula as follows: 1/10/6 + (1 + Ae)/2/2/2/1/4 + (2 + Ae).

Antenna ( Fig. 6 B) comprising coxa, allobasis, free second enp, and exp: coxa thick, short, and bare; allobasis thick, about twice as long as wide, with three longitudinal rows of spinules on proximal edge (arrowed in Fig. 6 B); exp 1-segmented, with 1 setulose seta on inner medial margin, 3 subapical spinules, and 1 apical setulose seta; free endopodal segment shorter than allobasis, with group of spinules on proximal inner margin, inner medial margin with 2 robust spines ornamented with crenulations along medial margin (arrowed in Fig. 6 B), 5 short blunt spinules, and 1 long simple seta, row of setules on outer distal margin, distal margin with 4 crenulate spines, 1 modified spine bearing 8 simple spinules and 1 simple seta (arrowed in Fig. 6 B), 1 bipinnate seta and row of setules.

Labrum ( Fig. 6 C) represented by a triangular plate, with single tip and fringed by hyaline around apex.

Mandible ( Fig. 6 D) comprising coxa, basis, enp, and exp: coxa elongated, with spinules on proximal margin; long gnathobasis with a sharp cutting edge, armed with 2 apical long teeth (outer teeth with 1 long spinule, inner teeth multicuspidate), 2 subapical short teeth (inner teeth with 1 short spinule), and 1 long and strong seta distally inserted on oral margin, with inner row of spinules; basis approximately 3 times as long as wide, with row of spinules along inner margin; exp 1-segmented, with 2 apical setae (inner unequally bifid setulose seta, outer seta broken); enp 1-segmented, with 4 apical setae fused to segment, 1 apical seta, and row of spinules along inner margin.

Maxillule ( Fig. 6 E) comprising praecoxa, coxa, basis, exp, and enp: praecoxa elongated, praecoxal arthrite with 6 slender setae apically, 2 subapical simple setae, 1 spinule on inner proximal margin, and 2 long simple setae on anterior surface; coxal endite with row of spinules along outer proximal margin and 3 slender setae and 1 geniculate seta apically; basal endite with 3 apical setae and 2 simple setae on posterior surface; exp 1-segmented represented by distinct segment armed with 1 bipinnate seta and 1 simple seta; enp 1-segmented fused to basis and represented by lobe armed with 2 long simple setae.

Maxilla ( Fig. 6 F) comprising syncoxa, basis, and enp: syncoxa with 2 endites, proximal endite armed with 1 long bipinnate seta, distal endite armed 1 long unipinnate seta and 1 long simple seta; basis drawn into strong, sclerotized and serrated claw, with strong accompanying spine inserted on inner proximal margin; enp fused to basis and armed with 2 distal simple slender setae.

Maxilliped ( Fig. 6 G) comprising syncoxa, basis, and enp: syncoxa thick, with group of spinules on inner proximal margin, 2 setae on inner distal margin; basis longer than syncoxa, with row of spinules along inner margin and longitudinal row of spinules on outer medial margin; enp 1-segmented, as long as basis, drawn into strong claw, concave margin ornamented with strong spinules along inner distal margin, 1 long slender seta on inner proximal margin, and 2 simple setae.

Armature formula of P1 to P4 as follows:

P1 ( Figs. 7 A, B) intercoxal sclerite transversely elongated, bare. Coxa approximately 0.4 times as long as wide, with two oblique rows of spinules near center and outer of distal margin on anterior surface. Basis short, narrower than coxa, with spinules and 1 long strong spine on inner margin, reaching beyond distal margin of enp-1, 1 long bipinnate outer seta, three transverse rows of spinules (one near base of exp, one on distal middle side, one on proximal middle side, the latter with longest spinules), and 1 strong spinule at base of inner spine. Both rami subequal in length, tapering gradually toward distal segment: exp-1 approximately 1.3 times as long as wide, with some spinules along outer margin, row of blunt spinules along outer distal margin, 2 short spinules near base of outer spine, 2 long spinules on posterior surface, setules on inner distal margin and armed with 1 bipinnate spine subapically; exp-2 shorter than exp-1, with 1 inner seta, 2 short spinules near base of outer spine, 2 spinules along inner margin, blunt spinules along outer distal margin, setules on inner distal margin and armed with 1 unipinnate outer spine; exp-3 slightly longer than exp-2, with 1 spinule on inner margin, 3 outer bipinnate spines (distalmost one longest, proximal 2 outer spines shorter than spines of exp-1 and exp-2), 1 outer apical bipinnate spine (longer than other spines, armed with spinules on the outer margin and setules on the inner margin), 1 long inner apical unipinnate spine. Enp with row of spinules along outer margin on each segments; enp-1 approximately 1.3 times as long as wide, with 2 strong spinules and 1 long bipinnate subapical seta 2.6 times as long as segment on inner margin, row of blunt spinules along outer distal margin; enp-2 shorter than enp-1, with 1 long unipinnate subapical seta on inner margin, approximately 2.5 times as long as segment and shorter than inner seta of enp-1, row of blunt spinules along outer distal margin; enp-3 similar in length to enp-1, with some spinules on inner margin, 1 outer bipinnate spine, 1 outer apical unipinnate spine, 1 long inner apical unipinnate seta, armed with setules on the inner margin.

