Apodopsyllus gwakjiensis, 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 : 130-135

publication ID	https://doi.org/ 10.11646/zootaxa.3368.1.6
persistent identifier	https://treatment.plazi.org/id/2F57495B-9578-9D2D-90F2-FE7DFEB5FA6D
treatment provided by	Felipe
scientific name	Apodopsyllus gwakjiensis
status	sp. nov.

Treatment

Apodopsyllus gwakjiensis sp. nov.

( Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Type locality. An upper intertidal zone at Gwakji sand beach on Jeju Island, Korea (33° 27' 04''N 126° 18' 19''E) GoogleMaps .

Material examined. Holotype, 1 female ( NIBRIV0000245112 ) dissected on 7 slides . Paratypes: 1 male ( NIBRIV0000245113 ) dissected on 5 slides, and 6 females ( NIBRIV0000245114 ) and 7 males ( NIBRIV0000245115 ) in 70% alcohol. All samples are from the type locality collected by J. Back, by sand rinsing on 3 June 2010 .

Description of female (holotype). Body ( Fig. 1A–B View FIGURE 1 ). Elongate, cylindrical, slightly depressed dorsoventrally, and somites not clearly demarcated from each other. Total body length 550 µm (n=6, mean=556 µm); measured from tip of rostrum to posterior margin of caudal rami; largest width 70 µm measured midway along cephalothorax. Few sensilla present as illustrated in figure 1A.

Rostrum ( Fig. 1A View FIGURE 1 ) diminutive, triangular, bare, fused with cephalic shield. Cephalothorax quadrangular, with few sensilla; 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. 1E View FIGURE 1 ) located at anterior third of genital double-somite. Copulatory pore observed, and covered by small process. Each P6 ( Fig. 1E View FIGURE 1 ) represented by chitinous out-growth armed with one longer inner and one shorter outer pinnate setae. Penultimate somite without pseudoperculum; anal somite deeply cleft and operculum not developed.

Caudal rami damaged during dissection (figured in male).

Antennule ( Fig. 2A View FIGURE 2 ) eight-segmented, short, robust. Segment-1 longest, with row of spinules on lateral margin; segment-4 forming sub-cylindrical process armed with one long slender seta fused basally to aesthetasc; segment-6 armed with one slender bare seta arising from sub-cylindrical process; armature formula: 1–[0], 2–[7+2 pinnate], 3–[6], 4–[2+(1+ae)], 5–[1], 6–[5], 7–[1], 8–[5+acrothek], apical acrothek consisting of well-developed aesthetasc fused basally to two slender, naked setae.

Antenna ( Fig. 1C View FIGURE 1 ) with coxa, basis, and two-segmented endopod. Coxa small and bare. Basis, approximately twice as long as wide, without any surface ornamentation. Exopod one-segmented, with one pinnate seta and two bifurcate setae. Proximal endopodal segment with one pinnate abexopodal seta; distal endopodal segment armed with three geniculate setae, one small seta, apically; one lateral bare seta, one lateral geniculate seta, and one geniculate seta fused basally to one slender seta.

Mandible ( Fig. 2B View FIGURE 2 ), coxa with well-developed gnathobase bearing one slender bare seta at dorsal corner and eight spinous overlapping teeth. Palp biramous, comprising basis, one-segmented exopod, and two-segmented endopod. Basis widening distally, with one pinnate seta. Exopod with two lateral and two apical bare setae. Endopod long; enp-1 with two bare seta on distal margin; enp-2 as long as exp, apically with five bare setae, two of which basally fused.

Maxillule ( Fig. 2C View FIGURE 2 ), praecoxal arthrite well developed, with five geniculate spines, one slender seta on distal corner, and two juxtaposed slender bare setae on anterior surface near outer margin. Coxa with cylindrical endite bearing four apical bare setae. Basis cylindrical, endites fused, collectively two pinnate and three bare setae apically. Exopod one-segmented, small, with one stout pinnate and one slender bare setae. Endopod onesegmented, rectangular, with six bare setae around distal margin.

