Doropygus kerguelensis Schellenberg, 1922

Kim, Il-Hoi & Boxshall, Geoff A., 2020, Untold diversity: the astonishing species richness of the Notodelphyidae (Copepoda: Cyclopoida), a family of symbiotic copepods associated with ascidians (Tunicata), Megataxa 4 (1), pp. 1-6 : 319-323

Doropygus kerguelensis Schellenberg, 1922

( Figs. 211–213 )

Material examined. 2 ♀♀ (MNHN-IU-2018-1850) and 1 dissected ♀ from Molgula sp., Subantarctic (49°14 Ń, 67°48 É), depth 202-208 m, 21 September 2010; 12 ♀♀ (MNHN-IU-2018-1851) and dissected 3 ♀♀, 1 ♂ from Ascidia meridionalis Herdman, 1880 , Subantarctic (48°48 Ń, 70°09 É), depth 103-104 m, 04 September 2010; 1 ♀, 1 ♂ (MNHN-IU-2018-1852) and 1 dissected ♀ from Molgula macquariensis Kott, 1954 , Kerguelen MD 04 Stn A3D6; 1 ♀, 2 ♂♂ (MNHN-IU-2018-1853) from M. macquariensis, Kerguelen ; 1 ♀, 1 ♂ (MNHN-IU-2009-5183) and 1 dissected ♀ from M. pedunculata Herdman, 1881 , POKER III, Stn CE06-049B = 31 (48°430 Ś, 67°585 É), depth 212 m; 1 ♀ (MNHN-IU-2009-5154) and 1 dissected ♀ from M. pedunculata, POKER III, Stn 133 (46°935 Ś, 68°820 É), depth 665 m = 665-706 m; 5 ♀♀, 5 ♂♂ (MNHN-IU-2009-5185) and dissected 1 ♀, 1 ♂from Molgula sp., POKER III, Stn CE06.163 = 167 (51°88 Ś, 70°675 É), depth 382 m; 11 ♀♀, 6 ♂♂ (MNHN-IU-2009-5186) from Molgula sp., POKER III, Stn CE06.048 = 30 (48°397 Ś, 67°338 É), depth 385 m; 15 young ♀♀, 30 ♂♂ (MNHN-IU-2009- 5187) and 1 dissected young ♀ from Molgula sp., POKER III, Stn CE06-039A (47°986 Ś, 67°154 É), depth 487 m; 2 ♀♀ (MNHN-IU-2009-5715) from Molgula pedunculata, POKER III, Stn CE 06-133; 1 ♀, 3 ♂♂ (MNHN-IU-2009-5717) from Molgula sp., POKER III, Stn CE06-119 (46°224 Ś, 68°600 É), depth 165 m; 37 ♀♀, 3 ♂♂ (MNHN-IU-2009-5718) from M. pedunculata, Expedition MD 03, Navire Oceanographique “Marion Dufresne”, Stn 2-7- CB 02 (49°33 Ś, 70°47 É), depth 130 m, 04 April 1974; 12 ♀♀ (MNHN-IU-2009-5719) from M. pedunculata, MD 42/ SIBEX, Stn 001, Mola 251 (51°15.0 Ś, 71°41.2 É), depth 285 m, 12 January 1985; 8 ♀♀, 8 ♂♂ (MNHN-IU-2009-5720) from Molgula sp., POKER III, Stn CE06-059 (48°606 Ś, 67°44 É), depth 220 m; 1♀, 8 young ♀♀, 10♂♂ (MNHN-IU-2009- 5721) from M. pedunculata, POKER III, Stn CE 06-040 = 25 (48°751 Ś, 67°010 É), depth 331 m; 4 ♀♀, 12 ♂♂ (MNHN-IU-2009-5729) from M. pedunculata, MD 42/ SIBEX, Stn.?, MolA 251 (51°15.0 Ś, 71°41.2 É), depth 285 m, 12 January 1985; 4 ♀♀, 12 ♂♂ (MNHN-IU-2009- 5730) from M. pedunculata, Pridz Bay, Stn 22-CP70, (67°000 Ś, 73°372 É), depth 490 m.

Supplementary description of female. Body ( Fig. 211A )narrow,slightlydepressed,3.85mmlong.Metasome obscurely 4-segmented with fourth pedigerous somite forming bulbous brood pouch, largely incorporating fifth pedigeroussomite. Freeurosome ( Fig. 211B ) slender, 5- segmented: genital somite 160×364 μm, shorter than other urosomites; 4 abdominalsomites 314×345, 258×308, 215×258, and 185×234 μm, respectively. Caudalramus ( Fig. 211C ) elongate, about 6.3 timeslongerthan wide (406×65 μm) and about twice as long as anal somite; armed with 6 small setae; all caudal setae shorter than width of caudal ramus; 2 proximal setae located at 26 and 65% of ramus length.

