Apodopsyllus unisetosus, Back & Lee, 2012

Back, Jinwook & Lee, Wonchoel, 2012, Two new species of Apodopsyllus (Copepoda, Harpacticoida) from Jeju Island, Korea, Zootaxa 3368 (1), pp. 128-145 : 135-142

publication ID	https://doi.org/ 10.11646/zootaxa.3368.1.6
DOI	https://doi.org/10.5281/zenodo.5253984
persistent identifier	https://treatment.plazi.org/id/2F57495B-957D-9D24-90F2-FA3DFEA5FD24
treatment provided by	Felipe
scientific name	Apodopsyllus unisetosus
status	sp. nov.

Treatment

Apodopsyllus unisetosus sp. nov.

( Figs. 5–9 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8 View FIGURE 9 )

Type locality. Subtidal zone near Seogwipo port on Jeju island, Korea (33° 13' 33''N 126° 34' 39''E), depth 15–20m, sand GoogleMaps .

Material examined. Holotype, 1 female ( NIBRIV0000245116 ) dissected on 5 slides . Paratypes: 1 male ( NIBRIV0000245117 ) dissected on 6 slides , 1 female ( NIBRIV0000245118 ) and 2 males ( NIBRIV0000245119 ) in 70% alcohol. All samples are from the type locality collected by J. Back, using a van Veen grab from a fishing boat on 4 June 2010 .

Description of female (holotype). Body ( Fig. 5A–B View FIGURE 5 ) elongate, cylindrical, depressed dorsoventrally, and somites weakly separated dorsally. Total body length 655 µm (n= 3, mean= 653); measured from tip of rostrum to rear margin of caudal rami. Largest width 70 µm measured near middle of cephalothorax.

Rostrum ( Fig. 5A View FIGURE 5 ) diminutive, triangular, bare, fused to cephalic shield. Cephalothorax bare with depressions dorsally; pleural areas weakly developed, posterior margin smooth. Prosome and urosome with plate-like structures dorsally and laterally except for anal somite. Genital somite and first abdominal somite completely fused forming genital double-somite. Genital field ( Fig. 7C View FIGURE 7 ) located midventrally at anterior fourth of genital double-somite. No discrete copulatory pore observed, presumably covered by process. P6 represented by two bare setae. Penultimate somite with well-developed, smooth, and thin pseudoperculum; anal somite with deep median cleft and operculum not developed.

Caudal rami ( Fig. 5D View FIGURE 5 ), juxtaposed, about 4.5 times as long as wide, conical, distal margin acutely pointed; each ramus armed with seven setae; seta I shortest, bare, ventrally; seta II, III pinnate, of similar length; seta IV bare; seta V longest, bare; seta VI bare, as long as seta IV; seta VII pinnate, tri-articulate at base on dorsal surface, inserted on small pedestal.

Antennule ( Fig. 7A View FIGURE 7 1 –A View FIGURE 1 3 View FIGURE 3 ), eight-segmented, short, robust. Segment-1 longest, with row of spinules along anterior margin, without seta; segment-4 forming sub-cylindrical process armed with one long slender seta fused basally to aesthetasc; segment 6 armed with one slender pinnate seta arising from sub-cylindrical process; armature formula: 1–[0], 2–[8+1 pinnate], 3–[8], 4–[2+(1+ae)], 5– [1], 6–[1+1 pinnate], 7–[4], 8–[4+acrothek], apical acrothek consisting of well-developed aesthetasc fused basally to two slender, naked setae.

Antenna ( Figs. 7B View FIGURE 7 1 View FIGURE 1 , B 2 View FIGURE 2 ), basis approximately twice as long as wide, without surface ornamentation. Exopod one-segmented, with one apical bare seta. Proximal endopodal segment with one pinnate abexopodal seta and ornamented with row of spinules near distal inner corner; distal endopodal segment armed with three bare, one pinnate, and one geniculate setae laterally, one geniculate seta fused basally to one slender naked seta, and three geniculate and one bare setae apically.

Mandible ( Fig. 6A View FIGURE 6 ), coxa with developed gnathobase bearing one slender bare seta at dorsal corner and eight spinous overlapping teeth. Palp biramous, comprising of basis, one-segmented exopod and two-segmented endopod. Basis widening distally, with one naked seta. Exp-1 as long as enp-1, with two lateral and two apical bare setae. Endopod longer than exopod; enp-1 with one pinnate and one bare setae; enp-2 of about same size of exp-1, with two bare setae and three basally fused setae at apex.

