Periproctia longirostris, 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 : 214-217

Periproctia longirostris sp. nov.

( Figs. 141 , 142 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21266 ) , paratype (intact ♀, MNHN-IU-2014-21267), and dissectedparatype (♀, figured) from Aplidium sp., lobster wall, Mabul Malaysia (04°14.53 Ń, 118°37.57 É), depth 17 m, 22 July 2004.

Etymology. The specific name refers to the elongate rostrum of the new species.

Descriptionoffemale. Body ( Fig. 141A, B ) rather narrow. Body length 1.31 mm in dissected largest specimen. Prosome cylindrical, 1.04 μmlong, 0.39 mm wide, ornamented with scattered setules dorsally and laterally in posterior half. Cephalosome clearly defined; 4 pedigerous somites fused and recognizable only by weak dorsal suture lines. Brood pouch extending through all pedigerous somites ( Fig. 141A, B ). Free urosome ( Fig. 141C ) 5-segmented: genital somite and first to third abdominal somites 63×157, 61×121, 65×111, and 72×100 μm, respectively. First to third abdominal somites ornamented with rows of minute spinules ventrally. Anal somite ( Fig. 141D ) short, with pair of highly sclerotized and strongly projecting ventral protuberances ornamented with spinules. Caudal rami divergent ( Fig. 141D ), ramus slightly narrowing distally, as long as wide (29×29 μm), armed with 3 unequal claws and 3 setae (2 pinnate and 1 naked); lengths of claws 44, 22, and 18 μm.

Rostrum ( Fig. 141E ) elongate, 77×44 μm, highly sclerotized, tapering towards distal beak-like process; pair of small sensillae present proximally. Antennule ( Fig. 141F ) graduallynarrowing distally, 123 μm long, and 8-segmented; armatureformula 5, 9, 8+aesthetasc, 3, 2+aesthetasc, 1, 2+aesthetasc, and 7+aesthetasc; setae crowded, proximal 2 setae markedly enlarged; most setae naked but several larger ones pinnate. Antenna ( Fig. 141G ) 4-segmented; basis and first endopodal segment each 1.3 times longer than wide and armed as usual for genus; compound distal endopodal segment 3.2 times longer than wide (64×20 μm), ornamented with scattered spinules; armed with 8 setae (including 1 pinnate and 4 bluntly tipped distal setae) plus slender terminal claw, about half as long as segment.

Labrum ( Fig. 141H ) simple, smooth, with slightly convex posterior margin. Mandible ( Fig. 141I ) with 5 teeth, 1 needle-like spinule between distal second and third teeth, and 1 proximal seta on coxal gnathobase; basiswith 1 medial seta; exopod 2-segmented, with 3 and 2 setae on first and second segments, respectively, outer seta on second segment about half as long as adjacent seta; endopod with 2 and 6 setae on first and second segments, respectively. Maxillule ( Fig. 142A ) with 8 setae on arthrite, 1 on coxal endite, 2 on epipodite, 3 on medial margin of basis, 3 on exopod and 4 on endopod. Maxilla ( Fig. 142B ) 5-segmented; syncoxawith 3, 1, 2, and 3 setae on first to fourth endites, respectively; basis with 2 setae, distal seta short and naked; endopod with 1, 1, and 2 setae on first to third segments, respectively. Maxilliped ( Fig. 142C ) lobate, armed with 8 medial and 2 apical setae.

Legs 1–4 ( Fig. 142 D-G) each with 3-segmented exopod and 2-segmented endopod. Inner coxal seta absent in legs 1–4. Outer seta on basis large, more than twice as long as exopod in leg 1, but small in legs 2–4. Innerdistalspineonbasisofleg 1 smooth, aslongas first endopodal segment. Third exopodal segment of legs 2–4 terminating in acutely pointed process. Leg 3 lacking inner seta on second exopodal segment. Leg 4 lacking inner seta on proximal 2 exopodal and first endopodal segments. Armature formula for legs 1–4 as follows:

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

Leg 5 ( Fig. 141C ) represented by small lobe on posteroventral margin of somite, armed with 2 pinnate setae distally.

Male. Unknown.

Remarks. Periproctia longirostris sp. nov. is characterised by multiple setal losses on legs 3 and 4. The setae lost are as follows: the inner setae on (1) the second exopodal segment of leg 3; (2) the first and (3) second exopodal segments of leg 4; (4) the first endopodal segment of leg 4; and (5) the inner seta derived from the ancestral second endopodal segment of leg 4 (now incorporated into a compound distal segment). Some reduction in leg setation was also recorded in the three speciesof Periproctia namedby Stock (1967), P. biuncata , P. falsiarcuata , and P. triuncata . The setal losses (3), (4), and (5), as listed above, are shared with all three species, but setal loss (1) is shared only with P. falsiarcuata and P. triuncata , and setalloss (2) isshared onlywith P. biuncata . These different setation patterns on the second exopodal segment of leg 3 and on the first exopodal segment of leg 4 serve to differentiate P. longirostris sp. nov. from these three congeners. There are additional significant differences including: P. longirostris sp. nov. has 3 spines and 3 setae on the caudal ramus (vs. 2 spines and 4 setae in P. biuncata ), 6 setae on the second endopodal segment of the mandible (vs. 5 setae in all the three species described by Stock, 1967), 10 setaeon the maxilliped (less than 10 setae in P. biuncata and P. triuncata ), and an inner seta on the second exopodal segment of leg 1 (this seta absent in P. biuncata and P. falsiarcuata ).

Figures

FIGURE 141. Periproctia longirostris sp. nov., female. A, habitus, dorsal; B, habitus, left; C, urosome, ventral; D, anal somite and caudal ramus, right; E, rostrum; F, antennule; G, antenna; H, labrum; I, mandible. Scale bars: A, B, 0.2 mm; C, 0.1 mm; D-H, 0.02 mm.

FIGURE 142. Periproctia longirostris sp. nov., female. A, maxillule; B, maxilla; C, maxilliped; D, leg 1; E, leg 2; F, leg 3; G, leg 4. Scale bars: 0.02 mm.