Pachypygusbisetiger, Kim & Boxshall, 2020

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 : 132-135

Pachypygusbisetiger sp. nov.

( Figs. 86 , 87 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21243 ) , paratype (intact ♀, MNHN-IU-2014-21244), and dissectedparatype (♀, figured), from the compound ascidian Clavelina detorta (Sluiter, 1904) , lagoon, New Caledonia, B. Richer de Forges - ORSTOM coll.

Etymology. The specific name refers to the presence of the two setae on the third segment of the maxilliped.

Descriptionoffemale. Body ( Fig. 86A ) bilaterally compressed. Dorsal shield of cephalosome with short, broad posterolateral processes and convex dorsal protrusion. Dorsal tergites of first to third prosomites incompletely developed, with unsclerotized gaps between them. Third and fourth pedigerous somites forming brood pouch; fourth pedigeroussomite suboval. Urosome ( Fig. 86B ) 6-segmented, graduallynarrowing distally. Fifth pedigerous somite short, 90×242 μm, but well-defined from fourth pedigerous somite. Genital and 4 free abdominalsomites 155×215, 181×176, 167×158, and 121×124, and 67×94 μm, respectively. Anal somite ( Fig. 86C ) with highly sclerotized posteroventral protrusion and short dorsal margin. Caudal ramus ( Fig. 86C ) inserted dorsolaterally on anal somite, about 2.5 times longer than wide (114×45 μm), narrowing distally, and armed with 4 distal claws (1 large and 3 small) and 2 setae; lengths of claws 35, 20, 17, and 14 μm; setae as long as distal width of ramus, positioned at 56% and 75% of ramus length.

Rostrum ( Fig. 86D ) bulbous, narrowing proximally, widest in middle, rounded distally and with large pore at apex. Antennule ( Fig. 86E ) 9-segmented, secondsegment widest, more distal segments narrowing gradually; fifth segment subdivided by incomplete suture line on posterior side; armatureformula 3, 16, 5, 2+ 2 aesthetascs, 4, 2+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; all setae naked and most setae long. Antenna ( Fig. 86F ) stout, 4-segmented; coxaandbasisunarmed; firstendopodal segment slightly shorter than basis, with 1 seta on inner margin; compound distal endopodal segment slightly shorter than first, twice as long as wide (61×32 μm); armedwith 8 setae (grouped as 3, 2, and 3) plusterminal claw longerthan segment.

Labrum ( Fig. 86G ) with large semicircular posterolateral lobes ornamented with setules on outer marginand inner side; convex posteriormargin setulose. Mandible ( Fig. 86H ) with 6 teeth, including 4 blunt, indistinct proximal ones, and 2 smallsetae on coxal gnathobase; basiswith 1 setaonmedial margin; exopod with 5 setae, outer 2 distinctly larger than 3 inner setae; endopod with 4 and 9 setaeon first and second segments, respectively; 2 outer distal setae on second endopodal segment subequal in length, third much larger than other 8. Paragnath ( Fig. 87A ) as usual for genus. Maxillule ( Fig. 86I ) with 10 setae on arthrite, 1 on coxal endite, 2 on epipodite; basiswith 4 setaeon medial margin, second proximal seta larger than other 3; exopod with 4 setae distally; endopod 2-segmented, with 3 smallsetae on first, and 2 (1 long, naked and 1 short pinnate) setae on second segment. Maxilla ( Fig. 87B ) 6-segmented; precoxa with 4 and 1 setae on first and second endites, respectively; coxa incompletely articulated from precoxa, with 2 and 3 setae on first and second endites, respectively; basis with slender, smooth claw plus 2 setae; endopod slender with 1, 1, and 4 setae on first to third segments, respectively. Maxilliped ( Fig. 86J ) 3-segmented, armedwith 9, 1, and 2 setae onfirst to third segments, respectively; thirdsegment small; articulation incomplete between first 2 segments.

Leg 1 ( Fig. 87C ) with 3-segmented rami. Legs 2–4 ( Fig. 87 D–F) each with 3-segmented exopod and 2- segmented endopod. Inner seta on coxa well-developed in leg 1, rudimentary in leg 3, but apparently absent in legs 2 and 4. Outer seta on basis broad and pinnate in leg 1, but small and naked in legs 2–4. Inner distal spine on basis of leg 1 acutely pointed at tip, 39 μm long, slightly longer than first endopodal segment. Outer spines on exopods of legs 2–4 slender, but swollen distally. First exopodal segment of legs 2–4 elongated, about 3.3 times longer than wide in legs 2 and 3 and 2.5 times in leg 4. Setae on legs 2–4 sparsely pinnate. Armature formula for legs 1–4 as follows:

	Coxa	Basis	Exopod	Endopod
Leg 1	0-1	1-I	I-1; I-1; III, I, 4	0-1; 0-1; 1, 2, 3
Leg 2	0-0	1-0	I-1; I-1; II, II, 0	0-1; 1, 2, 5
Leg 3	0-1	1-0	I-1; I-0; II, II, 0	0-1; 1, 2, 5
Leg 4	0-0	1-0	I-1; I-0; II, II, 0	0-1; 1, 2, 4

Leg 5 ( Fig. 87G ) 2-segmented. Protopod longer than wide, fused with somite, armed with 1 naked seta at outer distal corner and ornamented with row of several minute spinules near inner distal corner; free exopodal segment about 3.4 timeslongerthan wide (65×19 μm), armed distally with 1 small spine and 1 naked seta; ornamented with 3 rows of minute spinules on medial surface.

	Coxa	Basis	Exopod	Endopod
Leg 1	0-1	1-I	I-1; I-1; III, I, 4	0-1; 1, 2, 4
Legs 2 & 30-1	30-1	1-0	I-1; I-1; III, I, 0	0-1; 1, 2, 5
Leg 4	0-1	1-0	I-0; I-1; II, I,0	0-1; 1, 2, 4

Male. Unknown.

Remarks. Pachypygus bisetiger sp. nov. is unique in the genus in having only 2 setae on the third segment of the maxilliped; all other species have either 3 or 4 setae. In addition, there are only 2 setaeon the second endopodal segment of the maxillule in the new species, whereas there are 3 setae on this segment in all other described species. The 2-segmented endopod of legs 2–4 in the new species is also unique: all other species have 3-segmented endopods on these legs. The distal segments of the 2-segmented endopods are compound, representing the second and third ancestral segments.

Figures

FIGURE 86. Pachypygus bisetiger sp. nov., female. A, habitus, right; B, urosome, ventral C, distal part of abdomen, right; D, rostrum; E, antennule; F, antenna; G, labrum; H, mandible; I, maxillule; J, maxilliped. A, 0.5 mm; B, 0.1 mm; C–F, H–J, 0.05 mm; G, 0.02 mm.

FIGURE 87. Pachypygus bisetiger sp. nov., female. A, paragnath; B, maxilla; C, leg 1; D, leg 2; E, leg 3; F, leg 4; G, leg 5. Scale bars: A, G, 0.02 mm; B–F, 0.05 mm.