Henicoxiphium redactum Illg & Humes, 1971

Kim, Il-Hoi & Boxshall, Geoff A., 2021, Copepods associated with Ascidian hosts (Tunicata): Intramolgidae and Lichomolgidae, with descriptions of four new genera and 13 new species, Zootaxa 5013 (1), pp. 1-75 : 16-20

Henicoxiphium redactum Illg & Humes, 1971

( Figs. 9–11 )

Material examined. 2 ♀♀ 1 ♂ (MNHN-IU-2017-2141) (1 ♀ and 1 ♂ dissected) from myura lẚgnosa Michaelsen , 1908, Anse Noire, Martinique Island (14°32´N, 61°05.3´W), MADIBENTHOS Expedition, Stn AR 100, depth 2-8 m, 06 September 2016 .

Supplementary description of female. Body ( Fig. 9A ) with weak exoskeleton. Body length 1.50 mm; maximum width 552 μm. Prosome moderately expanded, 825 μm long. Urosome ( Fig. 9B ) 5-segmented; fifth pediger- ous somite 142 μm wide. Genital double-somite longer than wide (245×180 μm), rhomboidal, widest at proximal third; genital apertures located at mid-length of double-somite. Three free abdominal somites 71×77, 67×72, and 80×67 μm, respectively. Caudal ramus ( Fig. 9C ) large, about 5.6 times longer than wide (268×48 μm) and more than 3 times longer than anal somite: armed with 6 naked setae; outer lateral seta (seta II) located at about 36% of ramus length; seta VII positioned dorsally near seta II at about 42% of ramus length. Egg sac ( Fig. 9D ) 608×196 μm, tapering distally; each egg about 72 μm in diameter.

Rostrum ( Fig. 9E ) semicircular. Antennule ( Fig. 9F ) slender, 7-segmented; armature formula 4, 13, 6, 3, 4+aesthetasc, 2+aesthetasc, and 7+aesthetasc; all setae naked. Antenna ( Fig. 9G ) 3-segmented, consisting of coxobasis and 2-segmented endopod; coxobasis with 1 small seta distally on inner margin; proximal endopodal segment elongate with 1 minute seta on inner margin and row of spinules along outer margin; distal endopodal segment about 2.56 times longer than wide (64×25 μm), formed by fusion of original second and third endopodal segments, armed with 4 small setae proximally on inner margin, 5 small setae distally and subdistally, plus 2 large, unequal distal claws; longer claw 67 μm long, shorter 45 μm; one distal seta apparently inserted proximally on longer claw.

Labrum ( Fig. 9H ) deeply incised with broad posterior lobes. Mandible ( Fig. 9I ) with slender blade bearing several rows of spinules on convex outer surface and 1 row of setules along concave inner margin; forming elongate lash distally. Maxillule ( Fig. 9J ) as elongate lobe tipped with 2 unequal, naked setae. Maxilla ( Fig. 9K ) 2-segmented; proximal segment (syncoxa) unarmed; distal segment (basis) with extremely thin, elongate distal lash, and armed with 2 setae (minute inner seta and slightly expanded anterior seta); distal lash forming right angle with basis, ornamented with about 15 large spinules along proximal third of outer margin and minute spinules along distal twothirds of outer margin; inner margin of lash smooth. Maxilliped ( Fig. 9L ) 3-segmented; all segments unarmed; third segment small, tapering.

Legs 1–4 with 3-segmented rami ( Fig. 10 A-E). Inner seta on coxa of leg 4 small. Outer seta on basis of legs 1-4 naked. Armature formula for legs 1–4 as follows:

Coxa Basis Exopod Endopod

Leg 1: 0-1 1-0 I-0; I-1; III, I, 4 0-1; 0-1; I, 1, 4

Leg 2: 0-1 1-0 I-0; I-1; III, I, 5 0-1; 0-2; I, II, 3

Leg 3: 0-1 1-0 I-0; I-1; III, I, 5 0-1; 0-2; I, II, 2

Leg 4: 0-1 1-0 I-0; I-1; II, I, 5 0-1; 0-1; 0, I, 0

Leg 5 consisting of dorsolateral seta on fifth pedigerous somite and free exopod; exopod ( Fig. 10F ) broadening distally, about 1.5 times longer than wide (35×23 μm), with roundly expanded inner distal corner: armed with 2 spiniform setae distally; small inner seta 13 μm long; longer outer seta 42 μm long, slightly broadened in middle. Leg 6 ( Fig. 10G ) represented by 2 unequal setae and 1 spiniform process on genital operculum.

