Ooishillgia, 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 : 188-190

Ooishillgia gen. nov.

Diagnosis. Body of female elongate and bilaterally compressed. Prosome consisting of cephalosome, 3 pedigerous somites plus fourth and fused fifth pedigerous somites. Brood pouch extending through third and fourth pedigerous somites, rounded posteriorly. Free urosome 5- segmented in female, 6-segmented in male. Anal somite with weak posteroventral protuberance. Caudal ramus small, located dorsally on anal somite, armed with 6 setae. Rostrum well-developed. Antennule 8-segmented. Antenna 4-segmented; basis with 1 large exopodal seta. Mandible with 4 setaeon exopod; endopod with 4 and 9 setae on first and second segments, respectively. Maxillule with 3 setae each on basis and exopod, and 4 setae on endopod. Maxilla with claw plus 2 setae on basis and 4 setae on third endopodal segment. Maxilliped unsegmented with 8 medial and 2 apical setae in female, and 6 medial and 2 apical setae in male. Leg 1 with 3- segemented rami; third exopodal segment with setaas first outer element. Legs 2–4 each with 3-segmented exopod and 2-segmented endopod. Inner coxa seta lacking in legs 1–4. Leg 1 basis with inner distal spine; outer seta not enlarged. Leg 5 small with free exopodal segment bearing single apical seta.

Type and only species. Goniodelphys tokiokai Ooishi & Illg, 1973 , by original designation.

Etymology. The new genus named for the late Shigeko Ooishi and Paul L. Illg, who originally described the type species and have contributed enormously to our understanding of the Notodelphyidae . Gender feminine.

Remarks. The characters of type species suggest that the new genus is closely related to Notopterophoroides , with which it shares numerous derived character states. In particular, the possession of a seta as the proximal outer element on the third exopodal segment of leg 1 is an important synapomorphic trait. However, Ooishillgia gen. nov. differs from Notopterophoroides and from other similar genera in having 4 setae on the mandibular exopod, and 6 setae but no claws on the caudal ramus. We here remove G. tokiokai from Goniodelphys and establish Ooishillgia gen. nov. to accommodate it.

Ooishillgia tokiokai (Ooishi and Illg, 1973) comb. nov.

( Figs. 123 , 124 )

Syn.: Goniodelphys tokiokai Ooishi & Illg, 1973: 217 , figs. 1-4.

Material examined. 1 ♀, 1 ♂ (both dissected) from Pterygascidia longa (Van Name, 1918) , West of Panay Island, the Philippines (11°27 Ń, 121°43 É), MUSORSTOM Stn 131, depth 120 m, 05 June 1985.

Supplementary description of female. Female body ( Fig. 123A ) elongate, 2.23 mmlong measured from frontal margin of cephalosome to posterior end of brood pouch. Fourthpedigerous somiteextending beyond caudal rami; fifth pedigerous somite incorporated into brood pouch. Freeurosome ( Fig. 123B ) stout, 5-segmented: anal somite with weak posteroventral protuberance. Caudal ramus 65×35 μm, located dorsally on anal somite; armed with 6 setae.

Rostrum ( Fig. 123C ) longerthanwide (162×112 μm), triangular. Antennule ( Fig. 123D ) 8-segmented; fifth segment with trace of subdivision; armature formula 3, 15 (or 7, 11), 8+aesthetasc, 3, 3+aesthetasc, 2, 2+aesthetasc, and 6+aesthetasc; aesthetascs thin and hard to distinguish from setae.Antenna ( Fig. 123E ) 4-segmented; basisbearing large, pinnate seta plus vestigial seta, representing exopod.

Labrum simple, unornamented, with straight posterior margin lacking posteromedian lobe. Mandible ( Fig. 123F ) with 6 acute teeth and several needle-like spinules on cutting margin and 2 small setae on proximal margin of coxal gnathobase; exopod with 4 large setae; endopod with 4 and 9 setaeon first and second segments, respectively. Maxillule bearing 9 setae on arthrite, 1 each on coxal endite and epipodite, 3 on basis and on exopod, and 4 on endopod. Maxilla 5-segmented with 9, 2+claw, 1, 1, and 4 as armature formula. Maxilliped unsegmented, with 8 medial and 2 apical setae.

Leg 1 ( Fig. 123G ) with 3-segmented rami. Third exopodal segment armed with 1 seta (proximalmost element) and 2 slender spines on outer margin, 1 slender spine distally, and 3 setae on inner margin; first outer spine (second element) much shorter than 2 distal spines. Legs 2–4 each with 3-segmented exopod and 2-segmented endopod, lacking inner setaon second exopodal segment ( Fig. 124A ). Armature formula for legs 1–4 as follows:

Leg 4 0-0 1-0 1-1; 1-0; 2, 1, 3 0-1; 1, 2, 3

Leg 5 small; free exopodal segment ( Fig. 123B ) slender, 37×11 μm, with large naked apical seta.

Descriptionofmale. Body ( Fig. 124C ) strongly curved ventrally. Bodylength 1.30 mm. Urosome 6- segmentedwith clearly defined fifth pedigerous somite. Caudal ramus as in female.

Rostrum ( Fig. 124E ) minutely bifurcate at apex. Antennule, antenna, labrum, mandible, maxillule, maxilla asin female. Maxilliped ( Fig. 124F ) with 6 (3+3) medial and 2 apical setae.

	Coxa	Basis	Exopod	Endopod
Leg 1	0-0	1-I	I-1; I-1; 1, III, 3	0-0; 0-1; 1, 2, 2
Leg 2	0-0	1-0	I-1; I-0; 3, 1, 4	0-1; 1, 2, 6
Leg 3	0-0	1-0	I-1; I-0; 2, 1, 4	0-1; 1, 2, 5

Legs 1–4 as in female. Leg 5 ( Fig. 124D ) also similar to that of female. Leg 6 ( Fig. 124D ) represented by 2 naked setae on genital operculum.

Remarks. The male of this species is reported here for the first time. The single female studied exhibits some differences from the original description. The setation of the antennule and the relative lengths of the outer spines on the third exopodal segment of leg 1 differ between the type specimens and our specimen. Ooishi & Illg (1973) described a stout exopodalsegment on leg 5 and illustrated the presence of an inner seta on the second exopodal segment of leg 4. These discrepancies may be considered to be artefacts, or may represent infraspecific variation, since both the type and our specimens were derived from the same host species collected in the same geographical region.

Figures

FIGURE 123. Ooishillgia tokiokai (Ooishi & Illg, 1973) n. comb., female. A, habitus, left; B, urosome, ventral; C, rostrum; D, antennule; E, antenna; F, mandible; G, leg 1. Scale bars: A, 0.5 mm; B, C, 0.1 mm; D-G, 0.05 mm.

FIGURE 124. Ooishillgia tokiokai (Ooishi & Illg, 1973) n. comb., female: A, leg 4; B, exopod of leg 5. Male: C, habitus, left; D, first two urosomal somites, ventral; E, rostrum; F, maxilliped. Scale bars: A, D, E, 0.05 mm; B, F, 0.02 mm; C, 0.1 mm.