Notodelphyopsis longicaudata, 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 : 82-85

Notodelphyopsis longicaudata sp. nov.

( Figs. 53 , 54 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21231 ) anddissectedparatype (♀, figured) from Ascidia archaia Sluiter, 1890 , Île Nou, New Caledonia, 1985.

Additionalmaterial. 1 ♀ (MNHN-IU-2018-1778) from A. archaia, Île Nou New Caledonia, Stn NC13.

Etymology. The name refers to the extremely long caudal rami of the new species.

Descriptionoffemale. Body ( Fig. 53A ) depressed, similarto that of Notodelphyopsis falcifera in external appearance, but caudal rami and antennules much longer. Body length 2.77 mm, including elongate caudal rami. Posterolateral corners of cephalosome and of second and thirdpedigeroussomitesextendedposteriorly,thuscreating concave posterior margins. First pedigerous somite much narrower than other prosomites, lacking epimera. Brood pouch oval, 985×646 μm, longer than anterior part of prosome; incorporatingfusedfifthpedigerous somite. Free urosome ( Fig. 53B ) small, consistingof genital doublesomite and 3-segmented abdomen; genital double-somite graduallynarrowing posteriorly, 102×144 μm; first and second free abdominal somites equal in length, each wider than long. Anal somite shorter than preceding abdominal somites. Caudalramus ( Fig. 53A, C ) extremely long, flexible, about 23 timeslongerthan wide (1000×44 μm); armed with 6 small setae, 5 distally ( Fig. 53C ) and lateral seta positioned at 30% of ramus length; lateral margins parallel.

Rostrum ( Fig. 53D ) subrectangular, widerthan long, 83×100 μm, slightly broadening distally, with weak constriction posteriorly. Antennule 7-segmented ( Fig. 53E ), extremely elongate and narrow, 1120 μm long, extending to middle of brood pouch; armature formula 3, 16, 6, 5, 4, 2+aesthetasc, and 11+2 aesthetascs; setae small, usually weakly pinnate; segments with minute setules on anterior margin. Antenna ( Fig. 53F ) consisting of coxa, allobasis and free 1-segmented endopod; short coxa unarmed; allobasis with 2 equally large, pinnate setae onouter marginrepresenting exopod; freeendopodal segment about 5 times as long as wide, armed with 10 setae plus terminal claw half as long as segment.

Coxa Basis Exopod Endopod
Leg 1	0-1	1-I	I-0; I-1; III, 1, 40-1; 0-1; 1, 2, 3
Legs 2 & 30-0		1-0	I-0: I-1; III, I, 5 0-1; 0-2; 1, 2, 3
Leg 4	0-0	1-0	I-0; I-1; III, I, 5 0-1; 0-2; 1, 2, 2

Labrum ( Fig. 54A ) broad with slightly concave posterior margin, ornamented with dense setules along lateral borders and minute spinules proximally on ventral surface. Mandible ( Fig. 53G ) consisting of coxa and biramous palp: coxalgnathobase ( Fig. 53H ) with 4 major teeth, 2 spiniform teeth on cutting margin, 2 small setae on distal proximal margin, 2 spinule-like processes on distal margin near distalmost tooth: palp consisting of basis, exopod and endopod; basis with 1 setaonmedial margin; exopod indistinctly 3-segmented and armedwith 1, 1, and 3 setae on first to third segments, respectively, proximal 3 setae naked 2 distalsetae pinnate, expanded along proximal third, and more than twice as long as proximal 3 smaller setae: endopod 2-segmented, bearing 2 and 8 setae on first and second segments, respectively. Maxillule ( Fig. 53I ) with 9 setae on arthrite, 1 on coxal endite, 2 on epipodite, and 4 on medial margin of basis, second proximal seta much smaller than other 3; exopod with 4 setae distally; endopod 2-segmentedwith 1 setaon medial margin of first segment and 4 setae (2 large distal setae and 2 much smaller outer setae) on second segment. Maxilla ( Fig. 54B ) 5-segmentedwith 9 setaeonsyncoxa (3, 1, 2, and 3 on first to fourth endites, respectively), 3 on basis (1 large and 2 smaller), and 1, 1, and 3 on first to third endopodal segments, respectively. Maxilliped ( Fig. 54C ) 3-segmented and armedwith 9, 0, and 2 setaeon first to third segments, respectively; articulation incomplete between second and third segments.

Legs 1–4 ( Fig. 54 D–G) with 3-segmented rami: all legs lacking inner seta on first exopodal segment. Inner seta on coxa large in leg 1, absent in legs 2–4. Outer seta on basis large and pinnate in leg 1, but small and naked in legs 2–4. Innerdistalspineonbasisofleg 1 curved, clawlike, about half as long as first endopodal segment. First exopodal segment of leg 1 expanded. Two inner subdistal setae on third endopodal segment of leg 1 enlarged and broadened proximally. Inner seta on first endopodal segment of legs 2 and 3 strong, spiniform. Outer spine on first and second exopodal segments of leg 2–4 strong, curved, and claw-like. Outer margin of first and second exopodal segments of legs 2–4 ornamented with setules: 2 (1 in leg 4) on first and 1 on second segments. Spines on third exopodal segment of legs 2–4 setiform, blunt at tip. Third exopodal segment of leg 4 armed with 4 spines and 5 setae as in N. falcifera . Armature formula for legs 1–4 as follows:

Leg 5 ( Fig. 54H ) represented by 2 papillae fused to each other at base, each tipped with 1 naked seta.

Male. Unknown.

Remarks. Notodelphyopsis longicaudata sp. nov. is very similarto the type species, N. falcifera . They share many of the detailed morphological features of the mouthparts and legs 1–4, including the III, I, 5 setation formula for the third exopodal segment of leg 4. The significant differences between these two species are: (1) the antennule of N. longicaudata sp. nov. is longer than in N. falcifera , extending to the middle of the brood pouch (vs. extending only to the posterior margin of the third pedigerous somite in N. falcifera ); (2) the caudal ramus of N. longicaudata sp. nov. is relatively longer than that of N. falcifera, 1000 ×44 μm, more than 20 times longer than wide (vs. 500×41 μm, about 12 times longerthan wide in N. falcifera ); (3) the exopodal setae of the antenna are subequalin N. longicaudata sp. nov. but markedly unequal in N. falcifera ; and (4) the inner distal spine on the basis of leg 1 of N. longicaudata sp. nov. is short (about half as long as the first endopodal segment), but longer than the first endopodal segment in N. falcifera . The differences are sufficient to justify the establishment of this remarkable new species.

Figures

FIGURE 53. Notodelphyopsis longicaudata sp. nov., female. A, habitus, dorsal; B, urosome, ventral; C, distal part of caudal ramus; D, rostrum; E, antennule; F, antenna; G, mandible; H, coxal gnathobase of mandible; I, maxillule. Scale bars: A, 0.5 mm; B–D, G, 0.05 mm; E, 0.1 mm; F, H, I, 0.02 mm.

FIGURE 54. Notodelphyopsis longicaudata sp. nov., female. A, labrum; B, maxilla; C, maxilliped; D, leg 1; E, leg 2; F, leg 3; G, leg 4; H, leg 5. Scale bars: A–C, H, 0.02 mm; D–G, 0.05 mm.