Description of male. Body ( Fig. 11A ) similar to that of female, 1.05 μm long; prosome 556×360 μm. Urosome ( Fig. 11B ) 6-segmented: fifth pedigerous somite 93 μm wide; genital somite 170×148 μm, with rounded corners; 4 abdominal somites 48×59, 45×55, 36×48, and 45×49 μm, respectively. Caudal ramus about 5.56 times longer than wide (150×27 μm), with same form as female.

Rostrum as in female. Antennule with 3 additional aesthetascs: 2 on second and 1 on fourth segments, at sites indicated by dots in Fig. 9F . Antenna as in female.

Labrum, mandible, maxillule, and maxilla as in female. Maxilliped ( Fig. 11C ) 4-segmented; first and third segments unarmed; second segment with convex inner margin bearing 1 stiff seta; fourth segment forming strongly curved, elongate claw bearing 1 large and 1 minute seta proximally.

Legs 1-4 as in female. Leg 5 exopod ( Fig. 11D ) about 1.5 times longer than wide (23×15 μm), armed distally with 2 very unequal setae, 8 and 36 μm long. Leg 6 represented by 2 equal, naked setae at posterolateral corners of genital somite ( Fig. 11B ).

Remarks. eenẚcoxẚphẚum redactum has not been reported since its original description by Illg & Humes (1971). In contrast to the original description, our dissected female is 1.50 mm long, distinctly larger than type specimens which were 1.05 to 1.29 mm long; the maxillule is armed with 2 setae compared with 3 setae in the type specimens; the distal endopodal segment of the antenna has 4 proximal inner setae, compared to 3 setae in the type specimens; and the exopod of male leg 5 is 23×15 μm, distinctly broader than that of type specimens (recorded as 23×9 μm). We consider that these differences can be attributed to infraspecific variability, because numerous taxonomically important features of our material, such as the characteristic forms of the caudal ramus, maxillule, and exopod of female leg 5, and the characteristic positions of caudal setae, are shared with the type specimens.

Genus Lichomolgidium Kossmann, 1877

Remarks. The genus iẚchomolgẚdẚum currently consists of three known species. The type species i. sardum Kossmann, 1877 is redescribed here and a new species is described below. The major key characters of this genus include; the maxilliped is 2-segmented, the mandible lacks a distal lash, and the inner seta (seta I) on the basis of the maxilla is absent or rudimentary.

Figures

FIGURE 9. eenẚcoxẚphẚum redactum Illg and Humes, 1971, female.A, habitus, dorsal; B, urosome, dorsal; C, anal somite and caudal rami, dorsal; D, egg sac; E, rostrum; F, antennule; G, antenna; H, labrum; I, mandible; J, maxillule; K, maxilla; L, maxilliped. Scale bars: A–D, 0.1 mm; E, F, H, 0.05 mm; G, I–L, 0.02 mm.

FIGURE 10. eenẚcoxẚphẚum redactum Illg and Humes, 1971, female. A, leg 1; B, leg 2; C, endopod of leg 3; D, leg 4; E, endopod of leg 4; F, exopod of leg 5; G, right genital aperture, dorsal. Scale bars: A–D, 0.05 mm; E–G, 0.02 mm.

FIGURE 11. eenẚcoxẚphẚum redactum Illg and Humes, 1971, male. A, habitus, dorsal; B, urosome, dorsal; C, maxilliped; D, exopod of leg 5. Scale bars: A, B, 0.1 mm; C, D, 0.02 mm.