Doroixysbifurcata, 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 : 491-494

Doroixysbifurcata sp. nov.

( Figs. 326 , 327 )

Typematerial. Holotype (intact ♀, MNHN-IU-2014- 21376 ) , paratypes (2 intact ♀♀, MNHN-IU-2014-21377). and dissected paratypes (2 ♀♀, figured) from Didemnum psammatodes (Sluiter, 1895) , Pt. Lambi, Guadeloupe, depth 1-3 m, Monniot coll., 16 December 1980.

Etymology. The specific name refers to the distally bifurcate cephalic horn-like processes.

Descriptionoffemale. Body( Fig.326A ) small, stout, curved ventrally; bodylength 700 μm. Prosome 546 μm long; dorsal cephalic shield bearing paired posterolateral horn-like processes ( Fig. 326B ); these processes highly sclerotized and bifurcate at tip. Metasome unsegmented, with posterior 60% more expanded than anterior 40% and with rounded protuberance on posterior margin. Eggs visible within entire metasome. Free urosome 5- segmented, small, recurved ventrally. Caudalramus ( Fig. 326C ) about 2.2 times longer than wide (35×16 μm), tapering, slightly longer than anal somite, and ornamented with setules: armed with 6 setae, all setae naked and shorter than ramus but longer than width of ramus at base; 2 proximal setae positioned at 37 and 47% of ramus length.

Rostrum ( Fig. 326D ) aslongas wide, gradually narrowing distally towards rounded apex; ornamented with several setules. Antennule ( Fig. 326E ) 90 μm long, 6-segmented but fifth segment subdivided by incomplete suture line on posterior side; armature formula 2, 17, 6, 4, 4+aesthetasc, and 9+aesthetasc; all setae naked. Antenna ( Fig. 326F ) 4-segmented; proximal 3 segments (coxa, basis, and firstendopodal segment) unarmed; narrower second endopodal segment 29×10 μm, slightly longer than first; armedwith 6 setae (arranged as 1, 2, and 3) plus small terminal claw, less than half length of segment.

Labrum ( Fig. 326G ) simple, unornamented, with soft, thin-walled, posterior part. Mandible ( Fig. 326H ) bearing 5 acuteteeth and 1 small setaon coxal gnathobase: basis unarmed; exopod with 4 subequal medial and distal setae plus short outer seta about 0.65 times length of other 4: endopod 2-segmented, armed with 1 broad seta on first segment and 4 unequal setae on second segment; relative lengths of latter setae 5:8:11:9 from medial to outer. Maxillule ( Fig. 326I ) with 9 setaeon arthrite, 1 on epipodite, and 4 on exopod; basis and endopod fused, without any trace of articulation, bearing total of 4 setae. Maxilla ( Fig. 326J ) 4-segmented, armedwith 4, 2, and 2 setae on first to third endites of syncoxa, slender claw plus 1 seta on basis, and 1 and 3 setae on first and second endopodal segments, respectively. Maxilliped ( Fig. 326K ) small, unsegmented, armed with 5 setae and ornamented with spinules on outer surface.

Legs 1–3 ( Fig. 327 A-C) with 3-segmented rami. Leg 4 ( Fig. 327D ) with 3-segmented exopod and 2-segmented endopod. Inner coxal seta absent in legs 1–4. Outer seta on basis pinnate in leg 1, but naked in legs 2–4. Inner distal spine on basis of leg 1 small, 9 μm long. Outer spine on first exopodal segment of leg 1 enlarged, extending beyond distal tip of outer spine on second exopodal segment. All setae on legs 2–4 naked and most bluntly tipped. Armature formula for legs 1–4 as follows:

	Coxa Basis Exopod			Endopod
Leg 1	0-0	1-I	I-1; I-1; I+1, 2, 30-1; 0-1; 1, 2, 3
Legs 2 & 30-0		1-0	1-0; 1-0; 3, 1, 5	0-0; 0-0; 0, 2, 3
Leg 4	0-0	1-0	1-0; 1-0; 3, 1, 4	0-0; 0, 2, 2

Leg 5 ( Fig. 327E ) represented by 2 pointed processes and 2 naked setae; larger outer process bearing protopodal seta subdistally on outer margin, other seta positioned laterally at base of exopodal process.

Male. Unknown.

Remarks. Theendopod of leg 4 of Doroixysbifurcata sp. nov. is 2-segmented and armed with 4 setae on the compound distal segment. This pattern of segmentation and setation of the leg 4 endopod is shared only with D. minuta . The maxilliped armature of 5 setae is known only in D. bifurcata sp. nov., D. minuta , and D. manadoensis sp. nov., although the number of setae on this limb may be either 5 or 6 in the latter species. However, D. minuta . differs from D. bifurcata sp. nov. because the former has a 3-segmented antenna and is armed with only 3 setae on the second endopodal segment of the mandible, as described and illustrated by Stock (1970), whereas in D. bifurcata sp. nov. the antenna is 4-segmented and the mandible carries 4 setae on the secondendopodal segment. It can be distinguished from D. manadoensis sp. nov. which has 6 setae on the second endopodal segment of the mandible (rather than 4) and an inner seta on the first exopodal segment of leg 2 which is missing in D. bifurcata sp. nov.

In Doroixys , leg 5 consists of a protopod which is incorporated into the somite and a tapering, sclerotized inner process representing the transformed exopod. The rudimentary protopod (outer lobe) is either fully incorporated and appears as a bluntly rounded angle (which may or may not carry the outer protopodal seta), or projects as a digitiform process tipped with a seta. Leg 5 of D. bifurcata sp. nov. deviates from this general form in having an outer protopodal lobe which forms a pointed process similar to the exopodal process, and bears a seta on its outer margin. The characteristic form of leg 5 is an additional distinguishing feature of D. bifurcata sp. nov.

Figures

FIGURE 326. Doroixys bifurcata sp. nov. A, habitus, right; B, cephalic horn; C, left caudal ramus, dorsal; D, rostrum; E, antennule; F, antenna; G, labrum; H, mandible; I, maxillule; J, maxilla; K, maxilliped. Scale bars: A, 0.1 mm; B–H, 0.02 mm; I–K, 0.01 mm.

FIGURE 327. Doroixys bifurcata sp. nov. A, leg 1; B, leg 2; C, leg 3; D, leg 4; E, leg 5. Scale bars: 0.02 mm.