Caecijaera ciliata, Kim & Kim & Yoon, 2022

Kim, Sung Hoon, Kim, Jong Guk & Yoon, Seong Myeong, 2022, Description of two new janirid isopods (Isopoda, Asellota, Janiridae) from Korean waters, Zootaxa 5178 (6), pp. 532-546 : 534-538

Caecijaera ciliata sp. nov.

Figs 1–3

urn:lsid:zoobank.org:act:2702B996-A91A-4560-B7B6-23DD00CEED0D

Material Examined. Holotype: ♂, Chubongdo Island (34°45′40″N, 128°30′40″E), Chubong-ri, Tongyeong-si, Korea, 26 October 2019, dead wood lying on sandy beach during ebb tide, NIBRIV0000897186.

Paratypes: 2 ♂♂, 10 ♀♀, same data as holotype, NIBRIV0000876680 .

Additional material: Bakdo Island (34°40′57″N, 128°03′34″E), Mijo-ri , Mijo-myeon, Namhae-gun, Gyeongsangnam-do, Korea, 1 November 2020, 10 m, SCUBA diving, dead wood .

Diagnosis. Cephalothorax rounded laterally, expanding anterolaterally; pereonites 4–7 with 3–5 large simple setae on midline of posterior tergite margins; pleotelson proximolateral margin angled; antennula 6-articled; mandibular molar process greatly reduced; basis of pereopod VII with distodorsal margin serrated. Males, pleopod Ⅰ with 1 pair of indistinct distolateral lobes; pleopod II with distally truncated protopod; appendix masculina not coiled, not exceeding beyond protopod of pleopod II.

Description of holotype male. Body ( Fig. 2A ) 1.8 mm, elongated oval while widest in pereonite 6; length 1.8 times width; body surface smooth, covered with numerous simple setae dorsally. Cephalothorax broadly oval; 0.4 times as long as wide; anterior margin convex on mesial region, rounded distally; lateral margin rounded with numerous simple setae. Pereonites ( Fig. 2B ) wider than long, widest, with numerous simple setae marginally and rounded edge; posterior margins of pereonites 1–3 convex while pereonites 5–7 concave; pereonites 4–7 with 3–5 large simple setae on midline of posterior tergite margins; pereonite 6 widest. Pleon ( Fig. 2C ) comprised of 1 free pleonite and fused pleotelson; pleonite 1 enclosed by pereonite 7 and pleotelson; pleotelson roughly semicircular, angled proximolaterally, with numerous simple setae laterally and 1 pair of distinct concavities distally; caudomedial lobe rounded distally, with 2 simple setae.

Antennula ( Fig. 2D ) reaching distal end of peduncular article VI of antenna, about 0.6 times as long as antenna, 6-articled, composed of 3 peduncular articles and 3 flagellar articles; peduncular article Ⅰ enlarged, expanding anteromedially, with short simple setae dorsally and long simple setae laterally; article II oblong, about 0.5 times as long as article Ⅰ, with short simple setae dorsally, 4 simple setae and 1 penicillate seta distally; article III square, 0.5 times as long as article II, with 1 long simple seta distally; flagellar articles oblong; article Ⅰ with 2 simple setae distally, article II with 1 aesthetasc distally; article III with 1 aesthetasc and 3 simple setae distally. Antenna ( Fig. 2E ) 0.3 times as long as body, consisting of 6 peduncular articles and 19 flagellar articles; peduncular article Ⅰ extending laterally with simple setae laterally; article II without setae, with serrated medial margin; article III with 3 simple setae and distinct scale on lateral margin; scale oblong, rounded distally, 1.5 times longer than article III, with simple setae marginally and dorsally; article IV 0.8 times as long as article III, with 4 simple setae distally; article Ⅴ square, 1.7 times longer than article IV, with 8 simple setae distally; article VI oblong, 1.2 times longer than article Ⅴ, with 18 simple setae distally; flagellar articles sequentially narrowing towards distally, with several simple setae distally on all articles; flagellar article Ⅰ longest.

Left Mandible ( Fig. 3A ), molar process reduced, situated close to incisor, with 4 cusps and 1 simple seta distally; incisor with 4 cusps; lacinia with 5 cusps; palp article Ⅰ similar to article II in length, without setae; article II with 2 serrate setae laterally; article III about 0.5 times as long as article II, with 7 serrate setae laterally. Maxillula ( Fig. 3B ), inner lobe with 8 serrate setae distally; outer lobe 1.3 times wider than inner lobe, with 5 stout setae distally. Maxilla ( Fig. 3C ), inner lobe with 5 serrate setae distally; mesial lobe with 4 serrate setae distally; outer lobe with 4 serrate setae distally. Maxilliped ( Fig. 3D ), endite expanding to distal end of palp article II, truncated distally, with 2 coupling hooks medially, 9 serrate setae and 16 simple setae distally; palp article Ⅰ oblong, 0.6 times as long as wide, with 1 simple seta proximally and 2 simple setae distally; article II square, with 4 simple setae laterally; article III subequal to article II in length, with 4 simple setae laterally and 1 simple seta distally; articles IV and Ⅴ distinctly narrower than preceding articles, with several simple setae distally; epipod triangular, 2.4 times longer than wide, reaching proximal region of palp article IV, tapering distally, with acute distal end.

