Notopterophoroides deplanatum, 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 : 185-188

Notopterophoroides deplanatum sp. nov.

( Figs. 121 , 122 )

Type material. Holotype ♀ (dissected and mounted on a slide, MNHN-IU-2014-21256 ) from Ascidia ornata Monniot F. & Monniot C., 2001 (MNHN-IT-2008-1160 = MNHN P5/ASC.A/299), CRRFCRCHO 148, offshore sand cay, Camiguin Island, the Philippines (09°15.38 Ń, 124°39.12 É), depth 18 m, 19 April 1997.

Etymology. The specific name is derived from the Latin deplanat, meaning “flattened”, and refers to the extremely flattened body of the new species.

Descriptionoffemale. Body ( Fig. 121A ) extremely flattened dorsoventrally, 1.27 mm long. Prosome 110 μm long, occupying 87% of total body length, consistingof cephalothorax, 280×420 μm with broad, weak anterior protrusion, secondandthirdpedigerous somites,165×451, 260×455, respectively, and fourth pedigerous somite, 405×435 μm, incorporating fused fifth pedigerous somite. Freeurosome ( Fig. 121B ) small, 5-segmented, gradually narrowing posteriorly: genitalsomite 145 μm wide, not articulated from metasome, ornamented with row of minute spinules on both sides of posteroventral margin. Four free abdominal somites 118×127, 100×116, 56×95, and 47×71 μm, respectively. Anal somite ( Fig. 121C, D ) with paired sclerotized posteroventral protuberances ornamented with patches of spinules. Caudal ramus about 1.8 times longerthan wide (51×29 μm) positioneddorsally on anal somite, tapering and with spinulose ornamentation distally, possibly armed with 3 claws and 3 setae; 2 claws positioned dorsally at 60% length of ramus, other claw missing but scar visible.

Rostrum as weak anterior protrusion on frontal margin of dorsal cephalothoracic shield. Antennule ( Fig. 121E ) small, 150 μm long and 7-segmented; armature formula 7, 9+spine, 10, 4, 2+aesthetasc, 2+aesthetasc, and 7+aesthetasc; first segment with patch of minute spinules on proximal anterior surface; setae thin and aesthetascs hard to distinguish from setae. Antenna ( Fig. 121F ) 4- segmented; coxa short and unarmed; basis about 1.7 times longerthan wide, armed with large pinnate exopodal seta at outer distal corner; first endopodal segment about 1.3 timeslongerthan wide and 0.8 timeslongerthan basis, with 1 small seta subdistal on inner surface; compound distal endopodal segment about 4.3 times longer than wide (73×17 μm), ornamented with minute spinules on inner margin, and spinules plus setules subdistally on outer margin; armedwith 9 setae (all attenuated) plus slender terminal claw, less than half length of segment.

Labrum weak, destroyed. Mandible ( Fig. 121G ) with narrowcoxalgnathobasebearing 5teeth, 1 spinulebetween distal second and third teeth, and 1 small seta on proximal margin; basis with setules on outer and medial margins, armedwith 1 small mediodistal seta; exopod 2-segmented, armed with 3 and 2 setae on first and second segments, respectively; outer distal seta on second segment half as long as other exopodal setae: endopod with 4 and 9 setae on first and second segments, respectively. Maxillule ( Fig. 121H ) and maxilla ( Fig. 122A ) armed as in N. tripartitum sp. nov. Maxilliped ( Fig. 121I ) unsegmented, armedwith 6 (3+3) setae medially plus apical seta; with patches of fine spinules near base of medial setae; one proximal seta on medial margin much smaller than others.

Legs 1–4 ( Fig. 122 B-E) with 3-segmented exopods and 2-segmented endopods. Protopod broad in leg 1, but narrow inlegs 2–4. Rami of leg 1 widely separated. Coxa of legs 1–4 unarmed. Outer seta on basis of leg 1 not enlarged, similar inlength tothose of legs 2–4. Inner distal spineonbasisofleg 1 serrate, 22 μmlong, slightlylonger than first endopodal segment. Rami of legs 2–4 slender. Third exopodal segment of leg 1 bearing seta as first outer element. Endopods of legs 2–4 much shorter than exopod, not extending beyond distal border of second exopodal segment. Armature formula for legs 1–4 as follows:

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

Leg 5 ( Fig. 122F ) small, consistingof short protopod and free exopod; protopod with small, naked outer distal seta, and row of spinules along ventrodistal border; exopodal segment about 3.4 times longer than wide (27×8 μm), slightly constricted proximally, ornamented with 2 and 1 rows of spinules on inner and outer margins, respectively and 1 bifurcate sensilla subdistally; probably armed with single apical seta (seta missing, but scar visible).

Male. Unknown.

Remarks. This species is similar to N. tripartitum sp. nov. in having the unsegmented maxilliped and 2- segmented endopods in legs 2–4. Both species were collected from the same host at a same time. However N. deplanatum sp. nov. differs from N. tripartitum sp. nov. in having a 4-segmented, strongly depressed prosome (vs. 3-segmented and cylindrical in N. tripartitum sp. nov.), 7 setae on the maxilliped (vs. 9 setae in N. tripartitum sp. nov.), an inner seta on the first exopodal segment of leg 2 (vs. this seta missing in N. tripartitum sp. nov.), 8 setae on the third exopodal segment of leg 2, and 7 setae on the third exopodal segment of leg 4 (vs. 7 and 6 setae, respectively in N. tripartitum sp. nov.). These major differences cannot be considered as intraspecific variation and justify the establishment of the separate species.

Figures

FIGURE 121. Notopterophoroides deplanatum sp. nov., female. A, habitus, dorsal; B, urosome, ventral; C, anal somite and caudal rami, dorsal; D, anal somite and caudal rami, ventral; E, antennule; F, antenna; G, mandible; H, maxillule; I, maxilliped. Scale bars: A, 0.2 mm; B, 0.05 mm; C-I, 0.02 mm.

FIGURE 122. Notopterophoroides deplanatum sp. nov., female. A, maxilla; B, leg 1; C, leg 2; D, leg 3; E, leg 4; F, leg 5. Scale bars: A-E, 0.02 mm; F, 0.1 mm.