Asterocheres simulans
Creators: name: Kim, Il-Hoi
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Copepoda
Siphonostomatoida
Asterocheridae
Asterocheres
Asterocheres simulans

description: Asterocheres simulans (T. Scott, 1898) (Figs. 16-18)   
 Ascomyzon simulans T. Scott, 1898, p. 270, pl. 13, figs. 1-9. pl. 14, fig. 22; G.O. Sars, 1914, p. 89, pl. 55.   
 Asterocheres simulans: Giesbrecht, 1899, pp. 70, 115, 119; Ivanenko, 1997, p. 1119, figs. 1-6.   
 Material examined. 11$$, 1 damaged ♂ from an unidentified sponge, off Gisamun Port (38°00′30″N, 128° 43′51″E), in Yangynag on the eastern coast of Korea, in the depth of about 10 m, 23 September 2006.   
 Female. Body (Fig. 16A) 1.08 mm long in dissected and figured specimen. Mean body length 0.90 mm (0.80­1.08 mm), based on 9 specimens. Prosome oval, 738 μm long. Cephalothorax 453 × 585 μm, with angular posterolateral corners. Three metasomites with rounded posterolateral corners. Urosome (Fig. 16B) 4­segmented, tapering posteriorly. Fifth pedigerous somite 181 μm wide, tapering laterally, with spinules on dorsal surface. Genital double­somite 154× 177 μm, gradually tapering distally, with scales scattered on posterior half of dorsal surface, and about 30 stiff setules on lateral margin posterior to genital aperture (Fig. 17G). Genital aperture located dorsolaterally at 0.43 region of double­somite length. First and second abdominal somites 50× 94 and 48 × 77 μm, respectively, with scales on dorsal surface. Anal somite (second abdominal somite) with smooth posterior margin. Caudal ramus short, 21 × 30 μm, 1.43 times as wide as long, with 6 setae and smooth distal margin. Setae IV and V longer than urosome.   
Rostrum indistinct, without posterior apex (Fig. 17C). Antennule (Fig. 16D) 21­segmented, 458 μm long; armature formula 2, 2, 2, 2, 2 / 2, 2, 2, 7, 2 / 2, 2, 2, 2, 2 / 2, 2, 2 + aesthetasc, 2, 4, and 7; first segment with long setules on anterior margin; several setae on proximal segments plumose. Antenna (Fig. 16E) with short, unarmed coxa. Basis 103 μm long, with longitudinal row of minute pectens along distal 3/5. Exopod small, 10 × 6 μm, with 1 lateral and 2 unequal, distal setae. Endopod 3-segmented; first segment 76 μm long, with setules on outer margin; short second segment with 1 small seta; terminal segment with 2 spiniform setae (inner one 36 μm long and outer one 33 μm long) and terminated by spiniform claw of 77 μm long.  
Oral cone (Fig. 16F) evenly tapering, 201 μm long, 88 μm wide proximally, extending to base of maxilliped, with paired lateral points subdistally. Mandible (Fig. 16G) consisting of stylet and palp. Stylet 188 μm long, with fine teeth at distal region. Palp 2­segmented; first segment 46 μm long, and second segment 16 μm long; 2 distal setae plumose, 187 and 97 μm long, respectively. Palp, together with longer seta, distinctly longer than stylet. Maxillule (Fig. 16H) bilobed. Inner lobe 83 × 22 μm, with 5 distal setae; lengths of these setae 96, 94, 77, 58, and 16 μm, respectively. Outer lobe 30 × 10 μm, with 4 distal setae of 103, 100, 64, and 33 μm long, respectively. Maxilla (Fig. 16I) 2­segmented; syncoxa with slender tube and row of minute spinules at proximal region; basis represented by claw bearing row of minute spinules in distal region. Maxilliped (Fig. 17A) 6­segmented. Syncoxa with 1 small seta near inner distal corner. Basis 130 × 46 μm, with spinules on outer margin. First to fourth endopodal segments with 2, 1, 1, and 1 setae, respectively; terminal segment 45 μm long; terminal claw 100 μm long, 2.2 times as long as terminal segment.  
Legs 1­4 (Fig. 17 B­E) with 4­segmented rami. Leg 4 with small, plumose inner seta on coxa, otherwise armature formula as typical for genus. Outer spines on exopod of leg 1 tipped with small setule, that of first segment 36 μm long.  
Leg 5 consisting of dorsolateral seta on fifth pedigerous somite and free exopod (Fig. 16B); exopod (Fig. 17F) 69 × 37 μm, 1.86 times as long as wide, and armed with 2 distal and 1 subdistal setae; lateral margins of exopod slightly convex and spinulose; 2 distal setae broadened proximally, plumose, 61 and 46 μm long, respectively; subdistal seta naked, 41 μm long. Leg 6 represented by 2 small setae on genital operculum (Fig. 17G).  
 Male. Urosome 5­segmented. Genital somite (Fig. 18A) 128 × 164 μm, wider than long, with few spinules on lateral margin. First to third abdominal somites 26 × 60, 19 × 53, and 26 × 50 μm, respectively. Caudal ramus 16 × 23 μm, 1.45 times as wide as long.   
Rostrum as in female. Antennule (Fig. 18B) 368 μm long, 18­segmented, and geniculate between sixteenth and seventeenth segments; armature formula: 2, 2, 2, 2, 2 / 2, 2, 2, 6, 2 / 2, 2, 2, 2, 2 / 4, 2 + aesthetasc, and 11; aesthetasc on penultimate segment relatively small, but extending over distal tip of terminal segment. Antenna as in female.  
Oral cone, mandible, maxillule, and maxilla as in female. Maxilliped similar to that of female, but its basis with prominent proximal process on inner margin (Fig. 18C).  
Leg 1 slightly different from that of female in having more acutely pointed outer and inner distal processes on third endopodal segment (Fig. 18D). Legs 2­4 as in female.  
Leg 5 exopod (Fig. 18E) rectangular, 2.89 times as long as wide, with parallel lateral margins. Leg 6 represented by 2 distal plumose setae on genital operculum (Fig. 18A).  
 Remarks. Ivanenko (1997) redescribed this species, based on the specimens from the White Sea. A careful comparison of Korean specimens with Ivanenko’s illustrations resulted in that the forms from the two different zoogeographic regions revealed no significant differences. The length combinations of setae on the lobes of the maxillule are, in particular, almost identical between them. The presence of a row of setules on the medial margin of the genital operculum in the male from the White Sea, which is absent in the male from the Sea of Japan, is not considered important to differentiate them on the species level.
description: Published as part of Kim, Il-Hoi, 2016, Siphonostomatoid copepods (Crustacea) mainly associated with marine invertebrates from Korean waters, pp. 393-442 in Journal of Species Research 5 (3) on pages 416-420, DOI: 10.12651/JSR.2016.5.3.393, http://zenodo.org/record/13146750