Doropygella thorelli ( Aurivillius, 1882 )

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 : 303-307

Doropygella thorelli ( Aurivillius, 1882)

( Figs. 202–204 )

Material examined. 3 ♀♀ (MNHN-IU-2018-1922) and dissected 1 ♀ and 1 ♂from Styela sigma Hartmeyer, 1912 , French Guiana (07°10´Ń, 52°59´Ẃ), GUYANE 2014 Cruise, Stn CP 4364, N/O “Hermano Gines”, depth 397-399 m, MNHN—convention APA-973-1 coll., 01 August 2014.

Descriptionoffemale. Body ( Fig. 202A ) stout, slightly dorsoventrally depressed, 2.33 mm long. Dorsal cephalic shield strongly expanded ventrolaterally, completely concealing cephalothoracic appendages in lateral view ( Fig. 202A ). First pedigerous somite free: second and third pedigerous somites with weakly developed epimera; fourth pedigeroussomite expanded to form almost spherical brood pouch, largely incorporating fifthpedigerous somite. Freeurosome ( Fig. 202B ) 5- segmented; genitalsomite short; 4 abdominalsomites 214×300, 150×272, 122×250, and 236×226 μm, respectively. Anal somite with small, nipple-shaped tubercle on distal margin medial to base of caudal ramus. Caudalramus ( Fig. 202C ) about 3.3 timeslongerthan wide (155×47 μm) and about two thirds as long as anal somite: armed with 6 small setae; outer proximal and dorsal setae located at 38 and 61% of ramus length, respectively; all setae short (at most half as long as ramus width).

Rostrum ( Fig. 202D ) graduallynarrowing distally, longerthan wide (127×89 μm), with roundeddistal margin and apical tubercle. Antennule ( Fig. 202E ) 9-segmented; first to fourth segments greatly broadened, fifth to apical segments cylindrical; articulation between second and third segments incomplete; armature formula 2, 5, 12, 6, 4, 3, 4+aesthetasc, 2+aesthetasc, and 7+aesthetasc; all setae naked. Antenna ( Fig. 202F ) stout, 4-segmented; coxa unarmed; basis short, with 1 small seta distally and row of setules on medial surface; first endopodal segment unarmed, longer and wider than basis; compound distal endopodal segment about 3.1 times longerthan wide (109×35 μm), slightly longerthan first; armed with 9 small setae and row of spinules subdistally, plus terminal claw half as long as segment.

Labrum ( Fig. 202G ) with trilobate, setulose posterior margin and few spinules subdistally on lateral margins. Mandible ( Fig. 202H ) with 5 teeth on coxal gnathobase; basis with relatively long seta on medial margin; exopod short, unsegmented with 5 equally large setae; endopod armed with 4 and 10 setae on first and second segments, respectively. Paragnath ( Fig. 202I ) ornamented with setules plus few spinules on medial surface; distal margin smooth. Maxillule ( Fig. 202J ) with 10 setaeon arthrite, 1 slender setaon coxal endite, 2 on epipodite; 4 each on basis and exopod; endopod incompletely 2-segmented, bearing 2 and 4 setae on first and second segments, respectively. Maxilla ( Fig. 203A ) 4-segmented; syncoxa with 4 (1 small and naked), 1, 2, and 2 setae on first to fourth endites, respectively; basis with slender claw plus 2 setae; 2-segmented endopod very small, first segment unarmed, second with 5 slender naked setae. Maxilliped ( Fig. 203B ) 3-segmented, articulations between segments incomplete; first segment with 7 or 6 setae, smaller proximal seta (indicated by arrowhead in Fig. 203B ) present or absent in different specimens; second segment unarmed and unornamented; third segment narrow with 3 setae.

Legs 1–4 rami 3-segmented ( Fig. 203 C-F) with exopods and endopods widely separated from each other. Inner coxal seta absent in legs 1–4. Basis of leg 1 broad with protruding inner distal corner bearing slender spine, 45 μm long. Third endopodal segments of legs 2–4 each bearing 3 spines distally. Spines on both rami elongate and straight. Inner setae on third exopodal segment of legs 2–4 small and naked. Armature formula for legs 1–4 as in generic diagnosis.

Leg 5 ( Fig. 203G ) 2-segmented; protopod with 1 outer distal seta; exopod short, about 1.6 times longer than wide (54×33 μm), with attenuated distal region and armed with 2 small setae (1 distal and 1 inner subdistal). Leg 6 ( Fig. 203H ) represented by 2 small setae in genital region laterally on somite.

Descriptionofmale.Body( Fig.204A )dorsoventrally depressed, divisible into broad cephalosome, narrower metasome, and slender urosome. Body length 1.40 mm; prosome 745 μm long. Cephalosome twice as wide as long. Metasome comprising first to fourth pedigerous somites, with parallel lateral margins. Urosome ( Fig. 204B ) cylindrical, 6-segmented, consistingof welldefined fifth pedigerous somite, genital somite, and 4 free abdominal somites. Anal somite longest of urosomites, 159×150 μm. Caudal ramus about 3.7 times longer than wide (134×36 μm) and slightly shorter than anal somite.

Rostrum as in female. Antennule ( Fig. 204C ) 9- segmented, similartothatof female; armatureformula 2, 5, 12, 6, 4, 5, 3+aesthetasc, 2+aesthetasc, and 7+aesthetasc. Antenna, mouthparts and legs 1–4 all as in female.

Leg 5 protopod broad; exopod similar to that of female. Leg 6 ( Fig. 204B ) represented by 2 equal setae on genital operculum.

Remarks. This material can be unequivocally identitfied as Doropygella thorelli by the characteristic form of the rostrum, maxilla, maxilliped, and leg 5. These features are in accord with the descriptions of Aurivillius (1882) and Sars (1921). The discovery of this species on the Atlantic coast of South America is remarkable since it had previously been found only in the North Atlantic, ranging from Norway and Sweden in the eastto Greenland and the Davis Strait in the west ( Illg, 1958).

Figures

FIGURE 202. Doropygella thorelli (Aurivillius, 1882), female. A, habitus, right; B, urosome, ventral; C, right caudal ramus, ventral; D, rostrum; E, antennule; F, antenna; G, labrum; H, mandible; I, paragnath; J, maxillule. Scale bars: A, 0.5 mm; B, 0.1 mm; C–J, 0.05 mm.

FIGURE 203. Doropygella thorelli (Aurivillius, 1882), female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, exopod of leg 3; F, leg 4; G, leg 5; H, genital aperture. Scale bars: 0.05 mm.

FIGURE 204. Doropygella thorelli (Aurivillius, 1882), male. A, habitus, dorsal; B, urosome, ventral; C, antennule. Scale bars: A, 0.2 mm; B, 0.1 mm; C, 0.05 mm.