Maxilla ( Fig. 2D View FIGURE 2 ), syncoxa with three cylindrical endites; first and second coxal endites armed with two bare setae each; third coxal endite with two apical pinnate setae. Allobasis with one stout unipinnate, one slender distal setae, and one bare seta near base of endopod. Endopod one-segmented, indistinctly subdivided, with four bare setae around distal margin.

Maxilliped ( Fig. 2E View FIGURE 2 ), four-segmented comprising syncoxa, basis, and two-segmented endopod. Syncoxa and elongate basis without ornamentation. Enp-1 about 2.8 times as long as wide, with one minute bare and one stout distal setae. Enp-2 with two long naked apical setae.

Coxa of P1–P4 fused to posterior lateral margin of cephalsome (P1), or free pedigerous somites (P2–P4).

P1 ( Fig. 3A View FIGURE 3 ), basis with one pinnate inner seta and row of spinules near base of exopod. Exopod twosegmented; exp-1 about 1.7 times longer than exp-2, with one outer unipinnate seta and ornamented with row of spinules along outer margin; exp-2 with two terminal unipinnate and two outer bare setae. Endopod 1.7 times as long as exopod; enp-1 elongate, bare, 7 times as long as wide; enp-2 with two apical setae and ornamented with row of spinules along inner margin.

P2–P4 ( Fig. 3B–D View FIGURE 3 ), basis with 1 pinnate outer seta. Exopod three-segmented; exp-1 with one outer spine; exp- 2 inner distal corner forming spinous projection and with one outer spine; exp-3 with one long apical seta and one outer spine. Endopod absent.

Armature formula as follows:

P5 ( Fig. 1D View FIGURE 1 ). Baseoendopods confluent, forming large plate, exopod fused with baseoendopod, with one outer basal pinnate seta proximally; endopodal lobe with distinct concave shape with two naked setae; exopod represented by weak protrusion near basal seta, armed with two naked and one pinnate setae.

Description of male (paratype). Smaller and more slender than female. Body ( Fig. 4A View FIGURE 4 ) length 510 µm (n=7, mean = 519 µm). Largest width measured near middle of 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, P5, and P6.

Antennule ( Fig. 4B View FIGURE 4 1 –B View FIGURE 1 3 View FIGURE 3 ), six-segmented, short, robust, chirocer; segment-5 swollen, largest; Armature formula: 1–[0], 2–[8+1 pinnate], 3–[10], 4–[2], 5–[5+1 pinnate+(1+ae)], 6–[11+acrothek], apical acrothek consisting of aesthetasc fused basally to two slender, naked setae.

P5 ( Fig. 4D View FIGURE 4 ), conical, with medially fused baseoendopods. Baseoendopod and exopod fused, with four pinnate setae along outer margin.

P6 ( Fig. 4E View FIGURE 4 ), both legs distinct, represented by thin plate; armature consisting of one bare longest and two short pinnate setae.

Caudal rami ( Fig. 4C View FIGURE 4 ), juxtaposed, about 2.5 times as long as wide, conical, distal margin acutely pointed; each ramus armed with seven setae; seta I bare, short and located ventrally; seta II bare; seta III and IV pinnate; seta V longest, bare; seta VI short, bare and located sub-apically; seta VII bi-articulated, pinnate, and inserted on short peduncle.

Etymology. The specific name refers to the type locality.

Remarks. The new species Apodopsyllus gwakjiensis is most closely related to A. bermudensis Coull & Hogue, 1978 on account of seta formula of A2 exopod, P1 basis without outer seta, and P1 enp-1 longer than exopod. However, the new species is clearly distinguished from the congener by the combinations of characters: 1) concave shape of baseoendopod with two bare setae (baseoendopodal plate of A. bermudensis is confluent, without seta), 2) P4 basis without any elements at the endopodal location, while A. bermudensis armed with a minute spinule at that location. Other differences appear in the mouth parts, for example, A. gwakjiensis has a onesegmented mandibular exopod with four setae, while A. bermudensis has a two-segmented exopod in mandibular palp, and exp-1 with one seta. Nearly all species of Paramesochridae have a one-segmented exopod on the mandibular palp.