Pachypygus papillosus, 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 : 123-126

Pachypygus papillosus sp. nov.

( Figs. 80 , 81 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21239 ) , paratype (intact ♀, MNHN-IU-2014-21240), and dissectedparatype (♀, figured) from the compound ascidian Polycitor africanus Monniot F. & Monniot C., 1997 (MNHN-IT-2008-6885 = MNHNA 3/ POL. A/21), CRRFOCDN 3667-U, Pemba Island, Tanzania (5°14.42’S– 39°35.61’E), depth 30 m, 26 January 1996.

Additionalmaterial. 1 ♀ (MNHN-IU-2018-1812) from P. africanus , Pemba I., Tanzania, OCDN 3767-U ; 1 ♀ (dissected) from P. africanus , Tanzania, OCDN 3667-U, 1996; 2 ♀♀ (MNHN-IU-2018-1813) from P. africanus, Ibo , Mozambique depth 0-20 m, November 1995.

Etymology. The specific name refers to the papillate ornamentation over body surface of the new species.

Description of female. Body ( Fig. 80A ) narrow in lateral view, ventrally flexed. Body with thick cuticle and surface densely ornamented with rounded papillae ( Fig. 80B, C, D, E ). Body length 2.65 mm. Dorsal shield of cephalosome with prominent, digitiform process at each posterolateral corner ( Fig. 80A, B ). Brood pouch with almost straight dorsal margin, tapering obliquely in posterior third. Fifth pedigerous somiteshort and largely fused with brood pouch. Free urosome ( Fig. 80C ) 5- segmented: genitalsomite rectangular, widerthan long, 218×250 μm;4freeabdominalsomites280×211, 225×185, 109×153, and 84×123 μm, respectively. Anal somite ( Fig. 80D ) with short dorsal margin and longer ventral margin inlateral view, and protruding posteroventrally, Caudal ramus ( Fig. 80D ) inserted proximally on dorsal surface of anal somite, about 2.75 times longer than wide (121×44 μm), slightly curved ventrally, narrowing distally; armed with 2 large and 2 small claws, plus 2 setae; lengths of claws 27, 21, 17, and 14 μm; 2 setae positioned at 48% and 71% of ramus length.

Rostrum ( Fig. 80E ) triangular, widerthan long, 159×188 μm, densely papillate on ventral surface, and tipped with small conical process. Antennule ( Fig. 80F ) 8-segmented; secondsegment tapering, with papillate ornamentation, comprising about half length of entire antennule and about twice as long as wide; distal 6 segments small, combined length only half length of secondsegment; armatureformula 3, 15?, 4, 3, 3, 2, 2+aesthetasc, and 7+aesthetasc; all setae small and naked. Antenna ( Fig. 80G ) narrow, 4-segmented; coxa and basis unarmed; first endopodal segment broad, unarmed; compound distal endopodal segment 1.2 times longer than first segment and 2.9 times as long as wide (94×32 μm); armedwith 7 smallsetae (arranged as 3, 1, and 3) plusterminal claw, about half as long as segment.

Labrum ( Fig. 80H ) with paired semicircular lobes posterolaterally, both spinulose; posteriormargin concave, mid-ventral lobe spinulose, and lateral margins setulose distally. Mandible ( Fig. 80I ) with 5 teethand 2 smallsetae on coxal gnathobase; basis with 1 seta and patch of setules proximallyonmedial margin; exopod unsegmented, armed with 5 subequal setae; endopodwith 4 and 9 setaeonfirst and second segments, respectively, second outer seta on distal margin of second endopodal segment small, about half as long as adjacent setae on either side. Paragnath ( Fig. 80J ) with 2 dentiform processes and setulose medial margin, as usual for genus. Maxillule ( Fig. 80K ) with 9 setae on arthrite, 1 on coxal endite, 2 on epipodite, 4 on medial margin of basis (second proximal seta much larger than other 3), 4 on exopod; endopod 2-segmented with 4 setae on medial margin of first segment and 3 setae on distal margin of smallsecond segment. Maxilla ( Fig. 81A ) 5-segmented; syncoxawith 4, 1, 2, and 3 setaeonfirst to fourth endites, respectively; basiswith slender, strongly curved claw plus 2 setae; slender endopod with 1, 1, and 4 pinnate setae on first to third segments, respectively. Maxilliped ( Fig. 81B ) 3-segmented, armedwith 9, 1, and 3 setae on first to third segments, respectively; articulation between proximal 2 segments incomplete.

Legs 1–4 ( Fig. 81 C–F) with 3-segmented rami. Inner setaon coxa present in legs 1 and 2, lacking in legs 3 and 4. Outer seta on basis large in leg 1 but small in legs 2–4. Inner distal spine on basis of leg 1 longer than first endopodal segment, finely spinulose. Inner setaon first exopodal segment large inleg 2, absentin legs 3 and 4. Inner margin of second and third exopodal segments of legs 2–4 straight and smooth. First exopodal segment of legs 2–4 about 3 times longer than wide. Third exopodal segment about 3 times longerthan wide inlegs 2 and 3, about 2.5 timeslongerthan wide in leg 4. 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	0-1	1-0	I-1; I-0; II, II, 0	0-1; 0-2; 1, 2, 3
Leg 3	0-0	1-0	I-0; I-0; II, II, 0	0-1; 0-2; 1, 2, 3
Leg 4	0-0	1-0	I-0; I-0; II, II, 0	0-1; 0-2; 1, 2, 2

Leg 5 ( Fig. 81G ) protopod slightly longer than wide, armed with 1 seta at outer distalcorner and ornamented with row of spinules distally near base of exopod; free exopodal segment about 3.1 times longer than wide (89×29 μm), armed with 1 small spine and 1 naked seta distally; ornamented with 3 rows of small spinules on medial surface.

Male. Unknown.

Remarks. As indicated by the specific name, the new species is characterised by the dense ornamentation of papillae on the dorsal surface of the prosome, all over the surface of the urosomites, and on certain appendages. The large processes on the cephalosome extend back from the posterolateral corners of the dorsal shield and are not known from any other species of Pachypygus . The presence of 9 setae on the second endopodal segment of the mandible, and the 3 setae on the thirdsegment of the maxillipedare alsocharacteristic features; for comparison, all known congeners possess 10 and 4 setae, respectively, on these segments. Collectively these character states serve to clearly differentiate this distinctive new species from all of its congeners.

Figures

FIGURE 80. Pachypygus papillosus sp. nov., female. A, habitus, right; B, posterolateral process of cephalosome; C, urosome, ventral; D, distal part of abdomen, right; E, rostrum; F, antennule; G, antenna; H, labrum; I, mandible; J, paragnath; K, maxillule. Scale bars: A, 0.5 mm; B, C, 0.1 mm; D–K, 0.05 mm.

FIGURE 81. Pachypygus papillosus sp. nov., female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, leg 3; F, leg 4; G, leg 5. Scale bars: 0.05 mm.