Gosbia pusilla, 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 : 421

Gosbia pusilla gen. et sp. nov.

( Figs. 278 , 279 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21344 ) , paratypes (2 intact ♀♀, MNHN-IU-2014-21345), anddissectedparatype (♀, figured) from Minipera papillosa Monniot C. & Monniot F., 1974 , BIOGAS$ cruise, Stn DS55, Gulf of Gascogne, off Atlantic coast of France, “Jean Charcot” (47°35’N, 09°41’W), depth 4125 m, 22 February 1974.

Additional material. 1 ♀ (dissected) from M. papillosa, BIOGAS 4 DS75, Gulf of Gascogne (47°31 Ń, 9°07.8 Ẃ), depth 2906 m, 23 February 1974; 1 ♀ (MNHN-IU-2018-1881) from M. papillosa , West Ireland, Chain 106; 1 ♀ (MNHN-IU-2018-1882) from M. papillosa , Southwest Ireland, Chain 106 Stn 326, depth 3859 m, 1972.

Etymology. The specific name is derived from the Latin pusill (=very small) and refers to the small body of the new species.

Descriptionoffemale. Body ( Fig. 278A ) small, slightlydepressed; bodylength 773 μm. Prosome 480 μm long, consisting of relatively large cephalosome and 4- segmented metasome, with thin, soft cuticle: dorsal and ventral margins of prosome nearly parallel: pedigerous somites defined only by dorsal and lateral constrictions. Freeurosome ( Fig. 278B ) 5-segmented: genitalsomite 23×98 μm;4 abdominalsomites39×83,41×71, 32×65, and 59×67 μm, respectively. Surface of posterior abdominal somites ornamented with long setules. Caudal ramus ( Fig. 278C ) about 4.2 times longerthan wide (74×17.5 μm) and gradually narrowing distally, ornamented with scattered setules: armed with 6 setae; setae longerthan maximum width of ramus; 2 proximal setae located at 24 and 36% of ramus length.

Rostrum ( Fig. 278D ) large, elongate, 71×35 μm, narrowing distally, constricted near proximal third, with small notch in apex. Antennule ( Fig. 278E ) 112 μm long, 8-segmented; armatureformula 2, 15, 5, 3, 2, 3, 5 and 7+aesthetasc; larger seta on first segment pinnate, all other setae naked.Antenna ( Fig. 278F ) 4-segmented; coxa unarmed; basis 29×17 μm, armedwith 1 large, pinnate seta (37 μm long) representing exopod at outer distal corner; first endopodal segment 35×17 μm, unarmed, slightly longer than basis; compound distal endopodal segment about 4.2 timeslongerthan wide (50×12 μm) and ornamented with row of spinules on distal part of outer margin: armedwith 6 setae (arranged as 1, 2, and 3) plus slender terminal claw, 22 μm long, less than half length of segment.

Labrum ( Fig. 278G ) with large, spinulose posteromedian lobe and convex posterior margin ornamented with setules on both sides. Mandible ( Fig. 278H ) with coxa bearing 5 teeth and 2 small setae on cutting margin of gnathobase: basis with 1 seta on medial margin; exopod with 4 setae; second and third setae longerthan first and fourth; endopod with 1 and 5 setae on first and second segments, respectively; mediodistal seta on second segment much longerthan other setae on either ramus. Maxillule ( Fig. 278I ) armedwith 5 setaeon arthrite, 1 on each coxal endite and epipodite, 2 on basis, 3 on exopod and 2 on endopod; exopod and endopod small but clearly defined. Maxilla ( Fig. 278J ) 4-segmented; syncoxa with 9 setae arranged as 3, 1, 2, and 3; basis with strong claw bearing minute spinules on concave margin plus 2 unequal setae (proximal seta needle-like); endopod 2-segmented with 1 setaon first, and 4 setaeon second segment. Maxilliped ( Fig. 278K ) unsegmented, tapering distally, with traces of 2 transverse suture lines; armed with 10 medial setae and 1 apical seta.

Legs 1–4 biramous with 3-segmented rami ( Fig. 279 A-C); coxalacking inner seta; outersetaonbasis shorter than first exopodal segment. Inner distal spine on basis of leg 1 slender, spinulose, 23 μm long. First endopodal segment of leg 1 with pointed outer distal corner; second endopodal segment with bicuspid outer distalcorner. Setaeonleg 4 shortand naked. First exopodal segment of leg 4 lacking outer element. Armature formula for legs 1–4 as in generic diagnosis.

Leg 5 ( Fig. 278B, L ) rudimentary, represented by 2 small lobes each tipped with naked seta.

Male. Unknown.

Remarks. This copepod is a deep-water species. Its host Minipera papillosa is distributed across a wide depth range (750 to 6000 m) in the Atlantic Ocean ( Monniot & Monniot, 1987).

Figures

FIGURE 278. Gosbia pusilla gen. et sp. nov., female. A, habitus, right; B, urosome, ventral; C, right caudal ramus, dorsal; D, rostrum; E, antennule; F, antenna; G, labrum; H, mandible; I, maxillule; J, maxilla; K, maxilliped; L, leg 5. Scale bars: A, 0.1 mm; B, 0.05 mm; C–L, 0.02 mm.

FIGURE 279. Gosbia pusilla gen. et sp. nov., female. A, leg 1; B, leg 2; C, leg 4. Scale bars: 0.02 mm.