Bathynotodelphys defayeae, 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 : 9-13

publication ID	https://doi.org/ 10.11646/megataxa.4.1.1
DOI	https://doi.org/10.5281/zenodo.5661610
persistent identifier	https://treatment.plazi.org/id/03C487CB-EF59-3A39-FF4D-F949FDE9FAAC
treatment provided by	Plazi
scientific name	Bathynotodelphys defayeae
status	gen. et sp.nov.

Treatment

Bathynotodelphys defayeae gen. et sp.nov.

( Figs. 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21212 ), paratypes (intact 6 ♀♀ and 2 ♂♂, MNHN-IU-2014-21213) , and dissected paratypes (1 ♀ and 1 ♂) from Culeolus anonymus Monniot F. & Monniot C., 1976 , Vema Cruise, Argentine Basin, South Atlantic (44°33’S, 49°19’W), “Vema”, Stn V 17–81, depth 5329–5332 m, 27 May 1961. GoogleMaps

Etymology. The new species is named in honour of Dr. Danielle Defaye who made the Monniot collection of copepods associated with ascidians available to the authors for study, resulting in the present work.

Descriptionoffemale. Body ( Fig. 1A View FIGURE 1 ) laterally compressed: body length 4.40 mm in dissected specimen. Cephalosome broader than first to third pedigerous somites. Second and third pedigerous somites each with well-developed dorsal tergite. Fourth pedigerous somite forming small brood pouch, much shorter than anterior part of prosome, incorporating fused fifth pedigerous somite. Freeurosome ( Fig. 1B View FIGURE 1 ) 5-segmented: genital somite short; suture between genital and first abdominal somitesdistinct on dorsal surface but obscure ventrally. First to fourth free abdominal somites 364×345, 284×320, 218×287, and 255×313 μm, respectively. Caudal rami elongate and slightly divergent; each ramus ( Fig. 1C View FIGURE 1 ) constrictedbasallyandtaperingdistally, widestatproximal one-fifth, about 4.1 times as long as wide (502×124 μm) and armed with 6 small setae; 4 distal setae pinnate and remaining 2 setae naked; outer lateral seta positioned at 42% of ramus length.

Rostrum ( Fig. 1D View FIGURE 1 ) 255×215 μm, well-defined at base, tapering towards rounded apex. Antennule ( Fig. 1E View FIGURE 1 ) gradually narrowing distally, 9-segmented with segmental fusion pattern as in generic diagnosis; armature formula 3, 17, 6, 4+aesthetasc, 6, 4+aesthetasc, 2, 2+aesthetasc, and 7+aesthetasc; about half of setae pinnate (as figured). Antenna ( Fig. 1F View FIGURE 1 ) 5-segmented, consistingof coxa, basis and 3-segmented endopod: coxashortand unarmed: basis with 1 long pinnate seta and 1 minute naked seta at distal outer corner representing exopod; ornamented with tuft of setules proximally on inner margin: endopod 3-segmented; first segment with 1 seta on inner margin; second segment about 2.7 times as long as wide, armed with 5 setae (1 on middle of inner margin and 4 at inner distal corner); third segment about 0.6 times as long as second, 1.8 times as long as wide, armed with 6 setae (3 distal setae blunt at tip) plus small terminal claw, about 0.6 times as long as segment.

Labrum ( Fig. 1G View FIGURE 1 ) with rounded, setulose posterolateral corners and spinulose posteromedian lobe. Mandible ( Fig. 1H View FIGURE 1 ) with 6 teethand 2 smallproximal setae on cutting margin of coxal gnathobase; basis with 1 seta subdistally onmedial margin; exopod 4-segmented and armed with 1, 1, 1, and 2 setae on first to fourth segments, respectively (all 5 setae equal in length): endopod with 4 and 10 setae on first and second segments, respectively. Paragnath ( Fig. 1I View FIGURE 1 ) as simple lobe bearing setules on medial surface. Maxillule ( Fig. 1J View FIGURE 1 ) with 9 setaeon arthrite, 1 on coxal endite, 2 on epipodite, and 3 on medial margin of basis; exopod unsegmented with 4 setae distally; endopod 2-segmented with 2 or 3 setae on medial margin of first segment and 4 setae on second segment. Maxilla ( Fig. 2A View FIGURE 2 ) indistinctly 6-segmented; first segment (precoxa) with 4 and 1 setae on proximal and distal endites, respectively; secondsegment (coxa) incompletely articulated from first, armed with 2 and 3 setae on proximal and distal endites, respectively: basis with strong claw bearing spinules along concave margin, plus 2 setae: endopod slender, 3-segmentedwith 1, 1, and 4 setae on first to third segments, respectively; one of 4 setae on third segment small. Maxilliped ( Fig. 2B View FIGURE 2 ) 3-segmented and armed with 10, 1, and 4 setae on first to third segments, respectively; all setae pinnate.

Legs 1–4 biramous with 3-segmented rami ( Fig. 2 View FIGURE 2 C–E). Spines on outer margin of exopods slender and fringed with membrane bilaterally in distal half. Inner distal spine on basis of leg 1 fringed with spinules, 106 μm long, slightly longerthan first endopodal segment. Inner coxal seta of legs 2–4 stiff and spiniform. Armature formula as in generic diagnosis. Leg 5 ( Fig. 2F View FIGURE 2 ) consisting of protopod and free exopod; protopod incorporated into fifth pedigerous somite, armed with naked outer distal seta; exopodal segment elongate, about 4.3 times as long as wide (167×39 μm), ornamented with spinules along inner margin and armed distally with 1 slender spine (82 μm long) and 1 weakly pinnate seta (118 μm long).

Descriptionofmale. Body ( Fig. 3A View FIGURE 3 ) dorsoventrally depressed, tapering distally. Bodylength 2.20 mm. Prosome-urosome division indistinct. Urosome ( Fig. 3B View FIGURE 3 ) 6-segmented: fifth pedigerous somite (first urosomite) shorter than genital somite: genital somite 131×247 μm, with well-developed paired genital opercula ventrally: 4 abdominalsomites 167×196, 173×182, 135×160, and 135×145 μm, respectively. Caudal ramus about 5.6 times as long as wide (224×40 μm); outer lateral seta positioned at 40% of ramus length.

Rostrum asin female. Antennule 10-segmented; non-geniculate, segmental fusion pattern as in generic diagnosis; armatureformula 3, 17, 2, 2, 2, 4, 2, 4, 3+aesthetasc, and 10+aesthetasc; one setaon first segment pinnate, all other setae naked. Antenna as in female.

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

Labrum, maxilla, and legs 1–4 as in female. Mandible with 9 setae on second endopodal segment. Maxillule with 2 or 3 setae on first endopodal segment, as in female.

Leg 5 ( Fig. 3B View FIGURE 3 ) protopod articulated from fifth pedigerous somite; free exopodal segment about 3.2 times as long as wide (80×25 μm). Leg 6 represented by 3 setae on genital operculum, innermost seta small.

Remarks. The sexual dimorphism in antennulary segmentation of the new genus is unique. In the female segments XII to XIV are fused whereas in the male they are free; segment XVII is incorporated into a compound segment XVII-XX in the female but segment XVII is separate from XVIII-XX in the male. More distally, segments XXIV and XXV are free in the female but incorporated into a compound apical segment XXIV-XXVIII in the male. So although the male of B. defayeae gen. et sp. nov. does not retain geniculate antennules in the male, the fusion pattern of its distal segments XXIV to XXVIII probably represents a vestige of the original pattern associated with the possession of a geniculate antennule.

This species was found in deep water at a depth of 5329–5332 m in the Argentine Basin.