Apanthura laevipedata, Kim & Yoon, 2021

Kim, Sung Hoon & Yoon, Seong Myeong, 2021, Four new species of isopods (Crustacea, Isopoda) from South Korea, ZooKeys 1010, pp. 133-164 : 133

Apanthura laevipedata sp. nov. Figures 5 , 6 , 7

Material examined.

Holotype. South Korea • 1 non-ovigerous ♀ (5.5 mm); Jeju-do, Seogwipo-si, Beophwan-dong; 33°13'36"N, 126°32'12"E; 33 m; 26 Apr. 2018; Smith-McIntyre grab; NIBRIV0000862805.

Paratypes. 4 ♀♀, same data as for holotype; 2 ♀♀, same locality as for holotype; 1 Feb. 2018; 2 ♀♀; Jeju-do, Seogwipo-si, Seohong-dong; 33°13'48"N, 126°33'06"E; 51 m; 26 Apr. 2018; Smith-McIntyre grab • 1 juvenile ♀; Jeju-do, Seogwipo-si, Donghong-dong; 33°13'48"N, 126°34'36"E; 59 m; 26 Apr. 2018; Smith-McIntyre grab; NIBRIV0000880421.

Etymology.

The specific name, Apanthura laevipedata , originates from the combination of the Latin words laevis, meaning smooth and pedis, meaning foot. This name refers to having the propodus of pereopod that is smooth, not stepped.

Description of holotype female.

Body (Fig. 5A, B ) smooth and slender, 5.5 mm in length, 11 × longer than wide. Cephalon square, 0.7 × as long as pereonite I; rostrum extending as long as anterolateral lobes; eye absent. Pereonites oblong; pereonites I-III similar in length; pereonites IV-VI longer than previous three pereonites, subequal each other in length; pereonite VII ~ 0.7 × as long as pereonite VI; coxal plates of pereonites V-VII visible dorsally. Pleonites I-V not separated by folds dorsally and laterally; pleonite VI with middorsal notch posteriorly.

Antennule (Fig. 5C ) consisting of three peduncular and three flagellar articles. Peduncular article I oblong, longer than wide, with three penicillate setae and one simple seta along lateral margin; article II square, ~ 0.5 × as long as article I, with three penicillate setae on distal end; article III similar to article II in length, slender than article II, with one penicillate seta and three simple setae distally. Flagellar article I much shorter than other articles, 0.1 × as long as peduncular article III; article II oblong to oval, tapering distally, 0.8 × as long as peduncular article III; article III square to globular, 0.3 × as long as article II, with two simple setae and two aesthetascs distally.

Antenna (Fig. 5D ) longer than antennule, composed of five peduncular and three flagellar articles. Peduncular article I rectangular to globular, with one simple seta distally; article II 1.5 × longer than article I; article III oblong, 0.4 × as long as article II, with three simple setae distally; article IV similar to article III in shape, 0.7 × as long as article III, with four simple setae distally; article V elongated oblong, 2.3 × longer than article IV, with three penicillate and four simple setae on distal end. Flagellar article I elongated rectangular, ~ 0.5 × as long as peduncular article V; articles II and III minute, with several simple setae on distal end.

Mandible (Fig. 5E ), incisor with one cusp; molar process blunt; palp article I elongated oblong, with two simple setae distally; article II 1.4 × longer than article I, slightly thicker than other articles; article III slander, slightly tapering distally, 0.4 × as long as article II, with two short simple setae distally.

Maxilla (Fig. 5F ) with six irregular teeth distally and fine setae laterally.

Maxilliped (Fig. 5G ), epipods globular; endite slightly exceeding distal end of fused palp articles I and II, tapering distally, with one simple seta distally; palp articles I and II fused, rectangular, with one simple seta distally and one simple seta laterally; article III free, almost square, with three simple setae on distal end; articles IV and V fused, triangular, much smaller than other palp articles, with five simple setae along inner margin.