Pereopods ( Fig. 3E–K ), basis serrated distodorsally in pereopod VII; ischium almost 0.6 times as long as basis; merus 0.6 times as long as ischium, abruptly narrowing proximally, with 2 robust simple setae on superior distal angle (1 robust simple seta in pereopod Ⅴ); carpus oblong, 1.5 times longer than merus, with 3–6 robust simple setae and 0–1 penicillate seta on distodorsal angle, 3–6 simple setae on distoventral angle; propodus oblong, subequal to carpus in length with 4–7 simple setae superiorly and 0–1 penicillate seta distodorsally, without setae on ventral margin except for pereopod Ⅰ (3 short simple setae distoventrally); dactylus distally with 1 large inwardly curved claw, 1 small claw distoventrally, and protrusion ventrally excepting pereopod Ⅰ.

Pleopod Ⅰ ( Fig. 4A, B ) 1.8 times longer than wide, tapering distally, with 1 pair of small and indistinct distolateral lobes; distal end truncated, with 7 pairs of simple setae distally, 5 pairs of simple setae subdistally; 5 pairs of subdistal simple setae arranged longitudinally. Pleopod II ( Fig. 4C ), protopod semicircular, truncated distally, with long simple setae distally and short simple setae laterally; endopod located on almost half length of protopod; exopod short and blunt distally; appendix masculina slender, tapering distally and reaching distal end of protopod. Pleopod III ( Fig. 4D ), endopod rounded distally, with 4 plumose setae distally, 0.9 times longer than wide; exopod with numerous simple setae laterally; first article of exopod 3.1 times longer than second article. Pleopod IV ( Fig. 4F ) uniramous, 1.5 times longer than wide, with rounded distal end. Pleopod Ⅴ lacking.

Uropod ( Fig. 4F ), protopod extended laterally, 1.5 times wider than long, with simple setae on mesial and distal margins; rami oval, subequal in length, rounded distally, about 0.6 times as long as protopod, with simple setae distally.

Paratype female. Female similar to males except for following characters. Pereonites 4–7 with large simple setae on midline of posterior tergite margins, but relatively shorter and more slender than in the males. Pleopod II ( Fig. 4G ) semicircular, tapering and rounded distally, with simple setae laterally and distally; distal setae longer than lateral setae.

Remarks. Kussakin (1962) suggested that the genus Caecijaera could be divided into two groups:the Caecijaera group with 6-articled antennula, greatly reduced mandibular molar process, and not coiled appendix masculina (incl. C. horvathi , C. cojimarensis , and C. kussakini ); and the Caecijaeralla group with 5-articled antennula, welldeveloped mandibular molar process, and long and coiled appendix masculina (incl. C. borealis , C. derjugini , and C. mirabilis ) ( Kussakin 1962; Cooke 1977; Svavarsson 1982; Malyutina 1994; Wilson & Wägele 1994; Ortiz 2020). According to this criterion, the new species can be nested within the Caecijaera group ( Menzies 1951a; Kussakin 1962; Malyutina 1994; Ortiz 2020). However, the new species differs from other members of the Caecijaera group by having large simple setae near the midline of the posterior tergite margins of pereonites 4–7 (vs. lacking large simple setae in pereonite VII), and proximolaterally angled pleotelson (vs. proximolaterally rounded) ( Menzies 1951a; Malyutina 1994; Ortiz 2020). The indistinct distolateral lobes of pleopod Ⅰ in males is a key to distinguishing the new species from the Hawaiian materials of C. horvathi (vs. long distolateral lobes).

Etymology. The specific name, ciliata , originates from the Latin word cilium, meaning “hair”. This name refers to the presence of several large simple setae along the posterior margins of pereonites 4–7. It is in the nominative singular; gender feminine.

Distribution. Korea (the Yellow Sea).

Figures

FIGURE 1. Map of the type localities of one Caecijaera and four Janiralata species reported in the surrounding waters of Korea. 1, C. ciliata sp. nov.; 2, J. truncata sp. nov.; 3, J. shiinoi; 4, J. sagamiensis; 5, J. chuni; 6, C. derjugin.

FIGURE 2. Caecijaera ciliata sp. nov., holotype male, NIBRIV0000897186. A, Habitus, dorsal view; B, Lateral margins of pereonites 4 and 5; C, Pleotelson, dorsal view; D, Antennula; E, Antenna. Scale bars: A = 0.5 mm, C–E = 0.2 mm.

FIGURE 3. Caecijaera ciliata sp. nov., holotype male.A, Mandible; B, Maxillula; C, Maxilla; D, Maxilliped; E–K, Pereopods Ⅰ–VII, respectively. Scale bars: A–K = 0.05 mm.

FIGURE 4. Caecijaera ciliata sp. nov., holotype male (A–F) and paratype female, NIBRIV0000876680 (G).A, C–E, Pleopods Ⅰ–IV, respectively; B, Distal end of pleopod Ⅰ; F, Uropod; G, Pleopod II. Scale bar: A, C–G = 0.2 mm, B = 0.05 mm.