P2 ( Fig. 7 C) intercoxal sclerite smooth, rostrocaudally elongated, with deeply concave distal margin. Coxa approximately 0.4 times as long as wide, bare. Basis short, narrower than coxa, with 1 long simple outer seta, row of long spinules along inner margin and two transverse rows of strong spinules near base of exp and distal middle margin, respectively. Both rami tapering toward distal segment, 3-segmented. Exp approximately 1.3 times as long as enp: exp-1 approximately 1.7 times as long as wide, with 1 bipinnate subapical outer spine and 1 slender bipinnate subapical inner seta, 1 spinule subapically on outer margin, 1 long slender spinule on posterior surface, 1 short spinule near base of outer spine, 2 strong spinules along outer distal margin, and row of setules on inner distal margin; exp-2 shorter than exp-1, with 1 bipinnate subapical outer spine, 1 bipinnate subapical inner seta, 1 short spinule near base of outer spine, 2 short spinules along outer distal margin, and row of setules on the inner distal margin; exp-3 similar in length to exp-1, with 3 outer spines which distalmost longest, 1 long outer apical bipinnate spine (longer than other spines, armed with spinules on outer margin and setules on inner margin), 1 long inner apical bipinnate seta, armed with spinules on outer margin and setules on inner margin, 2 bipinnate inner setae. Enp with row of spinules along outer margin on each segment; enp-1 as long as wide, with 1 bipinnate subapical seta on inner margin, row of spinules along outer margin, 3 strong spinules along outer distal margin and row of setules on inner distal margin; enp-2 longer than enp-1, with 1 bipinnate subapical seta on inner margin, row of spinules along outer margin, 2 strong spinules along outer distal margin and row of setules on inner distal margin; enp-3 longest, with 2 inner and 2 apical setae, 1 outer spine accompanied by a small spinule, and some spinules along outer margin.

P3 ( Figs. 8 A, B) intercoxal sclerite smooth, rostrocaudally elongated, with deeply concave distal margin. Coxa approximately 0.4 times as long as wide, bare. Basis with 1 bipinnate outer seta, row of spinules along inner margin and two transverse rows of strong spinules near base of outer seta and distal middle margin. Both rami tapering toward distal segment, 3-segmented. Exp approximately 1.3 times as long as enp; exp-1 approximately 2.1 times as long as wide, with 1 subapical inner seta, row of setules on inner distal margin, 1 short strong spinule near base of outer spine, 2 strong spinules along outer distal margin, and armed with 1 subapical outer spine; exp-2 shorter than exp-1, with 1 subapical inner seta as long as segment, 1 short spinule near base of outer spine, 2 strong spinules along outer distal margin, row of setules on inner distal margin, and armed with 1 subapical outer spine; exp-3 similar in length to exp-1, with 4 strong outer spines (abnormal), 1 long outer apical bipinnate spine armed with spinules on outer margin and setules on inner margin, 1 long inner apical bipinnate seta armed with spinules on outer margin and setules on inner margin, and 3 bipinnate inner setae. Enp with row of spinules along outer margin of each segment; enp-1 as long as wide, with 1 subapical inner seta, 3 strong spinules along outer distal margin and row of setules along inner distal margin; enp-2 longer than enp-1, with 1 subapical inner seta, 2 strong spinules along outer distal margin, and row of setules on inner distal margin; enp-3 longest, with 1 strong outer bipinnate spine, 2 apical bipinnate setae, and 3 inner setae.

