Doropygus nasutus, 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 : 357-361

Doropygus nasutus sp. nov.

( Figs. 236–238 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21318 ) , paratypes (intact, 24 ♀♀, 2 ♂♂, MNHN-IU-2014-21319, and dissected paratypes (2 ♀♀, 1♂, figured) from Pyura microcosmus (Savigny, 1816) , Roscoff, France, Monniot coll., date unknown.

Additional material. All from P. microcosmus : 8 ♀♀ (MNHN-IU-2018-1863), Roscoff, France; 11 ♀♀ (MNHN-IU-2018-1864), Roscoff; 8 ♀♀, 2 ♂♂ (MNHN-IU-2018-1865), Petit Chevreuil, Dinard, France; 25 ♀♀, 1 ♂ (MNHN-IU-2018-1866) and 1 dissected ♀, Roscoff.

Etymology. The specific name is derived from the Latin nasut (=nose), alluding to the large rostrum of the new species.

Descriptionoffemale. Body ( Fig. 236A ) slightly compressed, rather stout; bodylength 2.97 mm. Prosome 2.39 mm long, 5-segmented. Dorsalcephalic shield expanded laterally, slightly produced posterodorsally. Fourth pedigerous somite forming elliptical brood pouch, about 1.5 times longer than wide and rounded posteriorly. Freeurosome ( Fig. 236B ) 5-segmented; genitalsomite 132×359 μm; 4 abdominalsomites 214×282, 214×245, 145×205, and 123×245 μm, respectively. Anal somite and caudal rami divergent. Caudal ramus ( Fig. 236C ) graduallynarrowing distally, about 4.0 times longerthan wide (218×55 μm); armedwith 6 rudimentary setae; two proximal setae located at 24 and 62% of ramus length.

Rostrum ( Fig. 236D, E ) characteristically large (more than half length of cephalic shield), highly sclerotized and about 3.6 times longerthan wide (337×93 μm), tapering peg-like in ventral view ( Fig. 236D ), gently curved and hook-like inlateral view ( Fig. 236E ), and clearly articulated at base. Antennule ( Fig. 236F ) 360 μm long, 7-segmented, but terminal segment bearing traces of 2 incompletely expressed articulations; third to terminal segments much narrower than proximal 2 segments; armatureformula 3, 16+spine, 5, 5, 3, 2+aesthetasc, 11+2 aesthetascs; all setae naked. Antenna ( Fig. 236G ) robust, 4-segmented; coxa unarmed; basis 113×73 μm, with 2 small setae; first endopodal segment 90×76 μm, with 1 small seta; compound distal endopodal segment about 2.0 timeslongerthan wide (105×54 μm); armedwith 7 setae (3 apparently located proximally on terminal claw) plus stout terminal claw 106 μm long, as long as segment, and blunt tipped.

Labrum ( Fig. 236H ) asin D. pulex . Mandible ( Fig. 236I ) with 5 teeth and 2 smallproximal setae on coxal gnathobase; setation of basis, exopod and first endopodal segment as in D. pulex , but first endopodal segment lacking row of spinules and second endopodal segment armed with 9 setae; 2 largest distalsetae on second endopodal segment equal in length. Paragnath ( Fig. 237A ) ornamented only with medial margin setules. Maxillule ( Fig. 236J ), maxilla ( Fig. 237B ), and maxilliped ( Fig. 237C ) asin D. pulex .

Leg 1 ( Fig. 237D ), leg 2 ( Fig. 237E ), leg 3, and leg 4 ( Fig. 237F ) armed as in D. pulex . Outer seta on basis of leg 1 naked, with flagellate tip. Inner coxal seta of leg 4 sparsely pinnate.

Leg 5 ( Fig. 237G, H ) similartothatof D. pulex : protopod bearing row of about 10 minute spinules at inner distal corner; free exopodal segment about 2.5 times longer than wide, armed with 2 setae distally (setal lengths variable, inner seta spiniform), ornamented with 2 or 3 rows of fine spinules on dorsomedial surface.

Descriptionofmale. Body ( Fig. 238A ) narrower than that of female, 1.45 mm long. Pedigerous somites incompletely segmented. Urosome 6-segmented. Caudal ramus about 4.9 times longer than wide (132×27 μm).

Rostrum as in female. Antennule also as in female, but aesthetascs better developed and thicker than in female. Antenna robust as in female, but terminal claw pointed distally. Labrum as in female. Mandible ( Fig. 238B ) bearing only 3 setae on first endopodal segment and 7 setaeon second. Paragnath, maxillule, maxilla, and maxilliped as in female.

Legs 1–4with 3-segmentedexopods and 2-segmented endopods ( Fig. 238 C-E); endopods shorter than exopods. Outerand distalsetae onendopods oflegs 2–4 transformed intoshort spines. Secondendopodalsegments oflegs 2 and 3 each bearing small offset spinous process, articulated at base (not included in armature formula), on anterior surface near outer distal corner.Armature formula for legs 1–4 as follows:

	Coxa Basis Exopod			Endopod
Leg 1	0-1	1-I	I-1; I-1; III, I, 4	0-1; 1, 2, 4
Legs 2 & 30-1		1-0	1-1; 1-1; 3, 1, 5	0-1; I, III, 4
Leg 4	0-1	1-0	1-1; 1-1; 2, 1, 5	0-1; I, III, 3

Leg 5 as in female; exopodal segment 2.2 times longer than wide (61×28 μm), with parallel outer and inner margins, 2 distal setae, and 3 medial rows of fine spinules. Leg 6 ( Fig. 238F ) represented by 2 equal setae and 1 small, spiniform inner process distally on genital operculum.

Remarks. Doropygus nasutus sp. nov. can be distinguished from other members of the D. pulex complex by the large, strong rostrum which is more than half the length of the dorsal cephalic shield and clearly visible without dissection. The robust antenna is also distinctive. In addition, unlike in D. pulex s. str., the brood pouch is rounded, rather than tapering posteriorly. In the present study, this species was discovered only from Pyura microcosmus and all the specimens of Doropygus collected from this species of ascidian host are D. nasutus sp. nov. This may suggest that other species of Doropygus previously recorded from P. microcosmus might be referable to D. nasutus sp. nov.

Figures

FIGURE 236. Doropygus nasutus sp. nov., female. A, habitus, right; B, urosome, ventral; C, left caudal ramus, dorsal; D, rostrum, ventral; E, rostrum, right; F, antennule; G, antenna; H, labrum; I, mandible; J, maxillule. Scale bars: A, 0.5 mm; B, 0.2 mm; C, F–J, 0.05 mm; D, E, 0.1 mm.

FIGURE 237. Doropygus nasutus sp. nov., female. A, paragnath; B, maxilla; C, maxilliped; D, leg 1; E, leg 2; F, leg 4; G, H, leg 5. Scale bars: A–C, G, H, 0.05 mm; D–F, 0.1 mm.

FIGURE 238. Doropygus nasutus sp. nov., male. A, habitus, right; B, mandible; C, leg 1; D, leg 2; E, leg 4; F, leg 6. Scale bars: A, 0.2 mm; B–E, 0.05 mm; F, 0.02 mm.