Paranotodelphys nodulosa, 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 : 53-57

Paranotodelphys nodulosa sp. nov.

( Figs. 33–35 )

Typematerial. Holotype (intact ♀, MNHN-IU 2014- 21219 ), allotype (intact ♂, MNHN-IU-2014-21220) , and dissected paratypes (1 ♀ and 1 ♂; figured), from Microcosmus helleri Herdman, 1881 , CRRFOCDN 2256- M, Mactan Island, Cebu, the Philippines (10°15.62’N, 123°59.11’E), depth 10m, 15 February 1994.

Etymology. The name of the new species refers to the presence of nodules on the caudal rami of the male.

Description of female. Body ( Fig. 33A, B ) consisting of broad cephalosome and 3 pedigerous somites, all dorsoventrally depressed, expanded brood pouch, and narrow, cylindrical urosome. Firsttothird pedigerous somites each with well-developed dorsal tergite. Body length 3.78 mm in fully grown adult (holotype, Fig. 33A ) and 2.45 mm in dissected young adult with only partially expanded brood pouch ( Fig. 33B ). Brood pouch formed by fourth pedigerous somite, incorporating fused fifth pedigerous somite. Free urosome ( Fig. 33C ) 5-segmented, graduallynarrowing posteriorly: comprising genital and 4 abdominal somites 97×221, 121×200, 136×194, 136×189, and 121×145 μm, respectively. Caudal rami ( Fig. 33C ) directed posteriorly; each ramus ( Fig. 66A ) about 4.1 times longer than wide (211×52 μm) and armed with 6 small setae, all naked and not longer than ramus width; outer lateral seta positioned at 40% of ramus length.

Rostrum ( Fig. 33D ) longer than wide, with parallel lateral margins and rounded apex. Antennule ( Fig. 33E ) graduallynarrowing distally and 9-segmented; armature formula 3, 17, 6, 4, 4, 3+aesthetasc, 3, 3+aesthetasc, and 7+aesthetasc; setae generally pinnate; distalsetaon fourth, fifth and sixth segments annulated at base. Antenna ( Fig. 33F ) 4-segmented; shortcoxa unarmed; basiswith 2 unequal, pinnate setae representing exopod (shorter seta 0.6 times as long); first endopodal segment demarcated from basis by non-sclerotized groove, with 1 seta on inner margin; compound distal endopodal segment about 2.9 times as long as wide (111×38 μm) and ornamented with 3 rows of minute spinules in distal region; armed with 10 small setae plus terminal claw about one-third as long as segment.

Labrum ( Fig. 33G ) densely hirsute posteriorly, with weakly concave posterior margin. Mandible ( Fig. 33H ) consisting of coxa and biramous palp: coxal gnathobase with 5 teeth and 2 proximal setae on cutting edge and ornamented with row of minute spinules near second proximaltoothondorsalsurface:basiswith1setasubdistally and patch of setules proximally on medial margin: exopod unsegmented; armed with 5 setae, distalmostseta markedly larger than other 4; endopod 2-segmented and armed with 2 and 8 setae on first and second segments, respectively. Paragnath ( Fig. 34B ) with rounded outer distal process and dense setules on medial surface. Maxillule ( Fig. 33I ) with 8 setae on arthrite, 1 on coxal endite, 2 on epipodite, 3 on medial margin of basis (proximal 2 small); exopod with 4 setae distally; endopod unsegmented with 6 setae (2 medial and 4 distal). Maxilla ( Fig. 34C ) 5-segmented; syncoxawith 4 (including 1 small), 1, 2, and 3 setaeonfirst to fourth endites, respectively; basis with 1 small naked and 2 large setae; endopodwith 1, 1, and 3 setaeonfirst to third segments, respectively. Maxilliped ( Fig. 34D ) 3- segmented, with 9, 0, and 3 setae on first to third segments, respectively; first segment ornamented with several row of fine spinules; second segment with prominent bulbous swelling distally and ornamented with row of long setules onmedial margin.

Legs 1–4 with 3-segmented rami ( Fig. 34 E–G). Inner coxal seta large in legs 1 and 2, but rudimentary in legs 3 and 4. Outer setaon basis of legs 2–4 also rudimentary. Leg 1 with large inner distal spine on basis, 85 μm long, distinctly longer than first endopodal segment, setulose proximallyand spinulosedistally. Outerspinesonexopods well-developed. Outer margin of exopod of leg 1 smooth but those of legs 2–4 setulose. Inner seta on first exopodal segment of leg 4 rudimentary. Armature formula for legs 1–4 as in generic diagnosis. Leg 5 ( Fig. 33C ) represented by pair of small setae on ventral posterior margin of brood pouch, near base of free urosome.

Description of male. Body ( Fig. 35A ) curved ventrally. Bodylength 1.53 mm. Cephalosome broader than cylindrical remaining part of body. Urosome ( Fig. 35B ) 6-segmented, with free fifth pedigerous somite: urosomites100×182,114×152,120×123,114×114.93×93, and 57×72 μm, respectively. First to third abdominal somites each about as long as wide. Caudal ramus ( Fig. 35C ) armed with 6 naked setae and ornamented with about 10 papillae along outer margin, each papilla with pore at tip.

