Notopygus minutispinatus, 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 : 399-400

Notopygus minutispinatus gen. et sp. nov.

( Figs. 265 , 266 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21335 ) , paratypes (2 intact ♀♀, MNHN-IU-2014-21336), anddissectedparatype (♀, figured) from Pyura stolonifera (Heller, 1878) (MNHN-IT-2008-7777 = MNHN S2/ PUY/XXX, lames 306), MRAC-ULB (Musée Royal de l’Afrique Centrale et Université Libre de Bruxelles), Inhaca Is, Mozambique (26°03 Ś, 32°54 É), depth 10-20 m, 07 August 1969.

Etymology. The specific name is derived from the Latin minut (=small) and spin (=spine) and refers to the small size of the apical spines on the caudal ramus.

Descriptionoffemale. Body ( Fig. 265A ) 4.36 mm long: prosome 3.60 mm long, with well-defined dorsal cephalic shield and bulbous metasome. Cephalosome to second pedigerous somite divided by weak constrictions; third and fourth pedigerous somites fused to form greatly inflated brood pouch. Free urosome ( Fig. 265B ) 5- segmented,graduallynarrowingposteriorly:genitalsomite 270×502 μm, with copulatory pore at anterior quarter on ventral surface; 4 abdominalsomites 364×393, 327×335, 182×276, and 167×247 μm, respectively. Caudalramus ( Fig. 265C ) about 4.1 timeslongerthan wide (264×64 μm), with nearly parallel margins in proximal third but graduallynarrowing in distal two-thirds: armedwith 2 small setae and 4 minute distal spines; 2 setae positioned at 34 and 63% of ramus length, both setae about half as long as width of ramus at base; distal spines blunt, at most 13 μm long, scarcely visible at low magnification.

Coxa Basis Exopod			Endopod
Leg 1 0-1 Legs 2 & 30-1 Leg 4 0-1	1-I 1-0 1-0	I-1; I-1; III, I, 4 1-1; 1-1; 3, 1, 5 1-1; 1-1; 3, 1, 5	0-1; 0-1; 1, 2, 3 0-1; 1, 2, 5 0-1; 1, 2, 4

Rostrum ( Fig. 265D ) about 110×136 μm, gently tapering proximally and steeply tapering in distal third. Antennule ( Fig. 265E ) 345 μmlong, 9-segmented; first and second segments much broader than distal segments; fifth segment subdivided on posterior side; armature formula 3, 17, 5, 5, 4, 2+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; setae generally small, all naked. Antenna ( Fig. 265F ) 4-segmented; coxa unarmed; basis 127×69 μm, with 2 vestigial setae on small knob (representing exopod) subdistally on outer margin; first endopodal segment 90×64 μm, with 1 small seta on inner margin; compound distal endopodal segment about 3.2 times longerthanwide (120×38 μm): armedwith 7 setae arranged as 1, 3, 1, and 2 plus terminal claw about 76 μm long, strongly curved at tip.

Labrum asin N. trispinatus gen. et sp. nov. Mandible ( Fig. 265G ) with 5 teeth and 1 small seta on coxal gnathobase: basis with 1 seta and row of minute spinules on subdistal medial margin: exopod 3-segmented and armed with 4 subequal setae (1, 1, and 2 setae on firsttothird segments): endopod 2-segmented; first segment with 4 unequal setae on medial margin and minute spinules scattered over ventral surface; second segment narrower than first, armed with 10 setae of various lengths. Paragnath ( Fig. 265H ) as small lobe with setules on medial margin, minute spinules mediodistally, and small rounded outer process distally. Maxillule ( Fig. 265I ) consisting of precoxa, coxa, basis, exopod and endopod: precoxa with 9 setae on arthrite; coxa with 1 seta on endite and 2 very unequal setae on epipodite; basis with 3 (2 long distal and 1 short proximal) setae on medial margin and row of several minute spinules near base of each distal seta; exopod with 3 setae distally and 1 minute vestigial seta between outer and middle setae; endopod with 3 equal setae. Maxilla ( Fig. 265J ) 5-segmented; syncoxa with 9 setae arranged as 3, 1, 2, and 3; basis with 1 strong claw bearing setules along concave margin plus 2 unequal setae; endopod slender, with 1, 1, and 3 setae on first to third segments, respectively. Maxilliped ( Fig. 266A ) incompletely 2-segmented; first segment with 9 setae medially; smallsecond segment with 2 equal apical setae.

Leg 1 ( Fig. 266B ) with 3-segmented rami. Outer seta on basis small. Inner distal spine on basis 50 μm long, not extending to distalborder of first endopodal segment. First and second exopodal segments with dense tuft of setules on outer side. Legs 2–4 with 3-segmented exopods and 2- segmented endopods ( Fig. 266C, D ); exopods longer than endopods. Outer seta on basis small as in leg 1. Outer setae on exopods attenuated and naked. All setae on third exopodal segment of legs 2–4 and 3 distal setae on second endopodal segment of leg 4 naked. Armature formula for legs 1–4 as follows:

Leg 5 ( Fig. 266E ) 2-segmented: protopod broad, notarticulated at base, with 1 small seta on oblique outer margin and row of several spinules near base of exopod; free exopodal segment nearly rectangular and about 3.1 times longer than wide (182×58 μm); armed distally with slender spine (49 μm long) and thin seta (55 μm long); ornamented with 3 rows of minute spinules on dorsomedial surface.

Male. Unknown.

Remarks. Notopygus minutispinatus gen. et sp. nov. can be readily differentiated from its two congeners by the possession of 4 spines and 2 setae on the caudal ramus of the female, and by the 3-segmented endopod of leg 1. In contrast, thetype species N. unispinatus gen. et sp. nov. has only 1 spine and 5 setae on the caudal ramus, and N. trispinatus gen. et sp. nov. has 3 spines and 3 setae. Both these species have a 2-segmented endopod on leg 1 whereas in N. minutispinatus gen. et sp. nov. this ramus is 3-segmented.

Figures

FIGURE 265. Notopygus minutispinatus gen. et sp. nov., female. A, habitus, right; B, urosome, ventral; C, left caudal ramus, dorsal; D, rostrum; E, antennule; F, antenna; G, mandible; H, paragnath; I, maxillule; J, maxilla. Scale bars: A, 0.5 mm; B, 0.2 mm; C–J, 0.05 mm.

FIGURE 266. Notopygus minutispinatus gen. et sp. nov., female. A, maxilliped; B, leg 1; C, leg 2; D, leg 4; E, leg 5. Scale bars: A, 0.05 mm; B–E, 0.1 mm.