Coxa Basis Exopod Endopod
Leg 1	0-1	1-I	I-1; I-1; III, I, 40-1; 0-1; 1, 2, 3
Legs 2 & 30-1		1-0	1-1; 1-1; 3, 1, 50-1; 1, 2, 5
Leg 4	0-1	1-0	1-0/1; 1-1; 3 0-1; 1, 2, 4
			(or 2), 1, 5

Rostrum ( Fig. 211D ) longerthanwide, tapering towardsroundedapex. Antennule ( Fig. 211E ) 440 μm long, 9-segmented; proximal segments weakly expanded; armatureformula 3, 17, 6, 4+aesthetasc, 4, 3+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; mostof largesetaepinnate with setules perpendicular to long axis of seta. Antenna ( Fig. 211F ) slender, 4 segmented; shortcoxa unarmed; basis about twice as long as wide, with small (exopodal) knob tipped by 2 vestigial setae at outer distal corner and 1 small seta at inner distal region; first endopodal segment 1.5 times longer than wide, with 1 seta on inner margin; compound distal endopodal segment twice as long as first and4.4 times longerthan wide (180×41 μm); armed with 10 small setae (3 distal setae blunt at tip) and ornamented with minute spinules on outer margin; terminal claw small, less than half length of segment.

Labrum ( Fig. 211G ) densely setulose posteriorly and with large setulose posteromedian lobe. Mandible ( Fig. 211H ) with 5 teeth on coxal gnathobase; basis with 1 seta onmedial margin; exopod 4-segmented with 1, 1, 1, and 2 setae on first to fourth segments, respectively, distalmost seta slightly shorter than other 4; first endopodal segment fused with or indistinctly articulated from basis and armedwith 4 setae medially; ornamented withrow of spinules at outer distal corner and patch of minute spinules ventrodistally; second endopodal segment with 10 setae. Maxillule ( Fig. 211I ) with 9 setaeon arthrite, 1 on coxal endite, 2 on epipodite, 3 on basis, 4 on exopod and 3 on endopod. Maxilla ( Fig. 212A ) 5-segmented; syncoxa with 3, 1, 2, and 3 setae on first to fourth endites, respectively; basiswith 3 setae; endopodwith 1, 1, and 4 setae on first to third segments, respectively; 2 of 4 setae on third endopodal segment naked, one half length of other. Maxilliped ( Fig. 212B ) unsegmented, armedwith 9 medial setae and 2 apical setaeon short, narrow distal part; oramented with tuft of setules proximally.

Leg 1 ( Fig. 212C ) with 3-segmented rami; innerdistal spine on basis 90 μm long, extending to distal border of second endopodal segment; outer margin of first exopodal segment slightly notched at distal third; first outer spine of exopod 88 μm long, twice as long as second and third outer spines. First exopodal segment of leg 4 lacking inner seta in some specimens; third exopodal segment armed with 9 or occasionally 8 setae (in case of 8 setae, first outer seta may be lost, this seta indicated by an arrowhead in Fig. 212E ). Armature formula for legs 1–4 as follows:

Leg 5 ( Fig. 212F ) with broad protopod bearing extremely thin outer seta and row of spinules at inner distal corner; free exopodal segment about 2.6 times longerthan wide (179×69 μm), armedwith 1 short seta and 1 longer seta distally and ornamented with 4 rows of minute spinules on dorsomedial surface.

Descriptionofmale. Body ( Fig. 213A ) slender, 1.98 mm long. Cephalosome much broader than remaining part of body. Urosome 6-segmented: first to third free abdominal somites longer than wide; other 3 urosomites widerthan long. Caudal ramus about 6.4 times longer than wide (212×33 μm) and 2.2 timeslongerthan anal somite.

Rostrum, antennule, antenna, and all mouthparts as in female. Armature formula for legs 1–3 also as in female. First exopodal segment of leg 4 ( Fig. 213B ) with or without inner seta, as in female; third exopodal segment of leg 4 with 8 setae (formula 2, 1, 5).

Leg 5 ( Fig. 213C ) armed and ornamented as in female. Exopodal segment about 3.2 timeslongerthan wide (92×29 μm). Leg 6 represented by 2 naked setae on genital operculum.

Remarks. Doropygus kerguelensis was originally described as D. trisetosus var. kerguelensis ( Schellenberg, 1922) but later raised to species level ( Sewell, 1949; Illg, 1958). The key features of Schellenberg’s brief description included the following: (1) the caudal ramus is twice as long as the anal somite; (2) the fifth seta on the mandibular exopod is shorter than the fourth; (3) the endopod of the maxillule bears 3 setae; (4) the first outer seta on the exopod of leg 1 is twice as long as the second and third; (5) the second and third outer setae on the exopods of legs 2–4 are about twice as long as the third exopodal segment; (6) the free exopodal segment of leg 5 is 2.5 timeslongerthan wide and has 4 indentations on the inner margin.All of these features are exhibited by our examined specimens, which are therefore identified as D. kerguelensis .

It is interesting to note that the basis of the antenna carries a small knob tipped with 2 vestigial setae at its outer distal angle. This structure is here interpreted as a vestige of the antennal exopod. Asimilar structure is present in the same position on the distal margin of the basis in D. globosus , although it somewhat resembles a bifurcate seta.

Figures

FIGURE 211. Doropygus kerguelensis Schellenberg, 1922, female.A, habitus, left; B, urosome, ventral; C, left caudal ramus, dorsal; D, rostrum; E, antennule; F, antenna; G, labrum; H, mandible; I, maxillule. Scale bars: A, 0.5 mm; B, 0.2 mm; C–F, H, 0.1 mm; G, I, 0.05 mm.

FIGURE 212. Doropygus kerguelensis Schellenberg, 1922, female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, leg 4; F, leg 5. Scale bars: A, B, 0.05 mm; C–F, 0.1 mm.

FIGURE 213. Doropygus kerguelensis Schellenberg, 1922, male. A, habitus, right; B, leg 4; C, leg 5. Scale bars: A, 0.2 mm; B, C, 0.05 mm.