P4 ( Fig. 8 C) intercoxal sclerite smooth, rostrocaudally elongated, with deeply concave distal margin. Coxa approximately 0.6 times as long as wide, bare. Basis with 1 naked outer seta, row of spinules along inner margin and two transverse rows of strong spinules near base of outer seta and distal middle margin. Both rami tapering toward distal segment, 3-segmented. Exp approximately 1.4 times as long as enp; exp-1 approximately 1.9 times as long as wide, with 1 slender bipinnate inner seta, 1 spinule near base of outer spine, 2 strong spinules along outer distal margin, and armed with 1 subapical outer spine; exp-2 shorter than exp-1, with 1 bipinnate inner seta, 1 spinule near base of outer spine, and 1 strong spinule on outer distal margin, and armed with 1 subapical outer spine; exp-3 longer than exp-1, with 3 outer spines, 1 long outer apical bipinnate spine armed with spinules on the outer margin and setules on the inner margin, 1 long inner apical bipinnate seta armed with spinules on the outer margin and setules on the inner margin, and 3 bipinnate inner setae. Enp with row of spinules along outer margin on each segment, except for enp-1; enp-1 approximately 1.5 times as long as wide, with 1 bipinnate subapical inner seta and 3 strong spinules along outer distal margin; enp-2 longer than exp-1, with 1 bipinnate subapical inner seta and 2 strong spinules along outer distal margin; enp-3 longest, with 1 strong outer bipinnate spine, 2 apical bipinnate setae, and 2 bipinnate inner setae.

P5 ( Fig. 7 D) composed of benp fused medially, and separate exp. Benp with outer simple seta on basis. Endopodal lobe wide armed with 4 long bipinnate spines, with length ratio (from inner side) 1.1:1.1:1.4:1, and row of spinules. Exp 1-segmented, approximately 1.2 times as long as wide, armed with 4 setae.

P6 ( Fig. 7 E) formed by a fused plate with 1 simple seta on each side. Genital aperture fused; a single copulatory pore followed by a long copulatory tube; seminal receptacles paired.

Remarks. Parameiropsis tetraspinosa n. sp. is similar to P. peruanus in the absence of a seta fused to the outermost spine of the enp of the antenna and the general features of the swimming legs. However, the two species can be differentiated by a greater length-to-width ratio of the caudal ramus in P. tetraspinosa (3.9:1 vs. 2.3:1), the presence of a distal seta on the syncoxa of the maxilliped in P. tetraspinosa , and by the medially fused P 5 in P. tetraspinosa . Additionally, P. tetraspinosa resembles P. magnus in terms of the morphological combination of the maxilliped syncoxa with 2 distal setae and the general features of the swimming legs. However, P. tetraspinosa can be distinguished from P. magnus by a greater length-to-width ratio of the caudal ramus in P. tetraspinosa (3.9:1 vs. 1:1), the presence of a proximal seta and a less developed claw on the enp of the maxilliped in P. tetraspinosa (vs. prominently developed), and the fact that P5 has separate exp and benp in P. tetraspinosa . The presence of a distal seta on the syncoxa of the maxilliped is also found in four previously described species ( P. rapiens , P. magnus , P. poseidonicus and P. amphitriteae ). Of these, P. magnus has 2 setae on the syncoxa of the maxilliped, whereas the other three species cited each have 1 seta. Additionally, P. tetraspinosa can be separated from the other species in terms of the morphological combination of the 4 outer spines on the endopodal lobe of P5, whereas the corresponding number is 3 in P. peruanus , P. rapiens , P. magnus , and P. k o do s e n s i s and 2 in P. antennafortis , P. poseidonicus , P. neptuni , P. senckenbergi , and P. amphitriteae .

Figures

FIGURE 5. Parameiropsis tetraspinosa n. sp., holotype female. A, habitus, dorsal view; B, habitus, lateral view; C, caudal rami, ventral view; C’, partial view of seta IV; C ”, partial view of seta V; D, rostrum. Scale bars are given in µm.

FIGURE 6. Parameiropsis tetraspinosa n. sp., holotype female. A, antennule; B, antenna; C, labrum; D, mandible; E, maxillule; F, maxilla; G, maxilliped. Arrows point to significant features. Scale bars are given in µm.

FIGURE 7. Parameiropsis tetraspinosa n. sp., holotype female. A, P 1; B, detail of right P 1 basis close to exp- 1; C, P 2; D, P 5; E, P 6. Scale bars are given in µm.

FIGURE 8. Parameiropsis tetraspinosa n. sp., holotype female. A, P 3; A’, inner distal seta and outer distal spine on P 3 exp- 3; B, enp of right P 3; C, P 4; C’, partial view of inner distal seta. Scale bars are given in µm.