Paranotodelphys polycarpae, 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 : 57-58

Paranotodelphys polycarpae sp. nov.

( Figs. 36 , 37 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21221 ) , paratype (intact ♀, MNHN-IU-2014-21222) , and dissected paratype (♀, figured) from Polycarpa nigricans Heller, 1878 , Ibo, Mozambique, depth 0–20 m, Monniot coll., 11 November 1995.

Additionalmaterial. 2 ♀♀ (MNHN-IU-2018-1777) (slender form) collected along with type material.

Etymology. The name of the new species is derived from the generic name of the type host.

Descriptionoffemale. Body ( Fig. 36A ) curved ventrally, 2.62 mm long. First to third pedigerous somites with weakly developed dorsal tergites. Brood pouch 1.33×0.68 μm inlateral view, longerthan anterior body somitescombined.Freeurosome ( Fig.36B )cylindricaland 5-segmented: genitalsomite 80×175 μm; 4 freeabdominal somites gradually narrowing 125×155, 127×143, 109×127, and 95×117 μm, respectively. Caudalramus ( Fig. 37A ) narrowing distally, widest across proximal quarter, about 4.1 times longer than wide (167×41 μm) and 1.8 times longer than anal somite; armed with 6 small setae, outer lateral seta positioned at 37% of ramus length, and subdistal seta (seta VII) at 75% of ramus length.

Rostrum ( Fig. 36C ) shield-shaped, 109×65 μm, weakly tapering, and well-defined from cephalosome, with scattered minute setules on ventral (anterior) surface. Antennule ( Fig. 36D ) 11-segmented; segmental fusions I-II, III-XI, XII, XIII, XIV, XV-XVI, XVII-XX, XXI-XXIII, XXIV, XXV, XXVI-XXVIII; suture lines between third to fifth segments distinct only on dorsal surface; armature formula 3, 21, 3, 2, 2, 6, 7, 5+aesthetasc, 4, 4+aesthetasc, and 8+aesthetasc; 2 setaeonfirst segment pinnate, other setae naked (as figured). Antenna ( Fig. 36E ) robust, consisting of unarmed coxa, allobasis, and compound distal endopodal segment; allobasis inflated, armed with 2 equal, pinnate setae representing exopod near middle of outer margin and ornamented with transverse row of fine spinules on inner side; trace of partial suture present near base of exopodal setae; exopodal setae fused to each other at base; free endopodal segment about 2.5 times longer than wide (76×31 μm) and ornamented with row of spinules on outer margin; armed with terminal claw plus 11 setae (arranged as 1, 1, 3, 1, 2, and 3), outer subdistal seta on endopod pinnate, other setae naked; terminal claw about half as long as segment.

Labrumdenselysetulosedistally;freeposteriormargin concave. Mandible ( Fig. 36F ) with 5 teethand 2 proximal setae on coxal gnathobase; needle-like spinule present between 2 proximal teeth; basis with 1 seta and setules on medial margin; exopod unsegmented with 5 setae (3 large and 2 smaller); endopod with 2 and 8 setae on first and second segments, respectively. Paragnath not observed. Maxillule ( Fig. 36G ) with 8 setae on precoxal arthrite (1 small), 1 seta on coxal endite, 2 setae on epipodite, 3 setae on medial margin of basis; small exopodwith 4 distal setae; endopod unsegmented, with 6 setae (3 distalsetae longer than other 3). Maxilla ( Fig. 37B ) 5-segmented; syncoxa with 3, 1, 2, and 3 setae on first to fourth endites, respectively; basiswith 2 setae; endopodwith 1, 1, and 3 setae on first to third segments, respectively. Maxilliped ( Fig. 36H ) 3-segmented, armedwith 9, 0, and 3 setae on first to third segments, respectively; second segment ornamented with setules onmedial marginand with slight swelling at outer distal corner.

Legs 1–4 ( Fig. 37 C–F) biramous with 3-segmented rami. Inner coxal seta large and pinnate in legs 1 and 2, but rudimentary in legs 3 and 4. Outer seta on basis of legs 2–4 small and naked. Inner seta on first exopodal segment of leg 4 rudimentary. Inner distal spine on leg 1 basis 52 μm long, longerthan firstendopodal segment. Armature formula for legs 1–4 as in generic diagnosis.

Leg 5 ( Fig. 36B ) represented by 2 small papillae each tipped with single minute seta.

Description of slender-form female. Body 2.54 mm long in dissected specimen. Brood pouch more slender than in typical form. Urosome ( Fig. 37G ) similar to that of typical form but caudal ramus ( Fig. 37H ) about 3.2 times longerthan wide (108×34 μm) and about 1.5 times longer than anal somite, with thick cuticular wall. Antennule, antenna, mouthparts, and legs 1–5 as in typical form.

Male. Unknown.

Remarks. Two of the five observed females were different in body shape from the three type specimens. These two specimens have a narrower brood pouch and shorter caudal rami. The caudal rami of the slender-form female are about 3.2 times longerthan wide and 1.5 times as long as anal somite, in contrast to about 4.1 and 1.8 times, respectively, found in the dissected paratype. These differences are recorded here, but because no other morphological differences were found between the types and the slender form, we are treating them as belonging to the same species.

Only two congeneric species, P. saccata and P. furcifera , are known to have the first endopodal segment of the antenna fully incorporated into an allobasis leaving only one free segment (the compound distal endopodal segment), as in the new species. Paranotodelphys saccata differs from the new species in having relatively shorter caudal rami and in having 2 unequal exopodal setae on the antenna. It also differs in the segmentation of the female antennule since the new species has 11 segments whereas P. saccata has 10 segments according to Stock (1967), although we found 9 segments in the material examined in the present account. Paranotodelphys furcifera is very similar to the new species. Based on comparison with the original description ( Stock, 1967), the main differences are the prominent, digitiform distal swelling on the second segment of the maxilliped (this distal swelling is very weakly expressed in the new species), the lack of the inner seta on the coxa of leg 4 (this seta present in the new species, although it is small), and the penultimate segment of the female antennule carries only 1 seta (compared to 4 setae plus an aesthetasc in the new species). These differences are sufficient to justify the establishment of the new species.

Again, there are additional setae present on the distal segments of the female antennule in the new species ( Fig. 30 ): the secondsegment (III-XI) carries 3 additional setae, the third segment (XII) carries 1 additional seta, the sixth segment (XV-XVI) carries 1 additional seta, the eighth segment (XXI-XXIII) carries 1 or 2 additional setae on the anterior margin, the ninth (XXIV) and tenth (XXV) each carry 2 additional anterior margin setae, and the apical segment carries 1 additional seta.

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 36. Paranotodelphys polycarpae sp. nov., female. A, habitus, right; B, urosome, ventral; C, rostrum; D, antennule; E, antenna; F, mandible; G, maxillule; H, maxilliped. Scale bars: A, 0.5 mm; B, 0.1 mm; C, D, F, 0.05 mm; E, G, H, 0.02 mm.

FIGURE 37. Paranotodelphys polycarpae sp. nov., female. A, left caudal ramus, dorsal; B, maxilla; C, leg 1; D, leg 2; E, leg 3; F, leg 4; G, urosome of slender–type female; H, left caudal ramus of slender–type female, dorsal. Scale bars: A–F, H, 0.05 mm; G, 0.1 mm.