Paranotodelphys bisetata, 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 : 64-69

Paranotodelphys bisetata sp. nov.

( Figs. 42 , 43 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21225 ) anddissectedparatype (♀, figured) from Ecteinascidia nexa Sluiter, 1904 , on seaweed, Ibo, Mozambique, Monniot coll., November 1995.

Additionalmaterial. 1 ♀ (dissected)from Perophora multiclathrata (Sluiter, 1904) , Ibo, Mozambique, Monniot coll., 09 November 1995.

Etymology. The name of the new species refers to the presence of only two setae on the terminal segment of the maxilliped.

Description of female. Body ( Fig. 42A, B ) moderately stout, 1.33 mm long. Cephalosome only slightly wider than following pedigerous somites. Brood pouch expanded, oval, 577×409 μm, about 1.3 times as long as anterior part of body, nearly circular inlateral view. Freeurosome ( Fig. 42C ) 5-segmented, gradually narrowing posteriorly; genital and 4 abdominal somites 64×125, 58×100, 51×86, 55×80, and 55×71 μm, respectively. Caudal rami ( Fig. 42C ) slightly divergent; each ramus narrowing evenly towards tip, about 4.2 times longer than wide (114×27 μm) and twice as long as anal somite; armed with 6 setae, outer lateral seta positioned at 34% of ramus length.

Rostrum ( Fig. 42D ) tapering, 75×52 μm, articulated at base, withrounded apex. Antennule ( Fig. 42E ) 9- segmented; armatureformula 3, 9, 6, 4+aesthetasc, 4, 2+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; proximal segments not expanded; several setae pinnate (as figured); secondsegment with trace of subdivision. Antenna ( Fig. 42F ) 4-segmented; coxa short, unarmed; basis distally with 1 pinnate seta and 1 smaller naked seta representing exopod, 26 and 18 μm long, respectively, lengths less than distal width of basis; first endopodal segment unarmed; compound distal endopodal segment about 3.4 times longerthan wide (55×16 μm); armed with 9 setae plus terminal claw about half as long as segment.

Labrum destroyed, not examined. Mandible ( Fig. 42G ) with 5 teeth and 1 small proximal setaon coxal gnathobase; distalmost tooth acutely attenuated; needlelike spinule present between 2 proximal teeth; basis with broad proximal protuberance on outer margin, plus 1 subistal seta and row of setules on medial margin; exopod with 5 setae, distal seta distinctly larger than other 4; endopod incompletely articulated from basis, with 2 and 8 setae on first and second segments, respectively. Maxillule ( Fig. 42H ) with 8 setae on arthrite, 1 on coxal endite, 2 on epipodite; basis with 2 small proximal and 1 large distal setae on medial margin; exopod with 4 setae distally; endopod unsegmented with 6 setae. Maxilla ( Fig. 43A ) 5-segmented; syncoxa with 9 enditic setae 9 (3, 1, 2, 3), 2 setae on basis, and 1, 1, and 3 on first to third endopodal segments, respectively; basis withsmall additional knob (indicated by arrowhead in Fig. 43A ) possibly vestige of seta. Maxilliped ( Fig. 74I ) 3-segmented and armedwith 9, 0, and 2 setae on first to third segments, respectively; second segment with bulbous swelling at outer distal corner and ornamented with setules on medial margin.

Legs 1–4 ( Fig. 43 B–E) with 3-segmented rami. Inner seta on coxa large in leg 1, smaller and pinnate in leg 2, small and naked in leg 3, and lacking in leg 4. Outer seta on basis pinnate in leg 1, small and naked in legs 2–4. Innerdistalspineonbasisofleg 152 μmlong, much longerthan first endopodal segment, with spinules on margins. Outer spine on first exopodal segment of leg 1 large, extending to middle of third exopodal segment. Outer spines on first exopodal segment of leg 1, and on first and second exopodal segments of legs 2–4 smooth, without ornamentation. Spines on third exopodal segment of legs 2–4 pectinate along distal half of outer margin. Armature formula for legs 1–4 as in generic diagnosis except for absence of inner coxal seta of leg 4.

Leg 5 ( Fig. 42C ) represented by 2 papillae, each tipped with minute seta.

Male. Unknown.

Remarks. The new species can be compared with its five congeners bearing only 2 setae. rather than 3, on the third segment of the maxilliped. These five species are P. engeli Stock, 1967 , P. phallusiae ( Gurney, 1927) , P. procax Stock and Humes, 1970 , P. scutiformis , and P. villosus Ooishi, 1963 . These can be distinguished from the new species as follows: in P. engeli the caudal ramus is strongly tapering and about twice as long as wide; the exopod of the antenna is represented by 2 subequal pinnate setae; and leg 4 has an inner coxal seta, whereas in the new species the caudal ramus is about 4.2 times longer, the exopodal setae differ markedly in length, and leg 4 lacks the inner coxal seta.

In P. phallusiae the female body length is 2.12 mm, the brood pouch is elongated, the exopod of the antenna is represented by 2 equal setae, the second endopodal segment of the mandible is armed with 7 setae, and the endopod of the maxillule is armed with 4 setae. In contrast the new species is much smaller (1.33 mm) and the brood pouch is oval, the exopodal setae differ markedly in length, the second endopodal segment of the mandible is armed with 8 setae, and the endopod of the maxillule is armedwith 6 setae.

Paranotodelphys procax has caudal rami that are hirsute along the inner margin whereas in the new species these margins are smooth. The exopod of the antenna is represented by 2 very unequal setae in P. procax with the longersetamorethan 3 timesthe length of theshorter.Also both these setae are naked according to Stock & Humes (1970). In the new species the longer seta is pinnate and less than 50% longer than the shorter naked seta.

In P. scutiformis the bodyis dorsoventrally depressed, the prosome has parallel lateral margins and the caudal rami are very short (about 1.3 times longer than wide and about equal in length to the anal somite), whereas in the new species the brood pouch is markedly wider than the rest of the prosome and the caudal rami are about 4.2 times longerthan wide and about twice the length of the anal somite. There are additional differences in limb setation: for example the second endopodal segment of the mandible is armed with 7 setae in P. scutiformis (8 in the new species) and the endopod of the maxillule has 5 setae (6 in the new species).

Finally, in P. villosus the brood pouch is elongated, the caudal rami are extremely elongate, 11 times as long as wide ( Ooishi, 1963) and have a densely hirsute inner margin, the exopod of the antenna is represented by 2 long, pinnate setae, and leg 4 has an inner coxal seta. All of these character states differ from those exhibited by the new species.

The female antennule does not display any additional setal elements on the distal segments.

Figures

FIGURE 42. Paranotodelphys bisetata sp. nov., female. A, habitus, dorsal; B, habitus, right; C, urosome, vental; D, rostrum; E, antennule; F, antenna; G, mandible; H, maxillule. Scale bars: A, B, 0.2 mm; C, 0.1 mm; D–I, 0.02 mm.

FIGURE 43. Paranotodelphys bisetata sp. nov., female. A, maxilla showing small knob on basis (arrowhead); B, leg 1; C, leg 2; D, leg 3; E, leg 4. Scale bars: A, 0.02 mm; B–E, 0.05 mm.

FIGURE 74. Pachypygus curvatus Ooishi, 1961, female. A, habitus, left; B, urosome, ventral; C, right caudal ramus, ventral; D, rostrum ventral; E, rostrum, left; F, antennule; G, antenna; H, labrum; I, mandible; J, paragnath; K, maxillule. Scale bars: A, 0.5 mm; B, 0.2 mm; C–E, I, 0.1 mm; F–H, J, K, 0.05 mm.