Pereopod I (Fig. 6A ) basis as long as ischium, gradually tapering proximally; ischium rectangular, with one simple seta on inferodistal angle; merus 0.4 × as long as ischium; superior margin of merus extending upwardly, with five simple setae on inferior margin, one short simple seta on superior margin, and one simple seta on mesial margin; carpus triangular, with five simple setae along inferior margin; propodus not stepped on palm, with two rows of simple setae along inferior margin and several fine setae on superior margin; dactylus oblique, with five simple setae; unguis slightly longer than dactylus; much longer than other pereopods, with accessory unguis distally. Pereopods II - VII (Fig. 6B-G ) basis oblong to oval, with several simple setae and penicillate setae on superior margin and one simple seta on inferodistal angle; ischium subequal in length, gradually tapering proximally, with several simple setae along with inferior margin and none or one simple seta on superodistal angle; merus tapering proximally, with several simple setae on inferior margin and 1-3 simple setae on superior margin; carpus of pereopods II and III triangular, with several simple setae on inferior margin without stout seta on inferodistal angle; carpus of pereopods IV-VII subsquare to globular or trapezoidal, with one stout seta on inferodistal angle, several simple setae on both lateral margins, none or one penicillate seta on superior margin; propodus slightly elongate and oval, with several simple setae on both lateral margins and one stout seta on inferodistal angle; dactylus slender, with several simple setae distally, unguis, much shorter than dactylus, with minute accessory unguis on distal end.

Pleopods (Fig. 7A-E ), protopod square to rectangular; rami subequal in length, rounded distally. Pleopod I (Fig. 7A ), protopod with three coupling hooks on inner margin; exopod 2 × wider than endopod. Pleopods II-V (Fig. 7B-E ), exopod with one simple seta on outer margin; pleopods III-V with notch on outer margin.

Uropod (Fig. 7F, G ), protopod oblong, 1.7 × longer than wide, with three plumose setae on each lateral margin; endopod triangular to oval, with one penicillate seta and 16 simple setae along outer margin; exopod oval, with numerous plumose and several simple setae along outer margin, not sinuous distally.

Pleotelson (Fig. 7H ) 2.6 × longer than wide, with two statocysts dorsally; lateral margins parallel; apex rounded, tapering distally, with two simple setae distally.

Distribution.

Southern coast of Jeju-do in South Korea.

Habitat.

Sublittoral zone of sandy bottom.

Remarks.

Apanthura laevipedata sp. nov. differs from its congeners by the following features combined: (1) the integument is not pigmented; (2) the eyes are lacking; (3) pleonites I-V are not separated by folds dorsally and laterally; (4) the propodal palm of pereopod I is not stepped; and (5) the uropodal exopod is not sinuous.

Besides the new species, four species that have no eyes are known in the genus Apanthura Stebbing, 1900: A. insignifica Kensley, 1978; A. tyrrhenica Wägele, 1980; A. drosera Poore & Lew Ton, 1985; and A. fusei Nunomura, 1993 ( Kensley 1978; Wägele 1980; Poore and Lew Ton 1985; Nunomura 1993). Among these species, Apanthura laevipedata sp. nov. is most similar to A. fusei in terms of dorsally fused pleonites I-V and not sinuous uropodal exopods. However, the new species is easily distinguished from the latter by not stepped propodal palm of pereopod I (vs. stepped in the latter), upwardly extending carpus (vs. not extending in the latter), laterally invisible suture in pleonites I-V (vs. visible in the latter), and parallel lateral margins of the pleotelson (vs. proximally concave lateral margins in the latter) ( Nunomura 1993). The new species also differs from A. drosera in having not stepped propodal palm of pereopod I (vs. stepped in the latter) ( Poore and Lew Ton 1985), while can be distinguished from A. insignifica and A. tyrrhenica in that all pleonites are not separated by folds (vs. separated in the latter species) ( Kensley 1978; Wägele 1980).

Figures

Figure 5. Apanthura laevipedata sp. nov., holotype, female A habitus, dorsal view B habitus, lateral view C antennule D antenna E mandible F maxilla G maxilliped.

Figure 6. Apanthura laevipedata sp. nov., holotype, female A pereopod 1 B pereopod 2 C pereopod 3 D pereopod 4 E pereopod 5 F pereopod 6 G pereopod 7.

Figure 7. Apanthura laevipedata sp. nov., holotype, female A pleopod 1 B pleopod 2 C pleopod 3 D pleopod 4 E pleopod 5 F uropodal exopod G uropodal endopod H pleotelson.