Maxillule ( Fig. 6B View FIGURE 6 ), praecoxal arthrite well developed, with six spines, one modified, one bare, and two juxtaposed slender bare setae. Coxa with cylindrical endite, armed with three apical bare setae. Basis endites fused, armed with six bare setae apically. Exopod one-segmented, small, with one bare seta on distal margin. Endopod one-segmented, rectangular, with six bare setae.

Maxilla ( Fig. 6C View FIGURE 6 ), syncoxa with three cylindrical endites; praecoxal and proximal coxal endites with two bare setae each; distal coxal endite with three bare setae. Allobasis with one stout blade-like seta and two slender bare setae around distal margin. Endopod two-segmented; enp-1 with one bare seta distally; enp-2 with one lateral longest and four distal bare setae.

Maxilliped ( Fig. 6D View FIGURE 6 ), four-segmented, comprising syncoxa, basis and two-segmented endopod. Syncoxa bare, twice as long as maximum width. Basis elongate, 2.8 times as long as wide, with row of spinules along distal half; enp-1 with two small, bare, lateral setae and one long, stout, naked distal seta; enp-2 with two naked apical setae.

P1 ( Fig 8A View FIGURE 8 ), coxa fused to lateral side of cephalsome. Basis with one pinnate inner and one bare outer setae. Exp-1 about 1.2 times longer than exp-2, with one outer pinnate seta and with row of spinules along outer margin; exp-2 with four unipinnate setae. Endopod 1.2 times as long as exopod; enp-1 elongate, 7 times as long as wide, ornamented with row of spinules along outer margin; enp-2 with two apical geniculate setae.

P2–P3 ( Figs. 5C View FIGURE 5 , 8B–C View FIGURE 8 ), coxa fused to lateral side of free pedigerous somites. Basis with one bare (P2) or pinnate (P3) outer seta. Endopod absent. Exopod three-segmented; exp-1 with one outer spine and ornamented with row of spinules along outer margin; exp-2 inner distal corner forming spinous projection, with one outer spine; exp-3 with one outer spine and one apical geniculate seta.

P4 ( Fig. 8D View FIGURE 8 ), basis with one pinnate outer seta. Endopod represented by one small naked seta near of basis. Exopod three-segmented; exp-1 with one outer spine; exp-2 inner distal corner forming spinous projection with spinules, with one outer spine; exp-3 with one outer spine and one apical geniculate seta.

Armature formula as follows:

P5 ( Fig. 7C View FIGURE 7 ), baseoendopod partly incorporated into somite, with one basal bare seta. Exopod completely fused with baseoendopodal lobe, represented by rounded depression armed with two slender bare setae. Baseoendopodal lobe conical, armed with one subapical naked seta.

Description of male (paratype). Smaller and more slender than female ( Fig. 9A View FIGURE 9 ). Body length 600 µm (n=3, mean=595). Largest width measured at cephalic shield: 65 µm. General body shape and ornamentation as in female except for separation of genital and first abdominal somites; additional sexual dimorphism in A1 and P6.

Antennule ( Fig. 9B View FIGURE 9 1 –B View FIGURE 1 2 View FIGURE 2 ), six-segmented, short, robust, subchirocer; segment-5, swollen, largest; Armature formula: 1–[0], 2–[8+1 pinnate], 3–[4], 4–[1], 5–[4+1 pinnate + (1+ae)], 6–[9+1 pinnate+acrothek], apical acrothek consisting of well-developed aesthetasc fused basally to two naked setae].

P5 ( Fig. 9C View FIGURE 9 ), shape as in female, fused with ventral plate, with one outer basal seta proximally; endopodal lobe developed, with one small naked setae; exopod completely fused with endopodal lobe, represented by round depression, with two naked setae.

P6 ( Fig. 9D View FIGURE 9 ), represented by one plate, fused medially, but separated by rounded median cleft; each with one stout bare seta in middle and two naked setae.

Etymology. The specific name refers to the characteristic of antennary exopod armed with one seta.

Remarks. The new species is clearly distinguished from its congeners by the following combination of characters: 1) exopod of antenna with one apical seta (this is the only species in the genus Apodopsyllus ), 2) P5 fused with somite, 3) P1 armed with one inner and one outer basal setae, and (4) male P6 well-developed and with a unique shape.