Pygodelphys chilensis, 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 : 101-104

Pygodelphys chilensis sp. nov.

( Figs. 66 , 67 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21235 ) , paratypes (intact, 6 ♀♀, 1 ♂, MNHN-IU-2014- 21236) , and dissected paratypes (1 ♀, 1 ♂, figured), from Styela magalhaensis Michaelsen, 1898 , Coquimbo, Chile, depth 450 m, 09 November 2001.

Etymology. The name of the new species refers to its type locality.

Descriptionoffemale. Body ( Fig. 66A ) moderately slender, strongly flexed ventrally. Body length 3.52 mm. Prosomites indistinctly articulated; second and third pedigerous somites with weakly developed epimera. Brood pouch incorporating fused fifth pedigerous somite rather small, subcircular in lateral view, shorter than anterior part of prosome. Free urosome ( Fig. 66B ) clearly 5-segmented, 141×295, 264×268, 228×264, 186×255, and 164×227 μm, respectively. Genital and first abdominal somites each ornamented with rows of minute spinules on ventral surface. Caudalramus ( Fig. 66C ) about 3.9 times longerthanwide (282×72 μm) and 1.7 timeslongerthan anal somite, graduallynarrowing distally; armedwith 6 naked setae, outer lateral seta (seta II) positioned at 26% of ramus length, seta III characteristically positioned on outer margin (not at outer distal corner) at 80% of ramus length.

Rostrum ( Fig. 66D ) large, 205×145 μm, elongate and tapering. Antennule ( Fig. 66E ) 10-segmented; armature formula 3, 17, 6, 4+aesthetasc, 1, 3, 2+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; setae naked, except 4 pinnate setae, 2 on first segment and another 2 on second segment. Antenna ( Fig. 66F ) slender, 3-segmented; short coxa unarmed; allobasis with 3 setae, 2 long, subequal pinnate setae on subdistal outer margin representing exopod and 1 smaller, naked seta derived from first endopodal segment on inner margin; compound distal endopodal segment about 3.4 times as long as wide, with terminal claw and 11 setae (arranged as 1, 1, 3, 1, 2, and 3), 3 distal setae blunt at tip.

Labrum ( Fig. 66G ) densely ornamented with setules posterolaterally, and with setules plus row of spinules on broad posteromedial lobe. Mandible ( Fig. 66H ) with 5 teeth and 2 small setaeon coxal gnathobase, with 1 spinule between 2 proximal teeth; basiswith 1 setaonmedial margin; exopod indistinctly 3-segmented, with 2, 1, and 2 setae on first to third segments, respectively, all exopodal setae equally long; endopod with 4 and 10 setae on first and second segments, respectively. Paragnath ( Fig. 67A ) as simple lobe ornamented only with setules on medial margin; lacking spinules or denticles. Maxillule ( Fig. 66I ) with 9 setae on arthrite, 1 on coxal endite, 2 on epipodite; basis with 3 setae on medial margin (2 small proximal and 1 larger distal); exopodwith 4 setae distally; endopod 2-segmented, with 2 setae on first segment and 3 on smallsecond segment. Maxilla ( Fig. 67B ) 5-segmented; syncoxawith 4 (including minute seta), 1, 2, and 3 setae on first to fourth endites, respectively; basis with strong claw bearing dense spinules along concave margin, plus 2 setae (smaller seta naked); endopodwith 1, 1, and 4 setae on first to third segments, respectively, one of 4 setae on third segment minute, spinule-like. Maxilliped ( Fig. 66J ) 2-segmented with 9 setae on first segment and 2 on second; first segment with setules on distal border; second segment with trace of articulation on medial surface.

Leg 1 ( Fig. 67C ) with 3-segmented rami; innerdistal spine on basis 80 μm long, longer than first endopodal segment, fringed with serrated membranes; first exopodal segment broad with fine spinules along outer margin. Legs 2–4 each with 3-segmented exopod and 2- segmented endopod ( Fig. 67D, E ). Inner seta on coxa of leg 4 rudimentary. Outer setaon basis of legs 1–4 small and naked. Armature formula for legs 1–4 as follows:

Descriptionofmale. Body ( Fig. 67F ) stronglyflexed ventrally. Bodylength 1.93 mm. Urosome 6-segmented: fifth pedigerous somite as wide as genital somite; genital and 4 freeabdominalsomites 130×222, 145×170, 145×156, 116×144, and 91×124 μm, respectively. First and second abdominal somites each ornamented with rows of minute spinules on ventral surface ( Fig. 67G ). Caudal ramus about 4.1 times longer than wide (149×36 μm).

Rostrum as in female. Antennule segmented as in female, but one setaon second segment broadened, spiniform. Antenna, labrum, mandible, paragnath, maxillule, and maxilla also as in female. Maxilliped 2-segmented, lacking trace of articulation on second segment.

Legs 1–4 with distinctly 3-segmented endopods, unlike female. Leg 5 ( Fig. 67G ) consistingof outer protopodal lobe tipped with seta and small free exopodal segment tipped with 1 seta. Leg 6 ( Fig. 67G ) represented by 2 setae on genital operculum.

Remarks. The new species shares the possession of only 5 (not 6) setae on the endopod of the maxillule with only two congeners, P. aquilonaris and P. lamellipes ( Schellenberg, 1922) . These two species can be distinguished from the new species by other characters. According to the description of Illg (1958), the female of P. aquilonaris retains a leg 5 consisting of a tiny outer papilla and inner lobe, each bearing an apical seta (vs. leg 5 absentin the new species); the caudal rami are about 5 timesas longas wide inthe female (vs. about 4 timesin the new species), the proximal outer caudal seta is about three quarters of the length of the ramus and the subdistal outer seta is nearly as long as the ramus (vs. both setae much shorter than the ramus in the new species); and the second endopodal segment of the mandible bears 9 setae (vs. 10 setae in the new species). According to the description and illustrations of P. lamellipes by Schellenberg (1922), the length ratio of the anal somite and the caudal ramus is 3:4, i.e., the caudal ramus is 1.33 times longer than the anal somite (vs. 1.7 times longer in the new species); the proximal outer seta of the caudal ramus is pinnate (vs. naked in the new species), and leg 5 is present in the female (vs. absent in the new species).

The structure of the maxillule is uncertain in P. patriciae . In the original description this appendage was described as having an unsegmented endopod bearing only 2 setae, but in the illustration by Stock (1967), the second segment of the endopod was missing. Pygodelphys patriciae canbeclearly differentiatedfromthe newspecies by numerous other features including a 9-segmented antennule, distinctly shorter and tapering caudal rami, a 3-segmented endopod of leg 2 in the female, the presence of 3 setae on the second segment of the maxilliped, and the well-developed outer spines (rather than setae) on the exopods of legs 2–4.

Figures

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.

FIGURE 67. Pygodelphys chilensis sp. nov., female: A, paragnath; B, maxilla; C, leg 1; D, leg 2; E, leg 4. Male: F, habitus, right; G, anterior part of urosome showing legs 5 and 6, ventral. Scale bars: A, B, 0.05 mm; C–E, G, 0.1 mm; F, 0.2 mm.