Rostrum ( Fig. 35D ) tapering towards minutely bifid apex. Antennule ( Fig. 35E ) non-geniculate, indistinctly 9- segmented, butarticulations incomplete between third and fourth and between sixth and seventh segments; armature formula 3, 17, 4, 2, 4+aesthetasc, 1, 6+aesthetasc, 3, and 10+aesthetasc. Antenna ( Fig. 35F ) more stout than in female and consisting of coxa, allobasis and compound distal endopodal segment; allobasis with trace of articulation between basis and first endopodal segment and ornamented with spinulesnear middle; freeendopodal segment about twice as long as wide, with 11 setae.

Labrum ( Fig. 35G ) with large tubercle proximally bearing 3 nipple-shaped processes (1 apical and 2 subdistal lateral); posterior margin slightly concave, with small mid-posterior lobe. Other mouthparts and legs 1–4 asin female.

Leg 5 ( Fig. 35B ) represented by 2 separate ventral setaeonrearmarginof somite.Leg6( Fig.35B ) represented by 2 setae on distal margin of genital operculum.

Remarks. The genus Paranotodelphys currently contains ten valid species ( Walter & Boxshall, 2020). This new species shares the possession of 3 setae on the terminal segment of the maxilliped with five congeners: P. constricta Illg, 1970 , P. furcifera Stock, 1967 , P. gracilis Schellenberg, 1922 , P. longicaudata Schellenberg, 1922 , and P. saccata . The first three of these species all have either 1 or 2 setae on the medial margin of the basis of the maxillule and are, therefore, easy to distinguish from the new species which has 3 setae. Paranotodelphys nodulosa sp. nov. is readily distinguishable from P. longicaudata because the latter species has very long caudal rami in the female, about 3 times longer than the anal somite compared to only about 1.7 times as long in the new species. It differsfrom P. saccata in the form of the female antenna: in P. saccata the basis and the first endopodal segment of the antenna are fully fused to form an allobasis with no trace of any suture marking the plane of fusion, and the seta originally derived from the first endopodal segment is lost, whereas in the new species the basis and first endopodal segment are still separated by a large nonsclerotized groove and the segmental seta is still present. Schellenberg (1922) described P. scutiformis as having 2 or 3 setae on the terminal segment of the maxilliped, but it can be distinguished from the new species by the presence of 7 setae on the second endopodal segment of the mandible (8 in the new species) and only 5 setae on the endopod of the maxillule (6 in the new species). These differences are sufficient to justify the establishment of the new species.

The new species also possesses novel additional setae on two of the distal antennule segments in the female ( Fig. 30 ). The sixth segment (XXI-XXIII) provides the reference point as it carries the aesthetasc derived ancestrally from XXI and the articulated seta derived from XXIII. The seventh segment (XXIV) carries 1 additional setaon the anterior margin (rather than 2 additional setae as in P. saccata ), and the eighth segment (XXV) similarly carries only 1 additional seta on the anterior margin (rather than 2 as in P. saccata ). Even more additional setae are present in P. polycarpae sp. nov. (see below). The segmentation of the male antennule is very unusual because the ancestral articulation (XX to XXI) marking the geniculation in neocopepodans ( Boxshall & Huys, 1998) is not expressed: instead it lies within the compound seventh segment (XVIII-XXIII).

Figures

FIGURE 30. Schematic comparison of antennular segmentation patterns in selected notodelphyid taxa. Roman numerals mark ancestral segments, Arabic numerals indicate number of setae on each segment/compound segment. ae = aesthetasc. Supernumerary setae are identified by reference to the observed maximum setal number known within the Copepoda (see Boxshall & Huys, 1998). Supernumerary setae are present on segments III–XI, XII–XIV, XV–XVI, XXIV and XXV of Paranotodelphys polycarpae, on segments III–XI, XII, XV–XVI, XXI–XXIII, XXIV, XXV and XXVI–XXVIII of P. saccata, and on segments XVII–XX, XXI–XXIII, XXIV, and XXV of Doropygopsis novemsetifera.

FIGURE 33. Paranotodelphys nodulosa sp. nov., female.A, fully grown adult, right; B, young adult, right; C, urosome, ventral; D, rostrum; E, antennule; F, antenna; G, labrum; H, mandible; I, maxillule. Scale bars: A, B, 0.5 mm; C, 0.1 mm; D–I, 0.05 mm.

FIGURE 34. Paranotodelphys nodulosa sp. nov., female. A, right caudal ramus, ventral; B, paragnath; C, maxilla; D, maxilliped; E, leg 1; F, leg 2; G, leg 4. Scale bars: A, C, E–G, 0.05 mm; B, D, 0.02 mm.

FIGURE 35. Paranotodelphys nodulosa sp. nov., male. A, habitus, right; B, urosome, ventral; C, right caudal ramus, dorsal; D, rostrum; E, antennule; F, antenna; G, labrum. Scale bars: A, 0.2 mm; B, 0.1 mm; C–E, 0.05 mm; F, G, 0.02 mm.

FIGURE 66. Pygodelphys chilensis sp. nov., female. A, habitus, right; B, urosome, ventral; C, left caudal ramus, ventral; D, rostrum; E, antennule; F, antenna; G, labrum; H, mandible; I, maxillule; J, maxilliped. Scale bars: A, 0.5 mm; B–E, H, 0.1 mm; F, G, I, J, 0.05 mm.