Bysonebidens, 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 : 444-446

Bysonebidens sp. nov.

( Figs. 294 , 295 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21356) , paratype (intact ♀, MNHN-IU-2014-21357), and dissectedparatype (♀, figured) from Chorizocarpaguttata Michaelsen, 1904 , Canal Woodin, New Caledonia, depth 18m, Monniot coll., 11 March 1987.

Etymology. The specific name is the combination of Latin words bi (=double) and dens (=a tooth), referring to the pair of ventrodistal denticles on the surface of the labrum.

Description of female. Body ( Fig. 294A ) with stout prosome and elongate urosome; body length 1.48 mm. Prosome 0.93 mm long: cephalosome clearly defined from inflated metasome; first and second pedigerous somites defined, but third and fourth pedigerous somites completely fused forming brood pouch. Free urosome ( Fig. 294B ) slender, 5-segmented: genitalsomite 68×294 μm, much wider than long; 4 abdominal somites gradually narrowing, 84×193, 84×123, 82×110, and 68×105 μm, respectively. Caudalramus ( Fig. 294C ) gradually narrowing distally, 3.6 times longer than wide (130×36 μm): armed with 6 setae; proximal and dorsal setae located at 32 and 63% of ramus length, respectively; all setae shorter than width of ramus at base.

Rostrum ( Fig. 294D ) 64×89 μm, tapering, with rounded and sclerotized distal margin. Antennule ( Fig. 294E ) 170 μmlong, 6-segmented; armatureformula 3, 17, 7+aesthetasc, 3, 2+aesthetasc, and 11+2 aesthetascs; setae naked and relatively short; setae on first segment not enlarged. Antenna ( Fig. 294F ) 4-segmented; coxa, basis, and first endopodal segment unarmed; compound distal endopodal segment 3.1 times longer than wide: armed with 5 setae (2 located at base of terminal claw) plus terminal claw, 33 μm long.

Labrum ( Fig. 294G ) bearing smooth ventral lobe, pair of ventrodistal denticles near midline, patches of minute setules ventrodistally, and with concave posterior margin. Mandible ( Fig.294H )withbroadcoxalgnathobasebearing 5 teeth and 1 distal, spinule-like subsidiary denticle: basis with 1 setaonmedial margin; exopod armedwith 4 setae; setae becoming gradually shorter from proximal to distal; endopod armed with 2 and 5 setae on first and second segments, respectively; middle setaon second endopodal segment markedly longer than other endopodal setae. second exopodal segment with short trace of articulation on outer side. Legs 2–4 with rudimentary inner coxal seta ( Fig. 295C, D ); outer seta on basis also small; all setae on endopod naked; outer setae on exopod small and bluntly tipped. Second endopodal segment of leg 4 elongated, about 4 times longer than first. Armature formula for legs 1–4 as in B. brevicaudatus sp. nov., except formula IV, I, 4 for second exopodal segment of leg 1. Leg 5 ( Fig. 295E ) small, consisting of 1 seta located on slight ventrolateral lobe and lobate tapering exopod, notarticulated at base, armed distally with 2 unequal setae.

Male. Unknown.

Remarks. Bysone bidens sp. nov. is more similar to B. brevicaudatus sp. nov. than to B. operculatus ; both share several character states including the 3-segmented endopod of the maxilla (2-segmented in B. operculatus ), the presence of a claw on the maxillary basis (only setae present in B. operculatus ), the inner coxalseta is present in allswimming legs (present onlyin leg 1 in B. operculatus ), and the second endopodal segment of leg 1 is armed with 7 setae (compared with 6 setaein B. operculatus ).

The salient differences between B. brevicaudatus sp. nov. and B. bidens sp. nov. are 7 setae on the maxilliped in the latter (vs. 9 setae in B. brevicaudatus sp. nov.), 4 setae on the second exopodal segment of leg 1 (vs. 3 setae in B. brevicaudatus sp. nov.), and a protopodal seta in leg 5 (vs. this seta absent in B. brevicaudatus sp. nov.).

Figures

FIGURE 294. Bysone bidens 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, maxilla. Scale bars: A, 0.2 mm; B, 0.1 mm; C, 0.05 mm; D–J, 0.02 mm.

FIGURE 295. Bysone bidens sp. nov., female. A, maxilliped; B, leg 1; C, leg 2; D, leg 4; E, leg 5. Scale bars: A, E, 0.02 mm; B–D, 0.05 mm.